Sample records for light interception self-shading
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Seedlings of temperate rainforest conifer and angiosperm trees differ in leaf area display.
Lusk, Christopher H; Pérez-Millaqueo, Manuel M; Saldaña, Alfredo; Burns, Bruce R; Laughlin, Daniel C; Falster, Daniel S
2012-07-01
The contemporary relegation of conifers mainly to cold or infertile sites has been ascribed to low competitive ability, as a result of the hydraulic inefficiency of tracheids and their seedlings' initial dependence on small foliage areas. Here it is hypothesized that, in temperate rainforests, the larger leaves of angiosperms also reduce self-shading and thus enable display of larger effective foliage areas than the numerous small leaves of conifers. This hypothesis was tested using 3-D modelling of plant architecture and structural equation modelling to compare self-shading and light interception potential of seedlings of six conifers and 12 angiosperm trees from temperate rainforests. The ratio of displayed leaf area to plant mass (LAR(d)) was used to indicate plant light interception potential: LAR(d) is the product of specific leaf area, leaf mass fraction, self-shading and leaf angle. Angiosperm seedlings self-shaded less than conifers, mainly because of differences in leaf number (more than leaf size), and on average their LAR(d) was about twice that of conifers. Although specific leaf area was the most pervasive influence on LAR(d), differences in self-shading also significantly influenced LAR(d) of large seedlings. The ability to deploy foliage in relatively few, large leaves is advantageous in minimizing self-shading and enhancing seedling light interception potential per unit of plant biomass. This study adds significantly to evidence that vegetative traits may be at least as important as reproductive innovations in explaining the success of angiosperms in productive environments where vegetation is structured by light competition.
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Seedlings of temperate rainforest conifer and angiosperm trees differ in leaf area display
Lusk, Christopher H.; Pérez-Millaqueo, Manuel M.; Saldaña, Alfredo; Burns, Bruce R.; Laughlin, Daniel C.; Falster, Daniel S.
2012-01-01
Background and Aims The contemporary relegation of conifers mainly to cold or infertile sites has been ascribed to low competitive ability, as a result of the hydraulic inefficiency of tracheids and their seedlings' initial dependence on small foliage areas. Here it is hypothesized that, in temperate rainforests, the larger leaves of angiosperms also reduce self-shading and thus enable display of larger effective foliage areas than the numerous small leaves of conifers. Methods This hypothesis was tested using 3-D modelling of plant architecture and structural equation modelling to compare self-shading and light interception potential of seedlings of six conifers and 12 angiosperm trees from temperate rainforests. The ratio of displayed leaf area to plant mass (LARd) was used to indicate plant light interception potential: LARd is the product of specific leaf area, leaf mass fraction, self-shading and leaf angle. Results Angiosperm seedlings self-shaded less than conifers, mainly because of differences in leaf number (more than leaf size), and on average their LARd was about twice that of conifers. Although specific leaf area was the most pervasive influence on LARd, differences in self-shading also significantly influenced LARd of large seedlings. Conclusions The ability to deploy foliage in relatively few, large leaves is advantageous in minimizing self-shading and enhancing seedling light interception potential per unit of plant biomass. This study adds significantly to evidence that vegetative traits may be at least as important as reproductive innovations in explaining the success of angiosperms in productive environments where vegetation is structured by light competition. PMID:22585929
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Valladares, Fernando; Gianoli, Ernesto; Saldaña, Alfredo
2011-08-01
While the climbing habit allows vines to reach well-lit canopy areas with a minimum investment in support biomass, many of them have to survive under the dim understorey light during certain stages of their life cycle. But, if the growth/survival trade-off widely reported for trees hold for climbing plants, they cannot maximize both light-interception efficiency and shade avoidance (i.e. escaping from the understorey). The seven most important woody climbers occurring in a Chilean temperate evergreen rainforest were studied with the hypothesis that light-capture efficiency of climbers would be positively associated with their abundance in the understorey. Species abundance in the understorey was quantified from their relative frequency and density in field plots, the light environment was quantified by hemispherical photography, the photosynthetic response to light was measured with portable gas-exchange analyser, and the whole shoot light-interception efficiency and carbon gain was estimated with the 3-D computer model Y-plant. Species differed in specific leaf area, leaf mass fraction, above ground leaf area ratio, light-interception efficiency and potential carbon gain. Abundance of species in the understorey was related to whole shoot features but not to leaf level features such as specific leaf area. Potential carbon gain was inversely related to light-interception efficiency. Mutual shading among leaves within a shoot was very low (<20 %). The abundance of climbing plants in this southern rainforest understorey was directly related to their capacity to intercept light efficiently but not to their potential carbon gain. The most abundant climbers in this ecosystem match well with a shade-tolerance syndrome in contrast to the pioneer-like nature of climbers observed in tropical studies. The climbers studied seem to sacrifice high-light searching for coping with the dim understorey light.
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Meng, Fengqun; Cao, Rui; Yang, Dongmei; Niklas, Karl J; Sun, Shucun
2014-01-01
Species in high-rainfall regions have two major alternative approaches to quickly drain off water, i.e., increasing leaf inclination angles relative to the horizontal plane, or developing long leaf drip tips. We hypothesized that shade-adapted species will have more pronounced leaf drip tips but not greater inclination angles (which can reduce the ability to intercept light) compared to sun-adapted species and that length of leaf drip tips will be negatively correlated with photosynthetic capacity [characterized by light-saturated net photosynthetic rates (Amax), associated light compensation points (LCP), and light saturation points (LSP)]. We tested this hypothesis by measuring morphological and physiological traits that are associated with light-interception and water shedding for seven shade-adapted shrub species, ten sun-adapted understory shrub species, and 15 sun-adapted tree species in a subtropical Chinese rainforest, where mean annual precipitation is around 1,600 mm. Shade-adapted understory species had lower LMA, Amax, LSP, and LCP compared to understory or canopy sun-adapted species; their leaf and twig inclination angles were significantly smaller and leaf drip tips were significantly longer than those in sun-adapted species. This suggests that shade-adapted understory species tend to develop pronounced leaf drip tips but not large leaf inclination angles to shed water. The length of leaf drip tips was negatively correlated with leaf inclination angles and photosynthetic capacity. These relationships were consistent between ordinary regression and phylogenetic generalized least squares analyses. Our study illustrates the trade-offs between light interception and leaf water shedding and indicates that length of leaf drip tips can be used as an indicator of adaptation to shady conditions and overall photosynthetic performance of shrub species in subtropical rainforests.
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Valladares, Fernando; Gianoli, Ernesto; Saldaña, Alfredo
2011-01-01
Background and Aims While the climbing habit allows vines to reach well-lit canopy areas with a minimum investment in support biomass, many of them have to survive under the dim understorey light during certain stages of their life cycle. But, if the growth/survival trade-off widely reported for trees hold for climbing plants, they cannot maximize both light-interception efficiency and shade avoidance (i.e. escaping from the understorey). The seven most important woody climbers occurring in a Chilean temperate evergreen rainforest were studied with the hypothesis that light-capture efficiency of climbers would be positively associated with their abundance in the understorey. Methods Species abundance in the understorey was quantified from their relative frequency and density in field plots, the light environment was quantified by hemispherical photography, the photosynthetic response to light was measured with portable gas-exchange analyser, and the whole shoot light-interception efficiency and carbon gain was estimated with the 3-D computer model Y-plant. Key Results Species differed in specific leaf area, leaf mass fraction, above ground leaf area ratio, light-interception efficiency and potential carbon gain. Abundance of species in the understorey was related to whole shoot features but not to leaf level features such as specific leaf area. Potential carbon gain was inversely related to light-interception efficiency. Mutual shading among leaves within a shoot was very low (<20 %). Conclusions The abundance of climbing plants in this southern rainforest understorey was directly related to their capacity to intercept light efficiently but not to their potential carbon gain. The most abundant climbers in this ecosystem match well with a shade-tolerance syndrome in contrast to the pioneer-like nature of climbers observed in tropical studies. The climbers studied seem to sacrifice high-light searching for coping with the dim understorey light. PMID:21685433
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Ishii, Hiroaki; Hamada, Yoko; Utsugi, Hajime
2012-10-01
We investigated the effects of sun- and shade-shoot architecture on the photosynthetic rates of two Picea species by applying light from various angles in the laboratory. Compared with sun shoots, shade shoots were characterized by lower mass allocation per light-intercepting area, less leaf mass per shoot mass, less mutual shading among leaves and more efficient allocation of chlorophyll to photosynthesis. The shoot silhouette to total leaf area ratio (STAR(ϕ)) decreased with increasing shoot inclination angle (ϕ, the shoot axis angle relative to the projection plane) and was consistently higher for the shade shoots. Morphological and physiological characteristics of the shade shoots resulted in maximum rates of net photosynthesis at ϕ = 0° (P(max,0)) similar to that of the sun shoots when expressed on a leaf mass, total leaf area and chlorophyll basis. When the angle of incoming light was varied, P(max,ϕ) per total leaf area (P(max,ϕ )/A(T)) of the shade shoots increased linearly with increasing STAR(ϕ), while P(max,ϕ) per shoot silhouette area did not change. In contrast, the response of the sun shoots was non-linear, and an optimum angle of incoming light was determined. Our results suggest that shade-shoot morphology is adaptive for utilizing diffuse light incoming from various angles, while sun-shoot morphology is adaptive for avoiding the negative effects of strong direct radiation and for enhancing light diffusion into the canopy. We propose that the angle of incoming light should be taken into account when estimating photosynthetic rates of sun shoots of conifer trees in the field.
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Leaf traits show different relationships with shade tolerance in moist versus dry tropical forests.
Poorter, Lourens
2009-03-01
Shade tolerance is the central paradigm for understanding forest succession and dynamics, but there is considerable debate as to what the salient features of shade tolerance are, whether adult leaves show similar shade adaptations to seedling leaves, and whether the same leaf adaptations are found in forests under different climatic control. Here, adult leaf and metamer traits were measured for 39 tree species from a tropical moist semi-evergreen forest (1580 mm rain yr(-1)) and 41 species from a dry deciduous forest (1160 mm yr(-1)) in Bolivia. Twenty-six functional traits were measured and related to species regeneration light requirements.Adult leaf traits were clearly associated with shade tolerance. Different, rather than stronger, shade adaptations were found for moist compared with dry forest species. Shade adaptations exclusively found in the evergreen moist forest were related to tough and persistent leaves, and shade adaptations in the dry deciduous forest were related to high light interception and water use.These results suggest that, for forests differing in rainfall seasonality, there is a shift in the relative importance of functional leaf traits and performance trade-offs that control light partitioning. In the moist evergreen forest leaf traits underlying the growth-survival trade-off are important, whereas in the seasonally deciduous forest leaf traits underlying the growth trade-off between low and high light might become important.
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Bourdier, Thomas; Cordonnier, Thomas; Kunstler, Georges; Piedallu, Christian; Lagarrigues, Guillaume; Courbaud, Benoit
2016-01-01
Plant structural diversity is usually considered as beneficial for ecosystem functioning. For instance, numerous studies have reported positive species diversity-productivity relationships in plant communities. However, other aspects of structural diversity such as individual size inequality have been far less investigated. In forests, tree size inequality impacts directly tree growth and asymmetric competition, but consequences on forest productivity are still indeterminate. In addition, the effect of tree size inequality on productivity is likely to vary with species shade-tolerance, a key ecological characteristic controlling asymmetric competition and light resource acquisition. Using plot data from the French National Geographic Agency, we studied the response of stand productivity to size inequality for ten forest species differing in shade tolerance. We fitted a basal area stand production model that included abiotic factors, stand density, stand development stage and a tree size inequality index. Then, using a forest dynamics model we explored whether mechanisms of light interception and light use efficiency could explain the tree size inequality effect observed for three of the ten species studied. Size inequality negatively affected basal area increment for seven out of the ten species investigated. However, this effect was not related to the shade tolerance of these species. According to the model simulations, the negative tree size inequality effect could result both from reduced total stand light interception and reduced light use efficiency. Our results demonstrate that negative relationships between size inequality and productivity may be the rule in tree populations. The lack of effect of shade tolerance indicates compensatory mechanisms between effect on light availability and response to light availability. Such a pattern deserves further investigations for mixed forests where complementarity effects between species are involved. When studying the effect of structural diversity on ecosystem productivity, tree size inequality is a major facet that should be taken into account.
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Meng, Fengqun; Cao, Rui; Yang, Dongmei; Niklas, Karl J; Sun, Shucun
2013-07-01
In theory, plants can alter the distribution of leaves along the lengths of their twigs (i.e., within-twig leaf distribution patterns) to optimize light interception in the context of the architectures of their leaves, branches and canopies. We hypothesized that (i) among canopy tree species sharing similar light environments, deciduous trees will have more evenly spaced within-twig leaf distribution patterns compared with evergreen trees (because deciduous species tend to higher metabolic demands than evergreen species and hence require more light), and that (ii) shade-adapted evergreen species will have more evenly spaced patterns compared with sun-adapted evergreen ones (because shade-adapted species are generally light-limited). We tested these hypotheses by measuring morphological traits (i.e., internode length, leaf area, lamina mass per area, LMA; and leaf and twig inclination angles to the horizontal) and physiological traits (i.e., light-saturated net photosynthetic rates, Amax; light saturation points, LSP; and light compensation points, LCP), and calculated the 'evenness' of within-twig leaf distribution patterns as the coefficient of variation (CV; the higher the CV, the less evenly spaced leaves) of within-twig internode length for 9 deciduous canopy tree species, 15 evergreen canopy tree species, 8 shade-adapted evergreen shrub species and 12 sun-adapted evergreen shrub species in a subtropical broad-leaved rainforest in eastern China. Coefficient of variation was positively correlated with large LMA and large leaf and twig inclination angles, which collectively specify a typical trait combination adaptive to low light interception, as indicated by both ordinary regression and phylogenetic generalized least squares analyses. These relationships were also valid within the evergreen tree species group (which had the largest sample size). Consistent with our hypothesis, in the canopy layer, deciduous species (which were characterized by high LCP, LSP and Amax) had more even leaf distribution patterns than evergreen species (which had low LCP, LSP and Amax); shade-adapted evergreen species had more even leaf distribution patterns than sun-adapted evergreen species. We propose that the leaf distribution pattern (i.e., 'evenness' CV, which is an easily measured functional trait) can be used to distinguish among life-forms in communities similar to the one examined in this study.
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Becoming less tolerant with age: sugar maple, shade, and ontogeny.
Sendall, Kerrie M; Lusk, Christopher H; Reich, Peter B
2015-12-01
Although shade tolerance is often assumed to be a fixed trait, recent work suggests ontogenetic changes in the light requirements of tree species. We determined the influence of gas exchange, biomass distribution, and self-shading on ontogenetic variation in the instantaneous aboveground carbon balance of Acer saccharum. We quantified the aboveground biomass distributions of 18 juveniles varying in height and growing in low light in a temperate forest understory in Minnesota, USA. Gas exchange rates of leaf and stem tissues were measured, and the crown architecture of each individual was quantified. The YPLANT program was used to estimate the self-shaded fraction of each crown and to model net leaf-level carbon gain. Leaf respiration and photosynthesis per gram of leaf tissue increased with plant size. In contrast, stem respiration rates per gram of stem tissue declined, reflecting a shift in the distribution of stem diameter sizes from smaller (with higher respiration) to larger diameter classes. However, these trends were outweighed by ontogenetic increases in self-shading (which reduces the net photosynthesis realized) and stem mass fraction (which increases the proportion of purely respiratory tissue) in terms of influence on net carbon exchange. As a result, net carbon gain per gram of aboveground plant tissue declined with increasing plant size, and the instantaneous aboveground light compensation point increased. When estimates of root respiration were included to model whole-plant carbon gain and light compensation points, relationships with plant size were even more pronounced. Our findings show how an interplay of gas exchange, self-shading, and biomass distribution shapes ontogenetic changes in shade tolerance.
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Graham, Eric A; Andrade, Jose Luis
2004-05-01
Vertical stratification of epiphytes generally has not been reported for dry forests. For two epiphytic Crassulacean acid metabolism bromeliads that segregate vertically, it was hypothesized that different potentials for photoprotection or shade tolerance rather than drought tolerance is responsible for the observed stratification. The light environment, capacity for photoprotection, germination response to light quality, and responses to light and drought were thus examined for Tillandsia brachycaulos and T. elongata. Vertical and light-environment distributions differed for the two species but photoprotection and photodamage did not where they occurred at similar field locations; T. brachycaulos had a higher pigment acclimation to light. Tillandsia brachycaulos had higher acid accumulation under low light as opposed to T. elongata, which responded similarly to all but the highest light treatment. Tillandsia brachycaulos maintained positive total daily net CO(2) uptake through 30 d of drought; T. elongata had a total daily net CO(2) loss after 7 d of drought. The vertical stratification was most likely the result of the sensitivity to drought of T. elongata rather than differences in photoprotection or shade tolerance between the two species. Tillandsia elongata occurs in more exposed locations, which may be advantageous for rainfall interception and dew formation.
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Uniform versus Asymmetric Shading Mediates Crown Recession in Conifers
Schoonmaker, Amanda L.; Lieffers, Victor J.; Landhäusser, Simon M.
2014-01-01
In this study we explore the impact of asymmetrical vs. uniform crown shading on the mortality and growth of upper and lower branches within tree crowns, for two conifer species: shade intolerant lodgepole pine (Pinus contorta) and shade tolerant white spruce (Picea glauca). We also explore xylem hydraulics, foliar nutrition, and carbohydrate status as drivers for growth and expansion of the lower and upper branches in various types of shading. This study was conducted over a two-year period across 10 regenerating forest sites dominated by lodgepole pine and white spruce, in the lower foothills of Alberta, Canada. Trees were assigned to one of four shading treatments: (1), complete uniform shading of the entire tree, (2) light asymmetric shading where the lower 1/4–1/3 of the tree crown was shaded, (3) heavy asymmetric shading as in (2) except with greater light reduction and (4) control in which no artificial shading occurred and most of the entire crown was exposed to full light. Asymmetrical shading of only the lower crown had a larger negative impact on the bud expansion and growth than did uniform shading, and the effect was stronger in pine relative to spruce. In addition, lower branches in pine also had lower carbon reserves, and reduced xylem-area specific conductivity compared to spruce. For both species, but particularly the pine, the needles of lower branches tended to store less C than upper branches in the asymmetric shade, which could suggest a movement of reserves away from the lower branches. The implications of these findings correspond with the inherent shade tolerance and self-pruning behavior of these conifers and supports a carbon based mechanism for branch mortality – mediated by an asymmetry in light exposure of the crown. PMID:25136823
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Uniform versus asymmetric shading mediates crown recession in conifers.
Schoonmaker, Amanda L; Lieffers, Victor J; Landhäusser, Simon M
2014-01-01
In this study we explore the impact of asymmetrical vs. uniform crown shading on the mortality and growth of upper and lower branches within tree crowns, for two conifer species: shade intolerant lodgepole pine (Pinus contorta) and shade tolerant white spruce (Picea glauca). We also explore xylem hydraulics, foliar nutrition, and carbohydrate status as drivers for growth and expansion of the lower and upper branches in various types of shading. This study was conducted over a two-year period across 10 regenerating forest sites dominated by lodgepole pine and white spruce, in the lower foothills of Alberta, Canada. Trees were assigned to one of four shading treatments: (1), complete uniform shading of the entire tree, (2) light asymmetric shading where the lower 1/4-1/3 of the tree crown was shaded, (3) heavy asymmetric shading as in (2) except with greater light reduction and (4) control in which no artificial shading occurred and most of the entire crown was exposed to full light. Asymmetrical shading of only the lower crown had a larger negative impact on the bud expansion and growth than did uniform shading, and the effect was stronger in pine relative to spruce. In addition, lower branches in pine also had lower carbon reserves, and reduced xylem-area specific conductivity compared to spruce. For both species, but particularly the pine, the needles of lower branches tended to store less C than upper branches in the asymmetric shade, which could suggest a movement of reserves away from the lower branches. The implications of these findings correspond with the inherent shade tolerance and self-pruning behavior of these conifers and supports a carbon based mechanism for branch mortality--mediated by an asymmetry in light exposure of the crown.
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Shade factors for 149 taxa of in-leaf urban trees in the USA
E. Gregory McPherson; Qingfu Xiao; Natalie S. van Doorn; Nels Johnson; Shannon Albers; Paula J. Peper
2018-01-01
Shade factors, defined as the percentage of sky covered by foliage and branches within the perimeter of individual tree crowns, have been used to model the effects of trees on air pollutant uptake, building energy use and rainfall interception. For the past 30 years the primary source of shade factors was a database containing values from 47 species. In most...
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Influence of Shoot Structure on Light Interception and Photosynthesis in Conifers
Carter, Gregory A.; Smith, William K.
1985-01-01
The influence of shoot structure on net photosynthesis was evaluated under field conditions for the central Rocky Mountain (United States) conifers Picea engelmannii (Parry ex Engelm.), Abies lasiocarpa ([Hook] Nutt.), and Pinus contorta (Engelm.). In all species, the greater number of needles per unit stem length on sun shoots correlated with a smaller silhouette leaf area to total leaf area ratio (STAR). Decreased STAR was due primarily to greater needle inclination toward the vertical, plus some needle mutual shading. However, photosynthesis expressed on a total leaf area basis did not decrease in sun shoots (lower STAR) but remained nearly constant at approximately 3 micromoles per square meter per second over a wide range of STAR (0.1 to 0.3). Relatively low light saturation levels of 200 to 1400 microeinsteins per square meter per second and diffuse light to 350 microeinsteins per meter per second maintained photosynthetic flux densities in inclined and/or shaded needles at levels comparable to those in unshaded needles oriented perpendicular to the solar beam. As a result, net CO2 uptake per unit stem length increased as much as 2-fold in sun shoots (low STAR) in direct proportion to increasing needle density. PMID:16664525
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Loik, Michael E
2008-09-01
Cactus spines reduce herbivory, direct water toward roots and reduce the impacts of high- and low-temperature extremes. Yet, shading of stems by spines reduces incident photosynthetic photon flux density (PFD), photosynthesis and growth. This study compared spinescence, PFD interception, stem temperature, Photosystem II (PSII) photochemistry and xanthophyll pigment composition for three species of cacti from the Mojave Desert, CA. The species vary in spinescence: Opuntia basilaris, which has no central or radial spines; Opuntia erinacea, which is densely covered with spines; and Opuntia phaeacantha, which has an intermediate coverage of spines. The role of spines was tested by removing spines from stems of O. erinacea. PFD interception was similar for both O. basilaris and O. phaeacantha, and about three times that for densely spined O. erinacea; removal of spines increased incident PFD three-fold. There were no effects of spines on stem temperatures. Steady-state light-response curves of chlorophyll a fluorescence from PSII indicated that PhiPSII, photochemical quenching (qP) and electron flux within PSII were lower, and non-photochemical quenching was higher, for O. erinacea in comparison to the other two species with less spines. After 2 months, qP was higher and electron flux lower, and xanthophyll pigment pool size was higher, for stems from which spines had been removed compared with intact stems. These three species allocate different amounts of biomass to spines, resulting in species-specific PFD interception, PSII photochemistry and xanthophyll pigment pool size, which may help maintain rates of photosynthesis during the hot, dry Mojave Desert summer.
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Photosynthetic light capture and processing from cell to canopy
DOE Office of Scientific and Technical Information (OSTI.GOV)
Stenberg, P.; DeLucia, E.H.; Schoettle, A.W.
1995-07-01
We have addressed the unique structural features of conifers, as they relate to photosynthetic production, at different levels of organization (from needle to canopy). Many concepts and measures must be defined for conifers so that they are consistent with the structural properties of needles and shoots. Consistency is needed in comparing the photosynthetic performance of conifers and broad leaves, wherein it is important to distinguish the effect of structural factors on light capture from differences in the photosynthetic response at a fixed interception. Needles differ from broad leaves both with respect to inner structure and external shape, which includes amore » continuum from nearly flat to cylindrical. For nonflat three-dimensional objects such as for conifer needles, total surface area is the natural measure. The meaning of the one-sided area of needles is not clear, but consistency requires that it be defined as half the total needle surface area, as concluded. Characteristic structural factors of conifers that affect their ability to harvest light are a deep canopy combined with a small needle size, which create an important penumbra effect, and the clustering of needles on shoots, which creates a discontinuous distribution of needle area. These factors imply that, at a fixed leaf area index, the intercepted PAR would be smaller in coniferous than in broad-leafed canopies, but the vertical gradient of light in conifers is less steep and light reaching the lower canopy is all penumbral (diffuse). Conifers can maintain a higher leaf area index, and this may be accomplished by a more even distribution of light between shoots at different locations in the canopy and also because shade shoots have a structure that effectively intercepts light. Broad leaves in general have higher maximum photosynthetic rates than do needles, and yet conifers are at least equally productive on a stand basis. Possible reasons are discussed.« less
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NASA Astrophysics Data System (ADS)
Fotis, A. T.; Curtis, P.
2016-12-01
Canopy structure influences forest productivity through its effects on the distribution of radiation and the light-induced changes in leaf physiological traits. Due to the difficulty of accessing and measuring forest canopies, few field-based studies have quantitatively linked these divergent scales of canopy functioning. The objective of our study was to investigate how canopy structure affects light profiles within a forest canopy and whether leaves of mature trees adjust morphologically and biochemically to the light environments characteristic of canopies with different structural complexity. We used a combination of light detection and ranging (LiDAR) data and hemispherical photographs to quantify canopy structure and light environments, respectively, and a telescoping pole to sample leaves. Leaf mass per area (LMA), nitrogen on an area basis (Narea) and chlorophyll on a mass basis (Chlmass) were measured in four co-dominant species (Acer rubrum, Fagus grandifolia, Pinus strobus and Quercus rubra) at different heights in plots with similar leaf area index (LAI) but contrasting canopy complexity (rugosity). We found that more complex canopies had greater porosity and reduced light variability in the midcanopy while total light interception was unchanged relative to less complex canopies. Leaves of F. grandifolia, Q. rubra, and P. strobus shifted towards sun-acclimation phenotypes with increasing canopy complexity while leaves of A. rubrum became more shade-acclimated (lower LMA) in the upper canopy of more complex stands, despite no differences in total light interception. Broadleaf species showed further acclimation by increasing Narea and reducing Chlmass as LMA increased, while P. strobus showed no change in Narea and Chlmass with increasing LMA. Our results provide new insight on how light distribution and leaf acclimation in mature trees might be altered when natural and anthropogenic disturbances cause structural changes in the canopy.
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Reich, Peter B; Falster, Daniel S; Ellsworth, David S; Wright, Ian J; Westoby, Mark; Oleksyn, Jacek; Lee, Tali D
2009-01-01
* Here, we evaluated how increased shading and declining net photosynthetic capacity regulate the decline in net carbon balance with increasing leaf age for 10 Australian woodland species. We also asked whether leaves at the age of their mean life-span have carbon balances that are positive, zero or negative. * The net carbon balances of 2307 leaves on 53 branches of the 10 species were estimated. We assessed three-dimensional architecture, canopy openness, photosynthetic light response functions and dark respiration rate across leaf age sequences on all branches. We used YPLANT to estimate light interception and to model carbon balance along the leaf age sequences. * As leaf age increased to the mean life-span, increasing shading and declining photosynthetic capacity each separately reduced daytime carbon gain by approximately 39% on average across species. Together, they reduced daytime carbon gain by 64% on average across species. * At the age of their mean life-span, almost all leaves had positive daytime carbon balances. These per leaf carbon surpluses were of a similar magnitude to the estimated whole-plant respiratory costs per leaf. Thus, the results suggest that a whole-plant economic framework, including respiratory costs, may be useful in assessing controls on leaf longevity.
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[Response of photosynthetic characteristics of peanut seedlings leaves to low light].
Zhang, Kun; Wan, Yong-shan; Liu, Feng-zhen; Zhang, Er-qun; Wang, Su
2009-12-01
To investigate the effects of shading and light recovery on the photosynthetic characteristics of peanut seedlings leaves, different shading treatments including no shading, 27% shading, 43% shading, and 77% shading were performed with black sunshade net at the seedling stage of two peanut cultivars Fenghua 1 and Fenghua 2, with related parameters determined. It was shown that with the increase of shading degree, the leaf chlorophyll content, actual PSII photochemical efficiency under irradiance (phi(PS II)), and maximum PS II photochemical efficiency (Fv/Fm) of test cultivars increased, while the Chl a/b ratio and photosynthetic rate (Pn) decreased. On the first day after light recovery, the Pn and stomatal conductance (Gs) decreased while the intercellular CO2 concentration (Ci) increased with increasing shading degree when measured under high light, but the Pn increased and the Gs and Ci decreased with increasing shading degree when measured under low light. The ratio of Pn measured under low light to that measured under high light increased significantly. With increasing shading degree, the light compensation point, light saturation point, CO2 compensation point, CO2 saturation point, and carboxylation efficiency decreased, while the apparent quantum yield increased. After the removal of shading, the Pn, phi(PS II), and Fv/Fm under natural light decreased immediately, but increased gradually 3-5 days after. 15 days after light recovery, the Pn, phi(PS II) and Fv/Fm in treatment 27% shading recovered to the level of no shading. As for the other treatments, the restored extent differed with shading degree and test variety. In the same treatments, the leaf chlorophyll content, Pn and phi(PS II) of Fenghua 1 were higher than those of Fenghua 2. The results demonstrated that shading at seedling stage improved the capabilities of test varieties in using low light, but reduced the capabilities in using high light.
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NASA Astrophysics Data System (ADS)
Syafrullah; Marlina, N.; Rahim, S. E.; Aminah, R. I. S.; Midranisiah; Rosmiah; Sakalena, F.
2017-06-01
This research was conducted in wetlands Semambu Village, District of North Indralaya, Ogan Ilir, South Sumatra Province, Indonesia, which lasted from July 2015 to February 2016. The observation of a microclimate indicate that the average intensity of light outside the auspices of the plot 1968.9 m2s mol1, under waranet 1502.40 mol1 m2s, below paranet 721.99 mol1 m2s-1 and under waranet 439.25 μmol m2s-1 - equivalent to the light interception 1 or 100%, 76%, 37% and 22%. Results of soil chemical analysis that the soil has a low fertility study (H2O pH of 3.32, organic C 4.47%, total N 0.35%, Bray P 13.30 ppm, K-ea 0.26 me / 100g, CEC 19.6 rne / 100g and Al-ea 3.28 me / 100g). Tests on 22 genotypes of maize grown with light interception 100%, 76%. 37% and 22%, by calculating tolerance index based on the weight of dry seed cob-1 was found four genotypes of maize tend to be tolerant to low-intensity light that were genotype B 41, Pioneer 27, Sukmaraga and Sugihan. The test results of corn planted in beds shade with light interception 100%, 76%, 37% and 22% for groups of maize tolerant and sensitive, followed by application of urea 0 kg ha1, 100 kg ha-1 200 kg ha-1, 300 kg ha-1 and 400 kg ha-1 indicate that maize and 41 and Pioneer 27 by Urea 300 kg ha-1 gives better results than other varieties at different intensities of light oil palm age of 12 years with applications Urea fertilizer 300 kg ha-1, indicating that the B 41 and Pioneer 27 tends to give better results compared with other varieties. The application of a polyculture system palm-maize can produce 1000 kg of dry grain of corn in a 1 ha of oil palm cultivation.
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Influence of light source, polarization, education, and training on shade matching quality.
Clary, Jacqueline A; Ontiveros, Joe C; Cron, Stanley G; Paravina, Rade D
2016-07-01
Many factors influence the quality of shade selection, and isolating how significantly each of these factors influences results is difficult. The purpose of this in vitro study was to compare results of shade matching using handheld lights with or without a polarizing filter with results obtained using a professional viewing booth and to analyze the influence of education and training on shade selection outcome. A total of 96 third-year dental students (evaluators) were randomly separated into 4 groups. Each group was assigned 1 of 2 handheld shade-matching devices (lights) with or without a polarizing filter. Each group performed a shade matching exercise using the handheld light or a professional viewing booth. The exercise consisted of matching shade tabs placed in a typodont to a commercial shade guide. Each group repeated this procedure 4 times over a 9-week period. A lecture on shade matching was presented at the fifth week of the study, between "before" and "after" shade matching procedures. Shade matching scores with handheld lights (7.8) were higher than scores of shade matching with the viewing booth (7.2). The mean scores for before (7.2) and after (7.8) shade matching (with education and training in between) were significantly different. The combined effect of light and education and training improved the shade matching score by 1.2, from 6.8 in the before sessions using the viewing booth to 8.0 in the after sessions using handheld lights. A 21% increase in the number of evaluators who selected 1 of 4 best matches was recorded, 10% for handheld lights versus viewing booth after education and training versus before sessions and 11% between after sessions using handheld lights versus before sessions using viewing booth. Within the limits of the study, the shade matching scores with handheld lights were significantly better than the results obtained using a viewing booth (P<.01). Using a handheld light with or without a polarizing filter did not influence shade matching results. Mean shade matching scores were significantly better after education and training (P<.01). Light combined with education and training resulted in the greatest increase in shade matching quality. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
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Effects of a shade-matching light and background color on reliability in tooth shade selection.
Najafi-Abrandabadi, Siamak; Vahidi, Farhad; Janal, Malvin N
2018-01-01
The purpose of this study was to evaluate the effects of a shade-matching light (Rite-Lite-2, AdDent) and different viewing backgrounds on reliability in a test of shade tab matching. Four members of the Prosthodontic faculty matched 10 shade tabs selected for a range of shades against the shade guide. All raters were tested for color blindness and were calibrated prior to the study. Matching took place under four combinations of conditions: with operatory light or the shade-matching light, and using either a pink or a blue background. Reliability was quantified with the kappa statistic, separately for agreement of value, hue, and chroma for each shade tab. In general, raters showed fair to moderate levels of agreement when judging the value of the shade tabs, but could not agree on the hue and chroma of the stimuli. The pink background led to higher levels of agreement than the blue background, and the shade-matching light improved agreement when used in conjunction with the pink but not the blue background. Moderate levels of agreement were found in matching shade tab value. Agreement was generally better when using the pink rather than the blue background, regardless of light source. The use of the shade-matching light tended to amplify the advantage of the pink background.
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Fotis, Alexander T; Curtis, Peter S
2017-10-01
Canopy structure influences forest productivity through its effects on the distribution of radiation and the light-induced changes in leaf physiological traits. Due to the difficulty of accessing and measuring forest canopies, few field-based studies have quantitatively linked these divergent scales of canopy functioning. The objective of our study was to investigate how canopy structure affects light profiles within a forest canopy and whether leaves of mature trees adjust morphologically and biochemically to the light environments characteristic of canopies with different structural complexity. We used a combination of light detection and ranging (LiDAR) data and hemispherical photographs to quantify canopy structure and light environments, respectively, and a telescoping pole to sample leaves. Leaf mass per area (LMA), nitrogen on an area basis (Narea) and chlorophyll on a mass basis (Chlmass) were measured in red maple (Acer rubrum), american beech (Fagus grandifolia), white pine (Pinus strobus), and northern red oak (Quercus rubra) at different heights in plots with similar leaf area index but contrasting canopy complexity (rugosity). We found that more complex canopies had greater porosity and reduced light variability in the midcanopy while total light interception was unchanged relative to less complex canopies. Leaf phenotypes of F. grandifolia, Q. rubra and P. strobus were more sun-acclimated in the midstory of structurally complex canopies while leaf phenotypes of A. rubrum were more shade-acclimated (lower LMA) in the upper canopy of more complex stands, despite no differences in total light interception. Broadleaf species showed further differences in acclimation with increased Narea and reduced Chlmass in leaves with higher LMA, while P. strobus showed no change in Narea and Chlmass with higher LMA. Our results provide new insight on how light distribution and leaf acclimation in mature trees might be altered when natural and anthropogenic disturbances cause structural changes in the canopy. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Lightness, chroma, and hue distributions of a shade guide as measured by a spectroradiometer.
Lee, Yong-Keun; Yu, Bin; Lim, Ho-Nam
2010-09-01
The color attributes of commercially available shade guides have been measured by spectrophotometers (SP), which are designed to measure flat surfaces. However, there is limited information on the color distribution of shade guides as measured by spectroradiometers (SR), which are capable of measuring the color of curved surfaces. The purpose of this study was to determine the distributions of lightness (CIE L*) and chroma (C*(ab)) step intervals between adjacent shade tabs of a shade guide based on the lightness, chroma, and hue attributes measured by an SR. Lightness, chroma, hue angle, and CIE a* and b* values of the shade tabs (n=26) from a shade guide (Vitapan 3D-Master) were measured by an SR under daylight conditions. The distributions of the ratios in lightness and chroma of each tab compared with the lowest lightness tab or the lowest chroma tab were determined. The values for each color parameter were analyzed by a 3-way ANOVA with the factors of lightness, chroma, and hue designations of the shade tabs (alpha=.05). The chroma and CIE a* and b* values were influenced by the lightness, chroma, and hue designations of the shade tabs (P<.001); however, the lightness and hue angle were influenced by the lightness and hue designations, but not by the chroma designation. Distributions for the CIE a* and b* values, in each lightness group, corresponded with the chroma designation. However, the intervals in the lightness and chroma scales between adjacent tabs were not uniform. The intervals in the color parameters between adjacent shade tabs were not uniform based on SR measurements. Therefore, a shade guide in which shade tabs are more equally spaced by the color attributes, based on the values as measured by an SR along with observers' responses with respect to the equality of the intervals, should be devised. Copyright © 2010 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.
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[Studies on the shade-endurance capacity of Glycyrrhiza uralensis].
Wei, Sheng-li; Wang, Wen-quan; Chen, Xiu-hua; Qin, Shu-ying; Chen, Xiu-tian
2005-01-01
To study the shade-endurance property of Glycyrrhiza uralensis and provide rationale for the practice of inter-cropping G. uralensis with trees. Black shading nets were used to provide five different environments of light intensities (light penetration rates of 100%, 75%, 65%, 50% and 25%, respectively). To assess the shade-endurance capacity of G. uralensis, several aspects were evaluated, including growth characters, physiological and ecological characters, biomass, and chemical contents. G. uralensis is a light-favored plant. The growth indices such as plant height, stem diameter, leaves number, root diameter, biomass, and daily average photosynthetic rate (Pn) are highest when light permeation rate is 100%. All these indices decrease when light intensity decreases. However, G. uralensis possesses shade-endurance capacity to some degree; it adapts to the shading environment by increasing the leaf area and chlorophyll contents. Shading has no obvious effect on the absolute light energy utilization rate (Eu) or Fv/Fm ratio. The influence of shading on the chemical contents of G. uralensis is obvious.
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Parra-Tabla, V; Munguía-Rosas, M; Campos-Navarrete, M J; Ramos-Zapata, J A
2015-01-01
Although it is known that floral dimorphism contributes to the maintenance of mixed breeding systems, the consequences of producing progeny of a contrasting genetic background and seeds with differential resource allocation has been practically ignored regarding establishment of belowground organisms-plant interactions. This article evaluates the combined effect of floral dimorphism with cross type and light environment on interactions between Ruellia nudiflora and arbuscular mycorrhizal fungi (AMF). R. nudiflora produces cleistogamous (CL) flowers that exhibit obligate self-pollination and chasmogamous (CH) flowers with facultative self- (CHs) or cross- (CHc) pollination. We evaluated the establishment of the plant-AMF interaction in progeny derived from each floral type, under two light conditions (shaded versus open). We established different scenarios depending on the existence of inbreeding depression (ID) and whether the differential resource allocation (DRA) to CH and CL flowers affected the R. nudiflora-AMF interaction. We predicted that under shaded light conditions there might be an intensification of ID, having a negative effect on AMF colonisation. The percentages of hyphae and vesicles in the harvested roots was significantly higher in the shaded plants (F ≥ 4.11, P < 0.05), while progeny of CHc and CHs presented a higher percentage of hyphae and vesicle colonisation compared to CL progeny (F = 15.26, P < 0.01). The results show that DRA to CH flowers and light availability both determines the establishment of R. nudiflora-AMF interaction. The results also suggest that even under stressful light conditions, endogamy does not affect this interaction, which may explain the success of R. nudiflora as an invasive species. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.
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The impact of translucent fabric shades and control strategies on energy savings and visual quality
NASA Astrophysics Data System (ADS)
Wankanapon, Pimonmart
Translucent fabric shades provide opportunities for building occupants to control sunlight penetration for heat reduction, thermal comfort, and visual quality. Regulating shades affects building energy and can potentially reduce the size of mechanical cooling systems. Shades are not normally included in energy model studies during the design process, even though shades potential impact energy use. This is because the occupants normally leave shades closed a large fraction of the time, but models are generally performed with no shades. Automatic shade control is now available, so it is necessary to understand the impact of shades on visual quality and their energy saving potential in order to optimize their overall performance. There are very limited studies that have address shades and their integrated performance on energy consumption and visual quality. Most of these do not reflected modern shade types and their application. The goals of this study are: First, to determine the impact of shades on total, heating, cooling and lighting energy savings with different design and operation parameters. Second, to study and develop different automatic shade control strategies to promote and optimize energy savings and visual quality. A simulation-based approach using EnergyPlus in a parametric study provide better understanding energy savings under different shade conditions. The parametric runs addressed various building parameters such as geometry, orientation, site climate, glazing/shade properties, and shade control strategies with integrated lighting control. The impact of shades was determined for total building and space heating, cooling and lighting energy savings. The effect of shades on visual quality was studied using EnergyPlus, AGI32 and DAYSIM for several indices such as daylight glare index (DGI), work plane illuminance, luminance ratios and view. Different shade control strategies and integrated lighting control were considered with two translucent fabric shade colors. The results clearly show the benefit of automatic shade control strategies with integrated lighting control over a condition when shades are closed all day. The main contributor to the total energy savings is from lighting energy savings, followed by cooling energy savings. Shades provide greater benefit in a hot climate and in a moderate climate than in a cold climate. Different control strategies provide savings in the range of 7-35% for annual total space energy with higher savings with light colored shades. Control strategies of shades should be selected and optimized based on climate, orientation, window area, and window/shade properties. High performance glazings, when equipped with shades, show lower energy savings when compared to standard glazings. High transmittance/reflectance shades, such as white shades, perform better than dark shades in most of the cases due to higher lighting energy savings obtained with the automatic electric lighting control and the resulting cooling energy savings from rejection of some solar energy and a reduction in the heat from lights. A South orientation showed the least benefit of automatic control of shades when compare to other orientations due to the large fraction of time shades are required to provide visual comfort. Under automatic shade control, energy savings are higher the more often the shades can be raised. The different automatic control strategies present tradeoffs between energy savings and comfort. With regard to visual quality, daylight quality assessments on view, glare, luminance ratios, and UDI can be used to assess shade control strategies. Automatic shade control can increase the number of view hours while controlling sunlight penetration. With automatic shade control, more daylight hours can be provided within the beneficial range of 100-2000 lux compared to shades that are closed all day. For a person facing the window, discomfort glare is likely to increase the more often the shades are raised. Keeping the shades down ensures an acceptable glare condition, but limits energy savings. Luminance ratios are another metric that can be used to assess shade performance. With white shades, the luminance ratios between the task and proximate surfaces are improved. Dark shades help improve the luminance ratios between the task and distant surfaces. When the shades are left open, even with no direct sunlight in the space, task to window luminance ratios will often exceed 1:10.
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Ventre-Lespiaucq, Agustina; Flanagan, Nicola S; Ospina-Calderón, Nhora H; Delgado, Juan A; Escudero, Adrián
2018-01-01
Crown architecture usually is heterogeneous as a result of foraging in spatially and temporally heterogeneous light environments. Ecologists are only beginning to identify the importance of temporal heterogeneity for light acquisition in plants, especially at the diurnal scale. Crown architectural heterogeneity often leads to a diurnal variation in light interception. However, maximizing light interception during midday may not be an optimal strategy in environments with excess light. Instead, long-lived plants are expected to show crown architectures and leaf positions that meet the contrasting needs of light interception and avoidance of excess light on a diurnal basis. We expected a midday depression in the diurnal course of light interception both at the whole-crown and leaf scales, as a strategy to avoid the interception of excessive irradiance. We tested this hypothesis in a population of guava trees ( Psidium guajava L.) growing in an open tropical grassland. We quantified three crown architectural traits: intra-individual heterogeneity in foliage clumping, crown openness, and leaf position angles. We estimated the diurnal course of light interception at the crown scale using hemispheric photographs, and at the leaf scale using the cosine of solar incidence. Crowns showed a midday depression in light interception, while leaves showed a midday peak. These contrasting patterns were related to architectural traits. At the crown scale, the midday depression of light interception was linked to a greater crown openness and foliage clumping in crown tops than in the lateral parts of the crown. At the leaf scale, an average inclination angle of 45° led to the midday peak in light interception, but with a huge among-leaf variation in position angles. The mismatch in diurnal course of light interception at crown and leaf scales can indicate that different processes are being optimized at each scale. These findings suggest that the diurnal course of light interception may be an important dimension of the resource acquisition strategies of long-lived woody plants. Using a temporal approach as the one applied here may improve our understanding of the diversity of crown architectures found across and within environments.
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Ventre-Lespiaucq, Agustina; Flanagan, Nicola S.; Ospina-Calderón, Nhora H.; Delgado, Juan A.; Escudero, Adrián
2018-01-01
Crown architecture usually is heterogeneous as a result of foraging in spatially and temporally heterogeneous light environments. Ecologists are only beginning to identify the importance of temporal heterogeneity for light acquisition in plants, especially at the diurnal scale. Crown architectural heterogeneity often leads to a diurnal variation in light interception. However, maximizing light interception during midday may not be an optimal strategy in environments with excess light. Instead, long-lived plants are expected to show crown architectures and leaf positions that meet the contrasting needs of light interception and avoidance of excess light on a diurnal basis. We expected a midday depression in the diurnal course of light interception both at the whole-crown and leaf scales, as a strategy to avoid the interception of excessive irradiance. We tested this hypothesis in a population of guava trees (Psidium guajava L.) growing in an open tropical grassland. We quantified three crown architectural traits: intra-individual heterogeneity in foliage clumping, crown openness, and leaf position angles. We estimated the diurnal course of light interception at the crown scale using hemispheric photographs, and at the leaf scale using the cosine of solar incidence. Crowns showed a midday depression in light interception, while leaves showed a midday peak. These contrasting patterns were related to architectural traits. At the crown scale, the midday depression of light interception was linked to a greater crown openness and foliage clumping in crown tops than in the lateral parts of the crown. At the leaf scale, an average inclination angle of 45° led to the midday peak in light interception, but with a huge among-leaf variation in position angles. The mismatch in diurnal course of light interception at crown and leaf scales can indicate that different processes are being optimized at each scale. These findings suggest that the diurnal course of light interception may be an important dimension of the resource acquisition strategies of long-lived woody plants. Using a temporal approach as the one applied here may improve our understanding of the diversity of crown architectures found across and within environments. PMID:29904391
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Role of riparian shade on the fish assemblage of a reservoir littoral
Raines, C. D.; Miranda, Leandro E.
2016-01-01
Research into the effects of shade on reservoir fish assemblages is lacking, with most investigations focused on streams. Unlike many streams, the canopy in a reservoir shades only a narrow fringe of water adjacent to the shoreline, and may not have the influential effect on the aquatic environment reported in streams. We compared fish assemblages between shaded and unshaded sites in a shallow reservoir. Overall species richness (gamma diversity) was higher in shaded sites, and fish assemblage composition differed between shaded and unshaded sites. Average light intensity was 66 % lower in shaded sites, and differences in average temperature and dissolved oxygen were small. Unlike streams where shade can have large effects on water physicochemistry, in reservoirs shade-related differences in fish assemblages seemed to be linked principally to differences in light intensity. Diversity in light intensity in shaded and unshaded sites in reservoirs can create various mosaics of light-based habitats that enable diversity of species assemblages. Managing to promote the habitat diversity provided by shade may require coping with the artificial nature of reservoir riparian zones and water level fluctuations.
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NASA Astrophysics Data System (ADS)
Zapater, M.; Breda, N.; Storchi, G.; Granier, A.
2005-12-01
Intra and interspecific variability in leaf gas exchange (net assimilation, stomatal conductance, transpiration, water use efficiency: WUE), in carbon isotope composition (d13C) and leaf characteristics related to photosynthesis was assessed in 5 trees species growing in a young broad-leaved mixed forest in North-Eastern France (Hesse, Lorraine). The studied species belong to contrasted functional groups of light tolerance: European beech (Fagus sylvatica) as shade tolerant species; sessile oak (Quercus petraea) and hornbeam (Carpinus betulus) as semitolerant species; silver birch (Betula pendula) and European aspen (Populus tremula) as shade intolerant species (pioneer species). Gas exchange was measured at leaf level in the upper and the lower canopy layers using a portable system (LI-6200, Licor). d13C signatures were determined in the sun and shade leaves in both bulk material and soluble sugars. Clear differences in bulk leaves and soluble sugars d13C and intrinsic WUEint were found among the investigated species, whatever the leaf location in the canopy. Within each tree species, shade leaves exhibited lower WUEint and more negative d13C than sun leaves. Little variability among trees was found for a given species. The 3 functional groups were separated by their leaf carbon content. Nevertheless each of the variables d13C, leaf mass area and nitrogen content, alone, could not separate the groups. A linear relationship was found between WUEint and d13C at the intraspecific level (r2 = 0.87 for leaves; r2 =0.89 for sugars) and at the interspecific level (r2 = 0.72 for bulk leaves). Nevertheless, this relationship differed from that of Farquhar et al. (1982), due to a different intercept, while the slope was the same. The causes of these variations are discussed. Key words: d13C; deciduous; mixed forest; WUEint; shade tolerance.
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Chmura, D J; Modrzyński, J; Chmielarz, P; Tjoelker, M G
2017-03-01
Mechanisms of shade tolerance in tree seedlings, and thus growth in shade, may differ by leaf habit and vary with ontogeny following seed germination. To examine early responses of seedlings to shade in relation to morphological, physiological and biomass allocation traits, we compared seedlings of 10 temperate species, varying in their leaf habit (broadleaved versus needle-leaved) and observed tolerance to shade, when growing in two contrasting light treatments - open (about 20% of full sunlight) and shade (about 5% of full sunlight). We analyzed biomass allocation and its response to shade using allometric relationships. We also measured leaf gas exchange rates and leaf N in the two light treatments. Compared to the open treatment, shading significantly increased traits typically associated with high relative growth rate (RGR) - leaf area ratio (LAR), specific leaf area (SLA), and allocation of biomass into leaves, and reduced seedling mass and allocation to roots, and net assimilation rate (NAR). Interestingly, RGR was not affected by light treatment, likely because of morphological and physiological adjustments in shaded plants that offset reductions of in situ net assimilation of carbon in shade. Leaf area-based rates of light-saturated leaf gas exchange differed among species groups, but not between light treatments, as leaf N concentration increased in concert with increased SLA in shade. We found little evidence to support the hypothesis of a increased plasticity of broadleaved species compared to needle-leaved conifers in response to shade. However, an expectation of higher plasticity in shade-intolerant species than in shade-tolerant ones, and in leaf and plant morphology than in biomass allocation was supported across species of contrasting leaf habit. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.
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Lusk, Christopher H; Onoda, Yusuke; Kooyman, Robert; Gutiérrez-Girón, Alba
2010-04-01
*When grown in a common light environment, the leaves of shade-tolerant evergreen trees have a larger leaf mass per unit area (LMA) than their light-demanding counterparts, associated with differences in lifespan. Yet plastic responses of LMA run counter to this pattern: shade leaves have smaller LMA than sun leaves, despite often living longer. *We measured LMA and cell wall content, and conducted punch and shear tests, on sun and shade leaves of 13 rainforest evergreens of differing shade tolerance, in order to understand adaptation vs plastic responses of leaf structure and biomechanics to shade. *Species shade tolerance and leaf mechanical properties correlated better with cell wall mass per unit area than with LMA. Growth light environment had less effect on leaf mechanics than on LMA: shade leaves had, on average, 40% lower LMA than sun leaves, but differences in work-to-shear, and especially force-to-punch, were smaller. This was associated with a slightly larger cell wall fraction in shade leaves. *The persistence of shade leaves might reflect unattractiveness to herbivores because they yield smaller benefits (cell contents per area) per unit fracture force than sun leaves. In forest trees, cell wall fraction and force-to-punch are more robust correlates of species light requirements than LMA.
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Chen, Tsu-Wei; Henke, Michael; de Visser, Pieter H. B.; Buck-Sorlin, Gerhard; Wiechers, Dirk; Kahlen, Katrin; Stützel, Hartmut
2014-01-01
Background and Aims Maximizing photosynthesis at the canopy level is important for enhancing crop yield, and this requires insights into the limiting factors of photosynthesis. Using greenhouse cucumber (Cucumis sativus) as an example, this study provides a novel approach to quantify different components of photosynthetic limitations at the leaf level and to upscale these limitations to different canopy layers and the whole plant. Methods A static virtual three-dimensional canopy structure was constructed using digitized plant data in GroIMP. Light interception of the leaves was simulated by a ray-tracer and used to compute leaf photosynthesis. Different components of photosynthetic limitations, namely stomatal (SL), mesophyll (ML), biochemical (BL) and light (LL) limitations, were calculated by a quantitative limitation analysis of photosynthesis under different light regimes. Key Results In the virtual cucumber canopy, BL and LL were the most prominent factors limiting whole-plant photosynthesis. Diffusional limitations (SL + ML) contributed <15 % to total limitation. Photosynthesis in the lower canopy was more limited by the biochemical capacity, and the upper canopy was more sensitive to light than other canopy parts. Although leaves in the upper canopy received more light, their photosynthesis was more light restricted than in the leaves of the lower canopy, especially when the light condition above the canopy was poor. An increase in whole-plant photosynthesis under diffuse light did not result from an improvement of light use efficiency but from an increase in light interception. Diffuse light increased the photosynthesis of leaves that were directly shaded by other leaves in the canopy by up to 55 %. Conclusions Based on the results, maintaining biochemical capacity of the middle–lower canopy and increasing the leaf area of the upper canopy would be promising strategies to improve canopy photosynthesis in a high-wire cucumber cropping system. Further analyses using the approach described in this study can be expected to provide insights into the influences of horticultural practices on canopy photosynthesis and the design of optimal crop canopies. PMID:24907313
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Chen, Tsu-Wei; Henke, Michael; de Visser, Pieter H B; Buck-Sorlin, Gerhard; Wiechers, Dirk; Kahlen, Katrin; Stützel, Hartmut
2014-09-01
Maximizing photosynthesis at the canopy level is important for enhancing crop yield, and this requires insights into the limiting factors of photosynthesis. Using greenhouse cucumber (Cucumis sativus) as an example, this study provides a novel approach to quantify different components of photosynthetic limitations at the leaf level and to upscale these limitations to different canopy layers and the whole plant. A static virtual three-dimensional canopy structure was constructed using digitized plant data in GroIMP. Light interception of the leaves was simulated by a ray-tracer and used to compute leaf photosynthesis. Different components of photosynthetic limitations, namely stomatal (S(L)), mesophyll (M(L)), biochemical (B(L)) and light (L(L)) limitations, were calculated by a quantitative limitation analysis of photosynthesis under different light regimes. In the virtual cucumber canopy, B(L) and L(L) were the most prominent factors limiting whole-plant photosynthesis. Diffusional limitations (S(L) + M(L)) contributed <15% to total limitation. Photosynthesis in the lower canopy was more limited by the biochemical capacity, and the upper canopy was more sensitive to light than other canopy parts. Although leaves in the upper canopy received more light, their photosynthesis was more light restricted than in the leaves of the lower canopy, especially when the light condition above the canopy was poor. An increase in whole-plant photosynthesis under diffuse light did not result from an improvement of light use efficiency but from an increase in light interception. Diffuse light increased the photosynthesis of leaves that were directly shaded by other leaves in the canopy by up to 55%. Based on the results, maintaining biochemical capacity of the middle-lower canopy and increasing the leaf area of the upper canopy would be promising strategies to improve canopy photosynthesis in a high-wire cucumber cropping system. Further analyses using the approach described in this study can be expected to provide insights into the influences of horticultural practices on canopy photosynthesis and the design of optimal crop canopies.
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Dong, Tingfa; Li, Junyu; Zhang, Yuanbin; Korpelainen, Helena; Niinemets, Ülo; Li, Chunyang
2015-06-01
The degree to which branches are autonomous in their acclimation responses to alteration in light environment is still poorly understood. We investigated the effects of shading of the sapling crown of Cunninghamia lanceolata (Lamb.) Hook on the whole-tree and mid-crown branch growth and current-year foliage structure and physiology. Four treatments providing 0, 50, 75 and 90% shading compared with full daylight (denoted as Treatment(0), Treatment(50%), Treatment(75%) and Treatment(90%), and Shaded(0), Shaded(50%), Shaded(75%) and Shaded(90%) for the shaded branches and Sunlit(0), Sunlit(50%), Sunlit(75%) and Sunlit(90%) for the opposite sunlit branches under natural light conditions, respectively), were applied over two consecutive growing seasons. Shading treatments decreased the growth of basal stem diameter, leaf dry mass per unit leaf area, stomatal conductance, transpiration rate, the ratio of water-soluble to structural leaf nitrogen content, photosynthetic nitrogen-use efficiency and instantaneous and long-term (estimated from carbon isotope composition) water-use efficiency in shaded branches. Differences between shaded and sunlit branches increased with increasing severity and duration of shading. A non-autonomous, partly compensatory behavior of non-shaded branches was observed for most traits, thus reflecting the dependence between the traits of sunlit branches and the severity of shading of the opposite crown half. The results collectively indicated that tree growth and branch and leaf acclimation responses of C. lanceolata are not only affected by the local light environment, but also by relative within-crown light conditions. We argue that such a non-autonomous branch response to changes in light conditions can improve whole-tree resource optimization. These results contribute to better understanding of tree growth and utilization of water and nitrogen under heterogeneous light conditions within tree canopies. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Arikawa, Hiroyuki; Kanie, Takahito; Fujii, Koichi; Ban, Seiji
2005-12-01
The purpose of this study was to investigate the effect of radiation light characteristics--of different types of clinical light-curing unit--on polymerization efficiency, as determined by the surface hardness of light-cured paint-on resins. Four shades of paint-on resin for shade modification of restorative resins were used. Materials were cured using one laboratory and three clinical light-curing units with different light sources, namely tungsten-halogen, LED, plasma arc, and xenon flash lamps. Knoop hardness measurements were taken at both the top and bottom surfaces of the specimens to assess the mechanical properties and degree of polymerization. Both LED and plasma arc light units caused significantly poorer surface hardness than the halogen and laboratory xenon lights. In addition, the transparent shade was more sensitive to surface hardness than other chromatic shades. Our results indicated that the polymerization efficiency of paint-on resin was significantly influenced by the radiation light characteristics of clinical light-curing units.
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Yano, S; Terashima, I
2001-12-01
Physiological and ecological characteristics of sun and shade leaves have been compared in detail, but their developmental processes, in particular their light sensory mechanisms, are still unknown. This study compares the development of sun and shade leaves of Chenopodium album L., paying special attention to the light sensory site. We hypothesized that mature leaves sense the light environment, and that this information determines anatomy of new leaves. To examine this hypothesis, we shaded plants partially. In the low-light apex treatment (LA), the shoot apex with developing leaves was covered by a cap made of a shading screen and received photosynthetically active photon flux density (PPFD) of 60 micromol m(-2 )s(-1), while the remaining mature leaves were exposed to 360 micromol m(-2 )s(-1). In the high-light apex treatment (HA), the apex was exposed while the mature leaves were covered by a shade screen. After these treatments for 6 d, we analyzed leaf anatomy and chloroplast ultrastructure. The anatomy of LA leaves with a two-layered palisade tissue was similar to that of sun leaves, while their chloroplasts were shade-type with thick grana. The anatomy of HA leaves and shade leaves was similar and both had one-layered palisade tissue, while chloroplasts of HA leaves were sun-type having thin grana. These results clearly demonstrate that new leaves differentiate depending on the light environment of mature leaves, while chloroplasts differentiate depending on the local light environment.
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Aasamaa, Krõõt; Aphalo, Pedro José
2017-02-01
Stomatal anatomical traits and rapid responses to several components of visible light were measured in Tilia cordata Mill. seedlings grown in an open, fully sunlit field (C-set), or under different kinds of shade. The main questions were: (i) stomatal responses to which visible light spectrum regions are modified by growth-environment shade and (ii) which separate component of vegetational shade is most effective in eliciting the acclimation effects of the full vegetational shade. We found that stomatal opening in response to red or green light did not differ between the plants grown in the different environments. Stomatal response to blue light was increased (in comparison with that of C-set) in the leaves grown in full vegetational shade (IABW-set), in attenuated UVAB irradiance (AB-set) or in decreased light intensity (neutral shade) plus attenuated UVAB irradiance (IAB-set). In all sets, the addition of green light-two or four times stronger-into induction light barely changed the rate of the blue-light-stimulated stomatal opening. In the AB-set, stomatal response to blue light equalled the strong IABW-set response. In attenuated UVB-grown leaves, stomatal response fell midway between IABW- and C-set results. Blue light response by neutral shade-grown leaves did not differ from that of the C-set, and the response by the IAB-set did not differ from that of the AB-set. Stomatal size was not modified by growth environments. Stomatal density and index were remarkably decreased only in the IABW- and IAB-sets. It was concluded that differences in white light responses between T. cordata leaves grown in different light environments are caused only by their different blue light response. Differences in stomatal sensitivity are not dependent on altered stomatal anatomy. Attenuated UVAB irradiance is the most efficient component of vegetational shade in stimulating acclimation of stomata, whereas decreased light intensity plays a minor role. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
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How kelp produce blade shapes suited to different flow regimes: A new wrinkle.
Koehl, M A R; Silk, W K; Liang, H; Mahadevan, L
2008-12-01
Many species of macroalgae have flat, strap-like blades in habitats exposed to rapidly flowing water, but have wide, ruffled "undulate" blades at protected sites. We used the giant bull kelp, Nereocystis luetkeana, to investigate how these ecomorphological differences are produced. The undulate blades of N. luetkeana from sites with low flow remain spread out and flutter erratically in moving water, thereby not only enhancing interception of light, but also increasing drag. In contrast, strap-like blades of kelp from habitats with rapid flow collapse into streamlined bundles and flutter at low amplitude in flowing water, thus reducing both drag and interception of light. Transplant experiments in the field revealed that shape of the blade in N. luetkeana is a plastic trait. Laboratory experiments in which growing blades from different sites were subjected to tensile forces that mimicked the hydrodynamic drag experienced by blades in different flow regimes showed that change in shape is induced by mechanical stress. During growth experiments in the field and laboratory, we mapped the spatial distribution of growth in both undulate and strap-like blades to determine how these different morphologies were produced. The highest growth rates occur near the proximal ends of N. luetkeana blades of both morphologies, but the rates of transverse growth of narrow, strap-like blades are lower than those of wide, undulate blades. If rates of longitudinal growth at the edges of a blade exceed the rate of longitudinal growth along the midline of the blade, ruffles along the edges of the blade are produced by elastic buckling. In contrast, flat blades are produced when rates of longitudinal growth are similar across the width of a blade. Because ruffles are the result of elastic buckling, a compliant undulate N. luetkeana blade can easily be pushed into different configurations (e.g., the wavelengths of the ruffles along the edges of the blade can change, and the whole blade can twist into left- and right-handed helicoidal shapes), which may enhance movements of the blade in flowing water that reduce self-shading and increase mass exchange along blade surfaces.
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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
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Yuen, Suet Wai; Bonebrake, Timothy C
2017-01-01
Artificial night light has the potential to significantly alter visually-dependent species interactions. However, examples of disruptions of species interactions through changes in light remain rare and how artificial night light may alter predator-prey relationships are particularly understudied. In this study, we examined whether artificial night light could impact prey attraction and interception in Nephila pilipes orb weaver spiders, conspicuous predators who make use of yellow color patterns to mimic floral resources and attract prey to their webs. We measured moth prey attraction and interception responses to treatments where we experimentally manipulated the color/contrast of spider individuals in the field (removed yellow markings) and also set up light manipulations. We found that lit webs had lower rates of moth interception than unlit webs. Spider color, however, had no clear impact on moth interception or attraction rates in lit nor unlit webs. The results show that night light can reduce prey interception for spiders. Additionally, this study highlights how environmental and morphological variation can complicate simple predictions of ecological light pollution's disruption of species interactions.
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Yaakub, Siti M; Chen, Eugene; Bouma, Tjeerd J; Erftemeijer, Paul L A; Todd, Peter A
2014-06-30
Seagrasses have substantial capacity to survive long periods of light reduction, but how acclimation to chronic low light environments may influence their ability to cope with additional stress is poorly understood. This study examines the effect of temporal light reduction by adding two levels of shading to Halophila ovalis plants in two meadows with different light histories, one characterized by a low light (turbid) environment and the other by a relatively high light (clear) environment. Additional shading resulted in complete mortality for both shading treatments at the turbid site while the clear site showed a pattern of decreased shoot density and increased photochemical efficiency (Fv/Fm) with increased shading. These contrasting results for the same species in two different locations indicate that acclimation to chronic low light regimes can affect seagrass resilience and highlights the importance of light history in determining the outcome of exposure to further (short-term) stress. Copyright © 2013 Elsevier Ltd. All rights reserved.
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The influence of canopy shading of snow on effective albedo in forested environments
NASA Astrophysics Data System (ADS)
Webster, C.; Jonas, T.
2017-12-01
The overlap of highly reflective snow and absorbent forested areas creates strong heterogeneity in the effective surface albedo compared to forest-free areas. Current errors in calculations of effective forest snow albedo arise due to uncertainties in how models should treat masking of snow by vegetation but improvement of local and large scale models is currently limited by a lack of measurements that demonstrate both spatial and temporal variability over forests. We present above-canopy measurements of winter-time effective forest snow albedo using up- and down-looking radiometers mounted on an octocopter UAV for a total of fifteen flights on eight different days. Ground-view fractions across the flight path were between 0.12 and 0.81. Correlations between effective albedo and both ground-view fraction and canopy height were statistically significant during 14 out of 15 flights, but varied between flights due to solar angle and snow cover. Measured effective albedo across the flight path differed by up to 0.33 during snow-on canopy conditions. A comparison between maximum interception and no interception showed effective albedo varied by up 0.17, which was the same variation between effective albedo during high (46°) and low (23°) solar elevation angles. Temporal and spatial variations in effective albedo caused by canopy shading of the snow surface are therefore as important as temporal variations caused by interception of snow by the canopy. Calculation of effective albedo over forested areas therefore requires careful consideration of canopy height, canopy coverage, solar angle and interception load. The results of this study should be used to inform snow albedo and canopy structure parametrisations in local and larger scale land surface models.
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Estimating Evapotranspiration Of Orange Orchards Using Surface Renewal And Remote Sensing Techniques
NASA Astrophysics Data System (ADS)
Consoli, S.; Russo, A.; Snyder, R.
2006-08-01
Surface renewal (SR) analysis was utilized to calculate sensible heat flux density from high frequency temperature measurements above orange orchard canopies during 2005 in eastern Sicily (Italy). The H values were employed to estimate latent heat flux density (LE) using measured net radiation (Rn) and soil heat flux density (G) in the energy balance (EB) equation. Crop coefficients were determined by calculating the ratio Kc=ETa/ETo, with reference ETo derived from the daily Penman-Monteith equation. The estimated daily Kc values showed an average of about 0.75 for canopy covers having about 70% ground shading and 80% of PAR light interception. Remote sensing estimates of Kc and ET fluxes were compared with those measured by SR-EB. IKONOS satellite estimates of Kc and NDVI were linearly correlated for the orchard stands.
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Song, Liang; Zhang, Yong-Jiang; Chen, Xi; Li, Su; Lu, Hua-Zheng; Wu, Chuan-Sheng; Tan, Zheng-Hong; Liu, Wen-Yao; Shi, Xian-Meng
2015-07-01
Fan life forms are bryophytes with shoots rising from vertical substratum that branch repeatedly in the horizontal plane to form flattened photosynthetic surfaces, which are well suited for intercepting water from moving air. However, detailed water relations, gas exchange characteristics of fan bryophytes and their adaptations to particular microhabitats remain poorly understood. In this study, we measured and analyzed microclimatic data, as well as water release curves, pressure-volume relationships and photosynthetic water and light response curves for three common fan bryophytes in an Asian subtropical montane cloud forest (SMCF). Results demonstrate high relative humidity but low light levels and temperatures in the understory, and a strong effect of fog on water availability for bryophytes in the SMCF. The facts that fan bryophytes in dry air lose most of their free water within 1 h, and a strong dependence of net photosynthesis rates on water content, imply that the transition from a hydrated, photosynthetically active state to a dry, inactive state is rapid. In addition, fan bryophytes developed relatively high cell wall elasticity and the osmoregulatory capacity to tolerate desiccation. These fan bryophytes had low light saturation and compensation point of photosynthesis, indicating shade tolerance. It is likely that fan bryophytes can flourish on tree trunks in the SMCF because of substantial annual precipitation, average relative humidity, and frequent and persistent fog, which can provide continual water sources for them to intercept. Nevertheless, the low water retention capacity and strong dependence of net photosynthesis on water content of fan bryophytes indicate a high risk of unbalanced carbon budget if the frequency and severity of drought increase in the future as predicted.
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Sarlikioti, V; de Visser, P H B; Marcelis, L F M
2011-04-01
At present most process-based models and the majority of three-dimensional models include simplifications of plant architecture that can compromise the accuracy of light interception simulations and, accordingly, canopy photosynthesis. The aim of this paper is to analyse canopy heterogeneity of an explicitly described tomato canopy in relation to temporal dynamics of horizontal and vertical light distribution and photosynthesis under direct- and diffuse-light conditions. Detailed measurements of canopy architecture, light interception and leaf photosynthesis were carried out on a tomato crop. These data were used for the development and calibration of a functional-structural tomato model. The model consisted of an architectural static virtual plant coupled with a nested radiosity model for light calculations and a leaf photosynthesis module. Different scenarios of horizontal and vertical distribution of light interception, incident light and photosynthesis were investigated under diffuse and direct light conditions. Simulated light interception showed a good correspondence to the measured values. Explicitly described leaf angles resulted in higher light interception in the middle of the plant canopy compared with fixed and ellipsoidal leaf-angle distribution models, although the total light interception remained the same. The fraction of light intercepted at a north-south orientation of rows differed from east-west orientation by 10 % on winter and 23 % on summer days. The horizontal distribution of photosynthesis differed significantly between the top, middle and lower canopy layer. Taking into account the vertical variation of leaf photosynthetic parameters in the canopy, led to approx. 8 % increase on simulated canopy photosynthesis. Leaf angles of heterogeneous canopies should be explicitly described as they have a big impact both on light distribution and photosynthesis. Especially, the vertical variation of photosynthesis in canopy is such that the experimental approach of photosynthesis measurements for model parameterization should be revised.
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Sarlikioti, V.; de Visser, P. H. B.; Marcelis, L. F. M.
2011-01-01
Background and Aims At present most process-based models and the majority of three-dimensional models include simplifications of plant architecture that can compromise the accuracy of light interception simulations and, accordingly, canopy photosynthesis. The aim of this paper is to analyse canopy heterogeneity of an explicitly described tomato canopy in relation to temporal dynamics of horizontal and vertical light distribution and photosynthesis under direct- and diffuse-light conditions. Methods Detailed measurements of canopy architecture, light interception and leaf photosynthesis were carried out on a tomato crop. These data were used for the development and calibration of a functional–structural tomato model. The model consisted of an architectural static virtual plant coupled with a nested radiosity model for light calculations and a leaf photosynthesis module. Different scenarios of horizontal and vertical distribution of light interception, incident light and photosynthesis were investigated under diffuse and direct light conditions. Key Results Simulated light interception showed a good correspondence to the measured values. Explicitly described leaf angles resulted in higher light interception in the middle of the plant canopy compared with fixed and ellipsoidal leaf-angle distribution models, although the total light interception remained the same. The fraction of light intercepted at a north–south orientation of rows differed from east–west orientation by 10 % on winter and 23 % on summer days. The horizontal distribution of photosynthesis differed significantly between the top, middle and lower canopy layer. Taking into account the vertical variation of leaf photosynthetic parameters in the canopy, led to approx. 8 % increase on simulated canopy photosynthesis. Conclusions Leaf angles of heterogeneous canopies should be explicitly described as they have a big impact both on light distribution and photosynthesis. Especially, the vertical variation of photosynthesis in canopy is such that the experimental approach of photosynthesis measurements for model parameterization should be revised. PMID:21355008
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Dutilleul, Pierre; Han, Liwen; Valladares, Fernando; Messier, Christian
2015-01-01
Plant light interception and shade tolerance are intrinsically related in that they involve structural, morphological and physiological adaptations to manage light capture for photosynthetic utilization, in order to sustain survival, development and reproduction. At the scale of small-size trees, crown traits related to structural geometry of branching pattern and space occupancy through phyllotaxis can be accurately evaluated in 3D, using computed tomography (CT) scanning data. We demonstrate this by scrutinizing the crowns of 15 potted miniature conifers of different species or varieties, classified in two groups based on leaf type (10 needlelike, 5 scalelike); we also test whether mean values of crown traits measured from CT scanning data and correlations with a shade tolerance index (STI) differ between groups. Seven crown traits, including fractal dimensions (FD1: smaller scales, FD2: larger scales) and leaf areas, were evaluated for all 15 miniature conifers; an average silhouette-to-total-area ratio was also calculated for each of the 10 needlelike-leaf conifers. Between-group differences in mean values are significant (P < 0.05) for STI, FD1, FD2, and the average leaf area displayed (ĀD). Between-group differences in sign and strength of correlations are observed. For example, the correlation between STI and FD1 is negative and significant (P < 0.10) for the needlelike-leaf group, but is positive and significant (P < 0.05) for the miniature conifers with scalelike leaves, which had lower STI and higher FD1 on average in our study; the positive correlation between STI and ĀD is significant (P < 0.05) for the scalelike-leaf group, and very moderate for the needlelike-leaf one. A contrasting physical attachment of the leaves to branches may explain part of the between-group differences. Our findings open new avenues for the understanding of fundamental plant growth processes; the information gained could be included in a multi-scale approach to tree crown modeling.
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Plant Strategies for Enhancing Access to Sunlight.
Fiorucci, Anne-Sophie; Fankhauser, Christian
2017-09-11
Light is a vital resource for plants, which compete for it particularly in dense communities. Plants have multiple photosensory receptors to detect the presence of competitors and thereby adjust their growth and developmental strategies accordingly. Broadly speaking, plants fall into two categories depending on their response to shading by leaves: shade tolerant or shade avoiding. Here, we describe the photoperception mechanisms and the growth responses elicited by the neighboring vegetation in shade-avoiding plants, focusing on Arabidopsis thaliana, where these responses are best understood. The type of response depends on plant density, ranging from neighbor detection modulating growth in anticipation of future shading to the response to canopy shade where light resources are limiting. These diverse environments are sensed by various photoreceptors, and we will describe our current understanding of signal integration triggered by distinct light cues in diverse light conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Ward, Marilyn; Felix, Heather
2012-04-01
The purpose of this study was to assess the efficacy of two different BriteSmile hydrogen peroxide (H2O2) gels in a split-arch protocol for whitening teeth in a clinical setting when used in conjunction with a BriteSmile BS4000 lamp. Fifteen subjects were enrolled into a single-center clinical trial. The efficacy of the BriteSmile BS4000 lamp using both 15% H2O2 and 25% H2O2 gel formulations was tested. Study subjects were concurrently exposed to the whitening lamp with the 15% H2O2 gel placed on half of their anterior teeth and the 25% H2O2 gel on the other half for a total light and gel exposure of 60 minutes. The clinical data collected were shade score, gingival health, and dentinal hypersensitivity self-assessment. Changes in tooth shade were better for subjects exposed to the 25% gel and the dental whitening lamp (average 8.0 shade changes) compared to subjects exposed to the 15% gel and dental whitening lamp (average 7.6 shade changes) immediately after treatment. The same held true at the 7-day follow-up (25% gel average 7.4 shade changes versus 15% gel average 7.3 shade changes). However, these differences were not statistically significant. No reports of irritation of gingival soft tissues were documented. The relative changes in mean sensitivity scores were similar for both groups with no significant differences in mean sensitivity scores between the groups. Both concentrations of H2O2 gel and the whitening lamp combined gave study subjects an average of 8.0 (25% gel) and 7.6 (15% gel) shade changes immediately after treatment. The 7-day follow-up examination resulted in a regression of lightest to an average of 7.4 (25% gel) and 7.3 (15% gel). It was concluded that the use of the chairside whitening light and either 15% or 25% hydrogen peroxide gel is safe and effective for whitening teeth in 1 hour.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Hoffmann, Sabine; Lee, Eleanor
Exterior shades are highly efficient for reducing solar load in commercial buildings. Their impact on net energy use depends on the annual energy balance of heating, cooling, fan and lighting energy. This paper discusses the overall energy use intensity of various external shading systems for a prototypical large office building split into the different types of energy use and for different orientations and window sizes. Lighting energy was calculated for a constant lighting power as well as for dimmed lighting fixtures (daylighting control). In Section 3, slat angles and solar cut-off angles were varied for fixed exterior slat shading systems.more » While the most light-blocking shades performed best for the case without daylighting controls, the optimum cut-off angle with daylighting controls was found to be 30 deg for the office building prototype used in Chicago and Houston. For large window-to-wall (WWR) ratios, window related annual energy use could be reduced by at least 70 % without daylighting control and by a minimum of 86 % with daylighting control in average over all orientations. The occurrence of discomfort glare was is considered in Section 4 of the paper, which looks at the performance of commercially available exterior shading systems when an interior shade is used in addition to the exterior shade during hours when occupants would experience discomfort glare. Glare control impacts overall energy use intensity significantly for exterior shades with high transmittance, especially when daylighting controls are used. In these cases, exterior shades are only beneficial for window-to-wall areas ≥ 45% in the hot Houston climate. For smaller windows and in a heating/cooling climate like Chicago, exterior shades can increase energy consumption« less
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Estimating Canopy Dark Respiration for Crop Models
NASA Technical Reports Server (NTRS)
Monje Mejia, Oscar Alberto
2014-01-01
Crop production is obtained from accurate estimates of daily carbon gain.Canopy gross photosynthesis (Pgross) can be estimated from biochemical models of photosynthesis using sun and shaded leaf portions and the amount of intercepted photosyntheticallyactive radiation (PAR).In turn, canopy daily net carbon gain can be estimated from canopy daily gross photosynthesis when canopy dark respiration (Rd) is known.
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Munguía-Rosas, Miguel A; Parra-Tabla, Victor; Ollerton, Jeff; Cervera, J Carlos
2012-02-01
Mixed reproductive strategies may have evolved as a response of plants to cope with environmental variation. One example of a mixed reproductive strategy is dimorphic cleistogamy, where a single plant produces closed, obligately self-pollinated (CL) flowers and open, potentially outcrossed (CH) flowers. Frequently, optimal environmental conditions favour production of more costly CH structures whilst economical and reliable CL structures are produced under less favourable conditions. In this study we explore (1) the effect of light and water on the reproductive phenology and (2) the effect of pollen supplementation on resource allocation to seeds in the cleistogamous weed Ruellia nudiflora. Split-plot field experiments were carried out to assess the effect of shade (two levels: ambient light vs. a reduction of 50 %) and watering (two levels: non-watered vs. watered) on the onset, end and duration of the production of three reproductive structures: CH flowers, CH fruit and CL fruit. We also looked at the effect of these environmental factors on biomass allocation to seeds (seed weight) from obligately self-pollinated flowers (CL), open-pollinated CH flowers and pollen-supplemented CH flowers. CH structures were produced for a briefer period and ended earlier under shaded conditions. These conditions also resulted in an earlier production of CL fruit. Shaded conditions also produced greater biomass allocation to CH seeds receiving extra pollen. Sub-optimal (shaded) conditions resulted in a briefer production period of CH structures whilst these same conditions resulted in an earlier production of CL structures. However, under sub-optimal conditions, plants also allocated more resources to seeds sired from CH flowers receiving large pollen loads. Earlier production of reproductive structures and relatively larger seed might improve subsequent success of CL and pollen-supplemented CH seeds, respectively.
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Chitrarsu, Vijai Krishnan; Chidambaranathan, Ahila Singaravel; Balasubramaniam, Muthukumar
2017-10-31
To evaluate the shade matching capabilities in natural dentitions using Vita Toothguide 3D-Master and an intraoral digital spectrophotometer (Vita Easyshade Advance 4.0) in various light sources. Participants between 20 and 40 years old with natural, unrestored right maxillary central incisors, no history of bleaching, orthodontic treatment, or malocclusion and no rotations were included. According to their shades, subjects were randomly selected and grouped into A1, A2, and A3. A total of 100 participants (50 male and 50 female) in each group were chosen for this study. Shade selection was made between 10 am and 2 pm for all light sources. The same examiner selected the shade of natural teeth with Vita Toothguide 3D-Master under natural light within 2 minutes. Once the Vita Toothguide 3D-Masterwas matched with the maxillary right central incisor, the L*, a*, and b* values, chroma, and hue were recorded with Vita Easyshade Advance 4.0 by placing it on the shade tab under the same light source. The values were statistically analyzed using one-way ANOVA and Tukey's HSD post hoc test with SPSS v22.0 software. The mean ∆E* ab values for shades A1, A2, and A3 for groups 1, 2, and 3 were statistically significantly different from each other (p < 0.001). The intraoral digital spectrophotometer showed statistically significant differences in shade matching compared to Vita Toothguide 3D-Master. Incandescent light showed more accurate shade matching than the filtered LED, LED, and daylight. © 2017 by the American College of Prosthodontists.
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NASA Astrophysics Data System (ADS)
Kvale, Karin F.; Meissner, Katrin J.
2017-10-01
Treatment of the underwater light field in ocean biogeochemical models has been attracting increasing interest, with some models moving towards more complex parameterisations. We conduct a simple sensitivity study of a typical, highly simplified parameterisation. In our study, we vary the phytoplankton light attenuation parameter over a range constrained by data during both pre-industrial equilibrated and future climate scenario RCP8.5. In equilibrium, lower light attenuation parameters (weaker self-shading) shift net primary production (NPP) towards the high latitudes, while higher values of light attenuation (stronger shelf-shading) shift NPP towards the low latitudes. Climate forcing magnifies this relationship through changes in the distribution of nutrients both within and between ocean regions. Where and how NPP responds to climate forcing can determine the magnitude and sign of global NPP trends in this high CO2 future scenario. Ocean oxygen is particularly sensitive to parameter choice. Under higher CO2 concentrations, two simulations establish a strong biogeochemical feedback between the Southern Ocean and low-latitude Pacific that highlights the potential for regional teleconnection. Our simulations serve as a reminder that shifts in fundamental properties (e.g. light attenuation by phytoplankton) over deep time have the potential to alter global biogeochemistry.
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NASA Astrophysics Data System (ADS)
Harpold, A. A.; Brooks, P. D.; Biederman, J. A.; Swetnam, T.
2011-12-01
Difficulty estimating snowpack variability across complex forested terrain currently hinders the prediction of water resources in the semi-arid Southwestern U.S. Catchment-scale estimates of snowpack variability are necessary for addressing ecological, hydrological, and water resources issues, but are often interpolated from a small number of point-scale observations. In this study, we used LiDAR-derived distributed datasets to investigate how elevation, aspect, topography, and vegetation interact to control catchment-scale snowpack variability. The study area is the Redondo massif in the Valles Caldera National Preserve, NM, a resurgent dome that varies from 2500 to 3430 m and drains from all aspects. Mean LiDAR-derived snow depths from four catchments (2.2 to 3.4 km^2) draining different aspects of the Redondo massif varied by 30%, despite similar mean elevations and mixed conifer forest cover. To better quantify this variability in snow depths we performed a multiple linear regression (MLR) at a 7.3 by 7.3 km study area (5 x 106 snow depth measurements) comprising the four catchments. The MLR showed that elevation explained 45% of the variability in snow depths across the study area, aspect explained 18% (dominated by N-S aspect), and vegetation 2% (canopy density and height). This linear relationship was not transferable to the catchment-scale however, where additional MLR analyses showed the influence of aspect and elevation differed between the catchments. The strong influence of North-South aspect in most catchments indicated that the solar radiation is an important control on snow depth variability. To explore the role of solar radiation, a model was used to generate winter solar forcing index (SFI) values based on the local and remote topography. The SFI was able to explain a large amount of snow depth variability in areas with similar elevation and aspect. Finally, the SFI was modified to include the effects of shading from vegetation (in and out of canopy), which further explained snow depth variability. The importance of SFI for explaining catchment-scale snow depth variability demonstrates that aspect is not a sufficient metric for direct radiation in complex terrain where slope and remote topographic shading are significant. Surprisingly, the net effects of interception and shading by vegetation on snow depths were minimal compared to elevation and aspect in these catchments. These results suggest that snowpack losses from interception may be balanced by increased shading to reduce the overall impacts from vegetation compared to topographic factors in this high radiation environment. Our analysis indicated that elevation and solar radiation are likely to control snow variability in larger catchments, with interception and shading from vegetation becoming more important at smaller scales.
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Light exclusion influence on grape anthocyanin
USDA-ARS?s Scientific Manuscript database
This study contrasted the anthocyanins of investigational grape clusters that developed without light incidence (light-excluded), to those of control clusters that were shaded naturally beneath the vine canopy (control-shaded). Treatment grape clusters were light-excluded during ripening by opaque w...
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[The fabrication and chroma study of a kind of custom shade guide with metal substrate].
Chen, Ling; Liu, Xian; Xu, Li-qiang; Chao, Yong-lie; Liu, Wen-fang; Chen, Xiao-fang
2007-06-01
This study was to explore the chroma of a custom shade guide with metal substrate. A custom shade guide sample was fabricated using the central maxillary incisor as a model,which was corresponding to the colour of VITAPAN shade guide.The colour of each shade tab was measured with PR-650 spectrophotometer when every porcelain was added. From the opaque to glaze, the lightness was decreased and the chroma was increased distinctively; When the body porcelain were baked over their corresponding opaque, the lightness was decreased and the chroma was increased; When the enamel porcelain and the translucent porcelain were added on, the lightness and chroma were decreased slightly; the glaze could increase the lightness. The "add on" porcelain can affect the final color of the restoration, and the effects of each porcelain layer were different from each other.
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Reducing shade avoidance responses in a cereal crop
Wille, Wibke; Pipper, Christian B; Rosenqvist, Eva; Andersen, Sven B
2017-01-01
Abstract Several researchers have hypothesized that shade avoidance behaviour is favoured by natural selection because it increases the fitness of individuals. Shade avoidance can be disadvantageous for crops, however, because it reduces allocation of resources to reproductive yield, increases the risk of lodging and reduces weed suppression. One approach to develop varieties with reduced shade avoidance and enhanced agronomic performance is by inducing mutations followed by phenotypic screening. We treated spring wheat seeds with ethyl methanesulfonate and screened the seedlings repeatedly under green filters for plants showing reduced elongation of the first leaf sheath and second leaf lamina. The shade avoidance responses of five promising mutant lines were further compared to non-mutated plants in a climate chamber experiment with added far-red light. Two of the selected lines displayed significantly reduced elongation under all light treatments while two lines showed reduced elongation only in added far-red light. The most promising mutant line did not differ in height from the non-mutated cultivar in neutral light, but elongated 20.6% less in strong far-red light. This traditional forward approach of screening mutagenized spring wheat produced plants with reduced shade avoidance responses. These mutants may generate new molecular handles to modify the reaction of plants to changes in light spectral distribution in traditional and novel cultivation systems. PMID:29071064
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Shading decreases the abundance of the herbivorous California horn snail, Cerithidea californica
Lorda, Julio; Lafferty, Kevin D.
2012-01-01
Most of the intertidal zone in estuaries of California, USA and Baja California, Mexico is covered with vascular vegetation. Shading by these vascular plants influences abiotic and biotic processes that shape benthic community assemblages. We present data on the effects of shading on the California horn snail, Cerithidea californica. This species is important because it is the most common benthic macrofaunal species in these systems and acts as an obligate intermediate host of several species of rematode parasites that infect several other species. Using observational and experimental studies, we found a negative effect of shade on the distribution and abundance of the California horn snail. We hypothesized that shading reduces the abundance of the epipelic diatoms that the snails feeds on, causing snails to leave haded areas. We observed a negative relationship between vascular plant cover, sub-canopy light levels, and snail density in Mugu Lagoon. Then we experimentally manipulated light regimes, by clipping vegetation and adding shade structures, and found higher snail densities at higher light levels. In Goleta Slough, we isolated the effect of shade from vegetation by documenting a negative relationship between the shade created by two bridges and diatom and snail densities. We also found that snails moved the greatest distances over shaded channel banks compared to unshaded channel banks. Further, we documented the effect of water depth and channel bank orientation on shading in this system. An additional effect of shading is the reduction of temperature, providing an alternative explanation for some of our results. These results broaden our knowledge of how variation in the light environment influences the ecology of estuarine ecosystems.
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Characterizing visual asymmetries in contrast perception using shaded stimuli.
Chacón, José; Castellanos, Miguel Ángel; Serrano-Pedraza, Ignacio
2015-01-01
Previous research has shown a visual asymmetry in shaded stimuli where the perceived contrast depended on the polarity of their dark and light areas (Chacón, 2004). In particular, circles filled out with a top-dark luminance ramp were perceived with higher contrast than top-light ones although both types of stimuli had the same physical contrast. Here, using shaded stimuli, we conducted four experiments in order to find out if the perceived contrast depends on: (a) the contrast level, (b) the type of shading (continuous vs. discrete) and its degree of perceived three-dimensionality, (c) the orientation of the shading, and (d) the sign of the perceived contrast alterations. In all experiments the observers' tasks were to equate the perceived contrast of two sets of elements (usually shaded with opposite luminance polarity), in order to determine the subjective equality point. Results showed that (a) there is a strong difference in perceived contrast between circles filled out with luminance ramp top-dark and top-light that is similar for different contrast levels; (b) we also found asymmetries in contrast perception with different shaded stimuli, and this asymmetry was not related with the perceived three-dimensionality but with the type of shading, being greater for continuous-shading stimuli; (c) differences in perceived contrast varied with stimulus orientation, showing the maximum difference on vertical axis with a left bias consistent with the bias found in previous studies that used visual-search tasks; and (d) asymmetries are consistent with an attenuation in perceived contrast that is selective for top-light vertically-shaded stimuli.
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Lightness, chroma and hue differences on visual shade matching.
Pecho, Oscar E; Pérez, María M; Ghinea, Razvan; Della Bona, Alvaro
2016-11-01
To analyze the influence of lightness, chroma and hue differences on visual shade matching performed by dental students. 100 dental students (DS) volunteers with normal vision participated in the study. A spectroradiometer (SP) was used to measure the spectral reflectance of 4 extracted human upper central incisors (UCI 1-4) and shade tabs from Vita Classical (VC) and Vita Toothguide 3D-Master (3D) shade guides. Measurements were performed over a gray background, inside a viewing booth and under D65 illuminant (diffuse/0° geometry). Color parameters (L*, a*, b*, C* and h°) were calculated. DS used VC and 3D to visually select the best shade match for each UCI. CIE metric differences (Δa * ,Δb * ,ΔL ' , ΔC ' and ΔH ' ) and CIEDE2000(2:1:1) lightness (ΔE L ), chroma (ΔE C ) and hue (ΔE H ) differences were obtained from each UCI and the first three shades selected by DS and the first option using CIELAB, CIEDE2000(1:1:1) and CIEDE2000(2:1:1) color difference metrics. The closest CIELAB color-discrimination ellipsoid (from RIT-DuPont visual color-difference data) to each UCI was selected for the analysis of visual shade matching. DS showed a preference for shades with lower chroma (ΔC ' and ΔE C ) and/or hue (ΔH ' and ΔE H ) values instead of shades with lower lightness values (ΔL ' and ΔE L ). Most best visual matches were near the tolerance ellipsoid centered on tooth shade. This study is an attempt to partially explain the inconsistencies between visual and instrumental shade matching and the limitations of shade guides. Visual shade matching was driven by color differences with lower chroma and hue values. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
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Evaluating shading bias in malaise and intercept traps
Irvine, Kathryn M.; Woods, Stephen A.
2007-01-01
Foresters are increasingly focusing on landscape level management regimes. At the landscape level, managed acreage may differ substantially in structure and micro-climatic conditions. Trapping is a commonly used method to evaluate changes in insect communities across landscapes. Among those trapping techniques, Malaise and window-pane traps are conveniently deployed to collect large numbers of insects for relative estimates of density. However, the catch within traps may be affected by a wide range of environmental variables including trap location, height, and factors such as exposure to sunlight and temperature. Seven experiments were conducted from 1996 through 2000 to evaluate the effects of shading on trap catch of a variety of Malaise trap designs and one window-pane trap design. Overall, differences in shading effects on trap catch were detected across different traps and taxa and suggested that, in general, more insects are collected in traps that were in direct sunlight. The effect of shading varied from a reduction in trap catch of 10 % to an increase of 7%, the results depended on trap color. Diptera, Coleoptera, and Homoptera were most likely to exhibit this bias. In contrast, trap catch of the Hymenoptera was the most variable and appeared to be sensitive to factors that might interact with sun/shade conditions
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Lasso, Eloisa; Engelbrecht, Bettina M J; Dalling, James W
2009-08-01
In moist tropical forests resprouting may be an important component of life history, contributing to asexual reproduction through the clonal spread of individuals derived from shoot fragments. However, in contrast to other ecosystems where resprouting is common, the ecological correlates of resprouting capacity in tropical forests remain largely unexplored. In this study we characterized shade tolerance, resprouting capacity and sexual reproductive success of eight co-occurring Piper species from lowland forests of Panama. In field experiments we found that shade-tolerant Piper species had a higher capacity to regenerate from excised or pinned stem fragments than light-demanding species in both gap and understory light conditions. In contrast, shade-tolerant species had lower recruitment probabilities from seeds, as a consequence of lower initial seed viability, and lower seedling emergence rates. All Piper species needed gap conditions for successful seedling establishment. Of 8,000 seeds sown in the understory only 0.2% emerged. In gaps, seed germination of light-demanding species was between 10 and 50%, whereas for shade-tolerant species it was 0.5-9.8%. We propose that the capacity to reproduce asexually from resprouts could be adaptive for shade-tolerant species that are constantly exposed to damage from falling litter in the understory. Resprouting may allow Piper populations to persist and spread despite the high rate of pre-dispersal seed predation and low seed emergence rates. Across Piper species, we detected a trade-off between resprouting capacity and the annual viable seed production per plant but not with annual seed mass produced per plant. This suggests that species differences in sexual reproductive success may not necessarily result from differential resource allocation. Instead we suggest that low sexual reproductive success in the understory may in part reflect reduced genetic diversity in populations undergoing clonal growth, resulting in self-fertilization and in-breeding depression.
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Stoepler, Teresa M; Lill, John T
2013-10-01
A variety of ecological factors influence host use by parasitoids, including both abiotic and biotic factors. Light environment is one important abiotic parameter that differs among habitats and influences a suite of plant nutritional and resistance traits that in turn affect herbivore performance. However, the extent to which these bottom-up effects "cascade up" to affect higher trophic levels and the relative importance of direct and indirect effects of sunlight on tritrophic interactions are unclear. The objective of this study was to test how light environment (light gap vs. shaded forest understory) and leaf type (sun vs. shade leaves) affect the performance and incidence of parasitism of two species of moth larvae, Euclea delphinii and Acharia stimulea (Limacodidae). We manipulated the leaf phenotype of potted white oak saplings by growing them in either full sun or full shade throughout leaf expansion to produce sun and shade leaves, respectively. These saplings were then placed in light gap and adjacent shaded understory habitats in the forest in a full-factorial design, and stocked with sentinel larvae that were exposed to parasitism ("exposed" experiments). We reared additional larvae in sleeve cages (protected from parasitism) to isolate light environment and leaf phenotype treatment effects on larval performance in the absence of enemies ("bagged" experiments). In the exposed experiments, light environment strongly affected the likelihood of parasitism, while leaf phenotype did not. Euclea delphinii larvae were up to 6.6 times more likely to be parasitized in light gaps than in shaded understory habitats. This pattern was consistent for both tachinid fly and wasp parasitoids across two separate experiments. However, the larval performance of both species in the bagged experiments was maximized in the shade-habitat/sun-leaf treatment, a habitat/leaf-type combination that occurs infrequently in nature. Taken together, our results suggest that the direct effects of light environment on the incidence of parasitism supersede any indirect effects resulting from altered leaf quality and reveal inherent ecological trade-offs for herbivores confronted with choosing between sunny (high leaf quality, harsh environment, high parasitism) and shaded (reduced leaf quality less harsh environment, reduced parasitism) habitats.
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Charbonnier, Fabien; Roupsard, Olivier; le Maire, Guerric; Guillemot, Joannès; Casanoves, Fernando; Lacointe, André; Vaast, Philippe; Allinne, Clémentine; Audebert, Louise; Cambou, Aurélie; Clément-Vidal, Anne; Defrenet, Elsa; Duursma, Remko A; Jarri, Laura; Jourdan, Christophe; Khac, Emmanuelle; Leandro, Patricia; Medlyn, Belinda E; Saint-André, Laurent; Thaler, Philippe; Van Den Meersche, Karel; Barquero Aguilar, Alejandra; Lehner, Peter; Dreyer, Erwin
2017-08-01
In agroforestry systems, shade trees strongly affect the physiology of the undergrown crop. However, a major paradigm is that the reduction in absorbed photosynthetically active radiation is, to a certain extent, compensated by an increase in light-use efficiency, thereby reducing the difference in net primary productivity between shaded and non-shaded plants. Due to the large spatial heterogeneity in agroforestry systems and the lack of appropriate tools, the combined effects of such variables have seldom been analysed, even though they may help understand physiological processes underlying yield dynamics. In this study, we monitored net primary productivity, during two years, on scales ranging from individual coffee plants to the entire plot. Absorbed radiation was mapped with a 3D model (MAESPA). Light-use efficiency and net assimilation rate were derived for each coffee plant individually. We found that although irradiance was reduced by 60% below crowns of shade trees, coffee light-use efficiency increased by 50%, leaving net primary productivity fairly stable across all shade levels. Variability of aboveground net primary productivity of coffee plants was caused primarily by the age of the plants and by intraspecific competition among them (drivers usually overlooked in the agroforestry literature) rather than by the presence of shade trees. © 2017 John Wiley & Sons Ltd.
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Alméras, Tancrède; Derycke, Morgane; Jaouen, Gaëlle; Beauchêne, Jacques; Fournier, Mériem
2009-01-01
Gravitropism is necessary for plants to control the orientation of their axes while they grow in height. In woody plants, stem re-orientations are costly because they are achieved through diameter growth. The functional diversity of gravitropism was studied to check if the mechanisms involved and their efficiency may contribute to the differentiation of height growth strategies between forest tree species at the seedling stage. Seedlings of eight tropical species were grown tilted in a greenhouse, and their up-righting movement and diameter growth were measured over three months. Morphological, anatomical, and biomechanical traits were measured at the end of the survey. Curvature analysis was used to analyse the up-righting response along the stems. Variations in stem curvature depend on diameter growth, size effects, the increase in self-weight, and the efficiency of the gravitropic reaction. A biomechanical model was used to separate these contributions. Results showed that (i) gravitropic movements were based on a common mechanism associated to similar dynamic patterns, (ii) clear differences in efficiency (defined as the change in curvature achieved during an elementary diameter increment for a given stem diameter) existed between species, (iii) the equilibrium angle of the stem and the anatomical characters associated with the efficiency of the reaction also differed between species, and (iv) the differences in gravitropic reaction were related to the light requirements: heliophilic species, compared to more shade-tolerant species, had a larger efficiency and an equilibrium angle closer to vertical. This suggests that traits determining the gravitropic reaction are related to the strategy of light interception and may contribute to the differentiation of ecological strategies promoting the maintenance of biodiversity in tropical rainforests.
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Light-Induced Indeterminacy Alters Shade-Avoiding Tomato Leaf Morphology1[OPEN
Chitwood, Daniel H.; Kumar, Ravi; Ranjan, Aashish; Pelletier, Julie M.; Townsley, Brad T.; Ichihashi, Yasunori; Martinez, Ciera C.; Zumstein, Kristina; Harada, John J.; Maloof, Julin N.; Sinha, Neelima R.
2015-01-01
Plants sense the foliar shade of competitors and alter their developmental programs through the shade-avoidance response. Internode and petiole elongation, and changes in overall leaf area and leaf mass per area, are the stereotypical architectural responses to foliar shade in the shoot. However, changes in leaf shape and complexity in response to shade remain incompletely, and qualitatively, described. Using a meta-analysis of more than 18,000 previously published leaflet outlines, we demonstrate that shade avoidance alters leaf shape in domesticated tomato (Solanum lycopersicum) and wild relatives. The effects of shade avoidance on leaf shape are subtle with respect to individual traits but are combinatorially strong. We then seek to describe the developmental origins of shade-induced changes in leaf shape by swapping plants between light treatments. Leaf size is light responsive late into development, but patterning events, such as stomatal index, are irrevocably specified earlier. Observing that shade induces increases in shoot apical meristem size, we then describe gene expression changes in early leaf primordia and the meristem using laser microdissection. We find that in leaf primordia, shade avoidance is not mediated through canonical pathways described in mature organs but rather through the expression of KNOTTED1-LIKE HOMEOBOX and other indeterminacy genes, altering known developmental pathways responsible for patterning leaf shape. We also demonstrate that shade-induced changes in leaf primordium gene expression largely do not overlap with those found in successively initiated leaf primordia, providing evidence against classic hypotheses that shaded leaf morphology results from the prolonged production of juvenile leaf types. PMID:26381315
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Gommers, Charlotte M M; Keuskamp, Diederik H; Buti, Sara; van Veen, Hans; Koevoets, Iko T; Reinen, Emilie; Voesenek, Laurentius A C J; Pierik, Ronald
2017-02-01
Plants growing at high densities elongate their shoots to reach for light, a response known as the shade avoidance syndrome (SAS). Phytochrome-mediated detection of far-red light reflection from neighboring plants activates growth-promoting molecular pathways leading to SAS However, it is unknown how plants that complete their life cycle in the forest understory and are shade tolerant prevent SAS when exposed to shade. Here, we show how two wild Geranium species from different native light environments regulate contrasting responses to light quality cues. A comparative RNA sequencing approach unveiled the molecular underpinnings of their contrasting growth responses to far-red light enrichment. It also identified differential phytochrome control of plant immunity genes and confirmed that far-red enrichment indeed contrastingly affects resistance against Botrytis cinerea between the two species. Furthermore, we identify a number of candidate regulators of differential shade avoidance. Three of these, the receptor-like kinases FERONIA and THESEUS1 and the non-DNA binding bHLH protein KIDARI, are functionally validated in Arabidopsis thaliana through gene knockout and/or overexpression studies. We propose that these components may be associated with either showing or not showing shade avoidance responses. © 2017 American Society of Plant Biologists. All rights reserved.
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Study on Light Interception and Biomass Production of Different Cotton Cultivars
Mao, Shuchun; Han, Yingchun; Feng, Lu; Wang, Guoping; Yang, Beifang; Zhi, Xiaoyu; Fan, Zhengyi; Lei, Yaping; Du, Wenli; Li, Yabing
2016-01-01
Identifying the characteristics of light interception and utilization is of great significance for improving the potential photosynthetic activity of plants. The present research investigates the differences in absorbing and converting photosynthetically active radiation (PAR) among various cotton cultivars. Field experiments were conducted in 2012, 2013 and 2014 in Anyang, Henan, China. Ten cultivars with different maturity and plant architectures were planted at a density of 60,000 plants ha-1 in randomized blocks, with three replicates. The spatial distribution of light in canopy was measured and quantified with a geo-statistical method, according to which the cumulative amount of intercepted radiation was calculated by Simpson 3/8 rules. Finally, light interception was analyzed in association with the biomass accumulation of different cultivars. The key results were: (1) late-maturing varieties with an incompact plant architecture captured more solar radiation throughout the whole growth period than middle varieties with columnar architecture and even more than early varieties with compact architecture, and they produced more biomass; (2) the highest PAR interception ratio and the maximum biomass accumulation rate occurred during the blossoming and boll-forming stage, when leaf area index (LAI) reached its peak; (3) the distribution within the canopy presented a significant spatial heterogeneity, and at late growing stage, the PAR was mainly intercepted by upper canopies in incompact-type plant communities, but was more homogeneous in columnar-type plants; however, the majority of radiation was transmitted through the canopy in compact-type colonies; (4) there was not a consistent variation relationship between the cumulative intercepted PAR (iPAR) and biomass among these cultivars over the three years of the study. Based on these results, we attempted to clarify the distinction in light spatial distribution within different canopies and the patterns of PAR interception in diverse cotton cultivars with different hereditary characters, thereby providing a significant basis for researchers to select cultivars with appropriate growth period and optimal plant architecture for improvement of light interception and utilization. PMID:27227675
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Validity of a Sun Safety Diary Using UV Monitors in Middle School Children
ERIC Educational Resources Information Center
Yaroch, Amy L.; Reynolds, Kim D.; Buller, David B.; Maloy, Julie A.; Geno, Cristy R.
2006-01-01
This article describes a validity study conducted among middle school students comparing self-reported sun safety behaviors from a diary with readings from ultraviolet (UV) monitors worn on different body sites. The UV monitors are stickers with panels that turn increasingly darker shades of blue in the presence of increasing amounts of UV light.…
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Optical and color stabilities of paint-on resins for shade modification of restorative resins.
Arikawa, Hiroyuki; Kanie, Takahito; Fujii, Koichi; Ban, Seiji; Homma, Tetsuya; Takahashi, Hideo
2004-06-01
The purpose of this study was to examine the optical and color stabilities of the paint-on resin used for shade modification of restorative resins. Three shades of paint-on resin and two crown and bridge resins were used. The light transmittance characteristics of the materials during accelerated aging tests such as water immersion, toothbrush abrasion, ultraviolet (UV) light irradiation, and staining tests were measured. Discolorations of materials resulting from tests were also determined. There were no significant effects of water immersion, toothbrush abrasion and UV light irradiation on the light transmittance and visible color change of paint-on resins, whereas the staining tests significantly decreased the light transmittance and increased color change of the translucent shades of materials. Our results indicate that the paint-on resins exhibit stable optical properties and color appearance, which are at least as good as the crown and bridge resins.
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Ma, Lifeng; Yi, Xiaoyun; Ruan, Jianyun
2014-01-01
To investigate the effect of light intensity and temperature on the biosynthesis and accumulation of quality-related metabolites, field grown tea plants were shaded by Black Net and Nano-insulating Film (with additional 2–4°C cooling effect) with un-shaded plants as a control. Young shoots were subjected to UPLC-Q-TOF MS followed by multivariate statistical analysis. Most flavonoid metabolites (mainly flavan-3-ols, flavonols and their glycosides) decreased significantly in the shading treatments, while the contents of chlorophyll, β-carotene, neoxanthin and free amino acids, caffeine, benzoic acid derivatives and phenylpropanoids increased. Comparison between two shading treatments indicated that the lower temperature under Nano shading decreased flavonols and their glycosides but increased accumulation of flavan-3-ols and proanthocyanidins. The comparison also showed a greater effect of temperature on galloylation of catechins than light intensity. Taken together, there might be competition for substrates between the up- and down-stream branches of the phenylpropanoid/flavonoid pathway, which was influenced by light intensity and temperature. PMID:25390340
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Zhang, Qunfeng; Shi, Yuanzhi; Ma, Lifeng; Yi, Xiaoyun; Ruan, Jianyun
2014-01-01
To investigate the effect of light intensity and temperature on the biosynthesis and accumulation of quality-related metabolites, field grown tea plants were shaded by Black Net and Nano-insulating Film (with additional 2-4°C cooling effect) with un-shaded plants as a control. Young shoots were subjected to UPLC-Q-TOF MS followed by multivariate statistical analysis. Most flavonoid metabolites (mainly flavan-3-ols, flavonols and their glycosides) decreased significantly in the shading treatments, while the contents of chlorophyll, β-carotene, neoxanthin and free amino acids, caffeine, benzoic acid derivatives and phenylpropanoids increased. Comparison between two shading treatments indicated that the lower temperature under Nano shading decreased flavonols and their glycosides but increased accumulation of flavan-3-ols and proanthocyanidins. The comparison also showed a greater effect of temperature on galloylation of catechins than light intensity. Taken together, there might be competition for substrates between the up- and down-stream branches of the phenylpropanoid/flavonoid pathway, which was influenced by light intensity and temperature.
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VALLADARES, FERNANDO; HERNÁNDEZ, LIBERTAD G.; DOBARRO, IKER; GARCÍA‐PÉREZ, CRISTINA; SANZ, RUBÉN; PUGNAIRE, FRANCISCO I.
2003-01-01
Different plant species and organs within a plant differ in their plastic response to light. These responses influence their performance and survival in relation to the light environment, which may range from full sunlight to deep shade. Plasticity, especially with regard to physiological features, is linked to a greater capacity to exploit high light and is usually low in shade‐tolerant species. Among photosynthetic organs, green stems, which represent a large fraction of the total photosynthetic area of certain species, are hypothesized to be less capable of adjustment to light than leaves, because of biomechanical and hydraulic constraints. The response to light by leaves and stems of six species of leguminous, green‐stemmed shrubs from dry and high‐light environments was studied by growing seedlings in three light environments: deep shade, moderate shade and sun (3, 30 and 100 % of full sunlight, respectively). Survival in deep shade ranged from 2 % in Retama sphaerocarpa to 74 % in Ulex europaeus. Survival was maximal at moderate shade in all species, ranging from 80 to 98 %. The six species differed significantly in their ratio of leaf to total photosynthetic area, which influenced their light response. Survival in deep shade increased significantly with increasing ratio of leaf to total photosynthetic area, and decreased with increasing plasticity in net photosynthesis and dark respiration. Responses to light differed between stems and leaves within each species. Mean phenotypic plasticity for the variables leaf or stem specific mass, chlorophyll content, chlorophyll a/b ratio, and carotenoid to chlorophyll ratio of leaves, was inversely related to that of stems. Although mean plasticity of stems increased with the ratio of leaf to total photosynthetic area, the mean plasticity of leaves decreased. Shrubs with green stems and a low ratio of leaf to total photosynthetic area are expected to be restricted to well‐lit habitats, at least during the seedling stage, owing to their inefficient light capture and the low plasticity of their stems. PMID:12646502
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Lilles, Erica B; Astrup, Rasmus; Lefrançois, Marie-Lou; David Coates, K
2014-12-01
We developed models to describe the responses of four commonly examined leaf traits (mass per area, weight, area and nitrogen (N) concentration) to gradients of light, soil nutrients and tree height in three conifer species of contrasting shade tolerance. Our observational dataset from the sub-boreal spruce forests of British Columbia included subalpine fir (Abies lasioscarpa [Hook.] Nutt; high shade tolerance), interior spruce (Picea glauca × Picea engelmannii [Moench] Voss; intermediate shade tolerance) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia; low shade tolerance) saplings from 0.18 to 4.87 m tall, in 8-98% of total incident light, from field sites with <17.6 kg ha(-1) to >46.8 kg ha(-1) total dissolved N. Leaf weights and areas showed strong positive responses to light and height, but little or no response to soil nutrients. Parameter estimates indicated that the shape of leaf weight and area responses to light corresponded with shade tolerance ranking for the three species; pine had the most linear response whereas spruce and fir had asymptotic responses. Leaf N concentration responded positively to soil nutrients, negatively to light and idiosyncratically to height. The negative effect of light was only apparent on sites of high soil nutrient availability, and parameter estimates for the shape of the negative response also corresponded to shade tolerance ranking (apine = -0.79, aspruce = -0.15, afir = -0.07). Of the traits we measured, leaf mass per area showed the least response to light, soil nutrient and height gradients. Although it is a common practice in comparisons across many species, characterizing these conifers by mean values of their leaf traits would miss important intraspecific variation across environmental and size gradients. In these forests, parameter estimates representing the intraspecific variability of leaf trait responses can be used to understand relative shade tolerances. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Song, Yu; Jiang, Chengyao; Gao, Lihong
2016-01-01
Light insufficient stress caused by canopy interception and mutual shading is a major factor limiting plant growth and development in intensive crop cultivation. Supplemental lighting can be used to give light to the lower canopy leaves and is considered to be an effective method to cope with low irradiation stress. Leaf photosynthesis, stomatal regulation, and plant growth and development of young tomato plants were examined to estimate the effects of supplemental lighting with various composite spectra and different light orientations. Light-emitting diodes (LEDs) of polychromatic light quality, red + blue (R/B), white + red + blue (W/R/B), white + red + far-red (W/R/FR), and white + blue (W/B) were assembled from the underneath canopy or from the inner canopy as supplemental lighting resources. The results showed that the use of supplemental lighting significantly increased the photosynthetic efficiency, and reduced stomatal closure while promoting plant growth. Among all supplemental lighting treatments, the W/R/B and W/B from the underneath canopy had best performance. The different photosynthetic performances among the supplemental lighting treatments are resulted from variations in CO2 utilization. The enhanced blue light fraction in the W/R/B and W/B could better stimulate stomatal opening and promote photosynthetic electron transport activity, thus better improving photosynthetic rate. Compared with the inner canopy treatment, the supplemental lighting from the underneath canopy could better enhance the carbon dioxide assimilation efficiency and excessive energy dissipation, leading to an improved photosynthetic performance. Stomatal morphology was highly correlated to leaf photosynthesis and plant development, and should thus be an important determinant for the photosynthesis and the growth of greenhouse tomatoes. PMID:28018376
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Munguía-Rosas, Miguel A.; Parra-Tabla, Victor; Ollerton, Jeff; Cervera, J. Carlos
2012-01-01
• Background and Aims Mixed reproductive strategies may have evolved as a response of plants to cope with environmental variation. One example of a mixed reproductive strategy is dimorphic cleistogamy, where a single plant produces closed, obligately self-pollinated (CL) flowers and open, potentially outcrossed (CH) flowers. Frequently, optimal environmental conditions favour production of more costly CH structures whilst economical and reliable CL structures are produced under less favourable conditions. In this study we explore (1) the effect of light and water on the reproductive phenology and (2) the effect of pollen supplementation on resource allocation to seeds in the cleistogamous weed Ruellia nudiflora. • Methods Split-plot field experiments were carried out to assess the effect of shade (two levels: ambient light vs. a reduction of 50 %) and watering (two levels: non-watered vs. watered) on the onset, end and duration of the production of three reproductive structures: CH flowers, CH fruit and CL fruit. We also looked at the effect of these environmental factors on biomass allocation to seeds (seed weight) from obligately self-pollinated flowers (CL), open-pollinated CH flowers and pollen-supplemented CH flowers. • Key Results CH structures were produced for a briefer period and ended earlier under shaded conditions. These conditions also resulted in an earlier production of CL fruit. Shaded conditions also produced greater biomass allocation to CH seeds receiving extra pollen. • Conclusions Sub-optimal (shaded) conditions resulted in a briefer production period of CH structures whilst these same conditions resulted in an earlier production of CL structures. However, under sub-optimal conditions, plants also allocated more resources to seeds sired from CH flowers receiving large pollen loads. Earlier production of reproductive structures and relatively larger seed might improve subsequent success of CL and pollen-supplemented CH seeds, respectively. PMID:22095920
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Cabrera-Bosquet, Llorenç; Fournier, Christian; Brichet, Nicolas; Welcker, Claude; Suard, Benoît; Tardieu, François
2016-10-01
Light interception and radiation-use efficiency (RUE) are essential components of plant performance. Their genetic dissections require novel high-throughput phenotyping methods. We have developed a suite of methods to evaluate the spatial distribution of incident light, as experienced by hundreds of plants in a glasshouse, by simulating sunbeam trajectories through glasshouse structures every day of the year; the amount of light intercepted by maize (Zea mays) plants via a functional-structural model using three-dimensional (3D) reconstructions of each plant placed in a virtual scene reproducing the canopy in the glasshouse; and RUE, as the ratio of plant biomass to intercepted light. The spatial variation of direct and diffuse incident light in the glasshouse (up to 24%) was correctly predicted at the single-plant scale. Light interception largely varied between maize lines that differed in leaf angles (nearly stable between experiments) and area (highly variable between experiments). Estimated RUEs varied between maize lines, but were similar in two experiments with contrasting incident light. They closely correlated with measured gas exchanges. The methods proposed here identified reproducible traits that might be used in further field studies, thereby opening up the way for large-scale genetic analyses of the components of plant performance. © 2016 INRA New Phytologist © 2016 New Phytologist Trust.
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Du, She-ni; Bai, Gang-shuan; Liang, Yin-li
2011-04-01
A pot experiment with artificial shading was conducted to study the effects of soil moisture content and light intensity on the plant growth and leaf physiological characteristics of squash variety "Jingyingyihao". Under all test soil moisture conditions, 30% shading promoted the growth of "Jingyingyihao", with the highest yield at 70% - 80% soil relative moisture contents. 70% shading inhibited plant growth severely, only flowering and not bearing fruits, no economic yield produced. In all treatments, there was a similar water consumption trend, i. e., both the daily and the total water consumption decreased with increasing shading and decreasing soil moisture content. Among all treatments, 30% shading and 70% - 80% soil relative moisture contents had the highest water use efficiency (2.36 kg mm(-1) hm(-2)) and water output rate (1.57 kg mm(-1) hm(-2)). The net photosynthetic rate, transpiration rate, stomatal conductance, and chlorophyll content of squash leaves decreased with increasing shading, whereas the intercellular CO2 concentration was in adverse. The leaf protective enzyme activity and proline content decreased with increasing shading, and the leaf MAD content decreased in the order of 70% shading, natural radiation, and 30% shading. Under the three light intensities, the change characteristics of squash leaf photosynthesis, protective enzyme activity, and proline and MAD contents differed with the increase of soil relative moisture content.
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Huang, Xu; Zhang, Qian; Jiang, Yupei; Yang, Chuanwei; Wang, Qianyue; Li, Lin
2018-06-21
Shade avoidance syndrome enables shaded plants to grow and compete effectively against their neighbors. In Arabidopsis , the shade-induced de-phosphorylation of the transcription factor PIF7 (PHYTOCHROME-INTERACTING FACTOR 7) is the key event linking light perception to stem elongation. However, the mechanism through which phosphorylation regulates the activity of PIF7 is unclear. Here, we show that shade light induces the de-phosphorylation and nuclear accumulation of PIF7. Phosphorylation-resistant site mutations in PIF7 result in increased nuclear localization and shade-induced gene expression, and consequently augment hypocotyl elongation. PIF7 interacts with 14-3-3 proteins. Blocking the interaction between PIF7 and 14-3-3 proteins or reducing the expression of 14-3-3 proteins accelerates shade-induced nuclear localization and de-phosphorylation of PIF7, and enhances the shade phenotype. By contrast, the 14-3-3 overexpressing line displays an attenuated shade phenotype. These studies demonstrate a phosphorylation-dependent translocation of PIF7 when plants are in shade and a novel mechanism involving 14-3-3 proteins, mediated by the retention of PIF7 in the cytoplasm that suppresses the shade response. © 2018, Huang et al.
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Flynn, Kevin J; Hansen, Per Juel
2013-11-01
In strict photoautotrophs, and in many mixotrophic protists, growth at low light stimulates the increased content of photopigment. This photoacclimation further elevates cellular Chl:C content through positive feedback (self-shading), until cellular Chl:C attains a maximum (ChlC(max)). This process, driven by the "selfish gene", enhances the fitness of the individual but decreases total population growth potential through community self-shading. However, some mixotrophic protists (generalist non-constitutives; GNC-mixotrophs) acquire their photosystems ready-made from phototrophic prey but they have no regulatory control on the acquired photosystems. When light is limiting, such organisms cannot photoacclimate; their total Chl:C ratio falls as their acquired photosystems are divided amongst daughter cells and also as the photosystems fail. We show that during that process, and with the removal (consumption) of their individually more efficient phototrophic prey, there is potential for populations of GNC-mixotrophs to become more efficient at light harvesting. Through this process these organisms may retain a critical additional period of photosynthetic capacity. Together with the fact that the acquired photosystem biomass can be potentially almost entirely converted into mixotroph biomass (while chloroplasts must remain an important component of biomass in constitutive mixotrophs, with an associated investment), this may help explain the success of GNC-mixotrophs. Copyright © 2013 Elsevier GmbH. All rights reserved.
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Dutilleul, Pierre; Han, Liwen; Valladares, Fernando; Messier, Christian
2015-01-01
Plant light interception and shade tolerance are intrinsically related in that they involve structural, morphological and physiological adaptations to manage light capture for photosynthetic utilization, in order to sustain survival, development and reproduction. At the scale of small-size trees, crown traits related to structural geometry of branching pattern and space occupancy through phyllotaxis can be accurately evaluated in 3D, using computed tomography (CT) scanning data. We demonstrate this by scrutinizing the crowns of 15 potted miniature conifers of different species or varieties, classified in two groups based on leaf type (10 needlelike, 5 scalelike); we also test whether mean values of crown traits measured from CT scanning data and correlations with a shade tolerance index (STI) differ between groups. Seven crown traits, including fractal dimensions (FD1: smaller scales, FD2: larger scales) and leaf areas, were evaluated for all 15 miniature conifers; an average silhouette-to-total-area ratio was also calculated for each of the 10 needlelike-leaf conifers. Between-group differences in mean values are significant (P < 0.05) for STI, FD1, FD2, and the average leaf area displayed (ĀD). Between-group differences in sign and strength of correlations are observed. For example, the correlation between STI and FD1 is negative and significant (P < 0.10) for the needlelike-leaf group, but is positive and significant (P < 0.05) for the miniature conifers with scalelike leaves, which had lower STI and higher FD1 on average in our study; the positive correlation between STI and ĀD is significant (P < 0.05) for the scalelike-leaf group, and very moderate for the needlelike-leaf one. A contrasting physical attachment of the leaves to branches may explain part of the between-group differences. Our findings open new avenues for the understanding of fundamental plant growth processes; the information gained could be included in a multi-scale approach to tree crown modeling. PMID:25852721
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Messinger, Susanna M; Ostling, Annette
2013-11-01
Predation interactions are an important element of ecological communities. Population spatial structure has been shown to influence predator evolution, resulting in the evolution of a reduced predator attack rate; however, the evolutionary role of traits governing predator and prey ecology is unknown. The evolutionary effect of spatial structure on a predator's attack rate has primarily been explored assuming a fixed metapopulation spatial structure, and understood in terms of group selection. But endogenously generated, emergent spatial structure is common in nature. Furthermore, the evolutionary influence of ecological traits may be mediated through the spatial self-structuring process. Drawing from theory on pathogens, the evolutionary effect of emergent spatial structure can be understood in terms of self-shading, where a voracious predator limits its long-term invasion potential by reducing local prey availability. Here we formalize the effects of self-shading for predators using spatial moment equations. Then, through simulations, we show that in a spatial context self-shading leads to relationships between predator-prey ecology and the predator's attack rate that are not expected in a non-spatial context. Some relationships are analogous to relationships already shown for host-pathogen interactions, but others represent new trait dimensions. Finally, since understanding the effects of ecology using existing self-shading theory requires simplifications of the emergent spatial structure that do not apply well here, we also develop metrics describing the complex spatial structure of the predator and prey populations to help us explain the evolutionary effect of predator and prey ecology in the context of self-shading. The identification of these metrics may provide a step towards expansion of the predictive domain of self-shading theory to more complex spatial dynamics. Copyright © 2013 Elsevier Inc. All rights reserved.
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Differences between the human eye and the spectrophotometer in the shade matching of tooth colour.
Gómez-Polo, Cristina; Gómez-Polo, Miguel; Celemin-Viñuela, Alicia; Martínez Vázquez De Parga, Juan Antonio
2014-06-01
The aim of this work was to assess the agreement between instrumental and visual colour matching. Shade selection with the 3DMaster Toothguide (Vita-Zahnfabrik) was performed for 1361 maxillary central incisors and compared with the shade obtained with the EasyShade Compact (Vita-Zahnfabrik) spectrophotometer. We observed a greater correlation between the objective method and the subjective one in the colour dimension of lightness (Kappa 0.6587), followed by hue (Kappa 0.4337) and finally chroma (Kappa 0.3578). The colour dimension in which the greatest agreement is seen between the operator and the spectrophotometer is value or lightness. This study reveals differences between the measurement of colour via spectrophotometry and the visual shade selection method. According to our results, there is better agreement in the value or lightness colour dimension, which is the most important one in the choice of tooth colour. Copyright © 2014 Elsevier Ltd. All rights reserved.
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Growth in relation to canopy light interception in a red pine (Pinus resinosa) thinning study
Beverly E. Law; Kurt H. Riitters; Lewis F. Ohmann
1992-01-01
Growth data from the most recent 5 years of a 40-year thinning study in an even-aged red pine (Pinus resinosa) forest in cutfoot sioux experimental forest, Minnesota, were used with intercepted photosynthetically active radiation (IPAR) data to determine the relationship between light interception and growth for a range ofstand densities. Stand basal...
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Smith, Duncan D; Sperry, John S; Enquist, Brian J; Savage, Van M; McCulloh, Katherine A; Bentley, Lisa P
2014-01-01
The West, Brown, Enquist (WBE) model derives symmetrically self-similar branching to predict metabolic scaling from hydraulic conductance, K, (a metabolism proxy) and tree mass (or volume, V). The original prediction was Kα V(0.75). We ask whether trees differ from WBE symmetry and if it matters for plant function and scaling. We measure tree branching and model how architecture influences K, V, mechanical stability, light interception and metabolic scaling. We quantified branching architecture by measuring the path fraction, Pf : mean/maximum trunk-to-twig pathlength. WBE symmetry produces the maximum, Pf = 1.0. We explored tree morphospace using a probability-based numerical model constrained only by biomechanical principles. Real tree Pf ranged from 0.930 (nearly symmetric) to 0.357 (very asymmetric). At each modeled tree size, a reduction in Pf led to: increased K; decreased V; increased mechanical stability; and decreased light absorption. When Pf was ontogenetically constant, strong asymmetry only slightly steepened metabolic scaling. The Pf ontogeny of real trees, however, was 'U' shaped, resulting in size-dependent metabolic scaling that exceeded 0.75 in small trees before falling below 0.65. Architectural diversity appears to matter considerably for whole-tree hydraulics, mechanics, photosynthesis and potentially metabolic scaling. Optimal architectures likely exist that maximize carbon gain per structural investment. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.
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Tsvuura, Zivanai; Griffiths, Megan E; Gunton, Richard M; Franks, Peter J; Lawes, Michael J
2010-12-01
The regeneration niche is commonly partitioned along a gradient from shade-tolerant to shade-intolerant species to explain plant community assembly in forests. We examined the shade tolerance of tree seedlings in a subtropical coastal forest to determine whether the ecological filtering effect of a dominant, synchronously monocarpic herb (Isoglossa woodii) selects for species at either end of the light response continuum during the herb's vegetative and reproductive phases. Photosynthetic characteristics of seedlings of 20 common tree species and the herb were measured. Seedlings were grown in the greenhouse at 12-14% irradiance, and their light compensation points measured using an open-flow gas exchange system. The light compensation points for the tree species were low, falling within a narrow range from 2.1 ± 0.8 μmol m(-2) s(-1) in Celtis africana to 6.4 ± 0.7 μmol m(-2) s(-1) in Allophylus natalensis, indicating general shade tolerance, consistent with a high and narrow range of apparent quantum yield among species (0.078 ± 0.002 mol CO(2) mol(-1) photon). Rates of dark respiration were significantly lower in a generalist pioneer species (Acacia karroo) than in a forest pioneer (C. africana), or in late successional phase forest species. We argue that the general shade tolerance, and phenotypic clustering of shade tolerance, in many tree species from several families in this system, is a result of ecological filtering by the prevailing low light levels beneath the I. woodii understorey, which excludes most light-demanding species from the seedling community.
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Santos, Leonardo D T; Da Cruz, Leandro R; Dos Santos, Samuel A; Sant'anna-Santos, Bruno F; Dos Santos, Izabela T; De Oliveira, Ariane M; Barros, Rodrigo E; Santos, Márcia V; Faria, Rodrigo M
2015-03-01
Plants have the ability to undergo morphophysiological changes based on availability of light. The present study evaluated biomass accumulation, leaf morphoanatomy and physiology of Neonotonia wightii and Pueraria phaseoloides grown in full sunlight, as well as in 30% and 50% shade. Two assays were performed, one for each species, using a randomized block design with 10 replicates. A higher accumulation of fresh mass in the shoot of the plants was observed for both species under cultivation in 50% shade, while no differences were detected between the full sunlight and 30% shade. N. wightii and P. phaseoloides showed increase in area and reduction in thickness leaf when cultivated in 50% shade. There were no changes in photosynthetic rate, stomatal conductance, water use efficiency and evapotranspiration of P. phaseoloides plants because growth environment. However, the shade treatments caused alterations in physiological parameters of N. wightii. In both species, structural changes in the mesophyll occurred depending on the availability of light; however, the amount of leaf blade tissue remained unaltered. Despite the influence of light intensity variation on the morphophysiological plasticity of N. wightii and P. phaseoloides, no effects on biomass accumulation were observed in response to light.
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Shade avoidance components and pathways in adult plants revealed by phenotypic profiling.
Nozue, Kazunari; Tat, An V; Kumar Devisetty, Upendra; Robinson, Matthew; Mumbach, Maxwell R; Ichihashi, Yasunori; Lekkala, Saradadevi; Maloof, Julin N
2015-04-01
Shade from neighboring plants limits light for photosynthesis; as a consequence, plants have a variety of strategies to avoid canopy shade and compete with their neighbors for light. Collectively the response to foliar shade is called the shade avoidance syndrome (SAS). The SAS includes elongation of a variety of organs, acceleration of flowering time, and additional physiological responses, which are seen throughout the plant life cycle. However, current mechanistic knowledge is mainly limited to shade-induced elongation of seedlings. Here we use phenotypic profiling of seedling, leaf, and flowering time traits to untangle complex SAS networks. We used over-representation analysis (ORA) of shade-responsive genes, combined with previous annotation, to logically select 59 known and candidate novel mutants for phenotyping. Our analysis reveals shared and separate pathways for each shade avoidance response. In particular, auxin pathway components were required for shade avoidance responses in hypocotyl, petiole, and flowering time, whereas jasmonic acid pathway components were only required for petiole and flowering time responses. Our phenotypic profiling allowed discovery of seventeen novel shade avoidance mutants. Our results demonstrate that logical selection of mutants increased success of phenotypic profiling to dissect complex traits and discover novel components.
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Munguía-Rosas, Miguel A; Campos-Navarrete, María J; Parra-Tabla, Víctor
2013-01-01
Dimorphic cleistogamy is a specialized form of mixed mating system where a single plant produces both open, potentially outcrossed chasmogamous (CH) and closed, obligately self-pollinated cleistogamous (CL) flowers. Typically, CH flowers and seeds are bigger and energetically more costly than those of CL. Although the effects of inbreeding and floral dimorphism are critical to understanding the evolution and maintenance of cleistogamy, these effects have been repeatedly confounded. In an attempt to separate these effects, we compared the performance of progeny derived from the two floral morphs while controlling for the source of pollen. That is, flower type and pollen source effects were assessed by comparing the performance of progeny derived from selfed CH vs. CL and outcrossed CH vs. selfed CH flowers, respectively. The experiment was carried out with the herb Ruellia nudiflora under two contrasting light environments. Outcrossed progeny generally performed better than selfed progeny. However, inbreeding depression ranges from low (1%) to moderate (36%), with the greatest value detected under shaded conditions when cumulative fitness was used. Although flower type generally had less of an effect on progeny performance than pollen source did, the progeny derived from selfed CH flowers largely outperformed the progeny from CL flowers, but only under shaded conditions and when cumulative fitness was taken into account. On the other hand, the source of pollen and flower type influenced seed predation, with selfed CH progeny the most heavily attacked by predators. Therefore, the effects of pollen source and flower type are environment-dependant and seed predators may increase the genetic differences between progeny derived from CH and CL flowers. Inbreeding depression alone cannot account for the maintenance of a mixed mating system in R. nudiflora and other unidentified mechanisms must thus be involved.
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Peer, W A; Briggs, W R; Langenheim, J H
1999-05-01
Shade-avoidance responses were examined for two species common to the coastal redwood forest, Sequoia sempervirens and Satureja douglasii. Sequoia seedlings demonstrated a shade-avoidance response when given end-of-day far-red light by increased hypocotyl, epicotyl, and first-node extension, and greater total number of needles and reduced anthocyanin concentration. Thus, Sequoia seedlings respond as sun-adapted plants. Satureja has several leaf monoterpene chemotypes that occur in different light environments including the redwood forest, and the types responded differently to the light treatments. The pulegone type responded to end-of-day far-red light as a sun-adapted plant with significant extension growth, increased leaf area and chlorophyll, and reduced anthocyanin. The isomenthone type responded as a shade-tolerant plant and did not exhibit extension growth nor a change in other parameters with end-of-day far-red light. However, the carvone and bicyclic types had variable responses depending on the parameter studied, which indicated genetic variation for these traits.
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Dutilleul, Pierre; Han, Liwen; Smith, Donald L
2008-01-01
Light interception by the leaf canopy is a key aspect of plant photosynthesis, which helps mitigate the greenhouse effect via atmospheric CO(2) recycling. The relationship between plant light interception and leaf area was traditionally modelled with the Beer-Lambert law, until the spatial distribution of leaves was incorporated through the fractal dimension of leafless plant structure photographed from the side allowing maximum appearance of branches and petioles. However, photographs of leafless plants are two-dimensional projections of three-dimensional structures, and sampled plants were cut at the stem base before leaf blades were detached manually, so canopy development could not be followed for individual plants. Therefore, a new measurement and modelling approach were developed to explain plant light interception more completely and precisely, based on appropriate processing of computed tomography (CT) scanning data collected for developing canopies. Three-dimensional images of canopies were constructed from CT scanning data. Leaf volumes (LV) were evaluated from complete canopy images, and fractal dimensions (FD) were estimated from skeletonized leafless images. The experimental plant species is pyramidal cedar (Thuja occidentalis, Fastigiata). The three-dimensional version of the Beer-Lambert law based on FD alone provided a much better explanation of plant light interception (R(2) = 0.858) than those using the product LV*FD (0.589) or LV alone (0.548). While values of all three regressors were found to increase over time, FD in the Beer-Lambert law followed the increase in light interception the most closely. The delayed increase of LV reflected the appearance of new leaves only after branches had lengthened and ramified. The very strong correlation obtained with FD demonstrates that CT scanning data contain fundamental information about the canopy architecture geometry. The model can be used to identify crops and plantation trees with improved light interception and productivity.
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Dutilleul, Pierre; Han, Liwen; Smith, Donald L.
2008-01-01
Background and Aims Light interception by the leaf canopy is a key aspect of plant photosynthesis, which helps mitigate the greenhouse effect via atmospheric CO2 recycling. The relationship between plant light interception and leaf area was traditionally modelled with the Beer–Lambert law, until the spatial distribution of leaves was incorporated through the fractal dimension of leafless plant structure photographed from the side allowing maximum appearance of branches and petioles. However, photographs of leafless plants are two-dimensional projections of three-dimensional structures, and sampled plants were cut at the stem base before leaf blades were detached manually, so canopy development could not be followed for individual plants. Therefore, a new measurement and modelling approach were developed to explain plant light interception more completely and precisely, based on appropriate processing of computed tomography (CT) scanning data collected for developing canopies. Methods Three-dimensional images of canopies were constructed from CT scanning data. Leaf volumes (LV) were evaluated from complete canopy images, and fractal dimensions (FD) were estimated from skeletonized leafless images. The experimental plant species is pyramidal cedar (Thuja occidentalis, Fastigiata). Key Results The three-dimensional version of the Beer–Lambert law based on FD alone provided a much better explanation of plant light interception (R2 = 0·858) than those using the product LV*FD (0·589) or LV alone (0·548). While values of all three regressors were found to increase over time, FD in the Beer–Lambert law followed the increase in light interception the most closely. The delayed increase of LV reflected the appearance of new leaves only after branches had lengthened and ramified. Conclusions The very strong correlation obtained with FD demonstrates that CT scanning data contain fundamental information about the canopy architecture geometry. The model can be used to identify crops and plantation trees with improved light interception and productivity. PMID:17981879
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Xie, Hongtao; Yu, Mukui; Cheng, Xiangrong
2018-03-01
Light availability greatly affects plant growth and development. In shaded environments, plants must respond to reduced light intensity to ensure a regular rate of photosynthesis to maintain the dynamic balance of nutrients, such as leaf non-structural carbohydrates (NSCs), carbon (C), nitrogen (N) and phosphorus (P). To improve our understanding of the nutrient utilization strategies of understory shade-tolerant plants, we compared the variations in leaf NSCs, C, N and P in response to heterogeneous controlled light conditions between two subtropical evergreen broadleaf shade-tolerant species, Elaeocarpus sylvestris (E. sylvestris) and Illicium henryi (I. henryi). Light intensity treatments were applied at five levels (100%, 52%, 33%, 15% and 6% full sunlight) for 30 weeks to identify the effects of reduced light intensity on leaf NSC allocation patterns and leaf C:N:P stoichiometry characteristics. We found that leaf soluble sugar, starch and NSC concentrations in E. sylvestris showed decreasing trends with reduced light intensity, whereas I. henryi presented slightly increasing trends from 100% to 15% full sunlight and then significant decreases at extremely low light intensity (6% full sunlight). The soluble sugar/starch ratio of E. sylvestris decreased with decreasing light intensity, whereas that of I. henryi remained stable. Moreover, both species exhibited increasing trends in leaf N and P concentrations but limited leaf N:P and C:P ratio fluctuations with decreasing light intensity, revealing their adaptive strategies for poor light environments and their growth strategies under ideal light environments. There were highly significant correlations between leaf NSC variables and C:N:P stoichiometric variables in both species, revealing a trade-off in photosynthesis production between leaf NSC and carbon allocation. Thus, shade-tolerant plants readjusted their allocation of leaf NSCs, C, N and P in response to light acclimation. Redundancy analysis showed that leaf morphological features of both E. sylvestris and I. henryi affected their corresponding leaf nutrient traits. These results improve our understanding of the dynamic balance between leaf NSCs and leaf C, N and P components in the nutritional metabolism of shade-tolerant plants. Two species of understory shade-tolerant plants responded differently to varying light intensities in terms of leaf non-structural carbohydrate allocation and the utilization of carbon, nitrogen and phosphorus to balance nutritional metabolism and adapt to environmental stress. Copyright © 2018 Elsevier Masson SAS. All rights reserved.
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Shading reduces growth of longleaf and loblolly pine seedlings in containers
James P. Barnett
1989-01-01
Development of longleaf (Pinus palustris Mill.) and loblolly (P. taeda L.) pine seediings growing under three light conditions--full sunlight, 30% shade, and 50% shade--was evaluated. Although there was little difference between development of seedlings in 30% and 50% shade, those grown is full sunlight were signiticantly larger...
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Patterns of shading tolerance determined from experimental light reduction studies of seagrasses
An extensive review of the experimental literature on seagrass shading evaluated the relationship between experimental light reductions, duration of experiment and seagrass response metrics to determine whether there were consistent statistical patterns. There were highly signif...
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Fish with red fluorescent eyes forage more efficiently under dim, blue-green light conditions.
Harant, Ulrike Katharina; Michiels, Nicolaas Karel
2017-04-20
Natural red fluorescence is particularly conspicuous in the eyes of some small, benthic, predatory fishes. Fluorescence also increases in relative efficiency with increasing depth, which has generated speculation about its possible function as a "light organ" to detect cryptic organisms under bluish light. Here we investigate whether foraging success is improved under ambient conditions that make red fluorescence stand out more, using the triplefin Tripterygion delaisi as a model system. We repeatedly presented 10 copepods to individual fish (n = 40) kept under a narrow blue-green spectrum and compared their performance with that under a broad spectrum with the same overall brightness. The experiment was repeated for two levels of brightness, a shaded one representing 0.4% of the light present at the surface and a heavily shaded one with about 0.01% of the surface brightness. Fish were 7% more successful at catching copepods under the narrow, fluorescence-friendly spectrum than under the broad spectrum. However, this effect was significant under the heavily shaded light treatment only. This outcome corroborates previous predictions that fluorescence may be an adaptation to blue-green, heavily shaded environments, which coincides with the opportunistic biology of this species that lives in the transition zone between exposed and heavily shaded microhabitats.
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Zachariades, Costas; Heshula, Lelethu U.; Hill, Martin P.
2018-01-01
Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear. PMID:29304104
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Uyi, Osariyekemwen O; Zachariades, Costas; Heshula, Lelethu U; Hill, Martin P
2018-01-01
Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
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Bender, B; Capellesso, E S; Lottici, M E; Sentkovski, J; Mielniczki-Pereira, A A; Rosa, L M G; Sausen, T L
2017-01-01
Flood events in riparian forests of southern Brazil, can be characterized as unpredictable and of low magnitude with an average duration of less than 15 days. Inga marginata is an evergreen tree which grows in Southeast South America on a wide range of environments, including riparian forests. In this paper, the interactive effects of the light environment and soil flooding on morphological parameters of I. marginata were examined. Seedlings were acclimated in two contrasting light conditions: sun or shade for 30 days. Sun and shade plants were subjected to soil flooding for two periods; five or 15 days. After 5 days, the interaction between flooding and light did not affect growth, chlorophyll content and dry mass or the root-shoot ratio. After 15 days, flooded plants from the sunny treatment had a lower shoot dry mass compared to control sun plants and flooded plants from the shaded treatment. Moreover, the higher dry mass observed for shade plants compared to sun plants, following flooding, can also be directly associated with a higher content of soluble sugars. Shade plants of I. marginata showed a greater acclimation to soil waterlogging. This acclimation appears to be associated with a larger accumulation of soluble sugars compared to non-flooded plants. The responses observed on the shade plants appear to be decisive to indicate the use of I. marginata in degraded areas.
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Sm, Mousavinasab; M, Atai; N, Salehi; A, Salehi
2016-12-01
The degree of conversion depends on the material composition, light source properties, distance from light source, light intensity, curing time, and other factors such as shade and translucency. In the present study, we evaluated the effects of different light-curing modes and shades of methacrylate and silorane-based resin composites on the degree of conversion of resin composites (DC). The methacrylate-based (Filtek Z250, 3M, ESPE) and low-shrinkage silorane-based (Filtek P90, 3M, ESPE) resin composites were used in three groups as follows: group 1-Filtek Z250 (shade A3), group 2-Filtek Z250 (shade B2), and group 3-Filtek P90 (shade A3). We used a light-emitting diode (LED) curing unit for photopolymerization. 10 samples were prepared in each group to evaluate the degree of conversion; 5 samples were cured using soft-start curing mode, and the other 5 were cured using standard curing mode. The DC of the resin composites was measured using Fourier Transform Infrared Spectroscopy (FTIR). The data were analyzed using Kruskal Wallis and one-way ANOVA statistical tests. The degree of conversion of silorane-based resin composite was 70 - 75.8% and that of methacrylate-based resin composites was 60.2 - 68.2% (p = 0.009). The degree of conversion of the composite with brighter colour (B2) was statistically more than the darker composite (A3). Higher degree of conversion was achieved applying the standard curing mode. The results of the study showed that the colour and type of the resin composite and also the curing mode influence the degree of conversion of resin composites.
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Leicht, Stacey A; Silander, John A
2006-07-01
When plants are subjected to leaf canopy shade in forest understories or from neighboring plants, they not only experience reduced light quantity, but light quality in lowered red : far red light (R : FR). Growth and other developmental responses of plants in reduced R : FR can vary and are not consistent across species. We compared how an invasive liana, Celastrus orbiculatus, and its closely related native congener, C. scandens, responded to changes in the R : FR under controlled, simulated understory conditions. We measured a suite of morphological and growth attributes under control, neutral shading, and low R : FR light treatments. Celastrus orbiculatus showed an increase in height, aboveground biomass, and total leaf mass in reduced R : FR treatments as compared to the neutral shade, while C. scandens had increased stem diameter, single leaf area, and leaf mass to stem mass ratio. These differences provide a mechanistic understanding of the ability of C. orbiculatus to increase height and actively forage for light resources in forest understories, while C. scandens appears unable to forage for light and instead depends upon a light gap forming. The plastic growth response of C. orbiculatus in shaded conditions points to its success in forested habitats where C. scandens is largely absent.
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Leicht, S.A.; Silander, J.A.
2006-01-01
When plants are subjected to leaf canopy shade in forest understories or from neighboring plants, they not only experience reduced light quantity, but light quality in lowered red:far red light (R:FR). Growth and other developmental responses of plants in reduced R:FR can vary and are not consistent across species. We compared how an invasive liana, Celastrus orbiculatus, and its closely related native congener, C. scandens, responded to changes in the R:FR under controlled, simulated understory conditions. We measured a suite of morphological and growth attributes under control, neutral shading, and low R:FR light treatments. Celastrus orbiculatus showed an increase in height, aboveground biomass, and total leaf mass in reduced R:FR treatments as compared to the neutral shade, while C. scandens had increased stem diameter, single leaf area, and leaf mass to stem mass ratio. These differences provide a mechanistic understanding of the ability of C. orbiculatus to increase height and actively forage for light resources in forest understories, while C. scandens appears unable to forage for light and instead depends upon a light gap forming. The plastic growth response of C. orbiculatus in shaded conditions points to its success in forested habitats where C. scandens is largely absent.
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Effect of light-curing units, post-cured time and shade of resin cement on knoop hardness.
Reges, Rogério Vieira; Costa, Ana Rosa; Correr, Américo Bortolazzo; Piva, Evandro; Puppin-Rontani, Regina Maria; Sinhoreti, Mário Alexandre Coelho; Correr-Sobrinho, Lourenço
2009-01-01
The aim of this study was to evaluate the Knoop hardness after 15 min and 24 h of different shades of a dual-cured resin-based cement after indirect photoactivation (ceramic restoration) with 2 light-curing units (LCUs). The resin cement Variolink II (Ivoclar Vivadent) shade XL, A2, A3 and opaque were mixed with the catalyst paste and inserted into a black Teflon mold (5 mm diameter x 1 mm high). A transparent strip was placed over the mold and a ceramic disc (Duceram Plus, shade A3) was positioned over the resin cement. Light-activation was performed through the ceramic for 40 s using quartz-tungsten-halogen (QTH) (XL 2500; 3M ESPE) or light-emitting diode (LED) (Ultrablue Is, DMC) LCUs with power density of 615 and 610 mW/cm(2), respectively. The Koop hardness was measured using a microhardness tester HMV 2 (Shimadzu) after 15 min or 24 h. Four indentations were made in each specimen. Data were subjected to ANOVA and Tukey's test (alpha=0.05). The QTH LCU provided significantly higher (p<0.05) KHN values than the LED LCU. When the post-cure times were compared for the same shade, QTH and LED at 24 h provided significantly higher (p<0.05) KHN values than at 15 min. It may be concluded that the Knoop hardness was generally dependent on the LCU and post-cure time. The opaque shade of the resin cement showed lower Knoop hardness than the other shades for both LCUs and post-cure times.
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Simulation of tree shade impacts on residential energy use for space conditioning in Sacramento
NASA Astrophysics Data System (ADS)
Simpson, J. R.; McPherson, E. G.
Tree shade reduces summer air conditioning demand and increases winter heating load by intercepting solar energy that would otherwise heat the shaded structure. We evaluate the magnitude of these effects here for 254 residential properties participating in a utility sponsored tree planting program in Sacramento, California. Tree and building characteristics and typical weather data are used to model hourly shading and energy used for space conditioning for each building for a period of one year. There were an average of 3.1 program trees per property which reduced annual and peak (8 h average from 1 to 9 p.m. Pacific Daylight Time) cooling energy use 153 kWh (7.1%) and 0.08 kW (2.3%) per tree, respectively. Annual heating load increased 0.85 GJ (0.80 MBtu, 1.9%) per tree. Changes in cooling load were smaller, but percentage changes larger, for newer buildings. Averaged over all homes, annual cooling savings of 15.25 per tree were reduced by a heating penalty of 5.25 per tree, for net savings of 10.00 per tree from shade. We estimate an annual cooling penalty of 2.80 per tree and heating savings of 6.80 per tree from reduced wind speed, for a net savings of 4.00 per tree, and total annual savings of 14.00 per tree (43.00 per property). Results are found to be consistent with previous simulations and the limited measurements available.
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NASA Technical Reports Server (NTRS)
Franklin, Janet; Duncan, Jeff; Huete, Alfredo R.; vanLeeuwen, W. J. D.; Li, Xiaowen; Begue, Agnes
1994-01-01
To use optical remote sensing to monitor land surface-climate interactions over large areas, algorithms must be developed to relate multispectral measurements to key variables controlling the exchange of matter (water, carbon dioxide) and energy between the land surface and the atmosphere. The proportion of the ground covered by vegetation and the interception of photosynthetically active radiation (PAR) by vegetation are examples of two variables related to evapotranspiration and primary production, respectively. An areal-proportion model of the multispectral reflectance of shrub savanna, composed of scattered shrubs with a grass, forb or soil understory, predicted the reflectance of two 0.5 km(exp 2) sites as the area-weighted average of the shrub and understory or 'background' reflectances. Although the shaded crown and shaded background have darker reflectances, ignoring them in the area-weighted model is not serious when shrub cover is low and solar zenith angle is small. A submodel predicted the reflectance of the shrub crown as a function of the foliage reflectance and amount of plant material within the crown, and the background reflectance scattered or transmitted through canopy gaps (referred to as a soil-plant 'spectral interaction' term). One may be able to combine these two models to estimate both the fraction of vegetation cover and interception of PAR by green vegetation in a shrub savanna.
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Hedley, John D; McMahon, Kathryn; Fearns, Peter
2014-01-01
A three-dimensional computer model of canopies of the seagrass Amphibolis griffithii was used to investigate the consequences of variations in canopy structure and benthic light environment on leaf-level photosynthetic saturation state. The model was constructed using empirical data of plant morphometrics from a previously conducted shading experiment and validated well to in-situ data on light attenuation in canopies of different densities. Using published values of the leaf-level saturating irradiance for photosynthesis, results show that the interaction of canopy density and canopy-scale photosynthetic response is complex and non-linear, due to the combination of self-shading and the non-linearity of photosynthesis versus irradiance (P-I) curves near saturating irradiance. Therefore studies of light limitation in seagrasses should consider variation in canopy structure and density. Based on empirical work, we propose a number of possible measures for canopy scale photosynthetic response that can be plotted to yield isoclines in the space of canopy density and light environment. These plots can be used to interpret the significance of canopy changes induced as a response to decreases in the benthic light environment: in some cases canopy thinning can lead to an equivalent leaf level light environment, in others physiological changes may also be required but these alone may be inadequate for canopy survival. By providing insight to these processes the methods developed here could be a valuable management tool for seagrass conservation during dredging or other coastal developments.
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Hedley, John D.; McMahon, Kathryn; Fearns, Peter
2014-01-01
A three-dimensional computer model of canopies of the seagrass Amphibolis griffithii was used to investigate the consequences of variations in canopy structure and benthic light environment on leaf-level photosynthetic saturation state. The model was constructed using empirical data of plant morphometrics from a previously conducted shading experiment and validated well to in-situ data on light attenuation in canopies of different densities. Using published values of the leaf-level saturating irradiance for photosynthesis, results show that the interaction of canopy density and canopy-scale photosynthetic response is complex and non-linear, due to the combination of self-shading and the non-linearity of photosynthesis versus irradiance (P-I) curves near saturating irradiance. Therefore studies of light limitation in seagrasses should consider variation in canopy structure and density. Based on empirical work, we propose a number of possible measures for canopy scale photosynthetic response that can be plotted to yield isoclines in the space of canopy density and light environment. These plots can be used to interpret the significance of canopy changes induced as a response to decreases in the benthic light environment: in some cases canopy thinning can lead to an equivalent leaf level light environment, in others physiological changes may also be required but these alone may be inadequate for canopy survival. By providing insight to these processes the methods developed here could be a valuable management tool for seagrass conservation during dredging or other coastal developments. PMID:25347849
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Growth, biomass allocation and photosynthesis of invasive and native Hawaiian rainforest species.
Pattison, R R; Goldstein, G; Ares, A
1998-12-01
Growth, biomass allocation, and photosynthetic characteristics of seedlings of five invasive non-indigenous and four native species grown under different light regimes were studied to help explain the success of invasive species in Hawaiian rainforests. Plants were grown under three greenhouse light levels representative of those found in the center and edge of gaps and in the understory of Hawaiian rainforests, and under an additional treatment with unaltered shade. Relative growth rates (RGRs) of invasive species grown in sun and partial shade were significantly higher than those for native species, averaging 0.25 and 0.17 g g -1 week -1 , respectively, while native species averaged only 0.09 and 0.06 g g -1 week -1 , respectively. The RGR of invasive species under the shade treatment was 40% higher than that of native species. Leaf area ratios (LARs) of sun and partial-shade-grown invasive and native species were similar but the LAR of invasive species in the shade was, on average, 20% higher than that of native species. There were no differences between invasive and native species in biomass allocation to shoots and roots, or in leaf mass per area across light environments. Light-saturated photosynthetic rates (Pmax) were higher for invasive species than for native species in all light treatments. Pmax of invasive species grown in the sun treatment, for example, ranged from 5.5 to 11.9 μmol m -2 s -1 as compared with 3.0-4.5 μmol m -2 s -1 for native species grown under similar light conditions. The slope of the linear relationship between Pmax and dark respiration was steeper for invasive than for native species, indicating that invasive species assimilate more CO 2 at a lower respiratory cost than native species. These results suggest that the invasive species may have higher growth rates than the native species as a consequence of higher photosynthetic capacities under sun and partial shade, lower dark respiration under all light treatments, and higher LARs when growing under shade conditions. Overall, invasive species appear to be better suited than native species to capturing and utilizing light resources, particularly in high-light environments such as those characterized by relatively high levels of disturbance.
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Winter, K; Osmond, C B; Hubick, K T
1986-01-01
Crassulacean acid metabolism (CAM) was studied in a tropical epiphytic fern, Pyrrosia longifolia, from a fully sun-exposed and from a very shaded site in Northern Queensland, Australia. Measurements of instantaneous net CO 2 exchange showed carbon gain via CO 2 dark fixation with some net CO 2 uptake also occuring during late afternoon, in both sun and shade fronds. Maximum rates of net CO 2 uptake and the nocturnal increase in titratable acidity were lower in shade than in sun fronds. δ 13 C values of sun and shade fronds were not significantly different, and ranged between-14 and-15‰ suggesting that, in the long term, carbon gain was mainly via CO 2 dark fixation. Sun fronds had a higher light compensation point of photosynthesis than shade fronds but the same quantum yield. Yet there was no acclimation of photosynthetic O 2 evolution, (measured at 5% CO 2 ) in sun and shade fronds and photosynthesis saturated at between 200 and 400 μmol quanta m -2 s -1 . Use of higher light intensities for photosynthesis of sun fronds was probably precluded by low nutrient availability. Total nitrogen was less than 1% of dry weight in fully expanded sun and shade fronds. Exposure of shade fronds to full sunlight for 6 h led to a 60% decline in the quantum yield of photosynthesis and to a decline in variable fluorescence measured at room temperature. Photoinhibition by high light was also observed in Hoya nicholsoniae, a rainforest climber growing in deep shade. This species also exhibited CAM as demonstrated by nocturnal net CO 2 uptake, nocturnal acidification and a δ 13 C value of-14‰. Photosynthetic O 2 evolution in this species was saturated at 2.5% of full sunlight. Two species of Dendrobium (Orchidaceae) from sun-exposed sites, one species exhibiting CAM and the other one exhibiting net CO 2 uptake exclusively during daytime via conventional C 3 photosynthesis, showed similar light response curves and the same quantum yield for photosynthetic O 2 evolution.
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Llorente, Briardo; D'Andrea, Lucio; Ruiz-Sola, M Aguila; Botterweg, Esther; Pulido, Pablo; Andilla, Jordi; Loza-Alvarez, Pablo; Rodriguez-Concepcion, Manuel
2016-01-01
Carotenoids are isoprenoid compounds that are essential for plants to protect the photosynthetic apparatus against excess light. They also function as health-promoting natural pigments that provide colors to ripe fruit, promoting seed dispersal by animals. Work in Arabidopsis thaliana unveiled that transcription factors of the phytochrome-interacting factor (PIF) family regulate carotenoid gene expression in response to environmental signals (i.e. light and temperature), including those created when sunlight reflects from or passes though nearby vegetation or canopy (referred to as shade). Here we show that PIFs use a virtually identical mechanism to modulate carotenoid biosynthesis during fruit ripening in tomato (Solanum lycopersicum). However, instead of integrating environmental information, PIF-mediated signaling pathways appear to fulfill a completely new function in the fruit. As tomatoes ripen, they turn from green to red due to chlorophyll breakdown and carotenoid accumulation. When sunlight passes through the flesh of green fruit, a self-shading effect within the tissue maintains high levels of PIFs that directly repress the master gene of the fruit carotenoid pathway, preventing undue production of carotenoids. This effect is attenuated as chlorophyll degrades, causing degradation of PIF proteins and boosting carotenoid biosynthesis as ripening progresses. Thus, shade signaling components may have been co-opted in tomato fruit to provide information on the actual stage of ripening (based on the pigment profile of the fruit at each moment) and thus finely coordinate fruit color change. We show how this mechanism may be manipulated to obtain carotenoid-enriched fruits. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.
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Shading Vita In-ceram YZ substructures: influence on value and chroma, part II.
Devigus, A; Lombardi, G
2004-10-01
In this study, the influence of differently shaded substructures made of Y-TZP from different manufacturers (without, with 0.5 mm or 1.0 mm ceramic veneer with Vita VM9 Base Dentin) on the lightness, the saturation, and the color shade (= value, chroma, and hue) was measured and assessed with a spectral photometer (Easy Shade, Vita) on a clinical case in the mouth and on models of different color. Shading substructures made of Y-TZP facilitated adaptation to the basic shade and reduced the layer thickness of the veneer ceramic required to achieve the desired color. This should be done in the future as a matter of routine. In this way, tooth substance can be better conserved when preparing the teeth, and the esthetic result is not diminished. The material used for the production of the working models (plaster or plastic) should be tooth colored and in terms of lightness--analogous to the shading of the substructure--in order to facilitate clinical color measurement and quality control in the laboratory.
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Zou, Chang-ming; Wang, Yun-qing; Cao, Wei-dong; Liu, Ying; Zhang, Xiao-hong; Tang, Shan
2015-12-01
In order to determine the adaptability of Adzuki beans as the interplanting crops in fruit yards, field and pot experimental treatments with full natural light and weak light (48% of full natural light) regimes were conducted to test the shade tolerance and physiological responses of three Adzuki bean varieties including Funan green Vigna angularis (FGVA), early-mature black V. angularis (EBVA) and late-mature black V. angularis (LBVA). The leaf photosynthetic characteristic parameters, photosynthetic pigment contents and the activity of RuBPCase were measured during the first bloom stage. The response of growth to weak light was likewise studied. The results showed that the photosynthetic characteristic parameters, i.e., the maximum net photosynthetic rate, light saturation point and light compensation point of the three Adzuki bean varieties under the weak light stress changed differently. The weak light stress induced the reduction of net photosynthetic rate, water use efficiency and RuBPCase activity of the three Adzuki bean varieties significantly. The contents of chlorophyll a and chlorophyll b in leaves of FGVA increased significantly, while Chl a/b and carotenoid content in the leaves decreased significantly after shading. But the other two varieties did not change obviously in photosynthetic pigments content after shading. The weak light changed the growth of the three Adzuki bean varieties, such as decreasing dry matter yield and dry matter accumulation efficiency, reducing root nodule and root-shoot ratio, debasing leaves quantity and leaf area index. The first bloom stage and maturing stage of FGVA advanced, while that of EBVA delayed under weak light. However, flowers were not strong enough to seed for LBVA under the weak light. In conclusion, according to the photosynthetic characteristics changes after shading, as well as the growth status, we concluded that the shade tolerance of the three Adzuki beans was ranked as FGVA>EBVA>LBVA.
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Partial Shade Stress Test for Thin-Film Photovoltaic Modules: Preprint
DOE Office of Scientific and Technical Information (OSTI.GOV)
Silverman, Timothy J.; Deceglie, Michael G.; Deline, Chris
2015-09-02
Partial shade of monolithic thin-film PV modules can cause reverse-bias conditions leading to permanent damage. In this work, we propose a partial shade stress test for thin-film PV modules that quantifies permanent performance loss. We designed the test with the aid of a computer model that predicts the local voltage, current and temperature stress that result from partial shade. The model predicts the module-scale interactions among the illumination pattern, the electrical properties of the photovoltaic material and the thermal properties of the module package. The test reproduces shading and loading conditions that may occur in the field. It accounts formore » reversible light-induced performance changes and for additional stress that may be introduced by light-enhanced reverse breakdown. We present simulated and experimental results from the application of the proposed test.« less
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Xu, Y X
2018-06-18
To investigate which shade guide, Vitapan Classical or Vita Bleachedguide 3DMaster, is better matched with the color of teeth in judging whitening effect, by comparing the color difference between shade tabs and corresponding teeth underwent cold light tooth whitening. A total of 60 patients underwent Beyond cold light tooth whitening from May 2014 to April 2016. The patients were divided into two experimental groups according to the shade guide used. Vitapan Classical shade guide was used to judge whitening effect in one group, and Vita Bleachedguide 3DMaster shade guide was used in another. Shade matching was carried out before and after whitening in both the two groups, and the results were recorded by digital photographs. Shade matching procedures were carried out by two doctors independently. If they chose the same tab, it would be seen as the shade matching result; While if they chose different tabs, another doctor would be invited to make a decision. Photographs were taken in preset conditions: intraoral photos of the full dentition in the front, and the proportion of shooting was 1:3; aperture was F22; shutter speed was 1/200; intensity of flash was M/8; ISO value was 200. The photographs were analyzed by Photoshop software. Chromatic values were measured, and color difference values were calculated. Measuring of chromatic values was carried out by three doctors independently, and all the photos were measured twice by each doctor. Six measure results of each photo were recorded, and the maximum and the minimum were excluded, then the mean was seen as the final result. The color difference values were compared by independent-sample t test. Besides, changes of shade tabs after whitening in the two groups were recorded. Color difference value was 5.06±1.71 in Vitapan Classical group, and 3.39±1.36 in Vita Bleachedguide 3D-Master group. There was statistically significant difference between the two groups (t=4.68,P<0.001). Change of shade tabs was 3.63±1.75 in Vitapan Classical group, and 2.23±1.01 in Vita Bleachedguide 3DMaster group. Vita Bleachedguide 3D-Master is better matched with the color of teeth, so it is preferred in judging the effect of cold light tooth whitening.
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Zavala, Miguel A; Angulo, Oscar; Bravo de la Parra, Rafael; López-Marcos, Juan C
2007-02-07
Light competition and interspecific differences in shade tolerance are considered key determinants of forest stand structure and dynamics. Specifically two main stand diameter distribution types as a function of shade tolerance have been proposed based on empirical observations. All-aged stands of shade tolerant species tend to have steeply descending, monotonic diameter distributions (inverse J-shaped curves). Shade intolerant species in contrast typically exhibit normal (unimodal) tree diameter distributions due to high mortality rates of smaller suppressed trees. In this study we explore the generality of this hypothesis which implies a causal relationship between light competition or shade tolerance and stand structure. For this purpose we formulate a partial differential equation system of stand dynamics as a function of individual tree growth, recruitment and mortality which allows us to explore possible individual-based mechanisms--e.g. light competition-underlying observed patterns of stand structure--e.g. unimodal or inverse J-shaped equilibrium diameter curves. We find that contrary to expectations interspecific differences in growth patterns can result alone in any of the two diameter distributions types observed in the field. In particular, slow growing species can present unimodal equilibrium curves even in the absence of light competition. Moreover, light competition and shade intolerance evaluated both at the tree growth and mortality stages did not have a significant impact on stand structure that tended to converge systematically towards an inverse J-shaped curves for most tree growth scenarios. Realistic transient stand dynamics for even aged stands of shade intolerant species (unimodal curves) were only obtained when recruitment was completely suppressed, providing further evidence on the critical role played by juvenile stages of tree development (e.g. the sampling stage) on final forest structure and composition. The results also point out the relevance of partial differential equations systems as a tool for exploring the individual-level mechanisms underpinning forest structure, particularly in relation to more complex forest simulation models that are more difficult to analyze and to interpret from a biological point of view.
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NASA Astrophysics Data System (ADS)
Gignoux, Jacques; Konaté, Souleymane; Lahoreau, Gaëlle; Le Roux, Xavier; Simioni, Guillaume
2016-12-01
The forest-savanna ecotone may be very sharp in fire-prone areas. Fire and competition for light play key roles in its maintenance, as forest and savanna tree seedlings are quickly excluded from the other ecosystem. We hypothesized a tradeoff between seedling traits linked to fire resistance and to competition for light to explain these exclusions. We compared growth- and survival-related traits of two savanna and two forest species in response to shading and fire in a field experiment. To interpret the results, we decomposed our broad hypothesis into elementary tradeoffs linked to three constraints, biomass allocation, plant architecture, and shade tolerance, that characterize both savanna and adjacent forest ecosystems. All seedlings reached similar biomasses, but forest seedlings grew taller. Savanna seedlings better survived fire after topkill and required ten times less biomass than forest seedlings to survive. Finally, only savanna seedlings responded to shading. Although results were consistent with the classification of our species as mostly adapted to shade tolerance, competition for light in the open, and fire tolerance, they raised new questions: how could savanna seedlings survive better with a 10-times lower biomass than forest seedlings? Is their shade intolerance sufficient to exclude them from forest understory?
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Těšitel, Jakub; Lepš, Jan; Vráblová, Martina; Cameron, Duncan D
2011-10-01
• Heterotrophic acquisition of substantial amounts of organic carbon by hemiparasitic plants was clearly demonstrated by numerous studies. Many hemiparasites are, however, also limited by competition for light preventing the establishment of their populations on highly productive sites. • In a growth-chamber experiment, we investigated the effects of competition for light, simulated by shading, on growth and heterotrophic carbon acquisition by the hemiparasite Rhinanthus alectorolophus attached to C(3) and C(4) hosts using analyses of biomass production and stable isotopes of carbon. • Shading had a detrimental effect on biomass production and vertical growth of the hemiparasites shaded from when they were seedlings, while shading imposed later caused only a moderate decrease of biomass production and had no effect on the height. Moreover, shading increased the proportion of host-derived carbon in hemiparasite biomass (up to 50% in shaded seedlings). • These results demonstrate that host-derived carbon can play a crucial role in carbon budget of hemiparasites, especially if they grow in a productive environment with intense competition for light. The heterotrophic carbon acquisition can allow hemiparasite establishment in communities of moderate productivity, helping well-attached hemiparasites to escape from the critical seedling stage. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.
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Fadil, Mouhcine; Farah, Abdellah; Ihssane, Bouchaib; Haloui, Taoufik; Lebrazi, Sara; Zghari, Badreddine; Rachiq, Saâd
2016-01-01
To investigate the effect of environmental factors such as light and shade on essential oil yield and morphological traits of Moroccan Myrtus communis, a chemometric study was conducted on 20 individuals growing under two contrasting light environments. The study of individual's parameters by principal component analysis has shown that essential oil yield, altitude, and leaves thickness were positively correlated between them and negatively correlated with plants height, leaves length and leaves width. Principal component analysis and hierarchical cluster analysis have also shown that the individuals of each sampling site were grouped separately. The one-way ANOVA test has confirmed the effect of light and shade on essential oil yield and morphological parameters by showing a statistically significant difference between them from the shaded side to the sunny one. Finally, the multiple linear model containing main, interaction and quadratic terms was chosen for the modeling of essential oil yield in terms of morphological parameters. Sun plants have a small height, small leaves length and width, but they are thicker and richer in essential oil than shade plants which have shown almost the opposite. The highlighted multiple linear model can be used to predict essential oil yield in the studied area.
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NASA Astrophysics Data System (ADS)
Browne, Nicola K.; Yaakub, Siti Maryam; Tay, Jason K. L.; Todd, Peter A.
2017-12-01
Elevated sediment delivery and resuspension in coastal waters from human activities such as shipping can have detrimental effects on seagrass health by limiting light penetration. Managing seagrasses requires knowledge of their light acclamatory abilities so guidelines for coastal activities (e.g. ship movements) that influence sediment dynamics can be created. Guidelines typically focus on ensuring that seagrasses are able to meet their minimal light requirements (MLR). MLRs can be achieved by different light regimes, but it remains unknown whether a chronically low yet stable light regime is less or more detrimental than a highly variable regime with periods of extreme low to no light. To test this, we compared the physiological and morphological responses of Thalassia hemprichii among three light regimes: an open control (30-40% ambient light), a shaded control with (11-15% ambient light), and a fluctuating shade (4-30% ambient light). The MLR for the T. hemprichii we studied was lower (4-10% ambient light) than previous reports (mean = 18%) illustrating enhanced light acclimation in Singapore's chronically turbid waters. Seagrass shoots in the shaded control, however, exhibited significantly more morphological stress symptoms, with reduced shoot growth and lower below ground biomass. These data suggest that for seagrass exposed to periods of acute light stress, energetic costs associated with photo-acclimation to more variable light regimes can be offset if the plant can meet its daily light requirements during periods of high light. Management of seagrass beds should incorporate regular light monitoring and move towards an adaptive feedback-based approach to ensure the long-term viability of these vulnerable ecosystems.
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Siminovitch, Michael J.; Page, Erik R.
2002-01-01
A double lamp table or floor lamp lighting system has a pair of compact fluorescent lamps (CFLs) or other lamps arranged vertically, i.e. one lamp above the other, with a reflective septum in between. By selectively turning on one or both of the CFLs, down lighting, up lighting, or both up and down lighting is produced. The control system can also vary the light intensity from each CFL. The reflective septum ensures that almost all the light produced by each lamp will be directed into the desired light distribution pattern which is selected and easily changed by the user. In a particular configuration, the reflective septum is bowl shaped, with the upper CFL sitting in the bowl, and a luminous shade hanging down from the bowl. The lower CFL provides both task lighting and uniform shade luminance. Planar compact fluorescent lamps, e.g. circular CFLs, particularly oriented horizontally, are preferable. CFLs provide energy efficiency. However, other types of lamps, including incandescent, halogen, and LEDs can also be used in the fixture. The lighting system may be designed for the home, hospitality, office or other environments.
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NASA Astrophysics Data System (ADS)
Magney, T. S.; Griffin, K. L.; Boelman, N.; Eitel, J.; Greaves, H.; Prager, C.; Logan, B.; Oliver, R.; Fortin, L.; Vierling, L. A.
2014-12-01
Because changes in vegetation structure and function in the Arctic are rapid and highly dynamic phenomena, efforts to understand the C balance of the tundra require repeatable, objective, and accurate remote sensing methods for estimating aboveground C pools and fluxes over large areas. A key challenge addressing the modelling of aboveground C is to utilize process-level information from fine-scale studies. Utilizing information obtained from high resolution remote sensing systems could help to better understand the C source/sink strength of the tundra, which will in part depend on changes in photosynthesis resulting from the partitioning of photosynthetic machinery within and among deciduous shrub canopies. Terrestrial LiDAR and passive hyperspectral remote sensing measurements offer an effective, repeatable, and scalable method to understand photosynthetic performance and partitioning at the canopy scale previously unexplored in arctic systems. Using a 3-D shrub canopy model derived from LiDAR, we quantified the light regime of leaves within shrub canopies to gain a better understanding of how light interception varies in response to the Arctic's complex radiation regime. This information was then coupled with pigment sampling (i.e., xanthophylls, and Chl a/b) to evaluate the optimization of foliage photosynthetic capacity within shrub canopies due to light availability. In addition, a lab experiment was performed to validate evidence of canopy level optimization via gradients of light intensity and leaf light environment. For this, hyperspectral reflectance (photochemical reflectance index (PRI)), and solar induced fluorescence (SIF)) was collected in conjunction with destructive pigment samples (xanthophylls) and chlorophyll fluorescence measurements in both sunlit and shaded canopy positions.
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Lima, Vandimilli A; Pacheco, Fernanda V; Avelar, Rafaella P; Alvarenga, Ivan C A; Pinto, José Eduardo B P; Alvarenga, Amauri A DE
2017-01-01
Piper hispidinervum C. DC. is popularly known as long-pepper and it owns a commercial value due to the essential oil it produces. Long-pepper oil is rich in safrole and eugenoln components that have insecticidal, fungicidal and bactericidal activity. It has been establish that to medicinal plants light influences not only growth but also essential oil production. The growth, the content of photosynthetic pigments and the essential oil production of Piper hispidinervum at greenhouses with different light conditions was evaluated. The treatments were characterized by cultivation of plants for 180 days under different light conditions, produced by shading greenhouses with 50% and 30% of natural incident irradiance, two colored shading nets red (RN) and blue (BN) both blocking 50% of the incident radiation and one treatment at full-sun (0% of shade). The results showed that the treatments of 50% shade and RN and BN were the ones which stimulated the greater growth. Blue and red light also had the best production of photosynthetic pigments. Essential oil yielded more under full sun therefore this is the most indicated condition to produce seedlings for the chemical and pharmaceutical industry.
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Latty, Tanya; Beekman, Madeleine
2010-01-01
How individuals deal with multiple conflicting demands is an important aspect of foraging ecology, yet work on foraging behavior has typically neglected neurologically simple organisms. Here we examine the impact of an abiotic risk (light) and energetic status on the foraging decisions of a protist, the slime mold Physarum polycephalum. We examined patch choice in a "non-risky" environment by presenting starved and non-starved P. polycephalum amoebas with a choice between two shaded food patches (one high quality, one low quality). We next examined patch choice in the presence of a conflict between foraging risk (light exposure) and food quality by presenting amoebas with a choice between a shaded, low-quality patch, and a light-exposed, high-quality patch. When both patches were shaded, 100% of amoebas selected the higher quality food patch, irrespective of food-quality differences or the individual's energetic status. When light exposure and food quality conflicted, amoebas selected the patch with the higher food quality when the quality difference between the patches was high. When the quality difference between patches was small, amoebas selected the shaded, lower quality patch.
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Shade effects on growth, flowering, and fruit of apple
USDA-ARS?s Scientific Manuscript database
Light is a critical resource needed by plants for growth and reproduction. A major portion of the apple (Malus xdomestica Borkh.) tree’s canopy is subjected to shade during most daylight hours each day and such shade may affect productivity. The current research determined effects of morning, afte...
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ERIC Educational Resources Information Center
Cook, Robert G.; Qadri, Muhammad A. J.; Kieres, Art; Commons-Miller, Nicholas
2012-01-01
Light is the origin of vision. The pattern of shading reflected from object surfaces is one of several optical features that provide fundamental information about shape and surface orientation. To understand how surface and object shading is processed by birds, six pigeons were tested with differentially illuminated convex and concave curved…
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Effects of shading on starch pasting characteristics of indica hybrid rice (Oryza sativa L.).
Wang, Li; Deng, Fei; Ren, Wan-Jun; Yang, Wen-Yu
2013-01-01
Rice is an important staple crop throughout the world, but environmental stress like low-light conditions can negatively impact crop yield and quality. Using pot experiments and field experiments, we studied the effects of shading on starch pasting viscosity and starch content with six rice varieties for three years, using the Rapid Visco Analyser to measure starch pasting viscosity. Shading at different growth stages and in different rice varieties all affected the starch pasting characteristics of rice. The effects of shading on starch pasting viscosity at middle and later growth stages were greater than those at earlier stages. Shading enhanced breakdown but reduced hold viscosity and setback at tillering-elongation stage. Most pasting parameters changed significantly with shading after elongation stage. Furthermore, the responses of different varieties to shading differed markedly. The change scope of starch pasting viscosity in Dexiang 4103 was rather small after heading, while that in IIyou 498 and Gangyou 906 was small before heading. We observed clear tendencies in peak viscosity, breakdown, and pasting temperature of the five rice varieties with shading in 2010 and 2011. Correlation analysis indicated that the rice amylose content was negatively correlated with breakdown, but was positively correlated with setback. Based on our results, IIyou 498, Gangyou 906, and Dexiang 4103 had higher shade endurance, making these varieties most suitable for high-quality rice cultivation in low-light regions.
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Effects of Shading on Starch Pasting Characteristics of Indica Hybrid Rice (Oryza sativa L.)
Ren, Wan-Jun; Yang, Wen-Yu
2013-01-01
Rice is an important staple crop throughout the world, but environmental stress like low-light conditions can negatively impact crop yield and quality. Using pot experiments and field experiments, we studied the effects of shading on starch pasting viscosity and starch content with six rice varieties for three years, using the Rapid Visco Analyser to measure starch pasting viscosity. Shading at different growth stages and in different rice varieties all affected the starch pasting characteristics of rice. The effects of shading on starch pasting viscosity at middle and later growth stages were greater than those at earlier stages. Shading enhanced breakdown but reduced hold viscosity and setback at tillering-elongation stage. Most pasting parameters changed significantly with shading after elongation stage. Furthermore, the responses of different varieties to shading differed markedly. The change scope of starch pasting viscosity in Dexiang 4103 was rather small after heading, while that in IIyou 498 and Gangyou 906 was small before heading. We observed clear tendencies in peak viscosity, breakdown, and pasting temperature of the five rice varieties with shading in 2010 and 2011. Correlation analysis indicated that the rice amylose content was negatively correlated with breakdown, but was positively correlated with setback. Based on our results, IIyou 498, Gangyou 906, and Dexiang 4103 had higher shade endurance, making these varieties most suitable for high-quality rice cultivation in low-light regions. PMID:23861872
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Jiang, Chuang-Dao; Wang, Xin; Gao, Hui-Yuan; Shi, Lei; Chow, Wah Soon
2011-03-01
Leaf anatomy of C3 plants is mainly regulated by a systemic irradiance signal. Since the anatomical features of C4 plants are different from that of C3 plants, we investigated whether the systemic irradiance signal regulates leaf anatomical structure and photosynthetic performance in sorghum (Sorghum bicolor), a C4 plant. Compared with growth under ambient conditions (A), no significant changes in anatomical structure were observed in newly developed leaves by shading young leaves alone (YS). Shading mature leaves (MS) or whole plants (S), on the other hand, caused shade-leaf anatomy in newly developed leaves. By contrast, chloroplast ultrastructure in developing leaves depended only on their local light conditions. Functionally, shading young leaves alone had little effect on their net photosynthetic capacity and stomatal conductance, but shading mature leaves or whole plants significantly decreased these two parameters in newly developed leaves. Specifically, the net photosynthetic rate in newly developed leaves exhibited a positive linear correlation with that of mature leaves, as did stomatal conductance. In MS and S treatments, newly developed leaves exhibited severe photoinhibition under high light. By contrast, newly developed leaves in A and YS treatments were more resistant to high light relative to those in MS- and S-treated seedlings. We suggest that (1) leaf anatomical structure, photosynthetic capacity, and high-light tolerance in newly developed sorghum leaves were regulated by a systemic irradiance signal from mature leaves; and (2) chloroplast ultrastructure only weakly influenced the development of photosynthetic capacity and high-light tolerance. The potential significance of the regulation by a systemic irradiance signal is discussed.
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Excess diffuse light absorption in upper mesophyll limits CO2 drawdown and depresses photosynthesis
USDA-ARS?s Scientific Manuscript database
Sun-grown and shade-grown leaves of some species absorb direct and diffuse light differently. Sun-grown leaves can photosynthesize ~10-15% less under diffuse compared to direct irradiance, while shade-grown leaves do not exhibit this sensitivity. In this study, we investigate if the spatial differen...
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Photoacclimation supports environmental tolerance of a sponge to turbid low-light conditions
NASA Astrophysics Data System (ADS)
Biggerstaff, A.; Smith, D. J.; Jompa, J.; Bell, J. J.
2015-12-01
Changes to coral reefs are occurring worldwide, often resulting in declining environmental quality which can be in the form of higher sedimentation rates and increased turbidity. While environmental acclimation to turbid and low-light conditions has been extensively studied in corals, far less is known about other phototrophic reef invertebrates. The photosynthetic cyanobacteria containing sponge Lamellodysidea herbacea is one of the most abundant sponges in the Wakatobi Marine National Park (WMNP, Indonesia), and its abundance is greatest at highly disturbed, turbid sites. This study investigated photoacclimation of L. herbacea symbionts to turbid reef sites using in situ PAM fluorometry combined with shading and transplant experiments at environmental extremes of light availability for this species. We found in situ photoacclimation of L. herbacea to both shallow, clear, high-light environments and deep, turbid, low-light environments. Shading experiments provide some evidence that L. herbacea are dependent on nutrition from their photosymbionts as significant tissue loss was seen in shaded sponges. Symbionts within surviving shaded tissue showed evidence of photoacclimation. Lamellodysidea herbacea transplanted from high- to low-light conditions appeared to have photoacclimated within 5 d with no significant effect of the lowered light level on survival. This ability of L. herbacea to photoacclimate to rapid and extreme changes in light availability may be one of the factors contributing to their survival on more turbid reef sites in the WMNP. Our study highlights the ability of some sponge species to acclimate to changes in light levels as a result of increased turbidity.
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Detecting Subtle Shifts in Ecosystem Functioning in a Dynamic Estuarine Environment
Pratt, Daniel R.; Lohrer, Andrew M.; Thrush, Simon F.; Hewitt, Judi E.; Townsend, Michael; Cartner, Katie; Pilditch, Conrad A.; Harris, Rachel J.; van Colen, Carl; Rodil, Iván F.
2015-01-01
Identifying the effects of stressors before they impact ecosystem functioning can be challenging in dynamic, heterogeneous ‘real-world’ ecosystems. In aquatic systems, for example, reductions in water clarity can limit the light available for photosynthesis, with knock-on consequences for secondary consumers, though in naturally turbid wave-swept estuaries, detecting the effects of elevated turbidity can be difficult. The objective of this study was to investigate the effects of shading on ecosystem functions mediated by sandflat primary producers (microphytobenthos) and deep-dwelling surface-feeding macrofauna (Macomona liliana; Bivalvia, Veneroida, Tellinidae). Shade cloths (which reduced incident light intensity by ~80%) were deployed on an exposed, intertidal sandflat to experimentally stress the microphytobenthic community associated with the sediment surface. After 13 weeks, sediment properties, macrofauna and fluxes of oxygen and inorganic nutrients across the sediment-water interface were measured. A multivariate metric of ecosystem function (MF) was generated by combining flux-based response variables, and distance-based linear models were used to determine shifts in the drivers of ecosystem function between non-shaded and shaded plots. No significant differences in MF or in the constituent ecosystem function variables were detected between the shaded and non-shaded plots. However, shading reduced the total explained variation in MF (from 64% in non-shaded plots to 15% in shaded plots) and affected the relative influence of M. liliana and other explanatory variables on MF. This suggests that although shade stress may shift the drivers of ecosystem functioning (consistent with earlier investigations of shading effects on sandflat interaction networks), ecosystem functions appear to have a degree of resilience to those changes. PMID:26214854
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Munguía-Rosas, Miguel A.; Campos-Navarrete, María J.; Parra-Tabla, Víctor
2013-01-01
Dimorphic cleistogamy is a specialized form of mixed mating system where a single plant produces both open, potentially outcrossed chasmogamous (CH) and closed, obligately self-pollinated cleistogamous (CL) flowers. Typically, CH flowers and seeds are bigger and energetically more costly than those of CL. Although the effects of inbreeding and floral dimorphism are critical to understanding the evolution and maintenance of cleistogamy, these effects have been repeatedly confounded. In an attempt to separate these effects, we compared the performance of progeny derived from the two floral morphs while controlling for the source of pollen. That is, flower type and pollen source effects were assessed by comparing the performance of progeny derived from selfed CH vs. CL and outcrossed CH vs. selfed CH flowers, respectively. The experiment was carried out with the herb Ruellia nudiflora under two contrasting light environments. Outcrossed progeny generally performed better than selfed progeny. However, inbreeding depression ranges from low (1%) to moderate (36%), with the greatest value detected under shaded conditions when cumulative fitness was used. Although flower type generally had less of an effect on progeny performance than pollen source did, the progeny derived from selfed CH flowers largely outperformed the progeny from CL flowers, but only under shaded conditions and when cumulative fitness was taken into account. On the other hand, the source of pollen and flower type influenced seed predation, with selfed CH progeny the most heavily attacked by predators. Therefore, the effects of pollen source and flower type are environment-dependant and seed predators may increase the genetic differences between progeny derived from CH and CL flowers. Inbreeding depression alone cannot account for the maintenance of a mixed mating system in R. nudiflora and other unidentified mechanisms must thus be involved. PMID:24260515
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Modrzyński, Jerzy; Chmura, Daniel J; Tjoelker, Mark G
2015-08-01
Initial growth of germinated seeds is an important life history stage, critical for establishment and succession in forests. Important questions remain regarding the differences among species in early growth potential arising from shade tolerance. In addition, the role of leaf habit in shaping relationships underlying shade tolerance-related differences in seedling growth remains unresolved. In this study we examined variation in morphological and physiological traits among seedlings of 10 forest tree species of the European temperate zone varying in shade tolerance and leaf habit (broadleaved winter-deciduous species vs needle-leaved conifers) during a 10-week period. Seeds were germinated and grown in a controlled environment simulating an intermediate forest understory light environment to resolve species differences in initial growth and biomass allocation. In the high-resource experimental conditions during the study, seedlings increased biomass allocation to roots at the cost of leaf biomass independent of shade tolerance and leaf habit. Strong correlations between relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA) and leaf mass fraction (LMF) indicate that physiology and biomass allocation were equally important determinants of RGR as plant structure and leaf morphology among these species. Our findings highlight the importance of seed mass- and seed size-related root morphology (specific root length-SRL) for shade tolerance during early ontogeny. Leaf and plant morphology (SLA, LAR) were more successful in explaining variation among species due to leaf habit than shade tolerance. In both broadleaves and conifers, shade-tolerant species had lower SRL and greater allocation of biomass to stems (stem mass fraction). Light-seeded shade-intolerant species with greater SRL had greater RGR in both leaf habit groups. However, the greatest plant mass was accumulated in the group of heavy-seeded shade-tolerant broadleaves. The results of our study suggest that the combinations of plant attributes enhancing growth under high light vary with shade tolerance, but differ between leaf habit groups. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Corcodel, N; Rammelsberg, P; Jakstat, H; Moldovan, O; Schwarz, S; Hassel, A J
2010-11-01
Visual tooth colour assessment by use of the Vita 3D-Master(®) (3D; Vita Zahnfabrik, Bad Säckingen, Germany) is well documented. To improve handling, a new linear arrangement of the shade tabs has been introduced (LG; Linearguide 3D-Master(®) ). The purpose of this study was to investigate whether the linear design has an effect on shade matching. Fifty-six students underwent identical, theoretical and practical training, by use of an Internet learning module [Toothguide Training Software(®) (TT)] and a standardised training programme [Toothguide Training Box(®) (TTB)]. Each student then matched 30 randomly chosen shade tabs presented in an intra-oral setting by a standardised device [Toothguide Check Box(®) (TCB)]; 15 matches were made using the 3D and 15 using the LG shade guide system, under a daylight lamp (840 matches for each guide). It was recorded to what extent the presented and selected shade tabs, or the lightness group of the tabs, matched, also the needed time for colour matching. The results showed that 35% of perfect matches were observed for the 3D and 32% for the LG. The lightness group was correct in 59% of cases for 3D and 56% for LG. Mean time needed for matching of tabs and lightness group was no different between groups (no significant difference for any assessment). Within the limitations of the study design, the colour assessment with regard to performance and time needed in shade matching was not different with the LG or the 3D. Therefore, the user should choose which shade tab arrangement is more applicable. © 2010 Blackwell Publishing Ltd.
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Chen, Anping; Lichstein, Jeremy W.; Osnas, Jeanne L. D.; Pacala, Stephen W.
2014-01-01
The ability to down-regulate leaf maximum net photosynthetic capacity (Amax) and dark respiration rate (Rdark) in response to shading is thought to be an important adaptation of trees to the wide range of light environments that they are exposed to across space and time. A simple, general rule that accurately described this down-regulation would improve carbon cycle models and enhance our understanding of how forest successional diversity is maintained. In this paper, we investigated the light response of Amax and Rdark for saplings of six temperate forest tree species in New Jersey, USA, and formulated a simple model of down-regulation that could be incorporated into carbon cycle models. We found that full-sun values of Amax and Rdark differed significantly among species, but the rate of down-regulation (proportional decrease in Amax or Rdark relative to the full-sun value) in response to shade was not significantly species- or taxon-specific. Shade leaves of sun-grown plants appear to follow the same pattern of down-regulation in response to shade as leaves of shade-grown plants. Given the light level above a leaf and one species-specific number (either the full-sun Amax or full-sun Rdark), we provide a formula that can accurately predict the leaf's Amax and Rdark. We further show that most of the down regulation of per unit area Rdark and Amax is caused by reductions in leaf mass per unit area (LMA): as light decreases, leaves get thinner, while per unit mass Amax and Rdark remain approximately constant. PMID:24727745
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Canopy Light Interception of a Conventional and an Erect Leaf Mutant Sorghum
USDA-ARS?s Scientific Manuscript database
Two sorghum lines, an erect leafed mutant sorghum and the wild type from which the mutant was generated, were field grown in rectilinear arrays at low (23 plants per square meter) and high (10 plants per square meter) population densities. Canopy light interception, biomass accretion and yield were ...
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Mundim, F M; Da Fonseca Roberti Garcia, L; Silva Sousa, A B; Cruvinel, D R; De Carvalho Panzeri Pires-De-Souza, F
2010-10-01
The aim of this study was to evaluate the influence of artificial accelerated aging on the color stability and opacity of composites of different shades. Four composites for direct use (Heliomolar, 4 Seasons, Tetric EvoCeram; QuiXfil) and one for indirect use (SR Adoro) in two shades were used: light (A2) and dark (C3 for direct, and D4 for indirect composite). QuiXfil was obtained in Universal shade. A Teflon matrix (12 X 2 mm) was used to obtain 54 specimens (N=6), which were submitted to color and opacity analysis (Spectrophotometer PCB 6807, Byk Gardner) before and after artificial accelerated aging for 384 hours. After the statistical analysis (2-way ANOVA - Bonferroni - P<0.05), significant color alteration was observed in the light and dark composites studied (P<0.05), with the exception of QuiXfil. Composite 4 Seasons/C3 showed less color alteration (ΔE=0.91). The opacity alteration (ΔOP) was higher for light composites. Artificial accelerated aging interfered in the optical properties assessed; however, the alterations seemed to be more related to the composites composition than to their shade.
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Shang, Zhehai; Lee, Zhongping; Dong, Qiang; Wei, Jianwei
2017-09-01
Self-shading associated with a skylight-blocked approach (SBA) system for the measurement of water-leaving radiance (L w ) and its correction [Appl. Opt.52, 1693 (2013)APOPAI0003-693510.1364/AO.52.001693] is characterized by Monte Carlo simulations, and it is found that this error is in a range of ∼1%-20% under most water properties and solar positions. A model for estimating this shading error is further developed, and eventually a scheme to correct this error based on the shaded measurements is proposed and evaluated. It is found that the shade-corrected value in the visible domain is within 3% of the true value, which thus indicates that we can obtain not only high precision but also high accuracy L w in the field with the SBA scheme.
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Douglas-fir in northern California: effects of shade on germination, survival, and growth
Rudolph O. Strothmann
1972-01-01
Effects of four light intensities on germination, survival, and early growth of Douglas-fir (Pseudotsuga menziesii) were studied on south-facing cutblocks in northwestern California. Tested were four shade intensities: 0, 25, 50, and 75 percent. On seeded spots, 50 percent shade resulted in greatest germination and survival, being significantly...
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Zhu, Hongfang; Li, Xiaofeng; Zhai, Wen; Liu, Yang; Gao, Qianqian; Liu, Jinping; Ren, Li; Chen, Huoying; Zhu, Yuying
2017-01-01
Anthocyanins are secondary metabolites that contribute to red, blue, and purple colors in plants and are affected by light, but the effects of low light on the physiological responses of purple pak-choi plant leaves are still unclear. In this study, purple pak-choi seedlings were exposed to low light by shading with white gauze and black shading in a phytotron. The responses in terms of photosynthetic properties, carbohydrate metabolism, antioxidant enzyme activity, anthocyanin biosynthetic enzyme activity, and the relative chlorophyll and anthocyanin content of leaves were measured. The results showed that chlorophyll b, intracellular CO2 content, stomatal conductance and antioxidant activities of guaiacol peroxidase, catalase and superoxide dismutase transiently increased in the shade treatments at 5 d. The malondialdehyde content also increased under low light stress, which damages plant cells. With the extension of shading time (at 15 d), the relative chlorophyll a, anthocyanin and soluble protein contents, net photosynthetic rate, transpiration rate, stomata conductance, antioxidant enzyme activities, and activities of four anthocyanin biosynthetic enzymes decreased significantly. Thus, at the early stage of low light treatment, the chlorophyll b content increased to improve photosynthesis. When the low light treatment was extended, antioxidant enzyme activity and the activity of anthocyanin biosynthesis enzymes were inhibited, causing the purple pak-choi seedlings to fade from purple to green. This study provides valuable information for further deciphering genetic mechanisms and improving agronomic traits in purple pak-choi under optimal light requirements.
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Carbon allocation to growth and storage in two evergreen species of contrasting successional status.
Piper, Frida I; Sepúlveda, Paulina; Bustos-Salazar, Angela; Zúñiga-Feest, Alejandra
2017-05-01
A prevailing hypothesis in forest succession is that shade-tolerant species grow more slowly than shade-intolerant species, across light conditions, because they prioritize carbon (C) allocation to storage. We examined this hypothesis in a confamilial pair of species, including one of the fastest-growing tree species in the world ( Eucalyptus globulus ) and a shade-tolerant, slow-growing species ( Luma apiculata ). Seedlings were subjected to one out of four combinations of light (high vs. low) and initial defoliation (90% defoliated vs. nondefoliated) for four months. Growth, C storage concentration in different organs, leaf shedding, and lateral shoot formation were measured at the end of the experiment. Eucalyptus globulus grew faster than L. apiculata in high light, but not in low light. Both species had lower C storage concentration in low than in high light, but similar C storage concentrations in each light condition. Defoliation had no effect on C storage, except in the case of the old leaves of both species, which showed lower C storage levels in response to defoliation. Across treatments, leaf shedding was 96% higher in E. globulus than in L. apiculata while, in contrast, lateral shoot formation was 87% higher in L. apiculata . In low light, E. globulus prioritized C storage instead of growth, whereas L. apiculata prioritized growth and lateral branching. Our results suggest that shade tolerance depends on efficient light capture rather than C conservation traits. © 2017 Botanical Society of America.
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USDA-ARS?s Scientific Manuscript database
Plant response to blue, red, gray or black shade cloth was evaluated with willow oak (Quercus phellos L.), Nuttall oak (Quercus nuttallii Palmer, Nuttall) and Summer Red maple (Acer rubrum L. ‘Summer Red’) liners. Light transmitted through the colored shade cloth had no influence on germination of ...
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The use of light in prey capture by the tropical pitcher plant Nepenthes aristolochioides.
Moran, Jonathan A; Clarke, Charles; Gowen, Brent E
2012-08-01
Nepenthes pitcher plants deploy tube-shaped pitchers to catch invertebrate prey; those of Nepenthes aristolochioides possess an unusual translucent dome. The hypothesis was tested that N. aristolochioides pitchers operate as light traps, by quantifying prey capture under three shade treatments. Flies are red-blind, with visual sensitivity maxima in the UV, blue, and green wavebands. Red celluloid filters were used to reduce the transmission of these wavebands into the interior of the pitchers. Those that were shaded at the rear showed a 3-fold reduction in Drosophila caught, relative to either unshaded control pitchers, or pitchers that were shaded at the front. Thus, light transmitted through the translucent dome is a fundamental component of N. aristolochioides' trapping mechanism.
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The use of light in prey capture by the tropical pitcher plant Nepenthes aristolochioides
Moran, Jonathan A.; Clarke, Charles; Gowen, Brent E.
2012-01-01
Nepenthes pitcher plants deploy tube-shaped pitchers to catch invertebrate prey; those of Nepenthes aristolochioides possess an unusual translucent dome. The hypothesis was tested that N. aristolochioides pitchers operate as light traps, by quantifying prey capture under three shade treatments. Flies are red-blind, with visual sensitivity maxima in the UV, blue, and green wavebands. Red celluloid filters were used to reduce the transmission of these wavebands into the interior of the pitchers. Those that were shaded at the rear showed a 3-fold reduction in Drosophila caught, relative to either unshaded control pitchers, or pitchers that were shaded at the front. Thus, light transmitted through the translucent dome is a fundamental component of N. aristolochioides' trapping mechanism. PMID:22836498
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Chen, Ji; Lv, Fengjuan; Liu, Jingran; Ma, Yina; Wang, Youhua; Chen, Binglin; Meng, Yali; Zhou, Zhiguo; Oosterhuis, Derrick M.
2014-01-01
Cotton-rapeseed or cotton-wheat double cropping systems are popular in the Yangtze River Valley and Yellow River Valley of China. Due to the competition of temperature and light resources during the growing season of double cropping system, cotton is generally late-germinating and late-maturing and has to suffer from the coupling of declining temperature and low light especially in the late growth stage. In this study, late planting (LP) and shading were used to fit the coupling stress, and the coupling effect on fiber cellulose synthesis was investigated. Two cotton (Gossypium hirsutum L.) cultivars were grown in the field in 2010 and 2011 at three planting dates (25 April, 25 May and 10 June) each with three shading levels (normal light, declined 20% and 40% PAR). Mean daily minimum temperature was the primary environmental factor affected by LP. The coupling of LP and shading (decreased cellulose content by 7.8%–25.5%) produced more severe impacts on cellulose synthesis than either stress alone, and the effect of LP (decreased cellulose content by 6.7%–20.9%) was greater than shading (decreased cellulose content by 0.7%–5.6%). The coupling of LP and shading hindered the flux from sucrose to cellulose by affecting the activities of related cellulose synthesis enzymes. Fiber cellulose synthase genes expression were delayed under not only LP but shading, and the coupling of LP and shading markedly postponed and even restrained its expression. The decline of sucrose-phosphate synthase activity and its peak delay may cause cellulose synthesis being more sensitive to the coupling stress during the later stage of fiber secondary wall development (38–45 days post-anthesis). The sensitive difference of cellulose synthesis between two cultivars in response to the coupling of LP and shading may be mainly determined by the sensitiveness of invertase, sucrose-phosphate synthase and cellulose synthase. PMID:25133819
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Automated analysis of hypocotyl growth dynamics during shade avoidance in Arabidopsis.
Cole, Benjamin; Kay, Steve A; Chory, Joanne
2011-03-01
Plants that are adapted to environments where light is abundant are especially sensitive to competition for light from neighboring vegetation. As a result, these plants initiate a series of changes known as the shade avoidance syndrome, during which plants elongate their stems and petioles at the expense of leaf development. Although the developmental outcomes of exposure to prolonged shade are known, the signaling dynamics during the initial exposure of seedlings to shade is less well studied. Here, we report the development of a new software-based tool, called HyDE (Hypocotyl Determining Engine) to measure hypocotyl lengths of time-resolved image stacks of Arabidopsis wild-type and mutant seedlings. We show that Arabidopsis grows rapidly in response to the shade stimulus, with measurable growth after just 45 min shade exposure. Similar to other mustard species, this growth response occurs in multiple distinct phases, including two phases of rapid growth and one phase of slower growth. Using mutants affected in shade avoidance phenotypes, we demonstrate that most of this early growth requires new auxin biosynthesis via the indole-3-pyruvate pathway. When activity of this pathway is reduced, the first phase of elongation growth is absent, and this is correlated with reduced activity of auxin-regulated genes. Finally, we show that varying shade intensity and duration can affect the shape and magnitude of the growth response, indicating a broad range of the elongation response to shade. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.
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Arroyo-Pérez, Erika; González-Salvatierra, Claudia; Matías-Palafox, María L.; Jiménez-Sierra, Cecilia
2017-01-01
Abstract We determined the seasonal ecophysiological performance under perennial plants and under high solar radiation for adult individuals from the ‘living rock’ cactus Ariocarpus kotschoubeyanus, which occurs equally under nurse plants and in open spaces. We evaluated the effective quantum yield of photosystem II (ΦPSII) and the dissipation of thermal energy [non-photochemical quenching (NPQ)] thorough the year. The maximum apparent electron transport rate (ETRmax) and the saturating photosynthetically active photon flux density for PSII (PFDsat) were also determined from rapid light curves. We found that although the ΦPSII was higher in shaded sites under potential nurse plants than in exposed sites, all values were close to the optimal value of 0.83. The high ΦPSII found for A. kotschoubeyanus plants suggests that they use a great proportion of the absorbed light for photosynthesis, under nurse plants as well as in open spaces. We also found higher NPQ values in exposed sites than in shaded ones but only in Autumn, thus reducing the risk of photoinhibition. In addition, the PFDsat was higher in exposed sites than in shaded ones in Spring, Summer and Autumn, but in Winter there were no differences between treatments. We also found high saturating light levels for ETR (PFDsat higher than 1378 μmol m−2 s−1) in all seasons but in winter for shaded and non-shaded plants. Our findings indicate that A. kotschoubeyanus plants use a great proportion of the light that they absorb for photosynthesis. This high tolerance to high-light conditions could explain why A. kotschoubeyanus do not show preferences for protected sites under nurse plants. PMID:28729902
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Season-dependent and independent responses of Mediterranean scrub to light conditions.
Zunzunegui, María; Díaz-Barradas, Mari Cruz; Jáuregui, Juan; Rodríguez, Herminia; Álvarez-Cansino, Leonor
2016-05-01
Semi-arid plant species cope with excess of solar radiation with morphological and physiological adaptations that assure their survival when other abiotic stressors interact. At the leaf level, sun and shade plants may differ in the set of traits that regulate environmental stressors. Here, we evaluated if leaf-level physiological seasonal response of Mediterranean scrub species (Myrtus communis, Halimium halimifolium, Rosmarinus officinalis, and Cistus salvifolius) depended on light availability conditions. We aimed to determine which of these responses prevailed independently of the marked seasonality of Mediterranean climate, to define a leaf-level strategy in the scrub community. Thirty six leaf response variables - involving gas exchange, water status, photosystem II photochemical efficiency, photosynthetic pigments and leaf structure - were seasonally measured in sun exposed and shaded plants under field conditions. Physiological responses showed a common pattern throughout the year, in spite of the marked seasonality of the Mediterranean climate and of species-specific differences in the response to light intensity. Variables related to light use, CO2 assimilation, leaf pigment content, and LMA (leaf mass area) presented differences that were consistent throughout the year, although autumn was the season with greater contrast between sun and shade plants. Our data suggest that in Mediterranean scrub shade plants the lutein pool could have an important role in the photoprotection of the photosynthetic tissues. There was a negative linear correlation between the ratio lutein/total chlorophylls and the majority of leaf level variables. The combined effect of abiotic stress factors (light and drought or light and cold) was variable-specific, in some cases enhancing differences between sun and shade plants, while in others leading to unified strategies in all scrub species. Copyright © 2016 Elsevier Masson SAS. All rights reserved.
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Al-Dwairi, Ziad; Shaweesh, Ashraf; Kamkarfar, Sohrab; Kamkarfar, Shahrzad; Borzabadi-Farahani, Ali; Lynch, Edward
2014-01-01
The purpose of this study was to examine the relationship between skin color (shade) and tooth shade under standard and nonstandard illumination sources. Four hundred Jordanian participants (200 males, 200 females, 20 to 50 years of age) were studied. Skin colors were assessed and categorized using the L'Oreal and Revlon foundation shade guides (light, medium, dark). The Vita Pan Classical Shade Guide (VPCSG; Vident) and digital Vita EasyShade Intraoral Dental Spectrophotometer (VESIDS; Vident) were used to select shades in the middle thirds of maxillary central incisors; tooth shades were classified into four categories (highest, high, medium, low). Significant gender differences were observed for skin colors (P = .000) and tooth shade guide systems (P = .001 and .050 for VPCSG and VESIDS, respectively). The observed agreement was 100% and 93% for skin and tooth shade guides, respectively. The corresponding kappa statistic values were 1.00 and 0.79, respectively (substantial agreement, P < .001). The observed agreement between skin color and tooth shades (VPCSG and VESIDS) was approximately 50%. The digital tooth shade guide system can be a satisfactory substitute for classical tooth shade guides and clinical shade matching. There was only moderate agreement between skin color and tooth shade.
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Zimmer, Heidi C.; Offord, Catherine A.; Auld, Tony D.; Baker, Patrick J.
2016-01-01
Translocation can reduce extinction risk by increasing population size and geographic range, and is increasingly being used in the management of rare and threatened plant species. A critical determinant of successful plant establishment is light environment. Wollemia nobilis (Wollemi pine) is a critically endangered conifer, with a wild population of 83 mature trees and a highly restricted distribution of less than 10 km2. We used under-planting to establish a population of W. nobilis in a new rainforest site. Because its optimal establishment conditions were unknown, we conducted an experimental translocation, planting in a range of different light conditions from deeply shaded to high light gaps. Two years after the experimental translocation, 85% of plants had survived. There were two distinct responses: very high survival (94%) but very low growth, and lower survival (69%) and higher growth, associated with initial plant condition. Overall survival of translocated W. nobilis was strongly increased in planting sites with higher light, in contrast to previous studies demonstrating long-term survival of wild W. nobilis juveniles in deep shade. Translocation by under-planting may be useful in establishing new populations of shade-tolerant plant species, not least by utilizing the range of light conditions that occur in forest understories. PMID:27403527
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Zimmer, Heidi C; Offord, Catherine A; Auld, Tony D; Baker, Patrick J
2016-01-01
Translocation can reduce extinction risk by increasing population size and geographic range, and is increasingly being used in the management of rare and threatened plant species. A critical determinant of successful plant establishment is light environment. Wollemia nobilis (Wollemi pine) is a critically endangered conifer, with a wild population of 83 mature trees and a highly restricted distribution of less than 10 km2. We used under-planting to establish a population of W. nobilis in a new rainforest site. Because its optimal establishment conditions were unknown, we conducted an experimental translocation, planting in a range of different light conditions from deeply shaded to high light gaps. Two years after the experimental translocation, 85% of plants had survived. There were two distinct responses: very high survival (94%) but very low growth, and lower survival (69%) and higher growth, associated with initial plant condition. Overall survival of translocated W. nobilis was strongly increased in planting sites with higher light, in contrast to previous studies demonstrating long-term survival of wild W. nobilis juveniles in deep shade. Translocation by under-planting may be useful in establishing new populations of shade-tolerant plant species, not least by utilizing the range of light conditions that occur in forest understories.
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NASA Technical Reports Server (NTRS)
Chretien, Jean-Loup (Inventor); Lu, Edward T. (Inventor)
2005-01-01
A dynamic optical filtration system and method effectively blocks bright light sources without impairing view of the remainder of the scene. A sensor measures light intensity and position so that selected cells of a shading matrix may interrupt the view of the bright light source by a receptor. A beamsplitter may be used so that the sensor may be located away from the receptor. The shading matrix may also be replaced by a digital micromirror device, which selectively sends image data to the receptor.
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NASA Technical Reports Server (NTRS)
Chretien, Jean-Loup (Inventor); Lu, Edward T. (Inventor)
2005-01-01
A dynamic optical filtration system and method effectively blocks bright light sources without impairing view of the remainder of the scene. A sensor measures light intensity and position so that selected cells of a shading matrix may interrupt the view of the bright light source by a receptor. A beamsplitter may be used so that the sensor may be located away from the receptor. The shading matrix may also be replaced by a digital micromirror device, which selectively sends image data to the receptor.
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Herbivores modify selection on plant functional traits in a temperate rainforest understory.
Salgado-Luarte, Cristian; Gianoli, Ernesto
2012-08-01
There is limited evidence regarding the adaptive value of plant functional traits in contrasting light environments. It has been suggested that changes in these traits in response to light availability can increase herbivore susceptibility. We tested the adaptive value of plant functional traits linked with carbon gain in contrasting light environments and also evaluated whether herbivores can modify selection on these traits in each light environment. In a temperate rainforest, we examined phenotypic selection on functional traits in seedlings of the pioneer tree Aristotelia chilensis growing in sun (canopy gap) and shade (forest understory) and subjected to either natural herbivory or herbivore exclusion. We found differential selection on functional traits depending on light environment. In sun, there was positive directional selection on photosynthetic rate and relative growth rate (RGR), indicating that selection favors competitive ability in a high-resource environment. Seedlings with high specific leaf area (SLA) and intermediate RGR were selected in shade, suggesting that light capture and conservative resource use are favored in the understory. Herbivores reduced the strength of positive directional selection acting on SLA in shade. We provide the first demonstration that natural herbivory rates can change the strength of selection on plant ecophysiological traits, that is, attributes whose main function is resource uptake. Research addressing the evolution of shade tolerance should incorporate the selective role of herbivores.
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Performance of Arrowroot (Marantha arundinacea) in various light intensities
NASA Astrophysics Data System (ADS)
Oktafani, M. B.; Supriyono; Budiastuti, MTh S.; Purnomo, D.
2018-03-01
Arrowroot (Marantha arundinacea) is one of the potential food crops to support food security programs. Light intensity is one of the important factors for plant growth. Arrowroot cultivation technology still need further development. Traditionally, arrowroot grows wild under canopy without intentisification of cultivating which have low productivity. The purpose of research was to investigate the suitable light intensity for arrowroot. The experiment was conducted at Jumantono as Experimental Field of Faculty of Agricultural, University of Sebelas Maret Surakarta located in Karanganyar, from March to September 2016. The experiment used a complete randomized block design (CRBD) of light intensity level there are 27400 lux (full sun light), 18900 lux (shaded 31%), 13500 lux (shaded 51%) and 7400 lux (shaded 72%). Each treatment was replicated six times so there were 24 experimental units. The results showed that arrowroot is a low light adaptive plant. Arrowroot under the light intensity 7400 lux (27% full light), the number of leaves and tillers is not significantly different than under full light, although the plant is higher. The highest tuber diameter and length were 1.91 and 25.06 cm, respectively, and tuber weight reached 607.5-651.67 g per plant.
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NASA Astrophysics Data System (ADS)
Anderson-Smith, A.; Pattison, R.; Sullivan, P.; Welker, J. M.
2009-12-01
Eriophorum vaginatum (Cotton Grass) is an important component of moist acidic tussock tundra, a plant community that appears to be undergoing changes in species composition associated with climate warming. This species is one of the most abundant in the arctic tundra, and provides important forage for caribou in their calving grounds on the Arctic Coastal Plain and along their migratory route through the foothills of Alaska. Recently, remote sensing data, repeat photography and plot-level measurements have indicated that shrub abundance is increasing while Eriophorum abundance is either constant or decreasing. One possible explanation for the reduction of Eriophorum while Betula nana is increasing, is that lower light levels in the taller Betula canopy may be constraining Eriophorum photosynthesis and subsequently reducing plant growth. This study measured the effect of shading on the light response of Eriphorum leaf photosynthesis in four different sites near Toolik Lake Alaska during the summer of 2009. Measurements were taken in: 1) a shrub patch within the drift zone of the ITEX long term snow fence experiment, 2) an LTER shade house (50% shading) built in 1989, 3) water track site 1 and water track site 2 (i.e. control areas with no experimental manipulations) Average photosynthetic rates for Eriophorum at a light level of 800 PAR varied from 3.8 to 10.9 umol m-2 s-1 and were not significantly different in shaded and unshaded areas. This study indicates that shading by shrubs does not appear to be altering the light response of Eriophorum nor does long-term shading by itself eliminate Eriophorum from the community. An alternative explanation for the decline of Eriophorum while Betula increases in abundance under changing climates may be related to plant and soil mineral nutrition, plant water relations or biotic processes involving herbivores.
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Kilkenny, Francis F; Galloway, Laura F
2008-03-01
Plant populations often exist in spatially heterogeneous environments. Light level can directly affect plant reproductive success through resource availability or by altering pollinator behavior. It can also indirectly influence reproductive success by determining floral display size which may in turn influence pollinator attraction. We evaluated direct and indirect effects of light availability and measured phenotypic selection on phenological traits that may enhance pollen receipt in the insect-pollinated herb Campanulastrum americanum. In a natural population, plants in the sun had larger displays and received 7 times more visits than plants in the shade. Using experimental arrays to separate the direct effects of irradiance on insects from their response to display size, we found more visits to plants in the sun than in the shade, but no association between number of visits each flower received and display size. Plants in the sun were not pollen limited but pollen-augmented shade flowers produced 50% more seeds than open-pollinated flowers. Phenological traits, which may influence pollen receipt, were not under direct selection in the sun. However, earlier initiation and a longer duration of flowering were favored in the shade, which may enhance visitation in this pollen-limited habitat.
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Rewiring of auxin signaling under persistent shade.
Pucciariello, Ornella; Legris, Martina; Costigliolo Rojas, Cecilia; Iglesias, María José; Hernando, Carlos Esteban; Dezar, Carlos; Vazquez, Martín; Yanovsky, Marcelo J; Finlayson, Scott A; Prat, Salomé; Casal, Jorge J
2018-05-22
Light cues from neighboring vegetation rapidly initiate plant shade-avoidance responses. Despite our detailed knowledge of the early steps of this response, the molecular events under prolonged shade are largely unclear. Here we show that persistent neighbor cues reinforce growth responses in addition to promoting auxin-responsive gene expression in Arabidopsis and soybean. However, while the elevation of auxin levels is well established as an early event, in Arabidopsis , the response to prolonged shade occurs when auxin levels have declined to the prestimulation values. Remarkably, the sustained low activity of phytochrome B under prolonged shade led to ( i ) decreased levels of PHYTOCHROME INTERACTING FACTOR 4 (PIF4) in the cotyledons (the organs that supply auxin) along with increased levels in the vascular tissues of the stem, ( ii ) elevated expression of the PIF4 targets INDOLE-3-ACETIC ACID 19 ( IAA19 ) and IAA29 , which in turn reduced the expression of the growth-repressive IAA17 regulator, ( iii ) reduced abundance of AUXIN RESPONSE FACTOR 6, ( iv ) reduced expression of MIR393 and increased abundance of its targets, the auxin receptors, and ( v ) elevated auxin signaling as indicated by molecular markers. Mathematical and genetic analyses support the physiological role of this system-level rearrangement. We propose that prolonged shade rewires the connectivity between light and auxin signaling to sustain shade avoidance without enhanced auxin levels.
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Lichtenthaler, Hartmut K; Babani, Fatbardha; Navrátil, Martin; Buschmann, Claus
2013-11-01
The chlorophyll (Chl) fluorescence induction kinetics, net photosynthetic CO2 fixation rates P N, and composition of photosynthetic pigments of differently light exposed leaves of several trees were comparatively measured to determine the differences in photosynthetic activity and pigment adaptation of leaves. The functional measurements were carried out with sun, half-shade and shade leaves of seven different trees species. These were: Acer platanoides L., Ginkgo biloba L., Fagus sylvatica L., Platanus x acerifolia Willd., Populus nigra L., Quercus robur L., Tilia cordata Mill. In three cases (beech, ginkgo, and oak), we compared the Chl fluorescence kinetics and photosynthetic rates of blue-shade leaves of the north tree crown receiving only blue sky light but no direct sunlight with that of sun leaves. In these cases, we also determined in detail the pigment composition of all four leaf types. In addition, we determined the quantum irradiance and spectral irradiance of direct sunlight, blue skylight as well as the irradiance in half shade and full shade. The results indicate that sun leaves possess significantly higher mean values for the net CO2 fixation rates P N (7.8-10.7 μmol CO2 m(-2) s(-1) leaf area) and the Chl fluorescence ratio R Fd (3.85-4.46) as compared to shade leaves (mean P N of 2.6-3.8 μmol CO2 m(-2) s(-1) leaf area.; mean R Fd of 1.94-2.56). Sun leaves also exhibit higher mean values for the pigment ratio Chl a/b (3.14-3.31) and considerably lower values for the weight ratio total chlorophylls to total carotenoids, (a + b)/(x + c), (4.07-4.25) as compared to shade leaves (Chl a/b 2.62-2.72) and (a + b)/(x + c) of 5.18-5.54. Blue-shade and half-shade leaves have an intermediate position between sun and shade leaves in all investigated parameters including the ratio F v/F o (maximum quantum yield of PS2 photochemistry) and are significantly different from sun and shade leaves but could not be differentiated from each other. The mean values of the Chl fluorescence decrease ratio R Fd of blue-shade and half-shade leaves fit well into the strong linear correlation with the net photosynthetic rates P N of sun and shade leaves, thus unequivocally indicating that the determination of the Chl fluorescence decrease ratio R Fd is a fast and indirect measurement of the photosynthetic activity of leaves. The investigations clearly demonstrate that the photosynthetic capacity and pigment composition of leaves and chloroplasts strongly depend on the amounts and quality of light received by the leaves.
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Prevalence of Tooth Shade and its Correlation with Skin Colour - A Cross-sectional Study.
Vadavadagi, Suneel V; Kumari, K V Halini; Choudhury, Gopal Krishna; Vilekar, Abhishek Madhukar; Das, Sitansu Sekhar; Jena, Debkant; Kataraki, Bharat; B L, Bhavana
2016-02-01
Aesthetics has become an important issue in modern society. Tooth shade is one of the factors in determining aesthetics. Studies have revealed that tooth shade is influenced by age, gender, eye colour, skin colour and other factors. The present study was aimed to assess the prevalence of tooth shade and its correlation with skin colour. A total of 300 subjects aged 18-20 years were evaluated for tooth shade using Vitapan - 3D shade guide. Anterior teeth were checked under natural light and facial skin colour by Lakme liquid foundation make up as a shade guide. Data was analysed using chi square test and spearman's correlation. Out of 300 students, 114 (38.00%) had A2 tooth shade; the least prevalent tooth shade among Chitradurga population was C1 (4.00%). There was a positive correlation between tooth shade and skin colour which was found to be statistically significant (p <0.05). The most prevalent tooth shade among Chitradurga population was A2 and least was C1. There was a significant correlation between tooth shade and skin colour with lighter skin tone subjects having lighter tooth shade hence skin colour can be used as a guide for shade selection.
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A Comparison of Trap Types for Assessing Diversity of Scarabaeoidea on South Carolina Golf Courses.
Chong, Juang-Horng; Hinson, Kevin R
2015-10-01
A 2-yr survey was conducted on golf courses in South Carolina to 1) document the species richness and seasonal activity of Scarabaeoidea; 2) assess any species compositional differences among three trap types (ultraviolet light, unbaited flight-intercept, and unbaited pitfall); and 3) identify any dominant taxa in each trap type. A total of 74,326 scarabaeoid beetles were captured, of which 77.4% were Aphodiinae (not identified to species). The remaining specimens belong to 104 species in 47 genera and 6 families. The most abundant species were Cyclocephala lurida Bland, Dyscinetus morator (F.), Euetheola humilis (Burmeister), Hybosorus illigeri Reiche, and Maladera castanea (Arrow). In all trap types, >90% of all specimens and taxa were collected between April and August. Ultraviolet light traps collected ∼94% of total specimens consisting of 83 taxa (of which 51 were unique to this trap type), whereas flight-intercept traps captured ∼2% of all specimens representing 53 taxa (18 of which were unique), and pitfall traps captured ∼4% of all specimens representing 15 taxa (no unique species; all species also captured by ultraviolet light traps). Indicator species analysis identified 2-3 and 10-13 taxa that were most frequently collected by flight-intercept and ultraviolet light traps, respectively. Flight-intercept traps complemented ultraviolet light traps by capturing more species of dung and carrion beetles and diurnal phytophagous scarab beetles. Results suggested that a similar survey for domestic or exotic scarabaeoid beetles in turfgrass systems should be conducted between April and August using ultraviolet light and flight-intercept traps at 13-58 sites. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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LED and Halogen Light Transmission through a CAD/CAM Lithium Disilicate Glass-Ceramic.
Pereira, Carolina Nemesio de Barros; De Magalhães, Cláudia Silami; Daleprane, Bruno; Peixoto, Rogéli Tibúrcio Ribeiro da Cunha; Ferreira, Raquel da Conceição; Cury, Luiz Alberto; Moreira, Allyson Nogueira
2015-01-01
The effect of thickness, shade and translucency of CAD/CAM lithium disilicate glass-ceramic on light transmission of light-emitting diode (LED) and quartz-tungsten-halogen units (QTH) were evaluated. Ceramic IPS e.max CAD shades A1, A2, A3, A3.5, high (HT) and low (LT) translucency were cut (1, 2, 3, 4 and 5 mm). Light sources emission spectra were determined. Light intensity incident and transmitted through each ceramic sample was measured to determine light transmission percentage (TP). Statistical analysis used a linear regression model. There was significant interaction between light source and ceramic translucency (p=0.008) and strong negative correlation (R=-0.845, p<0.001) between ceramic thickness and TP. Increasing one unit in thickness led to 3.17 reduction in TP. There was no significant difference in TP (p=0.124) between shades A1 (ß1=0) and A2 (ß1=-0.45) but significant reduction occurred for A3 (ß1=-0.83) and A3.5 (ß1=-2.18). The interaction QTH/HT provided higher TP (ß1=0) than LED/HT (ß1=-2.92), QTH/LT (ß1=-3.75) and LED/LT (ß1=-5.58). Light transmission was more effective using halogen source and high-translucency ceramics, decreased as the ceramic thickness increased and was higher for the lighter shades, A1 and A2. From the regression model (R2=0.85), an equation was obtained to estimate TP value using each variable ß1 found. A maximum TP of 25% for QTH and 20% for LED was found, suggesting that ceramic light attenuation could compromise light cured and dual cure resin cements polymerization.
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Chen, Tsu-Wei; Nguyen, Thi My Nguyet; Kahlen, Katrin; Stützel, Hartmut
2014-01-01
There is increasing interest in evaluating the environmental effects on crop architectural traits and yield improvement. However, crop models describing the dynamic changes in canopy structure with environmental conditions and the complex interactions between canopy structure, light interception, and dry mass production are only gradually emerging. Using tomato (Solanum lycopersicum L.) as a model crop, a dynamic functional–structural plant model (FSPM) was constructed, parameterized, and evaluated to analyse the effects of temperature on architectural traits, which strongly influence canopy light interception and shoot dry mass. The FSPM predicted the organ growth, organ size, and shoot dry mass over time with high accuracy (>85%). Analyses of this FSPM showed that, in comparison with the reference canopy, shoot dry mass may be affected by leaf angle by as much as 20%, leaf curvature by up to 7%, the leaf length:width ratio by up to 5%, internode length by up to 9%, and curvature ratios and leaf arrangement by up to 6%. Tomato canopies at low temperature had higher canopy density and were more clumped due to higher leaf area and shorter internodes. Interestingly, dry mass production and light interception of the clumped canopy were more sensitive to changes in architectural traits. The complex interactions between architectural traits, canopy light interception, dry mass production, and environmental conditions can be studied by the dynamic FSPM, which may serve as a tool for designing a canopy structure which is ‘ideal’ in a given environment. PMID:25183746
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Coble, Adam P; Fogel, Marilyn L; Parker, Geoffrey G
2017-10-01
In temperate deciduous forests, vertical gradients in leaf mass per area (LMA) and area-based leaf nitrogen (Narea) are strongly controlled by gradients in light availability. While there is evidence that hydrostatic constraints on leaf development may diminish LMA and Narea responses to light, inherent differences among tree species may also influence leaf developmental and morphological response to light. We investigated vertical gradients in LMA, Narea and leaf carbon isotope composition (δ13C) for three temperate deciduous species (Carpinus caroliniana Walter, Fagus grandifolia Ehrh., Liriodendron tulipifera L.) that differed in growth strategy (e.g., indeterminate and determinate growth), shade tolerance and leaf area to sapwood ratio (Al:As). Leaves were sampled across a broad range of light conditions within three vertical layers of tree crowns to maximize variation in light availability at each height and to minimize collinearity between light and height. All species displayed similar responses to light with respect to Narea and δ13C, but not for LMA. Light was more important for gradients in LMA for the shade-tolerant (C. caroliniana) and -intolerant (L. tulipifera) species with indeterminate growth, and height (e.g., hydrostatic gradients) and light were equally important for the shade-tolerant (F. grandifolia) species with determinate growth. Fagus grandifolia had a higher morphological plasticity in response to light, which may offer a competitive advantage in occupying a broader range of light conditions throughout the canopy. Differences in responses to light and height for the taller tree species, L. tulipifera and F. grandifolia, may be attributed to differences in growth strategy or Al:As, which may alter morphological and functional responses to light availability. While height was important in F. grandifolia, height was no more robust in predicting LMA than light in any of the species, confirming the strong role of light availability in determining LMA for temperate deciduous species. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Pick, Uri; Gounaris, Kleoniki; Barber, James
1987-01-01
A photosystem two (PSII) core complex consisting of five major polypeptides (47, 40, 32, 30, and 10 kilodaltons) and a light harvesting chlorophyll a/b complex (LHC-2) have been isolated from the halotolerant alga Dunaliella salina. The chlorophyll and polypeptide composition of both complexes were compared in illuminated and dark-adapted cultures. Dark adaptation is accompanied by a decrease in the chlorophyll a to chlorophyll b (Chl a/Chl b) ratio of intact thylakoids without any change in total chlorophyll. These changes occur with a half-time of 3 hours and are reversed upon reillumination. Analyses of PSII enriched membrane fragments suggest that the decrease in the Chl a/Chl b is due partly to an increase in the Chl b content of LHC-2 and partly to changes in the relative levels of the two complexes. Apparently during dark adaptation there is: (a) a net synthesis of chlorophyll b, (b) removal of PSII core complexes resulting in a 2-fold drop in the PSII cores to LHC-2 chlorophyll ratio. These changes should dramatically increase the light harvesting capacity of the remaining PSII reaction centers. Presumably this adjustment of antenna size and composition is a physiological mechanism necessary for responding to shade conditions. Also detected, using 32P, are light-induced phosphorylation of the LHC-2 (consistent with the ability to undergo State transitions) and of the 40 and 30 kilodalton subunits of the PSII core complex. These observations indicate that additional mechanisms may also exist to help optimize the interception of quanta during rapid changes in illumination conditions. Images Fig. 4 PMID:16665656
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Krishnadas, Meghna; Comita, Liza S
2018-01-01
Soil fungi are key mediators of negative density-dependent mortality in seeds and seedlings, and the ability to withstand pathogens in the shaded understory of closed-canopy forests could reinforce light gradient partitioning by tree species. For four species of tropical rainforest trees-two shade-tolerant and two shade-intolerant-we conducted a field experiment to examine the interactive effects of fungal pathogens, light, and seed density on germination and early seedling establishment. In a fully factorial design, seeds were sown into 1 m 2 plots containing soil collected from underneath conspecific adult trees, with plots assigned to forest edge (high light) or shaded understory, high or low density, and fungicide or no fungicide application. We monitored total seed germination and final seedling survival over 15 weeks. Shade-intolerant species were strongly constrained by light; their seedlings survived only at the edge. Fungicide application significantly improved seedling emergence and/or survival for three of the four focal species. There were no significant interactions between fungicide and seed density, suggesting that pathogen spread with increased aggregation of seeds and seedlings did not contribute to pathogen-mediated mortality. Two species experienced significant edge-fungicide interactions, but fungicide effects in edge vs. interior forest varied with species and recruitment stage. Our results suggest that changes to plant-pathogen interactions could affect plant recruitment in human-impacted forests subject to fragmentation and edge-effects.
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Gokce, Hasan Suat; Piskin, Bulent; Ceyhan, Dogan; Gokce, Sila Mermut; Arisan, Volkan
2010-03-01
The lighting conditions of the environment and visual deficiencies such as red-green color vision deficiency affect the clinical shade matching performance of dental professionals. The purpose of this study was to evaluate the shade matching performance of normal and color vision-deficient dental professionals with standard daylight and tungsten illuminants. Two sets of porcelain disc replicas of 16 shade guide tabs (VITA Lumin) were manufactured to exact L*a*b* values by using a colorimeter. Then these twin porcelain discs (13 mm x 2.4 mm) were mixed up and placed into a color-matching cabinet that standardized the lighting conditions for the observation tests. Normal and red-green color vision-deficient dental professionals were asked to match the 32 porcelain discs using standard artificial daylight D65 (high color temperature) and tungsten filament lamp light (T) (low color temperature) illuminants. The results were analyzed by repeated-measures ANOVA and paired and independent samples t tests for the differences between dental professionals and differences between the illuminants (alpha=.05). Regarding the sum of the correct shade match scores of all observations with both illuminants, the difference between normal vision and red-green color vision-deficient dental professional groups was not statistically significant (F=4.132; P=.054). However, the correct shade match scores of each group were significantly different for each illuminant (P<.005). The correct shade matching scores of normal color vision dental professionals were significantly higher with D65 illuminant (t=7.004; P<.001). Color matching scores of red-green color vision-deficient dental professionals (approximately 5.7 more pairs than with D65) were significantly higher with T illuminant (t=5.977; P<.001). CONCLUSIONS.: Within the limitations of this study, the shade matching performance of dental professionals was affected by color vision deficiency and the color temperature of the illuminant. The color vision-deficient group was notably unsuccessful with the D65 illuminant in shade matching. In contrast, there was a significant increase in the shade matching performance of the color vision-deficient group with T illuminant. The lower color temperature illuminant dramatically decreased the normal color vision groups' correct shade matching score. (c) 2010 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ma, Shengbo; Ting, Hungkit; Ma, Yingzhuang
2015-05-15
In this paper, smart photovoltaic (SPV) devices, integrating both functions of solar cells and smart windows, was fabricated based on dye-sensitized solar cells using photochromic spiropyran derivatives SIBT as photosensitizers. SPV devices have self-regulated power conversion efficiency (PCE) and light transmission responding to the incident spectra due to the photoisomerization of SIBT. SIBT isomerize from closed-ring form to open-ring form under UV illumination, accompanied with enhanced visible light absorption and electron delocalization. Therefore, increased PCE and absorption in SPV devices were observed under UV treatment and the devices can be restored gradually to the initial status when kept in dark.more » The SPV devices have self-regulation of PCE and sunlight transmission responding to the changing sun spectra in different times of a day, providing a proper energy usage and a better sun-shading.« less
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Jared M. Craig; John M. Lhotka; Jeffrey W. Stringer
2013-01-01
Historically, the abundance of red maple and shade-tolerant understory species was limited by fire and other disturbances. In the absence of periodic disturbance, regeneration of oaks with intermediate shade tolerance has been hindered due to inadequate light conditions created by shade-tolerant midstory trees. Research suggests that midstory removal in oak-dominated...
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Li, Yang; Chen, Jing-Song; Xue, Ge; Peng, Yuanying; Song, Hui-Xing
2018-07-01
Clonal integration plays an important role in clonal plant adapting to heterogeneous habitats. It was postulated that clonal integration could exhibit positive effects on nitrogen cycling in the rhizosphere of clonal plant subjected to heterogeneous light conditions. An in-situ experiment was conducted using clonal fragments of Phyllostachys bissetii with two successive ramets. Shading treatments were applied to offspring or mother ramets, respectively, whereas counterparts were treated to full sunlight. Rhizomes between two successive ramets were either severed or connected. Extracellular enzyme activities and nitrogen turnover were measured, as well as soil properties. Abundance of functional genes (archaeal or bacterial amoA, nifH) in the rhizosphere of shaded, offspring or mother ramets were determined using quantitative polymerase chain reaction. Carbon or nitrogen availabilities were significantly influenced by clonal integration in the rhizosphere of shaded ramets. Clonal integration significantly increased extracellular enzyme activities and abundance of functional genes in the rhizosphere of shaded ramets. When rhizomes were connected, higher nitrogen turnover (nitrogen mineralization or nitrification rates) was exhibited in the rhizosphere of shaded offspring ramets. However, nitrogen turnover was significantly decreased by clonal integration in the rhizosphere of shaded mother ramets. Path analysis indicated that nitrogen turnover in the rhizosphere of shaded, offspring or mother ramets were primarily driven by the response of soil microorganisms to dissolved organic carbon or nitrogen. This unique in-situ experiment provided insights into the mechanism of nutrient recycling mediated by clonal integration. It was suggested that effects of clonal integration on the rhizosphere microbial processes were dependent on direction of photosynthates transport in clonal plant subjected to heterogeneous light conditions. Copyright © 2018 Elsevier B.V. All rights reserved.
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A field measure of the shade fraction
NASA Technical Reports Server (NTRS)
Gillespie, Alan R.; Smith, Milton O.; Sabol, Donald E.
1992-01-01
'Shade' has a technical definition peculiar to linear spectral mixture analysis of imaging spectrometer data: it is the reduction in radiance from a surface due to lighting conditions and geometry, and includes topographic shading described by photometric functions as well as shadowing at all scales. 'Shade' is an important constituent of nearly all remotely sensed images, and is one endmember resolved in spectral mixture analysis, where it is represented as a fraction of the measured radiance and a characteristic spectrum. This spectrum is typically the null vector, provided the data have been corrected for atmospheric and instrument effects: i.e., 'shade' is the radiance from an ideal black surface. In topographic shading, irradiance is reduced - typically in proportion to cos(i), where i (incidence angle) is the angle between the sun and the local surface normal vectors. Therefore, the radiance is lowered by a multiplicative factor. Shadowing occurs when i is greater than 90 deg, or when sunlight is blocked by adjacent high terrain; the only irradiance is down-welling skylight and bounce light from adjacent terrain. In spectral mixture analysis, 'shade' is regarded as an additive term. In this regard, it is an accurate description of the proportion of a scene that consists of ideal shadows ('checkerboard mixing'); however, 'shade' represents the multiplicative cos(i) factor as well, as here it should be interpreted as the proportion of shadow that would darken the scene an equivalent amount. In either case, the 'shade' fraction is lessened by adjacency effects, because the scene has a non-zero reflectivity instead of the ideal black surface generally assumed.
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Callie Jo Schweitzer; Emile S. Gardiner; David L. Loftis
2006-01-01
The primary objective of this study was to determine if greenhouse light environment would affect outplanting success for northern red oak (Quercus rubra L.) in clearcuts and shelterwoods. In 2002, northern red oak seedlings were grown from acorns under full-ambient (sun) and half-ambient (shade) light conditions in a greenhouse. Seedlings grown...
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Agrawal, Anurag A; Kearney, Emily E; Hastings, Amy P; Ramsey, Trey E
2012-07-01
Plant responses to herbivory and light competition are often in opposing directions, posing a potential conflict for plants experiencing both stresses. For sun-adapted species, growing in shade typically makes plants more constitutively susceptible to herbivores via reduced structural and chemical resistance traits. Nonetheless, the impact of light environment on induced resistance has been less well-studied, especially in field experiments that link physiological mechanisms to ecological outcomes. Accordingly, we studied induced resistance of common milkweed (Asclepias syriaca, a sun-adapted plant), and linked hormonal responses, resistance traits, and performance of specialist monarch caterpillars (Danaus plexippus) in varying light environments. In natural populations, plants growing under forest-edge shade showed reduced levels of resistance traits (lower leaf toughness, cardenolides, and trichomes) and enhanced light-capture traits (higher specific leaf area, larger leaves, and lower carbon-to-nitrogen ratio) compared to paired plants in full sun. In a field experiment repeated over two years, only milkweeds growing in full sun exhibited induced resistance to monarchs, whereas plants growing in shade were constitutively more susceptible and did not induce resistance. In a more controlled field experiment, plant hormones were higher in the sun (jasmonic acid, salicylic acid, abscisic acid, indole acidic acid) and were induced by herbivory (jasmonic acid and abscisic acid). In particular, the jasmonate burst following herbivory was halved in plants raised in shaded habitats, and this correspondingly reduced latex induction (but not cardenolide induction). Thus, we provide a mechanistic basis for the attenuation of induced plant resistance in low resource environments. Additionally, there appears to be specificity in these interactions, with light-mediated impacts on jasmonate-induction being stronger for latex exudation than cardenolides.
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Razzak, Abdur; Ranade, Sonali Sachin; Strand, Åsa; García-Gil, M R
2017-08-01
We investigated the response to increasing intensity of red (R) and far-R (FR) light and to a decrease in R:FR ratio in Pinus sylvestris L. (Scots pine) seedling. The results showed that FR high-irradiance response for hypocotyl elongation may be present in Scots pine and that this response is enhanced by increasing light intensity. However, both hypocotyl inhibition and pigment accumulation were more strongly affected by the R light compared with FR light. This is in contrast to previous reports in Arabidopsis thaliana (L.) Heynh. In the angiosperm, A. thaliana R light shows an overall milder effect on inhibition of hypocotyl elongation and on pigment biosynthesis compared with FR suggesting conifers and angiosperms respond very differently to the different light regimes. Scots pine shade avoidance syndrome with longer hypocotyls, shorter cotyledons and lower chlorophyll content in response to shade conditions resembles the response observed in A. thaliana. However, anthocyanin accumulation increased with shade in Scots pine, which again differs from what is known in angiosperms. Overall, the response of seedling development and physiology to R and FR light in Scots pine indicates that the regulatory mechanism for light response may differ between gymnosperms and angiosperms. © 2017 John Wiley & Sons Ltd.
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Active Beam Shaping System and Method Using Sequential Deformable Mirrors
NASA Technical Reports Server (NTRS)
Pueyo, Laurent A. (Inventor); Norman, Colin A. (Inventor)
2015-01-01
An active optical beam shaping system includes a first deformable mirror arranged to at least partially intercept an entrance beam of light and to provide a first reflected beam of light, a second deformable mirror arranged to at least partially intercept the first reflected beam of light from the first deformable mirror and to provide a second reflected beam of light, and a signal processing and control system configured to communicate with the first and second deformable mirrors. The first deformable mirror, the second deformable mirror and the signal processing and control system together provide a large amplitude light modulation range to provide an actively shaped optical beam.
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Mänd, Pille; Hallik, Lea; Peñuelas, Josep; Kull, Olevi
2013-02-01
We investigated changes in chlorophyll a fluorescence from alternate leaf surfaces to assess the intraleaf light acclimation patterns in combination with natural variations in radiation, leaf angles, leaf mass per area (LMA), chlorophyll content (Chl) and leaf optical parameters. Measurements were conducted on bottom- and top-layer leaves of Tilia cordata Mill. (a shade-tolerant sub-canopy species, sampled at heights of 11 and 16 m) and Populus tremula L. (a light-demanding upper canopy species, sampled at canopy heights of 19 and 26 m). The upper canopy species P. tremula had a six times higher PSII quantum yield (Φ(II)) and ratio of open reaction centres (qP), and a two times higher LMA than T. cordata. These species-specific differences were also present when the leaves of both species were in similar light conditions. Leaf adaxial/abaxial fluorescence ratio was significantly larger in the case of more horizontal leaves. Populus tremula (more vertical leaves), had smaller differences in fluorescence parameters between alternate leaf sides compared with T. cordata (more horizontal leaves). However, optical properties on alternate leaf sides showed a larger difference for P. tremula. Intraspecifically, the measured optical parameters were better correlated with LMA than with leaf Chl. Species-specific differences in leaf anatomy appear to enhance the photosynthetic potential of leaf biochemistry by decreasing the interception of excess light in P. tremula and increasing the light absorptance in T. cordata. Our results indicate that intraleaf light absorption gradient, described here as leaf adaxial/abaxial side ratio of chlorophyll a fluorescence, varies significantly with changes in leaf light environment in a multi-layer multi-species tree canopy. However, this variation cannot be described merely as a simple function of radiation, leaf angle, Chl or LMA, and species-specific differences in light acclimation strategies should also be considered.
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Dental Shade Guide Variability for Hues B, C, and D Using Cross-Polarized Photography.
Sampaio, Camila S; Gurrea, Jon; Gurrea, Marta; Bruguera, August; Atria, Pablo J; Janal, Malvin; Bonfante, Estevam A; Coelho, Paulo G; Hirata, Ronaldo
2018-04-20
This study evaluated the color variability of hues B, C, and D between the VITA Classical shade guide (Vita Zahnfabrik) and four other VITA-coded ceramic shade guides using a digital camera (Canon EOS 60D) and computer software (Adobe Photoshop CC). A cross-polarizing filter was used to standardize external light sources influencing color match. A total of 275 pictures were taken, 5 per shade tab, for 11 shades (B1, B2, B3, B4, C1, C2, C3, C4, D2, D3, and D4), from the following shade guides: VITA Classical (control); IPS e.max Ceram (Ivoclar Vivadent); IPS d.SIGN (Ivoclar Vivadent); Initial ZI (GC); and Creation CC (Creation Willi Geller). Pictures were evaluated using Adobe Photoshop CC for standardization of hue, chroma, and value between shade tabs. The VITA-coded shade guides evaluated here showed an overall unmatched shade in all their tabs when compared to the control, suggesting that shade selection should be made with the corresponding manufacturer guide of the ceramic intended for the final restoration.
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Interactive rendering of acquired materials on dynamic geometry using frequency analysis.
Bagher, Mahdi Mohammad; Soler, Cyril; Subr, Kartic; Belcour, Laurent; Holzschuch, Nicolas
2013-05-01
Shading acquired materials with high-frequency illumination is computationally expensive. Estimating the shading integral requires multiple samples of the incident illumination. The number of samples required may vary across the image, and the image itself may have high- and low-frequency variations, depending on a combination of several factors. Adaptively distributing computational budget across the pixels for shading is a challenging problem. In this paper, we depict complex materials such as acquired reflectances, interactively, without any precomputation based on geometry. In each frame, we first estimate the frequencies in the local light field arriving at each pixel, as well as the variance of the shading integrand. Our frequency analysis accounts for combinations of a variety of factors: the reflectance of the object projecting to the pixel, the nature of the illumination, the local geometry and the camera position relative to the geometry and lighting. We then exploit this frequency information (bandwidth and variance) to adaptively sample for reconstruction and integration. For example, fewer pixels per unit area are shaded for pixels projecting onto diffuse objects, and fewer samples are used for integrating illumination incident on specular objects.
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Coble, Adam P; Cavaleri, Molly A
2015-04-01
Within-canopy gradients of leaf functional traits have been linked to both light availability and vertical gradients in leaf water potential. While observational studies can reveal patterns in leaf traits, within-canopy experimental manipulations can provide mechanistic insight to tease apart multiple interacting drivers. Our objectives were to disentangle effects of height and light environment on leaf functional traits by experimentally shading branches along vertical gradients within a sugar maple (Acer saccharum) forest. Shading reduced leaf mass per area (LMA), leaf density, area-based leaf nitrogen (N(area)), and carbon:nitrogen (C:N) ratio, and increased mass-based leaf nitrogen (N(mass)), highlighting the importance of light availability on leaf morphology and chemistry. Early in the growing season, midday leaf water potential (Ψ(mid)), LMA, and N(area) were driven primarily by height; later in the growing season, light became the most important driver for LMA and Narea. Carbon isotope composition (δ(13)C) displayed strong, linear correlations with height throughout the growing season, but did not change with shading, implying that height is more influential than light on water use efficiency and stomatal behavior. LMA, leaf density, N(mass), C:N ratio, and δ(13)C all changed seasonally, suggesting that leaf ageing effects on leaf functional traits are equally as important as microclimatic conditions. Overall, our results indicate that: (1) stomatal sensitivity to vapor pressure deficit or Ψ(mid) constrains the supply of CO2 to leaves at higher heights, independent of light environment, and (2) LMA and N(area) distributions become functionally optimized through morphological acclimation to light with increasing leaf age despite height-related constraints.
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NASA Astrophysics Data System (ADS)
Cambra-López, María; Winkel, Albert; Mosquera, Julio; Ogink, Nico W. M.; Aarnink, André J. A.
2015-06-01
The objective of this study was to compare co-located real-time light scattering devices and equivalent gravimetric samplers in poultry and pig houses for PM10 mass concentration, and to develop animal-specific calibration factors for light scattering samplers. These results will contribute to evaluate the comparability of different sampling instruments for PM10 concentrations. Paired DustTrak light scattering device (DustTrak aerosol monitor, TSI, U.S.) and PM10 gravimetric cyclone sampler were used for measuring PM10 mass concentrations during 24 h periods (from noon to noon) inside animal houses. Sampling was conducted in 32 animal houses in the Netherlands, including broilers, broiler breeders, layers in floor and in aviary system, turkeys, piglets, growing-finishing pigs in traditional and low emission housing with dry and liquid feed, and sows in individual and group housing. A total of 119 pairs of 24 h measurements (55 for poultry and 64 for pigs) were recorded and analyzed using linear regression analysis. Deviations between samplers were calculated and discussed. In poultry, cyclone sampler and DustTrak data fitted well to a linear regression, with a regression coefficient equal to 0.41, an intercept of 0.16 mg m-3 and a correlation coefficient of 0.91 (excluding turkeys). Results in turkeys showed a regression coefficient equal to 1.1 (P = 0.49), an intercept of 0.06 mg m-3 (P < 0.0001) and a correlation coefficient of 0.98. In pigs, we found a regression coefficient equal to 0.61, an intercept of 0.05 mg m-3 and a correlation coefficient of 0.84. Measured PM10 concentrations using DustTraks were clearly underestimated (approx. by a factor 2) in both poultry and pig housing systems compared with cyclone pre-separators. Absolute, relative, and random deviations increased with concentration. DustTrak light scattering devices should be self-calibrated to investigate PM10 mass concentrations accurately in animal houses. We recommend linear regression equations as animal-specific calibration factors for DustTraks instead of manufacturer calibration factors, especially in heavily dusty environments such as animal houses.
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Demetriades-Shah, T.H.; Fuchs, M.; Kanemasu, E.T.; Flitcroft, I.D.
1994-01-01
A strong correlation exists between intercepted solar radiation and crop growth. We cautioned that many derivations of the functional relationship between solar energy and biomass use cumulated data, and therefore have logical and arithmetic weaknesses. We examined the growth response of plants to solar energy by using rates of change, of both interception and growth. Our analysis revealed that measurements of light interception can only establish the relationship a posteriori. Replacing interception data with normalized random numbers did not change the quality of the relations. Several scientists have contested our views. This article reconfirms the general validity of our analysis and of our conclusions, that it is not possible to determine plant growth on the sole basis of intercepted solar energy.
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NASA Astrophysics Data System (ADS)
Blain, Stéphane; Renaut, Sophie; Xing, Xiaogang; Claustre, Hervé; Guinet, Christophe
2013-12-01
analyze an original large data set of concurrent in situ measurements of fluorescence, temperature and salinity provided by sensors mounted on the elephant seals of Kerguelen Island. Our results were mainly gathered in regions of the Southern Ocean where the typical iron limitation is relieved by natural iron fertilization. Thus the role of light as the proximal factor of control of phytoplankton can be examined. We show that self-shading, and consequently stratification, are major factors controlling the integrated biomass during the bloom induced by iron fertilization. When the mixed layer was the shallowest, the maximum ChlML achievable by the given light-mixing regime was however not reached, most likely due to silicic acid limitation. We also show that a favorable light-mixing regime prevails after the spring equinox and is maintained for roughly seven months (October-April).
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Arikawa, Hiroyuki; Kanie, Takahito; Fujii, Koichi; Homma, Tetsuya; Takahashi, Hideo; Ban, Seiji
2003-09-01
The purpose of this study was to examine the light transmittance characteristics of the paint-on resins for shade modification. Three shades of paint-on resin, one crown and bridge resin, and human enamel were used. Specimens with four different thicknesses (75-150 microm) were prepared. The light transmittances including its wavelength distribution and diffusion characteristics were measured. The color values and the color differences among thicknesses of specimens were also determined. The light transmittance values of the paint-on resins ranged from 60.3% to 88.3% at 100 microm thickness, which were lower or nearly equal in comparison with the crown and bridge resin and enamel. Although differences in the wavelength distribution of transmittance among materials were found at lower wavelengths, all materials showed similar diffusion characteristics. The thin layer of paint-on resin effectively changed the color of restorative resin. The paint-on resin may be an effective material for the modification of the color appearance matching required.
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The impact of cigarette pack design, descriptors, and warning labels on risk perception in the U.S.
Bansal-Travers, Maansi; Hammond, David; Smith, Philip; Cummings, K Michael
2011-06-01
In the U.S., limited evidence exists on the impact of colors and brand imagery used in cigarette pack design. This study examined the impact of pack design, product descriptors, and health warnings on risk perception and brand appeal. A cross-sectional mall-intercept study was conducted with 197 adult smokers and 200 nonsmokers in Buffalo NY from June to July 2009 (data analysis from July 2009 to December 2010). Participants were shown 12 sets of packs randomly; each set varied by a particular design feature (color, descriptor) or warning label style (text versus graphic, size, attribution, message framing). Packs were rated on criteria including risk perceptions, quit motivation, and purchase interest. Participants selected larger, pictorial, and loss-framed warning labels as more likely to attract attention, encourage thoughts about health risks, motivate quitting, and be most effective. Participants were more likely to select packs with lighter color shading and descriptors such as light, silver, and smooth as delivering less tar, smoother taste, and lower health risk, compared to darker-shaded or full-flavor packs. Additionally, participants were more likely to select the branded compared to plain white pack when asked which delivered the most tar, smoothest taste, was more attractive, appealed to youth aged <18 years, and contained cigarettes of better quality. The findings support larger, graphic health warnings that convey loss-framed messages as most effective in communicating health risks to U.S. adults. The results also indicate that color and product descriptors are associated with false beliefs about risks. Plain packaging may reduce many of the erroneous misperceptions of risk communicated through pack design features. Copyright © 2011 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.
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The Impact of Cigarette Pack Design, Descriptors, and Warning Labels on Risk Perception in the U.S
Bansal-Travers, Maansi; Hammond, David; Smith, Philip; Cummings, K. Michael
2011-01-01
Background In the U.S., limited evidence exists on the impact of colors and brand imagery used in cigarette pack design. Purpose This study examined the impact of pack design, product descriptors, and health warnings on risk perception and brand appeal. Methods A cross-sectional mall-intercept study was conducted with 197 adult smokers and 200 nonsmokers in Buffalo, NY from June to July 2009 (data analysis from July 2009 to December 2010). Participants were shown 12 sets of packs randomly; each set varied by a particular design feature (color, descriptor) or warning label style (text vs graphic, size, attribution, message framing). Packs were rated on criteria including risk perceptions, quit motivation, and purchase interest. Results Participants selected larger, pictorial, and loss-framed warning labels as more likely to attract attention, encourage thoughts about health risks, motivate quitting, and most effective. Participants were more likely to select packs with lighter color shading and descriptors such as light, silver, and smooth as delivering less tar, smoother taste, and lower health risk, compared to darker-shaded or full flavor packs. Additionally, participants were more likely to select the branded compared to plain white pack when asked which delivered the most tar, smoothest taste, was more attractive, appealed to youth aged <18 years, and contained cigarettes of better quality. Conclusions The findings support larger, graphic health warnings that convey loss-framed messages as most effective in communicating health risks to U.S. adults. The results also indicate that color and product descriptors are associated with false beliefs about risks. Plain packaging may reduce many of the erroneous misperceptions of risk communicated through pack design features. PMID:21565661
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Kitao, M; Hida, T; Eguchi, N; Tobita, H; Utsugi, H; Uemura, A; Kitaoka, S; Koike, T
2016-01-01
We measured leaf photosynthetic traits in shade-grown seedlings of four tree species native to northern Japan, raised under an elevated CO2 condition, to investigate the effects of elevated CO2 on shade tolerance of deciduous broadleaf tree species with different successional traits. We considered Betula platyphylla var. japonica and Betula maximowicziana as pioneer species, Quercus mongolica var. crispula as a mid-successional species, and Acer mono as a climax species. The plants were grown under shade conditions (10% of full sunlight) in a CO2 -regulated phytotron. Light compensation points (LCPs) decreased in all tree species when grown under elevated CO2 (720 μmol·mol(-1) ), which were accompanied by higher apparent quantum yields but no photosynthetic down-regulation. LCPs in Q. mongolica and A. mono grown under elevated CO2 were lower than those in the two pioneer birch species. The LCP in Q. mongolica seedlings was not different from that of A. mono in each CO2 treatment. However, lower dark respiration rates were observed in A. mono than in Q. mongolica, suggesting higher shade tolerance in A. mono as a climax species in relation to carbon loss at night. Thus, elevated CO2 may have enhanced shade tolerance by lowering LCPs in all species, but the ranking of shade tolerance related to successional traits did not change among species under elevated CO2 , i.e. the highest shade tolerance was observed in the climax species (A. mono), followed by a gap-dependent species (Q. mongolica), while lower shade tolerance was observed in the pioneer species (B. platyphylla and B. maximowicziana). © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.
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51. (no plate) Lens, lens pedestal, mercury float, shade holder ...
51. (no plate) Lens, lens pedestal, mercury float, shade holder installation, drawing # 3101, sheet 2 of 2. Approved April 6, 1928. - Block Island Southeast Light, Spring Street & Mohegan Trail at Mohegan Bluffs, New Shoreham, Washington County, RI
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Reliability of shade selection using an intraoral spectrophotometer.
Witkowski, Siegbert; Yajima, Nao-Daniel; Wolkewitz, Martin; Strub, Jorge R
2012-06-01
In this study, we evaluate the accuracy and reproducibility of human tooth shade selection using a digital spectrophotometer. Variability among examiners and illumination conditions were tested for possible influence on measurement reproducibility. Fifteen intact anterior teeth of 15 subjects were evaluated for their shade using a digital spectrophotometer (Crystaleye, Olympus, Tokyo, Japan) by two examiners under the same light conditions representing a dental laboratory situation. Each examiner performed the measurement ten times on the labial surface of each tooth containing three evaluation sides (cervical, body, incisal). Commission International on Illumination color space values for L* (lightness), a* (red/green), and b* (yellow/blue) were obtained from each evaluated side. Examiner 2 repeated the measurements of the same subjects under different light conditions (i.e., a dental unit with a chairside lamp). To describe measurement precision, the mean color difference from the mean metric was used. The computed confidence interval (CI) value 5.228 (4.6598-5.8615) reflected (represented) the validity of the measurements. Least square mean analysis of the values obtained by examiners 1 and 2 or under different illumination conditions revealed no statistically significant differences (CI = 95%). Within the limits of the present study, the accuracy and reproducibility of dental shade selection using the tested spectrophotometer with respect to examiner and illumination conditions reflected the reliability of this device. This study suggests that the tested spectrophotometer can be recommended for the clinical application of shade selection.
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Influence of background/surrounding area on accuracy of visual color matching.
Dudea, Diana; Gasparik, Cristina; Botos, Alexandra; Alb, Florin; Irimie, Ada; Paravina, Rade D
2016-07-01
Visual shade selection is subjective and influenced by factors that might be operator-dependent or not. The objective was to evaluate influence of observer nonrelated factors (background/surrounding area, and light) and observer-related factors (gender and color competence) on shade-matching quality and to identify the most often mismatched shades in correlation with the background. Ten observers with average or superior color discrimination competence according to ISO TR 28642:2011 were asked to match 48 shade tabs of three VITA Classical shade guides, in a viewing booth under two light sources: D65 and D50. Gray, white, black, red, and light blue background/surrounding area simulated various clinical situations. The results were statistically analyzed using Kruskal-Wallis test and Mann-Whitney U test. Post hoc power analyses and sample size calculations were also conducted. The matching scores ranged between 72.7 % (using blue background) and 85.9 % (using white and black backgrounds). There was a statistically significant difference between matching scores on the five backgrounds (χ (2)(4) = 12.67, p = 0.01). When neutral gray was used as reference, Mann-Whitney U value was statistically significant only for the blue background (U = 107.00, Z = -2.52, p = 0.01). The influence of gender and lighting condition was also assessed, no statistically significance being found, but in both cases, the effect size and the achieved power were small. However, color discrimination competence did influence the results (p < 0.01). Background influenced shade matching results for tabs A3, B3, B4, and D4. Within the limitations of this study, it was concluded that 1. When it comes to the influence of the background/surround area on quality of color matching, no difference among achromatic backgrounds was recorded. Significantly worse results were recorded when the blue background was used. 2. Observers with superior color matching competence performed significantly better than the ones with average competence 3. The most frequently mismatched shade tabs were A3.5, B3, B4, and D4.
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NASA Astrophysics Data System (ADS)
Wiley, Erin; Chow, Pak; Landhäusser, Simon
2016-04-01
Carbon stress and starvation remain poorly understood in trees, despite their potential role in mortality from a variety of agents. To explore the effects of carbon stress on nonstructural carbohydrate (NSC) dynamics and recovery potential and to examine the process of starvation, we grew aspen seedlings under one of three levels of shade: 40% (light shade), 8% (medium shade), and 4% (dark shade) of full sunlight. We then exposed seedlings to 24 hours darkness at either 20° or 28° C until trees had died. Periodically, seedlings were harvested for NSC analysis and to measure stem and root respiration. In addition, some seedlings were moved back into the light to determine if recovery was possible at certain points during starvation. Specifically, we sought to address the following questions: 1) Do NSC concentrations or mass influence tree survival under carbon stress? 2) At what carbohydrate levels do trees fail to recover and starve? 3) Does temperature affect the NSC level at which trees starve? Increasing shade reduced growth, but surprisingly did not reduce NSC levels, except in a portion of deep shade seedlings that experienced dieback. Once in darkness, leaves died first, with final NSC levels ranging from ~4% (Medium shade, 28 degrees) to 7.5% (Light shade). Stem death generally occurred gradually down the stem. Stem tissues retained ~1-2% NSC when dead. Recovery was still possible when only the upper half of the stem had died; at this point, seedlings had relatively high root NSC levels in their remaining roots (7-10%), with 1-3% starch. No trees recovered after the whole stem had died, at which point, some trees root systems were completely dead. However, most retained substantial amounts of live roots, averaging 5-6% NSC, with 0.25-1.5% starch. Despite the initially similar NSC concentrations, light shade seedlings took longer to reach half stem and whole stem death than seedlings from medium and dark shade. Longer survival times were associated with greater initial NSC pool sizes and lower mass-specific respiration rates. Higher temperatures reduced the time until tissue death and also tended to reduce NSC levels at death in some tissues. Survival time during starvation appeared to be controlled not only by the size of initial reserves, but by the rate of respiration. Relatively high leaf NSC levels of dead leaves observed during drought and during fall leaf abscission are within the range of leaf NSC levels of starved leaves seen here. Patterns of nonzero tissue NSC and the piecewise progression of mortality often observed in mature trees are not inconsistent with the process of carbon starvation, which may contribute to tree death by many causes.
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Liu, Yun; Schieving, Feike; Stuefer, Josef F; Anten, Niels P R
2007-01-01
Because plants protect each other from wind, stand density affects both the light climate and the amount of mechanical stress experienced by plants. But the potential interactive effects of mechanical stress and canopy shading on plant growth have rarely been investigated and never in stoloniferous plants which, due to their creeping growth form, can be expected to respond differently to these factors than erect plants. Plants of ten genotypes of the stoloniferous species Potentilla reptans were subjected to two levels of mechanical stress (0 or 40 daily flexures) and two levels of spectral shading (15 % of daylight with a red:far red ratio of 0.3 vs. 50 % daylight and a red:far red ratio of 1.2). Mechanically stressed plants produced more leaves with shorter more flexible petioles, more roots, and more but less massive stolons. Responses to spectral shading were mostly in the opposite direction to thigmomorphogenesis, including the production of thinner, taller petioles made of more rigid tissue. The degree of thigmomorphogenesis was either independent of light climate or stimulated by spectral shading. At the genotypic level there were no clear correlations between responses to shade and mechanical stress. These results suggest that in stoloniferous plants mechanical stress results in clones with a more compact, shorter shoot structure and more roots. This response does not appear to be suppressed by canopy shading, which suggests that wind shielding (reduced mechanical stress) by neighbours in dense vegetation serves as a cue that induces shade avoidance responses such as increased petiole elongation.
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Folding Elastic Thermal Surface - FETS
NASA Technical Reports Server (NTRS)
Urquiza, Eugenio; Zhang, Burt X.; Thelen, Michael P.; Rodriquez, Jose I.; Pellegrino, Sergio
2013-01-01
The FETS is a light and compact thermal surface (sun shade, IR thermal shield, cover, and/or deployable radiator) that is mounted on a set of offset tape-spring hinges. The thermal surface is constrained during launch and activated in space by a thermomechanical latch such as a wax actuator. An application-specific embodiment of this technology developed for the MATMOS (Mars Atmospheric Trace Molecule Occultation Spectrometer) project serves as a deployable cover and thermal shield for its passive cooler. The FETS fits compactly against the instrument within the constrained launch envelope, and then unfolds into a larger area once in space. In this application, the FETS protects the passive cooler from thermal damage and contamination during ground operations, launch, and during orbit insertion. Once unfolded or deployed, the FETS serves as a heat shield, intercepting parasitic heat loads by blocking the passive cooler s view of the warm spacecraft. The technology significantly enhances the capabilities of instruments requiring either active or passive cooling of optical detectors. This can be particularly important for instruments where performance is limited by the available radiator area. Examples would be IR optical instruments on CubeSATs or those launched as hosted payloads because radiator area is limited and views are often undesirable. As a deployable radiator, the panels making up the FETS are linked thermally by thermal straps and heat pipes; the structural support and deployment energy is provided using tape-spring hinges. The FETS is a novel combination of existing technologies. Prior art for deployable heat shields uses rotating hinges that typically must be lubricated to avoid cold welding or static friction. By using tape-spring hinges, the FETS avoids the need for lubricants by avoiding friction altogether. This also eliminates the potential for contamination of nearby cooled optics by outgassing lubricants. Furthermore, the tape-spring design of the FETS is also self-locking so the panels stay in a rigid and extended configuration after deployment. This unexpected benefit makes the tape-spring hinge design of the FETS a light, simple, reliable, compact, non-outgassing hinge, spring, and latch. While tape-spring hinges are not novel, they have never been used to deploy passive unfolding thermal surfaces (radiator panels, covers, sun shades, or IR thermal shields). Furthermore, because this technology is compact, it has minimal impact on the launch envelope and mass specifications. FETS enhances the performance of hosted payload instruments where the science data is limited by dark noise. Incorporating FETS into a thermal control system increases radiator area, which lowers the optical detector temperature. This results in higher SNR (signal-to-noise ratio) and improved science data.
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Biomechanical factors contributing to self-organization in seagrass landscapes
Fonseca, M.S.; Koehl, M.A.R.; Kopp, B.S.
2007-01-01
Field observations have revealed that when water flow is consistently from one direction, seagrass shoots align in rows perpendicular to the primary axis of flow direction. In this study, live Zostera marina shoots were arranged either randomly or in rows perpendicular to the flow direction and tested in a seawater flume under unidirectional flow and waves to determine if shoot arrangement: a) influenced flow-induced force on individual shoots, b) differentially altered water flow through the canopy, and c) influenced light interception by the canopy. In addition, blade breaking strength was compared with flow-induced force to determine if changes in shoot arrangement might reduce the potential for damage to shoots. Under unidirectional flow, both current velocity in the canopy and force on shoots were significantly decreased when shoots were arranged in rows as compared to randomly. However, force on shoots was nearly constant with downstream distance, arising from the trade-off of shoot bending and in-canopy flow reduction. The coefficient of drag was higher for randomly-arranged shoots at low velocities (< 30 cm s- 1) but converged rapidly among the two shoot arrangements at higher velocities. Shoots arranged in rows tended to intercept slightly more light than those arranged randomly. Effects of shoot arrangement under waves were less clear, potentially because we did not achieve the proper plant size?row spacing ratio. At this point, we may only suggest that water motion, as opposed to light capture, is the dominant physical mechanism responsible for these shoot arrangements. Following a computation of the Environmental Stress Factor, we concluded that even photosynthetically active blades may be damaged or broken under frequently encountered storm conditions, irrespective of shoot arrangement. We hypothesize that when flow is generally from one direction, seagrass bed patterns over multiple scales of consideration may arise as a cumulative effect of individual shoot self-organization driven by reduced force and drag on the shoots and somewhat improved light capture.
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Kurt W. Gottschalk
1985-01-01
Optimum light levels for shelterwood cutting to develop the large advance regeneration that require were investigated using eight shade-cloth treatments. Seedlings of northern red oak, black oak, black cherry and red maple were grow under these light treatments for 2 years. Height and diameter were measured annually, and samples were harvested for dry weight and leaf...
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Decision-making in plants under competition.
Gruntman, Michal; Groß, Dorothee; Májeková, Maria; Tielbörger, Katja
2017-12-21
Plants can plastically respond to light competition in three strategies, comprising vertical growth, which promotes competitive dominance; shade tolerance, which maximises performance under shade; or lateral growth, which offers avoidance of competition. Here, we test the hypothesis that plants can 'choose' between these responses, according to their abilities to competitively overcome their neighbours. We study this hypothesis in the clonal plant Potentilla reptans using an experimental setup that simulates both the height and density of neighbours, thus presenting plants with different light-competition scenarios. Potentilla reptans ramets exhibit the highest vertical growth under simulated short-dense neighbours, highest specific leaf area (leaf area/dry mass) under tall-dense neighbours, and tend to increase total stolon length under tall-sparse neighbours. These responses suggest shifts between 'confrontational' vertical growth, shade tolerance and lateral-avoidance, respectively, and provide evidence that plants adopt one of several alternative plastic responses in a way that optimally corresponds to prevailing light-competition scenarios.
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Analytic double product integrals for all-frequency relighting.
Wang, Rui; Pan, Minghao; Chen, Weifeng; Ren, Zhong; Zhou, Kun; Hua, Wei; Bao, Hujun
2013-07-01
This paper presents a new technique for real-time relighting of static scenes with all-frequency shadows from complex lighting and highly specular reflections from spatially varying BRDFs. The key idea is to depict the boundaries of visible regions using piecewise linear functions, and convert the shading computation into double product integrals—the integral of the product of lighting and BRDF on visible regions. By representing lighting and BRDF with spherical Gaussians and approximating their product using Legendre polynomials locally in visible regions, we show that such double product integrals can be evaluated in an analytic form. Given the precomputed visibility, our technique computes the visibility boundaries on the fly at each shading point, and performs the analytic integral to evaluate the shading color. The result is a real-time all-frequency relighting technique for static scenes with dynamic, spatially varying BRDFs, which can generate more accurate shadows than the state-of-the-art real-time PRT methods.
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Gilbert, Matthew E.; McElrone, Andrew J.
2017-01-01
In agricultural and natural systems, diffuse light can enhance plant primary productivity due to deeper penetration into and greater irradiance of the entire canopy. However, for individual sun-grown leaves from three species, photosynthesis is actually less efficient under diffuse compared with direct light. Despite its potential impact on canopy-level productivity, the mechanism for this leaf-level diffuse light photosynthetic depression effect is unknown. Here, we investigate if the spatial distribution of light absorption relative to electron transport capacity in sun- and shade-grown sunflower (Helianthus annuus) leaves underlies its previously observed diffuse light photosynthetic depression. Using a new one-dimensional porous medium finite element gas-exchange model parameterized with light absorption profiles, we found that weaker penetration of diffuse versus direct light into the mesophyll of sun-grown sunflower leaves led to a more heterogenous saturation of electron transport capacity and lowered its CO2 concentration drawdown capacity in the intercellular airspace and chloroplast stroma. This decoupling of light availability from photosynthetic capacity under diffuse light is sufficient to generate an 11% decline in photosynthesis in sun-grown but not shade-grown leaves, primarily because thin shade-grown leaves similarly distribute diffuse and direct light throughout the mesophyll. Finally, we illustrate how diffuse light photosynthetic depression could overcome enhancement in canopies with low light extinction coefficients and/or leaf area, pointing toward a novel direction for future research. PMID:28432257
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Excess Diffuse Light Absorption in Upper Mesophyll Limits CO2 Drawdown and Depresses Photosynthesis.
Earles, J Mason; Théroux-Rancourt, Guillaume; Gilbert, Matthew E; McElrone, Andrew J; Brodersen, Craig R
2017-06-01
In agricultural and natural systems, diffuse light can enhance plant primary productivity due to deeper penetration into and greater irradiance of the entire canopy. However, for individual sun-grown leaves from three species, photosynthesis is actually less efficient under diffuse compared with direct light. Despite its potential impact on canopy-level productivity, the mechanism for this leaf-level diffuse light photosynthetic depression effect is unknown. Here, we investigate if the spatial distribution of light absorption relative to electron transport capacity in sun- and shade-grown sunflower ( Helianthus annuus ) leaves underlies its previously observed diffuse light photosynthetic depression. Using a new one-dimensional porous medium finite element gas-exchange model parameterized with light absorption profiles, we found that weaker penetration of diffuse versus direct light into the mesophyll of sun-grown sunflower leaves led to a more heterogenous saturation of electron transport capacity and lowered its CO 2 concentration drawdown capacity in the intercellular airspace and chloroplast stroma. This decoupling of light availability from photosynthetic capacity under diffuse light is sufficient to generate an 11% decline in photosynthesis in sun-grown but not shade-grown leaves, primarily because thin shade-grown leaves similarly distribute diffuse and direct light throughout the mesophyll. Finally, we illustrate how diffuse light photosynthetic depression could overcome enhancement in canopies with low light extinction coefficients and/or leaf area, pointing toward a novel direction for future research. © 2017 American Society of Plant Biologists. All Rights Reserved.
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Effect of ceramic thickness and shade on mechanical properties of a resin luting agent.
Passos, Sheila Pestana; Kimpara, Estevão Tomomitsu; Bottino, Marco Antonio; Rizkalla, Amin S; Santos, Gildo Coelho
2014-08-01
This study aimed to investigate the influence of ceramic thickness and shade on the Knoop hardness and dynamic elastic modulus of a dual-cured resin cement. Six ceramic shades (Bleaching, A1, A2, A3, A3.5, B3) and two ceramic thicknesses (1 mm, 3 mm) were evaluated. Disk specimens (diameter: 7 mm; thickness: 2 mm) of the resin cement were light cured under a ceramic block. Light-cured specimens without the ceramic block at distances of 1 and 3 mm were also produced. The Knoop hardness number (KHN), density, and dynamic Young's moduli were determined. Statistical analysis was conducted using ANOVA and a Tukey B rank order test (p = 0.05). The bleaching 1-mm-thick group exhibited significantly higher dynamic Young's modulus. Lower dynamic Young's moduli were observed for the 3-mm-thick ceramic groups compared to bleaching 3-mm-thick group, and no difference was found among the other 3-mm groups. For the KHN, when A3.5 3-mm-thick was used, the KHN was significantly lower than bleaching and A1 1-mm-thick ceramic; however, no difference was exhibited between the thicknesses of the same shade. The dual-cured resin cement studied irradiated through the 1-mm-thick ceramic with the lightest shade (bleaching ceramic) exhibited a better elastic modulus, and there was no effect in KHN of the resin cement when light cured under different ceramic shades and thicknesses (1 and 3 mm), except when the A3.5 3-mm-thick ceramic was used. Variolink II irradiated through ceramic with the lowest chroma exhibited the highest elastic modulus; therefore, the light activation method might not be the same for all clinical situations. © 2014 by the American College of Prosthodontists.
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Gómez-Polo, Cristina; Gómez-Polo, Miguel; Celemín Viñuela, Alicia; Martínez Vázquez de Parga, Juan Antonio
2015-03-01
The 3D-Master System comprises 26 physical shade tabs and intermediate shades. Determining the relationship among all the groups of lightness, chroma, and hue of the 3D-Master System (Vita Zahnfabrik) and the L*, C*, and h* coordinates is important, because according to the manufacturer, 2 Toothguide 3D-Master shades need to be mixed in a 50:50 ratio to create an intermediate shade. The purpose of the study was to relate the lightness, chroma, and hue groups of the 3D-Master System with the polar coordinates of the CIELAB chromatic space, L*, C*, and h*, and to quantify the shades tabs and intermediate shades of the 3D-Master System according to color coordinates. The middle third of the facial surface of a natural maxillary central incisor was measured with an Easyshade Compact spectrophotometer (Vita Zahnfabrik) in 1361 Spanish participants aged between 16 and 89 years. Natural tooth color was recorded in the 3D-Master nomenclature and in the CIE L*, C*, and h* coordinates system. The program used for the present descriptive statistical analysis of the results was SAS 9.1.3. In the L* variable, the minimum was found at 47.0 and the maximum at 91.3. In the C* variable, the minimum was found at 5.9 and the maximum at 49.8, while for h*, the minimum was 67.5 degrees and the maximum 112.0 degrees. Despite the limitations of this study, the 3D-Master System was found to be arranged according to L*, C*, and h* coordinates in groups of lightness, chroma, and hue. The corresponding groups of lightness, chroma, and hue can be estimated on the basis of L*, C*, and h* coordinates. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
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Pignon, Charles P.; Jaiswal, Deepak; McGrath, Justin M.
2017-01-01
Abstract The wild progenitors of major C4 crops grew as individuals subjected to little shading. Today they are grown in dense stands where most leaves are shaded. Do they maintain photosynthetic efficiency in these low light conditions produced by modern cultivation? The apparent maximum quantum yield of CO2 assimilation (ΦCO2max,app), a key determinant of light-limited photosynthesis, has not been systematically studied in field stands of C4 crops. ΦCO2max,app was derived from the initial slope of the response of leaf CO2 uptake (A) to photon flux (Q). Leaf fractional light absorptance (α) was measured to determine the absolute maximum quantum yield of CO2 assimilation on an absorbed light basis (ΦCO2max,abs). Light response curves were determined on sun and shade leaves of 49 field plants of Miscanthus × giganteus and Zea mays following canopy closure. ΦCO2max,app and ΦCO2max,abs declined significantly by 15–27% (P<0.05) with canopy depth. Experimentally, leaf age was shown unlikely to cause this loss. Modeling canopy CO2 assimilation over diurnal courses suggested that the observed decline in ΦCO2max,app with canopy depth costs 10% of potential carbon gain. Overcoming this limitation could substantially increase the productivity of major C4 crops. PMID:28110277
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Egilmez, Ferhan; Ergun, Gulfem; Cekic-Nagas, Isil; Vallittu, Pekka K; Lassila, Lippo V J
To evaluate the light transmission characteristics of different types, shades, and thicknesses of novel CAD/CAM materials and their effect on the degree of conversion (DC) of a dual-curing resin cement. Square specimens (12 × 12 mm2) of three CAD/CAM materials - GC Cerasmart, Lava Ultimate, Vita Enamic - of different thicknesses (1.00, 1.50, and 2.00 mm, n = 5 per thickness) were irradiated with an LED unit. The amount of transmitted light was quantified. Thereafter, the DC% of the dual-curing resin cement (RelyX Ultimate) was recorded after 15 min using Fourier transform infrared spectroscopy. Statistical analysis was performed using two-way ANOVA followed by the Tukey's HSD post-hoc test at a significance level of p < 0.05. Regression analysis was performed to investigate the correlation between the DC and radiant energy, and the DC and thickness. Although the type and shade of CAD/CAM material significantly affect transmitted light irradiation (p < 0.0001), degrees of conversion are similar when the CAD/CAM material or material shade were taken into consideration (p > 0.05). Conversely, material thickness significantly affected light transmission (p < 0.0001) and DC (p < 0.0001). Multiple effects of material, shade, and thickness did not significantly affect the evaluated parameters (p = 0.638 for light irradiation; p = 0.637 for DC). Linear regression analysis showed a correlation between delivered energy and DC% results of the Vita Enamic (R² = 0.4169, p < 0.0001). Reduced light transmission in 2-mm-thick specimens of all CAD/CAM materials indicates that proper curing of the cement beneath CAD/CAM materials should be ensured.
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Influence of resin cement shade on the color and translucency of ceramic veneers
HERNANDES, Daiana Kelly Lopes; ARRAIS, Cesar Augusto Galvão; de LIMA, Erick; CESAR, Paulo Francisco; RODRIGUES, José Augusto
2016-01-01
ABSTRACT Objective This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. Material and Methods One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C* ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. Results HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Conclusions Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable. PMID:27556211
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Influence of resin cement shade on the color and translucency of ceramic veneers.
Hernandes, Daiana Kelly Lopes; Arrais, Cesar Augusto Galvão; Lima, Erick de; Cesar, Paulo Francisco; Rodrigues, José Augusto
2016-01-01
This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C*ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable.
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Martins, Samuel C. V.; Araújo, Wagner L.; Tohge, Takayuki; Fernie, Alisdair R.; DaMatta, Fábio M.
2014-01-01
Coffee (Coffea arabica L.) has been traditionally considered as shade-demanding, although it performs well without shade and even out-yields shaded coffee. Here we investigated how coffee plants adjust their metabolic machinery to varying light supply and whether these adjustments are supported by a reprogramming of the primary and secondary metabolism. We demonstrate that coffee plants are able to adjust its metabolic machinery to high light conditions through marked increases in its antioxidant capacity associated with enhanced consumption of reducing equivalents. Photorespiration and alternative pathways are suggested to be key players in reductant-consumption under high light conditions. We also demonstrate that both primary and secondary metabolism undergo extensive reprogramming under high light supply, including depression of the levels of intermediates of the tricarboxylic acid cycle that were accompanied by an up-regulation of a range of amino acids, sugars and sugar alcohols, polyamines and flavonoids such as kaempferol and quercetin derivatives. When taken together, the entire dataset is consistent with these metabolic alterations being primarily associated with oxidative stress avoidance rather than representing adjustments in order to facilitate the plants from utilizing the additional light to improve their photosynthetic performance. PMID:24733284
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Geographical Influences of an Emerging Network of Gang Rivalries
2011-03-17
Hollenbeck in the N × M environment grid. The semi-permeable boundaries encoded in the model are displayed in the center image. The shades of gray of...intensity. Light shades of gray correspond to high density values near one and dark shades correspond to low densities near zero. The boundary crossing...Threshold Graphs ( GTG ) For comparison to the networks produced by our simulations, we constructed an instance of a Geograph- ical Threshold Graph ( GTG
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Sun and Shade Leaves: Some Field Investigations.
ERIC Educational Resources Information Center
Tomley, David
1983-01-01
Several simple experiments illustrating how the light regime affects the final form of dog's mercury (Mercurialis perennis) are provided. These experiments, which can also be done with other plants, focus on differences in the anatomy, morphology, and physiology of sun and shade leaves. (JN)
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Shading effect on generative characters of upland red rice of Southeast Sulawesi, Indonesia
NASA Astrophysics Data System (ADS)
Muhidin; Syam’un, E.; Kaimuddin; Musa, Y.; Sadimantara, G. R.; Usman; Leomo, S.; Rakian, T. C.
2018-05-01
Upland red rice (Oryza sativa) contains anthocyanin, a phenolic compounds that can act as antioxidants and functional food for human dietary. The content of functional food on upland red rice is influenced by shading condition, but the production is also influenced by environmental condition, especially the availability of light. The study aims is to assess and analyze the effect of shade on the growth and production of upland red rice. The research was conducted using the quantitative method to obtain the optimal shading condition that can increase the rice anthocyanin content and relatively high production. The research was arranged in split plot design, with shade as main plot and the different of cultivar as sub plot with three replications. The shading treatment consist of 4 levels as follows: n1=shade level < 25 %, n2=shade level 25-50%, n3=shade level 50-75% and n4=shade level > 75%. The cultivar tested were (v1) = Labandiri, (v2) = Jangkobembe, (v3) = Ranggohitam, and (v4) = Paedara. The rice planted in between teak wood trees with different age and level of canopy. The research reveals that shades had an effect in decreasing plant production (the higher level of shade, the higher the decrease level of production), but the shades can improve the quality of red rice through the increase of anthocyanin content.
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Gao, Jia; Cui, Hai Yan; Shi, Jian Guo; Dong, Shu Ting; Liu, Peng; Zhao, Bin; Zhang, Ji Wang
2018-03-01
We examined the changes of photosynthetic characteristics and chloroplast ultrastructure in mesophyll cell of summer maize in response to different light intensities in the field, with the summer maize hybrid Denghai 605 as experimental material. Two treatments of both shading (S) and increasing light (L) from flowering to physiological maturity stage were designed, with the ambient sunlight treatment as control (CK). Under shading treatment, poorly developed thylakoid structure, blurry lamellar structure, loose granum, large gap between slices and warping granum were the major characteristics in chloroplast. Meanwhile, photosynthetic rate (P n ), transpiration rate, stomatal conductance, chlorophyll content, and actual photo-chemical efficiency (Φ PSII ) decreased, whereas the maximal photochemical efficiency and non-photochemical quenching increased, which resulted in decreases in grain yield under shading treatment. However, a better development was observed in chloroplasts for L treatment, with the number of grana and lamellae increased and lamellae arranged compactly. In addition, P n and Φ PSII increased under L treatment, which increased grain yield. The chloroplast arrangement dispersed in mesophyll cells and chloroplast ultrastructure was destroyed after shading, and then chlorophyll synthesis per unit leaf area and photosynthetic capacity decreased. In contrast, the number of grana and lamellae increased and lamellae arranged compactly after increasing light, which are beneficial for corn yield.
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Enríquez, Susana; Pantoja-Reyes, Norma I
2005-09-01
The variation in seagrass morphology and the magnitude of leaf self-shading within the canopy of Thalassia testudinum, were compared among nine sites in a fringing reef lagoon. We found a significant variation in the growth-form of T. testudinum reflected in a 5.4-fold variation in the attenuation coefficient (K (d)) within the canopy. The largest morphological variation was observed in shoot density. Leaf biomass, leaf area index (LAI), and shoot density were positively associated with canopy-K (d) and with the percentage of surface irradiance received by the top of the seagrass canopy (% Es). These results provide an explanation for the consistent pattern of depth reduction in seagrass leaf biomass and shoot density reported in the literature. Shoot density and shoot size are two descriptors of the growth-form of T. testudinum related to its clonal life-form. Shoot size was not significantly correlated with canopy-K (d), nevertheless, it showed a significant effect on the slope of the relationship between shoot density and canopy-K (d). According to this model, shoot size also contributes to light attenuation within the seagrass canopy by increasing the effect of shoot density. This form-function analysis suggests that light may have a relevant role in the regulation of the optimal plant balance between horizontal (variation in shoot density) and vertical (variation in shoot size) growth of seagrasses. Other environmental factors and interactions also need to be examined to fully understand the mechanistic bases of the morphological responses of seagrasses to the environment.
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Shaded Relief Image of Saint Pierre and Miquelon
NASA Technical Reports Server (NTRS)
2000-01-01
This image shows two islands, Miquelon and Saint Pierre, located south of Newfoundland, Canada. These islands, along with five smaller islands, are a self-governing territory of France. A thin barrier beach divides Miquelon, with Grande Miquelon to the north and Petite Miquelonto the south. Saint Pierre Island is located to the lower right. With the islandsi location in the north Atlantic Ocean and their deep water ports, fishing is the major part of the economy. The maximum elevation of the island is 240 meters (787 feet). The land mass of the islands is about 242 square kilometers, or 1.5 times the size of Washington DC.This shaded relief image was generated using topographic data from the Shuttle Radar Topography Mission. A computer-generated artificial light source illuminates the elevation data to produce a pattern of light and shadows. Slopes facing the light appear bright, while those facing away are shaded. On flatter surfaces, the pattern of light and shadows can reveal subtle features in the terrain. Shaded relief maps are commonly used in applications such as geologic mapping and land use planning.This image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASAis Jet Propulsion Laboratory, Pasadena, CA, for NASA1s Earth Science Enterprise, Washington, DC.nal measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC. -
Vertex shading of the three-dimensional model based on ray-tracing algorithm
NASA Astrophysics Data System (ADS)
Hu, Xiaoming; Sang, Xinzhu; Xing, Shujun; Yan, Binbin; Wang, Kuiru; Dou, Wenhua; Xiao, Liquan
2016-10-01
Ray Tracing Algorithm is one of the research hotspots in Photorealistic Graphics. It is an important light and shadow technology in many industries with the three-dimensional (3D) structure, such as aerospace, game, video and so on. Unlike the traditional method of pixel shading based on ray tracing, a novel ray tracing algorithm is presented to color and render vertices of the 3D model directly. Rendering results are related to the degree of subdivision of the 3D model. A good light and shade effect is achieved by realizing the quad-tree data structure to get adaptive subdivision of a triangle according to the brightness difference of its vertices. The uniform grid algorithm is adopted to improve the rendering efficiency. Besides, the rendering time is independent of the screen resolution. In theory, as long as the subdivision of a model is adequate, cool effects as the same as the way of pixel shading will be obtained. Our practical application can be compromised between the efficiency and the effectiveness.
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Guan, Le; Wu, Benhong; Hilbert, Ghislaine; Li, Shaohua; Gomès, Eric; Delrot, Serge; Dai, Zhanwu
2017-08-01
Amino acid composition of the grape berry at harvest is important for wine making. The present study investigates the complex interplay between tissue, cultivar and light conditions that determine berry amino acid content. Twenty amino acids were assessed in the berry skin and pulp of two grape cultivars (Gamay Noir and Gamay Fréaux), grown under either light exposure or cluster shading conditions. In all samples, cluster shading significantly reduced most amino acids, except gamma-aminobutyric acid (GABA) and phenylalanine. However, the magnitude of the decrease was stronger in the skin (67.0% decrease) than in the pulp (30.4%) and stronger in cv. Gamay Noir (69.7%) than in Gamay Fréaux (30.7%). Cluster shading also significantly modified amino acid composition by decreasing the proline content while increasing the GABA content. These results are of oenological interest for shaping the amino acid composition of the must and improving wine quality. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Manimaran, P; Sadan, D Sai
2016-10-01
Smile is one of the most important interactive communication skills of a person. A smile is the key factor for an aesthetic appearance. Hence aesthetics is one of the motivating factor for the patients to seek dental care. Correction of unaesthetic appearance gives a positive effect to the self esteem of the patient. The aim of this study was to compare the difference in the shade between the commercially available shade guides namely Vita Classical And Ivoclar Chromascop and the fired porcelain samples fabricated using Vita Zahnfabrik VMK 95 and Ivoclar Classic Materials respectively. The objective of this study was to obtain a matching brand of material that has a particular shade tab among the brands used. To conclude, Ivoclar material matched the chromascop shade guide better than the vita material matched the vita classic shade guide.
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Optimizing countershading camouflage.
Cuthill, Innes C; Sanghera, N Simon; Penacchio, Olivier; Lovell, Paul George; Ruxton, Graeme D; Harris, Julie M
2016-11-15
Countershading, the widespread tendency of animals to be darker on the side that receives strongest illumination, has classically been explained as an adaptation for camouflage: obliterating cues to 3D shape and enhancing background matching. However, there have only been two quantitative tests of whether the patterns observed in different species match the optimal shading to obliterate 3D cues, and no tests of whether optimal countershading actually improves concealment or survival. We use a mathematical model of the light field to predict the optimal countershading for concealment that is specific to the light environment and then test this prediction with correspondingly patterned model "caterpillars" exposed to avian predation in the field. We show that the optimal countershading is strongly illumination-dependent. A relatively sharp transition in surface patterning from dark to light is only optimal under direct solar illumination; if there is diffuse illumination from cloudy skies or shade, the pattern provides no advantage over homogeneous background-matching coloration. Conversely, a smoother gradation between dark and light is optimal under cloudy skies or shade. The demonstration of these illumination-dependent effects of different countershading patterns on predation risk strongly supports the comparative evidence showing that the type of countershading varies with light environment.
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Acclimatization of Photosynthetic Apparatus of Tor Grass (Brachypodium pinnatum) during Expansion
Bąba, Wojciech; Kalaji, Hazem M.; Kompała-Bąba, Agnieszka; Goltsev, Vasilij
2016-01-01
The aim of this study was to understand the acclimatization mechanisms of photosynthetic apparatus in Brachypodium pinnatum (L.) P. Beauv grass during its expansion. Twelve populations differentiated by age: young (30–50 years old), intermediate age (ca. 100 y) and old (>300 y) were studied. It was confirmed that the decrease of the number of genotypes as a result of environmental stress and competition were reflected in changes in chlorophyll fluorescence (ChlF) parameters. The old stands were dominated by a few genotypes which seem to be the best acclimatized to the self-shading/competition by lowering their photosynthetic performance during light-phase of photosynthesis. On the other hand, the 'high-speed' photosynthetic rate observed in the young populations can be seen as acclimatization to very adverse conditions. Our results clearly confirm that ChlF is a powerful method of inferring physiological mechanisms of the expansion of tor grass. The Principal Component and Redundancy Analyses, followed with k-means classification, allowed to find the differentiation of groups of distinct ChlF parameters and enabled us to relate them to changes in genotypic diversity of populations. We conclude that the plastic morphological and physiological response to changeable habitat light conditions with its optimum in half-shade refers to its forest-steppe origin. PMID:27275605
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Acclimatization of Photosynthetic Apparatus of Tor Grass (Brachypodium pinnatum) during Expansion.
Bąba, Wojciech; Kalaji, Hazem M; Kompała-Bąba, Agnieszka; Goltsev, Vasilij
2016-01-01
The aim of this study was to understand the acclimatization mechanisms of photosynthetic apparatus in Brachypodium pinnatum (L.) P. Beauv grass during its expansion. Twelve populations differentiated by age: young (30-50 years old), intermediate age (ca. 100 y) and old (>300 y) were studied. It was confirmed that the decrease of the number of genotypes as a result of environmental stress and competition were reflected in changes in chlorophyll fluorescence (ChlF) parameters. The old stands were dominated by a few genotypes which seem to be the best acclimatized to the self-shading/competition by lowering their photosynthetic performance during light-phase of photosynthesis. On the other hand, the 'high-speed' photosynthetic rate observed in the young populations can be seen as acclimatization to very adverse conditions. Our results clearly confirm that ChlF is a powerful method of inferring physiological mechanisms of the expansion of tor grass. The Principal Component and Redundancy Analyses, followed with k-means classification, allowed to find the differentiation of groups of distinct ChlF parameters and enabled us to relate them to changes in genotypic diversity of populations. We conclude that the plastic morphological and physiological response to changeable habitat light conditions with its optimum in half-shade refers to its forest-steppe origin.
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NASA Astrophysics Data System (ADS)
Djuricic, Ana; Puttonen, Eetu; Harzhauser, Mathias; Dorninger, Peter; Székely, Balázs; Mandic, Oleg; Nothegger, Clemens; Molnár, Gábor; Pfeifer, Norbert
2016-04-01
The world's largest fossilized oyster reef is located in Stetten, Lower Austria excavated during field campaigns of the Natural History Museum Vienna between 2005 and 2008. It is studied in paleontology to learn about change in climate from past events. In order to support this study, a laser scanning and photogrammetric campaign was organized in 2014 for 3D documentation of the large and complex site. The 3D point clouds and high resolution images from this field campaign are visualized by photogrammetric methods in form of digital surface models (DSM, 1 mm resolution) and orthophoto (0.5 mm resolution) to help paleontological interpretation of data. Due to size of the reef, automated analysis techniques are needed to interpret all digital data obtained from the field. One of the key components in successful automation is detection of oyster shell edges. We have tested Reflectance Transformation Imaging (RTI) to visualize the reef data sets for end-users through a cultural heritage viewing interface (RTIViewer). The implementation includes a Lambert shading method to visualize DSMs derived from terrestrial laser scanning using scientific software OPALS. In contrast to shaded RTI no devices consisting of a hardware system with LED lights, or a body to rotate the light source around the object are needed. The gray value for a given shaded pixel is related to the angle between light source and the normal at that position. Brighter values correspond to the slope surfaces facing the light source. Increasing of zenith angle results in internal shading all over the reef surface. In total, oyster reef surface contains 81 DSMs with 3 m x 2 m each. Their surface was illuminated by moving the virtual sun every 30 degrees (12 azimuth angles from 20-350) and every 20 degrees (4 zenith angles from 20-80). This technique provides paleontologists an interactive approach to virtually inspect the oyster reef, and to interpret the shell surface by changing the light source direction. One source of light for shading does show all morphologic features needed for description. Additionally, more details such as fault lines, overlaps and characteristic edges of complex shell structures are clearly detected by simply changing the illumination on the shaded digital surface model. In a further study, the potential of edge detection of the individual shells will be analyzed based on statistical analysis by keeping track of the local accumulative shading gradient. The results are compared to manually identified edges. In a following study phase, the detected edges will be improved by graph cut segmentation. We assume that this technique can lead to automatically extracted teaching set for object segmentation on a complex environment. The project is supported by the Austrian Science Fund (FWF P 25883-N29).
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Reymond, Mathieu C.; Brunoud, Géraldine; Chauvet, Aurélie; Martínez-Garcia, Jaime F.; Martin-Magniette, Marie-Laure; Monéger, Françoise; Scutt, Charles P.
2012-01-01
A key innovation of flowering plants is the female reproductive organ, the carpel. Here, we show that a mechanism that regulates carpel margin development in the model flowering plant Arabidopsis thaliana was recruited from light-regulated processes. This recruitment followed the loss from the basic helix-loop-helix transcription factor SPATULA (SPT) of a domain previously responsible for its negative regulation by phytochrome. We propose that the loss of this domain was a prerequisite for the light-independent expression in female reproductive tissues of a genetic module that also promotes shade avoidance responses in vegetative organs. Striking evidence for this proposition is provided by the restoration of wild-type carpel development to spt mutants by low red/far-red light ratios, simulating vegetation shade, which we show to occur via phytochrome B, PHYTOCHROME INTERACTING FACTOR4 (PIF4), and PIF5. Our data illustrate the potential of modular evolutionary events to generate rapid morphological change and thereby provide a molecular basis for neo-Darwinian theories that describe this nongradualist phenomenon. Furthermore, the effects shown here of light quality perception on carpel development lead us to speculate on the potential role of light-regulated mechanisms in plant organs that, like the carpel, form within the shade of surrounding tissues. PMID:22851763
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Kimber, A.; Korschgen, C.E.; Van Der Valk, A.G.
1995-01-01
Vallisneria americana declined in backwaters of the Upper Mississippi River, U.S.A., after a drought in 1988. To determine whether viable seeds of V. americana occurred in the seed bank of navigation pool 7, Lake Onalaska, the upper 5 cm of sediment was collected from 103 sites in May 1990. These sediment samples were kept in pots at a depth of 0.4, 0.8, and 1.2 m in an outdoor pond for 12 weeks. Vallisneria americana seeds germinated from sites throughout the lake, and some seedlings produced overwintering buds by the end of the study. Seeds, spores, or fragments of 12 other species of aquatic plants also germinated. Seed germination trials with fresh and stored seeds in both greenhouse and ponds in which light availability was reduced with shade cloths indicated that seed germination was insensitive to light level. To determine the tight requirements for seedling survival and bud production, sediment from Lake Onalaska was incubated in ponds under neutral density shade screens reducing light to 2, 5, 9, and 25% of full sun. Seeds germinated under all shade treatments but survival was significantly higher in the 9 and 25% light treatments, and bud production was restricted to these light levels.
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Sánchez-Gómez, David; Valladares, Fernando; Zavala, Miguel A
2006-11-01
We investigated the differential roles of physiological and morphological features on seedling survivorship along an experimental irradiance gradient in four dominant species of cool temperate-Mediterranean forests (Quercus robur L., Quercus pyrenaica Willd., Pinus sylvestris L. and Pinus pinaster Ait.). The lowest photochemical efficiency (F(v)/F(m) in dark-adapted leaves) was reached in deep shade (1% of full sunlight) in all species except Q. robur, which had the lowest photochemical efficiency in both deep shade and 100% of full sunlight. Species differed significantly in their survival in 1% of full sunlight but exhibited similar survivorship in 6, 20 and 100% of full sunlight. Shade-tolerant oaks had lower leaf area ratios, shoot to root ratios, foliage allocation ratios and higher rates of allocation to structural biomass (stem plus thick roots) than shade-intolerant pines. Overall phenotypic plasticity for each species, estimated as the difference between the minimum and the maximum mean values of the ecophysiological variables studied at the various irradiances divided by the maximum mean value of those variables, was inversely correlated with shade tolerance. Observed morphology, allocation and plasticity conformed to a conservative resource-use strategy, although observed differences in specific leaf area, which was higher in shade-tolerant species, supported a carbon gain maximization strategy. Lack of a congruent suite of traits underlying shade tolerance in the studied species provides evidence of adaptation to multiple selective forces. Although the study was based on only four species, the importance of ecophysiological variables as determinants of interspecific differences in survival in limiting light was demonstrated.
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Holmgren, Milena; Gómez-Aparicio, Lorena; Quero, José Luis; Valladares, Fernando
2012-06-01
The combined effects of shade and drought on plant performance and the implications for species interactions are highly debated in plant ecology. Empirical evidence for positive and negative effects of shade on the performance of plants under dry conditions supports two contrasting theoretical models about the role of shade under dry conditions: the trade-off and the facilitation hypotheses. We performed a meta-analysis of field and greenhouse studies evaluating the effects of drought at two or more irradiance levels on nine response variables describing plant physiological condition, growth, and survival. We explored differences in plant response across plant functional types, ecosystem types and methodological approaches. The data were best fit using quadratic models indicating a humped-back shape response to drought along an irradiance gradient for survival, whole plant biomass, maximum photosynthetic capacity, stomatal conductance and maximal photochemical efficiency. Drought effects were ameliorated at intermediate irradiance, becoming more severe at higher or lower light levels. This general pattern was maintained when controlling for potential variations in the strength of the drought treatment among light levels. Our quantitative meta-analysis indicates that dense shade ameliorates drought especially among drought-intolerant and shade-tolerant species. Wet tropical species showed larger negative effects of drought with increasing irradiance than semiarid and cold temperate species. Non-linear responses to irradiance were stronger under field conditions than under controlled greenhouse conditions. Non-linear responses to drought along the irradiance gradient reconciliate opposing views in plant ecology, indicating that facilitation is more likely within certain range of environmental conditions, fading under deep shade, especially for drought-tolerant species.
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Bonnineau, Chloé; Sague, Irene Gallardo; Urrea, Gemma; Guasch, Helena
2012-05-01
In multiple stress situations, the co-occurrence of environmental and chemical factors can influence organisms' ability to cope with toxicity. In this context, the influence of light adaptation on the response of freshwater biofilms to sudden light changes or to herbicides exposure was investigated by determining various parameters: diatom community composition, photosynthetic parameters, chlorophyll a content, antioxidant enzyme activities. Biofilms were grown in microcosms under sub-optimal, saturating, and high light intensities and showed already described characteristics of shade/light adaptation (community structure, photosynthetic adaptation, etc.). Light history modulated antioxidant and photosynthetic responses of biofilms to the stress caused by short-term exposure to sudden light changes or to herbicides. First biofilms adapted to sub-optimal light intensity (shade-adapted) were found to be more sensitive to an increase in light intensity than high-light adapted ones to a reduction in light intensity. Second, while light history influenced biofilms' response to glyphosate, it had little influence on biofilms' response to copper and none on its response to oxyfluorfen. Indeed glyphosate exposure led to a stronger decrease in photosynthetic efficiency of shade-adapted biofilms (EC(50) = 11.7 mg L(-1)) than of high-light adapted communities (EC(50) = 35.6 mg L(-1)). Copper exposure led to an activation of ascorbate peroxidase (APX) in biofilms adapted to sub-optimal and saturating light intensity while the protein content decreased in all biofilms exposed to copper. Oxyfluorfen toxicity was independent of light history provoking an increase in APX activity. In conclusion this study showed that both previous exposure to contaminants and physical habitat characteristics might influence community tolerance to disturbances strongly.
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Sun and Shade leaves, SIF, and Photosynthetic Capacity
NASA Astrophysics Data System (ADS)
Berry, J. A.; Badgley, G.
2016-12-01
Recent advances in retrieval of solar induced chlorophyll fluorescence (SIF) have opened up new possibilities for remote sensing of canopy physiology and structure. To date most of the emphasis has been placed on SIF as an indicator of stress and photosynthetic capacity. However, it is clear that canopy structure can also have an influence. To this point, simulations of SIF in land surface models tend to under predict observed variation in SIF. Also, large, systematic differences in SIF from different canopy types seem to correlate well with the photosynthetic capacity of these canopies. SIF emissions from pampered crops can be several-fold that from evergreen, needle-leaf forests. Yet, these may have similar vegetation indices and absorb a similar fraction of incident PAR. SIF photons produced in a conifer canopy do have a lower probability of escaping its dense, clumped foliage. However, this does not explain the correlated differences in photosynthetic rate and SIF. It is useful, in this regard, to consider the separate contributions of sun and shade leaves to the SIF emitted by a canopy. Sun leaves tend to be displayed to intercept the direct solar beam, and these highly illuminated leaves are often visible from above the canopy. Sun leaves produce more SIF and a large fraction of it escapes. Therefore, the intensity of SIF may be a sensitive indicator of the partitioning of absorbed PAR to sun and shade leaves. Many models account tor the different photosynthetic capacity of sun and shade leaves in calculating canopy responses. However, the fraction of leaves in each category is usually parameterized by an assumed leaf angle distribution (e.g. spherical). In reality, the sun/shade fraction can vary over a wide range, and it has been difficult to measure. SIF and possibly near-IR reflectance of canopies can be used to specify this key parameter with obvious importance to understanding photosynthetic rate.
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NASA Technical Reports Server (NTRS)
Rosecrance, Richard C.; Johnson, Lee; Soderstrom, Dominic
2016-01-01
Canopy light interception is a main driver of water use and crop yield in almond and walnut production. Fractional green canopy cover (Fc) is a good indicator of light interception and can be estimated remotely from satellite using the normalized difference vegetation index (NDVI) data. Satellite-based Fc estimates could be used to inform crop evapotranspiration models, and hence support improvements in irrigation evaluation and management capabilities. Satellite estimates of Fc in almond and walnut orchards, however, need to be verified before incorporating them into irrigation scheduling or other crop water management programs. In this study, Landsat-based NDVI and Fc from NASA's Satellite Irrigation Management Support (SIMS) were compared with four estimates of canopy cover: 1. light bar measurement, 2. in-situ and image-based dimensional tree-crown analyses, 3. high-resolution NDVI data from low flying aircraft, and 4. orchard photos obtained via Google Earth and processed by an Image J thresholding routine. Correlations between the various estimates are discussed.
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NASA Astrophysics Data System (ADS)
Rosecrance, R. C.; Johnson, L.; Soderstrom, D.
2016-12-01
Canopy light interception is a main driver of water use and crop yield in almond and walnut production. Fractional green canopy cover (Fc) is a good indicator of light interception and can be estimated remotely from satellite using the normalized difference vegetation index (NDVI) data. Satellite-based Fc estimates could be used to inform crop evapotranspiration models, and hence support improvements in irrigation evaluation and management capabilities. Satellite estimates of Fc in almond and walnut orchards, however, need to be verified before incorporating them into irrigation scheduling or other crop water management programs. In this study, Landsat-based NDVI and Fc from NASA's Satellite Irrigation Management Support (SIMS) were compared with four estimates of canopy cover: 1. light bar measurement, 2. in-situ and image-based dimensional tree-crown analyses, 3. high-resolution NDVI data from low flying aircraft, and 4. orchard photos obtained via Google Earth and processed by an Image J thresholding routine. Correlations between the various estimates are discussed.
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Genetic variation in response to shade in coastal Douglas-fir.
J. Bradley St. Clair; Richard A. Sniezko
1999-01-01
Tree improvement programs have generally relied on testing families in open light environments. With increased interest in multiaged silvicultural systems, some people have questioned whether families selected in the open are appropriate for planting in the shade. We grew Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii...
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Code of Federal Regulations, 2013 CFR
2013-01-01
... 7 Agriculture 2 2013-01-01 2013-01-01 false Discoloration. 51.700 Section 51.700 Agriculture..., California, and Arizona) Definitions § 51.700 Discoloration. Discoloration means russeting of light shade of... fairly smooth, superficial scars or other means may be allowed on a greater area, or darker shades may be...
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Code of Federal Regulations, 2011 CFR
2011-01-01
... 7 Agriculture 2 2011-01-01 2011-01-01 false Discoloration. 51.700 Section 51.700 Agriculture... § 51.700 Discoloration. Discoloration means russeting of light shade of golden brown caused by rust... scars or other means may be allowed on a greater area, or darker shades may be allowed on a lesser area...
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Code of Federal Regulations, 2010 CFR
2010-01-01
... 7 Agriculture 2 2010-01-01 2010-01-01 false Discoloration. 51.638 Section 51.638 Agriculture...) Definitions § 51.638 Discoloration. Discoloration means russeting of light shade of golden brown caused by..., superficial scars or other means may be allowed on a greater area, or darker shades may be allowed on a lesser...
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Code of Federal Regulations, 2011 CFR
2011-01-01
... 7 Agriculture 2 2011-01-01 2011-01-01 false Discoloration. 51.638 Section 51.638 Agriculture...) Definitions § 51.638 Discoloration. Discoloration means russeting of light shade of golden brown caused by..., superficial scars or other means may be allowed on a greater area, or darker shades may be allowed on a lesser...
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Code of Federal Regulations, 2010 CFR
2010-01-01
... 7 Agriculture 2 2010-01-01 2010-01-01 false Discoloration. 51.700 Section 51.700 Agriculture... § 51.700 Discoloration. Discoloration means russeting of light shade of golden brown caused by rust... scars or other means may be allowed on a greater area, or darker shades may be allowed on a lesser area...
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Code of Federal Regulations, 2014 CFR
2014-01-01
... 7 Agriculture 2 2014-01-01 2014-01-01 false Discoloration. 51.700 Section 51.700 Agriculture..., California, and Arizona) Definitions § 51.700 Discoloration. Discoloration means russeting of light shade of... fairly smooth, superficial scars or other means may be allowed on a greater area, or darker shades may be...
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Local auxin production underlies a spatially restricted neighbor-detection response in Arabidopsis
Michaud, Olivier
2017-01-01
Competition for light triggers numerous developmental adaptations known as the “shade-avoidance syndrome” (SAS). Important molecular events underlying specific SAS responses have been identified. However, in natural environments light is often heterogeneous, and it is currently unknown how shading affecting part of a plant leads to local responses. To study this question, we analyzed upwards leaf movement (hyponasty), a rapid adaptation to neighbor proximity, in Arabidopsis. We show that manipulation of the light environment at the leaf tip triggers a hyponastic response that is restricted to the treated leaf. This response is mediated by auxin synthesized in the blade and transported to the petiole. Our results suggest that a strong auxin response in the vasculature of the treated leaf and auxin signaling in the epidermis mediate leaf elevation. Moreover, the analysis of an auxin-signaling mutant reveals signaling bifurcation in the control of petiole elongation versus hyponasty. Our work identifies a mechanism for a local shade response that may pertain to other plant adaptations to heterogeneous environments. PMID:28652343
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Greer, Dennis H; Weedon, Mark M
2012-05-01
High-light intensities and temperatures of the warm climate regions of Australia and elsewhere have a major effect on the growth and development of grapevines (Vitis vinifera L.). The objective of this research was to assess interactions between the light and seasonal temperatures by shading some vines and comparing these with vines exposed to high-light intensities. Canopy temperatures were monitored using infrared radiometers and budbreak, phenology, growth, yield, berry ripening and gas exchange determined over three growing seasons. Results showed canopies were generally about 4 °C cooler than air and shading extended this cooling. Irradiance, irrespective of seasonal temperatures, had no effect on time of budbreak, shoot phenology, stem growth, yield and bunch fresh weights while bunch and leaf dry weights were reduced in low-light. Bunch ripening was initially delayed by low-light but thereafter the ripening process was highly temperature-dependent. Rates increased linearly with increasing temperature in both low and high-light and were optimal at about 35 °C. Maximum photosynthetic capacity was impaired by low irradiance, in accordance with shade leaf attributes, and attributable to stomatal closure. No effects of the low photosynthetic capacity apparently carried-over to sugar accumulation, consistent with the strong sink capacity of bunches. Crown Copyright © 2012. Published by Elsevier Masson SAS. All rights reserved.
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Sugiura, D; Tateno, M
2013-08-01
We investigated the nitrogen and carbohydrate allocation patterns of trees under heterogeneous light environments using saplings of the devil maple tree (Acer diabolicum) with Y-shaped branches. Different branch groups were created: all branches of a sapling exposed to full light (L-branches), all branches exposed to full shade (S-branches), and half of the branches of a sapling exposed to light (HL-branches) and the other half exposed to shade (HS-branches). Throughout the growth period, nitrogen was preferentially allocated to HL-branches, whereas nitrogen allocation to HS-branches was suppressed compared to L- and S-branches. HL-branches with the highest leaf nitrogen content (N(area)) also had the highest rates of growth, and HS-branches with the lowest N(area) had the lowest observed growth rates. In addition, net nitrogen assimilation, estimated using a photosynthesis model, was strongly correlated with branch growth and whole-plant growth. In contrast, patterns of photosynthate allocation to branches and roots were not affected by the light conditions of the other branch. These observations suggest that tree canopies develop as a result of resource allocation patterns, where the growth of sun-lit branches is favoured over shaded branches, which leads to enhanced whole-plant growth in heterogeneous light environments. Our results indicate that whole-plant growth is enhanced by the resource allocation patterns created for saplings in heterogeneous light environments.
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Physiological Analysis of Phototropic Responses in Arabidopsis.
Zeidler, Mathias
2016-01-01
Plants utilize light as sole energy source. To maximize light capture they are able to detect the light direction and orient themselves towards the light source. This phototropic response is mediated by the plant blue light photoreceptors phototropin1 and 2 (phot1 and phot2). Although fully differentiated plants also exhibit this response it can be best observed in etiolated seedlings. Differences in light between the illuminated and shaded site of a seedling stem lead to changes in the auxin-distribution, resulting in cell elongation on the shaded site. Since phototropism connects light perception, signaling, and auxin transport, it is of great interest to analyze this response with a fast and simple method.Here we describe a method to analyze the phototropic response of Arabidopsis seedlings. With numerous mutants available, its fast germination and its small size Arabidopsis is well suited for this analysis. Different genotypes can be simultaneously probed in less than a week.
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NASA Astrophysics Data System (ADS)
Loustau, D.; Berbigier, P.; Granier, A.
1992-10-01
Interception, throughfall and stemflow were determined in an 18-year-old maritime pine stand for a period of 30 months. This involved 71 rainfall events, each corresponding either to a single storm or to several storms. Gash's analytical model of interception was used to estimate the sensitivity of interception to canopy structure and climatic parameters. The seasonal cumulative interception loss corresponded to 12.6-21.0% of the amount of rainfall, whereas throughfall and stemflow accounted for 77-83% and 1-6%, respectively. On a seasonal basis, simulated data fitted the measured data satisfactorily ( r2 = 0.75). The rainfall partitioning between interception, throughfall and stemflow was shown to be sensitive to (1) the rainfall regime, i.e. the relative importance of light storms to total rainfall, (2) the climatic parameters, rainfall rate and average evaporation rate during storms, and (3) the canopy structure parameters of the model. The low interception rate of the canopy was attributed primarily to the low leaf area index of the stand.
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Intrarater repeatability of shade selections with two shade guides.
Hammad, Ihab A
2003-01-01
Color research has shown that shade guides do not always represent the color of natural teeth. Moreover, visual evaluation has been found to be unreliable and inconsistent. This investigation evaluated the effects of 2 shade guides on the intrarater repeatability (reliability) of prosthodontists and general practitioners with regard to shade selection. Ten prosthodontists and ten general practitioners (all men, 35-45 years old) with an average practice experience of 14 years participated in this study. Examiners were tested to eliminate color blindness. Each clinician used Vita Lumin Vacuum and Vitapan 3D-Master shade guides to determine the shades of the maxillary right canines of 20 patients following a standard protocol. The identification codes of the shade tabs were masked to prevent shade memory. All teeth were polished before each shade selection, and the selection process was standardized for controlled lighting and procedures. Shade selections were randomly repeated 1 month later by the same practitioners on the same group of patients in accordance with the same shade-selection protocol. Analysis of variance and t tests for individual comparisons among means were performed (P<.05). Significant interactions were found between the effects of shade guide system and specialty training on intrarater repeatability (P<.0001, analysis of variance). The intrarater repeatability of prosthodontists was significantly higher than that of general practitioners when the Vita Lumin Vacuum shade guide was used (P<.0001, t test). Use of the Vitapan 3D-Master shade guide significantly improved the intrarater repeatability of general practitioners compared with the Vita Lumin Vacuum shade guide (P<.0005). This improvement was not significant, however, among prosthodontists (P=.2861). Within the limitations of this study, the prosthodontists demonstrated superior intrarater repeatability in shade selection, especially when the Vita Lumin Vacuum shade guide was used. Use of the Vitapan 3D-Master shade guide notably improved intrarater repeatability among the general practitioners.
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Jung, Dae Ho; Lee, Joon Woo; Kang, Woo Hyun; Hwang, In Ha; Son, Jung Eek
2018-01-04
Photosynthesis is an important physiological response for determination of CO₂ fertilization in greenhouses and estimation of crop growth. In order to estimate the whole plant photosynthetic rate, it is necessary to investigate how light interception by crops changes with environmental and morphological factors. The objectives of this study were to analyze plant light interception using a three-dimensional (3D) plant model and ray-tracing, determine the spatial distribution of the photosynthetic rate, and estimate the whole plant photosynthetic rate of Irwin mango ( Mangifera indica L. cv. Irwin) grown in greenhouses. In the case of mangoes, it is difficult to measure actual light interception at the canopy level due to their vase shape. A two-year-old Irwin mango tree was used to measure the whole plant photosynthetic rate. Light interception and whole plant photosynthetic rate were measured under artificial and natural light conditions using a closed chamber (1 × 1 × 2 m). A 3D plant model was constructed and ray-tracing simulation was conducted for calculating the photosynthetic rate with a two-variable leaf photosynthetic rate model of the plant. Under artificial light, the estimated photosynthetic rate increased from 2.0 to 2.9 μmolCO₂·m -2 ·s -1 with increasing CO₂ concentration. On the other hand, under natural light, the photosynthetic rate increased from 0.2 μmolCO₂·m -2 ·s -1 at 06:00 to a maximum of 7.3 μmolCO₂·m -2 ·s -1 at 09:00, then gradually decreased to -1.0 μmolCO₂·m -2 ·s -1 at 18:00. In validation, simulation results showed good agreement with measured results with R ² = 0.79 and RMSE = 0.263. The results suggest that this method could accurately estimate the whole plant photosynthetic rate and be useful for pruning and adequate CO₂ fertilization.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Sun, Xingshu; Alam, Muhammad Ashraful; Raguse, John
2015-10-15
In this paper, we develop a physics-based compact model for copper indium gallium diselenide (CIGS) and cadmium telluride (CdTe) heterojunction solar cells that attributes the failure of superposition to voltage-dependent carrier collection in the absorber layer, and interprets light-enhanced reverse breakdown as a consequence of tunneling-assisted Poole-Frenkel conduction. The temperature dependence of the model is validated against both simulation and experimental data for the entire range of bias conditions. The model can be used to characterize device parameters, optimize new designs, and most importantly, predict performance and reliability of solar panels including the effects of self-heating and reverse breakdown duemore » to partial-shading degradation.« less
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Jallet, Denis; Caballero, Michael A.; Gallina, Alessandra A.
Photosynthetic microbes respond to changing light environments to balance photosynthetic process with light induced damage and photoinhibition. There have been very few characterizations of photosynthetic physiology or biomass partitioning during the day in mass culture. Understanding the constraints on photosynthetic efficiency and biomass accumulation are necessary for engineering superior strains or cultivation methods. We observed the photosynthetic physiology of nutrient replete Phaeodactylum tricornutum growing in light environments that mimic those found in rapidly mixing, outdoor, low biomass photobioreactors. We found little evidence for photoinhibition or non-photochemical quenching in situ, suggesting photosynthesis remains highly efficient throughout the day. Cells doubled theirmore » organic carbon from dawn to dusk and a small percentage – around 20% – of this carbon was allocated to carbohydrates or triacylglycerol. We thus conclude that the self-shading provided by dense culturing of P. tricornutum inhibits the induction of photodamage, and energy dissipation processes that would otherwise lower productivity in an outdoor photobioreactor.« less
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Jallet, Denis; Caballero, Michael A.; Gallina, Alessandra A.; ...
2016-06-11
Photosynthetic microbes respond to changing light environments to balance photosynthetic process with light induced damage and photoinhibition. There have been very few characterizations of photosynthetic physiology or biomass partitioning during the day in mass culture. Understanding the constraints on photosynthetic efficiency and biomass accumulation are necessary for engineering superior strains or cultivation methods. We observed the photosynthetic physiology of nutrient replete Phaeodactylum tricornutum growing in light environments that mimic those found in rapidly mixing, outdoor, low biomass photobioreactors. We found little evidence for photoinhibition or non-photochemical quenching in situ, suggesting photosynthesis remains highly efficient throughout the day. Cells doubled theirmore » organic carbon from dawn to dusk and a small percentage – around 20% – of this carbon was allocated to carbohydrates or triacylglycerol. We thus conclude that the self-shading provided by dense culturing of P. tricornutum inhibits the induction of photodamage, and energy dissipation processes that would otherwise lower productivity in an outdoor photobioreactor.« less
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System implications of aperture-shade design for the SIRTF Observatory
NASA Technical Reports Server (NTRS)
Lee, J. H.; Brooks, W. F.; Maa, S.
1987-01-01
The 1-m-aperture Space Infrared Telescope Facility (SIRTF) will operate with a sensitivity limited only by the zodiacal background. This sensitivity requirement places severe restrictions on the amount of stray light which can reach the focal plane from off-axis sources such as the sun or earth limb. In addition, radiation from these sources can degrade the lifetime of the telescope and instrument cryogenic system which is now planned for two years before the first servicing. Since the aperture of the telescope represents a break in the telescope insulation system and is effectively the first element in the optical train, the aperture shade is a key system component. The mass, length, and temperature of the shade should be minimized to reduce system cost while maximizing the telescope lifetime and stray light performance. The independent geometric parameters that characterize an asymmetrical shade for a 600 km, 28 deg orbit were identified, and the system sensitivity to the three most important shade parameters were explored. Despite the higher heat loads compared to previously studied polar orbit missions, the analysis determined that passive radiators of a reasonable size are sufficient to meet the system requirements. An optimized design for the SIRTF mission, based on the sensitivity analysis, is proposed.
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Trouwborst, Govert; Oosterkamp, Joke; Hogewoning, Sander W; Harbinson, Jeremy; van Ieperen, Wim
2010-03-01
Mathematical models of light attenuation and canopy photosynthesis suggest that crop photosynthesis increases by more uniform vertical irradiance within crops. This would result when a larger proportion of total irradiance is applied within canopies (interlighting) instead of from above (top lighting). These irradiance profiles can be generated by Light Emitting Diodes (LEDs). We investigated the effects of interlighting with LEDs on light interception, on vertical gradients of leaf photosynthetic characteristics and on crop production and development of a greenhouse-grown Cucumis sativus'Samona' crop and analysed the interaction between them. Plants were grown in a greenhouse under low natural irradiance (winter) with supplemental irradiance of 221 micromol photosynthetic photon flux m(-2) s(-1) (20 h per day). In the interlighting treatment, LEDs (80% Red, 20% Blue) supplied 38% of the supplemental irradiance within the canopy with 62% as top lighting by High-Pressure Sodium (HPS)-lamps. The control was 100% top lighting (HPS lamps). We measured horizontal and vertical light extinction as well as leaf photosynthetic characteristics at different leaf layers, and determined total plant production. Leaf mass per area and dry mass allocation to leaves were significantly greater but leaf appearance rate and plant length were smaller in the interlighting treatment. Although leaf photosynthetic characteristics were significantly increased in the lower leaf layers, interlighting did not increase total biomass or fruit production, partly because of a significantly reduced vertical and horizontal light interception caused by extreme leaf curling, likely because of the LED-light spectrum used, and partly because of the relatively low irradiances from above.
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Microclimate influence on mineral and metabolic profiles of grape berries.
Pereira, G E; Gaudillere, J-P; Pieri, P; Hilbert, G; Maucourt, M; Deborde, C; Moing, A; Rolin, D
2006-09-06
The grape berry microclimate is known to influence berry quality. The effects of the light exposure of grape berry clusters on the composition of berry tissues were studied on the "Merlot" variety grown in a vineyard in Bordeaux, France. The light exposure of the fruiting zone was modified using different intensities of leaf removal, cluster position relative to azimuth, and berry position in the cluster. Light exposures were identified and classified by in situ measurements of berry temperatures. Berries were sampled at maturity (>19 Brix) for determination of skin and/or pulp chemical and metabolic profiles based on (1) chemical and physicochemical measurement of minerals (N, P, K, Ca, Mg), (2) untargeted 1H NMR metabolic fingerprints, and HPLC targeted analyses of (3) amino acids and (4) phenolics. Each profile defined by partial least-square discriminant analysis allowed us to discriminate berries from different light exposure. Discriminant compounds between shaded and light-exposed berries were quercetin-3-glucoside, kaempferol-3-glucoside, myricetin-3-glucoside, and isorhamnetin-3-glucoside for the phenolics, histidine, valine, GABA, alanine, and arginine for the amino acids, and malate for the organic acids. Capacities of the different profiling techniques to discriminate berries were compared. Although the proportion of explained variance from the 1H NMR fingerprint was lower compared to that of chemical measurements, NMR spectroscopy allowed us to identify lit and shaded berries. Light exposure of berries increased the skin and pulp flavonols, histidine and valine contents, and reduced the organic acids, GABA, and alanine contents. All the targeted and nontargeted analytical data sets used made it possible to discriminate sun-exposed and shaded berries. The skin phenolics pattern was the most discriminating and allowed us to sort sun from shade berries. These metabolite classes can be used to qualify berries collected in an undetermined environment. The physiological significance of light and temperature effects on berry composition is discussed.
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NASA Astrophysics Data System (ADS)
Vuellers, Felix; Gomard, Guillaume; Preinfalk, Jan B.; Klampaftis, Efthymios; Worgull, Matthias; Richards, Bryce S.; Hölscher, Hendrik; Kavalenka, Maryna N.
2017-02-01
Combining high optical transmission, water-repellency and self-cleaning is of great interest for optoelectronic devices operating in outdoor conditions, such as photovoltaics where shading can significantly reduce the power output. The surface of water plant Pistia stratiotes combines these functionalities through a dense layer of transparent microhairs. It renders the surface superhydrophobic without affecting absorption of sunlight necessary for photosynthesis. Inspired by this surface, we fabricated a superhydrophobic flexible thin nanofur film made from optical grade polycarbonate using a scalable combination of hot embossing and hot pulling techniques. During fabrication, heated sandblasted steel plates locally elongate softened polymer, thus covering its surface in microcavities surrounded by high aspect ratio micro- and nanohairs. The superhydrophobic nanofur exhibits contact angles of (166+/-6°), low sliding angles (<6°) and is self-cleaning against various contaminants. The overall transmission of the self-standing nanofur film stands above 85% over the visible range, with 97% of the transmitted light scattered forward. Reflection drops below 4% when coated on a polymeric substrate, which can enhance light extraction in organic light emitting diodes (OLEDs). We report an increase of more than 10% in luminous efficacy for a nanofur coated OLED compared to a bare device. Finally, the nanofur film can be used for enhancing the incoupling of light to solar cells, while additionally providing self-cleaning properties. Optical coupling of the nanofur to a multi-crystalline silicon solar cell results in a 5.8% gain in photocurrent compared to a bare device under normal incidence.
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7 CFR 51.1161 - Discoloration.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 7 Agriculture 2 2013-01-01 2013-01-01 false Discoloration. 51.1161 Section 51.1161 Agriculture... § 51.1161 Discoloration. Discoloration means russeting of a light shade of golden brown caused by rust... scars or other means may be allowed on a greater area, or darker shades may be allowed on a lesser area...
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7 CFR 51.1161 - Discoloration.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 7 Agriculture 2 2014-01-01 2014-01-01 false Discoloration. 51.1161 Section 51.1161 Agriculture... § 51.1161 Discoloration. Discoloration means russeting of a light shade of golden brown caused by rust... scars or other means may be allowed on a greater area, or darker shades may be allowed on a lesser area...
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Learning Different Light Prior Distributions for Different Contexts
ERIC Educational Resources Information Center
Kerrigan, Iona S.; Adams, Wendy J.
2013-01-01
The pattern of shading across an image can provide a rich sense of object shape. Our ability to use shading information is remarkable given the infinite possible combinations of illumination, shape and reflectance that could have produced any given image. Illumination can change dramatically across environments (e.g. indoor vs. outdoor) and times…
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High Performance Building Mockup in FLEXLAB
DOE Office of Scientific and Technical Information (OSTI.GOV)
McNeil, Andrew; Kohler, Christian; Lee, Eleanor S.
Genentech has ambitious energy and indoor environmental quality performance goals for Building 35 (B35) being constructed by Webcor at the South San Francisco campus. Genentech and Webcor contracted with the Lawrence Berkeley National Laboratory (LBNL) to test building systems including lighting, lighting controls, shade fabric, and automated shading controls in LBNL’s new FLEXLAB facility. The goal of the testing is to ensure that the systems installed in the new office building will function in a way that reduces energy consumption and provides a comfortable work environment for employees.
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A Study on AR 3D Objects Shading Method Using Electronic Compass Sensor
NASA Astrophysics Data System (ADS)
Jung, Sungmo; Kim, Seoksoo
More effective communications can be offered to users by applying NPR (Non-Photorealistic Rendering) methods to 3D graphics. Thus, there has been much research on how to apply NPR to mobile contents. However, previous studies only propose cartoon rendering for pre-treatment with no consideration for directions of light in the surrounding environment. In this study, therefore, ECS(Electronic Compass Sensor) is applied to AR 3D objects shading in order to define directions of light as per time slots for assimilation with the surrounding environment.
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The effect of shade on chlorophyll and anthocyanin content of upland red rice
NASA Astrophysics Data System (ADS)
Muhidin; Syam'un, E.; Kaimuddin; Musa, Y.; Sadimantara, G. R.; Usman; Leomo, S.; Rakian, T. C.
2018-02-01
Upland red rice (Oryza sativa) is a staple food and contains anthocyanin, which can act as antioxidants, plays an important role both for the plant itself and for human health. Levels of antioxidants in rice can be affected by the availability of light. The results showed that the difference of shade, cultivar, and interaction both significantly affect the content of chlorophyll a, chlorophyll b and total chlorophyll. The results also showed that shade could increase chlorophyll in all cultivars tested. The highest levels of chlorophyll a were present in the moderate shade level (n2), then decreased at the shelter level (n3) and increased again at high levels (n4). While on chlorophyll content b, it appears that shade increased chlorophyll b in all cultivars tested and this increase was linear to the increase of shade. The shade treatment may increase the anthocyanin content and the increase depending on the type of cultivar. Increased levels of anthocyanin highest due to shade occurred on Jangkobembe cultivar. The original level of anthocyanin on Jangkobembe cultivar averaged 0.096 mg g-1 increased to 2.487 mg g-1 or increased 26 fold. It is concluded that the shade had a significant effect on the chlorophyll and anthocyanin content.
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[Research on the designing method of a special shade guide for tooth whitening].
Xu, Yingxin
2015-10-01
To investigate a method of designing an accurate and scientific shade guide, especially used for judging the effect of tooth whitening, by analyzing the colorimetric values of discolored teeth statistically. One hundred thirty-six pictures of patients who had been receiving the Beyond cold light whitening treatment from February 2009 to July 2014 were analyzed, including 25 tetracycline teeth, 61 mottled-enamel teeth, and 50 yellow teeth. The colorimetric values of discolored teeth were measured. The L* values of shade tabs were calculated by hierarchical clustering of those of discolored teeth. The a* and b* values of shade tabs were the mean of those observed for discolored teeth. Accordingly, different shade guides were designed for each type of discolored teeth, and the effects were evaluated. A statistically significant difference in colorimetric values was found among the three types of discolored teeth. Compared with the Vitapan Classical shade guide, the shade guides designed through the present method were more scientific and accurate in judging the effect of tooth whitening. Moreover, the arrangement of shade tabs was more logical, and the color difference between shade tabs and discolored teeth was smaller. The proposed designing method is theoretically feasible, although its clinical effect has yet to be proven.
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Schrameyer, Verena; York, Paul H; Chartrand, Kathryn; Ralph, Peter J; Kühl, Michael; Brodersen, Kasper Elgetti; Rasheed, Michael A
2018-05-01
Seagrass meadows increasingly face reduced light availability as a consequence of coastal development, eutrophication, and climate-driven increases in rainfall leading to turbidity plumes. We examined the impact of reduced light on above-ground seagrass biomass and sediment biogeochemistry in tropical shallow- (∼2 m) and deep-water (∼17 m) seagrass meadows (Green Island, Australia). Artificial shading (transmitting ∼10-25% of incident solar irradiance) was applied to the shallow- and deep-water sites for up to two weeks. While above-ground biomass was unchanged, higher diffusive O 2 uptake (DOU) rates, lower O 2 penetration depths, and higher volume-specific O 2 consumption (R) rates were found in seagrass-vegetated sediments as compared to adjacent bare sand (control) areas at the shallow-water sites. In contrast, deep-water sediment characteristics did not differ between bare sand and vegetated sites. At the vegetated shallow-water site, shading resulted in significantly lower hydrogen sulphide (H 2 S) levels in the sediment. No shading effects were found on sediment biogeochemistry at the deep-water site. Overall, our results show that the sediment biogeochemistry of shallow-water (Halodule uninervis, Syringodium isoetifolium, Cymodocea rotundata and C. serrulata) and deep-water (Halophila decipiens) seagrass meadows with different species differ in response to reduced light. The light-driven dynamics of the sediment biogeochemistry at the shallow-water site could suggest the presence of a microbial consortium, which might be stimulated by photosynthetically produced exudates from the seagrass, which becomes limited due to lower seagrass photosynthesis under shaded conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.
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Boxler-Baldoma, Carmen; Lütz, Cornelius; Heumann, Hans-Günther; Siefermann-Harms, Dorothea
2006-02-01
The correlation between structural changes of the vascular bundles and needle yellowing was examined for needles of damaged spruce (Picea abies (L.) Karst.) growing at a Mg-deficient and ozone polluted mountain site in the Central Black Forest (840m a.s.l.). In the previous year's sun-exposed needles, the following sequence of events was observed: (1) rapid needle yellowing, (2) hypertrophy and anomalous divisions of cambium cells, (3) phloem collapse, and, (4) production of atypical xylem tracheids. Under defined shade (reduction of the photosynthetically active photon flux density of the ambient light by 85-90%), the needles remained green, while the phloem collapsed completely within the first 6 weeks of shading; subsequently, a reversal of the collapse was observed. Under both light conditions, the content of Mg not bound to chlorophyll (Mg(free)) was in the range of 0.1 mg g(-1) needle dry matter, and hardly changed throughout the investigation period. After Mg fertilization, the Mg(free) level of the previous year's needles increased to 0.2 mg g(-1) dry matter, the light-exposed needles remained green, and the vascular bundles developed no anomalies. The data show that the rapid needle yellowing of ozone-exposed Mg-deficient needles did not depend on the collapse of the phloem. Mg deficiency played a key role in the development of anomalous vascular bundles under light, and also appears to explain the transient changes in sieve cell structure under shade. The role of Mg deficiency, rather than ozone pollution, in the damage of the sieve cells was confirmed in a long-term ozone exposure experiment with young clonal spruce growing under defined conditions.
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NASA Astrophysics Data System (ADS)
Pena Mello Brandão, Luciana; Silva Brighenti, Ludmila; Staehr, Peter Anton; Asmala, Eero; Massicotte, Philippe; Tonetta, Denise; Antônio Rodrigues Barbosa, Francisco; Pujoni, Diego; Fernandes Bezerra-Neto, José
2018-05-01
Despite the increasing understanding about differences in carbon cycling between temperate and tropical freshwater systems, our knowledge on the importance of organic matter (OM) pools on light absorption properties in tropical lakes is very scarce. We performed a factorial mesocosm experiment in a tropical lake (Minas Gerais, Brazil) to evaluate the effects of increased concentrations of allochthonous and autochthonous OM, and differences in light availability on the light absorption characteristics of chromophoric dissolved organic matter (CDOM). Autochthonous OM deriving from phytoplankton ( ˜ Chl a) was stimulated by addition of nutrients, while OM from degradation of terrestrial leaves increased allochthonous OM, and neutral shading was used to manipulate light availability. Effects of the additions and shading on DOC, Chl a, nutrients, total suspended solid concentrations (TSM) and spectral CDOM absorption were monitored every 3 days. CDOM quality was characterized by spectral indices (S250-450, S275-295, S350-450, SR and SUVA254). Effects of carbon sources and shading on the spectral CDOM absorption was investigated through principal component (PCA) and redundancy (RDA) analyses. The two different OM sources affected CDOM quality very differently and shading had minor effects on OM levels, but significant effects on OM quality, especially in combination with nutrient additions. Spectral indices (S250-450 and SR) were mostly affected by allochthonous OM addition. The PCA showed that enrichment by allochthonous carbon had a strong effect on the CDOM spectra in the range between 300 and 400 nm, while the increase in autochthonous carbon increased absorption at wavelengths below 350 nm. Our study shows that small inputs of allochthonous OM can have large effects on the spectral light absorption compared to large production of autochthonous OM, with important implications for carbon cycling in tropical lakes.
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Achieving the desired colour in discoloured teeth, using leucite-based CAD-CAM laminate systems.
Turgut, Sedanur; Bagis, Bora; Ayaz, Elif Aydogan
2014-01-01
To evaluate the cumulative effect of the abutment tooth and resin cement colour on the resultant optical properties of porcelain laminate veneers (PLVs) fabricated with leucite-based CAD/CAM blocks with different shades and thicknesses. A total of 224 ceramic specimens were prepared from the IPS Empress CAD with four different shades of HT-A1, LT-A1, MT-A1 and Bl-1. Resin composite discs were prepared with shade A3.5. For the cementation, 4 different shades of light-cure resin cements were chosen. L*, a*, and b* values, as well as the chroma (C) and hue (h) values of each cemented ceramic and the A1 shade table, were recorded. L*, Cab* and hab* values of the cemented ceramics were influenced by ceramic shade, ceramic thickness, cement shade, and interaction terms of the three variables. There were significant differences between the 1-mm-thick ceramic veneers that exhibited higher L* and lower Cab* values compared with veneers that were 0.5mm in thickness. Using the Tr shade cement resulted in lower L* and higher Cab* values for all thicknesses and ceramic shades, whereas the WO shade cement resulted in higher values. The selected colour of a laminate restoration is significantly affected by the ceramic shade, ceramic thickness and resin cement shade. Using the WO shade resin cement seems to be more effective in masking the discoloured abutment tooth. Clinicians should also select the translucency level of the ceramic block with the shade when a leucite-based CAD/CAM system is chosen to treat a discoloured tooth. Copyright © 2013 Elsevier Ltd. All rights reserved.
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Esthetics: patients' perceptions of dental attractiveness.
Dunn, W J; Murchison, D F; Broome, J C
1996-09-01
The importance of dentofacial attractiveness to the psychosocial well-being of an individual has been well established. Very little information is available regarding dental patient perceptions of a pleasing esthetic image. The purpose of this study was to identify factors distinctive to attractive smiles versus unattractive smiles, as perceived by patients. Standardized format photographs (5 x 7 in, matte finish, at f-32 and 1:2 magnification) of eight male and eight female smiles, framing only lips and teeth, were viewed by 297 subjects. The smiles exhibited differences in symmetry, tooth shade, number of teeth displayed, and height of maxillary lip line, and included both restored and unrestored teeth. Respondents ranked the photographs in order from most to least appealing appearance. Respondents viewed each series of photographs in a similar lighting and time period. A questionnaire identified the respondent's age, sex, race, education, income, and home town. Twenty-five demographic groups were established from the information in the questionnaire. Data were analyzed using stepwise discriminant analysis to determine the combination of smile characteristics that best predicted the ranking. The same female smile was chosen as the most attractive by 24 of the 25 demographic groups. This smile is characterized by natural teeth having light shade, high lip line, a large display of teeth, and radiating symmetry. Two female smiles typified by darker shade and asymmetry were rated by all groups as being least attractive. Two male smiles were judged equal as the most pleasing esthetically. Respondents favored those smiles characterized by light shade, a moderate display of teeth, moderate lip line, and a symmetrical arrangement of teeth. One male smile characterized by darker shade was rated as least attractive. In all cases, tooth shade was the most important factor, followed in sequence by unrestored natural teeth and number of teeth displayed. No correlation was found to exist between specific demographic groups and smile variables.
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NASA Technical Reports Server (NTRS)
Kuhn, H.; Galston, A. W.
1992-01-01
Etiolated pea seedlings require transformation of Pr phytochrome to Pfr before they display optimal phototropic response to unilateral blue light. This study investigates the possible role of auxin transport in explaining these phenomena. Labeled [2-14C]IAA applied to the intact terminal buds of dark-grown and red light-treated pea seedlings was measured 210 min later on the shaded and illuminated sides of the epicotyl as a function of direction and duration of irradiation with blue light. Totally darkened epicotyls show an asymmetry in distribution of radioactivity in the upper growth zone of the epicotyl, in favor of the side under the concave part of the apical hook. Red light, which greatly potentiates curvature toward subsequent unilateral blue light, lowers this asymmetry. Blue light directed to the epicotyl of red-pretreated plants in a plane parallel to the hook and from the side bearing the convex portion of the hook induces positive phototropic curvature as well as a surplus of radioactivity on the illuminated side of the upper epicotyl and on the shaded side of the lower growth zone of the epicotyl. Light directed to the side bearing the concave part of the hook also causes an accumulation of counts in the upper part of the lighted side but produces neither curvature of the epicotyl nor accumulation of counts in the lower shaded side. Because of this built-in physiological asymmetry in the growth zone just below the apical hook, it is difficult to explain the effects of red and blue light on curvature in terms of patterns of auxin distribution alone.
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Kuhn, H; Galston, A W
1992-01-01
Etiolated pea seedlings require transformation of Pr phytochrome to Pfr before they display optimal phototropic response to unilateral blue light. This study investigates the possible role of auxin transport in explaining these phenomena. Labeled [2-14C]IAA applied to the intact terminal buds of dark-grown and red light-treated pea seedlings was measured 210 min later on the shaded and illuminated sides of the epicotyl as a function of direction and duration of irradiation with blue light. Totally darkened epicotyls show an asymmetry in distribution of radioactivity in the upper growth zone of the epicotyl, in favor of the side under the concave part of the apical hook. Red light, which greatly potentiates curvature toward subsequent unilateral blue light, lowers this asymmetry. Blue light directed to the epicotyl of red-pretreated plants in a plane parallel to the hook and from the side bearing the convex portion of the hook induces positive phototropic curvature as well as a surplus of radioactivity on the illuminated side of the upper epicotyl and on the shaded side of the lower growth zone of the epicotyl. Light directed to the side bearing the concave part of the hook also causes an accumulation of counts in the upper part of the lighted side but produces neither curvature of the epicotyl nor accumulation of counts in the lower shaded side. Because of this built-in physiological asymmetry in the growth zone just below the apical hook, it is difficult to explain the effects of red and blue light on curvature in terms of patterns of auxin distribution alone.
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Redwood seedling responses to light patterns and intensities
Ronald W. Boldenow; Joe R. McBride
2017-01-01
Coast redwood (Sequoia sempervirens (D. Don) Endl.) seedlings were grown from seed in controlled environments with 16 hour photoperiods using three light patterns that mimicked full shade (constant light level), intermittent high light such as long duration sun flecks (low light with 15 minutes of intense light every 2 hours), and large...
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Morice, Antoine H P; Wallet, Grégory; Montagne, Gilles
2014-04-30
While it has been shown that the Global Optic Flow Rate (GOFR) is used in the control of self-motion speed, this study examined its relevance in the control of interceptive actions while walking. We asked participants to intercept approaching targets by adjusting their walking speed in a virtual environment, and predicted that the influence of the GOFR depended on their interception strategy. Indeed, unlike the Constant Bearing Angle (CBA), the Modified Required Velocity (MRV) strategy relies on the perception of self-displacement speed. On the other hand, the CBA strategy involves specific speed adjustments depending on the curvature of the target's trajectory, whereas the MRV does not. We hypothesized that one strategy is selected among the two depending on the informational content of the environment. We thus manipulated the curvature and display of the target's trajectory, and the relationship between physical walking speed and the GOFR (through eye height manipulations). Our results showed that when the target trajectory was not displayed, walking speed profiles were affected by curvature manipulations. Otherwise, walking speed profiles were less affected by curvature manipulations and were affected by the GOFR manipulations. Taken together, these results show that the use of the GOFR for intercepting a moving target while walking depends on the informational content of the environment. Finally we discuss the complementary roles of these two perceptual-motor strategies. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
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Tian, Yue Yue; Zhang, Li Xia; Zhang, Zheng Qun; Qiao, Ming Ming; Fan, Yan Gen
2017-03-18
In order to ensure the suitable shade model for 'Huangjinya' tea plant in Shandong Province, black or blue shading net at 55%, 70% or 85% shading rates was selected to recover tea garden in summer and autumn, then micro-climate of tea garden, leaf color, chlorophyll fluorescence parameters, growth status and biochemical composition of tea shoots were investigated.The results showed that compared with the control, light intensity and air temperature in tea garden, leaf temperature of tea plants in different shading treatments significantly decreased, while air humidity in tea garden increased. The contents of chlorophyll in the tea leaves were obviously increased with increasing the shading rate, which resulted in the leaf color becoming green. The yellowing characteristics and biochemical quality of 'Huangjinya' tea plants could be well kept in 55% shading treatments. In 70% shading treatments, 'Huangjinya' tea plants had better growth situation and higher yield with no photo-inhibition. Compared with the blue shading treatments, black shading treatments could obviously promote the growth of 'Huangjinya' tea plants, keep yellowing characteristics, and improve the quality. Therefore, the 70% black shading treatment (daily PAR values of 1.2-3.5 ten thousand lx) was appropriate for promoting the growth of 'Huangjinya' tea plants at the seedling stage. For mature tea plants, the 55% black shading treatment (daily PAR values of 1.8-5.5 ten thousand lx) could be used to keep the yellowing characteristics and to improve biochemical quality effectively, so as to give full play to its variety characteristics, to achieve goal of high quality and high yield.
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Lusk, Christopher H; Kelly, Jeff W G; Gleason, Sean M
2013-03-01
A trade-off between shade tolerance and growth in high light is thought to underlie the temporal dynamics of humid forests. On the other hand, it has been suggested that tree species sorting on temperature gradients involves a trade-off between growth rate and cold resistance. Little is known about how these two major trade-offs interact. Seedlings of Australian tropical and cool-temperate rainforest trees were grown in glasshouse environments to compare growth versus shade-tolerance trade-offs in these two assemblages. Biomass distribution, photosynthetic capacity and vessel diameters were measured in order to examine the functional correlates of species differences in light requirements and growth rate. Species light requirements were assessed by field estimation of the light compensation point for stem growth. Light-demanding and shade-tolerant tropical species differed markedly in relative growth rates (RGR), but this trend was less evident among temperate species. This pattern was paralleled by biomass distribution data: specific leaf area (SLA) and leaf area ratio (LAR) of tropical species were significantly positively correlated with compensation points, but not those of cool-temperate species. The relatively slow growth and small SLA and LAR of Tasmanian light-demanders were associated with narrow vessels and low potential sapwood conductivity. The conservative xylem traits, small LAR and modest RGR of Tasmanian light-demanders are consistent with selection for resistance to freeze-thaw embolism, at the expense of growth rate. Whereas competition for light favours rapid growth in light-demanding trees native to environments with warm, frost-free growing seasons, frost resistance may be an equally important determinant of the fitness of light-demanders in cool-temperate rainforest, as seedlings establishing in large openings are exposed to sub-zero temperatures that can occur throughout most of the year.
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Patients' perspective on dental aesthetics in a South-Eastern European community.
Dudea, Diana; Lasserre, Jean-François; Alb, Camelia; Culic, Bogdan; Pop Ciutrila, Ioana Sofia; Colosi, Horatiu
2012-07-01
To assess the importance attributed to dental aesthetics by subjects from a Romanian community. In addition, the role played by dental color, the group-distributions based on the self-evaluation of dental color and the previous experience regarding whitening treatments are analysed. A multiple-choice questionnaire was administered to 540 patients in dental offices in Cluj-Napoca, Romania; the subjects were also asked to self-evaluate their dental shade, using a set of images as a comparison. Answers to the questionnaires were statistically analysed using Microsoft Excel and SPSS 13.00 (Pearson's chi-square test, Fisher's exact test, Kendall's tau b). From the participants, 17.96% were motivated by aesthetic reasons to ask for treatment; most of the patients evaluated their smile as "acceptable" (38.51%) or "having some defects" (29.44%) and were self-included in groups of medium and dark shades (33.7% and 33.89%, respectively). Whilst 22.40% of the subjects considered the dental color as being the most evident defect of their dentition, 39.07% indicated a self-perception of "an abnormal dental shade". A strong correlation between darker self-assessed tooth color-groups and the self-perception of an abnormal tooth color was found (Chi square p≪0.001, Kendall's tau-c=0.44, with p≪0.001). Previous whitening treatments were reported by 8.88% of the subjects. Among patients who wanted to improve one of their oral functions, the majority requested changes in aesthetics. Dental shade is one of the aspects recognized as problematic by the participants, but nonetheless the percentage of patients who had previously benefited by whitening treatments was moderate. Copyright © 2012 Elsevier Ltd. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Karve, Abhijit A; Weston, David; Jawdy, Sara
2012-01-01
Shade avoidance signaling in higher plants involves perception of the incident red/far-red (R/FR) light by phytochromes and the modulation of downstream transcriptional networks to regulate developmental plasticity in relation to heterogeneous light environments. In this study, we characterized the expression and functional features of Populus phytochrome (PHY) gene family as well as the transcriptional responses of Populus to the changes in R/FR light. Expression data indicated that PHYA is the predominant PHY in the dark grown Populus seedling whereas PHYBs are most abundant in mature tissue types. Out of three Populus PHYs, PHYA is light labile and localized to cytosolmore » in dark whereas both PHYB1 and PHYB2 are light stable and are localized to nucleus in mesophyll protoplasts. When expressed in Arabidopsis, PHYB1 rescued Arabidopsis phyB mutant phenotype whereas PHYB2 did not, suggesting functional diversification between these two gene family members. However, phenotypes of transgenic Populus lines with altered expression of PHYB1, PHYB2 or both and the expression of candidate shade response genes in these transgenic lines suggest that PHYB1 and PHYB2 may have distinct yet overlapping functions. The RNAseq results and analysis of Populus exposed to enriched-FR light indicate that genes associated in cell wall modification and brassinosteroid signaling were induced under far red light. Overall our data indicate that Populus transcriptional responses are at least partially conserved with Arabidopsis.« less
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Losciale, Pasquale; Chow, Wah Soon; Corelli Grappadelli, Luca
2010-01-01
The productivity of fruit trees is a linear function of the light intercepted, although the relationship is less tight when greater than 50% of available light is intercepted. This paper investigates the management of light energy in peach using the measurement of whole-tree light interception and gas exchange, along with the absorbed energy partitioning at the leaf level by concurrent measurements of gas exchange and chlorophyll fluorescence. These measurements were performed on trees of a custom-built ‘asymmetric’ orchard. Whole-tree gas exchange for north–south, vertical canopies (C) was similar to that for canopies intercepting the highest irradiance in the morning hours (W), but trees receiving the highest irradiance in the afternoon (E) had the highest net photosynthesis and transpiration while maintaining a water use efficiency (WUE) comparable to the other treatments. In the W trees, 29% and 8% more photosystems were damaged than in C and E trees, respectively. The quenching partitioning revealed that the non-photochemical quenching (NPQ) played the most important role in excess energy dissipation, but it was not fully active at low irradiance, possibly due to a sub-optimal trans-thylakoid ΔpH. The non-net carboxylative mechanisms (NC) appeared to be the main photoprotective mechanisms at low irradiance levels and, probably, they could facilitate the establishment of a trans-thylakoid ΔpH more appropriate for NPQ. These findings support the conclusion that irradiance impinging on leaves may be excessive and can cause photodamage, whose repair requires energy in the form of carbohydrates that are thereby diverted from tree growth and productivity. PMID:20124356
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Shaded Relief of Rio Sao Francisco, Brazil
2000-02-14
This topographic image acquired by SRTM shows an area south of the Sao Francisco River in Brazil. The scrub forest terrain shows relief of about 400 meters (1300 feet). Areas such as these are difficult to map by traditional methods because of frequent cloud cover and local inaccessibility. This region has little topographic relief, but even subtle changes in topography have far-reaching effects on regional ecosystems. The image covers an area of 57 km x 79 km and represents one quarter of the 225 km SRTM swath. Colors range from dark blue at water level to white and brown at hill tops. The terrain features that are clearly visible in this image include tributaries of the Sao Francisco, the dark-blue branch-like features visible from top right to bottom left, and on the left edge of the image, and hills rising up from the valley floor. The San Francisco River is a major source of water for irrigation and hydroelectric power. Mapping such regions will allow scientists to better understand the relationships between flooding cycles, forestation and human influences on ecosystems. This shaded relief image was generated using topographic data from the Shuttle Radar Topography Mission. A computer-generated artificial light source illuminates the elevation data to produce a pattern of light and shadows. Slopes facing the light appear bright, while those facing away are shaded. On flatter surfaces, the pattern of light and shadows can reveal subtle features in the terrain. Shaded relief maps are commonly used in applications such as geologic mapping and land use planning. http://photojournal.jpl.nasa.gov/catalog/PIA02700
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Brouwer, Bastiaan; Gardeström, Per; Keech, Olivier
2014-01-01
Phytochrome is thought to control the induction of leaf senescence directly, however, the signalling and molecular mechanisms remain unclear. In the present study, an ecophysiological approach was used to establish a functional connection between phytochrome signalling and the physiological processes underlying the induction of leaf senescence in response to shade. With shade it is important to distinguish between complete and partial shading, during which either the whole or only a part of the plant is shaded, respectively. It is first shown here that, while PHYB is required to maintain chlorophyll content in a completely shaded plant, only PHYA is involved in maintaining the leaf chlorophyll content in response to partial plant shading. Second, it is shown that leaf yellowing associated with strong partial shading in phyA-mutant plants actually correlates to a decreased biosynthesis of chlorophyll rather than to an increase of its degradation. Third, it is shown that the physiological impact of this decreased biosynthesis of chlorophyll in strongly shaded phyA-mutant leaves is accompanied by a decreased capacity to adjust the Light Compensation Point. However, the increased leaf yellowing in phyA-mutant plants is not accompanied by an increase of senescence-specific molecular markers, which argues against a direct role of PHYA in inducing leaf senescence in response to partial shade. In conclusion, it is proposed that PHYA, but not PHYB, is essential for fine-tuning the chlorophyll biosynthetic pathway in response to partial shading. In turn, this mechanism allows the shaded leaf to adjust its photosynthetic machinery to very low irradiances, thus maintaining a positive carbon balance and repressing the induction of leaf senescence, which can occur under prolonged periods of shade. PMID:24604733
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USDA-ARS?s Scientific Manuscript database
Using shade cloths of different densities, potted individuals of Murraya exotica (Rutaceae) were exposed to levels of photosynthetic radiation (PAR) varying from 48 µmol photons per meter2 per second to 1562 µmol photons per meter2 per second (average of three readings taken at noon during condition...
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Matus, José Tomás; Loyola, Rodrigo; Vega, Andrea; Peña-Neira, Alvaro; Bordeu, Edmundo; Arce-Johnson, Patricio; Alcalde, José Antonio
2009-01-01
Anthocyanins, flavan-3-ols, and flavonols are the three major classes of flavonoid compounds found in grape berry tissues. Several viticultural practices increase flavonoid content in the fruit, but the underlying genetic mechanisms responsible for these changes have not been completely deciphered. The impact of post-veraison sunlight exposure on anthocyanin and flavonol accumulation in grape berry skin and its relation to the expression of different transcriptional regulators known to be involved in flavonoid synthesis was studied. Treatments consisting of removing or moving aside the basal leaves which shade berry clusters were applied. Shading did not affect sugar accumulation or gene expression of HEXOSE TRANSPORTER 1, although in the leaf removal treatment, these events were retarded during the first weeks of ripening. Flavonols were the most drastically reduced flavonoids following shading and leaf removal treatments, related to the reduced expression of FLAVONOL SYNTHASE 4 and its putative transcriptional regulator MYB12. Anthocyanin accumulation and the expression of CHS2, LDOX, OMT, UFGT, MYBA1, and MYB5a genes were also affected. Other regulatory genes were less affected or not affected at all by these treatments. Non-transcriptional control mechanisms for flavonoid synthesis are also suggested, especially during the initial stages of ripening. Although berries from the leaf removal treatment received more light than shaded fruits, malvidin-3-glucoside and total flavonol content was reduced compared with the treatment without leaf removal. This work reveals that flavonol-related gene expression responds rapidly to field changes in light levels, as shown by the treatment in which shaded fruits were exposed to light in the late stages of ripening. Taken together, this study establishes MYB-specific responsiveness for the effect of sun exposure and sugar transport on flavonoid synthesis. PMID:19129169
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Sun/shade conditions affect recruitment and local adaptation of a columnar cactus in dry forests.
Miranda-Jácome, Antonio; Montaña, Carlos; Fornoni, Juan
2013-02-01
Facilitation among plants in water-limited environments (i.e. where evapotranspiration overcomes the availability of water during the growing season) has been considered a local adaptation to water and light conditions. Among cacti, early life-history stages can benefit from the facilitative effects of nurse plants that reduce solar radiation and water stress. However, whether light condition itself acts as an agent of selection through facilitation remains untested. The aim of this study was to determine (1) whether light conditions affect seedling recruitment, (2) whether the positive effect of shade on seedling recruitment is more intense under more stressful conditions and (3) whether shade condition (facilitation) reduces the magnitude of local adaptation on seedling recruitment relative to full sunlight conditions. A reciprocal transplant experiment, coupled with the artificial manipulation of sun/shade conditions, was performed to test for the effects of local adaptation on germination, seedling survival and growth, using two demes of the columnar cactus Pilosocereus leucocephalus, representing different intensities of stressful conditions. Full sunlight conditions reduced recruitment success and supported the expectation of lower recruitment in more stressful environments. Significant local adaptation was mainly detected under full sunlight conditions, indicating that this environmental factor acts as an agent of selection at both sites. The results supported the expectation that the magnitude of local adaptation, driven by the effects of facilitative nurse plants, is less intense under reduced stressful conditions. This study is the first to demonstrate that sun/shade conditions act as a selective agent accounting for local adaptation in water-limited environments, and that facilitation provided by nurse plants in these environments can attenuate the patterns of local adaptation among plants benefiting from the nurse effect.
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Matus, José Tomás; Loyola, Rodrigo; Vega, Andrea; Peña-Neira, Alvaro; Bordeu, Edmundo; Arce-Johnson, Patricio; Alcalde, José Antonio
2009-01-01
Anthocyanins, flavan-3-ols, and flavonols are the three major classes of flavonoid compounds found in grape berry tissues. Several viticultural practices increase flavonoid content in the fruit, but the underlying genetic mechanisms responsible for these changes have not been completely deciphered. The impact of post-veraison sunlight exposure on anthocyanin and flavonol accumulation in grape berry skin and its relation to the expression of different transcriptional regulators known to be involved in flavonoid synthesis was studied. Treatments consisting of removing or moving aside the basal leaves which shade berry clusters were applied. Shading did not affect sugar accumulation or gene expression of HEXOSE TRANSPORTER 1, although in the leaf removal treatment, these events were retarded during the first weeks of ripening. Flavonols were the most drastically reduced flavonoids following shading and leaf removal treatments, related to the reduced expression of FLAVONOL SYNTHASE 4 and its putative transcriptional regulator MYB12. Anthocyanin accumulation and the expression of CHS2, LDOX, OMT, UFGT, MYBA1, and MYB5a genes were also affected. Other regulatory genes were less affected or not affected at all by these treatments. Non-transcriptional control mechanisms for flavonoid synthesis are also suggested, especially during the initial stages of ripening. Although berries from the leaf removal treatment received more light than shaded fruits, malvidin-3-glucoside and total flavonol content was reduced compared with the treatment without leaf removal. This work reveals that flavonol-related gene expression responds rapidly to field changes in light levels, as shown by the treatment in which shaded fruits were exposed to light in the late stages of ripening. Taken together, this study establishes MYB-specific responsiveness for the effect of sun exposure and sugar transport on flavonoid synthesis.
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Sun/shade conditions affect recruitment and local adaptation of a columnar cactus in dry forests
Miranda-Jácome, Antonio; Montaña, Carlos; Fornoni, Juan
2013-01-01
Background and Aims Facilitation among plants in water-limited environments (i.e. where evapotranspiration overcomes the availability of water during the growing season) has been considered a local adaptation to water and light conditions. Among cacti, early life-history stages can benefit from the facilitative effects of nurse plants that reduce solar radiation and water stress. However, whether light condition itself acts as an agent of selection through facilitation remains untested. The aim of this study was to determine (1) whether light conditions affect seedling recruitment, (2) whether the positive effect of shade on seedling recruitment is more intense under more stressful conditions and (3) whether shade condition (facilitation) reduces the magnitude of local adaptation on seedling recruitment relative to full sunlight conditions. Methods A reciprocal transplant experiment, coupled with the artificial manipulation of sun/shade conditions, was performed to test for the effects of local adaptation on germination, seedling survival and growth, using two demes of the columnar cactus Pilosocereus leucocephalus, representing different intensities of stressful conditions. Key Results Full sunlight conditions reduced recruitment success and supported the expectation of lower recruitment in more stressful environments. Significant local adaptation was mainly detected under full sunlight conditions, indicating that this environmental factor acts as an agent of selection at both sites. Conclusions The results supported the expectation that the magnitude of local adaptation, driven by the effects of facilitative nurse plants, is less intense under reduced stressful conditions. This study is the first to demonstrate that sun/shade conditions act as a selective agent accounting for local adaptation in water-limited environments, and that facilitation provided by nurse plants in these environments can attenuate the patterns of local adaptation among plants benefiting from the nurse effect. PMID:23223204
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Light-scattering properties of a Venetian blind slat used for daylighting applications
DOE Office of Scientific and Technical Information (OSTI.GOV)
Nilsson, Annica M.; Jonsson, Jacob C.
2010-12-15
The low cost, simplicity, and aesthetic appearance of external and internal shading devices, make them commonly used for daylighting and glare-control applications. Shading devices, such as Venetian blinds, screens, and roller shades, generally exhibit light scattering and/or light redirecting properties. This requires the bi-directional scattering distribution function (BSDF) of the material to be known in order to accurately predict the daylight distribution and energy flow through the fenestration system. Acquiring the complete BSDF is not a straightforward task, and to complete the process it is often required that a model is used to complement the measured data. In this project,more » a Venetian blind slat with a white top surface and a brushed aluminum bottom surface was optically characterized. A goniophotometer and an integrating sphere spectrophotometer were used to determine the angle resolved and hemispherical reflectance of the sample, respectively. The acquired data were fitted to a scattering model providing one Lambertian and one angle dependent description of the surface properties. These were used in combination with raytracing to obtain the complete BSDFs of the Venetian blind system. (author)« less
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Yang, Feng; Fan, Yuanfang; Wu, Xiaoling; Cheng, Yajiao; Liu, Qinlin; Feng, Lingyang; Chen, Junxu; Wang, Zhonglin; Wang, Xiaochun; Yong, Taiwen; Liu, Weiguo; Liu, Jiang; Du, Junbo; Shu, Kai; Yang, Wenyu
2018-01-01
The intensity and quality (red to far-red (R/Fr) ratio) of light directly affect growth of plant under shading. Gibberellins (GAs) and auxin [indole-3-acetic acid (IAA)] play important roles in mediating the shading adaptive responses of plants. Thus, the intensity and quality of the uncoupling light from shading were assessed to identify the influence of each component on the morphology and matter distribution of the leaf, stem, and petiole. This assessment was based on the changes in endogenous Gibberellin 1 (GA1) and IAA levels. Soybean plants were grown in a growth chamber with four treatments [normal (N), N+Fr, low (L), and L+Fr light]. Results revealed that the reductions in photosynthetically active radiation (PAR) and R/Fr ratio equally increased height and stem mass fractions (SMFs) of the soybean seedling. The light intensity significantly influenced the dry mass per unit area and mass fraction of soybean leaves, whereas the light quality regulated the petiole elongation and mass fraction. Low R/Fr ratio (high Fr light) increased the soybean biomass by improving the photosynthetic assimilation rate and quantum yield of photosystem II. In addition, the IAA and GA1 levels in the leaf, stem, and petiole did not reflect the growth response trends of each tissue toward light intensity and quality; however, trends of the IAA-to-GA1 content ratios were similar to those of the growth and matter allocation of each soybean tissue under different light environments. Therefore, the response of growth and matter allocation of soybean to light intensity and quality may be regulated by the IAA-to-GA1 content ratio in the tissues of the soybean plant. PMID:29441084
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Environmental tolerances of rare and common mangroves along light and salinity gradients.
Dangremond, Emily M; Feller, Ilka C; Sousa, Wayne P
2015-12-01
Although mangroves possess a variety of morphological and physiological adaptations for life in a stressful habitat, interspecific differences in survival and growth under different environmental conditions can shape their local and geographic distributions. Soil salinity and light are known to affect mangrove performance, often in an interactive fashion. It has also been hypothesized that mangroves are intrinsically shade intolerant due to the high physiological cost of coping with saline flooded soils. To evaluate the relationship between stress tolerance and species distributions, we compared responses of seedlings of three widespread mangrove species and one narrow endemic mangrove species in a factorial array of light levels and soil salinities in an outdoor laboratory experiment. The more narrowly distributed species was expected to exhibit a lower tolerance of potentially stressful conditions. Two of the widespread species, Avicennia germinans and Lumnitzera racemosa, survived and grew well at low-medium salinity, regardless of light level, but performed poorly at high salinity, particularly under high light. The third widespread species, Rhizophora mangle, responded less to variation in light and salinity. However, at high salinity, its relative growth rate was low at every light level and none of these plants flushed leaves. As predicted, the rare species, Pelliciera rhizophorae, was the most sensitive to environmental stressors, suffering especially high mortality and reduced growth and quantum yield under the combined conditions of high light and medium-high salinity. That it only thrives under shaded conditions represents an important exception to the prevailing belief that halophytes are intrinsically constrained to be shade intolerant.
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Brown, Caleb E; Mickelbart, Michael V; Jacobs, Douglass F
2014-12-01
Partial canopy cover promotes regeneration of many temperate forest trees, but the consequences of shading on seedling drought resistance are unclear. Reintroduction of blight-resistant American chestnut (Castanea dentata (Marsh.) Borkh.) into eastern North American forests will often occur on water-limited sites and under partial canopy cover. We measured leaf pre-dawn water potential (Ψpd), leaf gas exchange, and growth and biomass allocation of backcross hybrid American chestnut seedlings from three orchard sources grown under different light intensities (76, 26 and 8% full photosynthetically active radiation (PAR)) and subjected to well-watered or mid-season water-stressed conditions. Seedlings in the water-stress treatment were returned to well-watered conditions after wilting to examine recovery. Seedlings growing under medium- and high-light conditions wilted at lower leaf Ψpd than low-light seedlings. Recovery of net photosynthesis (Anet) and stomatal conductance (gs) was greater in low and medium light than in high light. Seed source did not affect the response to water stress or light level in most cases. Between 26 and 8% full PAR, light became limiting to the extent that the effects of water stress had no impact on some growth and morphological traits. We conclude that positive and negative aspects of shading on seedling drought tolerance and recovery are not mutually exclusive. Partial shade may help American chestnut tolerate drought during early establishment through effects on physiological conditioning. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Nameda, N
1988-01-01
Illumination allows solid object perception to be obtained and depicted by a shading pattern produced by lighting. The shading cue, as one of solid perception cues (Gibson 1979), was investigated in regard to a white corrugated wave shape, using computer graphic device: Tospix-2. The reason the corrugated wave was chosen, is that an alternately bright and dark pattern, produced by shading, can be conveniently analyzed into contained spatial frequencies. This paper reports spatial frequency properties contained in the shading pattern. The shading patterns, input into the computer graphic device, are analyzed by Fourier Transformation by the same device. After the filtration by various spatial frequency low and high pass filters, Inverse Fourier Transformation is carried out for the residual components. The result of the analysis indicates that the third through higher harmonics components are important in regard to presenting a solid reality feeling in solid perception. Sakata (1983) also reported that an edged pattern, superimposed onto a lower sinusoidal pattern, was important in solid perception. The third through higher harmonics components express the changing position of luminance on the pattern, and a slanted plane relating to the light direction. Detection of a solid shape, constructed with flat planes, is assumed to be on the bottom of the perfect curved solid perception mechanism. Apparent evidence for this assumption, in difficult visual conditions, is that a flat paneled solid is seen before the curved solid. This mechanism is explained by two spatial frequency neural network systems, assumed as having correspondence with higher spatial frequency detection and lower spatial frequency detection.
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A novel method for detecting light source for digital images forensic
NASA Astrophysics Data System (ADS)
Roy, A. K.; Mitra, S. K.; Agrawal, R.
2011-06-01
Manipulation in image has been in practice since centuries. These manipulated images are intended to alter facts — facts of ethics, morality, politics, sex, celebrity or chaos. Image forensic science is used to detect these manipulations in a digital image. There are several standard ways to analyze an image for manipulation. Each one has some limitation. Also very rarely any method tried to capitalize on the way image was taken by the camera. We propose a new method that is based on light and its shade as light and shade are the fundamental input resources that may carry all the information of the image. The proposed method measures the direction of light source and uses the light based technique for identification of any intentional partial manipulation in the said digital image. The method is tested for known manipulated images to correctly identify the light sources. The light source of an image is measured in terms of angle. The experimental results show the robustness of the methodology.
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McMahon, Kathryn; Lavery, Paul S; Mulligan, Michael
2011-02-01
A large-scale, manipulative experiment was conducted to examine the extent and rate of recovery of meadows of the temperate Australian seagrass, Amphibolis griffithii to different light-reduction scenarios typical of dredging operations, and to identify potential indicators of recovery from light reduction stress. Shade cloth was used to mimic different intensities, durations and start times of light reduction, and then was removed to assess the recovery. The meadow could recover from 3 months of light stress (5-18% ambient) following 10 months re-exposure to ambient light, even when up to 72% of leaf biomass was lost, much faster recovery rates than has previously been observed for large seagrasses. However, when the meadow had been shaded for 6-9 months and more than 82% of leaf biomass was lost, no recovery was detected up to 23 months after the light stress had ceased, consistent with other studies. Five potential indicators of recovery were recommended. Copyright © 2010 Elsevier Ltd. All rights reserved.
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Growth distribution during phototropism of Arabidopsis thaliana seedlings
DOE Office of Scientific and Technical Information (OSTI.GOV)
Orbovic, V.; Poff, K.L.
1993-09-01
The elongation rates of two opposite sides of hypocotyls of Arabidopsis thaliana seedlings were measured during phototropism by using an infrared imaging system. In first positive phototropism, second positive phototropism, and red light-enhanced first positive phototropism, curvature toward the light source was the result of an increase in the rate of elongation of the shaded side and a decrease in the rate of elongation of the lighted side of the seedlings. The phase of straightening that followed maximum curvature resulted from a decrease in the elongation rate of the shaded side and an increase in the elongation rate of themore » lighted side. These data for the three types of blue light-induced phototropism tested in this study and for the phase of straightening are all clearly consistent with the growth rate changes predicted by the Cholodny-Went theory. 31 refs., 7 figs.« less
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Responses of four Indo-West Pacific seagrass species to shading.
Collier, Catherine J; Waycott, Michelle; Ospina, Ana Giraldo
2012-01-01
Seagrasses of the Great Barrier Reef predominantly occur in coastal regions where terrestrial inputs modify water quality and photosynthetic light is highly variable. Responses to shading were tested for Cymodocea serrulata, Halodule uninervis, Thalassia hemprichii and Zostera muelleri. In aquaria, four light treatments - high (66% surface light), moderate (31%), low (14%) and very low light (1%) treatments - were applied for 102d. Stress responses in the low and very low light treatments occurred in the following sequence: metabolic and physiological changes (reduced growth, increased pigment concentrations and photosynthetic efficiency); shedding (leaf loss, shoot loss) and production of new, altered tissue (leaves with reduced length, width and thickness). Complete shoot loss was projected after 76 (Z. muelleri) to 130d (T. hemprichii). Responses were slower in the low than in the very low treatment, therefore, efforts to minimize water quality degradation will be rewarded with delayed impacts to seagrasses. Copyright © 2011 Elsevier Ltd. All rights reserved.
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A Novel Two-Step Method for Screening Shade Tolerant Mutant Plants via Dwarfism
Li, Wei; Katin-Grazzini, Lorenzo; Krishnan, Sanalkumar; Thammina, Chandra; El-Tanbouly, Rania; Yer, Huseyin; Merewitz, Emily; Guillard, Karl; Inguagiato, John; McAvoy, Richard J.; Liu, Zongrang; Li, Yi
2016-01-01
When subjected to shade, plants undergo rapid shoot elongation, which often makes them more prone to disease and mechanical damage. Shade-tolerant plants can be difficult to breed; however, they offer a substantial benefit over other varieties in low-light areas. Although perennial ryegrass (Lolium perenne L.) is a popular species of turf grasses because of their good appearance and fast establishment, the plant normally does not perform well under shade conditions. It has been reported that, in turfgrass, induced dwarfism can enhance shade tolerance. Here we describe a two-step procedure for isolating shade tolerant mutants of perennial ryegrass by first screening for dominant dwarf mutants, and then screening dwarf plants for shade tolerance. The two-step screening process to isolate shade tolerant mutants can be done efficiently with limited space at early seedling stages, which enables quick and efficient isolation of shade tolerant mutants, and thus facilitates development of shade tolerant new cultivars of turfgrasses. Using the method, we isolated 136 dwarf mutants from 300,000 mutagenized seeds, with 65 being shade tolerant (0.022%). When screened directly for shade tolerance, we recovered only four mutants from a population of 150,000 (0.003%) mutagenized seeds. One shade tolerant mutant, shadow-1, was characterized in detail. In addition to dwarfism, shadow-1 and its sexual progeny displayed high degrees of tolerance to both natural and artificial shade. We showed that endogenous gibberellin (GA) content in shadow-1 was higher than wild-type controls, and shadow-1 was also partially GA insensitive. Our novel, simple and effective two-step screening method should be applicable to breeding shade tolerant cultivars of turfgrasses, ground covers, and other economically important crop plants that can be used under canopies of existing vegetation to increase productivity per unit area of land. PMID:27752260
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Robson, Frances; Okamoto, Haruko; Patrick, Elaine; Harris, Sue-Ré; Wasternack, Claus; Brearley, Charles; Turner, John G.
2010-01-01
Jasmonate (JA) activates plant defense, promotes pollen maturation, and suppresses plant growth. An emerging theme in JA biology is its involvement in light responses; here, we examine the interdependence of the JA- and light-signaling pathways in Arabidopsis thaliana. We demonstrate that mutants deficient in JA biosynthesis and signaling are deficient in a subset of high irradiance responses in far-red (FR) light. These mutants display exaggerated shade responses to low, but not high, R/FR ratio light, suggesting a role for JA in phytochrome A (phyA) signaling. Additionally, we demonstrate that the FR light–induced expression of transcription factor genes is dependent on CORONATINE INSENSITIVE1 (COI1), a central component of JA signaling, and is suppressed by JA. phyA mutants had reduced JA-regulated growth inhibition and VSP expression and increased content of cis-(+)-12-oxophytodienoic acid, an intermediate in JA biosynthesis. Significantly, COI1-mediated degradation of JASMONATE ZIM DOMAIN1-β-glucuronidase (JAZ1-GUS) in response to mechanical wounding and JA treatment required phyA, and ectopic expression of JAZ1-GUS resulted in exaggerated shade responses. Together, these results indicate that JA and phyA signaling are integrated through degradation of the JAZ1 protein, and both are required for plant responses to light and stress. PMID:20435902
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Assessing solar energy and water use efficiencies in winter wheat
NASA Technical Reports Server (NTRS)
Asrar, G.; Hipps, L. E.; Kanemasu, E. T.
1982-01-01
The water use and solar energy conversion efficiencies of two cultivars of winter wheat (Triticum aestivum L., vars, Centurk and Newton) planted at three densities, were examined during a growing season. Water use, based on soil moisture depletion, was the lowest under the light, and the highest under the heavy planting densities of both cultivars. Water use efficiency of medium and heavy planting densities were greater than the light planting densities in both cultivars. The canopy radiation extinction coefficients of both cultivars increased with increases in planting density. Efficiency of operation interception of photosynthetically active radiation by both cultivars improved from the time of jointing until anthesis, and then decreased during senescence. The efficiency of the conversion of intercepted radiation to dry matter (biochemical efficiency) decreased throughout the growing season both cultivars. The interception, biochemical, and photosynthetic efficiencies improved as planting density increased.
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Varga, Sandra; Laaksonen, Ester; Siikamäki, Pirkko; Kytöviita, Minna-Maarit
2015-01-01
Sex-differential plasticity (SDP) hypothesis suggests that since hermaphrodites gain fitness through both pollen and seed production they may have evolved a higher degree of plasticity in their reproductive strategy compared to females which achieve fitness only through seed production. SDP may explain the difference in seed production observed between sexes in gynodioecious species in response to resource (nutrients or water) availability. In harsh environments, hermaphrodites decrease seed production whereas females keep it relatively similar regardless of the environmental conditions. Light availability can be also a limiting resource and thus could theoretically affect differently female and hermaphrodite seed output even though this ecological factor has been largely overlooked. We tested whether the two sexes in the gynodioecious species Geranium sylvaticum differ in their tolerance to light limitation during seed maturation in the field. We used a fully factorial block experiment exposing female and hermaphrodite plants to two different light environments (control and shade) after their peak flowering period. Specifically, we measured fruit and seed production in response to decreased light availability and compared it between the sexes. Shading reduced the number of fruits and seeds produced, but the decrease was similar between the sexes. Furthermore, shading delayed seed production by three days in both sexes, but did not affect seed mass, seed P content, or the probability of re-flowering the following year. Our results give no evidence for reproductive SDP in response to light during seed maturation.
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Seedling growth strategies in Bauhinia species: comparing lianas and trees.
Cai, Zhi-Quan; Poorter, Lourens; Cao, Kun-Fang; Bongers, Frans
2007-10-01
Lianas are expected to differ from trees in their growth strategies. As a result these two groups of woody species will have different spatial distributions: lianas are more common in high light environments. This study determines the differences in growth patterns, biomass allocation and leaf traits in five closely related liana and tree species of the genus Bauhinia. Seedlings of two light-demanding lianas (Bauhinia tenuiflora and B. claviflora), one shade-tolerant liana (B. aurea), and two light-demanding trees (B. purpurea and B. monandra) were grown in a shadehouse at 25% of full sunlight. A range of physiological, morphological and biomass parameters at the leaf and whole plant level were compared among these five species. The two light-demanding liana species had higher relative growth rate (RGR), allocated more biomass to leaf production [higher leaf mass fraction (LMF) and higher leaf area ratio (LAR)] and stem mass fraction (SMF), and less biomass to the roots [root mass fraction (RMF)] than the two tree species. The shade-tolerant liana had the lowest RGR of all five species, and had a higher RMF, lower SMF and similar LMF than the two light-demanding liana species. The two light-demanding lianas had lower photosynthetic rates per unit area (A(area)) and similar photosynthetic rates per unit mass (A(mass)) than the trees. Across species, RGR was positively related to SLA, but not to LAR and A(area). It is concluded that the faster growth of light-demanding lianas compared with light-demanding trees is based on morphological parameters (SLA, LMF and LAR), and cannot be attributed to higher photosynthetic rates at the leaf level. The shade-tolerant liana exhibited a slow-growth strategy, compared with the light-demanding species.
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Seedling Growth Strategies in Bauhinia Species: Comparing Lianas and Trees
Cai, Zhi-Quan; Poorter, Lourens; Cao, Kun-Fang; Bongers, Frans
2007-01-01
Background and Aims Lianas are expected to differ from trees in their growth strategies. As a result these two groups of woody species will have different spatial distributions: lianas are more common in high light environments. This study determines the differences in growth patterns, biomass allocation and leaf traits in five closely related liana and tree species of the genus Bauhinia. Methods Seedlings of two light-demanding lianas (Bauhinia tenuiflora and B. claviflora), one shade-tolerant liana (B. aurea), and two light-demanding trees (B. purpurea and B. monandra) were grown in a shadehouse at 25 % of full sunlight. A range of physiological, morphological and biomass parameters at the leaf and whole plant level were compared among these five species. Key Results The two light-demanding liana species had higher relative growth rate (RGR), allocated more biomass to leaf production [higher leaf mass fraction (LMF) and higher leaf area ratio (LAR)] and stem mass fraction (SMF), and less biomass to the roots [root mass fraction (RMF)] than the two tree species. The shade-tolerant liana had the lowest RGR of all five species, and had a higher RMF, lower SMF and similar LMF than the two light-demanding liana species. The two light-demanding lianas had lower photosynthetic rates per unit area (Aarea) and similar photosynthetic rates per unit mass (Amass) than the trees. Across species, RGR was positively related to SLA, but not to LAR and Aarea. Conclusions It is concluded that the faster growth of light-demanding lianas compared with light-demanding trees is based on morphological parameters (SLA, LMF and LAR), and cannot be attributed to higher photosynthetic rates at the leaf level. The shade-tolerant liana exhibited a slow-growth strategy, compared with the light-demanding species. PMID:17720978
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Quality and Quantity Evaluations of Shade Grown Forages
K. P. Ladyman; M. S. Kerley; R. L. Kallenbach; H. E. Garrett; J. W. Van Sambeek; N. E. Navarrete-Tindall
2003-01-01
Seven legumes were grown during the summer-fall of 2000, at the Horticulture and Agroforestry Research Center (39? 01 ' N, 92? 46' W) near New Franklin, MO. The forages were grown in 7.5L white pots placed on light-colored gravel either under full sunlight, 45% sunlight, or 20% sunlight created by a shade cloth over a rectangular frame. Drip irrigation was...
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Correlations between tree crown condition and shade tolerance, crown form, and light availability
KaDonna C. Randolph
2007-01-01
Individual tree crown condition is the result of a combination of many factors including genetic traits, growing site characteristics, and past and present external stresses (e.g., drought, insect outbreaks, fire, etc.). Shade tolerance and the extent to which terminal buds control the length and orientation of lateral branches (epinastic control) are the two primary...
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The Beauty of the Beasts in Chalk Pastels
ERIC Educational Resources Information Center
Skophammer, Karen
2010-01-01
In this article, the author describes how her seventh-grade art students captured an image of a stuffed animal in the "whole-to-part" drawing technique using chalk pastels. Shading with chalk pastels can give a gradual change in value from dark to light. The shading and color changes the mood of the original drawing, and adds texture, too. Chalk…
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Response of an algal assemblage to nutrient enrichment and shading in a Hawaiian stream
Stephens, S.H.; Brasher, A.M.D.; Smith, C.M.
2012-01-01
To investigate the effects of nitrate enrichment, phosphate enrichment, and light availability on benthic algae, nutrient-diffusing clay flowerpots were colonized with algae at two sites in a Hawaiian stream during spring and autumn 2002 using a randomized factorial design. The algal assemblage that developed under the experimental conditions was investigated by determining biomass (ash-free dry mass and chlorophyll a concentrations) and composition of the diatom assemblage. In situ pulse amplitude-modulated fluorometry was also used to model photosynthetic rate of the algal assemblage. Algal biomass and maximum photosynthetic rate were significantly higher at the unshaded site than at the shaded site. These parameters were higher at the unshaded site with either nitrate, or to a lesser degree, nitrate plus phosphate enrichment. Analysis of similarity of diatom assemblages showed significant differences between shaded and unshaded sites, as well as between spring and autumn experiments, but not between nutrient treatments. However, several individual species of diatoms responded significantly to nitrate enrichment. These results demonstrate that light availability (shaded vs. unshaded) is the primary limiting factor to algal growth in this stream, with nitrogen as a secondary limiting factor. ?? 2011 Springer Science+Business Media B.V.
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McGoey, Brechann V; Stinchcombe, John R
2009-08-01
Shade avoidance syndrome is a known adaptive response for Impatiens capensis growing in dense intraspecific competition. However, I. capensis also grow with dominant interspecific competitors in marshes. Here, we compare the I. capensis shade-avoidance phenotypes produced in the absence and presence of heterospecific competitors, as well as selection on those traits. Two treatments were established in a marsh; in one treatment all heterospecifics were removed, while in the other, all competitors remained. We compared morphological traits, light parameters, seed output and, using phenotypic selection analysis, examined directional and nonlinear selection operating in the different competitive treatments. Average phenotypes, light parameters and seed production all varied depending on competitive treatment. Phenotypic selection analyses revealed different directional, disruptive, stabilizing and correlational selection. The disparities seen in both phenotypes and selection between the treatments related to the important differences in elongation timing depending on the presence of heterospecifics, although environmental covariances between traits and fitness could also contribute. Phenotypes produced by I. capensis depend on their competitive environment, and differing selection on shade-avoidance traits between competitive environments could indirectly select for increased plasticity given gene flow between populations in different competitive contexts.
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Re, Giovanni Antonio; Piluzza, Giovanna; Sanna, Federico; Molinu, Maria Giovanna; Sulas, Leonardo
2018-06-01
In Mediterranean grazed woodlands, microclimate changes induced by trees influence the growth and development of the understory, but very little is known about its polyphenolic composition in relation to light intensity. We investigated the bioactive compounds and antioxidant capacity of different legume-based swards and variations due to full sunlight and partial shade. The research was carried out in a cork oak agrosilvopastoral system in Sardinia. The highest values of DPPH reached 7 mmol TEAC 100 g -1 DW, total phenolics 67.1 g GAE kg -1 DW and total flavonoids 7.5 g CE kg -1 DW. Compared to full sunlight, partial shade reduced DPPH values by 29 and 42%, and the total phenolic content by 23 and 53% in 100% legume mixture and semi natural pasture. Twelve phenolic compounds were detected: chlorogenic acid in 80% legume mixture (partial shade) and verbascoside in pure sward of bladder clover (full sunlight) were the most abundant. Light intensity significantly affected antioxidant capacity, composition and levels of phenolic compounds. Our results provide new insights into the effects of light intensity on plant secondary metabolites from legume based swards, underlining the important functions provided by agroforestry systems. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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Tattini, Massimiliano; Landi, Marco; Brunetti, Cecilia; Giordano, Cristiana; Remorini, Damiano; Gould, Kevin S; Guidi, Lucia
2014-11-01
The putative photoprotective role of foliar anthocyanins continues to attract heated debate. Strikingly different experimental set-ups coupled with a poor knowledge of anthocyanin identity have likely contributed to such disparate opinions. Here, the photosynthetic responses to 30 or 100% solar irradiance were compared in two cultivars of basil, the green-leafed Tigullio (TG) and the purple-leafed Red Rubin (RR). Coumaroyl anthocyanins in RR leaf epidermis significantly mitigated the effects of high light stress. In full sunlight, RR leaves displayed several shade-plant traits; they transferred less energy than did TG to photosystem II (PSII), and non-photochemical quenching was lower. The higher xanthophyll cycle activity in TG was insufficient to prevent inactivation of PSII in full sunlight. However, TG was the more efficient in the shade; RR was far less able to accommodate a large change in irradiance. Investment of carbon to phenylpropanoid biosynthesis was more in RR than in TG in the shade, and was either greatly enhanced in TG or varied little in RR because of high sunlight. The metabolic cost of photoprotection was lower whereas light-induced increase in biomass production was higher in RR than in TG, thus making purple basil the more light tolerant. Purple basil appears indeed to display the conservative resource-use strategy usually observed in highly stress tolerant species. We conclude that the presence of epidermal coumaroyl anthocyanins confers protective benefits under high light, but it is associated with a reduced plasticity to accommodate changing light fluxes as compared with green leaves. © 2014 Scandinavian Plant Physiology Society.
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A statistical light use efficiency model explains 85% variations in global GPP
NASA Astrophysics Data System (ADS)
Jiang, C.; Ryu, Y.
2016-12-01
Photosynthesis is a complicated process whose modeling requires different levels of assumptions, simplification, and parameterization. Among models, light use efficiency (LUE) model is highly compact but powerful in monitoring gross primary production (GPP) from satellite data. Most of LUE models adopt a multiplicative from of maximum LUE, absorbed photosynthetically active radiation (APAR), and temperature and water stress functions. However, maximum LUE is a fitting parameter with large spatial variations, but most studies only use several biome dependent constants. In addition, stress functions are empirical and arbitrary in literatures. Moreover, meteorological data used are usually coarse-resolution, e.g., 1°, which could cause large errors. Finally, sunlit and shade canopy have completely different light responses but little considered. Targeting these issues, we derived a new statistical LUE model from a process-based and satellite-driven model, the Breathing Earth System Simulator (BESS). We have already derived a set of global radiation (5-km resolution), carbon and water fluxes (1-km resolution) products from 2000 to 2015 from BESS. By exploring these datasets, we found strong correlation between APAR and GPP for sunlit (R2=0.84) and shade (R2=0.96) canopy, respectively. A simple model, only driven by sunlit and shade APAR, was thus built based on linear relationships. The slopes of the linear function act as effective LUE of global ecosystem, with values of 0.0232 and 0.0128 umol C/umol quanta for sunlit and shade canopy, respectively. When compared with MPI-BGC GPP products, a global proxy of FLUXNET data, BESS-LUE achieved an overall accuracy of R2 = 0.85, whereas original BESS was R2 = 0.83 and MODIS GPP product was R2 = 0.76. We investigated spatiotemporal variations of the effective LUE. Spatially, the ratio of sunlit to shade values ranged from 0.1 (wet tropic) to 4.5 (dry inland). By using maps of sunlit and shade effective LUE the accuracy of BESS-LUE further reached R2 = 0.88. Temporally, both sunlit and shade effective LUE had seasonal peak values in NH summer, and both showed significant increasing trends. Overall, BESS-LUE exhibited promising potential in global GPP mapping. We are going to evaluate it using FLUXNET2015 database and satellite solar Induced Fluorescence (SIF) data.
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Microplate-based method for high-throughput screening of microalgae growth potential.
Van Wagenen, Jon; Holdt, Susan Løvstad; De Francisci, Davide; Valverde-Pérez, Borja; Plósz, Benedek Gy; Angelidaki, Irini
2014-10-01
Microalgae cultivation conditions in microplates will differ from large-scale photobioreactors in crucial parameters such as light profile, mixing and gas transfer. Hence volumetric productivity (P(v)) measurements made in microplates cannot be directly scaled up. Here we demonstrate that it is possible to use microplates to measure characteristic exponential growth rates and determine the specific growth rate light intensity dependency (μ-I curve), which is useful as the key input for several models that predict P(v). Nannochloropsis salina and Chlorella sorokiniana specific growth rates were measured by repeated batch culture in microplates supplied with continuous light at different intensities. Exponential growth unlimited by gas transfer or self-shading was observable for a period of several days using fluorescence, which is an order of magnitude more sensitive than optical density. The microplate datasets were comparable to similar datasets obtained in photobioreactors and were used an input for the Huesemann model to accurately predict P(v). Copyright © 2014 Elsevier Ltd. All rights reserved.
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Does greater specific leaf area plasticity help plants to maintain a high performance when shaded?
Liu, Yanjie; Dawson, Wayne; Prati, Daniel; Haeuser, Emily; Feng, Yanhao; van Kleunen, Mark
2016-12-01
It is frequently assumed that phenotypic plasticity can be very advantageous for plants, because it may increase environmental tolerance (fitness homeostasis). This should, however, only hold for plastic responses that are adaptive, i.e. increase fitness. Numerous studies have shown shade-induced increases in specific leaf area (SLA), and there is wide consensus that this plastic response optimizes light capture and thus has to be adaptive. However, it has rarely been tested whether this is really the case. In order to identify whether SLA plasticity does contribute to the maintenance of high biomass of plant species under shaded conditions, a meta-analytical approach was employed. The data set included 280 species and 467 individual studies from 32 publications and two unpublished experiments. Plants increased their SLA by 55·4 % on average when shaded, while they decreased their biomass by 59·9 %. Species with a high SLA under high-light control conditions showed a significantly greater ability to maintain biomass production under shade overall. However, in contrast to the expectation of a positive relationship between SLA plasticity and maintenance of plant biomass, the results indicated that species with greater SLA plasticity were less able to maintain biomass under shade. Although a high SLA per se contributes to biomass homeostasis, there was no evidence that plasticity in SLA contributes to this. Therefore, it is argued that some of the plastic changes that are frequently thought to be adaptive might simply reflect passive responses to the environment, or result as by-products of adaptive plastic responses in other traits. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Konvalinková, Tereza; Püschel, David; Janoušková, Martina; Gryndler, Milan; Jansa, Jan
2015-01-01
Plant and fungal partners in arbuscular mycorrhizal symbiosis trade mineral nutrients for carbon, with the outcome of this relationship for plant growth and nutrition being highly context-dependent and changing with the availability of resources as well as with the specific requirements of the different partners. Here we studied how the model legume Medicago truncatula, inoculated or not with a mycorrhizal fungus Rhizophagus irregularis, responded to a gradient of light intensities applied over different periods of time, in terms of growth, phosphorus nutrition and the levels of root colonization by the mycorrhizal fungus. Short-term (6 d) shading, depending on its intensity, resulted in a rapid decline of phosphorus uptake to the shoots of mycorrhizal plants and simultaneous accumulation of phosphorus in the roots (most likely in the fungal tissues), as compared to the non-mycorrhizal controls. There was, however, no significant change in the levels of mycorrhizal colonization of roots due to short-term shading. Long-term (38 d) shading, depending on its intensity, provoked a multitude of plant compensatory mechanisms, which were further boosted by the mycorrhizal symbiosis. Mycorrhizal growth- and phosphorus uptake benefits, however, vanished at 10% of the full light intensity applied over a long-term. Levels of root colonization by the mycorrhizal fungus were significantly reduced by long-term shading. Our results indicate that even short periods of shade could have important consequences for the functioning of mycorrhizal symbiosis in terms of phosphorus transfer between the fungus and the plants, without any apparent changes in root colonization parameters or mycorrhizal growth response, and call for more focused research on temporal dynamics of mycorrhizal functioning under changing environmental conditions. PMID:25763002
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Kodama, Nao; Setoi, Ayana; Kose, Katsumi
2018-01-01
Spiral MRI sequences were developed for a 9.4T vertical standard bore (54 mm) superconducting magnet using unshielded and self-shielded gradient coils. Clear spiral images with 64-shot scan were obtained with the self-shielded gradient coil, but severe shading artifacts were observed for the spiral-scan images acquired with the unshielded gradient coil. This shading artifact was successfully corrected with a phase-correction technique using reference scans that we developed based on eddy current field measurements. We therefore concluded that spiral imaging sequences can be installed even for unshielded gradient coils if phase corrections are performed using the reference scans. PMID:28367906
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Kodama, Nao; Setoi, Ayana; Kose, Katsumi
2018-04-10
Spiral MRI sequences were developed for a 9.4T vertical standard bore (54 mm) superconducting magnet using unshielded and self-shielded gradient coils. Clear spiral images with 64-shot scan were obtained with the self-shielded gradient coil, but severe shading artifacts were observed for the spiral-scan images acquired with the unshielded gradient coil. This shading artifact was successfully corrected with a phase-correction technique using reference scans that we developed based on eddy current field measurements. We therefore concluded that spiral imaging sequences can be installed even for unshielded gradient coils if phase corrections are performed using the reference scans.
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Basch, Corey H; Hillyer, Grace Clarke; Ethan, Danna; Berdnik, Alyssa; Basch, Charles E
2015-07-01
Tanned skin has been associated with perceptions of fitness and social desirability. Portrayal of models in magazines may reflect and perpetuate these perceptions. Limited research has investigated tanning shade gradations of models in men's versus women's fitness and muscle enthusiast magazines. Such findings are relevant in light of increased incidence and prevalence of melanoma in the United States. This study evaluated and compared tanning shade gradations of adult Caucasian male and female model images in mainstream fitness and muscle enthusiast magazines. Sixty-nine U.S. magazine issues (spring and summer, 2013) were utilized. Two independent reviewers rated tanning shade gradations of adult Caucasian male and female model images on magazines' covers, advertisements, and feature articles. Shade gradations were assessed using stock photographs of Caucasian models with varying levels of tanned skin on an 8-shade scale. A total of 4,683 images were evaluated. Darkest tanning shades were found among males in muscle enthusiast magazines and lightest among females in women's mainstream fitness magazines. By gender, male model images were 54% more likely to portray a darker tanning shade. In this study, images in men's (vs. women's) fitness and muscle enthusiast magazines portrayed Caucasian models with darker skin shades. Despite these magazines' fitness-related messages, pro-tanning images may promote attitudes and behaviors associated with higher skin cancer risk. To date, this is the first study to explore tanning shades in men's magazines of these genres. Further research is necessary to identify effects of exposure to these images among male readers. © The Author(s) 2014.
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Shi, Yu; Chen, Mao-xue; Yu, Zhen-wen; Xu, Zhen-zhu
2011-10-01
Taking three wheat cultivars Jimai 20 (strong gluten), Taishan 23 (medium gluten), and Ningmai 9 (weak gluten) as test materials, a field experiment was conducted to examine the effects of shading at different phases of grain-filling on the grain protein components contents and processing quality. Four treatments were installed, i. e., no shading (S0), shading at early grain-filling phase (from 0 day after anthesis (DAA) to 11 DAA; S1), shading at medium grain-filling phase (from 12 DAA to 23 DAA; S2), and shading at late grain-filling phase (from 24 DAA to 35 DAA; S3). No significant differences were observed in the grain albumin+globulin contents of the three cultivars among the four treatments. Shading increased the grain HMW-GS, LMW-GS, gluten, glutenin, and total protein contents of Jimai 20 and Taishan 23 significantly, and the increments were higher in treatment S2 than in other shading treatments. Treatments S2 and S3 increased the grain protein components contents of Ningmai 9 significantly. Comparing with the control, shading decreased the grain yield significantly, but increased the dough development time, dough stability time, and sedimentation volume, especially for treatment S2, which suggested that the wheat grain quality had a close relationship with the light intensity at medium phase of grain-filling. Overall, the regulation effect of shading at grain-filling stage on the wheat grain yield, grain protein components contents, and indices values of grain processing quality for the test cultivars was in the order of Jimai 20 > Taishan 23 > Ningmai 9.
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Filiault, Daniele L.; Kumar, Ravi; Jiménez-Gómez, José M.; Schrager, Amanda V.; Park, Daniel S.; Peng, Jie; Sinha, Neelima R.; Maloof, Julin N.
2012-01-01
The laminae of leaves optimize photosynthetic rates by serving as a platform for both light capture and gas exchange, while minimizing water losses associated with thermoregulation and transpiration. Many have speculated that plants maximize photosynthetic output and minimize associated costs through leaf size, complexity, and shape, but a unifying theory linking the plethora of observed leaf forms with the environment remains elusive. Additionally, the leaf itself is a plastic structure, responsive to its surroundings, further complicating the relationship. Despite extensive knowledge of the genetic mechanisms underlying angiosperm leaf development, little is known about how phenotypic plasticity and selective pressures converge to create the diversity of leaf shapes and sizes across lineages. Here, we use wild tomato accessions, collected from locales with diverse levels of foliar shade, temperature, and precipitation, as a model to assay the extent of shade avoidance in leaf traits and the degree to which these leaf traits correlate with environmental factors. We find that leaf size is correlated with measures of foliar shade across the wild tomato species sampled and that leaf size and serration correlate in a species-dependent fashion with temperature and precipitation. We use far-red induced changes in leaf length as a proxy measure of the shade avoidance response, and find that shade avoidance in leaves negatively correlates with the level of foliar shade recorded at the point of origin of an accession. The direction and magnitude of these correlations varies across the leaf series, suggesting that heterochronic and/or ontogenic programs are a mechanism by which selective pressures can alter leaf size and form. This study highlights the value of wild tomato accessions for studies of both morphological and light-regulated development of compound leaves, and promises to be useful in the future identification of genes regulating potentially adaptive plastic leaf traits. PMID:22253737
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Shade matching assisted by digital photography and computer software.
Schropp, Lars
2009-04-01
To evaluate the efficacy of digital photographs and graphic computer software for color matching compared to conventional visual matching. The shade of a tab from a shade guide (Vita 3D-Master Guide) placed in a phantom head was matched to a second guide of the same type by nine observers. This was done for twelve selected shade tabs (tests). The shade-matching procedure was performed visually in a simulated clinic environment and with digital photographs, and the time spent for both procedures was recorded. An alternative arrangement of the shade tabs was used in the digital photographs. In addition, a graphic software program was used for color analysis. Hue, chroma, and lightness values of the test tab and all tabs of the second guide were derived from the digital photographs. According to the CIE L*C*h* color system, the color differences between the test tab and tabs of the second guide were calculated. The shade guide tab that deviated least from the test tab was determined to be the match. Shade matching performance by means of graphic software was compared with the two visual methods and tested by Chi-square tests (alpha= 0.05). Eight of twelve test tabs (67%) were matched correctly by the computer software method. This was significantly better (p < 0.02) than the performance of the visual shade matching methods conducted in the simulated clinic (32% correct match) and with photographs (28% correct match). No correlation between time consumption for the visual shade matching methods and frequency of correct match was observed. Shade matching assisted by digital photographs and computer software was significantly more reliable than by conventional visual methods.
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NASA Astrophysics Data System (ADS)
Eldridge, David J.
1999-05-01
The distribution and abundance of soil crust lichens and bryophytes was examined in a patterned Callitris glaucophylla woodland in eastern Australia. Twenty-one lichen species and 26 bryophyte species were collected within thirty quadrats along a sequence of runoff, interception and runoff zones. Crust cover was significantly greatest in the interception zones (79.0 %), followed by the runoff zones (24.0 %), and lowest in the groved, runon zones (6.6 %). Lichens and bryophytes were distributed across all geomorphic zones, and, although there were significantly more moss species in the interception zones (mean = 9.1) compared with either the runoff (4.2) or runon (3.2) zones, the number of lichen species did not vary between zones. Ordination of a reduced data set of 32 species revealed a separation of taxa into distinct groups corresponding to the three geomorphic zones. Canonical correspondence analysis (CCA) of the 32 species and thirteen environmental variables revealed that the most important factors associated with the distribution of species were sheet and scarp erosion, soil stability and coherence, litter cover and crust cover. Surface cracking, microtopography and plant cover were of intermediate importance. The CCA biplot revealed that the timbered runon zones (groves) were dominated by `shade-tolerant' mosses Fissidens vittatus and Barbula hornschuchiana, whilst the heavily eroded runoff zones supported sparse populations of `erosion tolerant' lichens ( Endocarpon rogersii) and mosses (Bryum argenteum and Didymodon torquatus). Interception zones supported a rich suite of `crust forming' mosses and lichens capable of tolerating moderate inundation by overland flow. Two other groups of taxa were identified by this analysis: the `pioneer' group, comprising mainly nitrogen-fixing lichens which occupy the zone of active erosion at the lower edge of the groves, and the `opportunists' dominated by liverworts, occupying the shallow depressions or bays at the margins of the groves and the interception zones. This study confirms that the non-vascular lichens and bryophytes in these arid soil crusts, are, like the vascular plants, strongly patterned according to geomorphic zone, being most strongly associated with soil surface and erosional features.
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Mosses and the struggle for light in a nitrogen-polluted world.
van der Wal, René; Pearce, Imogen S K; Brooker, Rob W
2005-01-01
The impact of reduced light conditions as an indirect effect of nitrogen (N) deposition was determined on three mosses in a montane ecosystem, where sedge and grass cover increase due to N enrichment. Additionally, in the greenhouse we established the importance of low light to moss growth as an indirect N deposition effect relative to the direct toxic effects of N. The amount of light reaching the moss layer was strongly and negatively related to graminoid abundance. Mosses showed differing sensitivities to reduced light in the field. Racomitrium lanuginosum biomass was found to be highest under high-light conditions, Polytrichum alpinum at intermediate light levels, whilst that of Dicranum fuscescens was unrelated to light availability. Moreover, Racomitrium biomass decreased with increasing amounts of graminoid litter, whereas the other species were little affected. All three mosses responded differently to the combination of elevated N (20 vs 10 kg N ha(-1) year(-1)) and reduced light (60 and 80% reduction) in the greenhouse. Racomitrium growth was strongly influenced by both light reduction and elevated N, in combination reducing shoot biomass up to 76%. There was a tendency for Dicranum growth to be modestly reduced by elevated N when shaded, causing up to 19% growth reduction. Polytrichum growth was not influenced by elevated N but was reduced up to 40% by shading. We conclude that competition for light, induced by vascular plants, can strongly influence moss performance even in unproductive low biomass ecosystems. The effects of reduced light arising from N pollution can be as important to mosses as direct toxicity from N deposition. Yet, different sensitivities of mosses to both toxic and shading effects of elevated N prevent generalisation and can lead to competitive species replacement within moss communities. This study demonstrates the importance of understanding moss-vascular plant interactions to allow interpretation and prediction of ecosystem responses to anthropogenic drivers such as atmospheric N deposition or climate change.
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Manga Vectorization and Manipulation with Procedural Simple Screentone.
Yao, Chih-Yuan; Hung, Shih-Hsuan; Li, Guo-Wei; Chen, I-Yu; Adhitya, Reza; Lai, Yu-Chi
2017-02-01
Manga are a popular artistic form around the world, and artists use simple line drawing and screentone to create all kinds of interesting productions. Vectorization is helpful to digitally reproduce these elements for proper content and intention delivery on electronic devices. Therefore, this study aims at transforming scanned Manga to a vector representation for interactive manipulation and real-time rendering with arbitrary resolution. Our system first decomposes the patch into rough Manga elements including possible borders and shading regions using adaptive binarization and screentone detector. We classify detected screentone into simple and complex patterns: our system extracts simple screentone properties for refining screentone borders, estimating lighting, compensating missing strokes inside screentone regions, and later resolution independently rendering with our procedural shaders. Our system treats the others as complex screentone areas and vectorizes them with our proposed line tracer which aims at locating boundaries of all shading regions and polishing all shading borders with the curve-based Gaussian refiner. A user can lay down simple scribbles to cluster Manga elements intuitively for the formation of semantic components, and our system vectorizes these components into shading meshes along with embedded Bézier curves as a unified foundation for consistent manipulation including pattern manipulation, deformation, and lighting addition. Our system can real-time and resolution independently render the shading regions with our procedural shaders and drawing borders with the curve-based shader. For Manga manipulation, the proposed vector representation can be not only magnified without artifacts but also deformed easily to generate interesting results.
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Shifting roles of heterotrophy and autotrophy in coral energetics under varying turbidity.
Anthony; Fabricius
2000-09-20
Suspended particulate matter (SPM) strongly alters the trophic environment of photosymbiotic aquatic organisms. At high particles loads, phototrophic energy gains can be diminished due to light absorption by suspended particles, and stress from particle abrasion or deposition on tissues. However, energy gains are enhanced if organisms are able to use SPM as a food source. For photosymbiotic benthic suspension feeders, increases in SPM concentrations may require both phototrophic and heterotrophic acclimation to sustain a positive energy balance. This study provides an experimental analysis of the effects of contrasting light and SPM regimes on the energy budget (scope for growth) of two zooxanthellate corals (Goniastrea retiformis and Porites cylindrica). Using a factorial design in a flow-through tank system, corals were exposed for 2 months to shaded and unshaded conditions (equivalent to 3-4 m depth at 4 and 16 mg dry weight SPM l(-1), respectively) and a range of controlled SPM loads with a natural organic content ( approximately 3% w/w). In G. retiformis, rates of particle ingestion were a linear function of SPM concentration within a broad range (1-30 mg dry weight l(-1)). After 2 months of shading, photosynthetic acclimation was significant in G. retiformis, but did not compensate for the reduced light level, as daily respiration exceeded daily photosynthesis. However, in response to the prolonged shading, G. retiformis more than doubled its rate of particle feeding. At high SPM treatments (16 mg dw l(-1)), sediment feeding by this species compensated fully for the 35-47% lower phototrophy in the shaded treatment. Due to both photo- and heterotrophic plasticity, G. retiformis gained tissue and skeletal mass at all experimental levels of light and SPM. In contrast, rates of particle intake by P. cylindrica contributed <10% to the energy budget in shaded and <3% in unshaded conditions. Feeding rates of P. cylindrica were half-saturated at approximately 3 mg dry weight l(-1), and four- to eight-fold lower than those of G. retiformis. Skeletal growth was sustained, but tissue mass and lipid contents declined in shaded and high-SPM treatments, and carbon loss due to shading by SPM was not compensated for by particle feeding. Thus, due to a lack of photo- and heterotrophic plasticity, periods of high turbidity resulted in energy deficiency in P. cylindrica, and high turbidity conditions appeared physiologically unsustainable for this species. This study is the first to show heterotrophic plasticity in a symbiotic coral, and to show that such plasticity can offset stress from high particle loads. It demonstrates that changes in the trophic mode of some coral species are a mechanism for sustaining a positive energy balance in turbid environments, thereby broadening their physiological niche.
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Photosynthesis in chlorolichens: the influence of the habitat light regime.
Piccotto, Massimo; Tretiach, Mauro
2010-11-01
The hypothesis that CO(2) gas exchange and chlorophyll a fluorescence (ChlaF) of lichens vary according to the light regimes of their original habitat, as observed in vascular plants, was tested by analysing the photosynthetic performance of 12 populations of seven dorsoventral, foliose lichens collected from open, south-exposed rocks to densely shaded forests. Light response curves were induced at optimum thallus water content and ChlaF emission curves at the species-specific photon flux at which the quantum yield of CO(2) assimilation is the highest and is saturating the photosynthetic process. Photosynthetic pigments were quantified in crude extracts. The results confirm that the maximum rate of gross photosynthesis is correlated with the chlorophyll content of lichens, which is influenced by light as well as by nitrogen availability. Like leaves, shade tolerant lichens emit more ChlaF than sun-loving ones, whereas the photosynthetic quantum conversion is higher in the latter.
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Al-Nsour, Hind Fahed; Al-Zoubi, Tamara Trad; Al-Rimawi, Ali Salaheddin
2018-03-01
Facial and dental aesthetics are becoming of great concern for patients, especially for the younger generation. Tooth color matching and selection is considered a vital element in order to create an attractive beautiful smile. The importance of tooth color matching is to adjust tooth colors to obtain a good match with adjacent teeth and the skin. This is considered a challenge especially if adjacent teeth were lost or records of patients' teeth color were not available. The aim of this study was to determine the relationship between skin complexion and tooth value in a Jordanian population. A cross-sectional study of 520 individuals who were randomly selected and belonging to different age groups, ranging from 15-65 years, with equal sex distribution. These patients visited the dental clinics at different Jordanian military hospitals. The study was carried out over a period of one year from 2015 to 2016. The randomly selected sample was examined by one researcher. Shade of the middle third of the labial surface of central incisor was determined visually using VITA tooth guide, 3D-MASTER shade guide. Tooth shades were divided into two categories according to their value. The skin complexion was identified using Fitzpatrick skin type test, and was categorized into two categories (fair and dark). Data were statistically analyzed using Epi Info version 6. A statistically significant tooth shade value difference was discovered among subjects of different skin color (p<0.0001). Individuals with dark skin tend to have lighter teeth, while individuals with light skin tend to have darker teeth. Out of the 304 participants that were with dark complexion 274 (90%) have light teeth, and only 30 (10%) were with dark teeth. Out of the 216 participants with light complexion 172 (80%) have dark teeth and only 44 (20%) have light teeth. Within the limitation of this study, there was an inverse relation between skin complexion and tooth value among a Jordanian population. Thus, considering the skin complexion when choosing tooth shades is helpful in achieving a pleasing good-looking smile, yet further investigations in this field must be carried out.
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Minimising losses to predation during microalgae cultivation.
Flynn, Kevin J; Kenny, Philip; Mitra, Aditee
2017-01-01
We explore approaches to minimise impacts of zooplanktonic pests upon commercial microalgal crops using system dynamics models to describe algal growth controlled by light and nutrient availability and zooplankton growth controlled by crop abundance and nutritional quality. Losses of microalgal crops are minimised when their growth is fastest and, in contrast, also when growing slowly under conditions of nutrient exhaustion. In many culture systems, however, dwindling light availability due to self-shading in dense suspensions favours slow growth under nutrient sufficiency. Such a situation improves microalgal quality as prey, enhancing zooplankton growth, and leads to rapid crop collapse. Timing of pest entry is important; crop losses are least likely in established, nutrient-exhausted microalgal communities grown for high C-content (e.g. for biofuels). A potentially useful approach is to promote a low level of P-stress that does not adversely affect microalgal growth but which produces a crop that is suboptimal for zooplankton growth.
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Northern Red Oak Seedling Growth Varies by Light Intensity and Seed Source
Charles E. McGee
1968-01-01
Northern red oak seedlings from each of three seed sources were subjected for one growing season to one of four intensities of light: full light, 70 percent light, 37 percent light, and 8 percent light. Seedlings grown in the open were taller than those grown in the shade and had more, generally heavier leaves. Height and leaf growth decreased as the amount of light...
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Peng, Hai-Qin; Liu, Yan; Gao, Xue-Long; Wang, Hong-Wu; Chen, Yi; Cai, Hui-Yi
2017-11-01
While point source pollutions have gradually been controlled in recent years, the non-point source pollution problem has become increasingly prominent. The receiving waters are frequently polluted by the initial stormwater from the separate stormwater system and the wastewater from sewage pipes through stormwater pipes. Consequently, calculating the intercepted runoff depth has become a problem that must be resolved immediately for initial stormwater pollution management. The accurate calculation of intercepted runoff depth provides a solid foundation for selecting the appropriate size of intercepting facilities in drainage and interception projects. This study establishes a separate stormwater system for the Yishan Building watershed of Fuzhou City using the InfoWorks Integrated Catchment Management (InfoWorks ICM), which can predict the stormwater flow velocity and the flow of discharge outlet after each rainfall. The intercepted runoff depth is calculated from the stormwater quality and environmental capacity of the receiving waters. The average intercepted runoff depth from six rainfall events is calculated as 4.1 mm based on stormwater quality. The average intercepted runoff depth from six rainfall events is calculated as 4.4 mm based on the environmental capacity of the receiving waters. The intercepted runoff depth differs when calculated from various aspects. The selection of the intercepted runoff depth depends on the goal of water quality control, the self-purification capacity of the water bodies, and other factors of the region.
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Children's Age-Related Speed--Accuracy Strategies in Intercepting Moving Targets in Two Dimensions
ERIC Educational Resources Information Center
Rothenberg-Cunningham, Alek; Newell, Karl M.
2013-01-01
Purpose: This study investigated the age-related speed--accuracy strategies of children, adolescents, and adults in performing a rapid striking task that allowed the self-selection of the interception position in a virtual, two-dimensional environment. Method: The moving target had curvilinear trajectories that were determined by combinations of…
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NASA Astrophysics Data System (ADS)
Ripetskyj, R. T.; Kit, N. A.
Isolated leafy shoots of the moss Pottia intermedia positioned horizontally on the agar surface in vertically oriented petri dishes regenerate unbranching negatively gravitropic protonemata on upper side of the regenerant. Gravity determines the site of regeneration not the process itself. White light of low intensity unsufficient to induce positive phototropism of dark-grown protonemata can, however, provoke their branching and gametophore bud formation (Ripetskyj et al., 1998; 1999). The presented experiments have been carried out with red light in Biological Research in Canisters/Light Emitting Diode (BRIC/LED) hardware developed at Kennedy Space Center, USA. Seven-day-old dark-grown negatively gravitropic secondary P. intermedia protonemata were positioned differently with respect to gravity vector and to the source of red light of low, 1 or 2 μ mol\\cdot m-2\\cdot s-1, intensities. The light induced intensive branching of the protonemata and gametophore bud formation initiation site of both processes as well as the direction of growth of branches and buds being depent on the position of protonemata with respect to gravity and light vectors. Vertically positioned, i.e. ungravistimulated, dark grown protonemata illuminated from one side with red light of 2 μ mol\\cdot m-2\\cdot s-1 intensity produced 96,9 ± 2,2% of side branches and buds growing directly towards the light source from the lit protonema side. Horizontally disposed protonemata irradiated from below with red light of the same intensity regenerate 31,7 ± 3,9% of branches and buds on the upper, i.e. shaded protonemata side, the upward growth of which should undoubtedly be determined by gravity. In vertically disposed protonemata illuminated with red light of 1 μ mol\\cdot m-2\\cdot s-1 intensity from aside 31,9 ± 5,5% of side branches and buds arised on shaded protonema side and grew away from the light. Illumination of the protonemata in horizontal position from below increased the number of upgrowing branches and buds on upper shaded protonemata side to 76,9 ± 2,4%. The results convincingly speak for stimulating effect of the interaction of gravity and red light of low intensity. Characteristically, the number of side branches and buds on upper side of horizontally disposed protonemata illuminated from below (76,9 ± 2,4%) or parallely to protonemata length from their tips (86,0 ± 5,3%) were slightly, however, statistically significantly, greater than in the case of illumination from above (62,9 ± 3,1%). The effect may be probably be explained by some intensification of gravity action with red light of low intensity from shading of upper cell side or from lighting parallelly with respect to the cell surface. This research was supported by NASA grant NN-09(R).
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Effects of Light Regimes on the Growth of Cherrybark Oak Seedlings
Yanfei Guo; Michael G. Shelton; Brian R. Lockhart
2001-01-01
Light regimes vary significantly within small forest openings, ranging from full sunlight to total shade, and they may affect the establishment and early growth of oak seedlings. We designed modified shadehouses to simulate the complex light conditions within forest openings and tested the effects of daily photosynthetically active radiation (PAR), time of direct light...
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Effects of Light Regimes on 1-Year-Old Sweetgum and Water Oak Seedlings
Yanfei Guo; Michael G. Shelton; Hui Zhang
2002-01-01
Light regimes vary significantly within small forest openings, ranging from full sunlight to total shade. This may affect establishment, early growth, and competitive status of hardwood seedlings. We used modified shadehouses to simulate light conditions within forest openings and to test the effects of daily photosynthetically active radiation and time of direct light...
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An evaluation of light intensity functions for determination of shaded reference stream metabolism.
Zell, Chris; Hubbart, Jason A
2012-04-30
The performance of three single-station whole stream metabolism models were evaluated within three shaded, seasonally hypoxic, Missouri reference streams using high resolution (15-minute) dissolved oxygen (DO), temperature, and light intensity data collected during the summers (July-September) of 2006-2008. The model incorporating light intensity data consistently achieved a lower root mean square error (median RMSE = 0.20 mg L(-1)) relative to models assuming sinusoidal light intensity functions (median RMSE = 0.28 mg L(-1)) and constant diel temperature (median RMSE = 0.53 mg L(-1)). Incorporation of site-specific light intensity into metabolism models better predicted morning DO concentrations and exposure to hypoxic conditions in shaded study streams. Model choice significantly affected (p < 0.05) rate estimates for daily average photosynthesis. Low reaeration (pooled site mean 1.1 day(-1) at 20 °C) coupled with summer temperatures (pooled site mean = 25.8 °C) and low to moderate community respiration (site median 1.0-3.0 g O(2) m(-2) day(-1)) yielded diel dissolved oxygen concentrations near or below critical aquatic life thresholds in studied reference streams. Quantifying these process combinations in best-available or least-disturbed (i.e., reference) systems advances our understanding of regional dissolved oxygen expectations and informs environmental management policy. Additional research is warranted to better link landscape processes with distributed sources that contribute to community respiration. Copyright © 2011 Elsevier Ltd. All rights reserved.
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2006-04-01
Primary mirror of Zerodur with Pilkington 747 coating • FOV = 0.104 degrees Airborne Intercept Monitoring RTO-MP-SET-105 16 - 3 UNCLASSIFIED...Pointing System (SPS). The STS is a 0.75 meter aperture Mersenne Cassegrain telescope and the SAT is a 0.34 meter aperture 3- mirror anastigmat telescope...UNLIMITED UNCLASSIFIED/UNLIMITED • Air Flow to Mitigate Thermal “Seeing” Effects • Light weighted primary mirror to reduce mass The SAT
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Green light in photomorphogenic development
NASA Astrophysics Data System (ADS)
Maruhnich, Stefanie Anne
Light quality, quantity, and duration provide essential environmental cues that shape plant growth and development. Over the last century, researchers have worked to discover how plants sense, integrate, and respond to red, blue, and far-red light. Green light is often considered a “benign” wavelength with little to no effect in plant development. However, sparse experiments in the literature demonstrate that green effects are often counterintuitive to normal light responses and oppose red- and blue-light-induced responses. Green light effects on plant growth and development are described here through the use of custom, tunable LED, light-emitting diode, chambers. These light sources allow for specific light qualities and quantities to be administered. The effects of green wavebands were assessed when red and blue photomorphogenic systems were active to answer the question: Are the effects of an inhibitor (green light) more evident in the presence of inducers (red and blue light)? In seedlings, supplemental green light increased hypocotyl elongation opposite to classical inhibition of hypocotyl elongation associated with growth in light and induced by red and blue wavebands. Results indicate that added green light induced a reversion of light-grown phenotypes. In mature plants, supplemental green light induced phenotypes typical of the shade-avoidance syndrome, including elongated petioles, smaller leaf areas, and leaf hyponasty. These responses are typical of lower-light conditions or far-red enriched environments. Contrary to far-red-light-induced shade-avoidance, data indicate green delays flowering. In Arabidopsis and strawberry plants, anthocyanin levels also decreased when green light was added to red and blue light treatments, which is again opposite to normal light-induced phenotypes. Photoreceptor mutants were tested and indicate green light effects in early development are cryptochromedependent. However, green-light-induced shade-avoidance responses were cryptochrome-independent. A candidate gene approach was used to identify other elements required for green light sensing and/or response. Defects in some green light responses were observed for mutants in CCD8/Max4, a putative carotenoid cleavage enzyme with high sequence similarity to a critical enzyme in animal vision. These data support a role for green light in plant development which opposes normal light-induced responses and indicate the existence of at least two green light sensing systems.
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Efficacy of cold light bleaching using different bleaching times and their effects on human enamel.
Wang, Wei; Zhu, Yuhe; Li, Jiajia; Liao, Susan; Ai, Hongjun
2013-01-01
This study investigated the efficacy of cold light bleaching using different bleaching times and the effects thereof on tooth enamel. Before and after bleaching, stained tooth specimens were subjected to visual and instrumental colorimetric assessments using Vita Shade Guide and spectrophotometric shade matching. Enamel surface alterations were examined using scanning electron microscopy (SEM) to analyze surface morphology, surface microhardness (SMH) measurement to determine changes in mechanical properties, and X-ray diffraction (XRD) to characterize post-bleaching enamel composition. Cold light bleaching successfully improved tooth color, with optimal efficacy when bleaching time was beyond 10 min. Significant differences in surface morphology were observed among the different bleaching times, but no significant differences were observed for enamel composition and surface microhardness among the different bleaching times. Results of this study revealed an association between the bleaching time of cold light bleaching and its whitening efficacy. Together with the results on enamel surface changes, this study provided positive evidence to support cold light bleaching as an in-office bleaching treatment.
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Buller, David B; Andersen, Peter A; Walkosz, Barbara J; Scott, Michael D; Beck, Larry; Cutter, Gary R
2016-01-01
Exposure to solar ultraviolet radiation during recreation is a risk factor for skin cancer. A trial evaluated an intervention to promote advanced sun protection (sunscreen pre-application/reapplication; protective hats and clothing; use of shade) during vacations. Adult visitors to hotels/resorts with outdoor recreation (i.e., vacationers) participated in a group-randomized pretest-posttest controlled quasi-experimental design in 2012-14. Hotels/resorts were pair-matched and randomly assigned to the intervention or untreated control group. Sun. protection (e.g., clothing, hats, shade and sunscreen) was measured in cross-sectional samples by observation and a face-to-face intercept survey during two-day visits. Initially, 41 hotel/resorts (11%) participated but 4 dropped out before posttest. Hotel/resorts were diverse (employees=30 to 900; latitude=24° 78' N to 50° 52' N; elevation=2ft. to 9726ft. above sea level), and had a variety of outdoor venues (beaches/pools, court/lawn games, golf courses, common areas, and chairlifts). At pretest, 4347 vacationers were observed and 3531 surveyed. More females were surveyed (61%) than observed (50%). Vacationers were mostly 35-60years old, highly educated (college education=68%) and non-Hispanic white (93%), with high-risk skin types (22%). Vacationers reported covering 60% of their skin with clothing. Also, 40% of vacationers used shade; 60% applied sunscreen; and 42% had been sunburned. The trial faced challenges recruiting resorts but result showed that the large, multi-state sample of vacationers were at high risk for solar UV exposure. Copyright © 2015 Elsevier Inc. All rights reserved.
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Zhang, Ziyan; He, Kate S.; Li, Bo
2015-01-01
Release from specialist insect herbivores may allow invasive plants to evolve traits associated with decreased resistance and increased competitive ability. Given that there may be genetic trade-off between resistance and tolerance, invasive plants could also become more tolerant to herbivores. Although it is widely acknowledged that light availability affects tolerance to herbivores, little information is available for whether the effect of light availability on tolerance differ between the introduced and native populations. We conducted a common garden experiment in the introduced range of Alternanthera philoxeroides using ten invasive US and ten native Argentinean populations at two levels of light availability and in the presence or absence of a specialist stem-boring insect Agasicles hygrophila. Plant biomass (total and storage root biomass), two allocation traits (root/shoot ratio and branch intensity, branches biomass/main stem biomass) and two functional traits (specific stem length and specific leaf area), which are potentially associated with herbivore resistance and light capture, were measured. Overall, we found that A. philoxeroides from introduced ranges had comparable biomass and tolerance to specialist herbivores, lower branch intensity, lower specific stem length and specific leaf area. Moreover, introduced populations displayed higher shade tolerance of storage root biomass and lower plastic response to shading in specific stem length. Finally, light availability had no significant effect on evolution of tolerance to specialist herbivores of A. philoxeroides. Our results suggest that post-introduction evolution might have occurred in A. philoxeroides. While light availability did not influence the evolution of tolerance to specialist herbivores, increased shade tolerance and release from specialist insects might have contributed to the successful invasion of A. philoxeroides. PMID:26407176
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Voolstra, Christian R.; Wild, Christian
2014-01-01
In the Central Red Sea, healthy coral reefs meet intense coastal development, but data on the effects of related stressors for reef functioning are lacking. This in situ study therefore investigated the independent and combined effects of simulated overfishing through predator/grazer exclusion and simulated eutrophication through fertilizer addition on settlement of reef associated invertebrates on light-exposed and -shaded tiles over 4 months. At the end of the study period invertebrates had almost exclusively colonized shaded tiles. Algae were superior settling competitors on light-exposed tiles. On the shaded tiles, simulated overfishing prevented settlement of hard corals, but significantly increased settlement of polychaetes, while simulated eutrophication only significantly decreased hard coral settlement relative to controls. The combined treatment significantly increased settlement of bryozoans and bivalves compared to controls and individual manipulations, but significantly decreased polychaetes compared to simulated overfishing. These results suggest settlement of polychaetes and hard corals as potential bioindicators for overfishing and eutrophication, respectively, and settlement of bivalves and bryozoans for a combination of both. Therefore, if the investigated stressors are not controlled, phase shifts from dominance by hard corals to that by other invertebrates may occur at shaded reef locations in the Central Red Sea. PMID:24765573
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[Preparation and chromaticity properties of colored dental 3Y-TZP ceramics].
Yi, Yuan-fu; Wang, Chen; Tian, Jie-mo; Liu, Hong-chen; Wen, Ning
2008-10-01
To obtain and investigate the chromaticity properties of colored dental 3Y-TZP ceramics with different colorant combinations. Colorant combinations were mixed with TZ-3Y-S powder, then the mixtures were compacted at 200 MPa using cold isostatic pressure, densely sintered at 1500 degrees C for 2 h forming 5 graded colored dental zirconia ceramics. Specimen were sectioned into 10 mm x 10 mm x 0.5 mm and 10 mm x l0 mmx 1 mm slices from the sintered blocks. Color measurement was performed under black background using spectrophotometer. The chromaticity properties were compared with that of the VITA In-Ceram YZ shade guide. Five colored dental zirconia ceramics were obtained. The lightness decreased gradually, and the chroma value increased gradually. The color differences of the two thickness specimens were little. The parameters of the color space were L*: 67.76-77.78; a*: -2.19-3.80; b*: 12.13-25.01, which was similar with that of the VITA In-Ceram YZ shade guide, while the lowest value of lightness was relatively higher than that of the VITA In-Ceram YZ shade guide. Colored 3Y-TZP dental ceramics are suitable for clinical use. There is a need to develop more darkness shaded zirconia dental ceramics.
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Jessen, Christian; Voolstra, Christian R; Wild, Christian
2014-01-01
In the Central Red Sea, healthy coral reefs meet intense coastal development, but data on the effects of related stressors for reef functioning are lacking. This in situ study therefore investigated the independent and combined effects of simulated overfishing through predator/grazer exclusion and simulated eutrophication through fertilizer addition on settlement of reef associated invertebrates on light-exposed and -shaded tiles over 4 months. At the end of the study period invertebrates had almost exclusively colonized shaded tiles. Algae were superior settling competitors on light-exposed tiles. On the shaded tiles, simulated overfishing prevented settlement of hard corals, but significantly increased settlement of polychaetes, while simulated eutrophication only significantly decreased hard coral settlement relative to controls. The combined treatment significantly increased settlement of bryozoans and bivalves compared to controls and individual manipulations, but significantly decreased polychaetes compared to simulated overfishing. These results suggest settlement of polychaetes and hard corals as potential bioindicators for overfishing and eutrophication, respectively, and settlement of bivalves and bryozoans for a combination of both. Therefore, if the investigated stressors are not controlled, phase shifts from dominance by hard corals to that by other invertebrates may occur at shaded reef locations in the Central Red Sea.
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NASA Astrophysics Data System (ADS)
Jayanti, L. D.; Yunus, A.; Pujiasmanto, B.; Widyastuti, Y.
2018-03-01
This study aims to examine the intensity of shade and proper dosage of fertilizer to maximize the content of ursolic acid and pearl grass yield. The field-run study was carried out at the Medicinal Plant Garden of the Research and Development of Medicinal Plants and Traditional Medicines (B2P2TOOT) and the laboratory research was conducted at the B2P2TOOT Phytochemistry Laboratory. The experiment design was Randomized Complete Block Design with Split Plot pattern with the intensity (three levels) as main plot and fertilizer dosage (four levels) as sub plot. The data obtained were analyzed using the variance analysis, if there were significant differences tested further by using Duncan’s Multiple Range Test (DMRT) with 95% confidence level. The results showed that shade treatment gave significant effects on plant height, number of branches, root length, fresh weight and dry weight. The treatment of a fertilizer dosage 15 tons/ha gave the best results on fresh weight and dry weight. The combination of N0K0 treatment (without shade, without cow manure) resulted in the highest quality of ursolic acid as it featured a light blue color when detected under UV366 light.
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Nieto-Lugilde, Diego; Lenoir, Jonathan; Abdulhak, Sylvain; Aeschimann, David; Dullinger, Stefan; Gégout, Jean-Claude; Guisan, Antoine; Pauli, Harald; Renaud, Julien; Theurillat, Jean-Paul; Thuiller, Wilfried; Van Es, Jérémie; Vittoz, Pascal; Willner, Wolfgang; Wohlgemuth, Thomas; Zimmermann, Niklaus E.; Svenning, Jens-Christian
2015-01-01
The role of competition for light among plants has long been recognised at local scales, but its importance for plant species distributions at larger spatial scales has generally been ignored. Tree cover modifies the local abiotic conditions below the canopy, notably by reducing light availability, and thus, also the performance of species that are not adapted to low-light conditions. However, this local effect may propagate to coarser spatial grains, by affecting colonisation probabilities and local extinction risks of herbs and shrubs. To assess the effect of tree cover at both the plot- and landscape-grain sizes (approximately 10-m and 1-km), we fit Generalised Linear Models (GLMs) for the plot-level distributions of 960 species of herbs and shrubs using 6,935 vegetation plots across the European Alps. We ran four models with different combinations of variables (climate, soil and tree cover) at both spatial grains for each species. We used partial regressions to evaluate the independent effects of plot- and landscape-grain tree cover on plot-level plant communities. Finally, the effects on species-specific elevational range limits were assessed by simulating a removal experiment comparing the species distributions under high and low tree cover. Accounting for tree cover improved the model performance, with the probability of the presence of shade-tolerant species increasing with increasing tree cover, whereas shade-intolerant species showed the opposite pattern. The tree cover effect occurred consistently at both the plot and landscape spatial grains, albeit most strongly at the former. Importantly, tree cover at the two grain sizes had partially independent effects on plot-level plant communities. With high tree cover, shade-intolerant species exhibited narrower elevational ranges than with low tree cover whereas shade-tolerant species showed wider elevational ranges at both limits. These findings suggest that forecasts of climate-related range shifts for herb and shrub species may be modified by tree cover dynamics. PMID:26290621
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Modeling shade tree use by beef cattle as a function of black globe temperature and time of day
NASA Astrophysics Data System (ADS)
Foust, Amanda M.; Headlee, William L.
2017-12-01
Increasing temperatures associated with global climate change threaten to disrupt agricultural systems such as beef production, yet relatively little is known about the use of natural tree shade to mitigate the negative effects of heat stress on beef cattle. In this study, we evaluated how temperature and time of day influenced the utilization of tree shade in relation to coloration, orientation, and behavior of beef cattle in a pasture system. Temperatures in shade and direct sunlight were measured using black globe temperature (BGT) data loggers. Time-lapse images from game cameras were used to obtain counts of shade usage, coloration, orientation, and behavior of cattle throughout the daytime hours. In general, we found that shade utilization and most of the predominating orientations and behaviors differed significantly ( P < 0.05) by both time of day (Hour) and BGT in direct sunlight (BGTsun), while interactions between these two effects (Hour × BGTsun) were often nonsignificant. The mean percentage of the herd using shade was highest in mid-morning (87-96%) and early afternoon (97%), but also increased with BGTsun regardless of the time of day; these trends were similar for both dark- and light-colored cattle. Lying down was the dominant behavior exhibited in the shade, while foraging was the most prevalent behavior in the sun. When herd shade usage was lowest in mid- to late-afternoon (<1%) we also observed an increase in the use of heat-mitigating orientations in the sun (37-47%). We discuss some practical implications of these results, including the potential use of temperature thresholds to interpret cattle behaviors and shade usage.
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Modeling shade tree use by beef cattle as a function of black globe temperature and time of day.
Foust, Amanda M; Headlee, William L
2017-12-01
Increasing temperatures associated with global climate change threaten to disrupt agricultural systems such as beef production, yet relatively little is known about the use of natural tree shade to mitigate the negative effects of heat stress on beef cattle. In this study, we evaluated how temperature and time of day influenced the utilization of tree shade in relation to coloration, orientation, and behavior of beef cattle in a pasture system. Temperatures in shade and direct sunlight were measured using black globe temperature (BGT) data loggers. Time-lapse images from game cameras were used to obtain counts of shade usage, coloration, orientation, and behavior of cattle throughout the daytime hours. In general, we found that shade utilization and most of the predominating orientations and behaviors differed significantly (P < 0.05) by both time of day (Hour) and BGT in direct sunlight (BGT sun ), while interactions between these two effects (Hour × BGT sun ) were often nonsignificant. The mean percentage of the herd using shade was highest in mid-morning (87-96%) and early afternoon (97%), but also increased with BGT sun regardless of the time of day; these trends were similar for both dark- and light-colored cattle. Lying down was the dominant behavior exhibited in the shade, while foraging was the most prevalent behavior in the sun. When herd shade usage was lowest in mid- to late-afternoon (<1%) we also observed an increase in the use of heat-mitigating orientations in the sun (37-47%). We discuss some practical implications of these results, including the potential use of temperature thresholds to interpret cattle behaviors and shade usage.
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Kaur, Ravneet; Albano, Peter P.; Cole, Justin G.; Hagerty, Jason; LeAnder, Robert W.; Moss, Randy H.; Stoecker, William V.
2015-01-01
Background/Purpose Early detection of malignant melanoma is an important public health challenge. In the USA, dermatologists are seeing more melanomas at an early stage, before classic melanoma features have become apparent. Pink color is a feature of these early melanomas. If rapid and accurate automatic detection of pink color in these melanomas could be accomplished, there could be significant public health benefits. Methods Detection of three shades of pink (light pink, dark pink, and orange pink) was accomplished using color analysis techniques in five color planes (red, green, blue, hue and saturation). Color shade analysis was performed using a logistic regression model trained with an image set of 60 dermoscopic images of melanoma that contained pink areas. Detected pink shade areas were further analyzed with regard to the location within the lesion, average color parameters over the detected areas, and histogram texture features. Results Logistic regression analysis of a separate set of 128 melanomas and 128 benign images resulted in up to 87.9% accuracy in discriminating melanoma from benign lesions measured using area under the receiver operating characteristic curve. The accuracy in this model decreased when parameters for individual shades, texture, or shade location within the lesion were omitted. Conclusion Texture, color, and lesion location analysis applied to multiple shades of pink can assist in melanoma detection. When any of these three details: color location, shade analysis, or texture analysis were omitted from the model, accuracy in separating melanoma from benign lesions was lowered. Separation of colors into shades and further details that enhance the characterization of these color shades are needed for optimal discrimination of melanoma from benign lesions. PMID:25809473
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Accurate shade image matching by using a smartphone camera.
Tam, Weng-Kong; Lee, Hsi-Jian
2017-04-01
Dental shade matching by using digital images may be feasible when suitable color features are properly manipulated. Separating the color features into feature spaces facilitates favorable matching. We propose using support vector machines (SVM), which are outstanding classifiers, in shade classification. A total of 1300 shade tab images were captured using a smartphone camera with auto-mode settings and no flash. The images were shot at angled distances of 14-20cm from a shade guide at a clinic equipped with light tubes that produced a 4000K color temperature. The Group 1 samples comprised 1040 tab images, for which the shade guide was randomly positioned in the clinic, and the Group 2 samples comprised 260 tab images, for which the shade guide had a fixed position in the clinic. Rectangular content was cropped manually on each shade tab image and further divided into 10×2 blocks. The color features extracted from the blocks were described using a feature vector. The feature vectors in each group underwent SVM training and classification by using the "leave-one-out" strategy. The top one and three accuracies of Group 1 were 0.86 and 0.98, respectively, and those of Group 2 were 0.97 and 1.00, respectively. This study provides a feasible technique for dental shade classification that uses the camera of a mobile device. The findings reveal that the proposed SVM classification might outperform the shade-matching results of previous studies that have performed similarity measurements of ΔE levels or used an S, a*, b* feature set. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
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Kaur, R; Albano, P P; Cole, J G; Hagerty, J; LeAnder, R W; Moss, R H; Stoecker, W V
2015-11-01
Early detection of malignant melanoma is an important public health challenge. In the USA, dermatologists are seeing more melanomas at an early stage, before classic melanoma features have become apparent. Pink color is a feature of these early melanomas. If rapid and accurate automatic detection of pink color in these melanomas could be accomplished, there could be significant public health benefits. Detection of three shades of pink (light pink, dark pink, and orange pink) was accomplished using color analysis techniques in five color planes (red, green, blue, hue, and saturation). Color shade analysis was performed using a logistic regression model trained with an image set of 60 dermoscopic images of melanoma that contained pink areas. Detected pink shade areas were further analyzed with regard to the location within the lesion, average color parameters over the detected areas, and histogram texture features. Logistic regression analysis of a separate set of 128 melanomas and 128 benign images resulted in up to 87.9% accuracy in discriminating melanoma from benign lesions measured using area under the receiver operating characteristic curve. The accuracy in this model decreased when parameters for individual shades, texture, or shade location within the lesion were omitted. Texture, color, and lesion location analysis applied to multiple shades of pink can assist in melanoma detection. When any of these three details: color location, shade analysis, or texture analysis were omitted from the model, accuracy in separating melanoma from benign lesions was lowered. Separation of colors into shades and further details that enhance the characterization of these color shades are needed for optimal discrimination of melanoma from benign lesions. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
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Esteban, R; Jiménez, M S; Morales, D; Jiménez, E T; Hormaetxe, K; Becerril, J M; Osmond, B; García-Plazaola, J I
2008-05-01
Short- and long-term responses of the violaxanthin (V) and lutein epoxide (Lx) cycles were studied in two species of Lauraceae: sweet bay laurel (Laurus nobilis L.) and avocado (Persea americana L.). The Lx content exceeded the V content in shade leaves of both species. Both Lx and V were de-epoxidised on illumination, but only V was fully restored by epoxidation in low light. Violaxanthin was preferentially de-epoxidised in low light in L. nobilis. This suggests that Lx accumulates with leaf ageing, partly because its conversion to lutein is limited in shade. After exposure to strong light, shade leaves of avocado readjusted the total pools of alpha- and beta-xanthophyll cycles by de novo synthesis of antheraxanthin, zeaxanthin and lutein. This occurred in parallel with a sustained depression of F(v)/F(m). In Persea indica, a closely related but low Lx species, F(v)/F(m) recovered faster after a similar light treatment, suggesting the involvement of the Lx cycle in sustained energy dissipation. Furthermore, the seasonal correlation between non-reversible Lx and V photoconversions and pre-dawn F(v)/F(m) in sun leaves of sweet bay supported the conclusion that the Lx cycle is involved in a slowly reversible downregulation of photosynthesis analogous to the V cycle.
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Lu, Yanfen; Bu, Yufen; Hao, Suxiao; Wang, Yaru; Zhang, Jie; Tian, Ji; Yao, Yuncong
2017-03-01
Fruit pigment accumulation, which represents an important indicator of nutrient quality and appearance value, is often affected by low light under rain, cloud, fog and haze conditions during the veraison period. It is not known whether continuous low light interferes with the production and accumulation of secondary metabolites in veraison fruit. In this paper, we measured pigments and the transcriptional level of genes related to secondary metabolites, i.e., flavonoid biosynthesis in the peel and flesh of Malus crabapple 'Radiant' fruit in response to normal light and shade from 10th July to 30th August. The results showed crosstalk between the flavonoid biosynthetic genes and the involvement of key transcription factors such as McMYB4, McMYB7, McMYB10, and McMYB16 in the regulation of the ratio of anthocyanins and flavanols, which accounted for the different colouration of the fruit peel and flesh under shade conditions. A model is proposed for the regulation of the flavonoid pathway in the peel and flesh of 'Radiant' fruit based on our study results. Moreover, the molecular mechanism for 'Radiant' fruit colouration provides reference information for understanding the light regulatory mechanism involved in the biosynthesis of flavonoids and for designing the next generation of apple breeding. Copyright © 2017 Elsevier B.V. All rights reserved.
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Hydraulic acclimation to shading in boreal conifers of varying shade tolerance.
Schoonmaker, Amanda L; Hacke, Uwe G; Landhäusser, Simon M; Lieffers, Victor J; Tyree, Melvin T
2010-03-01
The purpose of this study was to determine how shading affects the hydraulic and wood-anatomical characteristics of four boreal conifers (Pinus banksiana, Pinus contorta, Picea glauca and Picea mariana) that differ in shade tolerance. Plants were grown in an open field and under a deciduous-dominated overstory for 6 years. Sapwood- and leaf-area specific conductivity, vulnerability curves, and anatomical measurements (light and scanning electron microscopy) were made on leading shoots from six to nine trees of each treatment combination. There was no difference in sapwood-area specific conductivity between open-grown and understory conifers, although two of four species had larger tracheid diameters in the open. Shaded conifers appeared to compensate for small diameter tracheids by changes in pit membrane structure. Scanning electron microscopy revealed that understory conifers had thinner margo strands, greater maximum pore size in the margo, and more torus extensions. All of these trends may contribute to inadequate sealing of the torus. This is supported by the fact that all species showed increased vulnerability to cavitation when grown in the understory. Although evaporative demand in an understory environment is low, a rapid change into fully exposed conditions could be detrimental for shaded conifers.
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Retkute, Renata; Townsend, Alexandra J; Murchie, Erik H; Jensen, Oliver E; Preston, Simon P
2018-05-25
Diurnal changes in solar position and intensity combined with the structural complexity of plant architecture result in highly variable and dynamic light patterns within the plant canopy. This affects productivity through the complex ways that photosynthesis responds to changes in light intensity. Current methods to characterize light dynamics, such as ray-tracing, are able to produce data with excellent spatio-temporal resolution but are computationally intensive and the resulting data are complex and high-dimensional. This necessitates development of more economical models for summarizing the data and for simulating realistic light patterns over the course of a day. High-resolution reconstructions of field-grown plants are assembled in various configurations to form canopies, and a forward ray-tracing algorithm is applied to the canopies to compute light dynamics at high (1 min) temporal resolution. From the ray-tracer output, the sunlit or shaded state for each patch on the plants is determined, and these data are used to develop a novel stochastic model for the sunlit-shaded patterns. The model is designed to be straightforward to fit to data using maximum likelihood estimation, and fast to simulate from. For a wide range of contrasting 3-D canopies, the stochastic model is able to summarize, and replicate in simulations, key features of the light dynamics. When light patterns simulated from the stochastic model are used as input to a model of photoinhibition, the predicted reduction in carbon gain is similar to that from calculations based on the (extremely costly) ray-tracer data. The model provides a way to summarize highly complex data in a small number of parameters, and a cost-effective way to simulate realistic light patterns. Simulations from the model will be particularly useful for feeding into larger-scale photosynthesis models for calculating how light dynamics affects the photosynthetic productivity of canopies.
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Deng, Yanming; Li, Congcong; Shao, Qingsong; Ye, Xiaoqing; She, Jianming
2012-06-01
A double petal (DP) and a multi petal (MP) type jasmine (Jasminum sambac Ait.) growth and flowering was known largely affected by different levels of irradiance. Here, our objective was to determine the effects of shade on photosynthesis related characteristics and chloroplast ultrastructure of these two types. In both types, net photosynthetic rate (Pn), stomatal conductance (g(s)) and transpiration rate increased with decreasing irradiance from 100% to 20%, while both maximum and variable fluorescence showed a steady increase, and photochemical and nonphotochemical quenching indexes declined. At each conducted time, chlorophyll a, b and carotenoids contents in DP type shaded leaves increased whereas those in MP type decreased at 5% irradiance (considered as extreme shade). The maximum photochemical efficiency of photosystem II of DP plants showed subtle changes but that of MP plants declined by shading thereafter 21 days of treatment. Observation of chloroplast ultrastructure showed its best development in the leaves of DP and MP types mostly from 50% to 20% irradiance (considered as weak and moderate shade, respectively). At each shade treatment, Pn, g(s) and water use efficiency of DP-jasmine were always higher than those of MP-jasmine, thus the shade tolerance ability of the former was higher than that of the latter. The results showed that full sunlight and 5% natural irradiance caused photoinhibition and light deficiency of jasmine plants respectively, and modulating chloroplast development by the more numbers of thylakoids and grana to contain more photosynthetic pigments is an important shade tolerance mechanism of DP type. Copyright © 2012 Elsevier Masson SAS. All rights reserved.
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Marcondes, Maurem; Paranhos, Maria Paula Gandolfi; Spohr, Ana Maria; Mota, Eduardo Gonçalves; da Silva, Isaac Newton Lima; Souto, André Arigony; Burnett, Luiz Henrique
2009-07-01
The Nd:YAG laser can be used in Dentistry to remove soft tissue, disinfect canals in endodontic procedures and prevent caries. However, there is no protocol for Nd:YAG laser application in dental bleaching. The aims of this in vitro study were: (a) to observe the tooth shade alteration when hydrogen peroxide whitening procedures are associated with dyes with different wavelengths and irradiated with Nd:YAG laser or halogen light; (b) to measure the Vickers (VHN) enamel microhardness before and after the whitening procedure; (c) to evaluate the tensile bond strength of two types of adhesive systems applied on bleached enamel; (d) to observe the failure pattern after bond strength testing; (e) to evaluate the pulpal temperature during the bleaching procedures with halogen light or laser; (f) to measure the kinetic reaction of hydrogen peroxide. Extracted sound human molar crowns were sectioned in the mesiodistal direction to obtain 150 fragments that were divided into five groups for each adhesive system: WL (H(2)O(2) + thickener and Nd:YAG), WH (H(2)O(2) + thickener and halogen light), QL (H(2)O(2) + carbopol + Q-switch and Nd:YAG), QH (H(2)O(2) + carbopol + Q-switch and halogen light), and C (Control, without whitening agent). Shade assessment was made with a shade guide and the microhardness tests were performed before and after the bleaching procedures. Immediately afterwards, the groups were restored with the adhesive systems Adper Single Bond 2 or Solobond M plus composite resin, and the tensile bond strength test was performed. The temperature was measured by thermocouples placed on the enamel surface and intrapulpal chamber. The kinetics of hydrogen peroxide was observed by ultraviolet analysis. The shade changed seven levels for Nd:YAG laser groups and eight levels for halogen light. According to the student's t-test, there was no statistical difference between the VHN before and after the whitening protocols (p > 0.05). The tensile bond strength showed no statistical significance between the test groups and the controls, considering both adhesive systems tested by ANOVA and Tukey tests (p > 0.05). The predominant failure pattern after bond strength testing was mixed. The temperature was safe for laser and halogen light. The kinetic reaction showed that after 5 min all the hydrogen peroxide had been consumed. Nd:YAG laser associated with hydrogen peroxide bleached the enamel, the shade being similar to that obtained with the traditional method performed with halogen light. Moreover, the Vickers' microhardness and bond strength values were not altered in comparison with those for nonbleached enamel. (c) 2008 Wiley Periodicals, Inc.
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ERIC Educational Resources Information Center
Chihak, Benjamin J.; Plumert, Jodie M.; Ziemer, Christine J.; Babu, Sabarish; Grechkin, Timofey; Cremer, James F.; Kearney, Joseph K.
2010-01-01
Two experiments examined how 10- and 12-year-old children and adults intercept moving gaps while bicycling in an immersive virtual environment. Participants rode an actual bicycle along a virtual roadway. At 12 test intersections, participants attempted to pass through a gap between 2 moving, car-sized blocks without stopping. The blocks were…
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High-light acclimation in Quercus robur L.seedlings upon over-topped a shaded environment
Anna M. Jensen; Emile S. Gardiner; Kevin C. Vaughn
2012-01-01
High developmental plasticity at the seedling-level during acclimation to the light environment may be an important determinant of seedling establishment and growth in temperate broadleaf forests, especially in dense understories where spatial light availability can vary greatly. Pedunculate oak (Quercus robur L.) seedlings were raised beneath a...
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Chmura, Daniel J; Tjoelker, Mark G
2008-05-01
Crown architecture and size influence leaf area distribution within tree crowns and have large effects on the light environment in forest canopies. The use of selected genotypes in combination with silvicultural treatments that optimize site conditions in forest plantations provide both a challenge and an opportunity to study the biological and environmental determinants of forest growth. We investigated tree growth, crown development and leaf traits of two elite families of loblolly pine (Pinus taeda L.) and one family of slash pine (P. elliottii Mill.) at canopy closure. Two contrasting silvicultural treatments -- repeated fertilization and control of competing vegetation (MI treatment), and a single fertilization and control of competing vegetation treatment (C treatment) -- were applied at two experimental sites in the West Gulf Coastal Plain in Texas and Louisiana. At a common tree size (diameter at breast height), loblolly pine trees had longer and wider crowns, and at the plot-level, intercepted a greater fraction of photosynthetic photon flux than slash pine trees. Leaf-level, light-saturated assimilation rates (A(max)) and both mass- and area-based leaf nitrogen (N) decreased, and specific leaf area (SLA) increased with increasing canopy depth. Leaf-trait gradients were steeper in crowns of loblolly pine trees than of slash pine trees for SLA and leaf N, but not for A(max). There were no species differences in A(max), except in mass-based photosynthesis in upper crowns, but the effect of silvicultural treatment on A(max) differed between sites. Across all crown positions, A(max) was correlated with leaf N, but the relationship differed between sites and treatments. Observed patterns of variation in leaf properties within crowns reflected acclimation to developing light gradients in stands with closing canopies. Tree growth was not directly related to A(max), but there was a strong correlation between tree growth and plot-level light interception in both species. Growth efficiency was unaffected by silvicultural treatment. Thus, when coupled with leaf area and light interception at the crown and canopy levels, A(max) provides insight into family and silvicultural effects on tree growth.
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Interception of rainfall in a young loblolly pine plantation
Marvin D. Hoover
1953-01-01
Those who have sought refuge during a storm have found a tree to be an effective umbrella for a light shower but leaky in a heavy rain. Even so, it is usually possible to stay slightly more dry under forest canopy than in the open. That is because a portion of the rain is stored on leaves and branches and eventually evaporated back to the air. The term interception is...
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Chai, Shengfeng; Tang, Jianmin; Mallik, Azim; Shi, Yancai; Zou, Rong; Li, Jitao; Wei, Xiao
2018-02-07
Camellia nitidissima, a rare and endangered shrub is narrowly distributed in South China and North Vietnam occurring in forest understory. Their light tolerance mechanism is unclear. We measured photosynthesis and related parameters on 2-years-old cuttings growing at 10, 30, 50 and 100% sunlight. Our research question was: At what light level are C. nitidissima cuttings responding most favorably, and what is the eco-physiological basis for their response to light? We hypothesized that as a forest understory growth of C. nitidissima would respond most favorably at low to intermediate light by optimizing photosynthetic activity, and high light will affect photosynthetic functions due to photoinhibition, damage of photosynthetic apparatus and concomitant enzyme activity. With increasing light, the maximum net photosynthetic rate (P Nmax ) and apparent quantum yield (AQY) decreased, while the light compensation point increased, and light saturation point first increased followed by a decrease. The P Nmax and AQY under 50 and 100% sunlight were significantly lower than that under 10 and 30% sunlight. The chlorophyll fluorescence parameters F m , F v , F v /F m all decreased under high light (> 50%). The contents of chlorophyll a (Chla), chlorophyll b (Chlb), and carotenoid (Car) decreased with increasing light. Relative conductivity, malondialdehyde (MDA) and proline contents in leaves were significantly increased in high light but we found no significant difference in these indices at 10 and 30% sunlight. We conclude that C. nitidissima is a shade adapted plant with poor adaptability to high light (> 50%). The novelty of this research is the demonstration of the eco-physiological basis of its light tolerance (conversely, shade adaptation) mechanisms indicated by decreased photosynthetic activity, chlorophyll fluorescence, Chla, Chlb and Car contents and concomitant increase in relative conductivity, MDA and proline contents at high light causing photoinhibition. For artificial propagation of C. nitidissima we recommend growing cuttings below 30% sunlight. For in situ conservation of this valuable, rare and endangered shrub it is necessary to protect its natural habitats.
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Perceptual organization of shape, color, shade, and lighting in visual and pictorial objects
Pinna, Baingio
2012-01-01
The main questions we asked in this work are the following: Where are representations of shape, color, depth, and lighting mostly located? Does their formation take time to develop? How do they contribute to determining and defining a visual object, and how do they differ? How do visual artists use them to create objects and scenes? Is the way artists use them related to the way we perceive them? To answer these questions, we studied the microgenetic development of the object perception and formation. Our hypothesis is that the main object properties are extracted in sequential order and in the same order that these roles are also used by artists and children of different age to paint objects. The results supported the microgenesis of object formation according to the following sequence: contours, color, shading, and lighting. PMID:23145283
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Optical properties of base dentin ceramics for all-ceramic restorations.
Shiraishi, Takanobu; Wood, Duncan J; Shinozaki, Nobuya; van Noort, Richard
2011-02-01
The study was conducted to compare the optical parameters of VM7(®) M-shade base dentin ceramics (VITA, Germany) for all ceramic restorations to the chemical composition across the 3D-MASTER(®) shade system. Three disc samples, 13 mm diameter and 1.4 mm thickness, were produced for each M-shade following the manufacturer's instructions. Each disc was ground and polished to a thickness of 1.0 mm. Spectral light transmittance and reflectance data were recorded in the visible spectrum under the standard illuminant D65 and 2° observer at 10 nm intervals by using a computer-controlled spectrophotometer. Opacity, translucency and opalescence parameters were determined for each sample. (1) Spectral transmittance and reflectance in the short-wavelength range systematically decreased with increasing chroma number (M1, M2, M3) when compared within the same value (lightness) group. (2) Spectral transmittance and reflectance decreased systematically across the whole visible spectrum with increasing value group number when compared within the same chroma group. (3) Analysis of relationship between chemical composition and various optical parameters for all the samples showed the significant contribution of ZrO₂ and Y₂O₃ substances to optical properties of the present material. Systematic variations in optical properties of VM7(®) M-shade base dentin ceramics were observed throughout the 3D-MASTER(®) shade system and were suggested to be caused by the fine structure of the sample which can interfere with shorter wavelengths in the visible spectrum. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
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Shading of a computer-generated hologram by zone plate modulation.
Kurihara, Takayuki; Takaki, Yasuhiro
2012-02-13
We propose a hologram calculation technique that enables reconstructing a shaded three-dimensional (3D) image. The amplitude distributions of zone plates, which generate the object points that constitute a 3D object, were two-dimensionally modulated. Two-dimensional (2D) amplitude modulation was determined on the basis of the Phong reflection model developed for computer graphics, which considers the specular, diffuse, and ambient reflection light components. The 2D amplitude modulation added variable and constant modulations: the former controlled the specular light component and the latter controlled the diffuse and ambient components. The proposed calculation technique was experimentally verified. The reconstructed image showed specular reflection that varied depending on the viewing position.
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Diverse coral communities in mangrove habitats suggest a novel refuge from climate change
Yates, Kimberly K.; Rogers, Caroline S.; Herlan, James J.; Brooks, Gregg R.; Smiley, Nathan A.; Larson, Rebekka A.
2014-01-01
Over 30 species of scleractinian corals were growing in association with mangroves. Corals were thriving in low-light (more than 70% attenuation of incident PAR) from mangrove shading and at higher temperatures than nearby reef tract corals. A higher percentage of C. natans colonies were living shaded by mangroves, and no shaded colonies were bleached. Fewer D. labyrinthiformis colonies were shaded by mangroves, however more unshaded colonies were bleached. A combination of substrate and habitat heterogeneity, proximity of different habitat types, hydrographic conditions, and biological influences on seawater chemistry generate chemical conditions that buffer against ocean acidification. This previously undocumented refuge for corals provides evidence for adaptation of coastal organisms and ecosystem transition due to recent climate change. Identifying and protecting other natural, non-reef coral refuges is critical for sustaining corals and other reef species into the future.
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Streby, Henry M.; Kramer, Gunnar R.; Peterson, Sean M.; Lehman, Justin A.; Buehler, David A.; Andersen, David
2018-01-01
Lisovski et al. [1] describe the widely recognized limitations of light-level geolocator data for identifying short-distance latitudinal movements, recommend that caution be used when interpreting such data, intimated that we did not use such caution and argued that environmental shading likely explained the Golden-winged Warbler (Vermivora chrysoptera) movements described in our 2015 report [2] . Lisovski et al. [1] conclude that the bird movements we reported could not be disentangled from estimation error in stationary animals caused by environmental shading. We argue that, to the contrary, these hypotheses can easily be disentangled because the premise that environmental shading caused synchronous and parallel error among geolocators is false. With their assertion that our location estimates could be biased by >3,500 km on a day with no observable local sources of shading, Lisovski et al. [1] have taken a position of incredulity toward all geolocator-based animal movement data published to date.
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Using Cross-Polarized Photography as a Guide for Selecting Resin Composite Shade.
Villavicencio-Espinoza, C A; Narimatsu, M H; Furuse, A Y
The restoration of single discolored maxillary anterior teeth is still a difficult task, as not only shape and surface characterization play an important role in the success of the treatment, but the propagation of light throughout the restorative material does as well. In some cases, small changes in morphology, color, and brightness will be noticeable. These factors are sometimes very tricky, and shade guides alone are difficult to use for color selection. This article proposes a protocol of employing cross-polarization imaging for improving the accuracy of the shade selection of resin composites. The step-by-step technique is presented for the restoration of a single discolored tooth.
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USDA-ARS?s Scientific Manuscript database
Row spacing effects on light interception and extinction coefficient have been inconsistent for maize (Zea mays L.) when calculated with field measurements. To avoid inconsistencies due to variable light conditions and variable leaf canopies, we used a model to describe three-dimensional (3D) shoot ...
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Composite shade guides and color matching.
Paolone, Gaetano; Orsini, Giovanna; Manauta, Jordi; Devoto, Walter; Putignano, Angelo
2014-01-01
Finding reliable systems that can help the clinician match the color of direct composite restorations is often an issue. After reviewing several composite shade guides available on the market and outlining their main characteristics and limits (unrealistic specimen thickness, not made with the same material the clinician will use, only a few allow to overlap enamel tabs on dentin ones), the authors evaluated the reliability of a system designed to produce self-made standardized "tooth-shaped" shade guide specimens. Small changes in composite enamel thickness may determine huge differences in esthetic outcomes. In conclusion, the results showed that all the specimens demonstrated comparable enamel thickness in all the examined areas (cervical, middle, incisal).
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de Moraes Porto, Isabel Cristina Celerino; Ramos de Brito, Andréia Cristina; Parolia, Abhishek
2013-01-01
Background: Among the advice on prevent cross-infection was included usage of mechanical barriers on tips of photoactivation units. However, questions about the use of protective barriers placed on the light-curing unit's tips and the possibility of interference with the ability of guaranteeing an effective polymerization of composite resins need to be clarified. Aims: The aim of this study was to evaluate the effect of cross infection control barriers used on the light-curing device tips on the cure depth of composite resin. Materials and Methods: Power density measurements from the light-cure unit were recorded with a radiometer on ten separate occasions with different types and placement modes of each barrier (low-density polyethylene and polyvinyl chloride (PVC) film – smooth and folds) and no-barrier (control). Cure depth of TPH™ Spectrum™ resin, A2-A4, was evaluated by the scraping test. Statistical Analysis: The data were analyzed using Student's t-test or ANOVA one-way with Tukey's test (α =0.05). Results: Same type of barrier and different shades (A2, A4) of composite exhibited significant difference in the cure depth among all groups (P < 0.05). Both low-density polyethylene and PVC film folded barriers produced a significant reduction in the light intensity (P < 0.05). Conclusions: Regarding the resin shade, there was a significant reduction in the cure depth of A4 composite resin (dark shade) but this reduction is not enough to cause any adverse effect on the material's clinical performance. Therefore, disposable barriers can be recommended for use over the end of the light guide. PMID:23833455
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Fini, Alessio; Loreto, Francesco; Tattini, Massimiliano; Giordano, Cristiana; Ferrini, Francesco; Brunetti, Cecilia; Centritto, Mauro
2016-05-01
The ability to modify mesophyll conductance (gm ) in response to changes in irradiance may be a component of the acclimation of plants to shade-sun transitions, thus influencing species-specific distributions along light-gradients, and the ecological niches for the different species. To test this hypothesis we grew three woody species of the Oleaceae family, the evergreen Phillyrea latifolia (sun-requiring), the deciduous Fraxinus ornus (facultative sun-requiring) and the hemi-deciduous Ligustrum vulgare (shade tolerant) at 30 or 100% sunlight irradiance. We show that neither mesophyll conductance calculated with combined gas exchange and chlorophyll fluorescence techniques (gm) nor CO2 assimilation significantly varied in F. ornus because of sunlight irradiance. This corroborates previous suggestions that species with high plasticity for light requirements, do not need to undertake extensive reorganization of leaf conductances to CO2 diffusion to adapt to different light environments. On the other hand, gm steeply declined in L. vulgare and increased in P. latifolia exposed to full-sun conditions. In these two species, leaf anatomical traits are in part responsible for light-driven changes in gm , as revealed by the correlation between gm and mesophyll conductance estimated by anatomical parameters (gmA). Nonetheless, gm was greatly overestimated by gmA when leaf metabolism was impaired because of severe light stress. We show that gm is maximum at the light intensity at which plant species have evolved and we conclude that gm actually plays a key role in the sun and shade adaptation of Mediterranean species. The limits of gmA in predicting mesophyll conductance are also highlighted. © 2015 Scandinavian Plant Physiology Society.
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Responses of Primula vulgaris to light quality in the maternal and germination environments.
Marin, M; Blandino, C; Laverack, G; Toorop, P; Powell, A A
2018-05-22
In the model species Arabidopsis thaliana phytochromes mediate dormancy and germination responses to seasonal cues experienced during seed maturation on the maternal plants. However, the effect of the maternal light environment on seed germination in native wild species has not been studied well. This is particularly important given its practical application in the context of environmental restoration, when there can be marked changes in the canopy. Plants of Primula vulgaris were grown in the field over two vegetative seasons under four shading treatments from low to high ratio of red to far-red light (R:FR). Leaf and seed traits were assessed in response to the light treatments. The germination of seeds from these four maternal environments (pre-dispersal) was investigated at seven light and five temperature treatments (post-dispersal). Thinner leaves, larger leaf area and greater chlorophyll content were found in plants growing in reduced R:FR. Shading in the maternal environment led to increased seed size and yield, although the conditions experienced by the maternal plants had no effect on seed germination. Seeds responded strongly to the cues experienced in their immediate germination environment. Germination was always enhanced under higher R:FR conditions. The observed phenotypic trait variation plays a major role in the ability of P. vulgaris to grow in a wide range of light conditions. However, the increased germination capacity in response to a higher R:FR for all maternal environments suggests potential for seedling establishment under vegetative shade only in the presence of canopy gaps. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
MacIntyre, H.L.; Geider, R.J.; McKay, R.M.
Net phytoplankton (>20 {mu}m) comprised 51 {plus_minus} 9% of the total chlorophyll (Chl) in a Skeletonema costatum-dominated spring bloom in Delaware Bay. The net phytoplankton had low C:N and high protein:carbohydrate ratios, indicating that their growth was nutrient-replete. Their photosynthetic responses were characterized by low specific absorption, low light-limited and light-saturated rates of photosynthesis, and high quantum yields, indicative of acclimation to low irradiance and internal self-shading. High fucoxanthin: Chl ratios also indicated low light acclimation, but high photoprotective xanthophyll: Chl ratios suggested a high capacity for photoprotective energy dissipation. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) could be activated and deactivated in responsemore » to changes in irradiance and was fully activated at the surface of the water column and fully deactivated in aphotic deep water. Maximum Rubisco activity was correlated with Rubisco content and bulk protein content of the phytoplankton and with light-saturated rates of photosynthesis measured in short (<20-min) incubations. Long (60-min) incubations caused a decrease in the light-saturated rate of photosynthesis, possibly because of feedback limitation. While feedback limitation is unlikely to occur in the water column it should be considered when estimating productivity in well-mixed waters from fixed light-depth incubations. 90 refs., 7 figs., 2 tabs.« less
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Kudish, Avraham I; Harari, Marco; Evseev, Efim G
2011-10-01
The composition of the incident solar global ultraviolet B (UVB) radiation with regard to its beam and diffuse radiation fractions is highly relevant with regard to outdoor sun protection. This is especially true with respect to sun protection during leisure-time outdoor sun exposure at the shore and pools, where people tend to escape the sun under shade trees or different types of shading devices, e.g., umbrellas, overhangs, etc., believing they offer protection from the erythemal solar radiation. The degree of sun protection offered by such devices is directly related to the composition of the solar global UVB radiation, i.e., its beam and diffuse fractions. The composition of the incident solar global UVB radiation can be determined by measuring the global UVB (using Solar Light Co. Inc., Model 501A UV-Biometer) and either of its components. The beam component of the UVB radiation was determined by measuring the normal incidence beam radiation using a prototype, tracking instrument consisting of a Solar Light Co. Inc. Model 501A UV-Biometer mounted on an Eppley Solar Tracker Model St-1. The horizontal beam component of the global UVB radiation was calculated from the measured normal incidence using a simple geometric correlation and the diffuse component is determined as the difference between global and horizontal beam radiations. Horizontal and vertical surfaces positioned under a horizontal overhang/sunshade or an umbrella are not fully protected from exposure to solar global UVB radiation. They can receive a significant fraction of the UVB radiation, depending on their location beneath the shading device, the umbrella radius and the albedo (reflectance) of the surrounding ground surface in the case of a vertical surface. Shading devices such as an umbrella or horizontal overhang/shade provide relief from the solar global radiation and do block the solar global UVB radiation to some extent; nevertheless, a significant fraction of the solar global UVB radiation does penetrate this supposedly 'protective or comfort zone'. As a result, it is imperative to either apply sunscreen or cover up the exposed body surfaces even when under such shading devices. © 2011 John Wiley & Sons A/S.
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Valladares, Fernando; Zaragoza-Castells, Joana; Sánchez-Gómez, David; Matesanz, Silvia; Alonso, Beatriz; Portsmuth, Angelika; Delgado, Antonio; Atkin, Owen K
2008-12-01
Plants are naturally exposed to multiple, frequently interactive stress factors, most of which are becoming more severe due to global change. Established plants have been reported to facilitate the establishment of juvenile plants, but net effects of plant-plant interactions are difficult to assess due to complex interactions among environmental factors. An investigation was carried out in order to determine how two dominant evergreen shrubs (Quercus ilex and Arctostaphylos uva-ursi) co-occurring in continental, Mediterranean habitats respond to multiple abiotic stresses and whether the shaded understorey conditions ameliorate the negative effects of drought and winter frosts on the physiology of leaves. Microclimate and ecophysiology of sun and shade plants were studied at a continental plateau in central Spain during 2004-2005, with 2005 being one of the driest and hottest years on record; several late-winter frosts also occurred in 2005. Daytime air temperature and vapour pressure deficit were lower in the shade than in the sun, but soil moisture was also lower in the shade during the spring and summer of 2005, and night-time temperatures were higher in the shade. Water potential, photochemical efficiency, light-saturated photosynthesis, stomatal conductance and leaf 13C composition differed between sun and shade individuals throughout the seasons, but differences were species specific. Shade was beneficial for leaf-level physiology in Q. ilex during winter, detrimental during spring for both species, and of little consequence in summer. The results suggest that beneficial effects of shade can be eclipsed by reduced soil moisture during dry years, which are expected to be more frequent in the most likely climate change scenarios for the Mediterranean region.
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Valladares, Fernando; Zaragoza-Castells, Joana; Sánchez-Gómez, David; Matesanz, Silvia; Alonso, Beatriz; Portsmuth, Angelika; Delgado, Antonio; Atkin, Owen K.
2008-01-01
Background and Aims Plants are naturally exposed to multiple, frequently interactive stress factors, most of which are becoming more severe due to global change. Established plants have been reported to facilitate the establishment of juvenile plants, but net effects of plant–plant interactions are difficult to assess due to complex interactions among environmental factors. An investigation was carried out in order to determine how two dominant evergreen shrubs (Quercus ilex and Arctostaphylos uva-ursi) co-occurring in continental, Mediterranean habitats respond to multiple abiotic stresses and whether the shaded understorey conditions ameliorate the negative effects of drought and winter frosts on the physiology of leaves. Methods Microclimate and ecophysiology of sun and shade plants were studied at a continental plateau in central Spain during 2004–2005, with 2005 being one of the driest and hottest years on record; several late-winter frosts also occurred in 2005. Key Results Daytime air temperature and vapour pressure deficit were lower in the shade than in the sun, but soil moisture was also lower in the shade during the spring and summer of 2005, and night-time temperatures were higher in the shade. Water potential, photochemical efficiency, light-saturated photosynthesis, stomatal conductance and leaf 13C composition differed between sun and shade individuals throughout the seasons, but differences were species specific. Shade was beneficial for leaf-level physiology in Q. ilex during winter, detrimental during spring for both species, and of little consequence in summer. Conclusions The results suggest that beneficial effects of shade can be eclipsed by reduced soil moisture during dry years, which are expected to be more frequent in the most likely climate change scenarios for the Mediterranean region. PMID:18819947
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Wu, Longmei; Zhang, Wujun; Ding, Yanfeng; Zhang, Jianwei; Cambula, Elidio D; Weng, Fei; Liu, Zhenghui; Ding, Chengqiang; Tang, She; Chen, Lin; Wang, Shaohua; Li, Ganghua
2017-01-01
Low solar radiation caused by industrial development and solar dimming has become a limitation in crop production in China. It is widely accepted that low solar radiation influences many aspects of plant development, including slender, weak stems and susceptibility to lodging. However, the underlying mechanisms are not well understood. To clarify how low solar radiation affects stem mechanical strength formation and lodging resistance, the japonica rice cultivars Wuyunjing23 (lodging-resistant) and W3668 (lodging-susceptible) were grown under field conditions with normal light (Control) and shading (the incident light was reduced by 60%) with a black nylon net. The yield and yield components, plant morphological characteristics, the stem mechanical strength, cell wall components, culm microstructure, gene expression correlated with cellulose and lignin biosynthesis were measured. The results showed that shading significantly reduced grain yield attributed to reduction of spikelets per panicles and grain weight. The stem-breaking strength decreased significantly under shading treatment; consequently, resulting in higher lodging index in rice plant in both varieties, as revealed by decreased by culm diameter, culm wall thickness and increased plant height, gravity center height. Compared with control, cell wall components including non-structural carbohydrate, sucrose, cellulose, and lignin reduced quite higher. With histochemical straining, shading largely reduced lignin deposition in the sclerenchyma cells and vascular bundle cells compared with control, and decreased cellulose deposition in the parenchyma cells of culm tissue in both Wuyunjing23 and W3668. And under shading condition, gene expression involved in secondary cell wall synthesis, OsPAL, OsCOMT, OsCCoAOMT, OsCCR , and OsCAD2 , and primary cell wall synthesis, OsCesA1, OsCesA3 , and OsCesA8 were decreased significantly. These results suggest that gene expression involved in the reduction of lignin and cellulose in both sclerenchyma and parenchyma cells, which attribute to lignin and cellulose in culm tissue and weak mechanical tissue, consequently, result in poor stem strength and higher lodging risks. Highlights : (1) Shading decreases the stem mechanical strength of japonica rice by decreasing non-structural carbohydrate, sucrose, lignin, and cellulose accumulation in culms. (2) The decrease of carbon source under shading condition is the cause for the lower lignin and cellulose accumulation in culm. (3) The expression of genes involved in lignin and primarily cell wall cellulose biosynthesis ( OsCesA1, OsCesA3 , and OsCesA8 ) at the stem formation stage are down-regulated under shading condition, inducing defective cell wall development and poor lodging resistance.
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Łukowski, Adrian; Giertych, Marian J.; Zadworny, Marcin; Mucha, Joanna; Karolewski, Piotr
2015-01-01
The monophagous beetle, Altica brevicollis coryletorum, is a major leaf pest of Corylus avellana (common hazel). In contrast to majority of the other studied species of shrubs, sunlit leaves are grazed to a much greater extent than shaded leaves. Since the observation of a link between leaf irradiance level and A. brevicollis feeding is unique, we hypothesized that feeding preference of this beetle species is related to the speed needed to escape threats i.e. faster jumping. We also hypothesized that sunlit leaves are more nutritious and easier to consume than the leaves of shaded shrubs. Results indicated that beetle mass was greater in beetles occupying sunlit leaves, which is consistent with our second hypothesis. The study also confirmed under laboratory conditions, that larvae, pupae and beetles that were fed full-light (100% of full light) leaves were significantly heavier than those fed with shaded leaves (15% of full light). In the high irradiance conditions (higher temperature) duration of larval development is also reduced. Further results indicated that neither the concentration of soluble phenols, leaf toughness, or the number of trichomes could explain the insect’s preference for sunlit leaves. Notably, measurements of jump length of beetles of this species, both in the field and under laboratory conditions, indicated that the defense pattern related to jumping was associated with light conditions. The jump length of beetles in the sun was significantly higher than in the shade. Additionally, in laboratory tests, beetle defense (jumping) was more strongly affected by temperature (15, 25, or 35°C for 24h) than by leaf type. The effect of sunlit, higher nutrient leaves (greater level of non-structural carbohydrates) on defense (jumping) appears to be indirect, having a positive effect on insect mass in all developmental stages. PMID:25927706
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York, Paul H; Gruber, Renee K; Hill, Ross; Ralph, Peter J; Booth, David J; Macreadie, Peter I
2013-01-01
Understanding how multiple environmental stressors interact to affect seagrass health (measured as morphological and physiological responses) is important for responding to global declines in seagrass populations. We investigated the interactive effects of temperature stress (24, 27, 30 and 32°C) and shading stress (75, 50, 25 and 0% shade treatments) on the seagrass Zostera muelleri over a 3-month period in laboratory mesocosms. Z. muelleri is widely distributed throughout the temperate and tropical waters of south and east coasts of Australia, and is regarded as a regionally significant species. Optimal growth was observed at 27°C, whereas rapid loss of living shoots and leaf mass occurred at 32°C. We found no difference in the concentration of photosynthetic pigments among temperature treatments by the end of the experiment; however, up-regulation of photoprotective pigments was observed at 30°C. Greater levels of shade resulting in high photochemical efficiencies, while elevated irradiance suppressed effective quantum yield (ΔF/FM'). Chlorophyll fluorescence fast induction curves (FIC) revealed that the J step amplitude was significantly higher in the 0% shade treatment after 8 weeks, indicating a closure of PSII reaction centres, which likely contributed to the decline in ΔF/FM' and photoinhibition under higher irradiance. Effective quantum yield of PSII (ΔF/FM') declined steadily in 32°C treatments, indicating thermal damage. Higher temperatures (30°C) resulted in reduced above-ground biomass ratio and smaller leaves, while reduced light led to a reduction in leaf and shoot density, above-ground biomass ratio, shoot biomass and an increase in leaf senescence. Surprisingly, light and temperature had few interactive effects on seagrass health, even though these two stressors had strong effects on seagrass health when tested in isolation. In summary, these results demonstrate that populations of Z. muelleri in south-eastern Australia are sensitive to small chronic temperature increases and light decreases that are predicted under future climate change scenarios.
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A shading experiment was conducted over a growing season to measure the effects of light reduction on Vallisneria americana in Perdido Bay on the Florida-Alabama border, and to determine the response of heterotrophic bacteria in the rhizosphere. Plants subjected to 92% light redu...
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Switchgrass leaf area index and light extinction coefficients
USDA-ARS?s Scientific Manuscript database
Biomass production simulation modeling for plant species is often dependent upon accurate simulation or measurement of canopy light interception and radiation use efficiency. With the recent interest in converting large tracts of land to biofuel species cropping, modeling vegetative yield with grea...
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NASA Astrophysics Data System (ADS)
Weber, Raphael; Hoch, Günter
2017-04-01
Non-structural carbohydrates (NSC, i.e. free sugars and starch) are regarded as freely available carbon (C) reserves in plants. They are often quantified to estimate a plant's C-balance, assuming that NSC are controlled by the net-balance between photo-assimilation and C-usage (respiration, growth and other sinks). Within a recent field experiment, we investigated the extent, to which C-reserves (NSC) can be formed in young trees against prevailing C-sink demands (growth) under C-limitation. A total of almost 1000 individuals of two-year-old tree saplings from 6 deciduous, broadleaved species and 4 evergreen conifer species were planted on a field side. Half of the trees per species were treated with long-term C-limitation by exposing them to continuous deep shade conditions (5% of natural PPFD) under a permanent shading tent. C gas-exchange, growth and NSC tissue concentrations were analyzed in shaded and unshaded saplings for two consecutive years. Three months after the beginning of the experiment, leaf photosynthesis acclimatized to the low light conditions, with leaves of shaded trees showing significantly higher SLA and lower light saturation and maximum photosynthesis. During the second season of the experiment, most species exhibited very strong reductions in NSC, but much less pronounced reductions in growth. In contrast, other species, with few exceptions, kept NSC concentrations similar to unshaded controls, while growth virtually stopped under deep shade. In conclusion, we found species-specific strategies in the trees' C-household after two years of C-limitation, that fall into two major carbon allocation strategies: 1) "C-spenders", which deplete C reserves in order to keep up significant growth, and 2) "C-savers", which reduce C sink activities to a minimum in order to store substantial amounts of C reserves. Overall, early-successional species tended to follow the first strategy, while late-successional species tended to save higher C reserve pools in trade-off with growth.
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Application of a digital technique in evaluating the reliability of shade guides.
Cal, E; Sonugelen, M; Guneri, P; Kesercioglu, A; Kose, T
2004-05-01
There appears to be a need for a reliable method for quantification of tooth colour and analysis of shade. Therefore, the primary objective of this study was to show the applicability of graphic software in colour analysis and secondly to investigate the reliability of commercial shade guides produced by the same manufacturer, using this digital technique. After confirming the reliability and reproducibility of the digital method by using self-assessed coloured images, three shade guides of the same manufacturer were photographed in daylight and in studio environments with a digital camera and saved in tagged image file format (TIFF) format. Colour analysis of each photograph was performed using the Adobe Photoshop 4.0 graphic program. Luminosity, and red, green, blue (L and RGB) values of each shade tab of each shade guide were measured and the data were subjected to statistical analysis using the repeated measure Anova test. The L and RGB values of the images taken in daylight differed significantly from those of the images taken in studio environment (P < 0.05). In both environments, the luminosity and red values of the shade tabs were significantly different from each other (P < 0.05). It was concluded that, when the environmental conditions were kept constant, the Adobe Photoshop 4.0 colour analysis program could be used to analyse the colour of images. On the other hand, the results revealed that the accuracy of shade tabs widely being used in colour matching should be readdressed.
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Kubisch, Petra; Leuschner, Christoph; Coners, Heinz; Gruber, Andreas; Hertel, Dietrich
2017-01-01
Low temperatures are crucial for the formation of the alpine treeline worldwide. Since soil temperature in the shade of tree canopies is lower than in open sites, it was assumed that self-shading may impair the trees' root growth performance. While experiments with tree saplings demonstrate root growth impairment at soil temperatures below 5-7°C, field studies exploring the soil temperature - root growth relationship at the treeline are missing. We recorded soil temperature and fine root abundance and dynamics in shaded and sun-exposed areas under canopies of isolated Pinus cembra trees at the alpine treeline. In contrast to the mentioned assumption, we found more fine root biomass and higher fine root growth in colder than in warmer soil areas. Moreover, colder areas showed higher fine root turnover and thus lower root lifespan than warmer places. We conclude that P. cembra balances enhanced fine root mortality in cold soils with higher fine root activity and by maintaining higher fine root biomass, most likely as a response to shortage in soil resource supply. The results from our study highlight the importance of in situ measurements on mature trees to understand the fine root response and carbon allocation pattern to the thermal growth conditions at the alpine treeline.
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Lichtenberg, Mads; Kühl, Michael
2015-08-01
Macroalgae live in an ever-changing light environment affected by wave motion, self-shading and light-scattering effects, and on the thallus scale, gradients of light and chemical parameters influence algal photosynthesis. However, the thallus microenvironment and internal gradients remain underexplored. In this study, microsensors were used to quantify gradients of light, O2 concentration, variable chlorophyll fluorescence, photosynthesis and O2 consumption as a function of irradiance in the cortex and medulla layers of Fucus serratus. The two cortex layers showed more efficient light utilization compared to the medulla, calculated both from electron transport rates through photosystem II and from photosynthesis-irradiance curves. At moderate irradiance, the upper cortex exhibited onset of photosynthetic saturation, whereas lower thallus layers exhibited net O2 consumption. O2 consumption rates in light varied with depth and irradiance and were more than two-fold higher than dark respiration. We show that the thallus microenvironment of F. serratus exhibits a highly stratified balance of production and consumption of O2 , and when the frond was held in a fixed position, high incident irradiance levels on the upper cortex did not saturate photosynthesis in the lower thallus layers. We discuss possible photoadaptive responses and consequences for optimizing photosynthetic activity on the basis of vertical differences in light attenuation coefficients. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
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[Effects of light intensity on Quercus liaotungensis seed germination and seedling growth].
Yan, Xing-fu; Wang, Jian-li; Zhou, Li-biao
2011-07-01
This paper studied the effects of different shading (55.4%, 18.9%, 5.5%, 2.2%, 0.5% , and 0.3% natural sunlight) on the seed germination and seedling growth of Quercus liaotungensis. The seed germination rate and germination index were the highest (72.5% and 0.22, respectively) at 55.4% natural sunlight, declined with decreasing light intensity, and were the lowest (42.5% and 0.11, respectively) at 0.3% natural sunlight. Strong light had definite delaying effect on the germination. The index of germination vigor increased with decreasing light intensity, being the maximum at 0.5% natural sunlight. The delay of seed germination under strong light could be the selective tradeoff on varied seed fates. Strong light benefited the basal stem diameter and root system growth and dry mass accumulation of Q. liaotunensis seedling, but resulted in the minimum seedlings height (6.06 cm). Greater morphological plasticity was observed for the seedlings under different shading, which lent support to the higher adaptability of the seedlings to light environment. For example, the specific leaf area, specific shoot length, specific root length, and chlorophyll b and total chlorophyll contents were the maximum at 0.5% natural sunlight, being 142.57 cm2 x g(-1), 156.86 cm x g(-1), 271.87 cm x g(-1), 0.07 g x cm(-2), and 0.24 g x cm(-2), respectively, and the minimum at 55.4% natural sunlight, being 44.89 cm2 x g(-1), 52.84 cm x g(-1), 101.98 cm x g(-1), 0.04 g x cm(-2), and 0.15 g x cm(-2), respectively. The variation of the root/shoot ratio of Q. liaotungensis seedlings under different shading could be the effects of the combination of light intensity and water availability.
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Cerrudo, Ignacio; Caliri-Ortiz, M Emilia; Keller, Mercedes M; Degano, M Eugenia; Demkura, Patricia V; Ballaré, Carlos L
2017-05-01
Under conditions that involve a high risk of competition for light among neighbouring plants, shade-intolerant species often display increased shoot elongation and greater susceptibility to pathogens and herbivores. The functional links between morphological and defence responses to crowding are not well understood. In Arabidopsis, the protein JAZ10 is thought to play a key role connecting the inactivation of the photoreceptor phytochrome B (phyB), which takes place under competition for light, with the repression of jasmonate-mediated plant defences. Here, we show that a null mutation of the JAZ10 gene in Arabidopsis did not affect plant growth nor did it suppress the shade-avoidance responses elicited by phyB inactivation. However, the jaz10 mutation restored many of the defence traits that are missing in the phyB mutant, including the ability to express robust responses to jasmonate and to accumulate indolic glucosinolates. Furthermore, the jaz10phyB double mutant showed a significantly increased resistance to the pathogenic fungus Botrytis cinerea compared with the phyB parental line. Our results demonstrate that, by inactivating JAZ10, it is possible to partially uncouple shade avoidance from defence suppression in Arabidopsis. These findings may provide clues to improve plant resistance to pathogens in crops that are planted at high density. © 2016 John Wiley & Sons Ltd.
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An Inexpensive Apparatus for Growing Photosynthetic Microorganisms in Exotic Atmospheres
NASA Astrophysics Data System (ADS)
Thomas, David J.; Herbert, Stephen K.
2005-02-01
Given the need for a light source, cyanobacteria and other photosynthetic microorganisms can be difficult and expensive to grow in large quantities. Lighted growth chambers and incubators typically cost 50-100% more than standard microbiological incubators. Self-shading of cells in liquid cultures prevents the growth of dense suspensions. Growing liquid cultures on a shaker table or lighted shaker incubator achieves greater cell densities, but adds considerably to the cost. For experiments in which gases other than air are required, the cost for conventional incubators increases even more. We describe an apparatus for growing photosynthetic organisms in exotic atmospheres that can be built relatively inexpensively (approximately $100 U.S.) using parts available from typical hardware or department stores (e.g., Wal-mart or K-mart). The apparatus uses microfiltered air (or other gases) to aerate, agitate, and mix liquid cultures, thus achieving very high cell densities (A750 > 3). Because gases are delivered to individual culture tubes, a variety of gas mixes can be used without the need for enclosed chambers. The apparatus works with liquid cultures of unicellular and filamentous species, and also works with agar slants.
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Arnold, Sarah E J; Chittka, Lars
2012-07-01
Patchy illumination presents foraging animals with a challenge, as the targets being sought may appear to vary in colour depending on the illumination, compromising target identification. We sought to explore how the bumblebee Bombus terrestris copes with tasks involving flower colour discrimination under patchy illumination. Light patches varied between unobscured daylight and leaf-shade, as a bee might encounter in and around woodland. Using a flight arena and coloured filters, as well as one or two different colours of artificial flower, we quantified how bees chose to forage when presented with foraging tasks under patchy illumination. Bees were better at discriminating a pair of similar colours under simulated unobscured daylight illumination than when foraging under leaf-shade illumination. Accordingly, we found that bees with prior experience of simulated daylight but not leaf-shade illumination initially preferred to forage in simulated daylight when all artificial flowers contained rewards as well as when only one colour was rewarding, whereas bees with prior experience of both illuminants did not exhibit this preference. Bees also switched between illuminants less than expected by chance. This means that bees prefer illumination conditions with which they are familiar, and in which rewarding flower colours are easily distinguishable from unrewarding ones. Under patchy illumination, colour discrimination performance was substantially poorer than in homogenous light. The bees' abilities at coping with patchy light may therefore impact on foraging behaviour in the wild, particularly in woodlands, where illumination can change over short spatial scales.
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Does Acacia dealbata express shade tolerance in Mediterranean forest ecosystems of South America?
Aguilera, Narciso; Sanhueza, Carolina; Guedes, Lubia M; Becerra, José; Carrasco, Sebastián; Hernández, Víctor
2015-01-01
The distribution of Acacia dealbata Link (Fabaceae) in its non-native range is associated with disturbed areas. However, the possibility that it can penetrate the native forest during the invasion process cannot be ruled out. This statement is supported by the fact that this species has been experimentally established successfully under the canopy of native forest. Nonetheless, it is unknown whether A. dealbata can express shade tolerance traits to help increase its invasive potential. We investigated the shade tolerance of A. dealbata under the canopy of two native forests and one non-native for three consecutive years, as well as its early growth and photosynthetic performance at low light intensities (9, 30, and 70 μmol m−2sec−1) under controlled conditions. We found many A. dealbata plants surviving and growing under the canopy of native and non-native forests. The number of plants of this invasive species remained almost constant under the canopy of native forests during the years of study. However, the largest number of A. dealbata plants was found under the canopy of non-native forest. In every case, the distribution pattern varied with a highest density of plants in forest edges decreasing progressively toward the inside. Germination and early growth of A. dealbata were slow but successful at three low light intensities tested under controlled conditions. For all tested light regimes, we observed that in this species, most of the energy was dissipated by photochemical processes, in accordance with the high photosynthetic rates that this plant showed, despite the really low light intensities under which it was grown. Our study reveals that A. dealbata expressed shade tolerance traits under the canopy of native and non-native forests. This behavior is supported by the efficient photosynthetic performance that A. dealbata showed at low light intensities. Therefore, these results suggest that Mediterranean forest ecosystems of South America can become progressively invaded by A. dealbata and provide a basis for estimating the possible impacts that this invasive species can cause in these ecosystems in a timescale. PMID:26380668
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Effects of fluorescent lighting on in vitro micropropagation of Lemna minor
NASA Astrophysics Data System (ADS)
Somsri, Kollawat; Pinyopich, Pataradawn; Mohammed, Waleed S.
2010-05-01
The vegetative in vitro propagation of Lemna minor stain SING-4 exposed to two different types of fluorescent light sources, Philips TLD 36W/54 and Toshiba FL40T8BRF/36, was studied. The liquid culture medium contained 4.43gl-1 phytohormone-free full-strength Murashige & Skoog (MS) basal medium with vitamins, 30gl-1 sucrose, and 1gl-1 MES. The results showed that both plant cultures had undergone normal asexual reproduction with an exponential increase trend. Cultures exposed to Toshiba FL40T8BRF/36 reproduced at a slightly faster rate while expressing significantly greener foliage (leaf color chart shade No.8), which indicates the presence of more chlorophyll, than cultures exposed to Philips TLD 36W/54 (leaf color chart shade No.4). The data obtained from our experiment reveals that light emitted from Toshiba FL40T8BRF/36 produces healthier and higher quality cultures.
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Mobile Bay, Alabama area seen in Skylab 4 Earth Resources Experiment Package
NASA Technical Reports Server (NTRS)
1974-01-01
A near vertical view of the Mobile Bay, Alabama area seen in this Skylab 4 Earth Resources Experiment Package S190-B (five-inch earth terrain camera) photograph taken from the Skylab space station in earth orbit. North of Mobile the Tombigbee and Alabama Rivers join to form the Mobile River. Detailed configuration of the individual stream channels and boundaries can be defined as the Mobile River flows into Mobile Bay and into the Gulf of Mexico. The Mobile River Valley with its numerous stream channels is a distinct light shade in contrast to the dark green shade of the adjacent areas. The red coloration of Mobile Bay reflects the sediment load carried into the bay by the rivers. The westerly movement of the shore currents at the mouth of Mobile Bay is shown by the contrasting light blue of the sediment-laden current the the blue of the Gulf. Agricultural areas east and west of Mobile Bay are characterized by a rectangular pattern in green to white shades. Color variations may reflect
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NASA Technical Reports Server (NTRS)
Balasubramanian, Kunjithapatha; White, Victor; Yee, Karl; Echternach, Pierre; Muller, Richard; Dickie, Matthew; Cady, Eric; Mejia Prada, Camilo; Ryan, Daniel; Poberezhskiy, Ilya;
2015-01-01
Star light suppression technologies to find and characterize faint exoplanets include internal coronagraph instruments as well as external star shade occulters. Currently, the NASA WFIRST-AFTA mission study includes an internal coronagraph instrument to find and characterize exoplanets. Various types of masks could be employed to suppress the host star light to about 10 -9 level contrast over a broad spectrum to enable the coronagraph mission objectives. Such masks for high contrast internal coronagraphic imaging require various fabrication technologies to meet a wide range of specifications, including precise shapes, micron scale island features, ultra-low reflectivity regions, uniformity, wave front quality, achromaticity, etc. We present the approaches employed at JPL to produce pupil plane and image plane coronagraph masks by combining electron beam, deep reactive ion etching, and black silicon technologies with illustrative examples of each, highlighting milestone accomplishments from the High Contrast Imaging Testbed (HCIT) at JPL and from the High Contrast Imaging Lab (HCIL) at Princeton University. We also present briefly the technologies applied to fabricate laboratory scale star shade masks.
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NASA Astrophysics Data System (ADS)
Balasubramanian, Kunjithapatham; White, Victor; Yee, Karl; Echternach, Pierre; Muller, Richard; Dickie, Matthew; Cady, Eric; Mejia Prada, Camilo; Ryan, Daniel; Poberezhskiy, Ilya; Zhou, Hanying; Kern, Brian; Riggs, A. J.; Zimmerman, Neil T.; Sirbu, Dan; Shaklan, Stuart; Kasdin, Jeremy
2015-09-01
Star light suppression technologies to find and characterize faint exoplanets include internal coronagraph instruments as well as external star shade occulters. Currently, the NASA WFIRST-AFTA mission study includes an internal coronagraph instrument to find and characterize exoplanets. Various types of masks could be employed to suppress the host star light to about 10-9 level contrast over a broad spectrum to enable the coronagraph mission objectives. Such masks for high contrast internal coronagraphic imaging require various fabrication technologies to meet a wide range of specifications, including precise shapes, micron scale island features, ultra-low reflectivity regions, uniformity, wave front quality, achromaticity, etc. We present the approaches employed at JPL to produce pupil plane and image plane coronagraph masks by combining electron beam, deep reactive ion etching, and black silicon technologies with illustrative examples of each, highlighting milestone accomplishments from the High Contrast Imaging Testbed (HCIT) at JPL and from the High Contrast Imaging Lab (HCIL) at Princeton University. We also present briefly the technologies applied to fabricate laboratory scale star shade masks.
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Light Attenuation in a 14-year-old Loblolly Pine Stand as Influenced by Fertilization and Irrigation
D.A. Sampson; H. Lee Allen
1998-01-01
We examined empirical and simulated estimates of canopy light attenuation at SETRES (Southeast Tree Research and Education Site) a 2x2 factorial study of water and nutrients. Fertilized plots had signiticantly lower under-canopy PAR transmittance (Tc) when compared to non-fertilized plots. Light interception efftciency as measured by the...
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Kinoshita, Takafumi; Yano, Takayoshi; Sugiura, Makoto; Nagasaki, Yuji
2014-01-01
To further development of a simplified fertigation system using controlled-release fertilizers (CRF), we investigated the effects of differing levels of fertilizers and plant density on leaf area index (LAI), fruit yields, and nutrient use in soilless tomato cultures with low node-order pinching and high plant density during spring-summer (SS), summer-fall (SF), and fall-winter (FW) seasons. Plants were treated with 1 of 3 levels of CRF in a closed system, or with liquid fertilizer (LF) with constant electrical conductivity (EC) in a drip-draining system. Two plant densities were examined for each fertilizer treatment. In CRF treatments, LAI at pinching increased linearly with increasing nutrient supply for all cropping seasons. In SS, both light interception by plant canopy at pinching and total marketable fruit yield increased linearly with increasing LAI up to 6 m2·m−2; the maximization point was not reached for any of the treatments. In FW, both light interception and yield were maximized at an LAI of approximately 4. These results suggest that maximizing the LAI in SS and FW to the saturation point for light interception is important for increasing yield. In SF, however, the yield maximized at an LAI of approximately 3, although the light interception linearly increased with increasing LAI, up to 4.5. According to our results, the optimal LAI at pinching may be 6 in SS, 3 in SF, and 4 in FW. In comparing LAI values with similar fruit yield, we found that nutrient supply was 32−46% lower with the CRF method than with LF. In conclusion, CRF application in a closed system enables growers to achieve a desirable LAI to maximize fruit yield with a regulated amount of nutrient supply per unit area. Further, the CRF method greatly reduced nutrient use without decreasing fruit yield at similar LAIs, as compared to the LF method. PMID:25402478
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Buller, David B.; Andersen, Peter A.; Walkosz, Barbara J.; Scott, Michael D.; Beck, Larry; Cutter, Gary R.
2016-01-01
Introduction Exposure to solar ultraviolet radiation during recreation is a risk factor for skin cancer. A trial evaluating an intervention to promote advanced sun protection (sunscreen pre-application/reapplication; protective hats and clothing; use of shade) during vacations. Materials and Methods Adult visitors to hotels/resorts with outdoor recreation (i.e., vacationers) participated in a group-randomized pretest-posttest controlled quasi-experimental design in 2012–14. Hotels/resorts were pair-matched and randomly assigned to the intervention or untreated control group. Sun protection (e.g., clothing, hats, shade and sunscreen) was measured in cross-sectional samples by observation and a face-to-face intercept survey during two-day visits. Results Initially, 41 hotel/resorts (11%) participated but 4 dropped out before posttest. Hotel/resorts were diverse (employees=30 to 900; latitude=24o 78′ N to 50o 52′ N; elevation=2 ft. to 9,726 ft. above sea level), and had a variety of outdoor venues (beaches/pools, court/lawn games, golf courses, common areas, and chairlifts). At pretest, 4,347 vacationers were observed and 3,531 surveyed. More females were surveyed (61%) than observed (50%). Vacationers were mostly 35–60 years old, highly educated (college education = 68%) and non-Hispanic white (93%), with high-risk skin types (22%). Vacationers reported covering 60% of their skin with clothing. Also, 40% of vacationers used shade; 60% applied sunscreen; and 42% had been sunburned. Conclusions The trial faced challenges recruiting resorts but result show that the large, multi-state sample of vacationers were at high risk for solar UV exposure. PMID:26593781
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Kotilainen, Titta; Robson, T Matthew; Hernández, Ricardo
2018-01-01
Climate screens are typically used inside glass greenhouses to improve control of humidity and temperature, and thus reduce energy expenditure. Shade nets are more appropriate to use, either with or without polyethylene cladding, at locations less-reliant on climate control, but where protection against hail, wind and excessive solar radiation might be needed. In addition, insect screens and nets can be employed to hinder insect pests and other invertebrates entering either type of production environment, and to keep invertebrates used in pest management contained inside. Screens and nets both transmit sunlight in a wavelength-specific manner, giving them the potential to affect plant morphology and physiology. Screens and nets of various colours and nominal shading factors have been described and studied; however, detailed measurements of their spectral characteristics are scarce. We measured solar spectral photon-irradiance and its attenuation by climate screens, shade nets, insect nets, greenhouse glass, and polyethylene covers. Our aim was to elucidate the effects of different patterns, colours, and shading factors, on light quality in production environments. Our measurements reveal that there are large differences both in the fraction of global irradiance attenuated and spectral ratios received under materials that are otherwise superficially similar in terms of their appearance and texture. We suggest that the type of spectral characterization that we performed is required to fully interpret the results of research examining plant responses to different types of screen and net. These data on spectral irradiance would benefit material manufacturers, researchers, growers, and horticultural consultants, enabling material selection to better match the solutions sought by growers and their desired outcomes regarding plant performance.
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Mapping Time-to-Contact and Time-to-Peak Effector Velocity in Interceptive Striking Tasks
ERIC Educational Resources Information Center
Rothenberg-Cunningham, Alek; Newell, Karl M.
2015-01-01
Purpose: This study investigated perception and action coupling as reflected in a mapping between time-to-contact (TTC) and time-to-peak-velocity (TPV) for children and youths aged 7 to 8, 11 to 12, and 15 to 16 years old and adults aged 19 to 20 years old performing a task that allowed the participants to self-select the interception position in…
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Zhu, Dan H; Wang, Ping; Zhang, Wei Z; Yuan, Yue; Li, Bin; Wang, Jiang
2015-01-01
Although plant diversity is postulated to resist invasion, studies have not provided consistent results, most of which were ascribed to the influences of other covariate environmental factors. To explore the mechanisms by which plant diversity influences community invasibility, an experiment was conducted involving grassland sites varying in their species richness (one, two, four, eight, and sixteen species). Light interception efficiency and soil resources (total N, total P, and water content) were measured. The number of species, biomass, and the number of seedlings of the invading species decreased significantly with species richness. The presence of Patrinia scabiosaefolia Fisch. ex Trev. and Mosla dianthera (Buch.-Ham. ex Roxburgh) Maxim. significantly increased the resistance of the communities to invasion. A structural equation model showed that the richness of planted species had no direct and significant effect on invasion. Light interception efficiency had a negative effect on the invasion whereas soil water content had a positive effect. In monocultures, Antenoron filiforme (Thunb.) Rob. et Vaut. showed the highest light interception efficiency and P. scabiosaefolia recorded the lowest soil water content. With increased planted-species richness, a greater percentage of pots showed light use efficiency higher than that of A. filiforme and a lower soil water content than that in P. scabiosaefolia. The results of this study suggest that plant diversity confers resistance to invasion, which is mainly ascribed to the sampling effect of particular species and the complementarity effect among species on resources use.
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Underway sensing of radiometric properties utilizing a novel sub-hull installation on R/V SONNE
NASA Astrophysics Data System (ADS)
Zielinski, O.; Rüssmeier, N.; Garaba, S. P.; Voss, D.
2016-12-01
Understanding light interaction with biogeochemical constituents in the marine environment has improved in the last few years due to small, fast, automated and affordable optical tools. Ocean color observations are dependent on ambient sunlight, wind speed influencing sea surface reflected glint, instrument self shading, sensor accuracy, sensitivity as well as spatial and spectral resolution influencing our abilities in sensing oceanic processes. In this study we present a new method useful in collecting radiometric information, namely upwelling radiance from a platform submerged in a novel hydrographic sub-hull of a research vessel. The information analyzed here was obtained during a recent field campaign in the Northwestern European shelf seas aboard the new German research vessel SONNE. A comparison of the measurements from this approach with a free falling hyperspectral profiler was conducted to determine the degree of uncertainty that results from ship shadow. We observed intensity deviations in a range of about 30% compared to profiling measurements, which can be attributed to instrument shading and environmental perturbations. A form-fitting algorithm was adapted to receive corresponding depths with identical spectral shape indicating an equivalent light path of 22 m for the sub-hull installation. Remote sensing reflectance was then calculated by normalizing the upwelling radiance with the downward solar irradiance. During an east to west transect in the North Sea we successfully applied the above method while cruising at a maximum speed up of 12 knots, resolving the mixing zone of CDOM (colored dissolved organic matter) dominant Baltic waters towards the open North Sea.
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Louarn, Gaëtan; Lecoeur, Jérémie; Lebon, Eric
2008-01-01
Background and Aims In grapevine, canopy-structure-related variations in light interception and distribution affect productivity, yield and the quality of the harvested product. A simple statistical model for reconstructing three-dimensional (3D) canopy structures for various cultivar–training system (C × T) pairs has been implemented with special attention paid to balance the time required for model parameterization and accuracy of the representations from organ to stand scales. Such an approach particularly aims at overcoming the weak integration of interplant variability using the usual direct 3D measurement methods. Model This model is original in combining a turbid-medium-like envelope enclosing the volume occupied by vine shoots with the use of discrete geometric polygons representing leaves randomly located within this volume to represent plant structure. Reconstruction rules were adapted to capture the main determinants of grapevine shoot architecture and their variability. Using a simplified set of parameters, it was possible to describe (1) the 3D path of the main shoot, (2) the volume occupied by the foliage around this path and (3) the orientation of individual leaf surfaces. Model parameterization (estimation of the probability distribution for each parameter) was carried out for eight contrasting C × T pairs. Key Results and Conclusions The parameter values obtained in each situation were consistent with our knowledge of grapevine architecture. Quantitative assessments for the generated virtual scenes were carried out at the canopy and plant scales. Light interception efficiency and local variations of light transmittance within and between experimental plots were correctly simulated for all canopies studied. The approach predicted these key ecophysiological variables significantly more accurately than the classical complete digitization method with a limited number of plants. In addition, this model accurately reproduced the characteristics of a wide range of individual digitized plants. Simulated leaf area density and the distribution of light interception among leaves were consistent with measurements. However, at the level of individual organs, the model tended to underestimate light interception. PMID:18202006
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Moeller, Carina; Evers, Jochem B; Rebetzke, Greg
2014-01-01
Tillering is a core constituent of plant architecture, and influences light interception to affect plant and crop performance. Near-isogenic lines (NILs) varying for a tiller inhibition (tin) gene and representing two genetic backgrounds were investigated for tillering dynamics, organ size distribution, leaf area, light interception, red: far-red ratio, and chlorophyll content. Tillering ceased earlier in the tin lines to reduce the frequencies of later primary and secondary tillers compared to the free-tillering NILs, and demonstrated the genetically lower tillering plasticity of tin-containing lines. The distribution of organ sizes along shoots varied between NILs contrasting for tin. Internode elongation commenced at a lower phytomer, and the peduncle was shorter in the tin lines. The flag leaves of tin lines were larger, and the longest leaf blades were observed at higher phytomers in the tin than in free-tillering lines. Total leaf area was reduced in tin lines, and non-tin lines invested more leaf area at mid-canopy height. The tiller economy (ratio of seed-bearing shoots to numbers of shoots produced) was 10% greater in the tin lines (0.73-0.76) compared to the free-tillering sisters (0.62-0.63). At maximum tiller number, the red: far-red ratio (light quality stimulus that is thought to induce the cessation of tillering) at the plant-base was 0.18-0.22 in tin lines and 0.09-0.11 in free-tillering lines at levels of photosynthetic active radiation of 49-53% and 30-33%, respectively. The tin lines intercepted less radiation compared to their free-tillering sisters once genotypic differences in tiller numbers had established, and maintained green leaf area in the lower canopy later into the season. Greater light extinction coefficients (k) in tin lines prior to, but reduced k after, spike emergence indicated that differences in light interception between NILs contrasting in tin cannot be explained by leaf area alone but that geometric and optical canopy properties contributed. The careful characterization of specifically-developed NILs is refining the development of a physiology-based model for tillering to improve understanding of the value of architectural traits for use in cereal improvement.
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Effects of pathogen reduction systems on platelet microRNAs, mRNAs, activation, and function
Osman, Abdimajid; Hitzler, Walter E.; Meyer, Claudius U.; Landry, Patricia; Corduan, Aurélie; Laffont, Benoit; Boilard, Eric; Hellstern, Peter; Vamvakas, Eleftherios C.
2015-01-01
Pathogen reduction (PR) systems for platelets, based on chemically induced cross-linking and inactivation of nucleic acids, potentially prevent transfusion transmission of infectious agents, but can increase clinically significant bleeding in some clinical studies. Here, we documented the effects of PR systems on microRNA and mRNA levels of platelets stored in the blood bank, and assessed their impact on platelet activation and function. Unlike platelets subjected to gamma irradiation or stored in additive solution, platelets treated with Intercept (amotosalen + ultraviolet-A [UVA] light) exhibited significantly reduced levels of 6 of the 11 microRNAs, and 2 of the 3 anti-apoptotic mRNAs (Bcl-xl and Clusterin) that we monitored, compared with platelets stored in plasma. Mirasol (riboflavin + UVB light) treatment of platelets did not produce these effects. PR neither affected platelet microRNA synthesis or function nor induced cross-linking of microRNA-sized endogenous platelet RNA species. However, the reduction in the platelet microRNA levels induced by Intercept correlated with the platelet activation (p < 0.05) and an impaired platelet aggregation response to ADP (p < 0.05). These results suggest that Intercept treatment may induce platelet activation, resulting in the release of microRNAs and mRNAs from platelets. The clinical implications of this reduction in platelet nucleic acids secondary to Intercept remain to be established. PMID:24749844
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Ding, Zhaojun; Galván-Ampudia, Carlos S; Demarsy, Emilie; Łangowski, Łukasz; Kleine-Vehn, Jürgen; Fan, Yuanwei; Morita, Miyo T; Tasaka, Masao; Fankhauser, Christian; Offringa, Remko; Friml, Jiří
2011-04-01
Phototropism is an adaptation response, through which plants grow towards the light. It involves light perception and asymmetric distribution of the plant hormone auxin. Here we identify a crucial part of the mechanism for phototropism, revealing how light perception initiates auxin redistribution that leads to directional growth. We show that light polarizes the cellular localization of the auxin efflux carrier PIN3 in hypocotyl endodermis cells, resulting in changes in auxin distribution and differential growth. In the dark, high expression and activity of the PINOID (PID) kinase correlates with apolar targeting of PIN3 to all cell sides. Following illumination, light represses PINOID transcription and PIN3 is polarized specifically to the inner cell sides by GNOM ARF GTPase GEF (guanine nucleotide exchange factor)-dependent trafficking. Thus, differential trafficking at the shaded and illuminated hypocotyl side aligns PIN3 polarity with the light direction, and presumably redirects auxin flow towards the shaded side, where auxin promotes growth, causing hypocotyls to bend towards the light. Our results imply that PID phosphorylation-dependent recruitment of PIN proteins into distinct trafficking pathways is a mechanism to polarize auxin fluxes in response to different environmental and endogenous cues. © 2011 Macmillan Publishers Limited. All rights reserved
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Pons, Thijs L.; Poorter, Hendrik
2014-01-01
The carbon balance is defined here as the partitioning of daily whole-plant gross CO2 assimilation (A) in C available for growth and C required for respiration (R). A scales positively with growth irradiance and there is evidence for an irradiance dependence of R as well. Here we ask if R as a fraction of A is also irradiance dependent, whether there are systematic differences in C-balance between shade-tolerant and shade-intolerant species, and what the causes could be. Growth, gas exchange, chemical composition and leaf structure were analyzed for two shade-tolerant and three shade-intolerant herbaceous species that were hydroponically grown in a growth room at five irradiances from 20 μmol m−2 s−1 (1.2 mol m−2 day−1) to 500 μmol m−2 s−1 (30 mol m−2 day−1). Growth analysis showed little difference between species in unit leaf rate (dry mass increase per unit leaf area) at low irradiance, but lower rates for the shade-tolerant species at high irradiance, mainly as a result of their lower light-saturated rate of photosynthesis. This resulted in lower relative growth rates in these conditions. Daily whole-plant R scaled with A in a very tight manner, giving a remarkably constant R/A ratio of around 0.3 for all but the lowest irradiance. Although some shade-intolerant species showed tendencies toward a higher R/A and inefficiencies in terms of carbon and nitrogen investment in their leaves, no conclusive evidence was found for systematic differences in C-balance between the shade-tolerant and intolerant species at the lowest irradiance. Leaf tissue of the shade-tolerant species was characterized by high dry matter percentages, C-concentration and construction costs, which could be associated with a better defense in shade environments where leaf longevity matters. We conclude that shade-intolerant species have a competitive advantage at high irradiance due to superior potential growth rates, but that shade-tolerance is not necessarily associated with a better C-balance at low irradiance. Under those conditions tolerance to other stresses is probably more important for the performance of shade-tolerant species. PMID:24550922
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Díaz-Barradas, M C; Zunzunegui, M; Alvarez-Cansino, L; Esquivias, M P; Valera, J; Rodríguez, H
2018-03-01
Under natural conditions, light exposure for Mediterranean shrubs can be highly variable, especially during cloudy days or under a canopy, and can interfere with other environmental factors such as temperature and water availability. With the aim of decoupling the effect of radiation and temperature from water availability, we conducted an experiment where two perennial and three summer semi-deciduous shrub species were subjected to different levels of irradiation. In order to follow plant responses to light exposure, we measured gas exchange, photosystem II photochemical efficiency, photosynthetic pigments and leaf mass area in spring and summer. Results showed that all study species presented a plastic response to different light conditions, and that light-related traits varied in a coordinated manner. Summer semi-deciduous species exhibited a more opportunistic response, with higher photosynthesis rates in full sun, but under shade conditions, the two strategies presented similar assimilation rates. Stomatal conductance did not show such a drastic response as photosynthetsis, being related to changes in WUE. Daily cycles of F v /F m revealed a slight photoinhibitory response during summer, mainly in perennial species. In all cases photosynthetic pigments adjusted to the radiation level; leaves had lower chlorophyll content, higher pool of xanthophylls and higher proportion of the de-epoxydaded state of xanthophylls under sun conditions. Lutein content increased in relation to the xanthophyll pool under shade conditions. Our results evidenced that radiation is an important driving factor controlling morphological and physiological status of Mediterranean shrub species, independently of water availability. Summer semi-deciduous species exhibit a set of traits with higher response variability, maximising their photosynthetic assimilation under different sun conditions. © 2017 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.
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Tree seedlings respond to both light and soil nutrients in a Patagonian evergreen-deciduous forest.
Promis, Alvaro; Allen, Robert B
2017-01-01
Seedlings of co-occurring species vary in their response to resource availability and this has implications for the conservation and management of forests. Differential shade-tolerance is thought to influence seedling performance in mixed Nothofagus betuloides-Nothofagus pumilio forests of Patagonia. However, these species also vary in their soil nutrient requirements. To determine the effects of light and soil nutrient resources on small seedlings we examined responses to an experimental reduction in canopy tree root competition through root trenching and restricting soil nutrient depletion through the addition of fertilizer. To understand the effect of light these treatments were undertaken in small canopy gaps and nearby beneath undisturbed canopy with lower light levels. Seedling diameter growth was greater for N. pumilio and height growth was greater for N. betuloides. Overall, diameter and height growth were greater in canopy gaps than beneath undisturbed canopy. Such growths were also greater with fertilizer and root trenching treatments, even beneath undisturbed canopy. Seedling survival was lower under such treatments, potentially reflecting thinning facilitated by resource induced growth. Finally, above-ground biomass did not vary among species although the less shade tolerant N. pumilio had higher below-ground biomass and root to shoot biomass ratio than the more shade tolerant N. betuloides. Above- and below-ground biomass were higher in canopy gaps so that the root to shoot biomass ratio was similar to that beneath undisturbed canopy. Above-ground biomass was also higher with fertilizer and root trenching treatments and that lowered the root to shoot biomass ratio. Restricting soil nutrient depletion allowed seedlings of both species to focus their responses above-ground. Our results support a view that soil nutrient resources, as well as the more commonly studied light resources, are important to seedlings of Nothofagus species occurring on infertile soils.
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Reinen, Emilie; Anten, Niels P. R.
2017-01-01
Vegetation stands have a heterogeneous distribution of light quality, including the red/far-red light ratio (R/FR) that informs plants about proximity of neighbors. Adequate responses to changes in R/FR are important for competitive success. How the detection and response to R/FR are spatially linked and how this spatial coordination between detection and response affects plant performance remains unresolved. We show in Arabidopsis thaliana and Brassica nigra that localized FR enrichment at the lamina tip induces upward leaf movement (hyponasty) from the petiole base. Using a combination of organ-level transcriptome analysis, molecular reporters, and physiology, we show that PIF-dependent spatial auxin dynamics are key to this remote response to localized FR enrichment. Using computational 3D modeling, we show that remote signaling of R/FR for hyponasty has an adaptive advantage over local signaling in the petiole, because it optimizes the timing of leaf movement in response to neighbors and prevents hyponasty caused by self-shading. PMID:28652357
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Effects of shade on welfare and meat quality of grazing sheep under high ambient temperature.
Liu, H W; Cao, Y; Zhou, D W
2012-12-01
This study was conducted to evaluate the effects of providing shade on growth performance, welfare, and meat quality of grazing sheep under high ambient temperature. A total of 120 healthy male Ujumqin wool sheep (a local breed; BW = 18.7 ± 1.27 kg; 14 wk old) were randomly and equally divided into shaded and unshaded treatments with 3 pens per treatment. Sheep were grazed on an unshaded pastureland from 0600 to 1000 h and 1400 to 1800 h. During other times, sheep were confined in shaded or unshaded pens. Body weight was recorded on d 1 and 42 of the experiment. Rectal temperature and respiration rate were recorded on d 7, 14, 21, 28, 35, and 42. At end of the trial, sheep were blood sampled and slaughtered to collect meat samples. Respiration rate was greater (P < 0.05) in the unshaded sheep than shaded sheep on d 14, 21, 28, 35, and 42 of the trial whereas no significant differences were found on d 7. Moreover, no differences were observed in final BW, ADG, or rectal temperature throughout the trial. The pH at 24 h postmortem (pH(24)) and cooking loss were greater (P < 0.01) in unshaded than shaded sheep. On the contrary, lightness (L*), redness (a*) and yellowness (b*) values at 24 h postmortem were lower (P < 0.05) in unshaded versus shaded sheep. The sheep in the unshaded group had a greater (P < 0.05) cortisol concentration compared with the shaded group. Sheep in the shaded group had lower creatine kinase activity (P < 0.01) as well as observed for glucose (P < 0.05), triiodothyronine (P < 0.01), and thyroxine (P < 0.05) concentrations and white blood cell count (P < 0.05). Compared with the unshaded group, sheep in the shaded group had a greater lymphocytes (LYM) count (P < 0.05). In contrast, the opposite was true for neutrophils (NEU) count (P < 0.01) and NEU:LYM ratio (P < 0.01). In conclusion, the shade cloth, although not enhancing ADG, improved meat quality traits and certain stress parameters in grazing sheep reared under high ambient temperature.
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Atlan, Anne; Hornoy, Benjamin; Delerue, Florian; Gonzalez, Maya; Pierre, Jean-Sébastien; Tarayre, Michèle
2015-01-01
Phenotypic plasticity may be advantageous for plants to be able to rapidly cope with new and changing environments associated with climate change or during biological invasions. This is especially true for perennial plants, as they may need a longer period to respond genetically to selective pressures than annuals, and also because they are more likely to experience environmental changes during their lifespan. However, few studies have explored the plasticity of the reproductive life history traits of woody perennial species. This study focuses on a woody shrub, Ulex europaeus (common gorse), and on the response of its reproductive traits to one important environmental factor, shading. The study was performed on clones originating from western France (within the native range of this invasive species) and grown for seven years. We compared traits of plants grown in a shade treatment (with two successive shade levels) vs. full natural light. The traits monitored included flowering onset, pod production and seed predation. All traits studied responded to shading, exhibiting various levels of plasticity. In particular, dense shade induced a radical but reversible decrease in flower and pod production, while moderate shade had little effect on reproductive traits. The magnitude of the response to dense shade depended on the genotype, showing a genetically based polymorphism of plasticity. The level of plasticity also showed substantial variations between years, and the effect of environmental variations was cumulative over time. This suggests that plasticity can influence the lifetime fitness of U. Europaeus and is involved in the capacity of the species to grow under contrasting environmental conditions.
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Atlan, Anne; Hornoy, Benjamin; Delerue, Florian; Gonzalez, Maya; Pierre, Jean-Sébastien; Tarayre, Michèle
2015-01-01
Phenotypic plasticity may be advantageous for plants to be able to rapidly cope with new and changing environments associated with climate change or during biological invasions. This is especially true for perennial plants, as they may need a longer period to respond genetically to selective pressures than annuals, and also because they are more likely to experience environmental changes during their lifespan. However, few studies have explored the plasticity of the reproductive life history traits of woody perennial species. This study focuses on a woody shrub, Ulex europaeus (common gorse), and on the response of its reproductive traits to one important environmental factor, shading. The study was performed on clones originating from western France (within the native range of this invasive species) and grown for seven years. We compared traits of plants grown in a shade treatment (with two successive shade levels) vs. full natural light. The traits monitored included flowering onset, pod production and seed predation. All traits studied responded to shading, exhibiting various levels of plasticity. In particular, dense shade induced a radical but reversible decrease in flower and pod production, while moderate shade had little effect on reproductive traits. The magnitude of the response to dense shade depended on the genotype, showing a genetically based polymorphism of plasticity. The level of plasticity also showed substantial variations between years, and the effect of environmental variations was cumulative over time. This suggests that plasticity can influence the lifetime fitness of U. Europaeus and is involved in the capacity of the species to grow under contrasting environmental conditions. PMID:26383627
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Hardman-Mountford, Nick J; Polimene, Luca; Hirata, Takafumi; Brewin, Robert J W; Aiken, Jim
2013-12-06
Geo-engineering proposals to mitigate global warming have focused either on methods of carbon dioxide removal, particularly nutrient fertilization of plant growth, or on cooling the Earth's surface by reducing incoming solar radiation (shading). Marine phytoplankton contribute half the Earth's biological carbon fixation and carbon export in the ocean is modulated by the actions of microbes and grazing communities in recycling nutrients. Both nutrients and light are essential for photosynthesis, so understanding the relative influence of both these geo-engineering approaches on ocean ecosystem production and processes is critical to the evaluation of their effectiveness. In this paper, we investigate the relationship between light and nutrient availability on productivity in a stratified, oligotrophic subtropical ocean ecosystem using a one-dimensional water column model coupled to a multi-plankton ecosystem model, with the goal of elucidating potential impacts of these geo-engineering approaches on ecosystem production. We find that solar shading approaches can redistribute productivity in the water column but do not change total production. Macronutrient enrichment is able to enhance the export of carbon, although heterotrophic recycling reduces the efficiency of carbon export substantially over time. Our results highlight the requirement for a fuller consideration of marine ecosystem interactions and feedbacks, beyond simply the stimulation of surface blooms, in the evaluation of putative geo-engineering approaches.
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Hardman-Mountford, Nick J.; Polimene, Luca; Hirata, Takafumi; Brewin, Robert J. W.; Aiken, Jim
2013-01-01
Geo-engineering proposals to mitigate global warming have focused either on methods of carbon dioxide removal, particularly nutrient fertilization of plant growth, or on cooling the Earth's surface by reducing incoming solar radiation (shading). Marine phytoplankton contribute half the Earth's biological carbon fixation and carbon export in the ocean is modulated by the actions of microbes and grazing communities in recycling nutrients. Both nutrients and light are essential for photosynthesis, so understanding the relative influence of both these geo-engineering approaches on ocean ecosystem production and processes is critical to the evaluation of their effectiveness. In this paper, we investigate the relationship between light and nutrient availability on productivity in a stratified, oligotrophic subtropical ocean ecosystem using a one-dimensional water column model coupled to a multi-plankton ecosystem model, with the goal of elucidating potential impacts of these geo-engineering approaches on ecosystem production. We find that solar shading approaches can redistribute productivity in the water column but do not change total production. Macronutrient enrichment is able to enhance the export of carbon, although heterotrophic recycling reduces the efficiency of carbon export substantially over time. Our results highlight the requirement for a fuller consideration of marine ecosystem interactions and feedbacks, beyond simply the stimulation of surface blooms, in the evaluation of putative geo-engineering approaches. PMID:24132201
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Halford, W Kim; Lizzio, Alf; Wilson, Keithia L; Occhipinti, Stefano
2007-06-01
Relationship self-regulation (SR) is how much partners work at their couple relationship, and it has been hypothesized to predict relationship satisfaction. To test this hypothesis, the authors assessed 191 newlywed couples on SR and relationship satisfaction annually for 5 years. They conducted a multilevel analysis predicting satisfaction with SR as a time-varying covariate. The intercept and slope of relationship satisfaction varied across participants, and the slope showed an average slight decline for both men and women. There was mixed support for the primary hypothesis. SR cross-sectionally and prospectively predicted the intercept, but it did not predict the slope, of relationship satisfaction.
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Yu, Jie; Qiu, Hong; Liu, Xin; Wang, Meiling; Gao, Yongli; Chory, Joanne
2015-01-01
Abstract When sun plants, such as Arabidopsis thaliana, are under canopy shade, elongation of stems/petioles will be induced as one of the most prominent responses. Plant hormones mediate the elongation growth. However, how environmental and hormonal signals are translated into cell expansion activity that leads to the elongation growth remains elusive. Through forward genetic study, we identified shade avoidance2 (sav2) mutant, which contains a P287L mutation in β‐TUBULIN 4. Cortical microtubules (cMTs) play a key role in anisotropic cell growth. Hypocotyls of sav2 are wild type‐like in white light, but are short and highly swollen in shade and dark. We showed that shade not only induces cMT rearrangement, but also affects cMT stability and dynamics of plus ends. Even though auxin and brassinosteroids are required for shade‐induced hypocotyl elongation, they had little effect on shade‐induced rearrangement of cMTs. Blocking auxin transport suppressed dark phenotypes of sav2, while overexpressing EB1b‐GFP, a microtubule plus‐end binding protein, rescued sav2 in both shade and dark, suggesting that tub4P287L represents a unique type of tubulin mutation that does not affect cMT function in supporting cell elongation, but may affect the ability of cMTs to respond properly to growth promoting stimuli. PMID:25899068
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Bollineni, Swetha; Janga, Ravi Kumar; Venugopal, L; Reddy, Indukuri Ravikishore; Babu, P Ravisekhar; Kumar, Sunil S
2014-05-01
The use of self-administered carbamide peroxide bleaching gels has become increasingly popular for whitening of discolored vital teeth. Studies have reported that its use may induce increased levels of sensitivity and surface roughness of the tooth due to demineralization. This study evaluates the effect of fluoride addition to the bleaching agent - its remineralizing capacity and alterations in the whitening properties. Twenty-four extracted lower third molar teeth, with the pretreatment shade determined, were taken up in the study. Each tooth was sectioned into four and labeled as groups A, B, C, and D. The tooth quadrants in group A-C were demineralized; groups A and B were treated with 10% carbamide peroxide gel (group-A without fluoride and group-B with 0.463% fluoride addition) (no further treatment was carried out for group c) group-D remained as the control. The post-treatment shade was determined. The tooth samples were sectioned (approximately 200 μm) for evaluation under a light microscope. The depth of demineralization was analyzed at five different equidistant points. Statistical analysis was carried out with t-tests, accepting ≤0.05 as significant. Addition of fluoride caused remineralization of demineralized enamel. The tooth whitening system showed that the remineralization properties did not affect the whitening properties.
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Wright, Caradee Y; Reddy, Tarylee; Mathee, Angela; Street, Renée A
2017-09-28
Informal workers in African market trade have little formal protection against sun exposure. We aimed to examine sun exposure, sun-related symptoms, and sun protection practices in an informal occupational setting. Trained fieldworkers asked 236 workers in the Warwick Junction market about their workplace, skin and eye sensitivity and skin colour, symptoms faced at work during the summer due to heat, and preventive measures. Data were analyzed using univariate logistic regression to assess the effect of gender and the risk of experiencing symptoms to sun exposure in relation to pre-existing diseases and perception of sun exposure as a hazard. Of the 236 participants, 234 were Black African and 141 (59.7%) were female. Portable shade was the most commonly used form of sun protection (69.9%). Glare from the sun (59.7%) and excessive sweating (57.6%) were commonly reported sun-related health symptoms. The use of protective clothing was more prevalent among those who perceived sun exposure as a hazard ( p = 0.003). In an informal occupational setting, sun exposure was high. Protective clothing and portable shade to eliminate heat and bright light were self-implemented. Action by local authorities to protect informal workers should consider sun exposure to support workers in their efforts to cope in hot weather.
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Kubisch, Petra; Leuschner, Christoph; Coners, Heinz; Gruber, Andreas; Hertel, Dietrich
2017-01-01
Low temperatures are crucial for the formation of the alpine treeline worldwide. Since soil temperature in the shade of tree canopies is lower than in open sites, it was assumed that self-shading may impair the trees’ root growth performance. While experiments with tree saplings demonstrate root growth impairment at soil temperatures below 5–7°C, field studies exploring the soil temperature – root growth relationship at the treeline are missing. We recorded soil temperature and fine root abundance and dynamics in shaded and sun-exposed areas under canopies of isolated Pinus cembra trees at the alpine treeline. In contrast to the mentioned assumption, we found more fine root biomass and higher fine root growth in colder than in warmer soil areas. Moreover, colder areas showed higher fine root turnover and thus lower root lifespan than warmer places. We conclude that P. cembra balances enhanced fine root mortality in cold soils with higher fine root activity and by maintaining higher fine root biomass, most likely as a response to shortage in soil resource supply. The results from our study highlight the importance of in situ measurements on mature trees to understand the fine root response and carbon allocation pattern to the thermal growth conditions at the alpine treeline. PMID:28469633
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Star sensor/mapper with a self deployable, high-attenuation light shade for SAS-B
NASA Technical Reports Server (NTRS)
Schenkel, F. W.; Finkel, A.
1972-01-01
A star sensor/mapper to determine positional data for the small astronomy satellites was tested to detect stars of plus 4 visual magnitude. It utilizes two information channels with memory so that it can be used with a low-data-rate telemetry system. One channel yields star amplitude information; the other yields the time of star occurrence as the star passes across an N-slit reticle/photomultiplier detector system. Some of the features of the star sensor/mapper are its low weight of 6.5 pounds, low power consumption of 0.4 watt, bandwidth switching to match the satellite spin rate, optical equalization of sensitivity over the 5-by-10 deg field of view, and self-deployable sunshade. The attitude determination accuracy is 3 arc minutes. This is determined by such parameters as the reticle configuration, optical train, and telemetry readout. The optical and electronic design of the star sensor/mapper, its expansion capabilities, and its features are discussed.
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Regional climate modulates the canopy mosaic of favourable and risky microclimates for insects.
Pincebourde, Sylvain; Sinoquet, Herve; Combes, Didier; Casas, Jerome
2007-05-01
1. One major gap in our ability to predict the impacts of climate change is a quantitative analysis of temperatures experienced by organisms under natural conditions. We developed a framework to describe and quantify the impacts of local climate on the mosaic of microclimates and physiological states of insects within tree canopies. This approach was applied to a leaf mining moth feeding on apple leaf tissues. 2. Canopy geometry was explicitly considered by mapping the 3D position and orientation of more than 26 000 leaves in an apple tree. Four published models for canopy radiation interception, energy budget of leaves and mines, body temperature and developmental rate of the leaf miner were integrated. Model predictions were compared with actual microclimate temperatures. The biophysical model accurately predicted temperature within mines at different positions within the tree crown. 3. Field temperature measurements indicated that leaf and mine temperature patterns differ according to the regional climatic conditions (cloudy or sunny) and depending on their location within the canopy. Mines in the sun can be warmer than those in the shade by several degrees and the heterogeneity of mine temperature was incremented by 120%, compared with that of leaf temperature. 4. The integrated model was used to explore the impact of both warm and exceptionally hot climatic conditions recorded during a heat wave on the microclimate heterogeneity at canopy scale. During warm conditions, larvae in sunlight-exposed mines experienced nearly optimal growth conditions compared with those within shaded mines. The developmental rate was increased by almost 50% in the sunny microhabitat compared with the shaded location. Larvae, however, experienced optimal temperatures for their development inside shaded mines during extreme climatic conditions, whereas larvae in exposed mines were overheating, leading to major risks of mortality. 5. Tree canopies act as both magnifiers and reducers of the climatic regime experienced in open air outside canopies. Favourable and risky spots within the canopy do change as a function of the climatic conditions at the regional scale. The shifting nature of the mosaic of suitable and risky habitats may explain the observed uniform distribution of leaf miners within tree canopies.
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Marginal and Random Intercepts Models for Longitudinal Binary Data With Examples From Criminology.
Long, Jeffrey D; Loeber, Rolf; Farrington, David P
2009-01-01
Two models for the analysis of longitudinal binary data are discussed: the marginal model and the random intercepts model. In contrast to the linear mixed model (LMM), the two models for binary data are not subsumed under a single hierarchical model. The marginal model provides group-level information whereas the random intercepts model provides individual-level information including information about heterogeneity of growth. It is shown how a type of numerical averaging can be used with the random intercepts model to obtain group-level information, thus approximating individual and marginal aspects of the LMM. The types of inferences associated with each model are illustrated with longitudinal criminal offending data based on N = 506 males followed over a 22-year period. Violent offending indexed by official records and self-report were analyzed, with the marginal model estimated using generalized estimating equations and the random intercepts model estimated using maximum likelihood. The results show that the numerical averaging based on the random intercepts can produce prediction curves almost identical to those obtained directly from the marginal model parameter estimates. The results provide a basis for contrasting the models and the estimation procedures and key features are discussed to aid in selecting a method for empirical analysis.
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Kubásek, Jiří; Urban, Otmar; Šantrůček, Jiří
2013-12-01
Plants in the field are commonly exposed to fluctuating light intensity, caused by variable cloud cover, self-shading of leaves in the canopy and/or leaf movement due to turbulence. In contrast to C3 plant species, only little is known about the effects of dynamic light (DL) on photosynthesis and growth in C4 plants. Two C4 and two C3 monocot and eudicot species were grown under steady light or DL conditions with equal sum of daily incident photon flux. We measured leaf gas exchange, plant growth and dry matter carbon isotope discrimination to infer CO2 bundle sheath leakiness in C4 plants. The growth of all species was reduced by DL, despite only small changes in steady-state gas exchange characteristics, and this effect was more pronounced in C4 than C3 species due to lower assimilation at light transitions. This was partially attributed to increased bundle sheath leakiness in C4 plants under the simulated lightfleck conditions. We hypothesize that DL leads to imbalances in the coordination of C4 and C3 cycles and increasing leakiness, thereby decreasing the quantum efficiency of photosynthesis. In addition to their other constraints, the inability of C4 plants to efficiently utilize fluctuating light likely contributes to their absence in such environments as forest understoreys. © 2013 Scandinavian Plant Physiology Society.
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USDA-ARS?s Scientific Manuscript database
Weed interference with crop growth is often attributed to water, nutrient, or light competition; however, specific physiological responses to these stresses are not well described. This study’s objective was to compare growth, yield, and gene expression responses of corn to nitrogen (N), low light (...
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Adaptive Criterion Setting in Perceptual Decision Making
ERIC Educational Resources Information Center
Stuttgen, Maik C.; Yildiz, Ali; Gunturkun, Onur
2011-01-01
Pigeons responded in a perceptual categorization task with six different stimuli (shades of gray), three of which were to be classified as "light" or "dark", respectively. Reinforcement probability for correct responses was varied from 0.2 to 0.6 across blocks of sessions and was unequal for correct light and dark responses. Introduction of a new…
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Longitudinal Change of Self-Perceptions of Aging and Mortality
2014-01-01
Objective. To understand the association between self-perceptions of aging (SPA) and mortality in late life. Method. The sample (n = 1,507) was drawn from the Australian Longitudinal Study of Aging (baseline age = 65–103 years). We used joint growth curve and survival models on 5 waves of data for a period of 16 years to investigate the random intercept and slope of SPA for predicting all-cause mortality. Results. The unadjusted model revealed that poor SPA at baseline, as well as decline in SPA, increased the risk of mortality (SPA intercept hazard ratio [HR] = 1.21, 95% confidence interval [CI] = 1.13, 1.31; SPA slope HR = 1.17, 95% CI = 1.02, 1.33). This relationship remained significant for the SPA intercept after adjusting for other risk factors including demographics, physical health, cognitive functioning, and well-being. Conclusion. These findings suggest that a single measurement of SPA in late life may be very informative of future long-term vulnerability to health decline and mortality. Furthermore, a dynamic measure of SPA may be indicative of adaptation to age-related changes. This supports a “self-fulfilling” hypothesis, whereby SPA is a lens through which age-related changes are interpreted, and these interpretations can affect future health and health behaviors. PMID:23419867
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Light accelerates plant responses to warming.
De Frenne, Pieter; Rodríguez-Sánchez, Francisco; De Schrijver, An; Coomes, David A; Hermy, Martin; Vangansbeke, Pieter; Verheyen, Kris
2015-08-17
Competition for light has profound effects on plant performance in virtually all terrestrial ecosystems. Nowhere is this more evident than in forests, where trees create environmental heterogeneity that shapes the dynamics of forest-floor communities(1-3). Observational evidence suggests that biotic responses to both anthropogenic global warming and nitrogen pollution may be attenuated by the shading effects of trees and shrubs(4-9). Here we show experimentally that tree shade is slowing down changes in below-canopy communities due to warming. We manipulated levels of photosynthetically active radiation, temperature and nitrogen, alone and in combination, in a temperate forest understorey over a 3-year period, and monitored the composition of the understorey community. Light addition, but not nitrogen enrichment, accelerated directional plant community responses to warming, increasing the dominance of warmth-preferring taxa over cold-tolerant plants (a process described as thermophilization(6,10-12)). Tall, competitive plants took greatest advantage of the combination of elevated temperature and light. Warming of the forest floor did not result in strong community thermophilization unless light was also increased. Our findings suggest that the maintenance of locally closed canopy conditions could reduce, at least temporarily, warming-induced changes in forest floor plant communities.
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Field, Katie J; George, Rachel; Fearn, Brian; Quick, W Paul; Davey, Matthew P
2013-01-01
"Living stones" (Lithops spp.) display some of the most extreme morphological and physiological adaptations in the plant kingdom to tolerate the xeric environments in which they grow. The physiological mechanisms that optimise the photosynthetic processes of Lithops spp. while minimising transpirational water loss in both above- and below-ground tissues remain unclear. Our experiments have shown unique simultaneous high-light and shade-tolerant adaptations within individual leaves of Lithops aucampiae. Leaf windows on the upper surfaces of the plant allow sunlight to penetrate to photosynthetic tissues within while sunlight-blocking flavonoid accumulation limits incoming solar radiation and aids screening of harmful UV radiation. Increased concentration of chlorophyll a and greater chlorophyll a:b in above-ground regions of leaves enable maximum photosynthetic use of incoming light, while inverted conical epidermal cells, increased chlorophyll b, and reduced chlorophyll a:b ensure maximum absorption and use of low light levels within the below-ground region of the leaf. High NPQ capacity affords physiological flexibility under variable natural light conditions. Our findings demonstrate unprecedented physiological flexibility in a xerophyte and further our understanding of plant responses and adaptations to extreme environments.
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Lonigan, Christopher J.; Allan, Darcey M.; Phillips, Beth M.
2016-01-01
There is strong evidence that self-regulatory processes are linked to early academic skills both concurrently and longitudinally. The majority of extant longitudinal studies, however, have been conducted using autoregressive techniques that may not accurately model change across time. The purpose of this study was to examine the unique associations between two components of self-regulation, attention and executive functioning (EF), and growth in early literacy skills over the preschool year using latent-growth-curve analysis. The sample included 1,082 preschool children (M-age = 55.0 months, SD = 3.73). Children completed measures of vocabulary, syntax, phonological awareness, print knowledge, cognitive ability, and self-regulation, and children’s classroom teachers completed a behavior rating measure. To examine the independent relations of the self-regulatory skills and cognitive ability with children’s initial early literacy skills and growth across the preschool year, growth models in which the intercept and slope were simultaneously regressed on each of the predictor variables were examined. Because of the significant relation between intercept and slope for most outcomes, slope was regressed on intercept in the models to allow a determination of direct and indirect effects of the predictors on growth in children’s language and literacy skills across the preschool year. In general, both teacher-rated inattention and directly measured EF were uniquely associated with initial skills level; however, only teacher-rated inattention uniquely predicted growth in early literacy skills. These findings suggest that teacher-ratings of inattention may measure an aspect of self-regulation that is particularly associated with the acquisition of academic skills in early childhood. PMID:27854463
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Dan Binkley; Jose Luiz Stape; William L. Bauerle; Michael G. Ryan
2010-01-01
The growth of wood in trees and forests depends on the acquisition of resources (light, water, and nutrients), the efficiency of using resources for photosynthesis, and subsequent partitioning to woody tissues. Patterns of efficiency over time for individual trees, or between trees at one time, result from changes in rates photosynthesis and shifts in...
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Use of quantitative light-induced fluorescence to monitor tooth whitening
NASA Astrophysics Data System (ADS)
Amaechi, Bennett T.; Higham, Susan M.
2001-04-01
The changing of tooth shade by whitening agents occurs gradually. Apart from being subjective and affected by the conditions of the surroundings, visual observation cannot detect a very slight change in tooth color. An electronic method, which can communicate the color change quantitatively, would be more reliable. Quantitative Light- induced Fluorescence (QLF) was developed to detect and assess dental caries based on the phenomenon of change of autofluorescence of a tooth by demineralization. However, stains on the tooth surface exhibit the same phenomenon, and therefore QLF can be used to measure the percentage fluorescence change of stained enamel with respect to surrounding unstained enamel. The present study described a technique of assessing the effect of a tooth-whitening agent using QLF. This was demonstrated in two experiments in which either wholly or partially stained teeth were whitened by intermittent immersion in sodium hypochlorite. Following each immersion, the integrated fluorescence change due to the stain was quantified using QLF. In either situation, the value of (Delta) Q decreased linearly as the tooth regained its natural shade. It was concluded that gradual changing of the shade of discolored teeth by a whitening agent could be quantified using QLF.
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Gómez, Iván; Huovinen, Pirjo
2015-01-01
A striking characteristic of endemic Antarctic brown algae is their broad vertical distribution. This feature is largely determined by the shade adaptation in order to cope with the seasonal variation in light availability. However, during spring-summer months, when light penetrates deep in the water column these organisms have to withstand high levels of solar radiation, including UV. In the present study we examine the light use characteristics in parallel to a potential for UV tolerance (measured as content of phenolic compounds, antioxidant activity and maximum quantum yield of fluorescence) in conspecific populations of four Antarctic brown algae (Ascoseira mirabilis, Desmarestia menziesii, D. anceps and Himantothallus grandifolius) distributed over a depth gradient between 5 and 30 m. The main results indicated that a) photosynthetic efficiency was uniform along the depth gradient in all the studied species, and b) short-term (6 h) exposure to UV radiation revealed a high tolerance measured as chlorophyll fluorescence, phlorotannin content and antioxidant capacity. Multivariate analysis of similarity indicated that light requirements for photosynthesis, soluble phlorotannins and antioxidant capacity are the variables determining the responses along the depth gradient in all the studied species. The suite of physiological responses of algae with a shallower distribution (A. mirabilis and D. menziesii) differed from those with deeper vertical range (D. anceps and H. grandifolius). These patterns are consistent with the underwater light penetration that defines two zones: 0–15 m, with influence of UV radiation (1% of UV-B and UV-A at 9 m and 15 m respectively) and a zone below 15 m marked by PAR incidence (1% up to 30 m). These results support the prediction that algae show a UV stress tolerance capacity along a broad depth range according to their marked shade adaptation. The high contents of phlorotannins and antioxidant potential appear to be strongly responsible for the lack of clear depth patterns in light demand characteristics and UV tolerance. PMID:26252953
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Lights Off for Arbuscular Mycorrhiza: On Its Symbiotic Functioning under Light Deprivation
Konvalinková, Tereza; Jansa, Jan
2016-01-01
Plants are often exposed to shade over different time scales and this may substantially affect not only their own growth, but also development and functioning of the energetically dependent organisms. Among those, the root symbionts such as arbuscular mycorrhizal (AM) fungi and rhizobia represent particularly important cases—on the one hand, they consume a significant share of plant carbon (C) budget and, on the other, they generate a number of important nutritional feedbacks on their plant hosts, often resulting in a net positive effect on their host growth and/or fitness. Here we discuss our previous results comparing mycorrhizal performance under different intensities and durations of shade (Konvalinková et al., 2015) in a broader context of previously published literature. Additionally, we review publicly available knowledge on the root colonization and mycorrhizal growth responses in AM plants under light deprivation. Experimental evidence shows that sudden and intensive decrease of light availability to a mycorrhizal plant triggers rapid deactivation of phosphorus transfer from the AM fungus to the plant already within a few days, implying active and rapid response of the AM fungus to the energetic status of its plant host. When AM plants are exposed to intensive shading on longer time scales (weeks to months), positive mycorrhizal growth responses (MGR) are often decreasing and may eventually become negative. This is most likely due to the high C cost of the symbiosis relative to the C availability, and failure of plants to fully compensate for the fungal C demand under low light. Root colonization by AM fungi often declines under low light intensities, although the active role of plants in regulating the extent of root colonization has not yet been unequivocally demonstrated. Quantitative information on the rates and dynamics of C transfer from the plant to the fungus is mostly missing, as is the knowledge on the involved molecular mechanisms. Therefore, these subjects deserve particular attention in the future. PMID:27375642
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Lights Off for Arbuscular Mycorrhiza: On Its Symbiotic Functioning under Light Deprivation.
Konvalinková, Tereza; Jansa, Jan
2016-01-01
Plants are often exposed to shade over different time scales and this may substantially affect not only their own growth, but also development and functioning of the energetically dependent organisms. Among those, the root symbionts such as arbuscular mycorrhizal (AM) fungi and rhizobia represent particularly important cases-on the one hand, they consume a significant share of plant carbon (C) budget and, on the other, they generate a number of important nutritional feedbacks on their plant hosts, often resulting in a net positive effect on their host growth and/or fitness. Here we discuss our previous results comparing mycorrhizal performance under different intensities and durations of shade (Konvalinková et al., 2015) in a broader context of previously published literature. Additionally, we review publicly available knowledge on the root colonization and mycorrhizal growth responses in AM plants under light deprivation. Experimental evidence shows that sudden and intensive decrease of light availability to a mycorrhizal plant triggers rapid deactivation of phosphorus transfer from the AM fungus to the plant already within a few days, implying active and rapid response of the AM fungus to the energetic status of its plant host. When AM plants are exposed to intensive shading on longer time scales (weeks to months), positive mycorrhizal growth responses (MGR) are often decreasing and may eventually become negative. This is most likely due to the high C cost of the symbiosis relative to the C availability, and failure of plants to fully compensate for the fungal C demand under low light. Root colonization by AM fungi often declines under low light intensities, although the active role of plants in regulating the extent of root colonization has not yet been unequivocally demonstrated. Quantitative information on the rates and dynamics of C transfer from the plant to the fungus is mostly missing, as is the knowledge on the involved molecular mechanisms. Therefore, these subjects deserve particular attention in the future.
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Kurt W. Gottschalk
1987-01-01
Northern red oak, black oak, black cherry, and red maple seedlings were grown under light treatments ranging from 8 to 94% of full sunlight for 2 years. Growth was least at the lowest light level and total dry weight increased with increasing light. Total dry-weight rankings (largest to smallest) at all light levels were black cherry, northern red oak, black oak, and...
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Wyka, Tomasz P; Oleksyn, J; Zytkowiak, R; Karolewski, P; Jagodziński, A M; Reich, P B
2012-09-01
Spectra of leaf traits in northern temperate forest canopies reflect major differences in leaf longevity between evergreen conifers and deciduous broadleaf angiosperms, as well as plastic modifications caused by within-crown shading. We investigated (1) whether long-lived conifer leaves exhibit similar intra-canopy plasticity as short-lived broadleaves, and (2) whether global interspecific relationships between photosynthesis, nitrogen, and leaf structure identified for sun leaves adequately describe leaves differentiated in response to light gradients. We studied structural and photosynthetic properties of intra-tree sun and shade foliage in adult trees of seven conifer and four broadleaf angiosperm species in a common garden in Poland. Shade leaves exhibited lower leaf mass-per-area (LMA) than sun leaves; however, the relative difference was smaller in conifers than in broadleaves. In broadleaves, LMA was correlated with lamina thickness and tissue density, while in conifers, it was correlated with thickness but not density. In broadleaves, but not in conifers, reduction of lamina thickness was correlated with a thinner palisade layer. The more conservative adjustment of conifer leaves could result from a combination of phylogenetic constraints, contrasting leaf anatomies and shoot geometries, but also from functional requirements of long-lived foliage. Mass-based nitrogen concentration (N(mass)) was similar between sun and shade leaves, and was lower in conifers than in deciduous broadleaved species. Given this, the smaller LMA in shade corresponded with a lower area-based N concentration (N(area)). In evergreen conifers, LMA and N(area) were less powerful predictors of area-based photosynthetic rate (A (max(area))) in comparison with deciduous broadleaved angiosperms. Multiple regression for sun and shade leaves showed that, in each group, A (max(mass)) was related to N(mass) but not to LMA, whereas LMA became a significant codeterminant of A (max(mass)) in analysis combining both groups. Thus, a fundamental mass-based relationship between photosynthesis, nitrogen, and leaf structure reported previously also exists in a dataset combining within-crown and across-functional type variation.
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York, Paul H.; Gruber, Renee K.; Hill, Ross; Ralph, Peter J.; Booth, David J.; Macreadie, Peter I.
2013-01-01
Understanding how multiple environmental stressors interact to affect seagrass health (measured as morphological and physiological responses) is important for responding to global declines in seagrass populations. We investigated the interactive effects of temperature stress (24, 27, 30 and 32°C) and shading stress (75, 50, 25 and 0% shade treatments) on the seagrass Zostera muelleri over a 3-month period in laboratory mesocosms. Z. muelleri is widely distributed throughout the temperate and tropical waters of south and east coasts of Australia, and is regarded as a regionally significant species. Optimal growth was observed at 27°C, whereas rapid loss of living shoots and leaf mass occurred at 32°C. We found no difference in the concentration of photosynthetic pigments among temperature treatments by the end of the experiment; however, up-regulation of photoprotective pigments was observed at 30°C. Greater levels of shade resulting in high photochemical efficiencies, while elevated irradiance suppressed effective quantum yield (ΔF/FM’). Chlorophyll fluorescence fast induction curves (FIC) revealed that the J step amplitude was significantly higher in the 0% shade treatment after 8 weeks, indicating a closure of PSII reaction centres, which likely contributed to the decline in ΔF/FM’ and photoinhibition under higher irradiance. Effective quantum yield of PSII (ΔF/FM’) declined steadily in 32°C treatments, indicating thermal damage. Higher temperatures (30°C) resulted in reduced above-ground biomass ratio and smaller leaves, while reduced light led to a reduction in leaf and shoot density, above-ground biomass ratio, shoot biomass and an increase in leaf senescence. Surprisingly, light and temperature had few interactive effects on seagrass health, even though these two stressors had strong effects on seagrass health when tested in isolation. In summary, these results demonstrate that populations of Z. muelleri in south-eastern Australia are sensitive to small chronic temperature increases and light decreases that are predicted under future climate change scenarios. PMID:24124551
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Léchaudel, Mathieu; Lopez-Lauri, Félicie; Vidal, Véronique; Sallanon, Huguette; Joas, Jacques
2013-04-15
Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperature and intense light conditions that may lead to metabolic and physiological disorders and affect yield and quality. The present study aimed to determine how mango fruit adapted its functioning in terms of fruit water relations, epicarp characteristics and the antioxidant defence system in peel, to environmental conditions. The effect of contrasted temperature and light conditions was evaluated under natural solar radiation and temperature by comparing well-exposed and shaded fruit at three stages of fruit development. The sun-exposed and shaded peels of the two sides of the well-exposed fruit were also compared. Depending on fruit position within the canopy and on the side of a well-exposed fruit, the temperature gradient over a day affected fruit characteristics such as transpiration, as revealed by the water potential gradient as a function of the treatments, and led to a significant decrease in water conductance for well-exposed fruits compared to fruits within the canopy. Changes in cuticle thickness according to fruit position were consistent with those of fruit water conductance. Osmotic potential was also affected by climatic environment and harvest stage. Environmental conditions that induced water stress and greater light exposure, like on the sunny side of well-exposed fruit, increased the hydrogen peroxide, malondialdehyde and total and reduced ascorbate contents, as well as SOD, APX and MDHAR activities, regardless of the maturity stage. The lowest values were measured in the peel of the shaded fruit, that of the shaded side of well-exposed fruit being intermediate. Mango fruits exposed to water-stress-induced conditions during growth adapt their functioning by reducing their transpiration. Moreover, oxidative stress was limited as a consequence of the increase in antioxidant content and enzyme activities. This adaptive response of mango fruit to its climatic environment during growth could affect postharvest behaviour and quality. Copyright © 2012 Elsevier GmbH. All rights reserved.
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Durey, Kathryn; Santini, Ario; Miletic, Vesna
2008-01-01
The purpose of the present study was to measure the intrapulpal temperature rise occurring during polymerisation of different shades of resin-based composites (RBCs), and two light-emitting diode (LED) units. Seventy non-carious permanent molars, that had been extracted for orthodontic purposes and stored in 2% thymol for not more than four months, were selected. Patient age range was 11-18 years. Standard cavity preparation with standardised remaining dentine thickness and placement of thermocouples (TCs) was prepared using a novel split-tooth technique. Cavities were filled with one of two shades of RBC (A2 and C4, Filtek Z250, 3M ESPE, Seefeld, Germany), and cured with two LED high-intensity units (Elipar Freelight2, 3M ESPE, Seefeld, Germany; Bluephase, Ivoclar Vivadent, Schaan, Liechtenstein) and a conventional halogen light-curing unit (LCU) (Prismetics Lite 2, Dentsply, Weybridge, Surrey, UK) as a control. Pulp temperature rises during bonding [A2 results: H;2.67/0.48:E;5.24/1.32;B;5.99/1.61] were always greater than during RBC curing [A2 results: 2.44/0.63;E3.34/0.70;B3.38/0.60], and these were significant for both LED lights but not for the halogen control, irrespective of shade (Mann-Whitney test: 95% confidence limits). Temperature rises were at times in excess of the values normally quoted as causing irreversible pulp damage. Pulp temperature rises during bonding were higher with the LED lights than with the halogen control. There was no significant difference in temperature rise between the two LED lights when bonding but there was a significant difference between the two LED lights and the halogen control LCUs (Kruskal-Wallis Test: 95% confidence limits). The results support the view that there is a potential risk for heat-induced pulpal injury when light-curing RBCs. The risk is greater during bonding and with high energy, as compared to low-energy output systems. As the extent of tolerable thermal trauma by the pulp tissues is unknown, care and consideration should be given to the choice of LCU and the exposure time when curing RBCs, and especially during bonding.
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Patterns of shading tolerance determined from experimental ...
An extensive review of the experimental literature on seagrass shading evaluated the relationship between experimental light reductions, duration of experiment and seagrass response metrics to determine whether there were consistent statistical patterns. There were highly significant linear relationships of both percent biomass and percent shoot density reduction versus percent light reduction (versus controls), although unexplained variation in the data were high. Duration of exposure affected extent of response for both metrics, but was more clearly a factor in biomass response. Both biomass and shoot density showed linear responses to duration of light reduction for treatments 60%. Unexplained variation was again high, and greater for shoot density than biomass. With few exceptions, regressions of both biomass and shoot density on light reduction for individual species and for genera were statistically significant, but also tended to show high degrees of variability in data. Multivariate regressions that included both percent light reduction and duration of reduction as dependent variables increased the percentage of variation explained in almost every case. Analysis of response data by seagrass life history category (Colonizing, Opportunistic, Persistent) did not yield clearly separate response relationships in most cases. Biomass tended to show somewhat less variation in response to light reduction than shoot density, and of the two, may be the prefe
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Trocha, Lidia K; Weiser, Ewa; Robakowski, Piotr
2016-01-01
Seedlings of forest tree species are exposed to a number of abiotic (organ loss or damage, light shortage) and biotic (interspecific competition) stress factors, which may lead to an inhibition of growth and reproduction and, eventually, to plant death. Growth of the host and its mycorrhizal symbiont is often closely linked, and hence, host damage may negatively affect the symbiont. We designed a pot experiment to study the response of light-demanding Pinus sylvestris and shade-tolerant Fagus sylvatica seedlings to a set of abiotic and biotic stresses and subsequent effects on ectomycorrhizal (ECM) root tip colonization, seedling biomass, and leaf nitrogen content. The light regime had a more pronounced effect on ECM colonization than did juvenile damage. The interspecific competition resulted in higher ECM root tip abundance for Pinus, but this effect was insignificant in Fagus. Low light and interspecific competition resulted in lower seedling biomass compared to high light, and the effect of the latter was partially masked by high light. Leaf nitrogen responded differently in Fagus and Pinus when they grew in interspecific competition. Our results indicated that for both light-demanding (Pinus) and shade-tolerant (Fagus) species, the light environment was a major factor affecting seedling growth and ECM root tip abundance. The light conditions favorable for the growth of seedlings may to some extent compensate for the harmful effects of juvenile organ loss or damage and interspecific competition.
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Coming Closer in Adolescence: Convergence in Mother, Father, and Adolescent Reports of Parenting.
Mastrotheodoros, Stefanos; Van der Graaff, Jolien; Deković, Maja; Meeus, Wim H J; Branje, Susan J T
2018-06-19
Parent-child relationships change during adolescence. Furthermore, parents and adolescents perceive parenting differently. We examined the changes in perceptions of parental practices in fathers, mothers, and adolescents during adolescence. Furthermore, we investigated if fathers', mothers', and adolescents' perceptions converge during adolescence. Following 497 families across six waves (ages 13-18), we investigated the development of parental support and behavioral control using mother and father self-reports, and adolescent reports for mothers and fathers. We found curvilinear decrease for support and control. Parent-adolescent convergence emerged over the 6 years: those with higher intercepts had a steeper decrease, whereas correlations among parent and adolescent reports increased. This multi-informant study sheds light on the development of parent-adolescent convergence on perceptions of parenting. © 2018 Society for Research on Adolescence.
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... support groups and other stop-smoking strategies. Even secondhand smoke can cause further damage. So ask other ... You might take a bath or read a book. Use window shades to block outside light. Ask ...
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USDA-ARS?s Scientific Manuscript database
The current research was directed at determining the impact of light intensity on the architecture, amino acid content and trichome density and characteristics of Tropical Soda Apple (TSA), Solanum viarum (Solanaceae). TSA plants were grown in a greenhouse either covered with a shade cloth (75% bloc...
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USDA-ARS?s Scientific Manuscript database
Light limitation caused by dense vegetation is one of the greatest threats to plant survival in natural environments. Plants detect such neighboring vegetation as a reduction in the red to far-red ratio (R:FR) of the incoming light. The low R:FR signal, perceived by phytochromes, initiates a set of ...
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Development of digital shade guides for color assessment using a digital camera with ring flashes.
Tung, Oi-Hong; Lai, Yu-Lin; Ho, Yi-Ching; Chou, I-Chiang; Lee, Shyh-Yuan
2011-02-01
Digital photographs taken with cameras and ring flashes are commonly used for dental documentation. We hypothesized that different illuminants and camera's white balance setups shall influence color rendering of digital images and affect the effectiveness of color matching using digital images. Fifteen ceramic disks of different shades were fabricated and photographed with a digital camera in both automatic white balance (AWB) and custom white balance (CWB) under either light-emitting diode (LED) or electronic ring flash. The Commission Internationale d'Éclairage L*a*b* parameters of the captured images were derived from Photoshop software and served as digital shade guides. We found significantly high correlation coefficients (r² > 0.96) between the respective spectrophotometer standards and those shade guides generated in CWB setups. Moreover, the accuracy of color matching of another set of ceramic disks using digital shade guides, which was verified by ten operators, improved from 67% in AWB to 93% in CWB under LED illuminants. Probably, because of the inconsistent performance of the flashlight and specular reflection, the digital images captured under electronic ring flash in both white balance setups revealed less reliable and relative low-matching ability. In conclusion, the reliability of color matching with digital images is much influenced by the illuminants and camera's white balance setups, while digital shade guides derived under LED illuminants with CWB demonstrate applicable potential in the fields of color assessments.
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NASA Astrophysics Data System (ADS)
Schneebeli, M.; Wolf, S.; Kunert, N.; Eugster, W.; Mätzler, C.
2012-04-01
During summer and autumn 2007, a 11 GHz microwave radiometer was deployed in an experimental tree plantation in Sardinilla, Panama. With this instrument, the opacity of the tree canopy was derived from incoming brightness temperatures received on the ground. A collocated eddy-covariance flux tower measured water vapor fluxes and meteorological variables above the canopy. It was found that canopy intercepted rain and dew formation modulated the diurnal opacity cycle. With an enhanced canopy opacity model accounting for water deposited on the leaves, we quantified the influence of canopy stored water (i.e. intercepted water and dew) on the opacity. With this technique it was possible to directly monitor high resolution time series of dew formation and rain interception during a period of two weeks. In contrast to through-fall measurements, this new technique allows to determine the amount of intercepted rain more precisely and during day and night since evaporation effects do not hamper the accuracy of the method. We found that during light rainfall up to 60% of the rain amount is intercepted by the canopy whereas during periods of intense rainfall, only 4% were intercepted. On average, about 15% of the rain amount was intercepted during rainfalls of medium intensities. By comparing the interception with the water vapor flux time series it was found that intercepted water is evaporated rapidly after it is deposited on the leaves, which resulted in an enhanced water vapor flux. Our study also provides the first direct measurements and quantifications of the temporal evolution of dew formation and evaporation in a tree canopy on a diurnal base. Dew accumulated during the night and until about 2 h after sunrise, when the water vapor flux began to exceed the dew formation rate. The dew continued to evaporate for another 3.5 h until the surface of the leaves was completely dry. On average, 0.17 mm of dew was formed during the night. Dew evaporation contributed 5% to the total water vapor flux measured above the canopy.
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Liu, Yang; Qian, Chenyun; Ding, Sihui; Shang, Xulan; Yang, Wanxia; Fang, Shengzuo
2016-12-01
As a highly valued and multiple function tree species, Cyclocarya paliurus is planted and managed for timber production and medical use. However, limited information is available on its genotype selection and cultivation for growth and phytochemicals. Responses of growth and secondary metabolites to light regimes and genotypes are useful information to determine suitable habitat conditions for the cultivation of medicinal plants. Both light regime and provenance significantly affected the leaf characteristics, leaf flavonoid contents, biomass production and flavonoid accumulation per plant. Leaf thickness, length of palisade cells and chlorophyll a/b decreased significantly under shading conditions, while leaf areas and total chlorophyll content increased obviously. In the full light condition, leaf flavonoid contents showed a bimodal temporal variation pattern with the maximum observed in August and the second peak in October, while shading treatment not only reduced the leaf content of flavonoids but also delayed the peak appearing of the flavonoid contents in the leaves of C. paliurus. Strong correlations were found between leaf thickness, palisade length, monthly light intensity and measured flavonoid contents in the leaves of C. paliurus. Muchuan provenance with full light achieved the highest leaf biomass and flavonoid accumulation per plant. Cyclocarya paliurus genotypes show diverse responses to different light regimes in leaf characteristics, biomass production and flavonoid accumulation, highlighting the opportunity for extensive selection in the leaf flavonoid production.
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Light-dependent leaf trait variation in 43 tropical dry forest tree species.
Markesteijn, Lars; Poorter, Lourens; Bongers, Frans
2007-04-01
Our understanding of leaf acclimation in relation to irradiance of fully grown or juvenile trees is mainly based on research involving tropical wet forest species. We studied sun-shade plasticity of 24 leaf traits of 43 tree species in a Bolivian dry deciduous forest. Sampling was confined to small trees. For each species, leaves were taken from five of the most and five of the least illuminated crowns. Trees were selected based on the percentage of the hemisphere uncovered by other crowns. We examined leaf trait variation and the relation between trait plasticity and light demand, maximum adult stature, and ontogenetic changes in crown exposure of the species. Leaf trait variation was mainly related to differences among species and to a minor extent to differences in light availability. Traits related to the palisade layer, thickness of the outer cell wall, and N(area) and P(area) had the greatest plasticity, suggesting their importance for leaf function in different light environments. Short-lived pioneers had the highest trait plasticity. Overall plasticity was modest and rarely associated with juvenile light requirements, adult stature, or ontogenetic changes in crown exposure. Dry forest tree species had a lower light-related plasticity than wet forest species, probably because wet forests cast deeper shade. In dry forests light availability may be less limiting, and low water availability may constrain leaf trait plasticity in response to irradiance.
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Ben, Gui-Ying; Osmond, C. Barry; Sharkey, Thomas D.
1987-01-01
We have examined the effects of mild, chronic water stress and acute water stress on two water stress sensitive plants, Xanthium strumarium and Helianthus annuus. Using a combination of the leaf disc O2 electrode to measure the light responses of photosynthesis and 77 K fluorescence to monitor damage to the primary photochemistry, we have found the following: (a) The CO2 saturated rate of photosynthesis at high light is the most water stress sensitive parameter measured. (b) The apparent quantum yield (moles O2 per mole photons) was slightly, if at all, affected by mild water stress (>−1.5 megapascals). (c) Severe water stress (<−1.5 megapascals) reduced the quantum yield of photosynthesis regardless of whether the stress was applied in sun or shade. The light independent reduction of quantum yield was not associated with a reduction in 77 K fluorescence (Fv/Fm) indicating that the quantum yield reduction was not the result of damage to primary photochemistry. (d) The diel fluctuation in 77 K fluorescence seen in sun-exposed control leaves was greatly exaggerated in water stressed leaves because of enhanced decline in 77 K fluorescence in the morning. The rate of recovery was similar in both control and water stressed leaves. Shaded leaves showed no change in 77 K fluorescence regardless of whether water stress was imposed or not. (e) The water stress sensitive plants used in these experiments did not recover from acute water stress severe enough to reduce the quantum yield or chronic water stress which lasted long enough that light dependent damage to primary photochemistry occurred. PMID:16665465
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Ben, G Y; Osmond, C B; Sharkey, T D
1987-06-01
We have examined the effects of mild, chronic water stress and acute water stress on two water stress sensitive plants, Xanthium strumarium and Helianthus annuus. Using a combination of the leaf disc O(2) electrode to measure the light responses of photosynthesis and 77 K fluorescence to monitor damage to the primary photochemistry, we have found the following: (a) The CO(2) saturated rate of photosynthesis at high light is the most water stress sensitive parameter measured. (b) The apparent quantum yield (moles O(2) per mole photons) was slightly, if at all, affected by mild water stress (>-1.5 megapascals). (c) Severe water stress (<-1.5 megapascals) reduced the quantum yield of photosynthesis regardless of whether the stress was applied in sun or shade. The light independent reduction of quantum yield was not associated with a reduction in 77 K fluorescence (F(v)/F(m)) indicating that the quantum yield reduction was not the result of damage to primary photochemistry. (d) The diel fluctuation in 77 K fluorescence seen in sun-exposed control leaves was greatly exaggerated in water stressed leaves because of enhanced decline in 77 K fluorescence in the morning. The rate of recovery was similar in both control and water stressed leaves. Shaded leaves showed no change in 77 K fluorescence regardless of whether water stress was imposed or not. (e) The water stress sensitive plants used in these experiments did not recover from acute water stress severe enough to reduce the quantum yield or chronic water stress which lasted long enough that light dependent damage to primary photochemistry occurred.
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Optical bi-sensorial measurement system for production control of extruded profiles
NASA Astrophysics Data System (ADS)
Weckenmann, A.; Bernstein, J.
2008-09-01
Extruded profiles are semi-finished products (made out of steel, brass, aluminum, synthetics...) which are appointed for wide applications in manufacturing of technical products. As yet used optical sensors in process control working to the shading technology detect the object's shadow orthographically to the axis of illumination. As a consequence they record it unattached by the profiles coat in measurement range at any point of the measured profile with high precision. As a matter of fact, concave zones cannot be captured. Alternatively the measurement of concave zones can be arranged by light-section systems. These do not comply with the required accuracy, are comparatively slow and moreover affected by dislocations of the section of the profile. A measurement system including a light-section and a shading system combines the advantages of both optical systems. It is to serve with a reliable conception for the assembly of a bi-sensorial measurement system consisting of both systems as well as suitable methods of analysis for the in-line inspection of concave profiles. As a result it contains conclusions concerning requirements of the light source, the arrangement of this source and the cameras, obtainable precision and sampling rate as well as the essential synchronization of both systems. After designing an appropriate prototype, the selected light-section system and the shading system will be synchronized and aligned. Therefore, the metered geometrical data will be merged for the evaluation of form deviation. So, developed and adapted software supports and contains proposals to the uncertainty after successful tests. The system and a calibration method will be proved in production where robustness will be a most critical despite of heat, dust and vibrations. The target uncertainty of less than 0.1 mm at every section of the profiles coat has to be met.
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Füzy, Anna; Bothe, Hermann; Molnár, Edit; Biró, Borbála
2014-03-01
AMF (arbuscular mycorrhizal fungi) colonization of the grass chalk false-brome (Brachypodium pinnatum (L.) P. B.) was studied in selected habitats under spatially different light regimes: (a) shade condition under oak trees, (b) half shade in a shrubby area and (c) full-sun conditions on unshaded grassland. This study assessed the variations in AMF colonization of the grass dependent on the light supply in field habitats. Soil, root and shoot samples were collected four times during the vegetation period (in June, July, September and October). Root colonization, root and shoot biomass as well as soil water content were determined. The highest rate of AMF colonization was detected in June under half-sun and full-sun conditions, where about 50% of the roots were colonized. The average amount of arbuscules was less than 20% in the roots at the three sites, with the highest number of arbuscules in June, under half-sun and full-sun conditions, however, not under the trees. Overall, best mycorrhizal colonization occurred during summer, and its rate decreased in autumn. This tendency inversely correlated with the amount of precipitation, and thus with the water content of soils. The high colonization rate of the examined root samples, and also its seasonal fluctuation, might reflect the importance of the symbiosis where inorganic nutrients and water are the growth-limiting factors. The marginal AMF colonization of chalk false-brome under shade conditions indicates that plants do not use AMF under all stress conditions. When low light limits photosynthesis and thus growth of the plants, they dispense with the colonization of AMF in order to save the expenditure of organic carbon. Copyright © 2013 Elsevier GmbH. All rights reserved.
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Gautier, Hélène; Massot, Capucine; Stevens, Rebecca; Sérino, Sylvie; Génard, Michel
2009-02-01
The mechanisms involving light control of vitamin C content in fruits are not yet fully understood. The present study aimed to evaluate the impact of fruit and leaf shading on ascorbate (AsA) accumulation in tomato fruit and to determine how fruit sugar content (as an AsA precursor) affected AsA content. Cherry tomato plants were grown in a glasshouse. The control treatment (normally irradiated fruits and irradiated leaves) was compared with the whole-plant shading treatment and with leaf or fruit shading treatments in fruits harvested at breaker stage. In a second experiment, the correlation between sugars and AsA was studied during ripening. Fruit shading was the most effective treatment in reducing fruit AsA content. Under normal conditions, AsA and sugar content were correlated and increased with the ripening stage. Reducing fruit irradiance strongly decreased the reduced AsA content (-74 %), without affecting sugars, so that sugar and reduced AsA were no longer correlated. Leaf shading delayed fruit ripening: it increased the accumulation of oxidized AsA in green fruits (+98 %), whereas it decreased the reduced AsA content in orange fruits (-19 %), suggesting that fruit AsA metabolism also depends on leaf irradiance. Under fruit shading only, the absence of a correlation between sugars and reduced AsA content indicated that fruit AsA content was not limited by leaf photosynthesis or sugar substrate, but strongly depended on fruit irradiance. Leaf shading most probably affected fruit AsA content by delaying fruit ripening, and suggested a complex regulation of AsA metabolism which depends on both fruit and leaf irradiance and fruit ripening stage.
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Effect of resin shades on opacity of ceramic veneers and polymerization efficiency through ceramics.
Öztürk, Elif; Chiang, Yu-Chih; Coşgun, Erdal; Bolay, Şükran; Hickel, Reinhard; Ilie, Nicoleta
2013-11-01
The aim of this study was to assess the effect of different resin cement shades on the opacity and color difference of ceramics and to determine the polymerization efficiency of the resin cement at different shades after curing through ceramics. Two different ceramics (IPS e.max Press and IPS Empress(®)CAD, Ivoclar Vivadent) were used for this study. A light-cured veneer luting resin (Variolink Veneer, Ivoclar Vivadent) in four different shades of HV+1, HV+3, LV-1, and LV-3 was used for the colorimetric measurements. The color and spectral reflectance of the ceramics were measured according to the CIELab color scale relative to the standard illuminant D65 on a reflection spectrophotometer (ColorEye7000A, USA). Color differences (ΔE values) and the contrast ratios (CR) of the different groups of samples were calculated. In order to analyse the polymerization efficiency of the resin cements, the micromechanical properties of the resins were measured with an automatic microhardness indenter (Fisherscope H100C, Germany). The results were analysed using one-way ANOVA and Tukey's HSD post hoc tests (SPSS 18.0). The one-way ANOVA test showed that the values of ΔE and CR of the different specimen groups were significantly different (p<0.05). Group 1 (20.7 ± 0.5) (IPS-CAD without resin cement) exhibited the highest and group 10 (14.8 ± 0.5) (e.max:HV+3) exhibited the lowest ΔE value. Significant differences in the micromechanical properties were identified among the tested resin cements in different shades (p<0.05). Resin cement shade is an important factor for the opacity of a restoration. Furthermore, the resin shade affects the micromechanical properties of the underlying resin cement. Copyright © 2013 Elsevier Ltd. All rights reserved.
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Gautier, Hélène; Massot, Capucine; Stevens, Rebecca; Sérino, Sylvie; Génard, Michel
2009-01-01
Background and Aims The mechanisms involving light control of vitamin C content in fruits are not yet fully understood. The present study aimed to evaluate the impact of fruit and leaf shading on ascorbate (AsA) accumulation in tomato fruit and to determine how fruit sugar content (as an AsA precursor) affected AsA content. Methods Cherry tomato plants were grown in a glasshouse. The control treatment (normally irradiated fruits and irradiated leaves) was compared with the whole-plant shading treatment and with leaf or fruit shading treatments in fruits harvested at breaker stage. In a second experiment, the correlation between sugars and AsA was studied during ripening. Key Results Fruit shading was the most effective treatment in reducing fruit AsA content. Under normal conditions, AsA and sugar content were correlated and increased with the ripening stage. Reducing fruit irradiance strongly decreased the reduced AsA content (−74 %), without affecting sugars, so that sugar and reduced AsA were no longer correlated. Leaf shading delayed fruit ripening: it increased the accumulation of oxidized AsA in green fruits (+98 %), whereas it decreased the reduced AsA content in orange fruits (−19 %), suggesting that fruit AsA metabolism also depends on leaf irradiance. Conclusions Under fruit shading only, the absence of a correlation between sugars and reduced AsA content indicated that fruit AsA content was not limited by leaf photosynthesis or sugar substrate, but strongly depended on fruit irradiance. Leaf shading most probably affected fruit AsA content by delaying fruit ripening, and suggested a complex regulation of AsA metabolism which depends on both fruit and leaf irradiance and fruit ripening stage. PMID:19033285
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Aka, Betül; Celik, Esra Uzer
2017-09-01
This randomized controlled clinical trial compared the bleaching efficacy of two different at-home bleaching systems on teeth of different shades and their color stability after a 6-month follow-up. Ninety-two patients (777 teeth) were randomly divided into three groups: (a) negative control, (b) patients treated with a custom-made tray containing 10% carbamide peroxide (10% CP/PF) (Opalescence PF), and (c) patients treated with a pre-loaded tray containing 6% hydrogen peroxide (6% HP/Go) (Opalescence Go). Teeth in all groups were divided into three sub-groups according to the VITA Classic Shade Guide: light (A1-C1), medium dark (C2-B3), and dark (A3.5-C4). Bleaching systems were performed in accordance with manufacturers' instructions for 14 days. The color values were measured at the baseline, 10 days and 14 days of bleaching, 2 weeks, and 6 months after bleaching. Three-way ANOVA and Mann-Whitney U tests were used for statistical analysis (α = 0.05). Irrespective of original shade, both bleaching groups showed significantly higher ΔE* values than the control groups, and the ΔE* values were significantly higher in the 10% CP/PF groups than those in the 6% HP/Go groups (p < 0.05). In both bleaching systems, the dark teeth showed higher ΔE* values than the light teeth (p < 0.05). The ΔE* values decreased significantly only in the 10% CP/PF groups after 6 months (p < 0.05). Both bleaching agents produced a bleaching effect, but 10% CP/PF was more effective. A pre-loaded tray system may be used for dental bleaching, but it is still less effective than conventional a 10% carbamide peroxide system, irrespective of the initial shade. (J Esthet Restor Dent 29:325-338, 2017). © 2017 Wiley Periodicals, Inc.
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Upwelling Measurement Issues at the CERES Ocean Validation Experiment (COVE)
NASA Astrophysics Data System (ADS)
Fabbri, B. E.; Schuster, G. L.; Denn, F. M.; Arduini, R. F.; Madigan, J. J.; Rutan, D. A.
2016-12-01
The Clouds and the Earth's Radiant Energy System (CERES) satellite measures both solar-reflected and Earth-emitted radiation from the Earth's surface to the top of the atmosphere. One surface validation site is located at Chesapeake Light Station, approximately 25 kilometers east of Virginia Beach, Virginia (coordinates: 36.90N, 75.71W). In 1999, the CERES Ocean Validation Experiment (COVE) was established at Chesapeake Light Station. COVE is in its 17th year collecting radiometric and meteorological data. Other measurements over this time period include aerosol optical depth, water leaving radiance, precipitable water vapor and more. The issues we are trying to resolve for the upwelling flux are two-fold. First, there is the "shadow effect". In the morning, the shadow of the tower appears on the water in the field of view underneath the shortwave (SW) and longwave (LW) upwelling instruments. An attempt to understand the shading effect is made by separating the data into "shaded" and "unshaded" time periods using the Solar Azimuth (SA) angle. SA < 180 degrees are considered shaded, and SA > 180 degrees are considered unshaded. Upwelling SW shaded and unshaded datasets differ by a maximum of 9.5 W/m2 and a minimum of -0.7 W/m2 with the delta mean resulting in 3.6 W/m2. Upwelling LW shaded and unshaded datasets differ by a maximum of 8.0 W/m2 and a minimum of 1.0 W/m2 with the delta mean resulting in 3.7 W/m2. The second issue is the "tower radiating effect" which is especially noticeable on clear, sunny days. During these days, the tower tends to heat up and radiate extra heat energy that is measured by the LW instrument. We compare Infrared Radiation Thermometer (IRT) measurements to Precision Infrared Radiometer (PIR) measurements and make a case for using IRT measurements as upwelling LW.
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Fractional-order information in the visual control of lateral locomotor interception.
Bootsma, Reinoud J; Ledouit, Simon; Casanova, Remy; Zaal, Frank T J M
2016-04-01
Previous work on locomotor interception of a target moving in the transverse plane has suggested that interception is achieved by maintaining the target's bearing angle (often inadvertently confused and/or confounded with the target heading angle) at a constant value. However, dynamics-based model simulations testing the veracity of the underlying control strategy of nulling the rate of change in the bearing angle have been restricted to limited conditions of target motion, and only a few alternatives have been considered. Exploring a wide range of target motion characteristics with straight and curving ball trajectories in a virtual reality setting, we examined how soccer goalkeepers moved along the goal line to intercept long-range shots on goal, a situation in which interception is naturally constrained to movement along a single dimension. Analyses of the movement patterns suggested reliance on combinations of optical position and velocity for straight trajectories and optical velocity and acceleration for curving trajectories. As an alternative to combining such standard integer-order derivatives, we demonstrate with a simple dynamical model that nulling a single informational variable of a self-tuned fractional (rather than integer) order efficiently captures the timing and patterning of the observed interception behaviors. This new perspective could fundamentally change the conception of what perceptual systems may actually provide, both in humans and in other animals. (PsycINFO Database Record (c) 2016 APA, all rights reserved).
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ERIC Educational Resources Information Center
Andrieux, Mathieu; Danna, Jeremy; Thon, Bernard
2012-01-01
The aim of the present work was to analyze the influence of self-controlled task difficulty on motor learning. Participants had to intercept three targets falling at different velocities by displacing a stylus above a digitizer. Task difficulty corresponded to racquet width. Half the participants (self-control condition) could choose the racquet…
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Biological cell classification by multiangle light scattering
Salzman, G.C.; Crowell, J.M.; Mullaney, P.F.
1975-06-03
The specification is directed to an apparatus and method for detecting light scattering from a biological cell. Light, preferably from a coherent source of radiation, intercepts an individual biological cell in a stream of cells passing through the beam. Light scattered from the cell is detected at a selected number of angles between 0 and 90/sup 0/ to the longitudinal axis of the beam with a circular array of light responsive elements which produce signals representative of the intensity of light incident thereon. Signals from the elements are processed to determine the light-scattering pattern of the cell and therefrom its identity.
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Zlatanović, Sanja; Fabian, Jenny; Premke, Katrin; Mutz, Michael
2018-04-15
Perennial, temperate, low-order streams are predicted to become intermittent as a result of irregular droughts caused by global warming and increased water demand. We hypothesize that stream metabolism changes caused by irregular droughts are linked to the shading and bed sediment structure of temperate streams. We set up 16 outdoor experimental streams with low or high shade conditions and streambeds either with alternating sorted patches of gravel and sand or homogeneous gravel-sand mix sediment structures. We assessed community respiration (CR), net ecosystem production (NEP) and periphyton biomass and structure (diatoms, green algae, cyanobacteria) in the course of 6weeks colonization, 6weeks desiccation, and 2.5weeks after rewetting. The heterotroph to autotroph (H:A) and fungi to bacteria (F:B) ratios in the microbial biofilm community were assessed at the end of the colonization and rewetting phases. Streams with different bed sediment structure were functionally similar; their metabolism under desiccation was controlled solely by light availability. During flow recession, all streams showed net heterotrophy. As desiccation progressed, NEP and CR decreased to zero. Desiccation altered the periphyton composition from predominantly diatoms to green algae and cyanobacteria, particularly in streams with low shade and mixed sediments. Rapid post-drought resilience of NEP was accompanied by high cyanobacteria and green algae growth in low shade, but poor total periphyton growth in high shade streams. Variable periphyton recovery was followed by increased H:A in relation to shading, and decreased F:B in relation to sediments structure. These shifts resulted in poor CR recovery compared to the colonization phase, suggesting a link between CR resilience and microbial composition changes. The links between drought effects, post-drought recovery, shading level, and streambed structure reveal the importance of low-order stream management under a changing climate and land use to mitigate the future impact of unpredictable infrequent droughts on stream metabolism in temperate ecosystems. Copyright © 2017 Elsevier B.V. All rights reserved.
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2011-10-26
This global digital map of Saturn moon Titan was created using images taken by NASA Cassini spacecraft imaging science subsystem ISS. Because of the scattering of light by Titan dense atmosphere, no topographic shading is visible here.
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Gary W. Miller; James N. Kochenerfer; Kurt W. Gottschalk
2004-01-01
Successful oak regeneration is related to the size and number of advanced seedlings present when harvests occur. This study was installed to quantify the effect of microsite light availability and deer on the development of advanced northern red oak (Quercus rubra L.) reproduction in mesic Appalachian hardwood stands. Microsite light was manipulated...
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Malcolm North; Jiquan Chen; Brian Oakley; Bo Song; Mark Rudnicki; Andrew Gray; Jim Innes
2004-01-01
With fire suppression, many western forests are expected to have fewer gaps and higher stem density of shade-tolerant species as light competition becomes a more significant influence on stand pattern and composition. We compared species composition, structure, spatial pattern, and environmental factors such as light and soil moisture between two old-growth forests:...
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Dobbinson, S J; Veitch, J; Salmon, J; Wakefield, M; Staiger, P K; MacInnis, R J; Simmons, J
2017-02-22
Parks in disadvantaged suburbs often have low quality and few amenities, which is likely to result in them being underutilised for recreation and physical activity. Refurbishment of parks, including shade, walking paths and other amenities, may have broad health-related benefits. The study design, methods and planned analyses for a natural experiment examining the effects of refurbishments including built-shade added to parks in disadvantaged outer suburbs of Melbourne are described. Three intervention parks and three comparison parks matched for equivalence of park and neighbourhood characteristics were selected. Using mixed methods, the outcomes will be assessed during three consecutive spring-summer periods (T1: 2013-2014; T2: 2014-2015: T3: 2015-2016). Primary outcomes included: observed park use, physical activity and shade use. Self-reported social connectedness, community engagement and psychological well-being were assessed as secondary outcomes. This study was approved by Cancer Council Victoria's Human Research Ethics Committee. Studies such as ShadePlus can improve understanding of the broader effects of park refurbishments (including physical activity levels and sun protection behaviours, as well as social connectedness and psychological well-being). The study findings will be disseminated through established urban planning and parks and recreation networks, peer review publications and conference presentations. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.
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Charting color from the eye of the beholder
Landa, Edward; Fairchild, Mark
2005-01-01
Everyone knows the particular shade of yellow that adorns all school buses across the United States. But how do we define exactly what shade this is, and reproduce the same color from coast to coast? Much of the standardization of colors stems from the century-old work of Alfred Munsell, who created one of the first colorimetry systems defined by how people see color: lightness, hue, and chroma (how much the apparent hue differs from neutral grey). Munsell's color charts have been customized for different fields, and are still in use in areas as diverse as beer brewing and soil science.
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Vance, Nan C.; Copes, Donald O.; Zaerr, Joe B.
1990-01-01
Proteins were radiolabeled and extracted from needles of Pinus ponderosa var scopulorum (Dougl. ex Laws.) seedlings progressively drought-stressed for about 1 month. A set of novel, low molecular weight proteins was detected in fluorographs of two-dimensional gels when relative water content of needles fell below 70%. Their synthesis was undetectable in the fully recovered seedlings within 48 hours after rewatering. In similarly stressed seedlings that were shaded to 10% full light, the low molecular weight polypeptides were not detected or appeared at very low levels. The shaded seedlings, in which drought tolerance was reduced, did not recover upon termination of the drought. The results suggest that protein synthesis induced by water deficit in drought-tolerant seedlings may contribute to resisting the effects of cellular dehydration. Images Figure 1 Figure 2 PMID:16667397
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DOE Office of Scientific and Technical Information (OSTI.GOV)
García-Linares, Pablo, E-mail: pablo.garcia-linares@cea.fr; Voarino, Philippe; Besson, Pierre
2015-09-28
Concentrator solar cell front-grid metallizations are designed so that the trade-off between series resistance and shading factor (SF) is optimized for a particular irradiance. High concentrator photovoltaics (CPV) typically requires a metallic electrode pattern that covers up to 10% of the cell surface. The shading effect produced by this front electrode results in a significant reduction in short-circuit current (I{sub SC}) and hence, in a significant efficiency loss. In this work we present a cover glass (originally meant to protect the cell surface) that is laser-grooved with a micrometric pattern that redirects the incident solar light towards interfinger regions andmore » away from the metallic electrodes, where they would be wasted in terms of photovoltaic generation. Quantum efficiency (QE) and current (I)-voltage (V) characterization under concentration validate the proof-of-concept, showing great potential for CPV applications.« less
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NASA Technical Reports Server (NTRS)
Zander, Martin; Belvin, W. K.
2012-01-01
Current space applications of membrane structures include large area solar power arrays, solar sails, antennas, and numerous other large aperture devices like the solar shades of the new James Webb Space Telescope. These expandable structural systems, deployed in-orbit to achieve the desired geometry, are used to collect, reflect and/or transmit electromagnetic radiation. This work, a feasibility study supporting a diploma thesis, describes the systematic process for developing a biologically inspired concept for a structure supported (integrated) membrane, that features a rip stop principle, makes self-deployment possible and is part of an ultra-light weight space application. Novel manufacturing of membrane prototypes and test results are presented for the rip-stop concepts. Test data showed that the new membrane concept has a higher tear resistance than neat film of equivalent mass.
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The Use of Terrestrial Laser Scanning for Determining the Driver’s Field of Vision
Zemánek, Tomáš; Cibulka, Miloš; Skoupil, Jaromír
2017-01-01
Terrestrial laser scanning (TLS) is currently one of the most progressively developed methods in obtaining information about objects and phenomena. This paper assesses the TLS possibilities in determining the driver’s field of vision in operating agricultural and forest machines with movable and immovable components in comparison to the method of using two light point sources for the creation of shade images according to ISO (International Organization for Standardization) 5721-1. Using the TLS method represents a minimum time saving of 55% or more, according to the project complexity. The values of shading ascertained by using the shadow cast method by the point light sources are generally overestimated and more distorted for small cabin structural components. The disadvantage of the TLS method is the scanner’s sensitivity to a soiled or scratched cabin windscreen and to the glass transparency impaired by heavy tinting. PMID:28902177
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Chang, Jiun-Yao; Chen, Wen-Cheng; Huang, Ta-Ko; Wang, Jen-Chyan; Fu, Po-Sung; Chen, Jeng-Huey; Hung, Chun-Cheng
2012-09-01
As we pay increasing attention to dental aesthetics, tooth color matching has become an important part of daily dental practice. This aim of this study was to develop a method to enhance the accuracy of a tooth color matching machine. The Munsell color tabs in the range of natural human teeth were measured using a tooth color measuring machine (ShadeEye NCC). The machine's accuracy was analyzed using an analysis of variance test and a Tukey post-hoc test. When matching the Munsell color tabs with the ShadeEye NCC colorimeter, settings of Chroma greater than 6 and Value less than 4 showed unacceptable clinical results. When the CIELAB mode was used, the a* value (which represents the red-green axis in the Commission Internationale de l'Eclairage color space) made no significant difference (p=0.84), the L* value (which represents the lightness) resulted in a negative correlation, and the b* value (which represents the yellow-blue axis) resulted in a positive correlation with ΔE. When the Munsell color tabs and the Vitapan were measured in the same mode and compared, the inaccuracies showed that the Vitapan was not a proper tool for evaluating the stability and accuracy of ShadeEye NCC. By knowing the limitations of the machine, we evaluated the data using the Munsell color tabs; shade beyond the acceptable range should be reevaluated using a visual shade matching method, or if measured by another machine, this shade range should be covered to obtain more accurate results. Copyright © 2012. Published by Elsevier B.V.
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Difference in the color stability of direct and indirect resin composites
LEE, Yong-Keun; YU, Bin; LIM, Ho-Nam; LIM, Jin Ik
2011-01-01
Indirect resin composites are generally regarded to have better color stability than direct resin composites since they possess higher conversion degree Objective The present study aimed at comparing the changes in color (∆E) and color coordinates (∆L, ∆a and ∆b) of one direct (Estelite Sigma: 16 shades) and 2 indirect resin composites (BelleGlass NG: 16 shades; Sinfony: 26 shades) after thermocycling. Material and Methods Resins were packed into a mold and light cured; post-curing was performed on indirect resins. Changes in color and color coordinates of 1-mm-thick specimens were determined after 5,000 cycles of thermocycling on a spectrophotometer. Results ∆E values were in the range of 0.3 to 1.2 units for direct resins, and 0.3 to 1.5 units for indirect resins, which were clinically acceptable (∆E<3.3). Based on t-test, ∆E values were not significantly different by the type of resins (p>0.05), while ∆L, ∆a and ∆b values were significantly different by the type of resins (p<0.05). For indirect resins, ∆E values were influenced by the brand, shade group and shade designation based on three-way ANOVA (p<0.05). Conclusion Direct and indirect resin composites showed similar color stability after 5,000 cycles of thermocycling; however, their changes in the color coordinates were different. PMID:21552717
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Leicht-Young, S. A.; Latimer, A.M.; Silander, J.A.
2011-01-01
The neighborhood density of plants strongly affects their growth, reproduction, and survival. In most cases, high density increases competition and negatively affects a focal plant in predictable ways, leading to the self-thinning law. There are, however, situations in which high densities of plants facilitate focal plant performance, resulting in positive density dependence. Despite their importance in forest gap dynamics and distinctive growth form, there have been very few studies of the effect of density on lianas or vines. We grew an invasive (Celastrus orbiculatus) and a native (Celastrus scandens) liana species together in three different density treatments, while also manipulating the light and support availability. We found that across treatment conditions, C. orbiculatus always out-performed C. scandens, showing greater relative growth rate in height and diameter, greater biomass and higher survival. Both species responded similarly to the density treatments: with plants in high density not showing a decrease in relative height growth rate compared to medium density. Aboveground biomass for C. scandens was not affected by density, while for C. orbiculatus, the most massive plants were growing in medium density without support. More surprisingly, survival analysis indicated that the two species both had significantly lower mortality rates in the highest density treatment; this trend held true across the other treatments of light and supports. More generally, this study demonstrates that these lianas can escape the consequences of high density and thus the self-thinning law that affects self-supporting plants. This suggests a broader hypothesis about lianas in general: their greater flexibility in allocating growth resources allows them to grow taller and thinner without collapsing and thereby potentially escape shading and mortality even at high densities.
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Vehicle and cargo inspection system
NASA Astrophysics Data System (ADS)
Verbinski, Victor V.; Orphan, Victor J.
1997-02-01
Vehicle and Cargo Inspection System (VACIS) is comprised of a 1 Curie 137Cs gamma-ray source in a shield and collimator which produces a fan-shaped beam designed to intercept a vertical array of gama-ray detectors contained in a tower structure. The source and detector modules straddle the vehicle or container being inspected and are mounted on self-propelled trolleys which travel in synchronization along two parallel tracks covering the length of the scanned object. The signals from the gamma-ray detector array are processed and displayed so as to produce a 2D gamma-radiographic image of the object. Testing of the system on a variety of empty and lightly-loaded vehicles and containers has demonstrated the effectiveness of VACIS in detecting hidden contraband. For example, a small sample of cocaine only 1.5 inches thick was readily detected in a container.
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Bongers, Franca J; Pierik, Ronald; Anten, Niels P R; Evers, Jochem B
2017-12-21
Although phenotypic plasticity has been shown to be beneficial for plant competitiveness for light, there is limited knowledge on how variation in these plastic responses plays a role in determining competitiveness. A combination of detailed plant experiments and functional-structural plant (FSP) modelling was used that captures the complex dynamic feedback between the changing plant phenotype and the within-canopy light environment in time and 3-D space. Leaf angle increase (hyponasty) and changes in petiole elongation rates in response to changes in the ratio between red and far-red light, two important shade avoidance responses in Arabidopsis thaliana growing in dense population stands, were chosen as a case study for plant plasticity. Measuring and implementing these responses into an FSP model allowed simulation of plant phenotype as an emergent property of the underlying growth and response mechanisms. Both the experimental and model results showed that substantial differences in competitiveness may arise between genotypes with only marginally different hyponasty or petiole elongation responses, due to the amplification of plant growth differences by small changes in plant phenotype. In addition, this study illustrated that strong competitive responses do not necessarily have to result in a tragedy of the commons; success in competition at the expense of community performance. Together, these findings indicate that selection pressure could probably have played a role in fine-tuning the sensitive shade avoidance responses found in plants. The model approach presented here provides a novel tool to analyse further how natural selection could have acted on the evolution of plastic responses.
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NASA Astrophysics Data System (ADS)
Loranty, Michael M.; Mackay, D. Scott; Ewers, Brent E.; Traver, Elizabeth; Kruger, Eric L.
2010-12-01
We have used an ecosystem model, TREES (Terrestrial Regional Ecosystem Exchange Simulator), to test the hypothesis that competition for light limits reference canopy stomatal conductance (GSref; conductance at 1 kPa vapor pressure deficit) for individual tree crowns. Sap flux (JS) data was collected at an aspen-dominated unmanaged early successional site, and at a sugar maple dominated midsuccessional site managed for timber production. Using a Monte Carlo approach, JS scaled canopy transpiration (EC) estimates were used to parameterize two versions of the model for each tree individually; a control model treated trees as isolated individuals, and a modified version incorporated the shading effects of neighboring individuals on incident radiation. Agreement between simulated and observed EC was better for maple than for aspen using the control model. Accounting for canopy heterogeneity using a three-dimensional canopy representation had minimal effects on estimates of GSref or model performance for individual maples. At the Aspen site the modified model resulted in improved EC estimates, particularly for trees with lower GSref and more shading by neighboring individuals. Our results imply a link between photosynthetic capacity, as mediated by competitive light environment, and GSref. We conclude that accounting for the effects of canopy heterogeneity on incident radiation improves modeled estimates of canopy carbon and water fluxes, especially for shade intolerant species. Furthermore our results imply a link between ecosystem structure and function that may be exploited to elucidate the impacts of forest structural heterogeneity on ecosystem fluxes of carbon and water via LiDAR remote sensing.
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NASA Astrophysics Data System (ADS)
Bonan, Gordon B.; Oleson, Keith W.; Fisher, Rosie A.; Lasslop, Gitta; Reichstein, Markus
2012-06-01
The Community Land Model version 4 overestimates gross primary production (GPP) compared with estimates from FLUXNET eddy covariance towers. The revised model of Bonan et al. (2011) is consistent with FLUXNET, but values for the leaf-level photosynthetic parameterVcmaxthat yield realistic GPP at the canopy-scale are lower than observed in the global synthesis of Kattge et al. (2009), except for tropical broadleaf evergreen trees. We investigate this discrepancy betweenVcmaxand canopy fluxes. A multilayer model with explicit calculation of light absorption and photosynthesis for sunlit and shaded leaves at depths in the canopy gives insight to the scale mismatch between leaf and canopy. We evaluate the model with light-response curves at individual FLUXNET towers and with empirically upscaled annual GPP. Biases in the multilayer canopy with observedVcmaxare similar, or improved, compared with the standard two-leaf canopy and its lowVcmax, though the Amazon is an exception. The difference relates to light absorption by shaded leaves in the two-leaf canopy, and resulting higher photosynthesis when the canopy scaling parameterKn is low, but observationally constrained. Larger Kndecreases shaded leaf photosynthesis and reduces the difference between the two-leaf and multilayer canopies. The low modelVcmaxis diagnosed from nitrogen reduction of GPP in simulations with carbon-nitrogen biogeochemistry. Our results show that the imposed nitrogen reduction compensates for deficiency in the two-leaf canopy that produces high GPP. Leaf trait databases (Vcmax), within-canopy profiles of photosynthetic capacity (Kn), tower fluxes, and empirically upscaled fields provide important complementary information for model evaluation.
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Earthshots: Satellite images of environmental change – Lake Urmia, Iran
Adamson, Thomas
2015-01-01
The lake’s southern basin is shallower than its northern basin, so recent images show the water disappearing from the southern basin first. These Landsat images use the shortwave-infrared, near-infrared, and green wavelengths of light. Because water absorbs infrared light, water (dark blue to black) contrasts with the surrounding land areas. As the water becomes shallower, light is reflected off of the lakebed in shades of light blue. Lighter blue and bright areas immediately surrounding the lake are where the receding shoreline has exposed the lake bottom.
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Si, Yang; Zhang, Zheng; Wu, Wanrong; Fu, Qiuxia; Huang, Kang; Nitin, Nitin; Ding, Bin; Sun, Gang
2018-01-01
Emerging infectious diseases (EIDs) are a significant burden on global economies and public health. Most present personal protective equipment used to prevent EID transmission and infections is typically devoid of antimicrobial activity. We report on green bioprotective nanofibrous membranes (RNMs) with rechargeable antibacterial and antiviral activities that can effectively produce biocidal reactive oxygen species (ROS) solely driven by the daylight. The premise of the design is that the photoactive RNMs can store the biocidal activity under light irradiation and readily release ROS under dim light or dark conditions, making the biocidal function “always online.” The resulting RNMs exhibit integrated properties of fast ROS production, ease of activity storing, long-term durability, robust breathability, interception of fine particles (>99%), and high bactericidal (>99.9999%) and virucidal (>99.999%) efficacy, which enabled to serve as a scalable biocidal layer for protective equipment by providing contact killing against pathogens either in aerosol or in liquid forms. The successful synthesis of these fascinating materials may provide new insights into the development of protection materials in a sustainable, self-recharging, and structurally adaptive form. PMID:29556532
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Chlorophyll Fluorescence Is a Better Proxy for Sunlit Leaf Than Total Canopy Photosynthesis
NASA Astrophysics Data System (ADS)
Chen, J. M.; Wang, Z.; Zhang, F.; Mo, G.
2015-12-01
Chlorophyll fluorescence (CF) results from non-photochemical quenching during plant photosynthesis under excessive radiation. We explore the relationship between gross primary productivity (GPP) and CF using a process ecosystem model, which separates a vegetation canopy into sunlit and shaded leaf groups and simulates the total canopy GPP as the sum of sunlit and shaded leaf GPP. Using GOME-2 and GOSAT data acquired in 2010 over the global land surface, we found that measured CF signals gridded in 1 degree resolution are well correlated with simulated total GPP and its sunlit and shaded components, but the correlation coefficients (R) are largest for the sunlit GPP and smallest for shaded GPP. The seasonal R2 values vary from 0.57 to 0.74, 0.58 to 0.71, and 0.48 to 0.56 for sunlit, total and shaded GPP, respectively. The significance levels for these correlations are all greater than p<0.01. Averaged over the globe, the total simulated shaded GPP is 39% of the total GPP. Theoretically, CF from vegetation comes mostly from sunlit leaves. The significant correlation between measured canopy-level CF and the shaded GPP is likely due to the correlation between shaded and sunlit GPP as both increase with leaf area index. Our simulation confirms the validity of using canopy-level CF measurements to assess the total GPP as the first approximation, although these measurements are a consistently better indicator of sunlit GPP than total GPP. In previous studies, the R2 values for the correlation between CF and total GPP were found to range from 0.76 to 0.88, 0.56 to 0.78, and 0.57 to 0.77 for MPI-BGC, MODIS and CASA model results, respectively. These values are similar or larger than those for sunlit GPP simulated in our study, but are considerably larger than those for total GPP in our study because the correlation for total GPP is contaminated by the inclusion of shaded GPP. All these three models use canopy total light use efficiency without considering the differences between sunlit and shaded leaves, and therefore they mostly capture spatio-temporal variations in sunlit GPP. We therefore argue that solar-induced CF measured from vegetation is a better proxy of sunlit GPP than the total GPP, and the use of CF data for assessing the terrestrial carbon cycle can be improved when sunlit and shaded GPP are modelled separately.
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Kim, Jin-Cheol; Yu, Bin; Lee, Yong-Keun
2008-12-01
To determine the changes in color parameters of Vitapan 3D-Master shade guide tabs by a spectrophotometer (SP) or a spectroradiometer (SR), and by the removal of the surface layer of the tabs that was performed to make a flat measuring surface for the SP color measurement. Color of the shade tabs was measured before and after removing the surface layer of the tabs using SP and SR. Correlations between the color parameters between the original (OR) and the surface layer removed (RM) tabs and between the SP and the SR measurements were determined (alpha=0.05). Based on SP, the lightness, chroma, CIE a* and b* values measured after the surface layer removal were higher than those of the original tabs except a few cases. Based on SR, the chroma and CIE a* and b* values measured after surface layer removal were higher than those of the original tabs except a few cases; however, in case of the lightness, the changes varied by the shade designation. Type of instrument influenced the changes in color parameters based on paired t-test (p<0.05). The color parameters of the OR and RM tabs showed correlations based on both SP and SR measurements (r=0.952-0.997 and p<0.01); however, color difference between the SP-RM and SR-OR tabs was in the range of 18.1-27.0 DeltaE(ab)(*) units (mean: 23.3+/-2.2). When the color of tooth-shaped objects is measured with a spectrophotometer or a spectroradiometer, measurement protocols should be specified because color difference by the surface layer removal and the instrument was high.
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Niglas, Aigar; Papp, Kaisa; Sekiewicz, Maciej; Sellin, Arne
2017-09-01
Leaves have to acclimatize to heterogeneous radiation fields inside forest canopies in order to efficiently exploit diverse light conditions. Short-term effects of light quality on photosynthetic gas exchange, leaf water use and hydraulic traits were studied on Betula pendula Roth shoots cut from upper and lower thirds of the canopy of 39- to 35-year-old trees growing in natural forest stand, and illuminated with white, red or blue light in the laboratory. Photosynthetic machinery of the leaves developed in different spectral conditions acclimated differently with respect to incident light spectrum: the stimulating effect of complete visible spectrum (white light) on net photosynthesis is more pronounced in upper-canopy layers. Upper-canopy leaves exhibit less water saving behaviour, which may be beneficial for the fast-growing pioneer species on a daily basis. Lower-canopy leaves have lower stomatal conductance resulting in more efficient water use. Spectral gradients existing within natural forest stands represent signals for the fine-tuning of stomatal conductance and tree water relations to afford lavish water use in sun foliage and enhance leaf water-use efficiency in shade foliage sustaining greater hydraulic limitations. Higher sensitivity of hydraulic conductance of shade leaves to blue light probably contributes to the efficient use of short duration sunflecks by lower-canopy leaves. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Shaded relief of Bahia State, Brazil
NASA Technical Reports Server (NTRS)
2000-01-01
This topographic image is the first to show the full 240-kilometer-wide (150 mile)swath collected by the Shuttle Radar Topography Mission (SRTM). The area shown is in the state of Bahia in Brazil. The semi-circular mountains along the left side of the image are the Serra Da Jacobin, which rise to 1100 meters (3600 feet) above sea level. The total relief shown is approximately 800 meters (2600 feet). The top part of the image is the Sertao, a semi-arid region, that is subject to severe droughts during El Nino events. A small portion of the San Francisco River, the longest river (1609 kilometers or 1000 miles) entirely within Brazil, cuts across the upper right corner of the image. This river is a major source of water for irrigation and hydroelectric power. Mapping such regions will allow scientists to better understand the relationships between flooding cycles, drought and human influences on ecosystems.
This shaded relief image was generated using topographic data from the Shuttle Radar Topography Mission. A computer-generated artificial light source illuminates the elevation data to produce a pattern of light and shadows. Slopes facing the light appear bright, while those facing away are shaded. On flatter surfaces, the pattern of light and shadows can reveal subtle features in the terrain. Colors show the elevation as measured by SRTM. Colors range from green at the lowest elevations to reddish at the highest elevations. Shaded relief maps are commonly used in applications such as geologic mapping and land use planning.The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) and the German (DLR) and Italian (ASI) space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC. -
Shaded Relief of Rio Sao Francisco, Brazil
NASA Technical Reports Server (NTRS)
2000-01-01
This topographic image acquired by SRTM shows an area south of the Sao Francisco River in Brazil. The scrub forest terrain shows relief of about 400 meters (1300 feet). Areas such as these are difficult to map by traditional methods because of frequent cloud cover and local inaccessibility. This region has little topographic relief, but even subtle changes in topography have far-reaching effects on regional ecosystems. The image covers an area of 57 km x 79 km and represents one quarter of the 225 km SRTM swath. Colors range from dark blue at water level to white and brown at hill tops. The terrain features that are clearly visible in this image include tributaries of the Sao Francisco, the dark-blue branch-like features visible from top right to bottom left, and on the left edge of the image, and hills rising up from the valley floor. The San Francisco River is a major source of water for irrigation and hydroelectric power. Mapping such regions will allow scientists to better understand the relationships between flooding cycles, forestation and human influences on ecosystems.
This shaded relief image was generated using topographic data from the Shuttle Radar Topography Mission. A computer-generated artificial light source illuminates the elevation data to produce a pattern of light and shadows. Slopes facing the light appear bright, while those facing away are shaded. On flatter surfaces, the pattern of light and shadows can reveal subtle features in the terrain. Shaded relief maps are commonly used in applications such as geologic mapping and land use planning.The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC. -
NASA Astrophysics Data System (ADS)
Nieschulze, Jens; Erasmi, Stefan; Dietz, Johannes; Hölscher, Dirk
2009-01-01
SummaryRainforest conversion to other land use types drastically alters the hydrological cycle in which changes in rainfall interception contribute significantly to the observed differences. However, little is known about the effects of more gradual changes in forest structure and at regional scales. We studied land use types ranging from natural forest over selectively-logged forest to cacao agroforest in a lower montane region in Central Sulawesi, Indonesia, and tested the suitability of high-resolution optical satellite imagery for modeling observed interception patterns. Investigated characteristics indicating canopy structure were mean and standard deviation of reflectance values, local maxima, and self-similarity measures based on the grey level co-occurrence matrix and geostatistical variogram analysis. Previously studied and published rainfall interception data comprised twelve plots and median values per land use type ranged from 30% in natural forest to 18% in cacao agroforests. A linear regression model with local maxima, mean contrast and normalized digital vegetation index (NDVI) as regressors was able to explain more than 84% ( Radj2) of the variation encountered in the data. Other investigated characteristics did not prove significant in the regression analysis. The model yielded stable results with respect to cross-validation and also produced realistic values and spatial patterns when applied at the landscape level (783.6 ha). High values of interception were rare and localized in natural forest stands distant to villages, whereas low interception characterized the intensively used sites close to settlements. We conclude that forest use intensity significantly reduced rainfall interception and satellite image analysis can successfully be applied for its regional prediction, and most forest in the study region has already been subject to human-induced structural changes.
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NASA Astrophysics Data System (ADS)
Qiu, Zhaoyang; Wang, Pei; Zhu, Jun; Tang, Bin
2016-12-01
Nyquist folding receiver (NYFR) is a novel ultra-wideband receiver architecture which can realize wideband receiving with a small amount of equipment. Linear frequency modulated/binary phase shift keying (LFM/BPSK) hybrid modulated signal is a novel kind of low probability interception signal with wide bandwidth. The NYFR is an effective architecture to intercept the LFM/BPSK signal and the LFM/BPSK signal intercepted by the NYFR will add the local oscillator modulation. A parameter estimation algorithm for the NYFR output signal is proposed. According to the NYFR prior information, the chirp singular value ratio spectrum is proposed to estimate the chirp rate. Then, based on the output self-characteristic, matching component function is designed to estimate Nyquist zone (NZ) index. Finally, matching code and subspace method are employed to estimate the phase change points and code length. Compared with the existing methods, the proposed algorithm has a better performance. It also has no need to construct a multi-channel structure, which means the computational complexity for the NZ index estimation is small. The simulation results demonstrate the efficacy of the proposed algorithm.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Stimson, J.
1985-02-01
Field surveys at Enewetak Atoll, Marshall Islands, show that coral density and diversity is much lower beneath Acropora table corals than in adjacent unshaded areas. Additionally, the understory community is predominantly composed of massive and encrusting species, while branching Acropora and Pocillopora predominate in unshaded areas. Results of experiments in which coral fragments were transferred to the shade of table Acropora and to adjacent unshaded areas show that shading slows the growth and leads to higher mortality of branching species, while massive and encrusting species are unaffected. Light measurements made beneath table Acropora show that illumination and irradiance values fallmore » to levels at which most hermatypic corals do not occur. The fast-growing but fragile table Acropora are abundant in a wide variety of atoll habitats and grow rapidly to form a canopy approx. = 50 cm above the substrate. However, table Acropora also have high mortality rates, so that there is continuous production of unshaded areas. The growth and death of tables thus create local disturbances, and the resulting patchwork of recently shaded and unshaded areas may enhance coral diversity in areas of high coral cover.« less
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High-quality remote interactive imaging in the operating theatre
NASA Astrophysics Data System (ADS)
Grimstead, Ian J.; Avis, Nick J.; Evans, Peter L.; Bocca, Alan
2009-02-01
We present a high-quality display system that enables the remote access within an operating theatre of high-end medical imaging and surgical planning software. Currently, surgeons often use printouts from such software for reference during surgery; our system enables surgeons to access and review patient data in a sterile environment, viewing real-time renderings of MRI & CT data as required. Once calibrated, our system displays shades of grey in Operating Room lighting conditions (removing any gamma correction artefacts). Our system does not require any expensive display hardware, is unobtrusive to the remote workstation and works with any application without requiring additional software licenses. To extend the native 256 levels of grey supported by a standard LCD monitor, we have used the concept of "PseudoGrey" where slightly off-white shades of grey are used to extend the intensity range from 256 to 1,785 shades of grey. Remote access is facilitated by a customized version of UltraVNC, which corrects remote shades of grey for display in the Operating Room. The system is successfully deployed at Morriston Hospital, Swansea, UK, and is in daily use during Maxillofacial surgery. More formal user trials and quantitative assessments are being planned for the future.
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Restoring warped document images through 3D shape modeling.
Tan, Chew Lim; Zhang, Li; Zhang, Zheng; Xia, Tao
2006-02-01
Scanning a document page from a thick bound volume often results in two kinds of distortions in the scanned image, i.e., shade along the "spine" of the book and warping in the shade area. In this paper, we propose an efficient restoration method based on the discovery of the 3D shape of a book surface from the shading information in a scanned document image. From a technical point of view, this shape from shading (SFS) problem in real-world environments is characterized by 1) a proximal and moving light source, 2) Lambertian reflection, 3) nonuniform albedo distribution, and 4) document skew. Taking all these factors into account, we first build practical models (consisting of a 3D geometric model and a 3D optical model) for the practical scanning conditions to reconstruct the 3D shape of the book surface. We next restore the scanned document image using this shape based on deshading and dewarping models. Finally, we evaluate the restoration results by comparing our estimated surface shape with the real shape as well as the OCR performance on original and restored document images. The results show that the geometric and photometric distortions are mostly removed and the OCR results are improved markedly.
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Light-Mediated Hormonal Regulation of Plant Growth and Development.
de Wit, Mieke; Galvão, Vinicius Costa; Fankhauser, Christian
2016-04-29
Light is crucial for plant life, and perception of the light environment dictates plant growth, morphology, and developmental changes. Such adjustments in growth and development in response to light conditions are often established through changes in hormone levels and signaling. This review discusses examples of light-regulated processes throughout a plant's life cycle for which it is known how light signals lead to hormonal regulation. Light acts as an important developmental switch in germination, photomorphogenesis, and transition to flowering, and light cues are essential to ensure light capture through architectural changes during phototropism and the shade avoidance response. In describing well-established links between light perception and hormonal changes, we aim to give insight into the mechanisms that enable plants to thrive in variable light environments.
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Xie, Tian-peng; Zhang, Ge-fei; Zhao, Zhi-gang; Du, Guo-zhen; He, Gui-yong
2014-01-01
The relationship between sexual reproduction and clonal growth in clonal plants often shows up at the ramet level. However, only a few studies focus on the relationship at the genet level, which could finally account for evolution. The sexual reproduction and clonal growth of Ligularia virgaurea, a perennial herb widely distributed in the alpine grasslands of the Qinghai-Tibetan Plateau of China, were studied under different competition intensities and light conditions at the genet level through a potted experiment. The results showed that: (1) sexual reproduction did not depend on density or light, and increasing clonal growth with decreasing density and increasing light intensity indicated that intraspecific competition and light intensity may affect the clonal life history of L. virgaurea; (2) both sexual reproduction and clonal growth show a positive linear relationship with genet size under different densities and light conditions; (3) a threshold size is required for sexual reproduction and no evidence of a threshold size for clonal growth under different densities and light conditions; (4) light level affected the allocation of total biomass to clonal and sexual structures, with less allocation to clonal structures and more allocation to sexual structures in full sunlight than in shade; (5) light determined the onset of sexual reproduction, and the genets in the shade required a smaller threshold size for sexual reproduction to occur than the plants in full sunlight; and (6) no evidence was found of trade-offs between clonal growth and sexual reproduction under different densities and light conditions at the genet level, and the positive correlation between two reproductive modes indicated that these are two integrated processes. Clonal growth in this species may be viewed as a growth strategy that tends to maximize genet fitness. PMID:24683463
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Xu, Cheng-Yuan; Schooler, Shon S; Van Klinken, Rieks D
2012-01-01
In contrast to seeds, high sensitivity of vegetative fragments to unfavourable environments may limit the expansion of clonal invasive plants. However, clonal integration promotes the establishment of propagules in less suitable habitats and may facilitate the expansion of clonal invaders into intact native communities. Here, we examine the influence of clonal integration on the morphology and growth of ramets in two invasive plants, Alternanthera philoxeroides and Phyla canescens, under varying light conditions. In a greenhouse experiment, branches, connected ramets and severed ramets of the same mother plant were exposed under full sun and 85% shade and their morphological and growth responses were assessed. The influence of clonal integration on the light reaction norm (connection×light interaction) of daughter ramets was species-specific. For A. philoxeroides, clonal integration evened out the light response (total biomass, leaf mass per area, and stem number, diameter and length) displayed in severed ramets, but these connection×light interactions were largely absent for P. canescens. Nevertheless, for both species, clonal integration overwhelmed light effect in promoting the growth of juvenile ramets during early development. Also, vertical growth, as an apparent shade acclimation response, was more prevalent in severed ramets than in connected ramets. Finally, unrooted branches displayed smaller organ size and slower growth than connected ramets, but the pattern of light reaction was similar, suggesting mother plants invest in daughter ramets prior to their own branches. Clonal integration modifies light reaction norms of morphological and growth traits in a species-specific manner for A. philoxeroides and P. canescens, but it improves the establishment of juvenile ramets of both species in light-limiting environments by promoting their growth during early development. This factor may be partially responsible for their ability to successfully colonize native plant communities.
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Oguchi, Riichi; Hiura, Tsutom; Hikosaka, Kouki
2017-08-01
Gap formation increases the light intensity in the forest understorey. The growth responses of seedlings to the increase in light availability show interspecific variation, which is considered to promote biodiversity in forests. At the leaf level, some species increase their photosynthetic capacity in response to gap formation, whereas others do not. Here we address the question of whether the interspecific difference in the photosynthetic response results in the interspecific variation in the growth response. If so, the interspecific difference in photosynthetic response would also contribute to species coexistence in forests. We also address the further relevant question of why some species do not increase their photosynthetic capacity. We assumed that some cost of photosynthetic plasticity may constrain acquisition of the plasticity in some species, and hypothesized that species with larger photosynthetic plasticity exhibit better growth after gap formation and lower survivorship in the shade understorey of a cool-temperate deciduous forest. We created gaps by felling canopy trees and studied the relationship between the photosynthetic response and the subsequent growth rate of seedlings. Naturally growing seedlings of six deciduous woody species were used and their mortality was examined for 8 years. The light-saturated rate of photosynthesis (Pmax) and the relative growth rate (RGR) of the seedlings of all study species increased at gap plots. The extent of these increases varied among the species. The stimulation of RGR over 4 years after gap formation was strongly correlated with change in photosynthetic capacity of newly expanded leaves. The increase in RGR and Pmax correlated with the 8-year mortality at control plots. These results suggest a trade-off between photosynthetic plasticity and the understorey shade tolerance. Gap-demanding species may acquire photosynthetic plasticity, sacrificing shade tolerances, whereas gap-independent species may acquire shade tolerances, sacrificing photosynthetic plasticity. This strategic difference among species would contribute to species coexistence in cool-temperate deciduous forests. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
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Campioli, Matteo; Leblans, Niki; Michelsen, Anders
2012-01-01
Most manipulation experiments simulating global change in tundra were short-term or did not measure plant growth directly. Here, we assessed the growth of three shrubs (Cassiope tetragona, Empetrum hermaphroditum and Betula nana) at a subarctic heath in Abisko (Northern Sweden) after 22 years of warming (passive greenhouses), fertilisation (nutrients addition) and shading (hessian fabric), and compare this to observations from the first decade of treatment. We assessed the growth rate of current-year leaves and apical stem (primary growth) and cambial growth (secondary growth), and integrated growth rates with morphological measurements and species coverage. Primary- and total growth of Cassiope and Empetrum were unaffected by manipulations, whereas growth was substantially reduced under fertilisation and shading (but not warming) for Betula. Overall, shrub height and length tended to increase under fertilisation and warming, whereas branching increased mostly in shaded Cassiope. Morphological changes were coupled to increased secondary growth under fertilisation. The species coverage showed a remarkable increase in graminoids in fertilised plots. Shrub response to fertilisation was positive in the short-term but changed over time, likely because of an increased competition with graminoids. More erected postures and large, canopies (requiring enhanced secondary growth for stem reinforcement) likely compensated for the increased light competition in Empetrum and Cassiope but did not avoid growth reduction in the shade intolerant Betula. The impact of warming and shading on shrub growth was more conservative. The lack of growth enhancement under warming suggests the absence of long-term acclimation for processes limiting biomass production. The lack of negative effects of shading on Cassiope was linked to morphological changes increasing the photosynthetic surface. Overall, tundra shrubs showed developmental plasticity over the longer term. However, such plasticity was associated clearly with growth rate trends only in fertilised plots. PMID:22511968
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SAM Photovoltaic Model Technical Reference 2016 Update
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gilman, Paul; DiOrio, Nicholas A; Freeman, Janine M
This manual describes the photovoltaic performance model in the System Advisor Model (SAM) software, Version 2016.3.14 Revision 4 (SSC Version 160). It is an update to the 2015 edition of the manual, which describes the photovoltaic model in SAM 2015.1.30 (SSC 41). This new edition includes corrections of errors in the 2015 edition and descriptions of new features introduced in SAM 2016.3.14, including: 3D shade calculator Battery storage model DC power optimizer loss inputs Snow loss model Plane-of-array irradiance input from weather file option Support for sub-hourly simulations Self-shading works with all four subarrays, and uses same algorithm for fixedmore » arrays and one-axis tracking Linear self-shading algorithm for thin-film modules Loss percentages replace derate factors. The photovoltaic performance model is one of the modules in the SAM Simulation Core (SSC), which is part of both SAM and the SAM SDK. SAM is a user-friedly desktop application for analysis of renewable energy projects. The SAM SDK (Software Development Kit) is for developers writing their own renewable energy analysis software based on SSC. This manual is written for users of both SAM and the SAM SDK wanting to learn more about the details of SAM's photovoltaic model.« less
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Pasquini, Sarah C; Wright, S Joseph; Santiago, Louis S
2015-07-01
Lianas are a prominent growth form in tropical forests, and there is compelling evidence that they are increasing in abundance throughout the Neotropics. While recent evidence shows that soil resources limit tree growth even in deep shade, the degree to which soil resources limit lianas in forest understories, where they coexist with trees for decades, remains unknown. Regardless, the physiological underpinnings of soil resource limitation in deeply shaded tropical habitats remain largely unexplored for either trees or lianas. Theory predicts that lianas should be more limited by soil resources than trees because they occupy the quick-return end of the "leaf economic spectrum," characterized by high rates of photosynthesis, high specific leaf area, short leaf life span, affinity to high-nutrient sites, and greater foliar nutrient concentrations. To address these issues, we asked whether soil resources (nitrogen, phosphorus, and potassium), alone or in combination, applied experimentally for more than a decade would cause significant changes in the morphology or physiology of tree and liana seedlings in a lowland tropical forest. We found evidence for the first time that phosphorus limits the photosynthetic performance of both trees and lianas in deeply shaded understory habitats. More importantly, lianas always showed significantly greater photosynthetic capacity, quenching, and saturating light levels compared to trees across all treatments. We found little evidence for nutrient x growth form interactions, indicating that lianas were not disproportionately favored in nutrient-rich habitats. Tree and liana seedlings differed markedly for six key morphological traits, demonstrating that architectural differences occurred very early in ontogeny prior to lianas finding a trellis (all seedlings were self-supporting). Overall, our results do not support nutrient loading as a mechanism of increasing liana abundance in the Neotropics. Rather, our finding that lianas always outperform trees, in terms of photosynthetic processes and under contrasting rates of resource supply of macronutrients, will allow lianas to increase in abundance if disturbance and tree turnover rates are increasing in Neotropical forests as has been suggested.
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Ciliary photoreceptors in the cerebral eyes of a protostome larva
2011-01-01
Background Eyes in bilaterian metazoans have been described as being composed of either ciliary or rhabdomeric photoreceptors. Phylogenetic distribution, as well as distinct morphologies and characteristic deployment of different photopigments (ciliary vs. rhabdomeric opsins) and transduction pathways argue for the co-existence of both of these two photoreceptor types in the last common bilaterian ancestor. Both receptor types exist throughout the Bilateria, but only vertebrates are thought to use ciliary photoreceptors for directional light detection in cerebral eyes, while all other invertebrate bilaterians studied utilize rhabdomeric photoreceptors for this purpose. In protostomes, ciliary photoreceptors that express c-opsin have been described only from a non-visual deep-brain photoreceptor. Their homology with vertebrate rods and cones of the human eye has been hypothesized to represent a unique functional transition from non-visual to visual roles in the vertebrate lineage. Results To test the hypothesis that protostome cerebral eyes employ exclusively rhabdomeric photoreceptors, we investigated the ultrastructure of the larval eyes in the brachiopod Terebratalia transversa. We show that these pigment-cup eyes consist of a lens cell and a shading pigment cell, both of which are putative photoreceptors, deploying a modified, enlarged cilium for light perception, and have axonal connections to the larval brain. Our investigation of the gene expression patterns of c-opsin, Pax6 and otx in these eyes confirms that the larval eye spots of brachiopods are cerebral eyes that deploy ciliary type photoreceptors for directional light detection. Interestingly, c-opsin is also expressed during early embryogenesis in all potential apical neural cells, becoming restricted to the anterior neuroectoderm, before expression is initiated in the photoreceptor cells of the eyes. Coincident with the expression of c-opsin in the presumptive neuroectoderm, we found that middle gastrula stage embryos display a positive photoresponse behavior, in the absence of a discrete shading pigment or axonal connections between cells. Conclusions Our results indicate that the dichotomy in the deployment of ciliary and rhabdomeric photoreceptors for directional light detection is not as clear-cut as previously thought. Analyses of brachiopod larval eyes demonstrate that the utilization of c-opsin expressing ciliary photoreceptors in cerebral eyes is not limited to vertebrates. The presence of ciliary photoreceptor-based eyes in protostomes suggests that the transition between non-visual and visual functions of photoreceptors has been more evolutionarily labile than previously recognized, and that co-option of ciliary and rhabdomeric photoreceptor cell types for directional light detection has occurred multiple times during animal evolution. In addition, positive photoresponse behavior in gastrula stage embryos suggests that a discrete shading pigment is not requisite for directional photoreception in metazoans. Scanning photoreception of light intensities mediating cell-autonomous changes of ciliary movement may represent an ancient mechanism for regulating locomotory behavior, and is likely to have existed prior to the evolution of eye-mediated directional light detection employing axonal connections to effector cells and a discreet shading pigment. PMID:21362157
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Shaded Relief Color Wrapped, Kamchatka Peninsula, Russia
NASA Technical Reports Server (NTRS)
2000-01-01
This shaded relief topographic image shows the western side of the volcanically active Kamchatka Peninsula, Russia. The data are from the first C-band mapping swath of the Shuttle Radar Topography Mission (SRTM). On the left side are five rivers, which flow northwest to the Sea of Okhotsk. These rivers are, from the south to north, Tigil, Amanina, Voyampolka, Zhilovaya, and Kakhtana. The broad, flat floodplains of the rivers are shown in yellow. These rivers are important spawning grounds for salmon. In the right side of the image is the Sredinnyy Khrebet, the volcanic mountain range that makes up the 3spine2 of the peninsula. The cluster of hills to the lower right is a field of small dormant volcanoes. High resolution SRTM topographic data will be used by geologists to study how volcanoes form and understand the hazards posed by future eruptions.This image was generated using topographic data from the Shuttle Radar Topography Mission. Colors show the elevation as measured by SRTM. Each cycle of colors (from red through green back to red) represents an equal amount of elevation difference (400 meters, or 1300 feet)similar to contour lines on a standard topographic map. This image contains about 2300 meters (7500 feet) of total relief. For the shading, a computer-generated artificial light source illuminates the elevation data to produce a pattern of light and shadows. Slopes facing the light appear bright, while those facing away are shaded. Shaded relief maps are commonly used in applications such as geologic mapping and land use planning.The Shuttle Radar Topography Mission (SRTM), launched on February 11,2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) and the German (DLR) and Italian (ASI) space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC.Size: 240 km (150 miles) x 122 km (77 miles) Location: 57.5 deg. North lat., 158.8 deg. East lon. Orientation: North at top Original Data Resolution: 30 meters (99 feet) Date Acquired: February 12, 2000 -
Fornaini, C; Lagori, G; Merigo, E; Meleti, M; Manfredi, M; Guidotti, R; Serraj, A; Vescovi, P
2013-01-01
Many dental bleaching techniques are now available, several of them using a laser source. However, the literature on the exact role of coherent light in the biochemical reaction of the whitening process is very discordant. The aims of this in vitro study were: (1) to compare two different laser sources, a KTP laser with a wavelength of 532 nm and a diode laser with a wavelength of 808 nm, during dental bleaching, and (2) to investigate the relationships among changes in gel temperature, tooth shade and hydrogen peroxide (HP) concentration during laser irradiation. Altogether, 116 bovine teeth were bleached using a 30% HP gel, some of them with gel only and others with gel plus one of the two lasers (532 or 808 nm) at two different powers (2 and 4 W). The KTP laser produced a significant shade variation with a minimal temperature increase. The diode laser led to a higher temperature increase with a greater reduction in HP concentration, but the change in shade was only statistically significant with a power of 4 W. At a power of 2 W, the KTP laser caused a greater change in shade than the diode laser. No significant correlations were found among temperature, HP concentration and shade variation. The KTP laser appears to provide better results with less dangerous thermal increases than the diode laser. This might call into question most of the literature affirming that the action of laser bleaching is by increasing the gel temperature and, consequently, the speed of the redox reaction. Further study is required to investigate the correlations between the parameters investigated and efficacy of the bleaching process.
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Illuminating light-dependent color shifts in core and veneer layers of dental all-ceramics.
Lee, Yong-Keun; Cha, Hyun-Suk; Yu, Bin
2014-09-01
The color of an object is perceived differently depending on the ambient light conditions. Since dental all-ceramic restorations are fabricated by building up several layers to reproduce the tooth shade, the optical properties of each layer should be optimized for successful shade reproduction. This study aimed to determine the separate contributions of the color shifts in each of the core and veneer layers of all-ceramics by switching the illuminating lights on the color shifts of layered ceramics. Specimens of seven kinds of core ceramics and the corresponding veneer ceramics for each core were fabricated with a layered thickness of 1.5 mm. A sintering ceramic was used as a reference core material. The Commission Internationale de l’Eclairage (CIE) color coordinates of core, veneer, and layered specimens were measured with a spectroradiometer under the CIE illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp) simulating lights. Color shifts of the layered specimens were primarily determined by the CIE a shifts (D65 to A switch) or by the CIE b shifts (D65 to F9 switch) of the veneer layer. The color coordinates shifts in the constituent layers differentially influenced those of the layered specimens by the kind of switched lights. Therefore, the optical properties of the constituent layers of all-ceramics should be controlled to reflect these findings.
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Illuminating light-dependent color shifts in core and veneer layers of dental all-ceramics
NASA Astrophysics Data System (ADS)
Lee, Yong-Keun; Cha, Hyun-Suk; Yu, Bin
2014-09-01
The color of an object is perceived differently depending on the ambient light conditions. Since dental all-ceramic restorations are fabricated by building up several layers to reproduce the tooth shade, the optical properties of each layer should be optimized for successful shade reproduction. This study aimed to determine the separate contributions of the color shifts in each of the core and veneer layers of all-ceramics by switching the illuminating lights on the color shifts of layered ceramics. Specimens of seven kinds of core ceramics and the corresponding veneer ceramics for each core were fabricated with a layered thickness of 1.5 mm. A sintering ceramic was used as a reference core material. The Commission Internationale de l'Eclairage (CIE) color coordinates of core, veneer, and layered specimens were measured with a spectroradiometer under the CIE illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp) simulating lights. Color shifts of the layered specimens were primarily determined by the CIE a* shifts (D65 to A switch) or by the CIE b* shifts (D65 to F9 switch) of the veneer layer. The color coordinates shifts in the constituent layers differentially influenced those of the layered specimens by the kind of switched lights. Therefore, the optical properties of the constituent layers of all-ceramics should be controlled to reflect these findings.
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NASA Astrophysics Data System (ADS)
Zheng, Ting; Chen, Jing M.
2017-01-01
The estimation of maximum carboxylation rate (Vcmax)-a critical determinant of the terrestrial carbon simulation-over space remains a challenging task. Inverting the Vcmax through the sunlit gross primary productivity (GPP) is a possible solution if the key parameter sunlit light use efficiency (ɛsun) could be acquired through remote sensing approaches. Previous studies have shown that the reflectance centered at 531 nm (R531) is very sensitive to variations of ɛsun and the photochemical reflectance index (PRI, the normalized difference index using R531 and R570) can be used as an indicator of ɛsun at the leaf level though little is known about the PRI-ɛsun relationship at the canopy level due to the mixing of sunlit and shaded leaves. In this study, the photochemical reflectance ratio (PRR, defined as the ratio between R531 and R570) is proposed to enable the sunlit-shaded separation of the canopy reflectance observations acquired from a tower based multi-angular platform. The canopy PRR can be expressed as the algebraic sum of sunlit PRR and shaded PRR weighted by the visible portions of the sunlit canopy and the shaded canopy respectively. The visible portions from different angles were simulated using the 4-Scale model and the sunlit (/shaded) PRR was acquired through solving a set of equations describing the canopy PRR obtained from different angles. The relationships between the sunlit PRR (PRRsun) and ɛsun were studied for a white pine stand (TP39) and a sugar maple stand (HA). At both sites, significant correlations between PRRsun and ɛsun were obtained (R2 = 0.57 (TP39), 0.585 (HA), p < 0.001), showing the ability of PRRsun to track the variation of ɛsun. Nevertheless, differences existed in the expressions of the PRRsun-ɛsun relationship between TP39 and HA, a general expression could not be found. Further studies have shown that introducing the normalized difference vegetation index (NDVI) to correct PRRsun (NDVI × PRRsun) largely removed such differences, suggesting the potential of the NDVI corrected PRRsun in estimating the ɛsun for different biomes.
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Clinical Study of the 3D-Master Color System among the Spanish Population.
Gómez-Polo, Cristina; Gómez-Polo, Miguel; Martínez Vázquez de Parga, Juan Antonio; Celemín-Viñuela, Alicia
2017-01-12
To study whether the shades of the 3D-Master System were grouped and represented in the chromatic space according to the three-color coordinates of value, chroma, and hue. Maxillary central incisor color was measured on tooth surfaces through the Easyshade Compact spectrophotometer using 1361 participants aged between 16 and 89. The natural (not bleached teeth) color of the middle thirds was registered in the 3D-Master System nomenclature and in the CIELCh system. Principal component analysis and cluster analysis were applied. 75 colors of the 3D-Master System were found. The statistical analysis revealed the existence of 5 cluster groups. The centroid, the average of the 75 samples, in relation to lightness (L*) was 74.64, 22.87 for chroma (C*), and 88.85 for hue (h*). All of the clusters, except cluster 3, showed significant statistical differences with the centroid for the three-color coordinates (p <0.001). The results of this study indicated that 75 shades in the 3D-Master System were grouped into 5 clusters following coordinates L*, C*, and h* resulting from the dental spectrophotometer Vita Easyshade compact. The shades that composed each cluster did not belong to the same lightness color dimension groups. There was no special uniform chromatic distribution among the colors of the 3D-Master System. © 2017 by the American College of Prosthodontists.
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Cytohistological study of the leaf structures of Panax ginseng Meyer and Panax quinquefolius L.
Lee, Ok Ran; Nguyen, Ngoc Quy; Lee, Kwang Ho; Kim, Young Chang; Seo, Jiho
2017-10-01
Both Panax ginseng Meyer and Panax quinquefolius are obligate shade-loving plants whose natural habitats are broadleaved forests of Eastern Asia and North America. Panax species are easily damaged by photoinhibition when they are exposed to high temperatures or insufficient shade. In this study, a cytohistological study of the leaf structures of two of the most well-known Panax species was performed to better understand the physiological processes that limit photosynthesis. Leaves of ginseng plants grown in soil and hydroponic culture were sectioned for analysis. Leaf structures of both Panax species were observed using a light microscope, scanning electron microscope, and transmission electron microscope. The mesostructure of both P. ginseng and P. quinquefolius frequently had one layer of noncylindrical palisade cells and three or four layers of spongy parenchymal cells. P. quinquefolius contained a similar number of stomata in the abaxial leaf surface but more tightly appressed enlarged grana stacks than P. ginseng contained. The adaxial surface of the epidermis in P. quinquefolius showed cuticle ridges with a pattern similar to that of P. ginseng . The anatomical leaf structure of both P. ginseng and P. quinquefolius shows that they are typical shade-loving sciophytes. Slight differences in chloroplast structure suggests that the two different species can be authenticated using transmission electron microscopy images, and light-resistant cultivar breeding can be performed via controlling photosynthesis efficiency.
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2003-01-01
Adis CommentsCerus Corporation is developing a variety of pathogen-inactivation systems, based on its Helinx technology. Three of the systems include amotosalen [S 59] as the inactivation compound. Amotosalen is a light-activated, DNA-, RNA-crosslinking psoralen compound, which is used to neutralise pathogens. The systems that utilise amotosalen are called the INTERCEPT Platelet System, the INTERCEPT Plasma System and the Allogeneic Cellular Immunotherapies (ACIT) system. The INTERCEPT Platelet System and INTERCEPT Plasma System are two of the systems that make up Cerus' INTERCEPT Blood Systems. The other system is the INTERCEPT Red Blood Cell System, which contains S 303 as the inactivation compound rather than amotosalen. Cerus' Helinx technology is able to prevent replication of DNA or RNA that is present in pathogens but not in the blood components being treated (e.g. platelets and plasma). When added to the blood components, the inactivation agent (in this case amotosalen) crosses the membrane or cell wall of the pathogen. When activated by light, amotosalen binds to the nucleic acid of the pathogen and prevents replication. This process prevents infection. INTERCEPT Platelet System: Cerus developed its INTERCEPT Platelet System, in collaboration with Baxter Healthcare, for use in blood centres. Platelets are an essential component of the coagulation process and may be required by patients undergoing surgery, cancer chemotherapy, transplantation or with bleeding disorders. The system is made up of an illuminator device, a compound absorption device and a processing kit containing amotosalen. In October 2002, the two companies announced that CE Mark approval had been received for the illuminator device for the INTERCEPT trade mark Blood System. Application of this technology to platelets is the first to be approved. As it is a new technology, the system is currently undergoing process validation in accordance with European Blood Bank GMP requirements. This validation process is currently being conducted in Denmark, France, Germany, Sweden and the UK. Marketing approval applications for the INTERCEPT Platelet System have also been submitted in Australia and Canada. In addition, the regulatory submission process has begun in the US. A phase III trial (EuroSPRITE) has been conducted in 103 patients in Europe with pooled random donor platelets. The platelets were collected using the buffy coat process. Another two 20-patient clinical trials have also been conducted in Europe, as well as a 40-patient trial using platelets collected by an apheresis collection system. Cerus has also conducted a phase III trial (SPRINT) in the US. The trial was conducted in 671 patients and used platelets collected by Baxter's apheresis collection system. INTERCEPT Plasma System: Cerus is also developing the INTERCEPT Plasma System in collaboration with Baxter Healthcare. The system also combines amotosalen, an illumination device and a compound absorption device. The two companies are currently preparing regulatory applications for the INTERCEPT Plasma System for the US. This application will be followed by a submission for CE Mark designation in Europe. Patients undergoing surgery, or transplantation, or with bleeding disorders, may require transfusions of plasma, often to control bleeding. The type of plasma is stored in frozen form and is called fresh frozen plasma (FFP). The INTERCEPT Plasma System is currently in phase IIIc development in the US. Patient enrolment in the trial is still ongoing. The trial is comparing INTERCEPT trade mark Plasma System treated versus untreated FFP in 30 patients with thrombotic thrombocytopenic purpura. Allogeneic Cellular Immunotherapies system: Cerus is also investigating the potential of its Helinx technology to improve the outcome of bone marrow transplantation procedures (used to treat leukaemia and lymphoma) through the treatmatment for many forms of leukaemia and is most effective when the donor is very closely matched to the patient for the major human leucocyte antigen (HLA) groups. As part of the transplant procedure, patients receive donor T cells to improve engraftment of the bone marrow transplant and strengthen the patient's immune system. However, donor T cells expose the patient to a high risk of contracting graft-versus-host disease (GVHD) caused by the proliferation of donor T cells, which attack the patient's healthy tissue. GVHD has a high mortality rate. Cerus' ACIT system has been developed to decrease the stringency of matching donors to patients and to inhibit the ability of donor T cells to cause GVHD. Light-activated amotosalen binds and permanently crosslinks DNA, preventing replication and thus stopping proliferation of donor T cells. Phase I development is currently being conducted in this area in the US using amotosalen as the neutralising agent. Cerus completed a phase I study investigating the safety and tolerability of its ACIT system in 2001. The study was conducted in patients receiving closely matched allogeneic bone marrow transplants for leukaemia. The company is currently collaborating with the National Marrow Donor Program in order to conduct further clinical studies in patients receiving bone marrow transplants from unmatched donors. Cerus has development, manufacturing and marketing agreements with Baxter covering the INTERCEPT Blood Systems, which includes the INTERCEPT Platelet system, the INTERCEPT Plasma System, and the INTERCEPT Red Blood Cell System. Under the terms of the agreements the two companies usually share the very early development activities. Cerus then conducts preclinical and clinical trials, while Baxter is responsible for the development of the systems disposables and devices. Following commercialisation Cerus will supply amotosalen and Baxter will supply the other components of the system and market, sell and distribute the system In January 2001, Cereus announced that it has entered into a collaborative agreement with the Pharmaceutical Division of Kirin Brewery in Japan to develop and market products for stem cell transplantation based on Cerus' proprietary Helinx technology. Under terms of the agreement, Cerus and Kirin will jointly develop the products. Cerus has received an initial license fee of US dollar 1 million. In addition it may receive up to US dollar 11 million in future payments upon achievement of development milestones. Kirin will also fund all development expenses for the Asia-Pacific region and a portion of Cerus' development activities aimed at obtaining product approval in the US. Kirin will market the products in the Asia-Pacific region, including Japan, China, Korea and Australia, and Cerus will receive a specified share of product revenues. Cerus will retain marketing rights in the rest of the world, including the US and Europe.
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NASA Astrophysics Data System (ADS)
Qin, Hao; Kumar, Rupesh; Alleaume, Romain
2015-10-01
We report here a new side channel attack on a practical continuous-variable (CV) quantum key distribution (QKD) system. Inspired by blinding attack in discrete-variable QKD, we formalize an attack strategy by inserting an external light into a CV QKD system implemented Gaussian-modulated coherent state protocol and show that our attack can compromise its practical security. In this attack, we concern imperfections of a balanced homodyne detector used in CV QKD. According to our analysis, if one inserts an external light into Bob's signal port, due to the imperfect subtraction from the homodyne detector, the leakage of the external light contributes a displacement on the homodyne signal which causes detector electronics saturation. In consequence, Bob's quadrature measurement is not linear with the quadrature sent by Alice. By considering such vulnerability, a potential Eve can launch a full intercept-resend attack meanwhile she inserts an external light into Bob's signal port. By selecting proper properties of the external light, Eve actively controls the induced displacement value from the inserted light which results saturation of homodyne detection. In consequence, Eve can bias the excess noise due to the intercept-resend attack and the external light, such that Alice and Bob believe their excess noise estimation is below the null key threshold and they can still share a secret key. Our attack shows that the detector loopholes also exist in CV QKD, and it seems influence all the CV QKD systems using homodyne detection, since all the practical detectors have finite detection range.
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NASA Astrophysics Data System (ADS)
Cheng, Y.; Hilker, T.; Middleton, E. M.; Coops, N. C.; Black, T. A.; Krishnan, P.
2007-12-01
The use of remotely sensed measurements collected by satellite, aircraft, and ground instruments to improve our understanding of ecological and hydrological processes were successfully demonstrated through the First International Satellite Land Surface Climatology (ISLSCP) Field Experiment [FIFE] and the BOReal Ecosystem- Atmosphere Study [BOREAS]. Following the concept of FIFE and BOREAS, we analyzed hyperspectral reflectance measurements collected at a coastal forest in British Columbia, Canada through the 2006 growing season. Diurnal and seasonal dynamics of the Photochemical Reflectance Index (PRI), a normalized difference spectral band-ratio index based on the xanthophyll signal at 531 nm which expresses protective responses to high light stress, were studied. This index has been shown to correlate with photosynthetic light use efficiency (LUE), an essential variable to model carbon uptake efficiency by plants. The measurements were collected from an automated system mounted on a flux tower under different sun and view geometries and atmospheric conditions through the 2006 growing season. Canopy structure was modeled using Light Detection and Ranging (LiDAR) technology, from which the sunlit and shaded canopy fractions were calculated as a function of incoming photosynthetically active radiation (PAR). These automated directional observations allowed us to: 1) investigate diurnal and seasonal changes of the PRI under different sky conditions; 2) compare the PRI with tower-based micro-meteorological measurements; and 3) separately investigate the PRI dynamics for sunlit and shaded partitions of the canopy which differ in response to their light environments. The data were categorized into six different groups based on two sky conditions (sunny and cloudy) and three illumination conditions (sunlit, shaded and intermediate). PRI showed a clear correlation with the LiDAR-based shadow fraction estimates. In April, the commencement of the growing season, clear diurnal dynamics of the PRI were observed for the sunlit foliage subset which showed lower (more negative) PRI values and a more dramatic change with sun altitude than shaded leaves. This was expected since leaves exposed to direct sunlight in their natural environment are likely under higher light stress. Consequently, diurnal changes of PRI and the differences among foliage groups were less obvious on overcast days because of limited direct irradiance. In August, when water availability was at its lowest of the year, the PRI exhibited relatively constant values throughout the day but with clear distinguishable values among the three leaf groups on sunny days. For other tower based measurements, PAR and GEP both showed clear seasonal patterns. Better estimates of the actual PAR intensity illuminating the sunlit and shaded canopy fractions were retrieved using the shadow fraction to reduce the above-canopy PAR. A clear seasonal pattern emerged for this revised PAR that distinguished among the groups and was also used to estimate LUE for the leaf groups. The correlation between PRI and LUE was confirmed. From these results, better understandings of the dynamics of carbon exchange bio-indicators that can be derived from directional hyperspectral reflectance measurements were demonstrated. Keywords: PRI, photosynthesis, PAR, GEP, LUE
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Light acclimation strategies change from summer green to spring ephemeral as wild-leek plants age.
Dion, Pierre-Paul; Brisson, Jacques; Fontaine, Bastien; Lapointe, Line
2016-05-01
Spring-ephemeral forest-herbs emerge early to take advantage of the high-light conditions preceding canopy closure; they complete their life cycle in a few weeks, then senesce as the tree canopy closes. Summer greens acclimate their leaves to shade and thus manage to maintain a net carbon gain throughout summer. Differences in phenology among life stages within a species have been reported in tree saplings, whose leaf activity may extend beyond the period of shade conditions caused by mature trees. Similar phenological acclimation has seldom been studied in forest herbs. We compared wild-leek bulb growth and leaf phenology among plants from seedling to maturity and from under 4 to 60% natural light availability. We also compared leaf chlorophyll content and chl a/b ratio among seedlings and adult plants in a natural population as an indicator of photosynthetic capacity and acclimation to light environment. Overall, younger plants senesced later than mature ones. Increasing light availability delayed senescence in mature plants, while hastening seedling senescence. In natural populations, only seedlings acclimated to the natural reduction in light availability through time. Wild-leek seedlings exhibit a summer-green phenology, whereas mature plants behave as true spring ephemerals. Growth appears to be more source-limited in seedlings than in mature plants. This modulation of phenological strategy, if confirmed in other species, would require a review of the current classification of species as either spring ephemerals, summer greens, wintergreens, or evergreens. © 2016 Botanical Society of America.