Sample records for plant transpiration rate

  1. Transpiration rates of rice plants treated with Trichoderma spp.

    NASA Astrophysics Data System (ADS)

    Doni, Febri; Anizan, I.; Che Radziah C. M., Z.; Yusoff, Wan Mohtar Wan

    2014-09-01

    Trichoderma spp. are considered as successful plant growth promoting fungi and have positive role in habitat engineering. In this study, the potential for Trichoderma spp. to regulate transpiration process in rice plant was assessed experimentally under greenhouse condition using a completely randomized design. The study revealed that Trichoderma spp. have potential to enhance growth of rice plant through transpirational processes. The results of the study add to the advancement of the understanding as to the role of Trichoderma spp. in improving rice physiological process.

  2. Triazoles : Their Effects on Net Photosynthetic Rate, Transpiration Rate and Stomatal Resistance in Setaria italica Plants grown in vivo

    Microsoft Academic Search

    Rhadha Bisht; Premlata Singariya; Navish Mathur; S. P. Bohra

    The effects of different concentration of triazoles (Triademefon (TDM) and Paclobutrazol (PBZ)) on net photosynthetic rate, transpiration rate and stomatal resistance were studied in Setaria italica plants grown under field conditions. Net photosynthetic rates (Pn), transpiration rates (Tr) and stomatal resistances (Sr) were recorded after second and fifth day of third treatment. Plants treated with triadimefon (5 and 10mg\\/liter) and

  3. Effect of transpiration rate on internal plant resistance to water flow 

    E-print Network

    Hailey, James Lester

    1971-01-01

    of LAi over all the leaves ~ The leaf area was approximated for test plant number one from similar plants, in age and size. For test plant numbers two through four, the leaf area was measured after each transpiration test ~ -1 -2 Transpiration Rate... measurements a change from 2 ~ 0 microvolts to 4 ~ 0 microvolts was used for the transit time measurement ~ The leaf diffusion resistance was measured on the plant being tested for transpiration rates For plant number one ~ two readings were taken only...

  4. Oscillations in Plant Transpiration

    Microsoft Academic Search

    Anders Johnsson

    Plants take up water via the root system and transpire water vapour through stomatal openings. Surrounding guard and subsidiary cells control the magnitude of the openings, enabling transpiration but also CO 2 transport for photosynthesis. Rhythmic transpiration reflects rhythmic cellular control by these cells and shows a range of short-term periods (typically from a few minutes to over 100 min.

  5. Zinc and copper uptake by plants under two transpiration rates. Part I. Wheat (Triticum aestivum L.).

    PubMed

    Tani, F H; Barrington, S

    2005-12-01

    To evaluate the environmental risk of irrigating crops with treated wastewater, an experiment was conducted using two growth chambers, each offering a different vapour pressure deficit (VPD) for high and low transpiration rates (TR), respectively. One of the two sets of 24 pots planted with 6 week old wheat (Triticum aestivum L.), was placed in each growth chamber, and irrigated in triplicates for 20 days with 8 Zn and Cu solutions (0 and 25 mg Zn/L combined with 0, 5, 15 and 30 mg Cu/L). Water losses from planted and non-planted pots served to measure evapo-transpiration and evaporation, respectively. Pots were monitored for Cu and Zn uptake by collecting three plants (shoot and grain)/pots after 0, 10 and 20 days, and roots in each pot after 20 days, and analyzing these plant parts for dry mass, and Cu and Zn levels. Transpiration rate was not affected by any Cu/Zn treatment, but Cu and Zn uptake increase with the time, irrigation solution level and higher TR, with the roots retaining most Cu and Zn, compared to the shoot followed by the grain. For the shoot and grain, Cu had a significant synergetic effect on Zn uptake, when Zn had slight but insignificant antagonistic effects on Cu uptake. For the roots, Cu and Zn had significant synergetic effect on each other. Regression equations obtained from the data indicate that Cu and Zn levels normally found in treated wastewater (0.08 mg/L) are 300 times lower than those used for the most concentrated experimental solutions (30 and 25 mg/L, respectively) and may, on a long term basis, be beneficial rather than toxic to wheat plants and do not acidify soil pH. PMID:16043273

  6. Zinc and copper uptake by plants under two transpiration rates. Part II. Buckwheat (Fagopyrum esculentum L.).

    PubMed

    Tani, F H; Barrington, S

    2005-12-01

    To evaluate the environmental risks of irrigating crops with treated wastewater, a study was undertaken to quantify heavy metal uptake by 4-week old buckwheat (Fagopyrum esculentum L.) plants during 18 days of irrigation with 8 different Cu and Zn solutions under two transpiration rates (TR). At 4 weeks, potted buckwheat plants were transferred into one of the two growth chambers, offering either a high or low vapour pressure deficit (VDP) for, respectively, a high or low TR. Triplicate pots received one of the 8 irrigation treatments containing one of two Zn levels (0 and 25 mg/L) combined with one of four Cu levels (0, 5, 10 and 15 mg/L). Daily TR were measured by weighing the evapo-transpired water lost from the planted pot, less was the evaporation loss measured from triplicate non-planted pots. After 0, 6, 12 and 18 days of treatment, the stems and leaves of three randomly selected plants were harvested and after 18 days, the roots were harvested to determine Cu and Zn uptake. The treatments did not affect TR in terms of dry plant mass, indicating the absence of toxic effects. Irrigating with Zn, without Cu, increased dry biomass production, whereas the lowest biomass occurred with 15 and 30 mg/L of Cu with and without 25 mg/L of Zn, respectively, because higher applications of heavy metal significantly reduced soil pH. Plant Cu and Zn uptake increased with TR. With higher levels of Cu, Zn uptake by buckwheat was significantly reduced, while Zn had a slight but non-significant impact on Cu uptake. Previously and in a study exposing wheat plants to the same conditions, Cu significantly increased Zn uptake, while Zn had a slight but insignificant negative effect on Cu uptake. The buckwheat roots contained the greatest levels of Cu and Zn, indicating their role in moderating heavy metal uptake. Also, both Cu and Zn had a synergetic effect on each other in terms of root levels, and a similar observation was made in the earlier similar experiment using wheat plants. Irrigating a buckwheat crop with treated wastewater, with more natural Cu and Zn levels of 0.08 mg/L, could be quite beneficial without endangering the quality of the crop and acidifying the soil pH. The most concentrated experimental solutions contained 300 times more Cu and Zn, to obtain measurable differences. PMID:16043272

  7. Just Breathe Green: Measuring Transpiration Rates

    NSDL National Science Digital Library

    2014-09-18

    Through multi-trial experiments, students are able to see and measure something that is otherwise invisible to them—seeing plants breathe. Student groups are given two small plants of native species and materials to enclose them after watering with colored water. After being enclosed for 5, 10 and 15 minutes, teams collect and measure the condensed water from the plants' "breathing," and then calculate the rates at which the plants breathe. A plant's breath is known as transpiration, which is the flow of water from the ground where it is taken up by roots (plant uptake) and then lost through the leaves. Students plot volume/time data for three different native plant species, determine and compare their transpiration rates to see which had the highest reaction rate and consider how a plant's unique characteristics (leaf surface area, transpiration rate) might figure into engineers' designs for neighborhood stormwater management plans.

  8. Field experiment on transpiration from isolated urban plants

    Microsoft Academic Search

    Aya Hagishima; Ken-Ich Narita; Jun Tanimoto

    2007-01-01

    The effect of pot plant density on plant transpiration rate was examined in a series of field experiments. Three spatial densities were created using 203 nearly homogeneous pot plants; the ratios of plant separation to plant height were 0Ð25, 0Ð5, and 3 for the 'high,' 'medium,' and 'low' groups respectively. The daily transpiration rate of 55 pot plants was measured

  9. Daily transpiration rates of woody species on drying soil.

    PubMed

    Sinclair, Thomas R; Holbrook, N Michelle; Zwieniecki, Maciej A

    2005-11-01

    Among annual plants, daily transpiration rates, expressed as a fraction of volumetric soil water content available for transpiration, show a common pattern in response to soil drying. Initially, as soil dries, there is little decrease in transpiration rate until water availability has fallen to about one third that at field capacity. With further soil drying, relative transpiration rate decreases in a more-or-less linear fashion until all available water has been used. Data previously obtained for perennial woody species have often been confounded by different methods for determining available soil water. In this study, we investigated the daily transpiration response to soil drying in five woody perennial species: Thuja plicata Donn ex D. Don, Acer rubrum L., Robinia pseudoacacia L., Hibiscus sp. and Ibex aquifolium L. Transpiration was unaffected by soil drying until the initial estimated transpirable soil water fraction had decreased to between 0.23 and 0.32 of that at field capacity. Beyond this point, transpiration rate declined linearly with available soil water fraction until reaching one fifth the rate observed in well-watered plants. With further soil drying, the relative transpiration rates remained between 10 and 20% of that observed in well-watered plants. Maintenance of transpiration at these rates with further soil drying was hypothesized to result from contributions to transpiration of water stored in plant tissues. After taking tissue water storage into account, it was estimated that transpiration was curtailed as the available soil water fraction fell to between 0.26 and 0.37 of that at field capacity, which is comparable to values reported for annual crop plants. PMID:16105814

  10. Transpiration: Water Movement Through Plants

    NSDL National Science Digital Library

    Tracy Sterling (New Mexico State University; )

    2005-09-23

    Learn the basics of transpiration -- the transportation of water through plants from soil to leaves to atmosphere -- with this playful animation created by weed physiologist Tracy Sterling and animator Matt Byrnes. Interactive features allow you to explore the process including how changing environmental conditions can impact how fast water moves.

  11. Zinc uptake by young wheat plants under two transpiration regimes

    SciTech Connect

    Grifferty, A.; Barrington, S.

    2000-04-01

    Treated wastewater for crop irrigation is an alternative for countries with a shortage of fresh water. Such practice requires strict wastewater application criteria and a better understanding of the effects of transpiration rate on plant heavy metal uptake. The experiment measured Zn uptake by young wheat plants (Triticum aestvum L.) grown in triplicated experimental pots and held in two growth chambers with constant environmental conditions (relative humidity, light and temperature) but with a different air water vapor pressure deficit to produce two different transpiration rates. After 5 wk of growth in a greenhouse, the plants were transferred to the controlled chambers and irrigated using a fertilized solution with five different levels of Zn: 0, 2, 10, 25, and 50 mg/L. These Zn levels were low enough to have no significant effect on plant growth and transpiration rate. The wheat plants started to produce their grain at 6 wk. Plants were collected at 0, 3, and 10 d of incubation in the controlled chambers and analyzed for dry matter and total Zn content. The pots were weighed daily to measure their transpiration rates. On Day 10, the remaining plants were collected and their roots, shoots, and grain were separated, weighed, dried, and analyzed for total Zn. Time and plant transpiration rate were found to affect significantly plant Zn uptake. The higher transpiration rate enhanced plant Zn uptake. The roots had the highest Zn uptake followed by the shoots and then the grain.

  12. Quality assessment of plant transpiration water

    NASA Technical Reports Server (NTRS)

    Macler, Bruce A.; Janik, Daniel S.; Benson, Brian L.

    1990-01-01

    It has been proposed to use plants as elements of biologically-based life support systems for long-term space missions. Three roles have been brought forth for plants in this application: recycling of water, regeneration of air and production of food. This report discusses recycling of water and presents data from investigations of plant transpiration water quality. Aqueous nutrient solution was applied to several plant species and transpired water collected. The findings indicated that this water typically contained 0.3-6 ppm of total organic carbon, which meets hygiene water standards for NASA's space applications. It suggests that this method could be developed to achieve potable water standards.

  13. Zinc uptake by young wheat plants under two transpiration regimes

    Microsoft Academic Search

    A. Grifferty; S. Barrington

    2000-01-01

    Treated wastewater for crop irrigation is an alternative for countries with a shortage of fresh water. Such practice requires strict wastewater application criteria and a better understanding of the effects of transpiration rate on plant heavy metal uptake. The experiment measured Zn uptake by young wheat plants (Triticum aestvum L.) grown in triplicated experimental pots and held in two growth

  14. Plant Transpiration and its Sensitivity to Increasing Carbon Dioxide Concentration at Leaf, Canopy and Regional Scales

    Microsoft Academic Search

    Xiwu Zhan

    1995-01-01

    This thesis assembles simulation models for plant transpiration and uses these models to investigate the sensitivity of transpiration rates to the elevation of atmospheric CO_2 concentration at leaf, canopy and regional scales. The leaf transpiration model assembly (LTMA) simulates stomatal conductance, leaf net photosynthesis, leaf boundary layer conductance, mass and energy transfer, leaf energy balance. The stomatal conductance model and

  15. Effects of gravity on transpiration of plant leaves.

    PubMed

    Hirai, Hiroaki; Kitaya, Yoshiaki

    2009-04-01

    To clarify effects of gravity on the water vapor exchange between plants and the ambient air, we evaluated the transpiration rate of plant leaves at 0.01, 1.0, and 2.0 g for 20 s each during parabolic airplane flights. The transpiration rates of a strawberry leaf and a replica leaf made of wet cloth were determined using a chamber method with humidity sensors. Absolute humidity at 3 and 8 mm below the lower surface of leaves was measured to evaluate the effect of gravity on humidity near leaves and estimate their transpiration rate. The transpiration rate of the replica leaf decreased by 42% with decreasing gravity levels from 1.0 to 0.01 g and increased by 31% with increasing gravity levels from 1.0 to 2.0 g. Absolute humidity near the intact strawberry leaf was 5 g m(-3) at ambient absolute humidity of 2.3 g m(-3) and gravity of 1.0 g. The absolute humidity increased by 2.5 g m(-3) with decreasing gravity levels from 1.0 to 0.01 g. The transpiration rate of the intact leaf decreased by 46% with decreasing gravity levels from 1.0 to 0.01 g and increased by 32% with increasing gravity levels from 1.0 to 2.0 g. We confirmed that the transpiration rate of leaves was suppressed by retarding the water vapor transfer due to restricted free air convection under microgravity conditions. PMID:19426314

  16. TRANSPIRATION RATES UNDER CONTROLLED ENVIRONMENT: SPECIES, HUMIDITY, AND AVAILABLE WATER AS VARIABLES

    Microsoft Academic Search

    ATWELL M. WALLACE; NORMAN B. STOUT

    There is little agreement in the rates of transpiration reported for common species of plants. Some of the discrepancies are due to methods of measurement which influence the rate of transpiration. Much of the confusion is undoubtedly due to the lack of adequate controls in many of the experiments which have been performed. On the basis of available data it

  17. Responses of gas exchange to reversible changes in whole-plant transpiration rate in two conifer species.

    PubMed

    Warren, C R; Livingston, N J; Turpin, D H

    2003-08-01

    This study examined the autonomy of branches with respect to the control of transpiration (E) in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western red cedar (Thuja plicata Donn) seedlings. Experiments were conducted on whole seedlings in a gas exchange system with a dual-cuvette that permitted independent manipulation and measurement of E in the upper and lower cuvettes. The value of E in one cuvette was manipulated by varying vapor pressure deficit (D) between 2.2 and 0.2 kPa, whereas D in the other cuvette was held at 2.2 kPa. Reducing D, while increasing stomatal conductance (gs), resulted in an overall decrease in E. In western red cedar, this decrease was almost threefold, and in Douglas-fir, approximately fourfold. In well-watered western red cedar, a reduction of whole-plant E by 46% (brought about by reducing D in the upper cuvette) resulted in a 12% increase in gs, a 12% increase in E and a 7% increase in net assimilation (A) of untreated foliage in the lower cuvette. Responses of gs, E and A of untreated foliage were similar irrespective of whether foliage was at the top or bottom of the seedling. When D in the treatment cuvette was restored to 2.2 kPa, gs, E and A of foliage in the untreated cuvette returned to pretreatment values. In contrast, in well-watered Douglas-fir, there was almost no change in gs, E or A of untreated foliage in one cuvette when D in the other cuvette was reduced, causing a 52% reduction in whole-plant E. However, similar manipulations on drought-stressed Douglas-fir led to 7-19% increases in gs, E and A of untreated foliage. In well-watered western red cedar, daytime leaf water potential (Psil) was maintained near -0.9 MPa over a wide range of D, whereas Psil of Douglas-fir decreased from -1.2 to -1.5 MPa as D increased. The tighter (isohydric) regulation of Psil in western red cedar may partly explain its greater stomatal response to D and variation in whole-plant E compared with Douglas-fir. In response to a reduction in E, measured increases in Psil and gs of unmanipulated foliage were less than predicted by a model assuming complete hydraulic connectivity of foliage. Our results suggest the foliage of both species is partially autonomous with respect to water. PMID:12865245

  18. Transpiration - Water Movement through Plants

    NSDL National Science Digital Library

    This lesson and its animation follows the journey of water through a plant from its uptake by roots to its evaporation from the leaf surface. How this journey is altered by plant characteristics such as stomata and cuticles as well as by changes in the environment will be described.

  19. Characterizing photosynthesis and transpiration of plant communities in controlled environments

    NASA Technical Reports Server (NTRS)

    Monje, O.; Bugbee, B.

    1996-01-01

    CO2 and water vapor fluxes of hydroponically grown wheat and soybean canopies were measured continuously in several environments with an open gas exchange system. Canopy CO2 fluxes reflect the photosynthetic efficiency of a plant community, and provide a record of plant growth and health. There were significant diurnal fluctuations in root and shoot CO2 fluxes, and in shoot water vapor fluxes. Canopy stomatal conductance (Gc) to water vapor was calculated from simultaneous measurements of canopy temperature (Tcan) and transpiration rates (Tr). Tr in the dark was substantial, and there were large diurnal fluctuations in both Gc and Tr. Canopy net Photosynthesis (Pnet), Tr, and Gc increased with increasing net radiation. Gc increased with Tr, suggesting that the stomata of plants in controlled environments (CEs) behave differently from field-grown plants. A transpiration model based on measurements of Gc was developed for CEs. The model accurately predicted Tr from a soybean canopy.

  20. How-to-Do-It: Using Computers in Measuring Transpiration Rate.

    ERIC Educational Resources Information Center

    Seligmann, Peter F.; Thompson, Steven R.

    1989-01-01

    Described is an activity in which a computer is used to acquire temperature and humidity data useful in investigating transpiration in plants. Materials and procedures are discussed and examples of results are presented. Factors which influence the rate of transpiration are discussed. (CW)

  1. Measuring Transpiration to Regulate Winter Irrigation Rates

    SciTech Connect

    Samuelson, Lisa [Auburn University] [Auburn University

    2006-11-08

    Periodic transpiration (monthly sums) in a young loblolly pine plantation between ages 3 and 6 was measured using thermal dissipation probes. Fertilization and fertilization with irrigation were better than irrigation alone in increasing transpiration of young loblolly pines during winter months, apparently because of increased leaf area in fertilized trees. Irrigation alone did not significantly increase transpiration compared with the non-fertilized and non-irrigated control plots.

  2. Whole-plant capacitance, embolism resistance and slow transpiration rates all contribute to longer desiccation times in woody angiosperms from arid and wet habitats.

    PubMed

    Gleason, Sean M; Blackman, Chris J; Cook, Alicia M; Laws, Claire A; Westoby, Mark

    2014-03-01

    Low water potentials in xylem can result in damaging levels of cavitation, yet little is understood about which hydraulic traits have most influence in delaying the onset of hydraulic dysfunction during periods of drought. We examined three traits contributing to longer desiccation times in excised shoots of 11 species from two sites of contrasting aridity: (i) the amount of water released from plant tissues per decrease in xylem water potential (W?); (ii) the minimum xylem water potential preceding acute water stress (defined as P50L; water potential at 50% loss of leaf conductance); and (iii) the integrated transpiration rate between the points of full hydration and P50L (Wtime). The time required for species to reach P50L varied markedly, ranging from 1.3 h to nearly 3 days. W?, P50L and Wtime all contributed significantly to longer desiccation times, explaining 28, 22 and 50% of the variance in the time required to reach P50L. Interestingly, these three traits were nearly orthogonal to one another, suggesting that they do not represent alternative hydraulic strategies, but likely trade off with other ecological strategies not evaluated in this study. The majority of water lost during desiccation (60-91%) originated from leaves, suggesting an important role for leaf capacitance in small plants when xylem water potentials decrease below -2 MPa. PMID:24550089

  3. Effects of transpiration rate on boron uptake by roots and translocation to shoots of table beets (Beta vulgaris L.)

    Microsoft Academic Search

    Mary C. Halbrooks; Lloyd A. Peterson; Theodore T. Kozlowski

    1986-01-01

    The effects of transpiration rate on B uptake by roots and translocation to shoots of table beet (Beta vulgaris L. cv. Red Ace) plants were studied under conditions of environmental control. Plants grown under high or low relative humidities (RH) had low or high rates of transpiration, respectively. Dry weights and B contents of shoots and roots were higher among

  4. The effectiveness of a foliar spray of kaolinite clay in reducing transpiration of cotton plants 

    E-print Network

    McMichael, Bobbie Lee

    1967-01-01

    environmental i'actors cause rapid and drastic changes in the transpiration. rate. The effect of these factors on plant water losses must be considered before trans- piration can be successfully reduced and controlled, Temperature, and solar radiation... be brought about by changes in the light intensity relations of plants in direct sunlight. Eaton (11) reported an inverse relationship between leaf temperatures and transpiration rates. Balls (2) has shown that leaf temperatures may be raised as much...

  5. Identifying the Relationship Between Plant Transpiration and Groundwater Table Depth

    NASA Astrophysics Data System (ADS)

    Liang, X.; Luo, X.; Huang, M.

    2014-12-01

    Impact of the groundwater on plant transpiration constitutes an important but not well understood aspect of the interactions between groundwater and the land surface, vegetation and atmosphere. The lack of understanding can be attributed to the limited observations and the complex nature of the problem as the mechanisms and processes involved are many and often tightly coupled. This study addresses such issues by using the Variable Infiltration Capacity Plus (VIC+) land surface model (LSM) in conjunction with a series of numerical experiments. The VIC+ model considers impacts of the hydraulic redistribution (HR), plant storage, photosynthesis, and groundwater table (GWT) dynamics on plant transpiration, and the interactions between plant transpiration and subsurface processes. Several groups of numerical experiments are performed using different combinations of precipitation conditions, vegetation types, soil types, groundwater table depths (GWTDs) and treatment of the HR process. We have found, in water limited climates, vegetation type, soil type and the HR process have strong impacts on transpiration - GWTD relationships. In particular when the HR is significant, such as in drier climates, the inclusion of HR process in the modeling is essential in establishing the correct relationship between the plant transpiration and GWTD, where an omission would result in a more linear-like relationship. In addition, under certain conditions, there exists a transition zone in the relationship between plant transpiration and GWTD, where transpiration drops abruptly as the groundwater table declines. Moreover, plant transpiration and groundwater become disconnected as the groundwater table declines further and lies below the transition zone.

  6. Transpiration rates of Carex Meyeriana in relation to micrometerological factors in a mountain valley wetland

    Microsoft Academic Search

    Huifeng Xu; Yanming Jin; Wei Deng; Kezhang Xu; Zhen Wang

    2009-01-01

    In order to reveal transpiration rates of wetland plants and its relationships to micrometerological factors in a mountain\\u000a valley wetland, relative humidity, air temperature, leaf temperature, soil temperature, photo flux density and transpiration\\u000a rates were measured once two hours in a Carex meyeriana wetland of the Changbai Mountain valley in dry (July) and wet (September) of 2003, respectively. Results showed

  7. [Plant transpiration in a maize/soybean intercropping system measured with heat balance method].

    PubMed

    Gao, Yang; Duan, Ai-wang; Qiu, Xin-qiang; Zhang, Jun-peng; Sun, Jing-sheng; Wang, He-zhou

    2010-05-01

    In an experimental field with maize/soybean strip intercropping, the transpiration of maize and soybean plants was measured with sap flow gauge based on heat balance method. In the intercropping system, the diurnal change of the sap flow rates of the plants fitted single-peak curve in sunny day and multi-peak curve in cloudy day. The plant sap flow rates were affected by many environmental factors, among which, solar radiation was the most important meteorological factor. The daily sap flow per maize or soybean plant showed significant correlations with solar radiation, air temperature, relative humidity, wind speed, and soil heat flux. During the observation period (June 1-30, 2008), the mean daily transpiration of maize plant (1.44 mm x d(-1)) was about 1.8 times of that of soybean plant (0.79 mm x d(-1)). Maize transpiration and soybean transpiration contributed 64% and 36% to the total transpiration of the intercropping system, respectively. Due to the spatial variation of stem diameter and leaf area, it would be necessary to install more sap flow gauges to accurately measure the sap flow of maize and soybean plants. PMID:20707114

  8. Barley yellow dwarf virus effects on cereal plant growth and transpiration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Little is known about how changes in root system biomass caused by barley yellow dwarf virus (BYDV) infection impact water relations in cereal plants. Objectives of these greenhouse studies were to elucidate virus infection effects on plant growth and apparent transpiration rate in oats (Avena sati...

  9. [Transpiration of banana plant measured by Granier method].

    PubMed

    Liu, Hai-jun; Cohen, Shabtai; Tanny, Josef; Huang, Guan-hua

    2007-01-01

    Banana plant is the highest herbaceous plant in the world. Because of the height, it's inconvenient to measure the transpiration (Tr) of banana plant in direct way. Some indirect methods such as soil water balance method or FAO 56 Crop Coefficient are commonly used to measure or calculate the Tr, but the obtained results are easily influenced by soil texture and water content, climatic condition, and agronomic practice. In the present paper, Granier method was used to measure the sap flow (SF) at the corm of banana in a greenhouse from November 15 to October 5, 2005, with the Tr measured by gravimetric method compared. The results showed that the daily SF measured by Granier method was about 4% lower than the daily Tr measured by gravimetric method, and the SF rate lagged the Tr rate about one hour. Granier method was not sensitive enough to measure SF when the daily Tr was less than 0.05 L x m(-2) active leaf area. Granier probes could work properly 2-3 days after installation, and the measurement error of Granier method could be much reduced when more sets of probes were installed and the mean values of SF rate were taken. PMID:17396496

  10. Response of stomatal numbers to CO2 and humidity: control by transpiration rate and abscisic acid.

    PubMed

    Lake, J A; Woodward, F I

    2008-07-01

    The observation that stomatal density (number mm(-2)) on herbarium leaves had decreased over the last century represents clear evidence that plants have responded to anthropogenic increases in CO2 concentration. The mechanism of the response has proved elusive but here it is shown that density responses to both CO2 concentration and humidity are correlated with changes in whole-plant transpiration and leaf abscisic acid (ABA) concentration. The transpiration rate of a range of accessions of Arabidopsis thaliana was manipulated by changing CO2 concentration, humidity and by exogenous application of ABA. Stomatal density increased with transpiration and leaf ABA concentration. A common property of signal transduction systems is that they rapidly lose their ability to respond to the co-associated stimulus. Pathways of water movement within the plant are connected and so variations in supply and demand can be signalled throughout the plant directly, modifying stomatal aperture of mature leaves and stomatal density of developing leaves. Furthermore, the system identified here does not conform to the loss of ability to respond. A putative mechanism is proposed for the control of stomatal density by transpiration rate and leaf ABA concentration. PMID:19086289

  11. Decreasing Transpiration of Field Plants by Chemical Closure of Stomata

    Microsoft Academic Search

    P. E. Waggoner

    1964-01-01

    CHEMICALS which close stomata have been described by Zelitch1. When sprayed on leaf surfaces, the compounds decrease transpiration and photosynthesis of detached leaves2 and of maize plants in soil3 by increasing the diffusion resistance of stomata. When sprayed on intact tobacco plants in the greenhouse2 or on sunflowers growing in bins of soil outdoors3, the compounds reduced the loss of

  12. Integration of Transpiration Rate, Photosynthesis, Abscisic-Acid Signaling, and Guard-Cell Gene Expression

    Microsoft Academic Search

    Danielle M. Sherdan

    2007-01-01

    Guard cells in the leaf epidermis regulate transpiration rate (E) and carbon dioxide uptake by adjusting stomatal aperture size. Sucrose (suc) is a recent product of photosynthesis that accumulates around guard cells during transpiration. Similarly, abscisic acid (ABA) is a potent regulator of guard cell physiology that can be transported to guard cells via the transpiration stream. I tested the

  13. A method to determine plant water source using transpired water

    NASA Astrophysics Data System (ADS)

    Menchaca, L. B.; Smith, B. M.; Connolly, J.; Conrad, M.; Emmett, B.

    2007-04-01

    A method to determine the stable isotope ratio of a plant's water source using the plant's transpired water is proposed as an alternative to standard xylem extraction methods. The method consists of periodically sampling transpired waters from shoots or leaves enclosed in sealed, transparent bags which create a saturated environment, preclude further evaporation and allow the progressive mixing of evaporated transpired water and un-evaporated xylem water. The method was applied on trees and shrubs coexisting in a non-irrigated area where stable isotope ratios of local environmental waters are well characterized. The results show Eucalyptus globulus (tree) and Genista monspessulana (shrub) using water sources of different isotopic ratios congruent with groundwater and soil water respectively. In addition, tritium concentrations indicate that pine trees (Pinus sylvestris) switch water source from soil water in the winter to groundwater in the summer. The method proposed is particularly useful in remote or protected areas and in large scale studies related to water management, environmental compliance and surveillance, because it eliminates the need for destructive sampling and greatly reduces costs associated with laboratory extraction of xylem waters from plant tissues for isotopic analyses.

  14. Plant transpiration and net entropy exchange on the Earth’s surface in a Czech watershed

    Microsoft Academic Search

    Miroslav Tesa?; ?ubomír Lichner; Jan ?ermák

    2007-01-01

    The influence of plant transpiration on the entropy exchange was quantified as associated with the degradation of solar energy\\u000a on the Earth’s surface covered by plants. Two surfaces were studied: (1) productive surface — plant transpiration taken as\\u000a equal to the potential one, (2) non-productive surface — plant transpiration taken as equal to zero. The entropy exchanges\\u000a associated with the

  15. Investigation of transpiration and/or accumulation of volatile organic compounds (VOCs) by plants

    SciTech Connect

    Goodrich, R.L.; Carlsen, T.M. [Lawrence Livermore National Lab., CA (United States)

    1994-12-31

    The authors are in the planning stages of an investigation to explore plant transpiration and/or accumulation of VOCs (primarily Trichloroethylene [TCE]) by native vegetation. Such processes may naturally remediate these compounds in shallow ground water. To adequately quantify the amount of TCE in ground water prior to vegetation uptake, the authors will first install shallow piezometers adjacent to existing vegetation. Vegetation sampling will be synchronized with the ground water sampling to establish baseline conditions. They will conduct a literature search to identify potential structures with high lipid content in the plant species of interest (Populus fremontii, Typha latifolia and Salix). To investigate VOC distribution in the plant, individual morphological segments of the plant will be analyzed. The vegetation will be dissected into distinct segments, such as the vegetative (stem and leaves) and reproductive structures, to determine the possible accumulation of TCE at various points within the plant. They have completed preliminary development of analytical methods that they will use to analyze the samples. In the field, plastic (Tedlar) bags will be tightly secured onto the vegetation and a direct head-space analysis will be conducted on the bags, thus providing information on the rate of transpiration compared to the actual accumulation of VOCs within the plant. At a minimum, they expect to document VOC losses from the ground water via plant transpiration.

  16. A Transpiration Experiment Requiring Critical Thinking Skills.

    ERIC Educational Resources Information Center

    Ford, Rosemary H.

    1998-01-01

    Details laboratory procedures that enable students to understand the concept of how differences in water potential drive the movement of water within a plant in response to transpiration. Students compare transpiration rates for upper and lower surfaces of leaves. (DDR)

  17. Partial phenotypic reversion of ABA-deficient flacca tomato (Solanum lycopersicum) scions by a wild-type rootstock: normalizing shoot ethylene relations promotes leaf area but does not diminish whole plant transpiration rate

    Microsoft Academic Search

    Ian C. Dodd; Julian C. Theobald; Sarah K. Richer; William J. Davies

    2009-01-01

    To evaluate the role of root-synthesized ABA in regulating growth and stomatal behaviour under well-watered conditions, isogenic wild-type (WT) and ABA-deficient flacca (flc) tomato (Solanum lycopersicum) were reciprocally and self-grafted just below the cotyledonary node. Since flc scions had lower leaf water potentials due to higher transpiration rates, a subset of all graft combinations was grown under a shoot misting

  18. Transpiration and water use by cotton plants as affected by the soil application of fatty alcohols 

    E-print Network

    Rhoads, Frederick Milton

    1963-01-01

    Alcohols Rate of Growth and Fruit Production 33 V. Summary and Conclusions 40 VI. Literature Cited VII. Appendix 43 46 Legend A-l, Statistical Analysis of the Average Daily Transpiration A-2, Statistical Analysis of the Transpiration Ratio A-3... II. Review of the Literature III, . Materials and Methods Experimental Design and Materials Used Measurements 12 IV. Results and Discussion 20 Transpiration 20 Soil Moisture Content 27 Leaf Area Measurement 31 Decomposition Rates of Fatty...

  19. Effects of carbon dioxides and/or relative humidity on the growth and the transpiration of several plants.

    PubMed

    Shimizu, H; Fujinuma, Y; Omasa, K

    1996-12-01

    In order to estimate the effects of "global warming" on plants, the effects of carbon dioxide concentration (500 ppm or 1000 ppm CO2) and/or relative humidity (37% or 79% RH) on the growth and the transpiration of several C3 plants and a C4 plant (corn) were investigated by using artificially-lighted growth cabinets. The dry weight growths of all species, especially C3 plants, were accelerated by an elevated concentration of CO2, but were reduced, especially tomato and eggplant, by lowering RH. The leaf area growths of tomato and eggplant were accelerated by a high CO2, while those of all species were reduced by a low RH. A high CO2 increased net assimilation rates (NARs) more than relative growth rates (RGRs) of all species. It decreased leaf area ratio (LAR) due to a decrease in specific leaf area (SLA). A low RH decreased RGRs of all plants. while it affected NARs or LARs of some species. The partitioning of dry matter was insignificantly affected by CO2 or RH. Effects of CO2 on the transpiration rate were not observed clearly with C3 species, though a high CO2 decreased the transpiration of corn obviously. A low RH increased the transpiration rates of all species. From these results, the water use efficiencies of many plants, especially corn were kept at a high level by a high CO2 with a high RH condition. The interactive effects between CO2 and RH on the growth and the transpiration were insignificantly observed in these plants. PMID:11541568

  20. The use of plant-transpired water to monitor subsurface tritium contamination

    SciTech Connect

    Monheit, S.G. [Univ. of San Francisco, CA (United States)

    1995-12-31

    The experimental technique of sampling plant-transpired water to detect and monitor subsurface tritium contamination in soil water and groundwater was implemented in an area surrounding the National Tritium Labeling Facility (NTLF) at Lawrence Berkeley National Laboratory (LBNL). Data collected using the transpiration technique were compared with data collected by conventional soil water and groundwater sampling methods, to evaluate its application as an environmental monitoring tool. Tritium activity in the different ecological waters were compared for thirteen delineated areas. For statistical analysis of spatial and temporal trends, plant sampling stations were categorized as either deep or shallow rooted. Plant-transpired water samples were found to have consistently higher tritium activity than soil water or groundwater in leach localized area. Tritium activity in plant-transpired water diminished with distance from the emission source. Wet season plant-transpired water samples registered statistically significantly higher tritium activity than dry season samples, with the greatest variation from shallow rooted plants. The results of this study indicate that plant-transpired water sampling is a valuable tool in environmental monitoring and may be more sensitive in the detection of subsurface tritium contamination than conventional lysimeter or monitoring well sampling. Plant-transpired water sampling is a promising tool for investigating tritium distribution and concentration in contaminated soil water and groundwater.

  1. Differential effect of transpiration and Ca supply on growth and Ca concentration of tomato plants

    Microsoft Academic Search

    Francisco M. del Amor; Leo F. M. Marcelis

    2006-01-01

    To determine the extent to which transpiration and Ca concentration in the nutrient solution affect the regulation of growth, two independent experiments with young tomato plants were carried out under fully controlled climate conditions and grown hydroponically. The first experiment consisted of the regulation of transpiration by three levels of relative air humidity (RH): 50%, 70% (control) and 95% (corresponding

  2. NOTE / NOTE Transpiration-dependent passive silica

    E-print Network

    Kitajima, Kaoru

    manipulated transpiration rates by changing humidity and air movements around pot-grown plants receivingNOTE / NOTE Transpiration-dependent passive silica accumulation in cucumber (Cucumis sativus) under transport Si, through transpiration, from soils to shoots, while others actively transport silica

  3. Nighttime transpiration in woody plants from contrasting ecosystems.

    PubMed

    Dawson, Todd E; Burgess, Stephen S O; Tu, Kevin P; Oliveira, Rafael S; Santiago, Louis S; Fisher, Joshua B; Simonin, Kevin A; Ambrose, Anthony R

    2007-04-01

    It is commonly assumed that transpiration does not occur at night because leaf stomata are closed in the dark. We tested this assumption across a diversity of ecosystems and woody plant species by various methods to explore the circumstances when this assumption is false. Our primary goals were: (1) to evaluate the nature and magnitude of nighttime transpiration, E(n), or stomatal conductance, g(n); and (2) to seek potential generalizations about where and when it occurs. Sap-flow, porometry and stable isotope tracer measurements were made on 18 tree and eight shrub species from seven ecosystem types. Coupled with environmental data, our findings revealed that most of these species transpired at night. For some species and circumstances, nighttime leaf water loss constituted a significant fraction of total daily water use. Our evidence shows that E(n) or g(n) can occur in all but one shrub species across the systems we investigated. However, under conditions of high nighttime evaporative demand or low soil water availability, stomata were closed and E(n) or g(n) approached zero in eleven tree and seven shrub species. When soil water was available, E(n) or g(n) was measurable in these same species demonstrating plasticity for E(n) or g(n). We detected E(n) or g(n) in both trees and shrubs, and values were highest in plants from sites with higher soil water contents and in plants from ecosystems that were less prone to atmospheric or soil water deficits. Irrespective of plant or ecosystem type, many species showed E(n) or g(n) when soil water deficits were slight or non-existent, or immediately after rainfall events that followed a period of soil water deficit. The strongest relationship was between E(n) or g(n) and warm, low humidity and (or) windy (> 0.8 m s(-1)) nights when the vapor pressure deficit remained high (> 0.2 kPa in wet sites, > 0.7 kPa in dry sites). Why E(n) or g(n) occurs likely varies with species and ecosystem type; however, our data support four plausible explanations: (1) it may facilitate carbon fixation earlier in the day because stomata are already open; (2) it may enhance nutrient supply to distal parts of the crown when these nutrients are most available (in wet soils) and transport is rapid; (3) it may allow for the delivery of dissolved O(2) via the parenchyma to woody tissue sinks; or (4) it may occur simply because of leaky cuticles in older leaves or when stomata cannot close fully because of obstructions from stomatal (waxy) plugs, leaf endophytes or asymmetrical guard cells (all non-adaptive reasons). We discuss the methodological, ecophysiological, and theoretical implications of the occurrence of E(n) or g(n) for investigations at a variety of scales. PMID:17241998

  4. Na+ accumulation in root symplast of sunflower plants exposed to moderate salinity is transpiration-dependent.

    PubMed

    Quintero, José Manuel; Fournier, José María; Benlloch, Manuel; Rodríguez-Navarro, Alonso

    2008-08-25

    Twenty-day-old sunflower plants (Helianthus annuus L. cv Sun-Gro 380) grown hydroponically under controlled conditions were used to study the effect of transpiration on Na(+) compartmentalization in roots. The plants were exposed to low Na(+) concentrations (25 mM NaCl) and different environmental humidity conditions over a short time period (8.5 h). Under these conditions, Na(+) was accumulated primarily in the root, but only the Na(+) accumulated in the root symplast was dependent on transpiration, while the Na(+) accumulated in both the shoot and the root apoplast exhibited a low transpiration dependence. Moreover, Na(+) content in the root apoplast was reached quickly (0.25 h) and increased little with time. These results suggest that, in sunflower plants under moderate salinity conditions, Na(+) uptake in the root symplast is mediated by a transport system whose activity is enhanced by transpiration. PMID:18166246

  5. A microfluidic pump/valve inspired by xylem embolism and transpiration in plants.

    PubMed

    Jingmin, Li; Chong, Liu; Zheng, Xu; Kaiping, Zhang; Xue, Ke; Liding, Wang

    2012-01-01

    In plants, transpiration draws the water upward from the roots to the leaves. However, this flow can be blocked by air bubbles in the xylem conduits, which is called xylem embolism. In this research, we present the design of a biomimetic microfluidic pump/valve based on water transpiration and xylem embolism. This micropump/valve is mainly composed of three parts: the first is a silicon sheet with an array of slit-like micropores to mimic the stomata in a plant leaf; the second is a piece of agarose gel to mimic the mesophyll cells in the sub-cavities of a stoma; the third is a micro-heater which is used to mimic the xylem embolism and its self-repairing. The solution in the microchannels of a microfluidic chip can be driven by the biomimetic "leaf" composed of the silicon sheet and the agarose gel. The halting and flowing of the solution is controlled by the micro-heater. Results have shown that a steady flow rate of 1.12 µl/min can be obtained by using this micropump/valve. The time interval between the turning on/off of the micro-heater and the halt (or flow) of the fluid is only 2?3 s. This micropump/valve can be used as a "plug and play" fluid-driven unit. It has the potential to be used in many application fields. PMID:23209709

  6. A Microfluidic Pump/Valve Inspired by Xylem Embolism and Transpiration in Plants

    PubMed Central

    Jingmin, Li; Chong, Liu; Zheng, Xu; Kaiping, Zhang; Xue, Ke; Liding, Wang

    2012-01-01

    In plants, transpiration draws the water upward from the roots to the leaves. However, this flow can be blocked by air bubbles in the xylem conduits, which is called xylem embolism. In this research, we present the design of a biomimetic microfluidic pump/valve based on water transpiration and xylem embolism. This micropump/valve is mainly composed of three parts: the first is a silicon sheet with an array of slit-like micropores to mimic the stomata in a plant leaf; the second is a piece of agarose gel to mimic the mesophyll cells in the sub-cavities of a stoma; the third is a micro-heater which is used to mimic the xylem embolism and its self-repairing. The solution in the microchannels of a microfluidic chip can be driven by the biomimetic “leaf” composed of the silicon sheet and the agarose gel. The halting and flowing of the solution is controlled by the micro-heater. Results have shown that a steady flow rate of 1.12 µl/min can be obtained by using this micropump/valve. The time interval between the turning on/off of the micro-heater and the halt (or flow) of the fluid is only 2?3 s. This micropump/valve can be used as a “plug and play” fluid-driven unit. It has the potential to be used in many application fields. PMID:23209709

  7. [Diurnal dynamics of photosynthetic and transpiration rates of alfalfa under dry farming and their relationships with environmental factors].

    PubMed

    Liu, Yuhua; Shi, Ji'an; Jia, Zhikuan; Han, Qingfang

    2006-10-01

    In this paper, the diurnal dynamics of photosynthetic rate (Pn) and transpiration rate ( Tr) of four years planted alfalfa under dry farming, as well as those of photosynthetic active radiation (PAR) , CO2 concentration in field ( Ca ) , relative humidity (RH) and air temperature ( Ta) were measured, and the relationships between the diurnal dynamics of Pn, Tr and climatic factors were analyzed by correlation coefficient, path coefficient, and decision coefficient analyses. The results showed that T. had the greatest effect on the diurnal dynamics of Pn , while RH, PAR and C, affected P,, mainly through their acting on Ta PAR had the greatest effect on the diurnal changes of Tr, and RH, Ta and Ca affected Tr indirectly by acting on PAR. For the characteristics of photosynthesis and transpiration, PAR was the primary determining factor, and Ta was the main limiting factor. PMID:17209375

  8. Transpiration, Water Absorption, and Internal Water Balance of Cotton Plants as Affected by Light and Changes in Saturation Deficit 1

    PubMed Central

    Ehrler, W. L.; van Bavel, C. H. M.; Nakayama, F. S.

    1966-01-01

    In controlled environment studies of cotton plants (Gossypium barbadense L.) a light-induced acceleration of transpiration upset the water balance established in the dark because of a lag in water absorption. A plant-water deficit could be generated either by sudden illumination at a given saturation deficit (sd) of the air, or by raising the sd in conjunction with illumination, without different effects. Direct water balance measurements were confirmed in every experiment by beta ray gauge detection of changes in leaf-water content resulting from unequal gain and loss of water by the whole plant. Recovery from the initial loss of turgidity always was faster and more complete at the higher than at the lower values of sd. Recovery occurred even in the light at the higher values of sd, but was enhanced by return to darkness and a lower sd, which at times resulted in superhydration. Rehydration in the light could be attributed to at least 2 processes: A) a diminished transpiration rate if earlier water loss was sufficient to induce stomatal closure, and B) an increased rate of water absorption. The data suggest that a water deficit, temporary or persisting, does not cause a significantly lowered transpiration rate; thus, recovery must depend on increased absorption. The communicative link between the 2 processes appears weak, transmitting strong signals only. PMID:16656235

  9. Effect of carbon dioxide, osmotic potential of nutrient solution, and light intensity on transpiration and resistance to flow of water in pepper plants

    Microsoft Academic Search

    B. E. Janes

    1970-01-01

    The rate of transpiration, temperature of the leaves, and relative water content of leaves of pepper plants were measured in a small chamber in which the temperature, relative humidity, and carbon dioxide concentration of recirculated air were controlled and measured. The data reported were obtained by noting the response of pepper plants to all combinations of the following treatments: high

  10. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf

    PubMed Central

    Simonin, Kevin A.; Burns, Emily; Choat, Brendan; Barbour, Margaret M.; Dawson, Todd E.; Franks, Peter J.

    2015-01-01

    Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (??stem–leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO2 concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO2 concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO2 on g s. The positive relationship between k leaf and E minimized variation in ??stem–leaf. This enables leaves to minimize variation in ?leaf and maximize g s and CO2 assimilation rate over the diurnal course of evaporative demand. PMID:25547915

  11. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf.

    PubMed

    Simonin, Kevin A; Burns, Emily; Choat, Brendan; Barbour, Margaret M; Dawson, Todd E; Franks, Peter J

    2015-03-01

    Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (??stem-leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO? concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO? concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO? on g s. The positive relationship between k leaf and E minimized variation in ??stem-leaf. This enables leaves to minimize variation in ?leaf and maximize g s and CO? assimilation rate over the diurnal course of evaporative demand. PMID:25547915

  12. FPGA-based Fused Smart Sensor for Real-Time Plant-Transpiration Dynamic Estimation

    PubMed Central

    Millan-Almaraz, Jesus Roberto; de Jesus Romero-Troncoso, Rene; Guevara-Gonzalez, Ramon Gerardo; Contreras-Medina, Luis Miguel; Carrillo-Serrano, Roberto Valentin; Osornio-Rios, Roque Alfredo; Duarte-Galvan, Carlos; Rios-Alcaraz, Miguel Angel; Torres-Pacheco, Irineo

    2010-01-01

    Plant transpiration is considered one of the most important physiological functions because it constitutes the plants evolving adaptation to exchange moisture with a dry atmosphere which can dehydrate or eventually kill the plant. Due to the importance of transpiration, accurate measurement methods are required; therefore, a smart sensor that fuses five primary sensors is proposed which can measure air temperature, leaf temperature, air relative humidity, plant out relative humidity and ambient light. A field programmable gate array based unit is used to perform signal processing algorithms as average decimation and infinite impulse response filters to the primary sensor readings in order to reduce the signal noise and improve its quality. Once the primary sensor readings are filtered, transpiration dynamics such as: transpiration, stomatal conductance, leaf-air-temperature-difference and vapor pressure deficit are calculated in real time by the smart sensor. This permits the user to observe different primary and calculated measurements at the same time and the relationship between these which is very useful in precision agriculture in the detection of abnormal conditions. Finally, transpiration related stress conditions can be detected in real time because of the use of online processing and embedded communications capabilities. PMID:22163656

  13. FPGA-based fused smart sensor for real-time plant-transpiration dynamic estimation.

    PubMed

    Millan-Almaraz, Jesus Roberto; de Jesus Romero-Troncoso, Rene; Guevara-Gonzalez, Ramon Gerardo; Contreras-Medina, Luis Miguel; Carrillo-Serrano, Roberto Valentin; Osornio-Rios, Roque Alfredo; Duarte-Galvan, Carlos; Rios-Alcaraz, Miguel Angel; Torres-Pacheco, Irineo

    2010-01-01

    Plant transpiration is considered one of the most important physiological functions because it constitutes the plants evolving adaptation to exchange moisture with a dry atmosphere which can dehydrate or eventually kill the plant. Due to the importance of transpiration, accurate measurement methods are required; therefore, a smart sensor that fuses five primary sensors is proposed which can measure air temperature, leaf temperature, air relative humidity, plant out relative humidity and ambient light. A field programmable gate array based unit is used to perform signal processing algorithms as average decimation and infinite impulse response filters to the primary sensor readings in order to reduce the signal noise and improve its quality. Once the primary sensor readings are filtered, transpiration dynamics such as: transpiration, stomatal conductance, leaf-air-temperature-difference and vapor pressure deficit are calculated in real time by the smart sensor. This permits the user to observe different primary and calculated measurements at the same time and the relationship between these which is very useful in precision agriculture in the detection of abnormal conditions. Finally, transpiration related stress conditions can be detected in real time because of the use of online processing and embedded communications capabilities. PMID:22163656

  14. Characteristics of Encelia species differing in leaf reflectance and transpiration rate under common garden conditions

    Microsoft Academic Search

    James R. Ehleringer; Craig S. Cook

    1990-01-01

    The performance of coastal and desert species of Encelia (Asteraceae) were evaluated through common garden growth observations. The obectives of the study were to evaluate the roles of leaf features, thought to be of adaptive value (increased leaf reflectance and\\/or transpirational cooling), on plant growth in the hot, arid, desert garden versus their impact on growth under cooler, relatively more

  15. Hydraulic limits on maximum plant transpiration and the emergence of the safetyefficiency trade-off

    E-print Network

    Jackson, Robert B.

    Hydraulic limits on maximum plant transpiration and the emergence of the safety­efficiency trade.12126 Key words: hydraulic limitation, safety­ efficiency trade-off, soil­plant­atmosphere model, trait hydraulics constrain ecosystem productivity by setting physical limits to water transport and hence carbon

  16. Plant canopy transpiration in bioregenerative life support systems - The link between mechanistic and empirical models

    NASA Technical Reports Server (NTRS)

    Sirko, Robert J.; Mccormack, Ann C.; Edeen, Marybeth A.

    1992-01-01

    A model of water transpiration in a plant canopy that combines two approaches is presented. The first approach is to account for underlying physical processes, while the second is to empirically incorporate transpiration data now being generated at the Johnson Center Variable Pressure Growth Chamber. The two approaches, physical modeling and data analysis, make it possible to produce a model that is more robust than either the standard first-principles model or a straightforward empirical model. It is shown that the present transpiration model is able to efficiently capture the dynamic behavior of the plant canopy over the entire range of environmental parameters now envisioned to be important in an operating controlled ecological life support system (CELSS). Examples of the use of this model in assessing plant canopy dynamics and CELSS design options are also presented.

  17. Influence of Chloride and Transpiration on Net 15NO 3 ?Uptake Rate by Citrus Roots

    Microsoft Academic Search

    MIGUEL CEREZO; PILAR GARCÍA-AGUSTÍN; EDUARDO PRIMO-MILLO

    1999-01-01

    Three-month-old Carrizo citrange (hybrid of Citrus sinensis L. Osbeck×Poncirus trifoliata Blanco) seedlings were grown in controlled environment chambers in pots of fine sand. Plants were irrigated with either non-saline or saline solutions over a 3-week period. After these treatments, plants were transferred to vessels containing a 5 m m15NO3K (96% atom excess15N) solution, and transpiration as well as concentration of15N

  18. Oxygen isotope enrichment ( 18O) as a measure of time-averaged transpiration rate

    Microsoft Academic Search

    M. S. Sheshshayee; H. Bindumadhava; R. Ramesh; T. G. Prasad; M. R. Lakshminarayana; M. Udayakumar

    2005-01-01

    Experimental evidence is presented to show that the 18 O enrichment in the leaf biomass and the mean (time- averaged) transpiration rate are positively correlated in groundnut and rice genotypes. The relationship between oxygen isotope enrichment and stomatal con- ductance (gs) was determined by altering gs through ABA and subsequently using contrasting genotypes of cowpea and groundnut. The Peclet model

  19. Differences in transpiration rates between tropical and temperate grasses under controlled conditions

    Microsoft Academic Search

    R. W. Downes

    1969-01-01

    Two experiments were conducted to determine the transpiration rates of tropical and temperate grasses under a range of environmental conditions. In dense populations, three temperate grasses lost considerably more water per unit leaf area than did four tropical grasses, though tropical grasses tended to produce more dry matter per unit leaf area. The efficiency of production in relation to water

  20. Effect of transpiration on plant accumulation and translocation of PPCP/EDCs.

    PubMed

    Dodgen, Laurel K; Ueda, Aiko; Wu, Xiaoqin; Parker, David R; Gan, Jay

    2015-03-01

    The reuse of treated wastewater for agricultural irrigation in arid and hot climates where plant transpiration is high may affect plant accumulation of pharmaceutical and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs). In this study, carrot, lettuce, and tomato plants were grown in solution containing 16 PPCP/EDCs in either a cool-humid or a warm-dry environment. Leaf bioconcentration factors (BCF) were positively correlated with transpiration for chemical groups of different ionized states (p < 0.05). However, root BCFs were correlated with transpiration only for neutral PPCP/EDCs (p < 0.05). Neutral and cationic PPCP/EDCs showed similar accumulation, while anionic PPCP/EDCs had significantly higher accumulation in roots and significantly lower accumulation in leaves (p < 0.05). Results show that plant transpiration may play a significant role in the uptake and translocation of PPCP/EDCs, which may have a pronounced effect in arid and hot climates where irrigation with treated wastewater is common. PMID:25594843

  1. The effectiveness of a foliar spray of kaolinite clay in reducing transpiration of cotton plants

    E-print Network

    McMichael, Bobbie Lee

    1967-01-01

    THE EFFECTIVENESS OF A FOLIAR SPRAY OI" KAOLINITE CLAY IN REDUCING TRANSPIRATION OF COTTON PLANTS A Thesis Bobble L. McMichael Submitted to the Graduate Col]ege cf the Texas A&I University ir, Partial fulfillment of the requirements...

  2. CONTROL OF EVAPORATIVE DEMAND ON TRANSPIRING PLANTS I. SENSITIVITIES OF EVAPORATIVE DEMAND TO ENVIRONMENTAL FACTORS

    Microsoft Academic Search

    M. KITANO; H. ECUCHI

    KITANO M. and EGUCHI H. Control of evaporative demand on transpiring plants 1. Sensitivities of evaporative demand to environmental factors. BIOTRONICS 20, 53-64, 1991. Effects of environmental factors on evaporative demand (ED) were analyzed, and control characteristics of ED were simulated. ED was affected by the respective environmental factors of irradiance, air temperature, humidity and wind velocity, and the respective

  3. Use of Geostatistics and Plant Hydraulics to Explain Spatial Patterns of Transpiration Across Environmental Gradients

    NASA Astrophysics Data System (ADS)

    Ewers, B. E.; Adelman, J. D.; Mackay, D. S.; Loranty, M.; Traver, E.; Kruger, E. L.

    2005-12-01

    As direct measurements of tree transpiration via sap flux have become routine, the sample size of sap flux studies has dramatically increased. These large sample sizes now provide sufficient data for geostatistical analyses when measurement points are spatially explicit. In this study we tested whether 1) center-of-stand approaches to sap flux measurements and scaling are sufficient for characterizing stand level transpiration and 2) geostatistical techniques provide the information necessary for quantifying important stand and landscape level gradients. To maximize the inferences from our tests, we compared two contrasting forests: one dominated by lodgepole pine (Pinus contorta) in Wyoming and another dominated by trembling aspen (Populus tremuloides) in Wisconsin. The forest in Wyoming is characterized by low precipitation regimes dominated by snowfall while the forest in Wisconsin is characterized by moderate precipitation throughout the growing season. Analyses of the relationship between sample size and variance indicated an inflection point of 30 point pairs but the variance continued a shallow decline even at 100 point pairs. There was also evidence of species impacts on variance of transpiration that changed with environmental conditions. We used variogram analyses to quantify the spatial range of transpiration and found a variable spatial range across days with mean of approximately 30 m. The variability in spatial range could be partially explained by tree species' responses to soil moisture, vapor pressure deficit, and light based on current plant hydraulic knowledge. Our results confirm the utility of geostatistical techniques for quantifying and explaining transpiration in time and space.

  4. Transpiration rate in relation to root and leaf growth in cuttings of Begonia X hiemalis Fotsch

    Microsoft Academic Search

    B. Ottosson; N. T. Welander

    1997-01-01

    Cuttings of Begonia X hiemalis Fotsch. cv. ‘Schwabenland Red’ were rooted in an aeroponics system at 21 °C and 2.9 mol m?2 day?1 photosynthetic photon flux density (PPFD) for 18 h day?1. Leaf length increase rate was higher in leaves appearing at time of root formation compared with leaves starting to expand before roots were formed. Transpiration rate per unit

  5. Effect of carbon dioxide, osmotic potential of nutrient solution, and light intensity on transpiration and resistance to flow of water in pepper plants.

    PubMed

    Janes, B E

    1970-01-01

    The rate of transpiration, temperature of the leaves, and relative water content of leaves of pepper plants were measured in a small chamber in which the temperature, relative humidity, and carbon dioxide concentration of recirculated air were controlled and measured. The data reported were obtained by noting the response of pepper plants to all combinations of the following treatments: high light, 1.5 x 10(6) ergs per square centimeter per second; low light, 3.0 x 10(4) ergs per square centimeter per second; three levels of CO(2): 50, 268, and 730 parts per million; nutrient solution osmotic potentials of -0.5, -5.0, -7.5, and -9.5 bars.The rate of transpiration of pepper plants was reduced by a decrease in osmotic potential of the nutrient solution, an increase in CO(2) concentration in the ambient air, and a decrease in light intensity. The response, as measured by transpiration, to the three variables, light, CO(2), and osmotic potential indicated that each variable influenced a different and independent mechanism. A change in a single variable produced essentially the same percentage change at all levels of the other variables. The rate of movement of water from roots to leaves was in response to water potential gradient and not the actual potential in the leaves.The resistance to flow of water through the plants (R) was estimated by dividing the difference between the water potentials of the solution and the leaves by the rate of transpiration. The data indicated an increase in R as the rate of transpiration decreased. The type and size of errors encountered in the estimation of R and location of R within the plant are discussed. PMID:16657285

  6. A Laboratory Exercise to Assess Transpiration.

    ERIC Educational Resources Information Center

    Schrock, Gould F.

    1982-01-01

    Procedures are outlined for a laboratory exercise in which students use a gravimetric method to determine the rate of transpiration in sunflower seedlings. Discusses the data in terms of the effectiveness of stomatal openings, mechanisms for water movement in plants, and the role of transpiration in the environment. (DC)

  7. Transpirational Supply and Demand: Plant, Soil, and Atmospheric Effects Evaluated by Simulation

    NASA Astrophysics Data System (ADS)

    Federer, C. Anthony

    1982-04-01

    The assumption that transpiration is the lesser of an atmospheric demand function and a water supply function was tested by simulation with Federer's (1979) soil-plant-atmosphere model. The best estimate of atmospheric demand is called unstressed transpiration, defined as the transpiration that would occur in ambient conditions if stomata were unaffected by plant-water potential. For practical purposes the Penman equation provides a good estimate of unstressed transpiration for short vegetation but not for forests. Even when atmospheric variables and the Penman estimate are held constant among forest canopies, unstressed transpiration can vary by a factor of two because of variation both in the maximum value of leaf conductance and in the ratio of canopy conductance to leaf conductance. The best water supply function incorporates depth variation of soil water potential and of root and soil properties. A more practical supply function uses the ratio of available water in the root zone, W, to maximum available water WM. The maximum available water is soil water held at potentials less than that at which the hydraulic conductivity is 2 mm/d and greater than the critical leaf water potential at which stomata are completely closed. Using a mature hardwood forest as a standard, various parameters were varied to examine their effects on a water supply function defined as a supply constant times W/WM. The supply constant was found to be independent of soil texture and physical properties. Root density and the internal resistance of the plant to water flow were the most important determinants of the supply constant. Reasonable variation of root density and internal resistance produced variation in the constant from 1.9 mm/h, which implies that supply is less than demand only when soil is very dry, to 0.5 mm/hr, which implies that supply cannot meet the demand even when the soil is wet.

  8. Calculations of the transpiration rate and temperature of a leaf

    Microsoft Academic Search

    E. T. Linacre

    1964-01-01

    Sample calculations of the water-loss rate and the temperature of a leaf have been made in terms of three climatic factors (i. e. net radiation intensity, ambient temperature and ambient vapour pressure) and two diffusion resistances, respectively within and outside the leaf tissue. The results indicate the variability of the ratio of the respective water losses from a leaf and

  9. Effect of osmotic stress on transpiration and absorption rates in triticale and its parental species

    Microsoft Academic Search

    A. Morant-Avice; G. Ferard; A. Coudret

    1989-01-01

    In triticale and its parental species, the application of a root osmotic stress induced either a transient increase or an\\u000a immediate decrease in transpiration rate. The response of wheat (Trticum dicoccum farrum) proved to depend on relative humidity of air. In rye (Secale cerealecv. Petkus) and triticale (T. 300) the effect of NaCl stress was less expressive, than the effect

  10. Deuterium excess as a proxy for continental moisture recycling and plant transpiration

    NASA Astrophysics Data System (ADS)

    Aemisegger, F.; Pfahl, S.; Sodemann, H.; Lehner, I.; Seneviratne, S. I.; Wernli, H.

    2014-04-01

    Studying the evaporation process and its link to the atmospheric circulation is central for a better understanding of the feedbacks between the surface water components and the atmosphere. In this study, we use 5 months of deuterium excess (d) measurements at the hourly to daily timescale from a cavity ring-down laser spectrometer to characterise the evaporation source of low-level continental water vapour at the long-term hydrometeorological monitoring site Rietholzbach in northeastern Switzerland. To reconstruct the phase change history of the air masses in which we measure the d signature and to diagnose its area of surface evaporation we apply a Lagrangian moisture source diagnostic. With the help of a correlation analysis we investigate the strength of the relation between d measurements and the moisture source conditions. Temporal episodes with a duration of a few days of strong anticorrelation between d and relative humidity as well as temperature are identified. The role of plant transpiration, the large-scale advection of remotely evaporated moisture, the local boundary layer dynamics at the measurement site and recent precipitation at the site of evaporation are discussed as reasons for the existence of these modes of strong anticorrelation between d and moisture source conditions. We show that the importance of continental moisture recycling and the contribution of plant transpiration to the continental evaporation flux may be deduced from the d-relative humidity relation at the seasonal timescale as well as for individual events. The methodology and uncertainties associated with these estimates of the transpiration fraction of evapotranspiration are presented and the proposed novel framework is applied to individual events from our data set. Over the whole analysis period (August to December 2011) a transpiration fraction of the evapotranspiration flux over the continental part of the moisture source region of 62% is found albeit with a large event-to-event variability (0% to 89%) for continental Europe. During days of strong local moisture recycling a higher overall transpiration fraction of 76% (varying between 65% and 86%) is found. These estimates are affected by uncertainties in the assumptions involved in our method as well as by parameter uncertainties. An average uncertainty of 11% results from the strong dependency of the transpiration estimates on the choice of the non-equilibrium fractionation factor. Other uncertainty sources like the influence of boundary layer dynamics are probably large but more difficult to quantify. Nevertheless, such Lagrangian estimates of the transpiration part of continental evaporation could potentially be useful for the verification of model estimates of this important land-atmosphere coupling parameter.

  11. Determining the transpiration rate of peach trees under two trickle irrigation regimes 

    E-print Network

    Rodrigue, Paul Bryan

    1980-01-01

    conditions. Therefore, additional neutron probe measurements along with volumetric soil samples were obtained on July 24, 1979, when low values of soil moisture content were present. The data from these two dates provided data points over a range of soil... to determine the transpi rat1on rate of peach trees under two trickle 1 rr1gat1on regimes. To determine the transpiration rate a volume of soil around the test trees was 1nstru- mented with neutron access tubes. Soil moisture depletion was measured weekly...

  12. Deuterium excess as a proxy for continental moisture recycling and plant transpiration

    NASA Astrophysics Data System (ADS)

    Aemisegger, F.; Pfahl, S.; Sodemann, H.; Lehner, I.; Seneviratne, S. I.; Wernli, H.

    2013-11-01

    Studying the evaporation process and its link to the atmospheric circulation is central for a better understanding of the feedbacks between the surface water components and the atmosphere. Stable water isotopes are ideal tools to investigate surface evaporation as they are naturally available tracers of water phase changes in the atmosphere. The strength of isotope fractionation processes depends on environmental conditions such as relative humidity and temperature. In this study, we use five months of deuterium excess (d) measurements at the hourly to daily timescale from a cavity ring-down laser spectrometer to characterise the evaporation source of low-level continental water vapour at the long-term hydrometeorological monitoring site Rietholzbach in northeastern Switzerland. To reconstruct the phase change history of the air masses in which we measure the d signature and to diagnose its area of surface evaporation we apply an established Lagrangian moisture source diagnostic. With the help of a correlation analysis we investigate the strength of the relation between d measurements and the moisture source conditions. Temporal episodes with a duration of a few days of strong anticorrelation between d and relative humidity as well as temperature are identified. The role of plant transpiration, the large-scale advection of remotely evaporated moisture, the local boundary layer dynamics at the measurement site and recent precipitation at the site of evaporation are discussed as reasons for the existence of these modes of strong anticorrelation between d and moisture source conditions. The relation between d in atmospheric water vapour at the measurement site and the relative humidity conditions at the location of evaporation exhibits distinct characteristics for land surface evaporation and ocean evaporation. We show that the importance of continental moisture recycling and the contribution of plant transpiration to the continental evaporation flux can be deduced from the d-relative humidity relation at the seasonal timescale as well as for individual events. The slope of the relation between d and the diagnosed moisture source relative humidity provides a novel framework to estimate the transpiration fraction of land evapotranspiration at the local to continental scale. Over the whole analysis period (August to December 2011) a transpiration fraction of the evapotranspiration flux over the continental part of the moisture source region of 63% is found albeit with a large event-to-event variability (0% to 99%) for continental Europe. During days of strong local moisture recycling a higher overall transpiration fraction of 82% (varying between 65% and 94%) is found. Such Lagrangian estimates of the transpiration part of continental evaporation could potentially be useful for the verification of model estimates of this important land-atmosphere coupling parameter.

  13. Xylem transport and shoot accumulation of lumichrome, a newly recognized rhizobial signal, alters root respiration, stomatal conductance, leaf transpiration and photosynthetic rates in legumes and cereals.

    PubMed

    Matiru, V N; Dakora, F D

    2005-03-01

    * Root respiration, stomatal conductance, leaf transpiration and photosynthetic rates were measured in phytotron and field-grown plants following the application of 5 or 10 nM lumichrome, 10 nM ABA (abscisic acid) and 10 ml of 0.2 OD600 infective rhizobial cells. * Providing soybean and cowpea roots with their respective homologous rhizobia and/or purified lumichrome increased the concentration of this molecule in xylem sap and leaf extracts. Relative to control, rhizobial inoculation and lumichrome application significantly increased root respiration in maize, decreased it in lupin, but had no effect on the other test species. * Applying either lumichrome (10 nM), infective rhizobial cells or ABA to roots of plants for 44 h in growth chambers altered leaf stomatal conductance and transpiration in cowpea, lupin, soybean, Bambara groundnut and maize, but not in pea or sorghum. Where stomatal conductance was increased by lumichrome application or rhizobial inoculation, it resulted in increased leaf transpiration relative to control plants. Treating roots of field plants of cowpea with this metabolite up to 63 d after planting showed decreased stomatal conductance, which affected CO2 intake and reduction by Rubisco. * The effect of rhizobial inoculation closely mirrored that of lumichrome application to roots, indicating that rhizobial effects on these physiological activities were most likely due to lumichrome released into the rhizosphere. PMID:15720696

  14. A bio-inspired micropump based on stomatal transpiration in plants.

    PubMed

    Li, Jing-min; Liu, Chong; Xu, Zheng; Zhang, Kai-ping; Ke, Xue; Li, Chun-yu; Wang, Li-ding

    2011-08-21

    Stomatal transpiration, which is an efficient way to carry water from the roots up to the leaves, can be described by "diameter-law". According to the law, the flow rate induced by micropore transpiration far exceeded that induced by macroscale evaporation, and it can be controlled by opening (or closing) some micropores. In this research, a bio-inspired micropump based on stomatal transpiration is presented. The micropump is composed of three layers: the top layer is a 93 ?m-thick PVC (polyvinylchloride) film with a group of slit-like micropores; the second layer is a PMMA sheet with adhesives to join the other two layers together; the third layer is a microporous membrane. Using this pump, controllable flow rates of 0.13-3.74 ?l min(-1) can be obtained. This micropump features high and adjustable flow-rates, simple structure and low fabrication cost. It can be used as a "plug and play" fluid-driven unit without any external power sources and equipment. PMID:21725568

  15. The stable isotope composition of transpired water and the rate of change in leaf water enrichment in response to variable environments

    NASA Astrophysics Data System (ADS)

    Simonin, K. A.; Roddy, A. B.; Link, P.; Apodaca, R. L.; Tu, K. P.; Hu, J.; Dawson, T. E.; Barbour, M.

    2012-12-01

    Previous research has shown that during daylight hours the isotope composition of leaf water is generally well approximated by steady-state leaf water isotope enrichment models. However, there is little direct confirmation of isotopic steady state (ISS) transpiration. Here we use a novel method to evaluate the frequency (or infrequency) of ISS transpiration and the rate of change in leaf water enrichment when leaves are exposed to a variable environment. Specifically, our study had three goals. First, we wanted to develop a new method to measure the isotope fluxes of transpiration that relies on isotope ratio infrared spectroscopy (IRIS) and highlight how an IRIS instrument can be coupled to plant gas exchange systems. In doing so, we also developed a method for controlling the absolute humidity entering the gas exchange cuvettes across a wide range of concentrations (approximately 4000 ppmv to 22000 ppmv) without changing the isotope composition of water vapour entering the cuvette. Second, we quantified variation in the isotope composition of transpired water vapor and the rate of change in leaf water enrichment that can occur as a result of changes in relative humidity, leaf surface conductance to water vapour, leaf temperature and the isotope composition of atmospheric water vapor. Third, we examine the differences between steady state and non-steady state model predictions of leaf water enrichment at the site of evaporation. In our measurements the isotopic compositions of transpired water were neither stable nor equal to source water until leaves had been maintained at physiological steady state for at least 40 minutes. Additionally when transpiration was not at ISS, the steady state model predictions of leaf water enrichment at the site of evaporation exceeded non steady-state model predictions by up to 8 per mil. Further, the rate of change in leaf water enrichment was highly sensitive to variation in leaf water content. Our results suggest that a variable environment is likely to preclude isotopic steady-state transpiration and that this effect would be exacerbated by lengthy leaf water turnover times.

  16. Assimilation and transpiration capabilities of rhyniophytic plants from the Lower Devonian and their implications for paleoatmospheric CO 2 concentration

    Microsoft Academic Search

    Anita Roth-Nebelsick; Wilfried Konrad

    2003-01-01

    The characteristic basic construction of early land plants with an upright posture is represented by a simple leaf- and rootless axis system with a central conducting bundle (‘rhyniophytic habit’). Variations of this simple architectural principle in different early land plant taxa probably reflect different ecophysiological requirements. In this contribution, the assimilation and transpiration of three different Rhynie Chert taxa (Pragian,

  17. Reduction of Transpiration

    Microsoft Academic Search

    W. J. Roberts

    1961-01-01

    The monomolecular film technique for reducing evaporation from water surfaces has been applied to the problem of transpiration from plants. Hybrid corn grown in soil en- riched by various amounts of fatty alcohols such as hexadecanol has required up to 40 per cent less water during its growth than control plants. It is theorized that some of the transpiration from

  18. Validation of canopy transpiration in a mixed-species foothill eucalypt forest using a soil-plant-atmosphere model

    NASA Astrophysics Data System (ADS)

    Gharun, Mana; Turnbull, Tarryn L.; Adams, Mark A.

    2013-06-01

    Studies of the hydrology of native eucalypt forests in south-east Australia have focused on ash-type eucalypt species that are largely confined to Victoria and Tasmania. Mixed species foothill forests comprise the largest proportion of the forest estate in south-east Australia, yet are poorly known hydrologically. The ability to predict forest transpiration, both with reasonable accuracy and in response to changes in the environment, is essential for catchment management. A soil-plant-atmosphere model (SPA) was validated for 222 days in a mature, mixed species forest of north-east Victoria using measurements of overstorey transpiration (Eucalyptus radiata and Eucalyptus goniocalyx) and site-specific climate and vegetation parameters. There was a stronger relationship between average daily transpiration (0.71 mm day-1) and daily minimum relative humidity (R2 = 0.71), than between average daily transpiration and daily maximum temperature (R2 = 0.65). Stand water use could be predicted best from vapour pressure deficit (R2 = 0.89). SPA successfully predicted stand transpiration (R2 = 0.85) over a range of soil water and climatic conditions. A sensitivity analysis suggests that among the various required inputs, leaf area index (LAI) was the most important, and accurate estimates of LAI could significantly improve estimation of stand transpiration.

  19. Transpiration Rate. An Important Factor Controlling the Sucrose Content of the Guard Cell Apoplast of Broad Bean

    Microsoft Academic Search

    William H. Outlaw

    2001-01-01

    Evaporation of water from the guard cell wall concentrates apoplastic solutes. We hypothesize that this phenomenon provides two mechanisms for responding to high transpiration rates. First, apoplastic abscisic acid is concentrated in the guard cell wall. Second, by accumulating in the guard cell wall, apoplastic sucrose (Suc) provides a direct osmotic feedback to guard cells. As a means of testing

  20. Cadmium exposure in Brassica juncea causes a decline in transpiration rate and leaf expansion without effect on photosynthesis

    Microsoft Academic Search

    Angela Haag-Kerwer; Holger J. Schafer; Senta Heiss; Cornelia Walter; Thomas Rausch

    1999-01-01

    decline in transpiration rate. Brassica juncea L. is able to accumulate more than Key words: Brassica juncea, gas exchange, chlorophyll 400 m gg '1 DW Cd in the shoot, a physiological trait fluorescence, growth, phytochelatin, c-ECS, MT2, which may be exploited for the bioremediation of cadmium.

  1. Transpiration modulates phosphorus acquisition in tropical tree seedlings.

    PubMed

    Cernusak, Lucas A; Winter, Klaus; Turner, Benjamin L

    2011-08-01

    Several experiments were conducted with tropical tree and liana seedlings in which transpiration ratio and leaf phosphorus to carbon ratio (P:C) were measured. Transpiration ratio was expressed as kg H(2)O transpired g(-1) C incorporated into plant biomass, and leaf P:C as mg P g(-1) C. Leaf P:C was positively correlated with transpiration ratio across 19 species for plants grown under similar conditions (R(2)?=?0.35, P?transpiration ratio. Within four of these five species, leaf P:C correlated positively with transpiration ratio. The slope and strength of the correlation varied among species. In one experiment, whole-plant P:C was measured in addition to leaf P:C. Patterns of correlation between whole-plant P:C and transpiration ratio were similar to those between leaf P:C and transpiration ratio. Together, these observations suggest that transpiration can influence the rate of P uptake from soil in tropical tree and liana seedlings. We suggest that this occurs through transport of inorganic phosphate and organic P compounds to root surfaces by transpiration-induced mass flow of the soil solution. The positive correlation between leaf P:C and transpiration ratio suggests that leaf P:C could decline in tropical forests as atmospheric CO(2) concentration rises, due to decreasing transpiration ratios. PMID:21856654

  2. Transpiration cooling of hypersonic blunt bodies with finite rate surface reactions

    NASA Technical Reports Server (NTRS)

    Henline, William D.

    1989-01-01

    The convective heat flux blockage to blunt body and hypersonic vehicles by transpiration cooling are presented. The general problem of mass addition to laminar boundary layers is reviewed. Results of similarity analysis of the boundary layer problem are provided for surface heat flux with transpiration cooling. Detailed non-similar results are presented from the numerical program, BLIMPK. Comparisons are made with the similarity theory. The effects of surface catalysis are investigated.

  3. Plant delta 15N correlates with the transpiration efficiency of nitrogen acquisition in tropical trees.

    PubMed

    Cernusak, Lucas A; Winter, Klaus; Turner, Benjamin L

    2009-11-01

    Based upon considerations of a theoretical model of (15)N/(14)N fractionation during steady-state nitrate uptake from soil, we hypothesized that, for plants grown in a common soil environment, whole-plant delta(15)N (deltaP) should vary as a function of the transpiration efficiency of nitrogen acquisition (F(N)/v) and the difference between deltaP and root delta(15)N (deltaP - deltaR). We tested these hypotheses with measurements of several tropical tree and liana species. Consistent with theoretical expectations, both F(N)/v and deltaP - deltaR were significant sources of variation in deltaP, and the relationship between deltaP and F(N)/v differed between non-N(2)-fixing and N(2)-fixing species. We interpret the correlation between deltaP and F(N)/v as resulting from variation in mineral nitrogen efflux-to-influx ratios across plasma membranes of root cells. These results provide a simple explanation of variation in delta(15)N of terrestrial plants and have implications for understanding nitrogen cycling in ecosystems. PMID:19726571

  4. Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables.

    PubMed

    Simonin, Kevin A; Roddy, Adam B; Link, Percy; Apodaca, Randy; Tu, Kevin P; Hu, Jia; Dawson, Todd E; Barbour, Margaret M

    2013-12-01

    During daylight hours, the isotope composition of leaf water generally approximates steady-state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady-state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of (18)O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non-steady state. We show that non-steady-state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents. PMID:23647101

  5. TRANSPIRATION EFFECT ON THE UPTAKE AND DISTRIBUTION OF BROMACIL, NITROBENZENE, AND PHENOL IN SOYBEAN PLANTS (JOURNAL VERSION)

    EPA Science Inventory

    The influence of transpiration rate on the uptake and translocation of two industrial waste compounds, phenol and nitrobenzene, and one pesticide, 5-bromo-3-sec-butyl-6-methyluracil (bromacil), was examined. Carbon-14 moieties of each compound were provided separately in hydropon...

  6. Combining quantitative trait loci analysis with physiological models to predict genotype-specific transpiration rates.

    PubMed

    Reuning, Gretchen A; Bauerle, William L; Mullen, Jack L; McKay, John K

    2015-04-01

    Transpiration is controlled by evaporative demand and stomatal conductance (gs ), and there can be substantial genetic variation in gs . A key parameter in empirical models of transpiration is minimum stomatal conductance (g0 ), a trait that can be measured and has a large effect on gs and transpiration. In Arabidopsis thaliana, g0 exhibits both environmental and genetic variation, and quantitative trait loci (QTL) have been mapped. We used this information to create a genetically parameterized empirical model to predict transpiration of genotypes. For the parental lines, this worked well. However, in a recombinant inbred population, the predictions proved less accurate. When based only upon their genotype at a single g0 QTL, genotypes were less distinct than our model predicted. Follow-up experiments indicated that both genotype by environment interaction and a polygenic inheritance complicate the application of genetic effects into physiological models. The use of ecophysiological or 'crop' models for predicting transpiration of novel genetic lines will benefit from incorporating further knowledge of the genetic control and degree of independence of core traits/parameters underlying gs variation. PMID:25124388

  7. On the enrichment of H 2 18 O in the leaves of transpiring plants

    Microsoft Academic Search

    G. Dongmann; H. W. Nuernberg; H. Foerstel; K. Wagener

    1974-01-01

    Summary The vapor pressure difference between H218O and H216O is the reason for the accumulation of the heavy molecule in transpiring leaves. Since photosynthesis on land is the main source of atmospheric oxygen, this mechanism is important for the remarkable enrichment of18O in atmospheric O2 (Dole effect). Using a simple box model for transpiring leaves a quantitative understanding of the

  8. Effect of temperature and humidity on the transpiration rate of the whole mushrooms

    Microsoft Academic Search

    P. V. Mahajan; F. A. R. Oliveira; I. Macedo

    2008-01-01

    Water loss or transpiration is an important physiological process that affects the main quality characteristics of fresh mushrooms, such as saleable weight, appearance and texture. A loss in weight of only 5% may cause fresh produce to lose freshness and appear wilted and it is an important parameter to be considered while designing packaging. A setup was developed to monitor

  9. Transpiration cooling in hypersonic flight

    NASA Technical Reports Server (NTRS)

    Tavella, Domingo; Roberts, Leonard

    1989-01-01

    A preliminary numerical study of transpiration cooling applied to a hypersonic configuration is presented. Air transpiration is applied to the NASA all-body configuration flying at an altitude of 30500 m with a Mach number of 10.3. It was found that the amount of heat disposal by convection is determined primarily by the local geometry of the aircraft for moderate rates of transpiration. This property implies that different areas of the aircraft where transpiration occurs interact weakly with each other. A methodology for quick assessments of the transpiration requirements for a given flight configuration is presented.

  10. A phytotoxicity test using transpiration of willows.

    PubMed

    Trapp, S; Zambrano, K C; Kusk, K O; Karlson, U

    2000-08-01

    A short-term acute toxicity assay for willow trees growing in contaminated solution or in polluted soil was developed and tested. The test apparatus consists of an Erlenmeyer flask with a prerooted tree cutting growing in it. Growth and reduction of transpiration are used to determine toxicity. Transpiration is closely related to photosynthesis and growth, but is easier and faster to measure and can be measured without disturbance of the test system. Plants are grown for 24 h in uncontaminated nutrient solution before the toxicant is added to determine the initial transpiration. The loss of weight is expressed as % decrease after 48 and 72 h or longer compared to the initial transpiration, divided by the transpiration of control plants. More toxicity parameters are growth and water use efficiency of the plants. The sensitivity of the test was evaluated with 3,5-dichlorophenol. EC(50) values between 5.8 and 9.6 mg/L were found. This is similar to the results from algal growth rate tests. The willow tree toxicity test may be useful for determining the site-specific toxicity of polluted soils and for terrestrial risk assessment of new chemicals and pesticides. PMID:10871417

  11. Simulating canopy transpiration and photosynthesis of corn plants under contrasting water regimes using a coupled model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A process-based corn simulation model (MaizeSim) was coupled with a two-dimensional soil simulator (2DSOIL) to simulate the transpiration and photosynthesis of corn under drought stress. To simulate stomatal reaction to drought stress, two stomatal controlling algorithms (control by hydraulic signal...

  12. COMBINED EFFECT OF WHITENING AND VENTILATION METHODS ON MICROCLIMATE AND TRANSPIRATION IN ROSE GREENHOUSE

    E-print Network

    Lieth, J. Heinrich

    COMBINED EFFECT OF WHITENING AND VENTILATION METHODS ON MICROCLIMATE AND TRANSPIRATION IN ROSE of inside air temperature, plant canopy temperature, growing media temperature, relative humidity and transpiration rate in a single span rose greenhouse size 22m x 10m x 4.90m located at the department

  13. Prolonged experimental drought reduces plant hydraulic conductance and transpiration and increases mortality in a piñon-juniper woodland.

    PubMed

    Pangle, Robert E; Limousin, Jean-Marc; Plaut, Jennifer A; Yepez, Enrico A; Hudson, Patrick J; Boutz, Amanda L; Gehres, Nathan; Pockman, William T; McDowell, Nate G

    2015-04-01

    Plant hydraulic conductance (k s) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between k s and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (E C) and conductance (G C). For both species, we observed significant reductions in plant transpiration (E) and k s under experimentally imposed drought. Conversely, supplemental water additions increased E and k s in both species. Interestingly, both species exhibited similar declines in k s under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant k s also reduced carbon assimilation in both species, as leaf-level stomatal conductance (g s) and net photosynthesis (A n) declined strongly with decreasing k s. Finally, we observed that chronically low whole-plant k s was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy E C and G C. Our data indicate that significant reductions in k s precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon-juniper woodlands can be expected due to reduced plant hydraulic conductance and increased mortality of both piñon pine and juniper under anticipated future conditions of more frequent and persistent regional drought in the southwestern United States. PMID:25937906

  14. Photosynthesis and Transpiration

    NSDL National Science Digital Library

    2013-07-08

    In this activity on page 7 of the PDF, learners examine the effects that light and air have on green plants. Learners plant seeds in two containers and compare what happens when the containers are placed in dark and light places. Use this activity to introduce learners to photosynthesis and transpiration.

  15. Unveiling stomata 24/7: can we use carbonyl sulfide (COS) and oxygen isotopes (18O) to constrain estimates of nocturnal transpiration across different evolutionary plant forms?

    NASA Astrophysics Data System (ADS)

    Gimeno, Teresa E.; Ogee, Jerome; Bosc, Alexander; Genty, Bernard; Wohl, Steven; Wingate, Lisa

    2015-04-01

    Numerous studies have reported a continued flux of water through plants at night, suggesting that stomata are not fully closed. Growing evidence indicates that this nocturnal flux of transpiration might constitute an important fraction of total ecosystem water use in certain environments. However, because evaporative demand is usually low at night, nocturnal transpiration fluxes are generally an order of magnitude lower than rates measured during the day and perilously close to the measurement error of traditional gas-exchange porometers. Thus estimating rates of stomatal conductance in the dark (gnight) precisely poses a significant methodological challenge. As a result, we lack accurate field estimates of gnight and how it responds to different atmospheric drivers, indicating the need for a different measurement approach. In this presentation we propose a novel method to obtain detectable and robust estimates of gnight. We will demonstrate using mechanistic theory how independent tracers including the oxygen isotope composition of CO2 (?18O) and carbonyl sulfide (COS) can be combined to obtain robust estimates of gnight. This is because COS and CO18O exchange within leaves are controlled by the light insensitive enzyme carbonic anhydrase. Thus, if plant stomata are open in the dark we will continue to observe COS and CO18O exchange. Using our theoretical model we will demonstrate that the exchange of these tracers can now be measured using advances in laser spectrometry techniques at a precision high enough to determine robust estimates of gnight. We will also present our novel experimental approach designed to measure simultaneously the exchange of CO18O and COS alongside the conventional technique that relies on measuring the total water flux from leaves in the dark. Using our theoretical approach we will additionally explore the feasibility of our proposed experimental design to detect variations in gnight during drought stress and across a variety of plant types that have evolved diverse strategies to control water loss from leaf tissues.

  16. Measuring forest evaporation and transpiration rates with fibre optic temperature sensing

    NASA Astrophysics Data System (ADS)

    Coenders-Gerrits, Miriam; Luxemburg, Wim; Hessels, Tim; de Kloe, Arjan; Elbers, Jan

    2014-05-01

    Evaporation is one of the most important fluxes of the water balance as it accounts for 55-80% of the precipitation. However, measuring evaporation remains difficult and requires sophisticated and expensive equipment. In this paper we propose a new measuring technique based on the existing Bowen ratio method. With a fibre optic cable a temperature and a vapour pressure profile can be measured by the principle of a psychrometer and combined with the net radiation (and ground heat flux) the latent heat can be calculated. Compared to the conventional Bowen ratio method the advantages of this method is that the profiles are measured with a single sensor (resulting in a smaller error), and contain more measuring points in the vertical and therefore give more insight into the developed profiles. The method also allows to measure through a forest canopy. Applying the Bowen ratio above and below the canopy an estimation of the transpiration flux can be obtained. As a first test, we compared in a pine forest in The Netherlands (Loobos) the transpiration estimates of the fibre optic cable with sapflow measurements, and eddy covariance measurements above and below the canopy. The experiment was carried out on three days in September 2013 and the preliminary results show reasonable correlation with the eddy covariance estimates, but not with the sapflow observations. To explain the differences further investigation is needed and a longer measuring period is required.

  17. Modelling canopy resistances and transpiration of grassland

    NASA Astrophysics Data System (ADS)

    Menzel, L.

    1996-05-01

    Lysimeter measurements have been used in an inverted form of the Penman-Monteith equation to calculate daily values of canopy resistances for dense and dry plant cover. The analysis of the relationship between the calculated data and a series of environmental variables showed that canopy resistances of the investigated grassland can be expressed as non-linear functions of the air temperature, leaf area index and soil moisture deficit. After linearization of these empirical functions the selected variables have been combined in a multiple regression model which was adopted as a submodel for the Penman-Monteith equation. Daily and hourly modelled canopy resistances have been used to calculate transpiration for periods with various environmental conditions. The results show that the difference between calculated and measured daily transpiration is in the range of 5 %. Hourly predicted transpiration rates are able to explain approximately 78 % of the variance of measured data.

  18. A maximum hypothesis of transpiration

    Microsoft Academic Search

    Jingfeng Wang; Rafael L. Bras; Manuel Lerdau; Guido D. Salvucci

    2007-01-01

    We hypothesize that the system of liquid water in leaf tissues and the water vapor in the atmosphere tends to evolve towards a potential equilibrium as quickly as possible by maximization of the transpiration rate. We make two assumptions in formulating the transpiration rate: (1) stomatal aperture is directly controlled by guard cell turgor (or leaf water potential); (2) CO2

  19. The effect of atmospheric humidity on photosynthesis, transpiration and water use efficiency of leaves of several plant species.

    PubMed

    Rawson, H M; Begg, J E; Woodward, R G

    1977-01-01

    The effect of humidity on the gas exchange of leaves of the dicotyledons soybean (Glycine max (L.) Merrill), sunflower (Helianthus annuus L.), jojoba (Simmondsia chinensis (L.) Schneider), and saltbush (Atriplex halimus L.) and the monocotyledons wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) sorghum (Sorghum bicolor (L.) Moench) and barnyard grass (Echinochloa crus-galli (L.) Beauv.) was examined under conditions of adequate soil moisture in a controlled environment. Photosynthesis and stomatal and internal diffusion resistances of whole, attached, single leaves were not affected by changes in humidity as the vapour pressure deficit between the leaf and atmosphere ranged from 8 to 27 mb. Transpiration increased linearly with increasing vapour pressure deficit. Whole plants of barley exhibited a different response. As humidity was increased, photosynthesis increased, transpiration expressed per unit of vapour pressure difference increased, and diffusion resistances became smaller. Reasons for the different behaviour of single leaves and whole plants are suggested. An index for water use efficiency, expressed per millibar of vapour pressure deficit, was calculated for single leaves of each species used in the experiments. This showed that water use efficiency was highest in the C4 xerophytes and lowest in the C3 mesophytes. The effect of environment on water use efficiency is examined using data from the literature. PMID:24419571

  20. Sap flow measurements to determine the transpiration of facade greenings

    NASA Astrophysics Data System (ADS)

    Hölscher, Marie-Therese; Nehls, Thomas; Wessolek, Gerd

    2014-05-01

    Facade greening is expected to make a major contribution to the mitigation of the urban heat-island effect through transpiration cooling, thermal insulation and shading of vertical built structures. However, no studies are available on water demand and the transpiration of urban vertical green. Such knowledge is needed as the plants must be sufficiently watered, otherwise the posited positive effects of vertical green can turn into disadvantages when compared to a white wall. Within the framework of the German Research Group DFG FOR 1736 "Urban Climate and Heat Stress" this study aims to test the practicability of the sap flow technique for transpiration measurements of climbing plants and to obtain potential transpiration rates for the most commonly used species. Using sap flow measurements we determined the transpiration of Fallopia baldschuanica, Parthenocissus tricuspidata and Hedera helix in pot experiments (about 1 m high) during the hot summer period from August 17th to August 30th 2012 under indoor conditions. Sap flow measurements corresponded well to simultaneous weight measurement on a daily base (factor 1.19). Fallopia baldschuanica has the highest daily transpiration rate based on leaf area (1.6 mm d-1) and per base area (5.0 mm d-1). Parthenocissus tricuspidata and Hedera helix show transpiration rates of 3.5 and 0.4 mm d-1 (per base area). Through water shortage, transpiration strongly decreased and leaf temperature measured by infrared thermography increased by 1 K compared to a well watered plant. We transferred the technique to outdoor conditions and will present first results for facade greenings in the inner-city of Berlin for the hottest period in summer 2013.

  1. Genetic variation in a grapevine progeny (Vitis vinifera L. cvs Grenache×Syrah) reveals inconsistencies between maintenance of daytime leaf water potential and response of transpiration rate under drought.

    PubMed

    Coupel-Ledru, Aude; Lebon, Éric; Christophe, Angélique; Doligez, Agnès; Cabrera-Bosquet, Llorenç; Péchier, Philippe; Hamard, Philippe; This, Patrice; Simonneau, Thierry

    2014-11-01

    In the face of water stress, plants evolved with different abilities to limit the decrease in leaf water potential, notably in the daytime (?M). So-called isohydric species efficiently maintain high ?M, whereas anisohydric species cannot prevent ?M from dropping as soil water deficit develops. The genetic and physiological origins of these differences in (an)isohydric behaviours remain to be clarified. This is of particular interest within species such as Vitis vinifera L. where continuous variation in the level of isohydry has been observed among cultivars. With this objective, a 2 year experiment was conducted on the pseudo-F1 progeny from a cross between the two widespread cultivars Syrah and Grenache using a phenotyping platform coupled to a controlled-environment chamber. Potted plants of all the progeny were analysed for ?M, transpiration rate, and soil-to-leaf hydraulic conductance, under both well-watered and water deficit conditions. A high genetic variability was found for all the above traits. Four quantitative trait loci (QTLs) were detected for ?M under water deficit conditions, and 28 other QTLs were detected for the different traits in either condition. Genetic variation in ?M maintenance under water deficit weakly correlated with drought-induced reduction in transpiration rate in the progeny, and QTLs for both traits did not completely co-localize. This indicates that genetic variation in the control of ?M under water deficit was not due simply to variation in transpiration sensitivity to soil drying. Possible origins of the diversity in (an)isohydric behaviours in grapevine are discussed on the basis of concurrent variations in soil-to-leaf hydraulic conductance and stomatal control of transpiration. PMID:25381432

  2. Determining the Transpiration Rate of Peach Trees Under Two Trickle Irrigation Regimes

    E-print Network

    Howell, T. A.; McFarland, M. J.; Reddell, D. L.; Brown, K. W.; Newton, R. J.; Rodriguez, P. B.; Van Bavel, C. H. M.; Reeder, E. L.

    The scientific design and management of a modern irrigation system requires that the designer or manager have knowledge of site and plant criteria such as infiltration, drainage, soil fertility, plant water needs, and plant production under varying...

  3. Climate change at northern latitudes: rising atmospheric humidity decreases transpiration, N-uptake and growth rate of hybrid aspen.

    PubMed

    Tullus, Arvo; Kupper, Priit; Sellin, Arne; Parts, Leopold; Sõber, Jaak; Tullus, Tea; Lõhmus, Krista; Sõber, Anu; Tullus, Hardi

    2012-01-01

    At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated atmospheric humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008-2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the humidity treatment effect--inhibition of above-ground growth rate--was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO(3) (-) in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO(2) concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place. PMID:22880067

  4. Estimation of plant transpiration from meteorological data under conditions of sufficient soil moisture

    NASA Astrophysics Data System (ADS)

    Pražák, J.; Šír, M.; Tesar?, M.

    1994-11-01

    The transpiration of forest growth during the growing season when sufficient soil moisture is available is estimated on the basis of the requirement of water for cooling trees. Tree growth is regarded as a cooler with water as a coolant (evaporative latent heat). Trees are simultaneously warmed up by incident solar radiation and cooled down by the ambient air and by the evaporation of water from the leaf. These parallel, mutually competing processes are described in their simplest form and provide the algorithm for the calculation of the cooling-water requirement. The calculation uses hourly values of air temperature and of global-radiation totals. Properties of the forest growth are expressed in terms of two phenomenological constants — effective absorptivity and effective thickness of leaves. Both are obtained by calibration. The applicability of the proposed calculation was subjected to experimental verification during the course of the growing seasons for 1985-1989 in the mountain watershed LIZ, situated in the National Park S?umava in the southern part of the Czech Republic. The error in determining evapotranspiration/transpiration is about 5% of the precipitation over the growing season.

  5. Quantifying the feedback of evaporation and transpiration rates to soil moisture dynamics and meteorological condition changes by a numerical model

    NASA Astrophysics Data System (ADS)

    Su, Ye; Shao, Wei; Vl?ek, Lukáš; Langhammer, Jakub

    2015-04-01

    Evapotranspiration drives the hydrological process through energy-driven water-phase changes between systems of soil-vegetation-atmosphere. Evapotranspiration performs a rather complex process attributable to the spatial and temporal variation of soil-vegetation-atmosphere system. For vegetation-covered land surfaces, the transpiration process is governed by the stomatal behavior and water uptake from the root zone, and evaporation is related with the interception of rainfall and radiation on the canopy and soil surface. This study is emphasized on describing the hydrological process and energy cycle in a basic hydrological response unit, a hillslope. The experimental hillslope is located in an experimental catchment of the Bohemian Forest Mountains' headwaters in the Czech Republic, where is mostly covered by dead Norway spruce forest (Picea abies) stands caused by balk beetle outbreak. High-frequency monitoring network of the hydro-climatic data, soil pore water pressure and soil temperature has been launched since 2012. To conceptualize the land-surface energy and water fluxes in a complex hillslope, a soil-vegetation-atmosphere transport (SVAT) model, coupled with a multi-phase soil physics process (i.e. the water, vapor and heat flow transport) is used. We selected an 8-week basis dataset from 2013 as a pilot for partitioning the evapotranspiration into three interactive components: transpiration (Et), canopy interception evaporation (Ei), and soil evaporation (Es), by using this numerical model. Within such model framework, the sensitive feedback of evapotranspiration rates to rainfall intensity, soil moisture, and solar radiation will be examined by conducting numerical experiments to better understand the mechanism of evapotranspiration process under various influencing factors. Such application study and followed numerical simulations provide a new path for quantifying the behaviors of the soil-vegetation-atmosphere system.

  6. The effects of CO2 on growth and transpiration of radish (Raphanus sativus) in hypobaria

    NASA Astrophysics Data System (ADS)

    Gohil, H. L.; Bucklin, R. A.; Correll, M. J.

    2010-04-01

    Plants grown on long-term space missions will likely be grown in low pressure environments (i.e., hypobaria). However, in hypobaria the transpiration rates of plants can increase and may result in wilting if the water is not readily replaced. It is possible to reduce transpiration by increasing the partial pressure of CO2 (pCO2), but the effects of pCO2 at high levels (>120 Pa) on the growth and transpiration of plants in hypobaria are not known. Therefore, the effects of pCO2 on the growth and transpiration of radish (Raphanus sativus var. Cherry Bomb II) in hypobaria were studied. The fresh weight (FW), leaf area, dry weight (DW), CO2 assimilation rates (CA), dark respiration rates (DR), and transpiration rates from 26 day-old radish plants that were grown for an additional seven days at different total pressures (33, 66 or 101 kPa) and pCO2 (40 Pa, 100 Pa and 180 Pa) were measured. In general, the dry weight of plants increased with CO2 enrichment and with lower total pressure. In limiting pCO2 (40 Pa) conditions, the transpiration for plants grown at 33 kPa was approximately twice that of controls (101 kPa total pressure with 40 Pa pCO2). Increasing the pCO2 from 40 Pa to 180 Pa reduced the transpiration rates for plants grown in hypobaria and in standard atmospheric pressures. However, for plants grown in hypobaria and high pCO2 (180 Pa) leaf damage was evident. Radish growth can be enhanced and transpiration reduced in hypobaria by enriching the gas phase with CO2 although at high levels leaf damage may occur.

  7. The control of transpiration by absorbed radiation

    Microsoft Academic Search

    Roland Pieruschka; Joseph A. Berry

    2010-01-01

    Transpiration plays a key role in the hydrological cycle and models of transpiration have been used in many applications. However, our understanding of mechanisms which control the rate of transpiration is still limited being a domain of two different disciplines. Meteorologists apply the top-down approach driven by physical descriptions and water vapour transport, stomatal conductance is regarded as a boundary

  8. The effects of CO 2 on growth and transpiration of radish ( Raphanus sativus) in hypobaria

    Microsoft Academic Search

    H. L. Gohil; R. A. Bucklin; M. J. Correll

    2010-01-01

    Plants grown on long-term space missions will likely be grown in low pressure environments (i.e., hypobaria). However, in hypobaria the transpiration rates of plants can increase and may result in wilting if the water is not readily replaced. It is possible to reduce transpiration by increasing the partial pressure of CO2 (pCO2), but the effects of pCO2 at high levels

  9. The effects of CO2 on growth and transpiration of radish (Raphanus sativus) in hypobaria

    Microsoft Academic Search

    H. L. Gohil; R. A. Bucklin; M. J. Correll

    2010-01-01

    Plants grown on long-term space missions will likely be grown in low pressure environments (i.e., hypobaria). However, in hypobaria the transpiration rates of plants can increase and may result in wilting if the water is not readily replaced. It is possible to reduce transpiration by increasing the partial pressure of CO2 (pCO2), but the effects of pCO2 at high levels

  10. Solute Export Through Transpiration: A Possible Control of Soil Water Chemistry?

    NASA Astrophysics Data System (ADS)

    Alexander, S. C.; Boyle, D. B.; Alexander, E. C.

    2005-12-01

    Recent studies of soil and ground water interactions in western Minnesota have produced seemingly anomalous results. The soil waters beneath highly transpirative plants (Typha sp., Salix sp. and Populus sp.) in a ground water discharge area developed high calcium sulfate concentrations with only minor enrichment of sodium and chloride. It was expected that concentration of solutes by evapo-transpiration would enrich all ions in the originating ground water more equally. Transpired water is generally assumed to be essentially distilled water although there is little analytical data to support this hypothesis. Given the very high evapotranspiration rates of Western Minnesota, greater than 95% of total water movement, even relatively dilute ion concentrations in the transpired water may be significant in the total chemical budget. To investigate the chemistry of transpired water we adapted techniques that have been used to study total transpiration rates as well as isotopic composition of transpired waters. Our initial results from typha sp. have produced waters that while relatively dilute are distinctly not distilled water. Control samples using de-ionized water over dead vegetation produced minor ion enrichment. All results are in ppm. Ion - Ca, Mg, Na, K, P, Mn, Cl , SO4, NO3-N soil water - 18.5, 2.9, 4.8, 3.8, 0.2, 0.2, 5.6, 2.4, 0.5 transpiration - 1.9, 0.6, 1.5, 8.5, 0.3, 0.4, 9.0, 1.6, <0.1 DI control - 0.1, <0.1, 0.1, <0.1, <0.1, <0.1, <0.1, 1.6, <0.1 The observed transpiration chemistries are in rough agreement with reported literature values for plant stem water. While many plants are known to excrete large molecules the expulsion of ions in transpired water would represent a novel chemical plant pathway.

  11. Development of a simplified plant stomatal resistance model and its validation for potentially transpiring and water-stressed water hyacinths

    NASA Astrophysics Data System (ADS)

    Idso, Sherwood B.

    A simple model of upper-canopy plant stomatal resistance ( ruC) was developed which requires but four input parameters: canopy aerodynamic resistance, upper-canopy foliage temperature, and air vapor pressure deficit and temperature. The model was tested against upper-canopy sunlit leaf stomatal resistance ( r l) measurements of both potentially and non-potentially transpiring water hyacinth plants over the upper-canopy-intercepted net radiation range of 300-450 W m -2 and over a 10-fold range of r l. In all instances, and indicative of the model's good performance, the ratio of r uC/r l consistently averaged about 1.25, due to partial self-shading of the upper-canopy foliage. The significance of this finding to air pollution studies arises from the facts that (1) contemporary knowledge of a plant canopy's leaf area index would allow the transformation of ruC to rC, the total canopy diffusive resistance, and (2) the proper accounting for different trace gas diffusivities would allow the transformation of rc for water vapor to the variety of rC values required to infer the gaseous deposition of important pollutant gas species at vegetated surfaces.

  12. Pattern of Transpiration of Four Shrub Species and Water Consumption from Shrub Stands in an Eco-Reclamation Catchment in Northwest China

    Microsoft Academic Search

    Chuan Tong; Jian-Zhou Gong; Robb Marrs; Lu Zhang; Wei-Qi Wang

    2008-01-01

    The seasonal and diurnal variation in transpiration rate and stomatal conductance of four dominant shrub species (Caragana intermedia, Hippophae rhamnoides, Hedysarum leave, Salix psammophyla) planted in schemes designed to restore vegetation and conserve water in the arid soils of northwest China were studied. Transpiration rates were measured at the leaf scale using a porometer and then combined with data on

  13. Estimating High Rates of Transpiration in Woody Vines with the Heat-Balance Method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heat-balance sap flow gauges were configured to produce a more thermally uniform stem cross section under high flow rates. On mature grapevines (Vitis labruscana) either undisturbed in the field or transplanted to large containers (ca. 1m3 volume), with stem diameters up to 46 mm and leaf area per v...

  14. Estimating High Rates of Transpiration in Woody Vines with the Heat-Balance Method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heat-balance sap flow gauges were configured to produce a more thermally uniform stem cross-section under high flow rates. On mature grapevines (Vitis labruscana) either undisturbed in the field or transplanted to large containers (ca. 1m^3 volume), with stem diameters up to 46 mm and leaf area per ...

  15. Transpiration of urban forests in the Los Angeles metropolitan area.

    PubMed

    Pataki, Diane E; McCarthy, Heather R; Litvak, Elizaveta; Pincetl, Stephanie

    2011-04-01

    Despite its importance for urban planning, landscape management, and water management, there are very few in situ estimates of urban-forest transpiration. Because urban forests contain an unusual and diverse mix of species from many regions worldwide, we hypothesized that species composition would be a more important driver of spatial variability in urban-forest transpiration than meteorological variables in the Los Angeles (California, USA) region. We used constant-heat sap-flow sensors to monitor urban tree water use for 15 species at six locations throughout the Los Angeles metropolitan area. For many of these species no previous data on sap flux, water use, or water relations were available in the literature. To scale sap-flux measurements to whole trees we conducted a literature survey of radial trends in sap flux across multiple species and found consistent relationships for angiosperms vs. gymnosperms. We applied this relationship to our measurements and estimated whole-tree and plot-level transpiration at our sites. The results supported very large species differences in transpiration, with estimates ranging from 3.2 +/- 2.3 kg x tree(-1) x d(-1) in unirrigated Pinus canariensis (Canary Island pine) to 176.9 +/- 75.2 kg x tree(-1) x d(-1) in Platanus hybrida (London planetree) in the month of August. Other species with high daily transpiration rates included Ficus microcarpa (laurel fig), Gleditsia triacanthos (honeylocust), and Platanus racemosa (California sycamore). Despite irrigation and relatively large tree size, Brachychiton populneas (kurrajong), B. discolor (lacebark), Sequoia sempervirens (redwood), and Eucalyptus grandis (grand Eucalyptus) showed relatively low rates of transpiration, with values < 45 kg x tree(-1) x d(-1). When scaled to the plot level, transpiration rates were as high as 2 mm/d for sites that contained both species with high transpiration rates and high densities of planted trees. Because plot-level transpiration is highly dependent on tree density, we modeled transpiration as a function of both species and density to evaluate a likely range of values in irrigated urban forests. The results show that urban forests in irrigated, semi-arid regions can constitute a significant use of water, but water use can be mitigated by appropriate selection of site, management method, and species. PMID:21639035

  16. Restriction of transpiration rate under high vapour pressure deficit and non-limiting water conditions is important for terminal drought tolerance in cowpea.

    PubMed

    Belko, N; Zaman-Allah, M; Diop, N N; Cisse, N; Zombre, G; Ehlers, J D; Vadez, V

    2013-03-01

    Drought stress is a major constraint on cowpea productivity, since the crop is grown under warm conditions on sandy soils having low water-holding capacity. For enhanced performance of crops facing terminal drought stress, like cowpea, water-saving strategies are crucial. In this work, the growth and transpiration rate (TR) of 40 cowpea genotypes with contrasting response to terminal drought were measured under well-watered conditions across different vapour pressure deficits (VPD) to investigate whether tolerant and sensitive genotypes differ in their control of leaf water loss. A method is presented to indirectly assess TR through canopy temperature (CT) and the index of canopy conductance (Ig). Overall, plants developed larger leaf area under low than under high VPD, and there was a consistent trend of lower plant biomass in tolerant genotypes. Substantial differences were recorded among genotypes in TR response to VPD, with tolerant genotypes having significantly lower TR than sensitive ones, especially at times with the highest VPD. Genotypes differed in TR response to increasing VPD, with some tolerant genotypes exhibiting a clear VPD breakpoint at about 2.25?kPa, above which there was very little increase in TR. In contrast, sensitive genotypes presented a linear increase in TR as VPD increased, and the same pattern was found in some tolerant lines, but with a smaller slope. CT, estimated with thermal imagery, correlated well with TR and Ig and could therefore be used as proxy for TR. These results indicate that control of water loss discriminated between tolerant and sensitive genotypes and may, therefore, be a reliable indicator of terminal drought stress tolerance. The water-saving characteristics of some genotypes are hypothesised to leave more soil water for pod filling, which is crucial for terminal drought adaptation. PMID:22823007

  17. Nutrient availability moderates transpiration in Ehrharta calycina.

    PubMed

    Cramer, Michael D; Hoffmann, Vera; Verboom, G Anthony

    2008-01-01

    Transpiration-driven 'mass-flow' of soil-water can increase nutrient flow to the root surface. Here it was investigated whether transpiration could be partially regulated by nutrient status. Seeds of Ehrharta calycina from nine sites across a rainfall gradient were supplied with slow-release fertilizer dibbled into the sand surrounding the roots and directly available through interception, mass-flow and diffusion (dubbed 'interception'), or sequestered behind a 40-microm mesh and not directly accessible by the roots, but from which nutrients could move by diffusion or mass-flow (dubbed 'mass-flow'). Although mass-flow plants were significantly smaller than interception plants as a consequence of nutrient limitation, they transpired 60% faster, had 90% higher photosynthesis relative to transpiration (A/E), and 40% higher tissue P, Ca and Na concentrations than plants allowed to intercept nutrients directly. Tissue N and K concentrations were similar for interception and mass-flow plants. Transpiration was thus higher in the nutrient-constrained 'mass-flow' plants, increasing the transport of nutrients to the roots by mass-flow. Transpiration may have been regulated by N availability, resulting in similar tissue concentration between treatments. It is concluded that, although transpiration is a necessary consequence of photosynthetic CO(2) uptake in C(3) plants, plants can respond to nutrient limitation by varying transpiration-driven mass-flow of nutrients. PMID:18537891

  18. Impact of photosynthesis and transpiration on nitrogen removal in constructed wetlands

    Microsoft Academic Search

    Weiguo Luo; Shihe Wang; Juan Huang; Lu Yan; Jun Huang

    2007-01-01

    To determine the impact of photosynthesis and transpiration on nitrogen removal in wetlands, an artificial wetland planted\\u000a with reeds was constructed to treat highly concentrated domestic wastewater. Under different meteorological and hydraulic\\u000a conditions, the daily changes of photosynthesis and transpiration of reeds, as well as nitrogen removal efficiency were measured.\\u000a It was found that net photosynthesis rate per unit leaf

  19. Responses of transpiration and canopy conductance to partial defoliation of Eucalyptus globulus trees

    Microsoft Academic Search

    Audrey G. Quentin; Anthony P. O’Grady; Christopher L. Beadle; Dale Worledge; Elizabeth A. Pinkard

    2011-01-01

    Partial defoliation has been shown to affect the water relations and transpiration (gas exchange) of plants. Over one growing season, the water relations in response to partial (?45%) defoliation were examined in four-year-old Eucalyptus globulus trees in southern Australia. Daily maximum transpiration rates (Emax), maximum canopy conductance (GCmax), and diurnal patterns of tree water-use were measured over a period of

  20. Near-optimal response of instantaneous transpiration efficiency to vapour pressure deficit, temperature and [CO2] in cotton (Gossypium hirsutum L.).

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The instantaneous transpiration efficiency (ITE, the ratio of photosynthesis rate to transpiration) is an important variable for crops, because it ultimately affects dry mass production per unit of plant water lost to the atmosphere. The theory that stomata optimize carbon uptake per unit water used...

  1. Maize transpiration in response to meteorological conditions

    NASA Astrophysics Data System (ADS)

    Klimešová, Jana; St?edová, Hana; St?eda, Tomáš

    2013-09-01

    Differences in transpiration of maize (Zea mays L.) plants in four soil moisture regimes were quantified in a pot experiment. The transpiration was measured by the "Stem Heat Balance" method. The dependence of transpiration on air temperature, air humidity, global solar radiation, soil moisture, wind speed and leaf surface temperature were quantified. Significant relationships among transpiration, global radiation and air temperature (in the first vegetation period in the drought non-stressed variant, r = 0.881**, r = 0.934**) were found. Conclusive dependence of transpiration on leaf temperature (r = 0.820**) and wind speed (r = 0.710**) was found. Transpiration was significantly influenced by soil moisture (r = 0.395**, r = 0.528**) under moderate and severe drought stress. The dependence of transpiration on meteorological factors decreased with increasing deficiency of water. Correlation between transpiration and plant dry matter weight (r = 0.997**), plant height (r = 0.973**) and weight of corn cob (r = 0.987**) was found. The results of instrumental measuring of field crops transpiration under diverse moisture conditions at a concurrent monitoring of the meteorological elements spectra are rather unique. These results will be utilized in the effort to make calculations of the evapotranspiration in computing models more accurate.

  2. Steady state or non-steady state? Identifying driving mechanisms of oxygen isotope signatures of leaf transpiration in functionally distinct plant species

    NASA Astrophysics Data System (ADS)

    Dubbert, Maren; Kübert, Angelika; Cuntz, Matthias; Werner, Christiane

    2015-04-01

    Isotope techniques are widely applied in ecosystem studies. For example, isoflux models are used to separate soil evaporation from transpiration in ecosystems. These models often assume that plant transpiration occurs at isotopic steady state, i.e. that the transpired water shows the same isotopic signature as the source water. Yet, several studies found that transpiration did not occur at isotopic steady state, under both controlled and field conditions. Here we focused on identifying the internal and external factors which drive the isotopic signature of leaf transpiration. Using cavity ring-down spectroscopy (CRDS), the effect of both environmental variables and leaf physiological traits on ?18OT was investigated under controlled conditions. Six plant species with distinct leaf physiological traits were exposed to step changes in relative air humidity (RH), their response in ?18OT and gas exchange parameters and their leaf physiological traits were assessed. Moreover, two functionally distinct plant types (tree, i.e. Quercus suber, and grassland) of a semi-arid Mediterranean oak-woodland where observed under natural conditions throughout an entire growth period in the field. The species differed substantially in their leaf physiological traits and their turn-over times of leaf water. They could be grouped in species with fast (<60 min.), intermediate (ca. 120 min.) and slow (>240 min.) turn-over times, mostly due to differences in stomatal conductance, leaf water content or a combination of both. Changes in RH caused an immediate response in ?18OT, which were similarly strong in all species, while leaf physiological traits affected the subsequent response in ?18OT. The turn-over time of leaf water determined the speed of return to the isotopic steady or a stable ?18OT value (Dubbert & Kübert et al., in prep.). Under natural conditions, changes in environmental conditions over the diurnal cycle had a huge impact on the diurnal development of ?18OT in both observed plant functional types. However, in accordance with our findings in the lab, species specific differences in the leaf water turn over time, significantly influenced the amount of time plants transpired at non-steady state during the day (Dubbert et al., 2013, 2014). Our results emphasize the significance of considering isotopic non-steady state of transpiration and specifically to account for the specific differences of plant species resulting from distinct physiological traits of their leaves when applying isoflux models in ecosystem studies. Dubbert, M; Cuntz, M; Piayda, A; Maguas, C; Werner, C: Partitioning evapotranspiration - Testing the Craig and Gordon model with field measurements of oxygen isotope ratios of evaporative fluxes. J Hydrol (2013) Dubbert, M; Piayda, A; Cuntz, M; Correia, AC; Costa e Silva, F; Pereira, JS; Werner, C: Stable oxygen isotope and flux partitioning demonstrates understory of an oak savanna contributes up to half of ecosystem carbon and water exchange, Frontiers in Plant Science (2014a)

  3. Wind effects on leaf transpiration challenge the concept of "potential evaporation"

    NASA Astrophysics Data System (ADS)

    Schymanski, S. J.; Or, D.

    2015-06-01

    Transpiration is commonly conceptualised as a fraction of some potential rate, driven by so-called "atmospheric evaporative demand". Therefore, atmospheric evaporative demand or "potential evaporation" is generally used alongside with precipitation and soil moisture to characterise the environmental conditions that affect plant water use. Consequently, an increase in potential evaporation (e.g. due to climate change) is believed to cause increased transpiration and/or vegetation water stress. In the present study, we investigated the question whether potential evaporation constitutes a meaningful reference for transpiration and compared sensitivity of potential evaporation and leaf transpiration to atmospheric forcing. A physically-based leaf energy balance model was used, considering the dependence of feedbacks between leaf temperature and exchange rates of radiative, sensible and latent heat on stomatal resistance. Based on modelling results and supporting experimental evidence, we conclude that stomatal resistance cannot be parameterised as a factor relating transpiration to potential evaporation, as the ratio between transpiration and potential evaporation not only varies with stomatal resistance, but also with wind speed, air temperature, irradiance and relative humidity. Furthermore, the effect of wind speed in particular implies increase in potential evaporation, which is commonly interpreted as increased "water stress", but at the same time can reduce leaf transpiration, implying a decrease in water demand at leaf scale.

  4. Comparison of corn transpiration, eddy covariance, and soil water loss

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stem flow gages are used to estimate plant transpiration, but only a few studies compare transpiration with other measures of soil water loss. The purpose of this study was to compare transpiration from stem flow measurements with soil water changes estimated by daily neutron probe readings. Monitor...

  5. Uncertainty in sap flow-based transpiration due to xylem properties

    NASA Astrophysics Data System (ADS)

    Looker, N. T.; Hu, J.; Martin, J. T.; Jencso, K. G.

    2014-12-01

    Transpiration, the evaporative loss of water from plants through their stomata, is a key component of the terrestrial water balance, influencing streamflow as well as regional convective systems. From a plant physiological perspective, transpiration is both a means of avoiding destructive leaf temperatures through evaporative cooling and a consequence of water loss through stomatal uptake of carbon dioxide. Despite its hydrologic and ecological significance, transpiration remains a notoriously challenging process to measure in heterogeneous landscapes. Sap flow methods, which estimate transpiration by tracking the velocity of a heat pulse emitted into the tree sap stream, have proven effective for relating transpiration dynamics to climatic variables. To scale sap flow-based transpiration from the measured domain (often <5 cm of tree cross-sectional area) to the whole-tree level, researchers generally assume constancy of scale factors (e.g., wood thermal diffusivity (k), radial and azimuthal distributions of sap velocity, and conducting sapwood area (As)) through time, across space, and within species. For the widely used heat-ratio sap flow method (HRM), we assessed the sensitivity of transpiration estimates to uncertainty in k (a function of wood moisture content and density) and As. A sensitivity analysis informed by distributions of wood moisture content, wood density and As sampled across a gradient of water availability indicates that uncertainty in these variables can impart substantial error when scaling sap flow measurements to the whole tree. For species with variable wood properties, the application of the HRM assuming a spatially constant k or As may systematically over- or underestimate whole-tree transpiration rates, resulting in compounded error in ecosystem-scale estimates of transpiration.

  6. Leaf senescence in rice due to magnesium deficiency mediated defect in transpiration rate before sugar accumulation and chlorosis.

    PubMed

    Kobayashi, Natsuko I; Saito, Takayuki; Iwata, Naoko; Ohmae, Yoshimi; Iwata, Ren; Tanoi, Keitaro; Nakanishi, Tomoko M

    2013-08-01

    Magnesium (Mg) is an essential macronutrient supporting various functions, including photosynthesis. However, the specific physiological responses to Mg deficiency remain elusive. In this study, 2-week-old rice seedlings (Oryza sativa. cv. Nipponbare) with three expanded leaves (L2-L4) were transferred to Mg-free nutrient solution for 8 days. In the absence of Mg, on day 8, L5 and L6 were completely developed, while L7 just emerged. We also studied several mineral deficiencies to identify specific responses to Mg deficiency. Each leaf was analyzed in terms of chlorophyll, starch, anthocyanin and carbohydrate metabolites, and only absence of Mg was found to cause irreversible senescence of L5. Resupply of Mg at various time points confirmed that the borderline of L5 death was between days 6 and 7 of Mg deficiency treatment. Decrease in chlorophyll concentration and starch accumulation occurred simultaneously in L5 and L6 blades on day 8. However, nutrient transport drastically decreased in L5 as early as day 6. These data suggest that the predominant response to Mg deficiency is a defect in transpiration flow. Furthermore, changes in myo-inositol and citrate concentrations were detected only in L5 when transpiration decreased, suggesting that they may constitute new biological markers of Mg deficiency. PMID:23176135

  7. Leaf senescence in rice due to magnesium deficiency-mediated defect in transpiration rate before sugar accumulation and chlorosis.

    PubMed

    Kobayashi, Natsuko I; Saito, Takayuki; Iwata, Naoko; Ohmae, Yoshimi; Iwata, Ren; Tanoi, Keitaro; Nakanishi, Tomoko M

    2012-10-26

    Magnesium (Mg) is an essential macronutrient supporting various functions, including photosynthesis. However, the specific physiological responses to Mg deficiency remain elusive. In this study, 2-week-old rice seedlings (Oryza sativa. cv. Nipponbare) with 3 expanded leaves (L2-L4) were transferred to Mg-free nutrient solution for 8 days. In the absence of Mg, on day 8, L5 and L6 were completely developed, while L7 just emerged. We also studied several mineral deficiencies to identify specific responses to Mg deficiency. Each leaf was analyzed in terms of chlorophyll, starch, anthocyanin, and carbohydrate metabolites, and only absence of Mg was found to cause irreversible senescence of L5. Resupply of Mg at various time points confirmed that the borderline of L5 death was between days 6 and 7 of Mg deficiency treatment. Decrease in chlorophyll concentration and starch accumulation occurred simultaneously in L5 and L6 blades on day 8. However, nutrient transport drastically decreased in L5 as early as day 6. These data suggest that the predominant response to Mg deficiency is a defect in transpiration flow. Furthermore, changes in myo-inositol and citrate concentrations were detected only in L5 when transpiration decreased, suggesting that they may constitute new biological markers of Mg deficiency. PMID:23106221

  8. Response of tomato plants to a step-change in root-zone salinity under two different transpiration regimes

    Microsoft Academic Search

    Ya Ling Li; Cecilia Stanghellini; Hugo Challa

    2002-01-01

    The response of a tomato crop to a step-change in salinity was investigated under different potential transpiration conditions. A crop growing for 5 months under saline irrigation water (EC 9dSm?1) was given thereafter a standard nutrient solution with an EC of 2dSm?1. The previous effects of salinity were largely reversed, especially for fruits and leaves that had not yet reached

  9. Diurnal courses and factorial dependencies of leaf conductance and transpiration of differently potassium fertilized and watered field grown barley plants

    Microsoft Academic Search

    R. Lösch; C. R. Jensen; M. N. Andersen

    1992-01-01

    During the grain filling period we followed diurnal courses in leaf water potential (?1), leaf osmotic potential (??), transpiration (E), leaf conductance to water vapour transfer (g) and microclimatic parameters in field-grown spring barley\\u000a (Hordeum distichum L. cv. Gunnar). The barley crop was grown on a coarse textured sandy soil at low (50 kg ha?1) or high (200 kg ha?1)

  10. AIR HUMIDITY WITHIN BOUNDARYLAYER OF A TRANSPIRING LEAF I. RELATIONSHIP BETWEEN TRANSPIRATION AND WATER VAPOR DENSITY AT LEAF SURFACE

    Microsoft Academic Search

    M. KITANO; H. EGUCHI

    KITANO M. and EGUCHI H. Air humidity within boundary layer ofa transpiring leaf. 1. Relationship between transpiration and water vapor density at leafsurface. BIOTRONICS 16, 39-45, 1987. A simple system for on-line measurement of water vapor density within leaf boundary layer was developed, and water vapor density (WBO) at the cucumber leaf surface was analyzed in relation to transpiration rate

  11. The function of nocturnal transpiration

    NASA Astrophysics Data System (ADS)

    Pfautsch, Sebastian; Resco de Dios, Víctor; Loik, Michael; Tissue, David

    2014-05-01

    Nocturnal transpiration is an important source of water loss, accounting for up to 25% of daytime transpiration in some species. Nocturnal water losses cannot be explained under the prevailing 'paradigm' of optimizing carbon gain while minimizing water loss because carbon fixation does not occur at night. Alternative explanations regarding the function and potential evolutionary advantage of nocturnal transpiration have been proposed, such as enhanced nutrient uptake and transport or delivery of O2 to parenchyma cells for respiration. However, recent evidence suggests that the role of nocturnal transpiration in supplementing the overall plant nutrient budget is relatively small, and the O2 hypothesis is difficult to test experimentally. Here, we propose that the main function of nocturnal transpiration (and water transport) is to prevent catastrophic xylem failure by restoring depleted stem 'capacitors' and enhancing early morning CO2 uptake, as stomata 'prepare' for daytime conditions. Nocturnal sap flux was highest in Eucalyptus grandis trees in the field following a heat wave (reaching 47C with VPDs > 8kPa in the daytime) generating maximal daytime water losses compared with cooler and lower VPD periods, indicating the importance of nocturnal stomatal conductance for stem refilling. Moreover, we observed that the time for stomata to respond to light early in the morning (dawn) across 25 different genotypes of E. camaldulensis in a glasshouse was shortest in those genotypes with highest nocturnal stomatal conductance, which was also correlated with higher daytime photosynthesis. This observation is consistent with previous observations that nocturnal stomatal conductance is partially controlled by the clock, which is utilised to anticipate daytime conditions. Data from the literature suggests that eucalypts respond similarly to other C3 species, suggesting that mechanisms regulating night-time transpiration may be universal.

  12. Simple relations for different stomatal control mechanisms link partially drying soil and transpiration

    NASA Astrophysics Data System (ADS)

    Huber, Katrin; Vanderborght, Jan; Javaux, Mathieu; Vereecken, Harry

    2015-04-01

    Stomata can close to regulate plant water loss under unfavourable water availability. This closure can be triggered by hydraulic ('H') and/or chemical signals ('C', 'H+C'). By combining plant hydraulic relations with a model for stomatal conductance, including chemical signalling, our aim was to derive a simple relation that links soil water availability, expressed as the fraction of roots in dry soil, to transpiration. We used the detailed mechanistic soil-root water flow model R-SWMS to verify this relation. Virtual split root experiments were simulated, comparing horizontally and vertically split domains with varying fractions of roots in dry soil and comparing different strengths of stomatal regulation by chemical and hydraulic signals. Transpiration predicted by the relation was in good agreement with numerical simulations. Under certain conditions H+C control leads to isohydric plant behaviour, which means that stomata close to keep leaf water potential constant after reaching a certain level. C control on the other hand exerts anisohydric behaviour, meaning that stomata remain fully open during changes in leaf water potential. For C control the relation between transpiration reduction and fraction of roots in dry soil becomes independent of transpiration rate whereas H+C control results in stronger reduction for higher transpiration rates. Simple relations that link effective soil and leaf water potential can describe different stomatal control resulting in contrasting behaviour.

  13. Genetic variability for leaf growth rate and duration under water deficit in sunflower: analysis of responses at cell, organ, and plant level

    Microsoft Academic Search

    Gustavo A. Pereyra-Irujo; Luciano Velazquez; Leandra Lechner; Luis A. N. Aguirrezabal

    2008-01-01

    Plants under water deficit reduce leaf growth, thereby reducing transpiration rate at the expense of reduced photosynthesis. The objective of this work was to analyse the response of leaf growth to water deficit in several sunflower genotypes in order to identify and quantitatively describe sources of genetic variability for this trait that could be used to develop crop varieties adapted

  14. Plant Populations and Seeding Rates for Soybeans

    E-print Network

    Holland, Jeffrey

    Plant Populations and Seeding Rates for Soybeans Andrew P. Robinson Department of Agronomy www input costs for soybean growers, so it's important for growers to plant the right amount of seed to minimize input costs and increase profitability. Seeding rate, plant population, and row spacing are tied

  15. Seasonal, synoptic and diurnal variation of atmospheric water-isotopologues in the boundary layer of Southwestern Germany caused by plant transpiration, cold-front passages and dewfall.

    NASA Astrophysics Data System (ADS)

    Christner, Emanuel; Dyroff, Christoph; Kohler, Martin; Zahn, Andreas; Gonzales, Yenny; Schneider, Matthias

    2013-04-01

    Atmospheric water is an enormously crucial trace gas. It is responsible for ~70 % of the natural greenhouse effect (Schmidt et al., JGR, 2010) and carries huge amounts of latent heat. The isotopic composition of water vapor is an elegant tracer for a better understanding and quantification of the extremely complex and variable hydrological cycle in Earth's atmosphere (evaporation, cloud condensation, rainout, re-evaporation, snow), which in turn is a prerequisite to improve climate modeling and predictions. As H216O, H218O and HDO differ in vapor pressure and mass, isotope fractionation occurs due to condensation, evaporation and diffusion processes. In contrast to that, plants are able to transpire water with almost no isotope fractionation. For that reason the ratio of isotopologue concentrations in the boundary layer (BL) provides, compared to humidity measurements alone, independent and additional constraints for quantifying the strength of evaporation and transpiration. Furthermore the isotope ratios contain information about transport history of an air mass and microphysical processes, that is not accessible by humidity measurements. Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) a commercial Picarro Analyzer L2120-i is operated at Karlsruhe in Southwestern Germany, which is continuously measuring the isotopologues H216O, HDO and H218O of atmospheric water vapor since January 2012. A one year record of H216O, HDO and H218O shows clear seasonal, synoptic and diurnal characteristics and reveals the main driving processes affecting the isotopic composition of water vapor in the Middle European BL. Changes in continental plant transpiration and evaporation throughout the year lead to a slow seasonal HDO/H216O-variation, that cannot be explained by pure Rayleigh condensation. Furthermore, cold-front passages from NW lead to fast and pronounced depletion of the HDO/H216O-ratio within minutes. Superimposed to these variations are local diurnal processes like dewfall, which cause a diurnal pattern captured by the deuterium excess.

  16. Influence of Transpiration Suppressants, Sprinkler Irrigation and Moisture Levels on Transpiration and Evapotranspiration 

    E-print Network

    Gerard, C. J.

    1970-01-01

    determined. Microclimatic data as influenced by treatments were determined. Estimates of influences of treatments on transpiration were evaluated with thermoelectric sensors. Tomato and citrus plant parts were analyzed for certain chemical properties. Diurnal...

  17. Estimation of Transpiration and Water Use Efficiency Using Satellite and Field Observations

    NASA Technical Reports Server (NTRS)

    Choudhury, Bhaskar J.; Quick, B. E.

    2003-01-01

    Structure and function of terrestrial plant communities bring about intimate relations between water, energy, and carbon exchange between land surface and atmosphere. Total evaporation, which is the sum of transpiration, soil evaporation and evaporation of intercepted water, couples water and energy balance equations. The rate of transpiration, which is the major fraction of total evaporation over most of the terrestrial land surface, is linked to the rate of carbon accumulation because functioning of stomata is optimized by both of these processes. Thus, quantifying the spatial and temporal variations of the transpiration efficiency (which is defined as the ratio of the rate of carbon accumulation and transpiration), and water use efficiency (defined as the ratio of the rate of carbon accumulation and total evaporation), and evaluation of modeling results against observations, are of significant importance in developing a better understanding of land surface processes. An approach has been developed for quantifying spatial and temporal variations of transpiration, and water-use efficiency based on biophysical process-based models, satellite and field observations. Calculations have been done using concurrent meteorological data derived from satellite observations and four dimensional data assimilation for four consecutive years (1987-1990) over an agricultural area in the Northern Great Plains of the US, and compared with field observations within and outside the study area. The paper provides substantive new information about interannual variation, particularly the effect of drought, on the efficiency values at a regional scale.

  18. PILOT PLANT EXPLORATION OF SLOW RATE FILTRATION

    EPA Science Inventory

    Alternatives to conventional coagulation water filtration plants (those that utilize coagulation, flocculation, sedimentation and filtration) may be appropriate for some small water utilities. One such alternative is slow rate filtration. This paper describes pilot plant studies ...

  19. Terrestrial water fluxes dominated by transpiration.

    PubMed

    Jasechko, Scott; Sharp, Zachary D; Gibson, John J; Birks, S Jean; Yi, Yi; Fawcett, Peter J

    2013-04-18

    Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km(3) per year) (refs 1, 2, 3, 4, 5). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth's continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 ± 8,000 km(3) of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 ± 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes. PMID:23552893

  20. Transpiration: A Test of Optimality Hypothesis

    NASA Astrophysics Data System (ADS)

    Wang, J.; Bras, R. L.; Lerdau, M.; Salvucci, G. D.; Wofsy, S.

    2003-12-01

    The argument is that the fundamental mechanisms behind bare soil evaporation are also responsible for plant transpiration except that stomata affect the exchange of water vapor between the evaporating surface and the atmosphere. It is hypothesized that the system of liquid water in leaf tissues and the water vapor in the atmosphere tries to evolve towards a potential equilibrium as quickly as possible by maximizing transpiration. In the proposed theory, CO2 flux is used as a non-parametric equivalent of stomatal conductance as CO2 and water vapor diffuse in and out of leaves through the same path. It is further assumed that stomatal aperture is directly controlled by guard cell turgor (or leaf water potential). Transpiration is formulated as a function of leaf temperature, leaf water potential/stomatal conductance (or CO2 flux as the surrogate), and sensible heat flux (characterizing transport mechanism) at a given level of radiative energy input. Optimization of transpiration constrained by the energy balance equation leads to vanishing derivatives of transpiration with respect to leaf temperature and CO2 flux. Effect of vapor pressure deficit on transpiration is also investigated. Preliminary tests using field experimental measurements lead to encouraging evidence in support of the hypothesis. It is found that transpiration is fairly insensitive to atmospheric humidity as suggested by several earlier studies.

  1. The contribution of large trees to total transpiration rates in a pre-montane tropical forest and its implications for selective logging practices

    NASA Astrophysics Data System (ADS)

    Orozco, G.; Moore, G. W.; Miller, G. R.

    2012-12-01

    In the humid tropics, conservationists generally prefer selective logging practices over clearcutting. Large valuable timber is removed while the remaining forest is left relatively undisturbed. However, little is known about the impact of selective logging on site water balance. Because large trees have very deep sapwood and exposed canopies, they tend to have high transpiration. The first objective was to evaluate the methods used for scaling sap flow measurements to the watershed with particular emphasis on large trees. The second objective of this study was to determine the relative contribution of large trees to site water balance. Our study was conducted in a pre-montane transitional forest at the Texas A&M University Soltis Center in north-central Costa Rica. During the period between January and July 2012, sap flux was monitored in a 30-m diameter plot within a 10-ha watershed. Two pairs of heat dissipation sensors were installed in the outer 0-20 mm of each of 15 trees selected to represent the full range of tree sizes. In six of the largest trees, depth profiles were recorded at 10-mm intervals to a depth of 60 mm using compensation heat pulse sensors. To estimate sapwood basal area of the entire watershed, a stand survey was conducted in three 30-m-diameter plots. In each plot, we measured basal area of all trees and estimated sapwood basal area from sapwood depth measured in nearly half of the trees. An estimated 36.5% of the total sapwood area in this watershed comes from the outer 20 mm of sapwood, with the remaining 63.5% of sapwood from depths deeper than 20 mm. Nearly 13% of sapwood is from depths beyond 60 mm. Sap velocity profiles indicate the highest flow rates occurred in the 0-2 cm depths, with declines of 17% and 25% in the 20-40 mm and 40-60 mm ranges, respectively. Our results demonstrate the need to measure sap velocity profiles in large tropical trees. If total transpiration had been estimated solely from the 0-20 mm heat dissipation probes, it would have been overestimated by at least 15%. Total transpiration averaged 1.49 mm over the 6-month study period. However, the largest 10% of trees contributed disproportionately to this amount. Trees greater than 110 cm in diameter represented over half of the total basal area and 32% of the total sapwood area. These results highlight the importance of large trees in estimating watershed-scale transpiration. From a forest management perspective, selectively logging only the very largest trees, a common practice among these tropical forests of Costa Rica, is likely to disproportionately impact the site water balance unless water use of smaller trees can fully compensate.

  2. Transpiration and CO/sub 2/ fixation of selected desert shrubs as related to soil-water potential

    SciTech Connect

    Clark, S.B.; Letey, J. Jr.; Lunt, O.R.; Wallace, A.; Kleinkopf, G.E.; Romney, E.M.

    1980-01-01

    In desert plants, transpiration rates decreased before photosynthetic rates when plants were entering a period of water stress. This may have adaptive consequences. A difference of -5 bars in the soil-moisture potential had considerable importance in reducing the rate of transpiration. In Helianthus annuus L. (sunflower) the photosynthetic rate decreased before the transpiration rate in contrast to Great Basin-Mojave Desert plants, and the changes occurred with a -1 bar difference in soil-moisture potential. Morphological changes in three desert plant species (Artemisia tridentata Nutt., Ambrosia dumosa (Gray) Payne, Larrea tridentata (Ses. Moc. ex DC) Cov.) as the soil-moisture potential decreased are given. With a mesic species, H. annuus, 20% reduction in photosynthesis and transpiration was reached at higher soil-moisture potentials than with the desert plants. Loss of net photosynthesis occurred in A. dumosa (a summer deciduous shrub) as PSI soil reached -48 bars in the field, whereas L. tridentata (an evergreen shrub) at the same time was able to maintain a water potential difference between soil and plant of -10 to -15 bars and continue net CO/sub 2/ gain well into the summer months.

  3. Stem girdling evidences a trade-off between cambial activity and sprouting and dramatically reduces plant transpiration due to feedback inhibition of photosynthesis and hormone signaling

    PubMed Central

    López, Rosana; Brossa, Ricard; Gil, Luis; Pita, Pilar

    2015-01-01

    The photosynthesis source–sink relationship in young Pinus canariensis seedlings was modified by stem girdling to investigate sprouting and cambial activity, feedback inhibition of photosynthesis, and stem and root hydraulic capacity. Removal of bark tissue showed a trade-off between sprouting and diameter growth. Above the girdle, growth was accelerated but the number of sprouts was almost negligible, whereas below the girdle the response was reversed. Girdling resulted in a sharp decrease in whole plant transpiration and root hydraulic conductance. The reduction of leaf area after girdling was strengthened by the high levels of abscisic acid found in buds which pointed to stronger bud dormancy, preventing a new needle flush. Accumulation of sugars in leaves led to a coordinated reduction in net photosynthesis (AN) and stomatal conductance (gS) in the short term, but later (gS below 0.07 mol m-2 s-1) AN decreased faster. The decrease in maximal efficiency of photosystem II (FV/FM) and the operating quantum efficiency of photosystem II (?PSII) in girdled plants could suggest photoprotection of leaves, as shown by the vigorous recovery of AN and ?PSII after reconnection of the phloem. Stem girdling did not affect xylem embolism but increased stem hydraulic conductance above the girdle. This study shows that stem girdling affects not only the carbon balance, but also the water status of the plant. PMID:25972884

  4. Export of Abscisic Acid, 1-Aminocyclopropane-1-Carboxylic Acid, Phosphate, and Nitrate from Roots to Shoots of Flooded Tomato Plants (Accounting for Effects of Xylem Sap Flow Rate on Concentration and Delivery).

    PubMed Central

    Else, M. A.; Hall, K. C.; Arnold, G. M.; Davies, W. J.; Jackson, M. B.

    1995-01-01

    We determined whether root stress alters the output of physiologically active messages passing from roots to shoots in the transpiration stream. Concentrations were not good measures of output. This was because changes in volume flow of xylem sap caused either by sampling procedures or by effects of root stress on rates of whole-plant transpiration modified concentrations simply by dilution. Thus, delivery rate (concentration x sap flow rate) was preferred to concentration as a measure of solute output from roots. To demonstrate these points, 1-aminocyclopropane-1-carboxylic acid (ACC), abscisic acid, phosphate, nitrate, and pH were measured in xylem sap of flooded and well-drained tomato (Lycopersicon esculentum Mill., cv Ailsa Craig) plants expressed at various rates from pressurized detopped roots. Concentrations decreased as sap flow rates were increased. However, dilution of solutes was often less than proportional to flow, especially in flooded plants. Thus, sap flowing through detopped roots at whole-plant transpiration rates was used to estimate solute delivery rates in intact plants. On this basis, delivery of ACC from roots to shoots was 3.1-fold greater in plants flooded for 24 h than in well-drained plants, and delivery of phosphate was 2.3-fold greater. Delivery rates of abscisic acid and nitrate in flooded plants were only 11 and 7%, respectively, of those in well-drained plants. PMID:12228364

  5. Transpiration: How Much Water Does a Tree Transpire in One Day?

    NSDL National Science Digital Library

    This activity has students construct a small terrarium that will allow them to observe and measure the water given off through transpiration. Students will be able to recognize transpiration and explain its value to the plant. They will also be able to explain how transpiration affects climate. The student's guide has an overall description of the activity, a list of materials, the procedure, and observations and questions. The teacher's guide contains detailed background material, learning goals, alignment to national standards, grade level/time, details on materials and preparation, procedure, assessment ideas, and modifications for alternative learners.

  6. Gas exchange rates at different vapor pressure deficits and water relations of ‘Pera’ sweet orange plants with citrus variegated chlorosis (CVC)

    Microsoft Academic Search

    Gustavo Habermann; Eduardo Caruso Machado; João Domingos Rodrigues; Camilo Lázaro Medina

    2003-01-01

    Net photosynthesis (A) and transpiration rates (E), stomatal conductance (g), water use efficiency (WUE), intrinsic water use efficiency (IWUE) and internal leaf CO2 concentration (Ci) in response to different vapor pressure deficit (1.2 and 2.5kPa) were investigated in ‘Pera’ sweet orange plants affected by citrus variegated chlorosis (CVC), a disease caused by Xylella fastidiosa. All plants were well watered and

  7. Numerical Analysis of Convection/Transpiration Cooling

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale

    1999-01-01

    An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.

  8. Numerical Analysis of Convection/Transpiration Cooling

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Dilley, Arthur D.; Kelly, H. Neale

    1999-01-01

    An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux, high temperature environment such as hypersonic vehicle engine combustor walls. A boundary layer code and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature. The boundary, layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant. The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.

  9. Tritium Concentrations in Environmental Samples and Transpiration Rates from the Vicinity of Mary's Branch Creek and Background Areas, Barnwell, South Carolina, 2007-2009

    USGS Publications Warehouse

    Vroblesky, Don A.; Canova, Judy L.; Bradley, Paul M.; Landmeyer, James E.

    2009-01-01

    Tritium in groundwater from a low-level radioactive waste disposal facility near Barnwell, South Carolina, is discharging to Mary's Branch Creek. The U.S. Geological Survey conducted an investigation from 2007 to 2009 to examine the tritium concentration in trees and air samples near the creek and in background areas, in groundwater near the creek, and in surface water from the creek. Tritium was found in trees near the creek, but not in trees from background areas or from sites unlikely to be in direct root contact with tritium-contaminated groundwater. Tritium was found in groundwater near the creek and in the surface water of the creek. Analysis of tree material has the potential to be a useful tool in locating shallow tritium-contaminated groundwater. A tritium concentration of 1.4 million picocuries per liter was measured in shallow groundwater collected near a tulip poplar located in an area of tritium-contaminated groundwater discharge. Evapotranspiration rates from the tree and tritium concentrations in water extracted from tree cores indicate that during the summer, this tulip poplar may remove more than 17.1 million picocuries of tritium per day from the groundwater that otherwise would discharge to Mary's Branch Creek. Analysis of air samples near the tree showed no evidence that the transpirative release of tritium to the air created a vapor hazard in the forest.

  10. A high CO2 -driven decrease in plant transpiration leads to perturbations in the hydrological cycle and may link terrestrial and marine loss of biodiversity: deep-time evidence.

    NASA Astrophysics Data System (ADS)

    Steinthorsdottir, Margret; Woodward, F. Ian; Surlyk, Finn; McElwain, Jennifer C.

    2013-04-01

    CO2 is obtained and water vapor simultaneously transpired through plant stomata, driving the water uptake of roots. Stomata are key elements of the Earth's hydrological cycle, since a large part of the evapotranspiration from the surface to the atmosphere takes place via stomatal pores. Plants exercise stomatal control, by adjusting stomatal size and/or density in order to preserve water while maintaining carbon uptake for photosynthesis. A global decrease in stomatal density and/or size causes a decrease in transpiration and has the potential to increase global runoff. Here we show, from 91 fossil leaf cuticle specimens from the Triassic/Jurassic boundary transition (Tr-J) of East Greenland, that both stomatal size and density decreased dramatically during the Tr-J, coinciding with mass extinctions, major environmental upheaval and a negative C-isotope excursion. We estimate that these developmental and structural changes in stomata resulted in a 50-60% drop in stomatal and canopy transpiration as calibrated using a stomatal model, based on empirical measurements and adjusted for fossil plants. We additionally present new field evidence indicating a change to increased erosion and bad-land formation at the Tr-J. We hypothesize that plant physiological responses to high carbon dioxide concentrations at the Tr-J may have increased runoff at the local and perhaps even regional scale. Increased runoff may result in increased flux of nutrients from land to oceans, leading to eutrophication, anoxia and ultimately loss of marine biodiversity. High-CO2 driven changes in stomatal and canopy transpiration therefore provide a possible mechanistic link between terrestrial ecological crisis and marine mass extinction at the Tr-J.

  11. Measurement of transpiration in Pinus taeda L. and Liquidambar styraciflua L. in an environmental chamber using tritiated water

    NASA Technical Reports Server (NTRS)

    Levy, G. F.; Sonenshine, D. E.; Czoch, J. K.

    1976-01-01

    Transpiration rates of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) were measured at two different atmospheric water vapor pressure deficits (V.P.D.) in a controlled environment growth chamber using tritiated water as a tracer. The trees were maintained in a sealed plant bed containing a hydroponic nutrient solution into which labeled water (spike) was introduced. Samples of leaves, chamber air, spiked nutrient solution and control water were assayed for ratio-activity using liquid scintillation techniques to determine transpiration rates. The transpiration rate of sweetgum in ml./hr./gm. (4.95) was found to be 5 times greater than that of loblolly pine (1.03) at 1.84 V.P.D. and 8 times greater at 6.74 V.P.D. (15.99 for sweetgum vs. 2.19 for pine). Transpiration (based on measurements of leaf radioactivity) in both species rose with increasing deficit; however sweetgum increased its output by 3 times while pine only doubled its rate. Cyclical changes in transpiration rates were noted in both species; the sweetgum cycle required a 6 hour interval whereas the pine cycle required a 9 hour interval.

  12. Correlation of thermophoretically-modified small particle diffusional deposition rates in forced convection systems with variable properties, transpiration cooling and/or viscous dissipation

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Rosner, D. E.

    1984-01-01

    A cooled object (heat exchanger tube or turbine blade) is considered to be immersed in a hot fluid stream containing trace amounts of suspended vapors and/or small particles. Numerical prediction calculations were done for self-similar laminar boundary layers and law-of-the-wall turbulent boundary layers. Correlations are presented for the effect of thermophoresis in the absence of transpiration cooling and viscous dissipation; the effect of real suction and blowing in the absence of thermophoresis; the effect of viscous dissipation on thermophoresis in the absence of transpiration cooling; and the combined effect of viscous dissipation and transpiration cooling on thermophoresis. The final correlation, St/St-sub-zero, is insensitive to particle properties, Euler number, and local mainstream temperature.

  13. Transpiration of apple trees in a humid climate using heat pulse sap flow gauges calibrated with whole-canopy gas exchange chambers

    Microsoft Academic Search

    D. Dragoni; A. N. Lakso; R. M. Piccioni

    2005-01-01

    For scientific study and practical irrigation management, the estimate of plant transpiration and water use rates is needed. Several methods are available to measure water use by plants, and among them, sap flow estimation techniques are currently popular, although the interpretation of data may be complex due to several assumptions. In this study, we present a combined approach to measure

  14. Transpiration and yield relationships of grain sorghum grown in a field environment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability of plants to convert transpiration into dry matter has been studied since the early 20th century. Research has compared differences among species using transpiration efficiency (TE), the ratio of biomass yield (Yb) to transpiration (T); and m and k, which are the slopes of the linear Yb...

  15. Effect of chemical closure of stomata on transpiration in varied soil and atmospheric environments

    Microsoft Academic Search

    D. Shimshi

    1963-01-01

    The effect of phenylmercuric acetate on transpiration and growth was measured on sunflowers growing outdoors and on tobacco growing in a greenhouse. There was a significant reduction in transpiration in both plants; no reduction in growth was observed in tobacco, whereas some damage was evident in the sunflowers. Phenylmercuric acetate reduced transpiration in tobacco equally whether the soil was wet

  16. Stomatal Closure in Flooded Tomato Plants lnvolves Abscisic Acid and a Chemically Unidentified AntiTranspirant in Xylem Sap

    Microsoft Academic Search

    Mark A. Else; Annemiek E. Tiekstra; Stephen J. Croker; William J. Davies; Michael B. Jackson

    We address the question of how soil flooding closes stomata of tomato (Lycopersicon esculentum Mill. cv Ailsa Craig) plants within a few hours in the absence of leaf water deficits. Three hypotheses to explain this were tested, namely that (a) flooding increases abscisic acid (ABA) export in xylem sap from roots, (b)'flooding increases ABA synthesis and export from older to

  17. Effects of Xylem pH on Transpiration from Wild-Type and flacca Tomato Leaves1

    PubMed Central

    Wilkinson, Sally; Corlett, Janet E.; Oger, Ludovic; Davies, William J.

    1998-01-01

    The pH of xylem sap from tomato (Lycopersicon esculentum) plants increased from pH 5.0 to 8.0 as the soil dried. Detached wild-type but not flacca leaves exhibited reduced transpiration rates when the artificial xylem sap (AS) pH was increased. When a well-watered concentration of abscisic acid (0.03 ?m) was provided in the AS, the wild-type transpirational response to pH was restored to flacca leaves. Transpiration from flacca but not from wild-type leaves actually increased in some cases when the pH of the AS was increased from 6.75 to 7.75, demonstrating an absolute requirement for abscisic acid in preventing stomatal opening and excessive water loss from plants growing in many different environments. PMID:9625724

  18. Transpiration: A Test of Optimality Hypothesis

    Microsoft Academic Search

    J. Wang; R. L. Bras; M. Lerdau; G. D. Salvucci; S. Wofsy

    2003-01-01

    The argument is that the fundamental mechanisms behind bare soil evaporation are also responsible for plant transpiration except that stomata affect the exchange of water vapor between the evaporating surface and the atmosphere. It is hypothesized that the system of liquid water in leaf tissues and the water vapor in the atmosphere tries to evolve towards a potential equilibrium as

  19. Regional variation in canopy transpiration of Central European beech forests

    Microsoft Academic Search

    Florian Schipka; Jutta Heimann; Christoph Leuschner

    2005-01-01

    Forest hydrologists have hypothesised that canopy transpiration (Ec) of European temperate forests occurs at rather similar rates in stands with different tree species and hydrologic regimes. We tested this hypothesis by synchronously measuring xylem sap flow in four mature stands of Fagus sylvatica along a precipitation gradient with the aim (1) of exploring the regional variability of annual canopy transpiration

  20. Wind speed effects on leaf energy balance, transpiration and water use efficiency

    NASA Astrophysics Data System (ADS)

    Schymanski, S. J.; Or, D.

    2014-12-01

    Transpiration and heat exchange rates by plant leaves involve coupled physiological processes of significant ecohydrological importance. Prediction of the effects of changing environmental conditions such as irradiance, temperature, humidity and wind speed requires a thorough understanding of these processes. The common assumption that leaf temperature equals air temperature may introduce significant bias into estimates of transpiration rates and water use efficiency (WUE, the amount of carbon gained by photosynthesis per unit of water lost by transpiration). Theoretical considerations and observations suggest that leaf temperatures may deviate substantially from air temperature under typical environmental conditions, leading to greatly modified transpiration rates compared to isothermal conditions. In particular, effects of wind on gas exchange must consider feedbacks with leaf temperature. Systematic quantification of the effects of wind speed on leaf heat and gas exchange rates yield some surprising insights. We found a range of conditions where increased wind speed can suppress transpiration rates. The result reflects unintuitive feedbacks between sensible heat flux, leaf temperature, leaf-to-air vapour pressure deficit and latent heat flux. Modelling results suggest that with high wind speeds the same leaf conductance (for water vapour and carbon dioxide) can be maintained with less evaporative losses. This leads to positive relation between water use efficiency and wind speed across a wide range of conditions. The presentation will report results from a lab experiment allowing separation of the different leaf energy balance components under fully controlled conditions (wind speed, temperature, humidity, irradiance) and put them into perspective with a detailed leaf energy balance model and the commonly used Penman-Monteith equation.

  1. The dynamic role of root-water uptake in coupling potential to actual transpiration

    E-print Network

    Katul, Gabriel

    The dynamic role of root-water uptake in coupling potential to actual transpiration Chun-Ta Lai a potential and actual transpiration and accounts for root-uptake eciency, potential transpiration rate, and root-density distribution was proposed and ®eld-tested. The total amount of water consumed by the root

  2. Direct impact of atmospheric CO2 enrichment on regional transpiration

    Microsoft Academic Search

    C. M. J. Jacobs

    1994-01-01

    Plant physiological research has revealed that stomatal aperture of many plant species is reduced by CO 2<\\/sub> . Therefore, the question has been raised as to how transpiration will be affected if the ambient C0 2<\\/sub> concentration increases. This study focuses on the prediction of changes in transpiration at the regional scale (10-100 km horizontal, 1-5 km vertical). A rather

  3. Beziehungen Zwischen Wurzelwachstum, Transpiration und CO 2 -Gaswechsel bei Einigen Kakteen

    Microsoft Academic Search

    Walter Kausch

    1965-01-01

    1.When roots of cacti which have been kept dry for many months are remoistened, absorbing roots are formed after a few hours.2.The transpiration rate increases rapidly within a day after the remoistening. This is an indication, that as soon as the roots appear, water-absorption begins immediately, and a rapid improvement of the water relationships in the plant occurs.3.The CO2-exchange of

  4. Transpiration Control Of Aerodynamics Via Porous Surfaces

    NASA Technical Reports Server (NTRS)

    Banks, Daniel W.; Wood, Richard M.; Bauer, Steven X. S.

    1993-01-01

    Quasi-active porous surface used to control pressure loading on aerodynamic surface of aircraft or other vehicle, according to proposal. In transpiration control, one makes small additions of pressure and/or mass to cavity beneath surface of porous skin on aerodynamic surface, thereby affecting rate of transpiration through porous surface. Porous skin located on forebody or any other suitable aerodynamic surface, with cavity just below surface. Device based on concept extremely lightweight, mechanically simple, occupies little volume in vehicle, and extremely adaptable.

  5. Evapotranspiration crop coefficients for mixed riparian plant community and transpiration crop coefficients for Common reed, Cottonwood and Peach-leaf willow in the Platte River Basin, Nebraska-USA

    NASA Astrophysics Data System (ADS)

    Irmak, S.; Kabenge, I.; Rudnick, D.; Knezevic, S.; Woodward, D.; Moravek, M.

    2013-02-01

    SummaryApplication of two-step approach of evapotranspiration (ET) crop coefficients (Kc) to "approximate" a very complex process of actual evapotranspiration (ETa) for field crops has been practiced by water management community. However, the use of Kc, and in particular the concept of growing degree days (GDD) to estimate Kc, have not been sufficiently studied for estimation of evaporative losses from riparian vegetation. Our study is one of the first to develop evapotranspiration crop coefficient (KcET) curves for mixed riparian vegetation and transpiration (TRP) crop coefficients (KcTRP) for individual riparian species as a function GDD through extensive field campaigns conducted in 2009 and 2010 in the Platte River Basin in central Nebraska, USA. KcTRP values for individual riparian vegetation species [Common reed (Phragmites australis), Cottonwood (Populus deltoids) and Peach-leaf willow (Salix amygdaloides)] were quantified from the TRP rates obtained using scaled-up canopy resistance from measured leaf-level stomatal resistance and reference evapotranspiration. The KcET and KcTRP curves were developed for alfalfa-reference (KcrET and KcrTRP) surface. The seasonal average mixed riparian plant community KcrET was 0.89 in 2009 and 1.27 in 2010. In 2009, the seasonal average KcrTRP values for Common reed, Cottonwood and Peach-leaf willow were 0.57, 0.51 and 0.62, respectively. In 2010, the seasonal average KcrTRP were 0.69, 0.62 and 0.83 for the same species, respectively. In general, TRP crop coefficients had less interannual variability than the KcrET. Response of the vegetation to flooding in 2010 played an important role on the interannual variability of KcrET values. We demonstrated good performance and reliability of developed GDD-based KcrTRP curves by using the curves developed for 2009 to predict TRP rates of individual species in 2010. Using the KcrTRP curves developed during the 2009 season, we were able to predict the TRP rates for Common reed, Cottonwood and Peach-leaf willow in 2010 within 7%, 8% and 13% accuracy, indicating a good performance of the two-step approach proposed in this study for estimating TRP for riparian vegetation. The surface conditions of the riparian ecosystem need to be considered when using the two-step approach to estimate ETa or TRP rates of riparian plant communities. The results of this study provide important water use information and data for riparian vegetation that can be used for more robust hydrologic/water balance analyses.

  6. Idaho Chemical Processing Plant failure rate database

    SciTech Connect

    Alber, T.G.; Hunt, C.R.; Fogarty, S.P.; Wilson, J.R.

    1995-08-01

    This report represents the first major upgrade to the Idaho Chemical Processing Plant (ICPP) Failure Rate Database. This upgrade incorporates additional site-specific and generic data while improving on the previous data reduction techniques. In addition, due to a change in mission at the ICPP, the status of certain equipment items has changed from operating to standby or off-line. A discussion of how this mission change influenced the relevance of failure data also has been included. This report contains two data sources: the ICPP Failure Rate Database and a generic failure rate database. A discussion is presented on the approaches and assumptions used to develop the data in the ICPP Failure Rate Database. The generic database is included along with a short discussion of its application. A brief discussion of future projects recommended to strengthen and lend credibility to the ICPP Failure Rate Database also is included.

  7. UBC Social Ecological Economic Development Studies (SEEDS) Student Report The Effect of Environmental Changes on the Photosynthesis and Transpiration of

    E-print Network

    of Environmental Changes on the Photosynthesis and Transpiration of Rates of Evergreen and Deciduous Trees during of Environmental Changes on the Photosynthesis and Transpiration of Rates of Evergreen and Deciduous Trees during in the photosynthesis (CO2 uptake and fixation) and transpiration (water loss) rates of evergreen and deciduous trees

  8. Influence of light intensity, temperature and humidity on photosynthesis and transpiration of Sasa nipponica and Arundinaria pygmaea

    Microsoft Academic Search

    Waichi Agata; Susumu Hakoyama; Yoshinobu Kawamitsu

    1985-01-01

    Photosynthesis and transpiration were simultaneously measured under different light intensity, temperature and humidity conditions\\u000a inSasa nipponica andArundinaria pygmaea grown in exposed and shaded habitats. Both species showed a saturated light curve for photosynthetic rate. The saturation\\u000a point was lower in shaded plants. The apparent quantum yields were larger inS. nipponica and in shaded plants, while the maximum photosynthesis was higher

  9. Elevated CO2 decreases both transpiration flow and concentrations of Ca and Mg in the xylem sap of wheat.

    PubMed

    Houshmandfar, Alireza; Fitzgerald, Glenn J; Tausz, Michael

    2015-02-01

    The impact of elevated atmospheric [CO2] (e[CO2]) on plants often includes a decrease in their nutrient status, including Ca and Mg, but the reasons for this decline have not been clearly identified. One of the proposed hypotheses is a decrease in transpiration-driven mass flow of nutrients due to decreased stomatal conductance. We used glasshouse and Free Air CO2 Enrichment (FACE) experiments with wheat to show that, in addition to decrease in transpiration rate, e[CO2] decreased the concentrations of Ca and Mg in the xylem sap. This result suggests that uptake of nutrients is not only decreased by reduced transpiration-driven mass flow, but also by as yet unidentified mechanisms that lead to reduced concentrations in the xylem sap. PMID:25462978

  10. Transpiration purged optical probe

    DOEpatents

    2004-01-06

    An optical apparatus for clearly viewing the interior of a containment vessel by applying a transpiration fluid to a volume directly in front of the external surface of the optical element of the optical apparatus. The fluid is provided by an external source and transported by means of an annular tube to a capped end region where the inner tube is perforated. The perforation allows the fluid to stream axially towards the center of the inner tube and then axially away from an optical element which is positioned in the inner tube just prior to the porous sleeve. This arrangement draws any contaminants away from the optical element keeping it free of contaminants. In one of several embodiments, the optical element can be a lens, a viewing port or a laser, and the external source can provide a transpiration fluid having either steady properties or time varying properties.

  11. Environmental and biological controls of urban tree transpiration in the Upper Midwest

    NASA Astrophysics Data System (ADS)

    Peters, E. B.; McFadden, J.; Montgomery, R.

    2009-12-01

    Urban trees provide a variety of ecosystem services to urban and suburban areas, including carbon uptake, climate amelioration, energy reduction, and stormwater management. Tree transpiration, in particular, modifies urban water budgets by providing an alternative pathway for water after rain events. The relative importance of environmental and biological controls on transpiration are poorly understood in urban areas, yet these controls are important for quantifying and scaling up the ecosystem services that urban trees provide at landscape and regional scales and predicting how urban ecosystems will respond to climate changes. The objectives of our study were to quantify the annual cycle of tree transpiration in an urban ecosystem and to determine how different urban tree species and plant functional types respond to environmental drivers. We continuously measured whole-tree transpiration using thermal dissipation sap flow at four urban forest stands that were broadly representative of the species composition and tree sizes found in a suburban residential neighborhood of Minneapolis-Saint Paul, Minnesota. A total of 40 trees, representing different species, plant functional types, successional stages, and xylem anatomy, were sampled throughout the 2007 and 2008 growing seasons (April-November). At each site we monitored soil moisture, air temperature, and relative humidity continuously, and we measured leaf area index weekly. Urban tree transpiration was strongly correlated with diurnal changes in vapor pressure deficit and photosynthetically active radiation and with seasonal changes in leaf area index. We found that plant functional type better explained species differences in transpiration per canopy area than either successional stage or xylem anatomy, largely due to differences in canopy structure between conifer and broad-leaf deciduous trees. We also observed inter-annual differences in transpiration rates due to a mid-season drought and longer growing season in 2007, compared with the cooler, wetter conditions in 2008. These results were scaled to estimate the relative contribution of each tree type at the scale of a suburban landscape. The findings of this study have implications for understanding the role of trees in managing urban water budgets and predicting the impacts of climate change on urban ecosystem services.

  12. Variability of Recombination Rates in Higher Plants

    Microsoft Academic Search

    Elisabeth Esch; Renate Horn

    \\u000a Recombination and chiasma frequency, like other features of meiosis, are subject to various genetic control mechanisms. Here,\\u000a we give an overview of the genetic and environmental factors as well as the genomic structures that play a role for the variability\\u000a of recombination rates in plant genomes. Suppressed or greatly reduced recombination is observed in chromosomal regions that\\u000a contain repetitive sequences

  13. Effects of potassium deficiency on water relations and photosynthesis of the tomato plant

    Microsoft Academic Search

    M. H. Behboudian; D. R. Anderson

    1990-01-01

    Potassium deficient (?K) and potassium sufficient (+K) plants were exposed to four days of water stress. Well watered ?K and\\u000a +K plants had comparable rates of transpiration. But +K plants had a larger leaf area and depleted the soil moisture to a\\u000a greater extent on day 1 of stress. For days 2 and 3 their transpiration rate, leaf water potential

  14. Effects of radiation, temperature and humidity on photosynthesis, transpiration and water use efficiency of oilseed rape ( Brassica campestris L.)

    Microsoft Academic Search

    D. P. Singh; N. C. Turner; H. M. Rawson

    1982-01-01

    The net photosynthetic rate (F), transpiration rate (Q) and water use efficiency (F\\/Q) of oilseed rape (Brassica campestris L. cv. Span) was studied under a range of atmospheric conditions by gas exchange techniques. The plants were at the full\\u000a bloom\\/pod initiation stage of development at the time of measurement. The environmental conditions consisted of various levels\\u000a of photosynthetically active radiation

  15. Vessel Contents During Transpiration-Embolisms and Refilling

    Microsoft Academic Search

    Martin J. Canny

    1997-01-01

    A test was made of the previous unexpected observation that embolized vessels were refilled during active transpiration. The contents of individual vessels in petioles of sunflower plants were examined, after snap-freezing at 2-h intervals during a day's transpiration, in the cryo-scanning electron microscope, and assessed for the presence of liquid or gas (embolism) contents. Concurrent measurements were made of irradiance,

  16. Original article Transpiration and stomatal conductance

    E-print Network

    Paris-Sud XI, Université de

    annual rainfall. transpiration / sap flow / stomatal conductance / air humidity / tropical speciesOriginal article Transpiration and stomatal conductance of two rain forest species growing (PET). This low transpiration level was explained by incomplete canopy closure and hence a low LAI

  17. Thermodynamics of cuticular transpiration Allen G. Gibbs *

    E-print Network

    Ahmad, Sajjad

    Accepted 6 May 2011 Keywords: Cuticle Humidity Thermodynamics Transpiration Water vapor A B S T R A CReview Thermodynamics of cuticular transpiration§ Allen G. Gibbs * School of Life Sciences, 4505 S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1066 2. Effects of temperature on cuticular transpiration

  18. Water, heat, and airborne pollutants effects on transpiration of urban trees.

    PubMed

    Wang, Hua; Ouyang, Zhiyun; Chen, Weiping; Wang, Xiaoke; Zheng, Hua; Ren, Yufen

    2011-01-01

    Transpiration rates of six urban tree species in Beijing evaluated by thermal dissipation method for one year were correlated to environmental variables in heat, water, and pollutant groups. To sort out colinearity of the explanatory variables, their individual and joint contributions to variance of tree transpiration were determined by the variation and hierarchical partitioning methods. Majority of the variance in transpiration rates was associated with joint effects of variables in heat and water groups and variance due to individual effects of explanatory group were in comparison small. Atmospheric pollutants exerted only minor effects on tree transpiration. Daily transpiration rate was most affected by air temperature, soil temperature, total radiation, vapor pressure deficit, and ozone. Relative humidity would replace soil temperature when factors influencing hourly transpiration rate was considered. PMID:21411197

  19. Green Roof Water Harvesting and Recycling Effects on Soil and Water Chemistry and Plant Physiology 

    E-print Network

    Laminack, Kirk Dickison

    2014-04-17

    on each green roof. Plant water potential, specific leaf area and rates of photosynthesis, transpiration, and conductivity were not significantly different between roofs which helped to further conclude that water quality parameters remained within...

  20. [Comparison of ecophysiological characteristics of seven plant species in semiarid loess hilly-gully region].

    PubMed

    Xu, Bing-cheng; Shan, Lun; Li, Feng-min

    2007-05-01

    The diurnal course of photosynthetic rate, transpiration rate, and leaf water potential (psi L) of five plant species in North Shaanxi loess hilly-gully region were measured in dry seasons. Based on the daily maximum photosynthetic and transpiration rates, daily total assimilation and transpiration, and diurnal change characteristics of psi L, the test plants were classified into different eco-adaptation types. Panicum virgatum L. had high photosynthetic rate, low transpiration rate and high water use efficiency (WUE), and its drought adaptation strategy was to delay dehydration by developing high psi L. Medicago sativa had high photosynthetic and transpiration rates but low WUE, while Lespedeza dahurica had low photosynthetic and transpiration rates and low WUE. Their drought adaptation strategies were the same, namely, by increasing psi L delay dehydration. Bothriochloa ischaemum had high photosynthetic rate, relative high transpiration rate and medium WUE, and its drought-resistant strategy was to decrease psi L to endure dehydration. Astragalus adsurgens had similar characteristics in diurnal courses of photosynthesis with B. ischaemum, and its drought adaption strategy was to delay dehydration by developing low psi psi L. PMID:17650846

  1. Effect ofEnvironmental Factors on Cuticular Transpiration Resistancet

    Microsoft Academic Search

    S. MORESHET

    Measurements ofthevarious diffusive resistances towater vaportransport withintheleavesof sunflower plants (Helianthus annuus)growinginacontrolled environment chamber,wereusedto calculate valuesofcuticular re- sistance undera rangeofenvironmental conditions. Cu- ticular resistance towaterlosswasfoundtobeinversely related totherelative humidity ofthesurrounding air, and itissuggested thatsuchamechanismwouldformauseful adaptation toaridconditions, enabling plants tomaintain amorefavorable internal waterbalance. Theflux ofwaterbytranspiration fromtheleaf totheatmos- phere takes place viathestomatal apertures andthrough the cuticle. Although theimportance ofenvironmental conditions in controlling stomatal transpiration

  2. Will intra-specific differences in transpiration efficiency in wheat be maintained in a high CO? world? A FACE study.

    PubMed

    Tausz-Posch, Sabine; Norton, Robert M; Seneweera, Saman; Fitzgerald, Glenn J; Tausz, Michael

    2013-06-01

    This study evaluates whether the target breeding trait of superior leaf level transpiration efficiency is still appropriate under increasing carbon dioxide levels of a future climate using a semi-arid cropping system as a model. Specifically, we investigated whether physiological traits governing leaf level transpiration efficiency, such as net assimilation rates (A(net)), stomatal conductance (g(s)) or stomatal sensitivity were affected differently between two Triticum aestivum L. cultivars differing in transpiration efficiency (cv. Drysdale, superior; cv. Hartog, low). Plants were grown under Free Air Carbon dioxide Enrichment (FACE, approximately 550?µmol?mol?¹ or ambient CO? concentrations (approximately 390?µmol?mol?¹). Mean A(net) (approximately 15% increase) and gs (approximately 25% decrease) were less affected by elevated [CO?] than previously found in FACE-grown wheat (approximately 25% increase and approximately 32% decrease, respectively), potentially reflecting growth in a dry-land cropping system. In contrast to previous FACE studies, analyses of the Ball et al. model revealed an elevated [CO?] effect on the slope of the linear regression by 12% indicating a decrease in stomatal sensitivity to the combination of [CO?], photosynthesis rate and humidity. Differences between cultivars indicated greater transpiration efficiency for Drysdale with growth under elevated [CO?] potentially increasing the response of this trait. This knowledge adds valuable information for crop germplasm improvement for future climates. PMID:23035842

  3. Coordination of Leaf Photosynthesis, Transpiration, and Structural Traits in Rice and Wild Relatives (Genus Oryza)1[W][OA

    PubMed Central

    Giuliani, Rita; Koteyeva, Nuria; Voznesenskaya, Elena; Evans, Marc A.; Cousins, Asaph B.; Edwards, Gerald E.

    2013-01-01

    The genus Oryza, which includes rice (Oryza sativa and Oryza glaberrima) and wild relatives, is a useful genus to study leaf properties in order to identify structural features that control CO2 access to chloroplasts, photosynthesis, water use efficiency, and drought tolerance. Traits, 26 structural and 17 functional, associated with photosynthesis and transpiration were quantified on 24 accessions (representatives of 17 species and eight genomes). Hypotheses of associations within, and between, structure, photosynthesis, and transpiration were tested. Two main clusters of positively interrelated leaf traits were identified: in the first cluster were structural features, leaf thickness (Thickleaf), mesophyll (M) cell surface area exposed to intercellular air space per unit of leaf surface area (Smes), and M cell size; a second group included functional traits, net photosynthetic rate, transpiration rate, M conductance to CO2 diffusion (gm), stomatal conductance to gas diffusion (gs), and the gm/gs ratio. While net photosynthetic rate was positively correlated with gm, neither was significantly linked with any individual structural traits. The results suggest that changes in gm depend on covariations of multiple leaf (Smes) and M cell (including cell wall thickness) structural traits. There was an inverse relationship between Thickleaf and transpiration rate and a significant positive association between Thickleaf and leaf transpiration efficiency. Interestingly, high gm together with high gm/gs and a low Smes/gm ratio (M resistance to CO2 diffusion per unit of cell surface area exposed to intercellular air space) appear to be ideal for supporting leaf photosynthesis while preserving water; in addition, thick M cell walls may be beneficial for plant drought tolerance. PMID:23669746

  4. TaER Expression Is Associated with Transpiration Efficiency Traits and Yield in Bread Wheat

    PubMed Central

    Zheng, Jiacheng; Yang, Zhiyuan; Madgwick, Pippa J.; Carmo-Silva, Elizabete; Parry, Martin A. J.; Hu, Yin-Gang

    2015-01-01

    ERECTA encodes a receptor-like kinase and is proposed as a candidate for determining transpiration efficiency of plants. Two genes homologous to ERECTA in Arabidopsis were identified on chromosomes 6 (TaER2) and 7 (TaER1) of bread wheat (Triticum aestivum L.), with copies of each gene on the A, B and D genomes of wheat. Similar expression patterns were observed for TaER1 and TaER2 with relatively higher expression of TaER1 in flag leaves of wheat at heading (Z55) and grain-filling (Z73) stages. Significant variations were found in the expression levels of both TaER1 and TaER2 in the flag leaves at both growth stages among 48 diverse bread wheat varieties. Based on the expression of TaER1 and TaER2, the 48 wheat varieties could be classified into three groups having high (5 varieties), medium (27 varieties) and low (16 varieties) levels of TaER expression. Significant differences were also observed between the three groups varying for TaER expression for several transpiration efficiency (TE)- related traits, including stomatal density (SD), transpiration rate, photosynthetic rate (A), instant water use efficiency (WUEi) and carbon isotope discrimination (CID), and yield traits of biomass production plant-1 (BYPP) and grain yield plant-1 (GYPP). Correlation analysis revealed that the expression of TaER1 and TaER2 at the two growth stages was significantly and negatively associated with SD (P<0.01), transpiration rate (P<0.05) and CID (P<0.01), while significantly and positively correlated with flag leaf area (FLA, P<0.01), A (P<0.05), WUEi (P<0.05), BYPP (P<0.01) and GYPP (P<0.01), with stronger correlations for TaER1 than TaER2 and at grain-filling stage than at heading stage. These combined results suggested that TaER involved in development of transpiration efficiency -related traits and yield in bread wheat, implying a function for TaER in regulating leaf development of bread wheat and contributing to expression of these traits. Moreover, the results indicate that TaER could be exploitable for manipulating important agronomical traits in wheat improvement. PMID:26047019

  5. Spatial patterns of simulated transpiration response to climate variability in a snow dominated mountain ecosystem

    USGS Publications Warehouse

    Christensen, L.; Tague, C.L.; Baron, J.S.

    2008-01-01

    Transpiration is an important component of soil water storage and stream-flow and is linked with ecosystem productivity, species distribution, and ecosystem health. In mountain environments, complex topography creates heterogeneity in key controls on transpiration as well as logistical challenges for collecting representative measurements. In these settings, ecosystem models can be used to account for variation in space and time of the dominant controls on transpiration and provide estimates of transpiration patterns and their sensitivity to climate variability and change. The Regional Hydro-Ecological Simulation System (RHESSys) model was used to assess elevational differences in sensitivity of transpiration rates to the spatiotemporal variability of climate variables across the Upper Merced River watershed, Yosemite Valley, California, USA. At the basin scale, predicted annual transpiration was lowest in driest and wettest years, and greatest in moderate precipitation years (R2 = 0.32 and 0.29, based on polynomial regression of maximum snow depth and annual precipitation, respectively). At finer spatial scales, responsiveness of transpiration rates to climate differed along an elevational gradient. Low elevations (1200-1800 m) showed little interannual variation in transpiration due to topographically controlled high soil moistures along the river corridor. Annual conifer stand transpiration at intermediate elevations (1800-2150 m) responded more strongly to precipitation, resulting in a unimodal relationship between transpiration and precipitation where highest transpiration occurred during moderate precipitation levels, regardless of annual air temperatures. Higher elevations (2150-2600 m) maintained this trend, but air temperature sensitivities were greater. At these elevations, snowfall provides enough moisture for growth, and increased temperatures influenced transpiration. Transpiration at the highest elevations (2600-4000 m) showed strong sensitivity to air temperature, little sensitivity to precipitation. Model results suggest elevational differences in vegetation water use and sensitivity to climate were significant and will likely play a key role in controlling responses and vulnerability of Sierra Nevada ecosystems to climate change. Copyright ?? 2008 John Wiley & Sons, Ltd.

  6. PILOT-PLANT STUDIES OF SLOW-RATE FILTRATION

    EPA Science Inventory

    Alternatives to conventional coagulation water filtration plants (those that utilize coagulation, flocculation, sedimentation and filtration) may be appropriate for some small water utilities. One such alternative is slow rate filtration. This paper describes pilot plant studies ...

  7. Leaf energy balance and transpirational relationships of tulip poplar (Liriodendron tulipifera)

    Microsoft Academic Search

    R. K. McConathy; S. B. McLaughlin; D. E. Reichle; B. E. Dinger

    1976-01-01

    Relationships between several physiological parameters of in situ tulip poplar (Liriodendron tulipifera L.) foliage, and its surrounding forest environment were examined, with emphasis on the transpirational process. Objectives were to measure and compare stomatal relationships with environmental and plant morphological variables, determine and assess the relative importance of factors affecting transpiration and leaf energy balance of a mature tulip poplar,

  8. Simulation of diurnal transpiration and photosynthesis of a water stressed soybean crop

    Microsoft Academic Search

    Albert Olioso; Toby N. Carlson; Nadine Brisson

    1996-01-01

    The diurnal course of photosynthesis and transpiration of different plants can exhibit a dissymmetric behaviour between the morning and the afternoon, a photosynthetic midday depression and a transpiration ‘plateau’. A field experiment conducted in a meditenanean climate allows us to identify these features for a soybean crop undergoing water stress. The experimental data also show that, before and after the

  9. Role of transpiration suppression by evaporation of intercepted water in improving irrigation efficiency

    Microsoft Academic Search

    J. A. Tolk; T. A. Howell; J. L. Steiner; D. R. Krieg; A. D. Schneider

    1995-01-01

    Sprinkler irrigation efficiency declines when applied water intercepted by the crop foliage, or gross interception (Igross), as well as airborne droplets and ponded water at the soil surface evaporate before use by the crop. However, evaporation of applied water can also supply some of the atmospheric demands usually met by plant transpiration. Any suppression of crop transpiration from the irrigated

  10. Use of high-resolution thermal infrared remote sensing and “three-temperature model” for transpiration monitoring in arid inland river catchment

    NASA Astrophysics Data System (ADS)

    Tian, Fei; Qiu, GuoYu; Lü, YiHe; Yang, YongHui; Xiong, Yujiu

    2014-07-01

    Based on high-resolution thermal infrared remote sensing and the three-temperature model (3T model), we developed a new algorithm for mapping transpiration. The necessary input parameters were surface temperature, air temperature, and solar radiation only. Therefore, in comparison with conventional methods, it is a simple and potentially valuable way to employ the thermal infrared remote sensing application. By using the proposed method, transpiration of sixteen types of typical vegetation in the upper and middle reaches of the Heihe River Basin in Northwestern China were calculated pixel by pixel. We evaluated modeled evapotranspiration with an eddy covariance (EC) result from the established regression equation, and a scatter correlation plot for the measured and estimated transpiration indicated that the model estimate is within acceptable limits, with a correlation coefficient of R2 = 0.796. Compared with the desert-oasis transitional zone, the maximum transpiration rate at the Gobi Desert presented a little earlier but was smaller. This great difference may imply that different types of plants have different water-use abilities and drought tolerances. Thus, the transpiration estimation with the 3T model, using high-resolution thermal infrared remote sensing data, can provide not only a bridge between large-scale and point observation with a measure of m2 from the infrared thermal imager, but also provide decision support for operational water management issues.

  11. CCMR: Modeling Transpiration with Porous Silicon Membranes

    NSDL National Science Digital Library

    Jilo, Allen

    2010-08-15

    The purpose of the project was to better understand the characteristics of porous silicon membranes and assess their possible applications, especially in the area of heat transfer. Porous silicon can be used in the modeling of transpiration in plants, where water is transported under negative pressure. If porous silicon is found to be able to hold high enough levels of tension (negative pressure), then it has great potential in cooling systems; it could act as a “self-driving pump” that would not need large amounts of external energy like most current systems.

  12. Nitrogen regulation of transpiration controls mass-flow acquisition of nutrients.

    PubMed

    Matimati, Ignatious; Verboom, G Anthony; Cramer, Michael D

    2014-01-01

    Transpiration may enhance mass-flow of nutrients to roots, especially in low-nutrient soils or where the root system is not extensively developed. Previous work suggested that nitrogen (N) may regulate mass-flow of nutrients. Experiments were conducted to determine whether N regulates water fluxes, and whether this regulation has a functional role in controlling the mass-flow of nutrients to roots. Phaseolus vulgaris were grown in troughs designed to create an N availability gradient by restricting roots from intercepting a slow-release N source, which was placed at one of six distances behind a 25 ?m mesh from which nutrients could move by diffusion or mass-flow (termed 'mass-flow' treatment). Control plants had the N source supplied directly to their root zone so that N was available through interception, mass-flow, and diffusion (termed 'interception' treatment). 'Mass-flow' plants closest to the N source exhibited 2.9-fold higher transpiration (E), 2.6-fold higher stomatal conductance (gs), 1.2-fold higher intercellular [CO2] (Ci), and 3.4-fold lower water use efficiency than 'interception' plants, despite comparable values of photosynthetic rate (A). E, gs, and Ci first increased and then decreased with increasing distance from the N source to values even lower than those of 'interception' plants. 'Mass-flow' plants accumulated phosphorus and potassium, and had maximum concentrations at 10mm from the N source. Overall, N availability regulated transpiration-driven mass-flow of nutrients from substrate zones that were inaccessible to roots. Thus when water is available, mass-flow may partially substitute for root density in providing access to nutrients without incurring the costs of root extension, although the efficacy of mass-flow also depends on soil nutrient retention and hydraulic properties. PMID:24231035

  13. Stomatal control of transpiration: Examination of the Jarvis-type representation of canopy resistance in relation to humidity

    NASA Astrophysics Data System (ADS)

    Lhomme, J.-P.

    2001-03-01

    The Jarvis-type parameterization of canopy resistance is commonly used to model the canopy energy balance in large-scale applications. In its most complete form it is written as a minimal stomatal resistance multiplied by five stress functions involving solar radiation F1(S), air temperature F2(T), air saturation deficit F3(D), soil or plant water status F4(?), and CO2 concentration of the air F5(C), respectively. One or several functions, however, can be missing according to the experimental conditions or the assumptions made for the modeling process. This general scheme is examined in relation to environmental humidity to determine the exact correspondence between the mathematical representation and the physiological response in terms of canopy resistance and actual transpiration. The strict feedback response, i.e., the response to air or soil humidity through plant water status, is simulated by means of the sole function F4 involving leaf water potential ?l (without the need for another stress function related to environmental humidity). In this case, canopy resistance increases with increased saturation deficit, and transpiration also increases. When soil water potential decreases, canopy resistance increases and transpiration falls. A feedforward response to air humidity, i.e., a direct response of stomata independent of plant water status, is modeled through the stress function F3(D), with or without the function F4(?l), depending on whether the feedforward response is combined with or without a feedback effect. In this latter case, canopy resistance increases with an increased saturation deficit, while the transpiration rate increases up to a threshold and then falls. A strict feedforward response to soil moisture is modeled through function F4 in which soil water potential replaces leaf water potential. When the canopy resistance formulation includes a feedback response, i.e., when the function F4(?) is used with leaf water potential ?l, Jarvis' scheme is equivalent to the parameterization developed by Monteith (as a function of the rate of transpiration), and the transpiration rate can be rewritten as a simple function of the climatic demand, the soil water availability, and the decoupling factor ?.

  14. Temporal variations of the 18O/16O signal of the whole-canopy transpiration in a temperate forest

    NASA Astrophysics Data System (ADS)

    Lee, Xuhui; Kim, Kyounghee; Smith, Ronald

    2007-09-01

    Biosphere-atmosphere exchange of water vapor isotopes plays an important role in the global atmospheric 18O-CO2 and 18O-O2 budgets. In this paper, we report the results of the first continuous measurements of isotope ratios of water vapor and the evapotranspiration flux in a temperate forest over one full growing season. We found that the 18O/16O isotopic signal of the whole-canopy transpiration (?T) was not in steady state with respect to plant source water. The departure from steady state was greatest at night and on days of low transpiration rates. Relative humidity was an important driver on timescales shorter than a few hours; on the diurnal timescale, the nonsteady state behavior was driven by relative humidity and the covarying transpiration rate. On average, ?T was lowest in midmorning and highest at midnight, with an average peak-to-peak variation on the order of 15‰ over the growing season. A diurnal variation of 60‰ or more was observed on some days. On the seasonal timescale, ?T was tightly coupled with the precipitation isotope ratio in the early growing season and fluctuated around the isotope ratio of the stem water of overstory trees in the late growing season. The temporal shift suggests that the forest switched its water source from the shallow to the deep soil pool and that the overstory trees dominated the whole stand transpiration in the late growing season. Using isotopic partitioning, we estimated that the overstory trees contributed roughly 70% to the whole-stand transpiration water loss during the growing season.

  15. A hierarchical analysis of the interactive effects of elevated CO2 and water availability on the nitrogen and transpiration productivities of velvet mesquite seedlings.

    PubMed

    Peterson, Andrew G; Neofotis, Peter G

    2004-12-01

    In this study we apply new extensions of classical growth analysis to assess the interactive effects of elevated CO2 and differences in water availability on the leaf-nitrogen and transpiration productivities of velvet mesquite (Prosopis velutina Woot.) seedlings. The models relate transpiration productivity (biomass gained per mass of water transpired per day) and leaf-nitrogen productivity (biomass gain per unit leaf N per day) to whole-plant relative growth rate (RGR) and to each other, allowing a comprehensive hierarchical analysis of how physiological and morphological responses to the treatments interact with each other to affect plant growth. Elevated CO2 led to highly significant increases in N and transpiration productivities but reduced leaf N per unit leaf area and transpiration per unit leaf area, resulting in no net effect of CO2 on the RGR of seedlings. In contrast, higher water availability led to an increase in leaf-tissue thickness or density without affecting leaf N concentration, resulting in a higher leaf N per unit leaf area and consequently a higher assimilatory capacity per unit leaf area. The net effect was a marginal increase in seedling RGR. Perhaps most important from an ecological perspective was a 41% reduction in whole-plant water use due to elevated CO2. These results demonstrate that even in the absence of CO2 effects on integrative measures of plant growth such as RGR, highly significant effects may be observed at the physiological and morphological level that effectively cancel each other out. The quantitative framework presented here enables some of these tradeoffs to be identified and related directly to each other and to plant growth. PMID:15322897

  16. Partitioning evapotranspiration into evaporation and transpiration in a corn field

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evapotranspiration (ET) is a main component of the hydrology cycle. It consists of soil water evaporation (E) and plant transpiration (T). Accurate partitioning of ET into E and T is challenging. We measured soil water E using heat pulse sensors and a micro-Bowen ratio system, T using stem flow gaug...

  17. Transpiration during life cycle in controlled wheat growth

    NASA Technical Reports Server (NTRS)

    Volk, Tyler; Rummel, John D.

    1989-01-01

    A previously-developed model of wheat growth, designed for convenient incorporation into system-level models of advanced space life support systems is described. The model is applied to data from an experiment that grew wheat under controlled conditions and measured fresh biomass and cumulated transpiration as a function of time. The adequacy of modeling the transpiration as proportional to the inedible biomass, and an age factor which varies during the life cycle, are examined. Results indicate that during the main phase of vegetative growth in the first half of the life cycle, the rate of transpiration per unit mass of inedible biomass is more than double the rate during the phase of grain development and maturation during latter half of the life cycle.

  18. A global synthesis of plant extinction rates in urban areas.

    PubMed

    Hahs, Amy K; McDonnell, Mark J; McCarthy, Michael A; Vesk, Peter A; Corlett, Richard T; Norton, Briony A; Clemants, Steven E; Duncan, Richard P; Thompson, Ken; Schwartz, Mark W; Williams, Nicholas S G

    2009-11-01

    Plant extinctions from urban areas are a growing threat to biodiversity worldwide. To minimize this threat, it is critical to understand what factors are influencing plant extinction rates. We compiled plant extinction rate data for 22 cities around the world. Two-thirds of the variation in plant extinction rates was explained by a combination of the city's historical development and the current proportion of native vegetation, with the former explaining the greatest variability. As a single variable, the amount of native vegetation remaining also influenced extinction rates, particularly in cities > 200 years old. Our study demonstrates that the legacies of landscape transformations by agrarian and urban development last for hundreds of years, and modern cities potentially carry a large extinction debt. This finding highlights the importance of preserving native vegetation in urban areas and the need for mitigation to minimize potential plant extinctions in the future. PMID:19723284

  19. Oxygen isotope signatures of transpired water vapor: the role of isotopic non-steady-state transpiration under natural conditions.

    PubMed

    Dubbert, Maren; Cuntz, Matthias; Piayda, Arndt; Werner, Christiane

    2014-09-01

    The oxygen isotope signature of water is a powerful tracer of water movement from plants to the global scale. However, little is known about the short-term variability of oxygen isotopes leaving the ecosystem via transpiration, as high-frequency measurements are lacking. A laser spectrometer was coupled to a gas-exchange chamber directly estimating branch-level fluxes in order to evaluate the short-term variability of the isotopic composition of transpiration (?E ) and to investigate the role of isotopic non-steady-state transpiration under natural conditions in cork-oak trees (Quercus suber) during distinct Mediterranean seasons. The measured ?(18) O of transpiration (?E ) deviated from isotopic steady state throughout most of the day even when leaf water at the evaporating sites was near isotopic steady state. High agreement was found between estimated and modeled ?E values assuming non-steady-state enrichment of leaf water. Isoforcing, that is, the influence of the transpirational ?(18) O flux on atmospheric values, deviated from steady-state calculations but daily means were similar between steady state and non-steady state. However, strong daytime isoforcing on the atmosphere implies that short-term variations in ?E are likely to have consequences for large-scale applications, for example, partitioning of ecosystem fluxes or satellite-based applications. PMID:24909361

  20. Measurement of sap flow in plant stems

    Microsoft Academic Search

    D. M. Smith; S. J. Allen

    1996-01-01

    Transpiration rates for whole plants, individual branches or tillers can be determined by techniques which measure the rate at which sap ascends stems. All of these methods use heat as a tracer for sap movement, but they are fundamentally different in their operating principles. Two methods commonly employed, the stem heat balance and trunk sector heat balance methods, use the

  1. Thermal Transpiration in Microsphere Membranes

    Microsoft Academic Search

    Marcus Young; Yen Lin Han; E. P. Muntz; G. Shiflett; Andrew Ketsdever; Amanda Green

    2003-01-01

    Self-assembled glass microsphere membranes as an alternative transpiration membrane for application in a Knudsen Compressor are discussed. A performance model is constructed and used to compare the performance of glass microsphere membranes to silicon aerogel membranes for this application. An initial experimental Knudsen Compressor stage based on glass microsphere membranes has been designed and experimentally tested. Preliminary performance results show

  2. Transpiration as landfill leachate phytotoxicity indicator.

    PubMed

    Bia?owiec, Andrzej

    2015-05-01

    An important aspect of constructed wetlands design for landfill leachate treatment is the assessment of landfill leachate phytotoxicity. Intravital methods of plants response observation are required both for lab scale toxicity testing and field examination of plants state. The study examined the toxic influence of two types of landfill leachate from landfill in Zakurzewo (L1) and landfill in Wola Paw?owska (L2) on five plant species: reed Phragmites australis (Cav.) Trin. ex Steud, manna grass Glyceria maxima (Hartm.) Holmb., bulrush Schoenoplectus lacustris (L.) Palla, sweet flag Acorus calamus L., and miscanthus Miscanthus floridulus (Labill) Warb. Transpiration measurement was used as indicator of plants response. The lowest effective concentration causing the toxic effect (LOEC) for each leachate type and plant species was estimated. Plants with the highest resistance to toxic factors found in landfill leachate were: sweet flag, bulrush, and reed. The LOEC values for these plants were, respectively, 17%, 16%, 9% in case of leachate L1 and 21%, 18%, 14% in case of L2. Leachate L1 was more toxic than L2 due to a higher pH value under similar ammonia nitrogen content, i.e. pH 8.74 vs. pH 8.00. PMID:25708408

  3. SK30 total energy plant rated at 73% efficiency

    SciTech Connect

    de Biasi, V. (ed.)

    1980-07-01

    The City of Hague in Holland is building a combined cycle plant. The plant will be powered by two Rolls-Royce SK30 gas turbine generators site rated at 25,000 kW each, two unfired Stork waste heat recovery boilers, and a Delaval Stork steam turbine rated at 26,000 kW. On its own, without district heating, the combined cycle plant is rated for 77,000 kW output at around 44% efficiency. Heat output of the combined cycle plant is used to provide thermal power for district heating. In the maximum output mode, there is some drop in electric power output (around 70,000 kW) but this is accompanied by 60,000 kW thermal power output for a net plant efficiency of close to 74% overall. (MCW)

  4. Comparison of photosynthesis, transpiration, and water use efficiency in two desert shrubs

    NASA Astrophysics Data System (ADS)

    Wei, Ruyi; Pan, Xiaoling

    2003-07-01

    Photosynthesis and transpiration are the most important physiological activities for plants. They are closely related not only to photosynthesis active radiation (PAR), air temperature (Ta), relative humility (RH) and ambient CO2 concentration, but also to plant stomatal conductance and intercellular CO2 concentration. Their relationship can be analyzed through statistic methods to indicate plant eco-physiological ability bearing to environment. By means of measuring the photosynthesis of Haloxylon ammodendron and Reaumuria soongorica in the Sangonghe River valley we have dealt with similarities and differences of two species. Results show that net photosynthesis rate of Reaumuria soongorica is slight higher than Haloxylon ammodendron, but water use efficiency of Haloxylon ammodendron is evidently higher than Reaumuria soongorica. It suggests that Haloxylon ammodendron has strong bearing ability to drought in natural habitat.

  5. Rate of Contamination Removal of Two Phyto-remediation Sites at the DOE Portsmouth Gaseous Diffusion Plant

    SciTech Connect

    Lewis, A.C.; Baird, D.R. [CDM Federal Services, P.O. Box 789, Piketon, OH 45661 (United States)

    2006-07-01

    This paper describes applications of phyto-remediation at the Portsmouth Gaseous Diffusion Plant (PORTS), a Department of Energy (DOE) Facility that enriched uranium from the early 1950's until 2000. Phyto-remediation has been implemented to assist in the removal of TCE (trichloroethylene) in the groundwater at two locations at the PORTS facility: the X-740 area and the X-749/X-120 area. Phyto-remediation technology is based on the ability of certain plants species (in this case hybrid poplar trees) and their associated rhizo-spheric microorganisms to remove, degrade, or contain chemical contaminants located in the soil, sediment, surface water, groundwater, and possibly even the atmosphere. Phyto-remediation technology is a promising clean-up solution for a wide variety of pollutants and sites. Mature trees, such as the hybrid poplar, can consume up to 3,000 gallons of groundwater per acre per day. Organic compounds are captured in the trees' root systems. These organic compounds are degraded by ultraviolet light as they are transpired along with the water vapor through the leaves of the trees. The phyto-remediation system at the X-740 area encompasses 766 one-year old hybrid poplar trees (Populus nigra x nigra, Populus nigra x maximowiczii, and Populus deltoides x nigra) that were planted 10 feet apart in rows 10 feet to 20 feet apart, over an area of 2.6 acres. The system was installed to manage the VOC contaminant plume. At the X749/X-120 area, a phyto-remediation system of 2,640 hybrid poplar trees (Populus nigra x maximowiczii) was planted in seven areas/zones to manage the VOC contaminant plume. The objectives of these systems are to remove contamination from the groundwater and to prevent further migration of contaminants. The goal of these remediation procedures is to achieve completely mature and functional phyto-remediation systems within two years of the initial planting of the hybrid poplar trees at each planting location. There is a direct relationship between plant transpiration, soil moisture, and groundwater flow in a phyto-remediation system. The existing monitoring program was expanded in 2004 in order to evaluate the interactions among these processes. The purpose of this monitoring program was to determine the rate of contaminant removal and to more accurately predict the amount of time needed to remediate the contaminated groundwater. Initial planting occurred in 1999 at the X-740 area, with additional replanting in 2001 and 2002. In 2003, coring of selected trees and chemical analyses illustrated the presence of TCE; however, little impact was observed in groundwater levels, analytical monitoring, and periodic tree diameter monitoring at the X-740 area. To provide better understanding of how these phyto-remediation systems work, a portable weather station was installed at the X-740 area to provide data for estimating transpiration and two different systems for measuring sap flow and sap velocity were outfitted to numerous trees. After evaluating and refining the groundwater flow and contaminant transport models, the data gathered by these two inventive methods can be used to establish a rate of contaminant removal and to better predict the time required in order to meet remediation goals for the phyto-remediation systems located at the PORTS site. (authors)

  6. Transpiration-induced changes in the photosynthetic capacity of leaves

    Microsoft Academic Search

    Thomas D. Sharkey

    1984-01-01

    High transpiration rates were found to affect the photosynthetic capacity of Xanthium strumarium L. leaves in a manner analagous to that of low soil water potential. The effect was also looked for and found in Gossypium hirsutum L., Agathis robusta (C. Moore ex Muell.) Bailey, Eucalyptus microcarpa Maiden, Larrea divaricata Cav., the wilty flacca tomato mutant (Lycopersicon esculentum (L.) Mill.)

  7. Sap flow in the stem of water stressed soybean and maize plants

    Microsoft Academic Search

    Y. Cohen; M. G. Huck; J. D. Hesketh; J. R. Frederick

    1990-01-01

    Water stress was imposed upon soybean [Glyxine max (L.) Merr. cv. Williams] and maize [Zea mays (L.) cv. Pioneer 3377] plants grown under controlled-environment conditions during a growing period of several irrigation cycles. Transpiration rates of individual plants were measured with a calibrated heat-pulse method and correlated to the rate of water loss obtained from successive weighings of the pots

  8. Changes in the photosynthetic characteristics of Plantago major plants caused by soil drought stress

    Microsoft Academic Search

    V. Mudrik; A. Kosobrukhov; I. Knyazeva; T. Pigulevskaya

    2003-01-01

    Changes in net photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentrations (Ci), transpiration rate (E) and water use efficiency (WUE) were measured in Plantago major L. plants grown under sufficient soil water supply or under soil water stress conditions. The plants had high PN in a wide range of soil water potential and temperature regimes. Soil water had little

  9. Relative Contribution of Nighttime Transpiration to Daily Total Water Use by Tamarix in a Desert Riparian Woodland

    Microsoft Academic Search

    G. W. Moore; K. Owens

    2005-01-01

    The phreatophytic plant, Tamarix, consumes water from the Pecos River in west Texas, forming a narrow band of dense riparian woodland in an otherwise sparsely vegetated desert environment. Narrow desert riparian zones are largely influenced by dry desert air, creating favorable conditions for nighttime transpiration. In this study, we explore whether nighttime transpiration, especially on nights with warm temperatures and

  10. Transpiration of urban trees and its cooling effect in a high latitude city

    NASA Astrophysics Data System (ADS)

    Konarska, Janina; Uddling, Johan; Holmer, Björn; Lutz, Martina; Lindberg, Fredrik; Pleijel, Håkan; Thorsson, Sofia

    2015-06-01

    An important ecosystem service provided by urban trees is the cooling effect caused by their transpiration. The aim of this study was to quantify the magnitude of daytime and night-time transpiration of common urban tree species in a high latitude city (Gothenburg, Sweden), to analyse the influence of weather conditions and surface permeability on the tree transpiration, and to find out whether tree transpiration contributed to daytime or nocturnal cooling. Stomatal conductance and leaf transpiration at day and night were measured on mature street and park trees of seven common tree species in Gothenburg: Tilia europaea, Quercus robur, Betula pendula, Acer platanoides, Aesculus hippocastanum, Fagus sylvatica and Prunus serrulata. Transpiration increased with vapour pressure deficit and photosynthetically active radiation. Midday rates of sunlit leaves ranged from less than 1 mmol m-2 s-1 (B. pendula) to over 3 mmol m-2 s-1 (Q. robur). Daytime stomatal conductance was positively related to the fraction of permeable surfaces within the vertically projected crown area. A simple estimate of available rainwater, comprising of precipitation sum and fractional surface permeability within the crown area, was found to explain 68 % of variation in midday stomatal conductance. Night-time transpiration was observed in all studied species and amounted to 7 and 20 % of midday transpiration of sunlit and shaded leaves, respectively. With an estimated night-time latent heat flux of 24 W m-2, tree transpiration significantly increased the cooling rate around and shortly after sunset, but not later in the night. Despite a strong midday latent heat flux of 206 W m-2, a cooling effect of tree transpiration was not observed during the day.

  11. Leaf Diffusion Resistance, Illuminance, and Transpiration 1

    PubMed Central

    Ehrler, W. L.; van Bavel, C. H. M.

    1968-01-01

    Stepwise increases in fluorescent illuminance, imposed as a single variable in a controlled environment, induced progressive stomatal opening in 8 plant species, as evidenced by a consistent decrease in leaf diffusion resistance (RL), ranging from 15 to 70 sec cm?1 in darkness to about 1 sec cm?1 at approximately 40 kilolux. The minimum RL values were the same for the upper and the lower epidermis, provided that stomatal density was adequate. Saturation illuminance was not achieved in any species; extrapolation indicates that 50 kilolux would bring about full stomatal opening (RL ? 0.1 sec cm?1). In 4 species, reasonable agreement was obtained in a controlled environment between transpiration as measured by weight loss and that calculated from determination of (a) the difference in water vapor density from leaf to air, (b) the boundary layer resistance, and (c) the leaf diffusion resistance. This result confirms the physical validity of the resistance measurement procedure. PMID:16656753

  12. Requirements for obtaining maximum indices of photosynthesis and transpiration in attached leaves of willow plants grown in short-rotation forest

    Microsoft Academic Search

    E. L. Kaipiainen; P. Pelkonen

    2007-01-01

    The results of multiyear studies of gas exchange in intact attached leaves of several willow species (Salix sp.) were analyzed. Measurements were performed with a portable Li-6400 infrared gas analyzer both on plants in their natural\\u000a environment and on rooted cuttings grown in a greenhouse. Individual attached leaves were placed into the leaf chamber where\\u000a climatic conditions were either similar

  13. Spatial Variability of Tree Transpiration Along a Soil Drainage Gradient of Boreal Black Spruce Forest

    NASA Astrophysics Data System (ADS)

    Angstmann, J. L.; Ewers, B. E.; Kwon, H.; Bond-Lamberty, B.; Amiro, B.; Gower, S. T.

    2008-12-01

    Boreal forests are an integral component in obtaining a predictive understanding of global climate change because they comprise 33% of the world's forests and store large amounts of carbon. Much of this carbon storage is a result of peat formation in cold, poorly-drained soils. Transpiration plays a crucial role in the interaction between carbon and water cycles due to stomatal control of these fluxes. The primary focus of this study is to quantify the spatial variability and drivers of tree transpiration in boreal forest stands across a well- to poorly-drained soil drainage gradient. Species composition of this region of boreal forest changes during succession in well-drained soils from being primarily dominated by Picea mariana with co-dominant Pinus banksiana and Populus tremuloides in younger stands to being dominated solely by Picea marianain older stands. Poorly-drained soils are dominated by Picea mariana and change little with succession. Previous work in well-drained stands showed that 1) tree transpiration changed substantially with stand age due to sapwood-to-leaf area ratio dynamics and 2) minimum leaf water potential (?) was kept constant to prevent excessive cavitation. We hypothesized that 1) minimum ? would be constant, 2) transpiration would be proportional to the sapwood-to-leaf area ratio across a soil drainage gradient, and 3) spatial relationships between trees would vary depending on stomatal responses to vapor pressure deficit (D). We tested these hypotheses by measuring ? of 33 trees and sap flux from 204 trees utilizing cyclic sampling constructed to study spatial relationships. Measurements were conducted at a 42-year-old stand representing maximum tree diversity during succession. There were no significant differences between growing season averaged ? in well- (-0.35 and -1.37 for pre-dawn and mid-day respectively) and poorly- drained soil conditions (-0.38 and -1.41 for pre-dawn and mid-day respectively) for Picea mariana. Water use results of Picea mariana differed between drainage conditions when expressed per unit xylem area with trees in poorly-drained soils experiencing higher rates than trees in well-drained areas (101.79 and 83.02 g cm-2 day-1 respectively). In contrast, when expressed as transpiration per tree, trees on well-drained soils had higher rates than those in poorly-drained locations (366.96 and 216.82 g tree-1 day-1 respectively). This indicates that tree size, reflected in sapwood area per ground area, which is constrained by anaerobic conditions across well- to poorly-drained areas, is driving differences in tree transpiration. Initial spatial analyses show that spatial autocorrelation decreases from 51.3 to 24.6 meters as D increases from 0.9 to 2.1 kPa. This phenomenon is explained by tree hydraulics and more patchy stomatal response as trees regulate water loss. Thus, regional scale bottom-up process models of boreal forest transpiration can be simplified with respect to soil drainage while retaining mechanistic rigor with respect to plant hydraulics.

  14. Transpiration of shrub species, Alnus firma under changing atmospheric environments in montane area, Japan

    NASA Astrophysics Data System (ADS)

    Miyazawa, Y.; Maruyama, A.; Inoue, A.

    2014-12-01

    In the large caldera of Mt. Aso in Japan, grasslands have been traditionally managed by the farmers. Due to changes in the social structure of the region, a large area of the grassland has been abandoned and was invaded by the shrubs with different hydrological and ecophysiological traits. Ecophysiological traits and their responses to seasonally changing environments are fundamental to project the transpiration rates under changing air and soil water environments, but less is understood. We measured the tree- and leaf-level ecophysiological traits of a shrub, Alnus firma in montane region where both rainfall and soil water content drastically changes seasonally. Sap flux reached the annual peak in evaporative summer (July-August) both in 2013 and 2014, although the duration was limited within a short period due to the prolonged rainy season before summer (2014) and rapid decrease in the air vapor pressure deficit (D) in late summer. Leaf ecophysiological traits in close relationship with gas exchange showed modest seasonal changes and the values were kept at relatively high levels typical in plants with nitrogen fixation under nutrient-poor environments. Stomatal conductance, which was measured at leaf-level measurements and sap flux measurements, showed responses to D, which coincided with the theoretical response for isohydric leaves. A multilayer model, which estimates stand-level transpiration by scaling up the leaf-level data, successfully captured the temporal trends in sap flux, suggesting that major processes were incorporated. Thus, ecophysiological traits of A. firma were characterized by the absence of responses to seasonally changing environments and the transpiration rate was the function of the interannually variable environmental conditions.

  15. Uncertainty in the response of transpiration to CO2 and implications for climate change

    NASA Astrophysics Data System (ADS)

    Mengis, Nadine; Keller, David; Eby, Michael; Oschlies, Andreas

    2015-04-01

    While terrestrial precipitation is a societally highly relevant climate variable, there is little consensus among climate models about its projected 21st century changes. The main source of precipitable water over land is plant transpiration. Plants control transpiration by opening and closing their stomata. The sensitivity of this process to increasing CO2 concentrations is uncertain. To assess the impact of this uncertainty on future climate, we perform experiments with an intermediate complexity Earth System Climate Model (UVic ESCM) for a range of model-imposed transpiration-sensitivities to CO2. Changing the sensitivity of transpiration to CO2 causes simulated terrestrial precipitation to change by -10 % to +27 % by 2100 under a high emission scenario. This study emphasises the importance of an improved assessment of the dynamics of environmental impact on vegetation to better predict future changes of the terrestrial hydrological and carbon cycle.

  16. Decreased transpiration in poplar trees exposed to 2,4,6-trinitrotoluene

    SciTech Connect

    Thompson, P.L. [Seattle Univ., WA (United States). Dept. of Civil and Environmental Engineering; Ramer, L.A.; Guffey, A.P.; Schnoor, J.L. [Univ. of Iowa, Iowa City, IA (United States). Dept. of Civil and Environmental Engineering

    1998-01-01

    The improper handling of the toxic compound 2,4,6-trinitrotoluene (TNT) has led to the contamination of soil and groundwater, and the uptake of TNT by a variety of plants has been established. This article discusses the effects of various concentrations of the explosive 2,4,6-trinitrotoluene (TNT) on the transpiration of hybrid poplar trees growing in hydroponic media. Transpiration was measured daily by gravimetric means. The rapid removal of TNT from hydroponic solutions was a result of plant uptake and required a daily dosage of TNT to ensure a relatively constant exposure over time. Transpiration decreased with increasing TNT concentrations {ge}5 mg/L. Decreases in transpiration were accompanied by leaf chlorosis and abscission. A comparison between a laboratory study and a pilot-scale experiment showed good scale-up potential.

  17. Reduced atmospheric pressure in Radish: Alteration of NCER and transpiration at decreased oxygen partial pressures

    NASA Astrophysics Data System (ADS)

    Wehkamp, Cara Ann; Stasiak, Michael; Wheeler, Raymond; Dixon, Mike

    Fundamental to the future of space exploration is the development of advanced life support systems capable of maintaining crews for significant periods without re-supply from Earth. Significant research is focused on the development of bioregenerative life support systems to be used in conjunction with the current physico-chemical methods. These bioregenerative life support systems harness natural ecosystem processes and employ plant photosynthesis and transpiration to produce food, oxygen and regenerate water while consuming carbon dioxide. The forthcoming exploration of the Moon and Mars has prompted interest into the effects of hypobaria on plant development. Reduced atmospheric pressures will lessen the pressure gradient between the structure and the local environment thereby decreasing gas leakage and possibly the structural mass of the plant growth facility. In order to establish the optimal specifications for reduced pressure plant growth structures it is essential to determine the atmospheric pressure limits required for conventional plant development and growth. Due to its physiological importance, oxygen will compose a significant portion of these minimal environments. The objective of this study was to test the hypothesis that reduced atmospheric pressure and decreased oxygen partial pressures had no effect on radish productivity. Radishes (Raphanus sativa L. cv. Cherry Bomb II) were grown from seed in the University of Guelph's Hypobaric Plant Growth Chambers for a period of 21 days. Treatments included total pressures of 10, 33, 66 and 96 kPa and oxygen partial pressures of 2, 7, 14 and 20 kPa. Experiments demonstrated that reduced partial pressures of oxygen had a greater effect on radish growth than hypobaria. Results showed a reduction in net carbon exchange rate and transpiration with decreasing oxygen partial pressures leading to diminished productivity. Keywords: hypobaric, radish, oxygen partial pressure, variable pressure chamber, bioregenerative life support

  18. Effect of plants on sunspace passive solar heating

    SciTech Connect

    Best, E.D.; McFarland, R.D.

    1985-01-01

    The effect of plants on sunspace thermal performance is investigated, based on experiments done in Los Alamos using two test rooms with attached sunspaces, which were essentially identical except for the presence of plants in one. Performance is related to plant transpiration, evaporation from the soil, condensation on the glazing and the absorbtance of solar energy by the lightweight leaves. Performance effects have been quantified by measurements of auxiliary heat consumption in the test rooms and analyzed by means of energy balance calculations. A method for estimating the transpiration rate is presented.

  19. Transpiration in an oil palm landscape: effects of palm age

    NASA Astrophysics Data System (ADS)

    Röll, A.; Niu, F.; Meijide, A.; Hardanto, A.; Hendrayanto; Knohl, A.; Hölscher, D.

    2015-06-01

    Oil palm (Elaeis guineensis Jacq.) plantations cover large and continuously increasing areas of humid tropical lowlands. Landscapes dominated by oil palms usually consist of a mosaic of mono-cultural, homogeneous stands of varying age, which may be heterogeneous in their water use characteristics. However, studies on the water use characteristics of oil palms are still at an early stage and there is a lack of knowledge on how oil palm expansion will affect the major components of the hydrological cycle. To provide first insights into hydrological landscape-level consequences of oil palm cultivation, we derived transpiration rates of oil palms in stands of varying age, estimated the contribution of palm transpiration to evapotranspiration, and analyzed the influence of fluctuations in environmental variables on oil palm water use. We studied 15 two- to 25 year old stands in the lowlands of Jambi, Indonesia. A sap flux technique with an oil palm specific calibration and sampling scheme was used to derive leaf-, palm- and stand-level water use rates in all stands under comparable environmental conditions. Additionally, in a two- and a 12 year old stand, eddy covariance measurements were conducted to derive evapotranspiration rates. Water use rates per leaf and palm increased 5-fold from an age of two years to a stand age of approx. 10 years and then remained relatively constant. A similar trend was visible, but less pronounced, for estimated stand transpiration rates of oil palms; they varied 12-fold, from 0.2 mm day-1 in a 2 year old to 2.5 mm day-1 in a 12 year old stand, showing particularly high variability in transpiration rates among medium-aged stands. Confronting sap flux and eddy-covariance derived water fluxes suggests that transpiration contributed 8 % to evapotranspiration in the 2 year old stand and 53 % in the 12 year old stand, indicating variable and substantial additional sources of evaporation, e.g. from the soil, the ground vegetation and from trunk epiphytes. Diurnally, oil palm transpiration rates were characterized by an early peak between 10 and 11 a.m.; there was a pronounced hysteresis in the leaf water use response to changes in vapor pressure deficit for all palms of advanced age. On the day-to-day basis this resulted in a relatively low variability of oil palm water use regardless of fluctuations in vapor pressure deficit and radiation. We conclude, that oil palm dominated landscapes show some spatial variations in (evapo)transpiration rates, e.g. due to varying age-structures, but that the temporal variability of oil palm transpiration is rather low. Stand transpiration rates of some studied oil palm stands compared to or even exceed values reported for different tropical forests, indicating a high water use of oil palms under certain site or management conditions. Our study provides first insights into the eco-hydrological characteristics of oil palms as well as a first estimate of oil palm water use across a gradient of plantation age. It sheds first light on some of the hydrological consequences of the continuing expansion of oil palm plantations.

  20. Regional variation in canopy transpiration of Central European beech forests.

    PubMed

    Schipka, Florian; Heimann, Jutta; Leuschner, Christoph

    2005-03-01

    Forest hydrologists have hypothesised that canopy transpiration (E(c)) of European temperate forests occurs at rather similar rates in stands with different tree species and hydrologic regimes. We tested this hypothesis by synchronously measuring xylem sap flow in four mature stands of Fagus sylvatica along a precipitation gradient with the aim (1) of exploring the regional variability of annual canopy transpiration (E(c(t))) in this species, and (2) of analysing the relationship between precipitation (P) and E(c(t)). E(c(t)) rates of 216, 225, 272 and 303 mm year(-1) corresponded to precipitation averages of 520, 710, 801 and 1,040 mm year(-1) in the four stands. We explored the regional variability of E(c(t)) in Central European colline to sub-montane beech stands in two meta-analyses based on (1) existing sap flow data on beech (n=5 observations), or (2) all canopy transpiration data on beech obtained by different techniques (sap flow, micrometeorological or soil water budget approaches, n=25). With a coefficient of variation (CV) of 20%, the regional variability of E(c(t)) (213-421 mm year(-1)) was smaller than the variation in corresponding precipitation (550-1,480 mm year(-1)). The mean E(c(t)) for beech was 289 (+/-58) mm year(-1) (n=25). A humped-shaped relationship between E(c(t)) and P, with a broad transpiration maximum in the precipitation range from ca. 700 to 1,000 mm year(-1), was found which may indicate soil moisture limitation of transpiration for P transpiration by increased cloudiness or leaf wetness for P>1,000 mm year(-1). Thus, the precipitation level significantly influences canopy transpiration of humid temperate forests; however, the size of the P influence on E(c(t)) and, in part, the direction of its effect differ from forests in semi-arid or arid climates. European beech has the capacity to maintain high E(c) rates in both humid and partly dry summer climates (P<550 mm year(-1)). PMID:15682345

  1. The upscaling of transpiration from individual trees to areal transpiration in tree belts

    Microsoft Academic Search

    Russell S. Crosbie; Brett Wilson; Justin D. Hughes; Christopher McCulloch

    2007-01-01

    Sap flow measurements have long been used to measure transpiration in individual trees and there exist some well established\\u000a methods for upscaling individual tree volumetric transpiration to areal transpiration in plantation and forest plots. However,\\u000a where edge effects are significant, such as in tree belts, the area the volumetric transpiration is to be projected upon is\\u000a unknown. This paper provides

  2. Effect, uptake and disposition of nitrobenzene in several terrestrial plants

    Microsoft Academic Search

    C. McFarlane; T. Pfleeger; J. Fletcher

    1990-01-01

    Eight species of plants were exposed to nitrobenzene in a hydroponic solution. Four species experienced no depression of either transpiration or photosynthetic rates, while one was rapidly killed and the other three were temporarily affected but recovered from the treatment. Uptake of nitrobenzene was passive and was shown to be proportional to the rate of water flux in each species.

  3. Effects of anti-transpirants on transpiration and energy use in greenhouse cultivation

    Microsoft Academic Search

    L. F. M. Marcelis; F. L. K. Kempkes; C. Stanghellini; C. Grashoff

    2008-01-01

    Greenhouse production in North-West Europe consumes a lot of energy. The energy is needed for heating the greenhouse and controlling air humidity. Transpiration of a crop increases the energy use. The aim of this study was to explore the possibilities for the application of anti-transpirants to save energy by reducing crop transpiration without reducing crop yield. Literature and model calculations

  4. Material Response of One-Dimensional, Steady-State Transpiration Cooling in Radiative and Convective Environments

    NASA Technical Reports Server (NTRS)

    Kubota, Hirotoshi

    1975-01-01

    A simplified analytical solution for thermal response of a transpiration-cooled porous heat-shield material in an intense radiative-convective heating environment is presented. Essential features of this approach are "two-flux method" for radiative transfer process and "two-temperature" assumption for solid and gas temperatures. Incident radiative-convective heatings are specified as boundary conditions. Sample results are shown using porous silica with CO2 transpiration and some parameters quantitatively show the effect on this transpiration cooling system. Summarized maps for mass injection rate, porosity and blowing correction factor for radiation are obtained in order to realize such a cooling system.

  5. Cultural Practices for Producing Dryland Malt Barley: Planting Rate

    E-print Network

    Lawrence, Rick L.

    Cultural Practices for Producing Dryland Malt Barley: Planting Rate Grant D. Jackson Western Triangle Ag Research Center, Conrad, MT Introduction Production of malting barley is expected to increase in non-traditional barley producing areas of north central Montana due to the expected increase

  6. [Photosynthesis and transpiration characteristics of female and male Trichosanthes kirilowii Maxim individuals].

    PubMed

    Liu, Yun; Zhong, Zhang-cheng; Wang, Xiao-xue; Xie, Jun; Yang, Wen-ying

    2011-03-01

    A field research was conducted on the photosynthesis and transpiration characteristics of dioecious Trichosanthes kirilowii individuals at four key development stages. At vegetative growth stage, the photosynthesis rate, transpiration rate, stomatal conductance, and water use efficiency of male individuals were higher than those of female individuals, and hence, male individuals entered into reproductive growth stage 22 days earlier than female individuals. After entering into reproductive growth stage, male individuals had higher photosynthesis rate, transpiration rate, and stomatal conductance, but slightly lower water use efficiency than female individuals. As the female individuals started to reproductive growth, their photosynthesis rate and water use efficiency were significantly lower, while the transpiration rate and stomatal conductance were higher than those of the male individuals. The effects of climate factors on the growth and development of T. kirilowii mainly occurred at its vegetative growth and early reproductive growth stages, and weakened at later reproductive growth stages. Higher temperature and lower relative humidity benefited the growth and development of T. kirilowii, and illumination could enhance the photosynthesis rate of T. kirilowii, especially its male individuals. After entering into reproductive growth stage, the photosynthesis rate of male individuals increased significantly with increasing illumination, but that of female individuals only had a slight increase, and the transpiration rate of male individuals as well as the photosynthesis rate of female individuals all increased significantly with increasing temperature. PMID:21657019

  7. Towards modeling hydrodynamic stress limitations on transpiration

    NASA Astrophysics Data System (ADS)

    Matheny, A. M.; Bohrer, G.; Ivanov, V. Y.; Stoy, P. C.

    2011-12-01

    Evapotranspiration is one of the major forcing functions of Earth's climate, providing the link for the soil-plant-water continuum. Current models for transpiration assume a coupling between stomatal conductance and soil moisture through empirical relationships that do not resolve the hydrodynamic process of water movement from the soil to the leaves. This approach does not take advantage of recent advances in our understanding of water flow and storage in the trees, or of tree and canopy structure. It has been suggested that stomata respond to water potential in the leaf and branch, and that this hydrodynamic response is a mechanism for hydraulic limitation of stomatal conductance. Hydraulic limitations in forest ecosystems are common and are known to control transpiration when the soil is drying or when vapor pressure deficit (VPD) is very large. Hydraulic limitation can also impact stomatal apertures under conditions of adequate soil moisture and lower evaporative demand. Hydrodynamic stresses at the tree level act at several time scales, including the fast, minute-hour scale. These dynamics are faster than the time scales of hours to days at which drying soil will affect stomata conductance. The lack of representation of the tree-hydrodynamic process should therefore lead to atypical intra-daily patterns of error in results of current models. We use a large-scale comparison between observations and land-surface models to characterize the patterns of intra-daily error in simulated water flux. Through the use of the North American Carbon Program (NACP) dataset, more than 10 years of water flux data for 35 Fluxnet sites in the US and Canada have been analyzed. The diurnal error for each of the 24 models represented in this dataset allows the models to be categorized and evaluated on their ability to accurately predict the fast temporal dynamics of transpiration in different ecosystems and atmospheric forcing. Among well calibrated models, two general error patterns prevail: (1) a daytime underestimation followed by nighttime overestimation of latent heat exchange; and (2) an underestimation during the morning and an afternoon overestimation. Although model error patterns are site specific, there are models that are more likely to favor one pattern above the other based on the model's sensitivity to VPD and soil moisture. The second error pattern occurs more frequently in sites where non-limiting soil moisture conditions exist. We hypothesize that the afternoon overestimation of transpiration in these scenarios can be explained by the models' lack of a mechanism to handle midday stomata closure due to hydrodynamic stresses. We introduce FETCH - a tree hydrodynamic model that can resolve the fast dynamics of stomatal conductance. We propose that coupling FETCH to other land-surface models would reduce intra-daily errors and improve the representation of canopy structure in atmospheric and hydrologic simulations.

  8. Mostly Plants. Individualized Biology Activities on: I. Investigating Bread Mold; II. Transpiration; III. Botany Project; IV. Collecting/Preserving/Identifying Leaves; [and] V. Student Science Laboratory Write-Ups.

    ERIC Educational Resources Information Center

    Gibson, Paul R.

    Individualized biology activities for secondary students are presented in this teaching guide. The guide is divided into five sections: (1) investigating bread mold; (2) investigating transpiration; (3) completing a botany project; (4) collecting, preserving, and identifying leaves; and (5) writing up science laboratory investigations. The…

  9. Transpiration Cooling Of Hypersonic Blunt Body

    NASA Technical Reports Server (NTRS)

    Henline, William D.

    1991-01-01

    Results on analytical approximation and numerical simulation compared. Report presents theoretical study of degree to which transpiration blocks heating of blunt, axisymmetric body by use of injected air. Transpiration cooling proposed to reduce operating temperatures on nose cones of proposed hypersonic aerospace vehicles. Analyses important in design of thermal protection for such vehicles.

  10. Transpiration from shoots triggers diurnal changes in root aquaporin expression.

    PubMed

    Sakurai-Ishikawa, Junko; Murai-Hatano, Mari; Hayashi, Hidehiro; Ahamed, Arifa; Fukushi, Keiko; Matsumoto, Tadashi; Kitagawa, Yoshichika

    2011-07-01

    Root hydraulic conductivity (Lp(r)) and aquaporin amounts change diurnally. Previously, these changes were considered to be spontaneously driven by a circadian rhythm. Here, we evaluated the new hypothesis that diurnal changes could be triggered and enhanced by transpirational demand from shoots. When rice plants were grown under a 12h light/12h dark regime, Lp(r) was low in the dark and high in the light period. Root aquaporin mRNA levels also changed diurnally, but the amplitudes differed among aquaporin isoforms. Aquaporins, such as OsPIP2;1, showed moderate changes, whereas root-specific aquaporins, such as OsPIP2;5, showed temporal and dramatic induction around 2h after light initiation. When darkness was extended for 12h after the usual dark period, no such induction was observed. Furthermore, plants under 100% relative humidity (RH) showed no induction even in the presence of light. These results suggest that transpirational demand triggers a dramatic increase in gene expressions such as OsPIP2;5. Immunocytochemistry showed that OsPIP2;5 accumulated on the proximal end of the endodermis and of the cell surface around xylem. The strong induction by transpirational demand and the polar localization suggest that OsPIP2;5 contributes to fine adjustment of radial water transport in roots to sustain high Lp(r) during the day. PMID:21414014

  11. Stomatal control of transpiration: Examination of Monteith's Formulation of canopy resistance

    Microsoft Academic Search

    J.-P. Lhomme; E. Elguero; A. Chehbouni; G. Boulet

    1998-01-01

    The stomatal response to air humidity has been recently reinterpreted in the sense that stomata seem to respond to the rate of transpiration rather to air humidity per se. Monteith suggested that the relation between canopy stomatal resistance rs and canopy transpiration E can be written as rs\\/rsn=1\\/(1 ? E\\/Ex), where rsn is a notional minimum canopy resistance, obtained by

  12. Stomatal control of transpiration: Examination of Monteith's formulation of canopy resistance

    Microsoft Academic Search

    J.-P. Lhomme; E. Elguero; A. Chehbouni; G. Boulet

    1998-01-01

    The stomatal response to air humidity has been recently reinterpreted in the sense that stomata seem to respond to the rate of transpiration rather to air humidity per se. Monteith suggested that the relation between canopy stomatal resistance rs and canopy transpiration E can be written as rs\\/rsn=1\\/(1-E\\/Ex), where rsn is a notional minimum canopy resistance, obtained by extrapolation to

  13. Effects of Typha latifolia transpiration and harvesting on nitrate concentrations in surface water of wetland microcosms

    Microsoft Academic Search

    Jay Martin; Elizabeth Hofherr; Martin F. Quigley

    2003-01-01

    Abtract  This experiment tested the hypothesis that the movement of water into the soil due to macrophyte transpiration stimulates\\u000a nitrate removal from wetlands. The short-term impacts of biomass harvesting upon the ability of wetlands to reduce nitrate\\u000a concentrations were also investigated. Different amounts of biomass were harvested fromTypha latifolia specimens to create three treatments of varying transpiration rates. Harvesting and the

  14. HYDROLOGICAL IMPACTS OF WOODY PLANT ENCROACHMENT IN ARID AND SEMIARID GRASSLANDS

    EPA Science Inventory

    Woody plants may be able to access deeper groundwater for year-round transpiration and thus consume more water than grasses, affecting recharge, soil moisture and runoff. Amount of water available to plants from precipitation is determined in part by nfiltration rates into...

  15. Transpiration Regulation of silver firs during and after severe droughts in relation to soil properties

    NASA Astrophysics Data System (ADS)

    Chanzy, A.; Nourtier, M.

    2011-12-01

    Silver fir is declining and dying in the Mediterranean area, at its southern margin where climate is expected to become warmer and drier. At regional scale, silver fir death seems to be located on dry areas while it depends on soil water availability at forest stand scale. To understand silver firs vulnerability to drought, factors involved in their transpiration regulation were studied. An experiment was carried out on Mont Ventoux (in Provence region in south of France) which is a karstic area. Soil properties were characterised by electric resistivity tomography for estimating soil water storage capacity through the determination of soil depth and stones content. Transpiration, predawn leaf water potential dynamic and crown surface temperature were measured on trees during three years. Vulnerability curves to embolism of coarse roots and branches were established. Finally, tree growth rate history was analysed using tree ring width analysis. The experiment covered three very different climatic years. 2008 was a wet year, whereas a severe drought occurred in summer 2009 and in less extent in 2010. Soils were well watered during winters thanks to exceptional snow falls. In the context of the experiment, silver firs strongly regulate their transpiration. Transpiration/potential transpiration ratio is mostly far below 1. The decrease in transpiration rate during drying periods were the quickest on soil having small and large water storage capacity whereas on the intermediate cases, the decrease was more gradual. Moreover, the water stress intensity, derived from predawn leaf water potential, was the largest on soil having large water storage capacity. After the 2009 severe drought, transpiration rate remains much low after fall rainfalls. The transpiration drop persisted after the winter while soils were well watered. Sap flow radial distributions have suggested that the deeps roots were not reactivated after the drought. Tring ring width analysis showed that the impact of a severe drought as that of 1976 may impact the tree physiology over very long periods (>10 years). The aboveground/belowground development during the juvenile period appeared as a key to understand the tree regulation to water stress. Long term regulation mechanisms based on carbon availability allocation should be accounted for to represent the transpiration regulation. Our observations have shown that transpiration modelling schemes, based on energy balance and stomatal regulation only, are not appropriate to represent silver transpiration rate during and after drought. Some additional regulation processes have been proposed.

  16. A simple general method to evaluate intra-specific transpiration parameters within and among seedling families

    Microsoft Academic Search

    Stefano Leonardi; Paolo Piovani; Federico Magnani; Paolo Menozzi

    2006-01-01

    A method to evaluate the genetic control of plant response to increasing soil water deficit is proposed. A description of single tree transpiration behavior was obtained considering parameters independent from air and soil conditions. We removed environmental effects by using two approaches: the normalization of drought data to control (watered) plants and the fitting of a process model. We analyzed

  17. Carbon dioxide enrichment and temperature effects on cotton canopy photosynthesis, transpiration, and water-use efficiency

    Microsoft Academic Search

    V. R. Reddy; K. R. Reddy; H. F. Hodges

    1995-01-01

    The objectives of this study were to evaluate effects of ambient and double ambient [CO2] at a range of growing temperatures on photosynthesis, respiration, transpiration, water-use efficiency and dry matter accumulation of cotton plants (Gossypium hirsutum L., cv. DPL 50). In Experiment I, plants were grown outdoors until first bloom, then transferred into naturally lit growth chambers and grown for

  18. The Inappropriate Use of Crop Transpiration Coefficients (Kc) to Estimate Evapotranspiration in Arid Ecosystems: A Review

    Microsoft Academic Search

    Ricardo Mata-González; Terry McLendon; David W. Martin

    2005-01-01

    The transpiration coefficient (Kc) method estimates evapotranspiration as a proportion of the evapotranspiration of a reference crop growing in ideal conditions. This approach was designed for irrigated crops and assumes that plants are not subjected to resource limitations. Other assumptions are that plants have high leaf area index and little stomatal resistance to water loss. These conditions are not common

  19. Nitric acid loss rates measured in power plant plumes

    Microsoft Academic Search

    J. A. Neuman; D. D. Parrish; T. B. Ryerson; C. A. Brock; C. Wiedinmyer; G. J. Frost; J. S. Holloway; F. C. Fehsenfeld

    2004-01-01

    Measurements of HNO3, NOx, NOy, and CO2 in the plumes from electric utility power plants located in eastern Texas are used to determine the HNO3 loss rates in the planetary boundary layer during plume transport. These 1 Hz measurements were obtained from the National Center for Atmospheric Research Electra aircraft flying on clear afternoons in a well-mixed planetary boundary layer

  20. Triadimefon enhances growth and net photosynthetic rate in NaCl stressed plants of Raphanus sativus L

    Microsoft Academic Search

    R. Panneerselvam; M. Muthukumarasamy; L. Karikalan

    1997-01-01

    The effect of sodium chloride and triadimefon (TDM) on the chlorophyll (Chl) content, net photosynthetic rates (PN), rate of transpiration (E), and intercellular CO2 concentration (Ci) in Raphanus sativus was studied. The effect of NaCl salinity was partially ameliorated by TDM which caused increase in Chl\\u000a content, PN, and Ci. TDM also increased root dry matter production, decreased E, and

  1. Transpirational demand affects aquaporin expression in poplar roots.

    PubMed

    Laur, Joan; Hacke, Uwe G

    2013-05-01

    Isohydric plants tend to maintain a water potential homeostasis primarily by controlling water loss via stomatal conductance. However, there is accumulating evidence that plants can also modulate water uptake in a dynamic manner. The dynamics of water uptake are influenced by aquaporin-mediated changes in root hydraulics. Most studies in this area have been conducted on herbaceous plants, and less is known about responses of woody plants. Here a study was conducted to determine how roots of hybrid poplar plants (Populus trichocarpa×deltoides) respond to a step change in transpirational demand. The main objective was to measure the expression of selected aquaporin genes and to assess how transcriptional responses correspond to changes in root water flow (Q R) and other parameters of water relations. A subset of plants was grown in shade and was subsequently exposed to a 5-fold increase in light level. Another group of plants was grown at ~95% relative humidity (RH) and was then subjected to lower RH while the light level remained unchanged. Both plant groups experienced a transient drop in stem water potentials. At 28h after the increase in transpirational demand, water potentials recovered. This recovery was associated with changes in the expression of PIP1 and PIP2 subfamily genes and an increase in Q R. Stomata of plants growing at high RH were larger and showed incomplete closure after application of abscisic acid. Since stomatal conductance remained high and unchanged in these plants, it is suggested that the recovery in water potential in these plants was largely driven by the increase in Q R. PMID:23599275

  2. Transpirational demand affects aquaporin expression in poplar roots

    PubMed Central

    Laur, Joan; Hacke, Uwe G.

    2013-01-01

    Isohydric plants tend to maintain a water potential homeostasis primarily by controlling water loss via stomatal conductance. However, there is accumulating evidence that plants can also modulate water uptake in a dynamic manner. The dynamics of water uptake are influenced by aquaporin-mediated changes in root hydraulics. Most studies in this area have been conducted on herbaceous plants, and less is known about responses of woody plants. Here a study was conducted to determine how roots of hybrid poplar plants (Populus trichocarpa×deltoides) respond to a step change in transpirational demand. The main objective was to measure the expression of selected aquaporin genes and to assess how transcriptional responses correspond to changes in root water flow (Q R) and other parameters of water relations. A subset of plants was grown in shade and was subsequently exposed to a 5-fold increase in light level. Another group of plants was grown at ~95% relative humidity (RH) and was then subjected to lower RH while the light level remained unchanged. Both plant groups experienced a transient drop in stem water potentials. At 28h after the increase in transpirational demand, water potentials recovered. This recovery was associated with changes in the expression of PIP1 and PIP2 subfamily genes and an increase in Q R. Stomata of plants growing at high RH were larger and showed incomplete closure after application of abscisic acid. Since stomatal conductance remained high and unchanged in these plants, it is suggested that the recovery in water potential in these plants was largely driven by the increase in Q R. PMID:23599275

  3. Nighttime transpiration observed over a larch forest in Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Kobayashi, N.; Hiyama, T.; Fukushima, Y.; Lopez, M. L.; Hirano, T.; Fujinuma, Y.

    2007-03-01

    Nighttime transpiration in a larch forest in northern Japan was investigated using concurrent measurements of the energy budget below and above the canopy and sap flow velocities. Upward latent heat flux (lE) above the canopy was observed on ˜20% of nights during the growing season. Nighttime lE was ˜7% of daily totals during the dry season (September-October) and averaged ˜3% over the entire growing season. A relatively low contribution of the understory to lE (<30%) and strong synchronicity between larch sap flow rates and lE on two warm windy nights indicated nighttime lE, occurring when warm dry air intruded from above, was largely due to transpiration from the larch overstory. High canopy conductance on some nights relative to reported maximum cuticular conductance and a strong correlation between canopy conductance and air humidity on these nights indicate the stomata of the larch trees did not close tightly at night.

  4. [Greenhouse tomato transpiration and its affecting factors: correlation analysis and model simulation].

    PubMed

    Yao, Yong-Zhe; Li, Jian-Ming; Zhang, Rong; Sun, San-Jie; Chen, Kai-Li

    2012-07-01

    A pot experiment was conducted to study the correlations between the daily transpiration of greenhouse tomato and the related affecting factors such as total leaf area per plant, soil relative moisture content, air temperature, relative humidity, and solar radiation under different treatments of supplementary irrigation. A regression model for the daily transpiration of greenhouse tomato was established. There existed significant linear correlations between the daily transpiration and the test affecting factors, and the affecting factors had complicated mutual effects. Soil relative moisture content was the main decision factor of the transpiration, with the decision coefficient being 27.4%, and daily minimum relative humidity was the main limiting factor, with the decision coefficient being -119.7%. The square value of the regression coefficient (R2) between the predicted and measured tomato daily transpiration was 0.81, root mean squared error (RMSE) was 68.52 g, and relative prediction error (RE) was 19.4%, suggesting that the regression model established by using the main affecting factors selected through path analysis could better simulate the daily transpiration of greenhouse tomato. PMID:23173461

  5. Transpiration And Regenerative Cooling Of Rocket Engine

    NASA Technical Reports Server (NTRS)

    Obrien, Charles J.

    1989-01-01

    Transpiration cooling extends limits of performance. Addition of transpiration cooling to regeneratively-cooled rocket-engine combustion chamber proposed. Modification improves performance of engine by allowing use of higher chamber pressure. Throat section of combustion-chamber wall cooled by transpiration, while chamber and nozzle sections cooled by fluid flowing in closed channels. Concept applicable to advanced, high-performance terrestrial engines or some kinds of industrial combustion chambers. With proper design, cooling scheme makes possible to achieve higher chamber pressure and higher overall performance in smaller engine.

  6. A respiration based description of plant growth rate responses to temperature

    Microsoft Academic Search

    Richard S. Criddle; Bruce N. Smith; Lee D. Hansen

    1997-01-01

    .  ?The temperature dependence of metabolic rates determines how plant growth rates vary with temperature. This paper shows that\\u000a equations on physiological relations between respiration rates (i.e. rates of heat loss and CO2 evolution) and growth rates can be used to describe temperature effects on plant growth rate. Incorporating measured values\\u000a of plant respiratory heat and CO2 rates at a few

  7. Transpiration efficiency of a tropical pioneer tree (Ficus insipida) in relation to soil fertility

    Microsoft Academic Search

    Lucas A. Cernusak; Klaus Winter; Jorge Aranda; Benjamin L. Turner; John D. Marshall

    2007-01-01

    The response of whole-plant water-use efficiency, termed transpiration efficiency (TE), to variation in soil fertility was assessed in a tropical pioneer tree, Ficus insipida Willd. Measurements of stable isotope ratios (d13C, d18O, d15N), elemental concentrations (C, N, P), plant growth, instantaneous leaf gas exchange, and whole-plant water use were used to analyse the mechanisms controlling TE. Plants were grown in-

  8. MORPHOLOGICAL AND PHYSIOLOGICAL INTERACTIONS IN DIVERSE PLANT COMMUNITIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Morphological and physiological interactions among plants in multi-species forage mixtures affect responses to environmental stresses. White clover growing under drought stress in a five-species mixture which included a deep-rooted forb had greater transpiration rates and higher leaf water potential...

  9. A Phytotoxicity Test Using Transpiration of Willows

    Microsoft Academic Search

    S. Trapp; K. C. Zambrano; K. O. Kusk; U. Karlson

    2000-01-01

    A short-term acute toxicity assay for willow trees growing in contaminated solution or in polluted soil was developed and\\u000a tested. The test apparatus consists of an Erlenmeyer flask with a prerooted tree cutting growing in it. Growth and reduction\\u000a of transpiration are used to determine toxicity. Transpiration is closely related to photosynthesis and growth, but is easier\\u000a and faster to

  10. Sap flux–upscaled canopy transpiration, stomatal conductance, and water use efficiency in an old growth forest in the Great Lakes region of the United States

    Microsoft Academic Search

    Jianwu Tang; Paul V. Bolstad; Brent E. Ewers; Ankur R. Desai; Kenneth J. Davis; Eileen V. Carey

    2006-01-01

    Combining sap flux and eddy covariance measurements provides a means to study plant stomatal conductance and the relationship between transpiration and photosynthesis. We measured sap flux using Granier-type sensors in a northern hardwood-dominated old growth forest in Michigan, upscaled to canopy transpiration, and calculated canopy conductance. We also measured carbon and water fluxes with the eddy covariance method and derived

  11. Sap flux-upscaled canopy transpiration, stomatal conductance, and water use efficiency in an old growth forest in the Great Lakes region of the United States

    Microsoft Academic Search

    Jianwu Tang; Paul V. Bolstad; Brent E. Ewers; Ankur R. Desai; Kenneth J. Davis; Eileen V. Carey

    2006-01-01

    Combining sap flux and eddy covariance measurements provides a means to study plant stomatal conductance and the relationship between transpiration and photosynthesis. We measured sap flux using Granier-type sensors in a northern hardwood-dominated old growth forest in Michigan, upscaled to canopy transpiration, and calculated canopy conductance. We also measured carbon and water fluxes with the eddy covariance method and derived

  12. Stem Extension Rate in Light-Grown Plants 1

    PubMed Central

    Lecharny, Alain; Schwall, Michael; Wagner, Edgar

    1985-01-01

    Low temperature pulses have two effects on the circadian rhythm exhibited by stem extension rate of green Chenopodium rubrum plants. First, low temperature pulses have the same effect on the phasing of the rhythm as a dark period interrupting continuous light. Second, low temperature pulses stimulate stem extension rate during the 10 hours immediately following the end of the pulse. A difference in temperature between soil and air increases this effect. In any case, it is the change in temperature which is essential and not a specific temperature. Effects of light and temperature on phasing and amplitude of the rhythm explain why the maximal stem growth is observed under normal photo-thermoperiodic conditions, i.e. a high temperature during the photoperiod and a low temperature during the dark period. PMID:16664462

  13. Coupling gross primary production and transpiration for a consistent estimate of canopy water use efficiency

    NASA Astrophysics Data System (ADS)

    Yebra, Marta; van Dijk, Albert

    2015-04-01

    Water use efficiency (WUE, the amount of transpiration or evapotranspiration per unit gross (GPP) or net CO2 uptake) is key in all areas of plant production and forest management applications. Therefore, mutually consistent estimates of GPP and transpiration are needed to analysed WUE without introducing any artefacts that might arise by combining independently derived GPP and ET estimates. GPP and transpiration are physiologically linked at ecosystem level by the canopy conductance (Gc). Estimates of Gc can be obtained by scaling stomatal conductance (Kelliher et al. 1995) or inferred from ecosystem level measurements of gas exchange (Baldocchi et al., 2008). To derive large-scale or indeed global estimates of Gc, satellite remote sensing based methods are needed. In a previous study, we used water vapour flux estimates derived from eddy covariance flux tower measurements at 16 Fluxnet sites world-wide to develop a method to estimate Gc using MODIS reflectance observations (Yebra et al. 2013). We combined those estimates with the Penman-Monteith combination equation to derive transpiration (T). The resulting T estimates compared favourably with flux tower estimates (R2=0.82, RMSE=29.8 W m-2). Moreover, the method allowed a single parameterisation for all land cover types, which avoids artefacts resulting from land cover classification. In subsequent research (Yebra et al, in preparation) we used the same satellite-derived Gc values within a process-based but simple canopy GPP model to constrain GPP predictions. The developed model uses a 'big-leaf' description of the plant canopy to estimate the mean GPP flux as the lesser of a conductance-limited and radiation-limited GPP rate. The conductance-limited rate was derived assuming that transport of CO2 from the bulk air to the intercellular leaf space is limited by molecular diffusion through the stomata. The radiation-limited rate was estimated assuming that it is proportional to the absorbed photosynthetically active radiation (PAR), calculated as the product of the fraction of absorbed PAR (fPAR) and PAR flux. The proposed algorithm performs well when evaluated against flux tower GPP (R2=0.79, RMSE= 1.93 µmol m2 s-1). Here we use GPP and T estimates previously derived at the same 16 Fluxnet sites to analyse WUE. Satellite-derived WUE explained variation in (long-term average) WUE among plant functional types but evergreen needleleaf had higher WUE than predicted. The benefit of our approach is that it uses mutually consistent estimates of GPP and T to derive canopy-level WUE without any land cover classification artefacts. References Baldocchi, D. (2008). Turner Review No. 15: 'Breathing' of the terrestrial biosphere: lessons learned from a global network of carbon dioxide flux measurement systems. Australian Journal of Botany, 56, 26 Kelliher, F.M., Leuning, R., Raupach, M.R., & Schulze, E.D. (1995). Maximum conductances for evaporation from global vegetation types. Agricultural and Forest Meteorology, 73, 1-16 Yebra, M., Van Dijk, A., Leuning, R., Huete, A., & Guerschman, J.P. (2013). Evaluation of optical remote sensing to estimate actual evapotranspiration and canopy conductance. Remote Sensing of Environment, 129, 250-261

  14. Risk-taking plants

    PubMed Central

    Sade, Nir; Gebremedhin, Alem; Moshelion, Menachem

    2012-01-01

    Water scarcity is a critical limitation for agricultural systems. Two different water management strategies have evolved in plants: an isohydric strategy and an anisohydric strategy. Isohydric plants maintain a constant midday leaf water potential (?leaf) when water is abundant, as well as under drought conditions, by reducing stomatal conductance as necessary to limit transpiration. Anisohydric plants have more variable ?leaf and keep their stomata open and photosynthetic rates high for longer periods, even in the presence of decreasing leaf water potential. This risk-taking behavior of anisohydric plants might be beneficial when water is abundant, as well as under moderately stressful conditions. However, under conditions of intense drought, this behavior might endanger the plant. We will discuss the advantages and disadvantages of these two water-usage strategies and their effects on the plant’s ability to tolerate abiotic and biotic stress. The involvement of plant tonoplast AQPs in this process will also be discussed. PMID:22751307

  15. Do root hydraulic properties change during the early vegetative stage of plant development in barley (Hordeum vulgare)?

    PubMed Central

    Suku, Shimi; Knipfer, Thorsten; Fricke, Wieland

    2014-01-01

    Background and Aims As annual crops develop, transpirational water loss increases substantially. This increase has to be matched by an increase in water uptake through the root system. The aim of this study was to assess the contributions of changes in intrinsic root hydraulic conductivity (Lp, water uptake per unit root surface area, driving force and time), driving force and root surface area to developmental increases in root water uptake. Methods Hydroponically grown barley plants were analysed during four windows of their vegetative stage of development, when they were 9–13, 14–18, 19–23 and 24–28 d old. Hydraulic conductivity was determined for individual roots (Lp) and for entire root systems (Lpr). Osmotic Lp of individual seminal and adventitious roots and osmotic Lpr of the root system were determined in exudation experiments. Hydrostatic Lp of individual roots was determined by root pressure probe analyses, and hydrostatic Lpr of the root system was derived from analyses of transpiring plants. Key Results Although osmotic and hydrostatic Lp and Lpr values increased initially during development and were correlated positively with plant transpiration rate, their overall developmental increases (about 2-fold) were small compared with increases in transpirational water loss and root surface area (about 10- to 40-fold). The water potential gradient driving water uptake in transpiring plants more than doubled during development, and potentially contributed to the increases in plant water flow. Osmotic Lpr of entire root systems and hydrostatic Lpr of transpiring plants were similar, suggesting that the main radial transport path in roots was the cell-to-cell path at all developmental stages. Conclusions Increase in the surface area of root system, and not changes in intrinsic root hydraulic properties, is the main means through which barley plants grown hydroponically sustain an increase in transpirational water loss during their vegetative development. PMID:24287810

  16. Experimental studies of transpiration cooling with shock interaction in hypersonic flow, part B

    NASA Technical Reports Server (NTRS)

    Holden, Michael S.

    1994-01-01

    This report describes the result of experimental studies conducted to examine the effects of the impingement of an oblique shock on the flowfield and surface characteristics of a transpiration-cooled wall in turbulent hypersonic flow. The principal objective of this work was to determine whether the interaction between the oblique shock and the low-momentum region of the transpiration-cooled boundary layer created a highly distorted flowfield and resulted in a significant reduction in the cooling effectiveness of the transpiration-cooled surface. As a part of this program, we also sought to determine the effectiveness of transpiration cooling with nitrogen and helium injectants for a wide range of blowing rates under constant-pressure conditions in the absence of shock interaction. This experimental program was conducted in the Calspan 48-Inch Shock Tunnel at nominal Mach numbers of 6 and 8, for a Reynolds number of 7.5 x 10(exp 6). For these test conditions, we obtained fully turbulent boundary layers upstream of the interaction regions over the transpiration-cooled segment of the flat plate. The experimental program was conducted in two phases. In the first phase, we examined the effects of mass-addition level and coolant properties on the cooling effectiveness of transpiration-cooled surfaces in the absence of shock interaction. In the second phase of the program, we examined the effects of oblique shock impingement on the flowfield and surface characteristics of a transpiration-cooled surface. The studies were conducted for a range of shock strengths with nitrogen and helium coolants to examine how the distribution of heat transfer and pressure and the characteristics of the flowfield in the interaction region varied with shock strength and the level of mass addition from the transpiration-cooled section of the model. The effects of the distribution of the blowing rate along the interaction regions were also examined for a range of blowing rates through the transpiration-cooled panels. The regions of shockwave/boundary layer interaction examined in these studies were induced by oblique shocks generated with a sharp, flat plate, inclined to the freestream at angles of 5 degrees, 7.5 degrees, and 10 degrees. It was found that, in the absence of an incident shock, transpiration cooling was a very effective method for reducing both the heat transfer and the skin friction loads on the surface. The helium coolant was found to be significantly more effective than nitrogen, because of its low molecular weight and high specific heat. The studies of shock-wave/transpiration-cooled surface interaction demonstrated that the interaction region between the incident shock and the low-momentum transpiration-cooled boundary layer did not result in a significant increase in the size of attached or separated interaction regions, and did not result in significant flowfield distortions above the interaction region. The increase in heating downstream of the shock-impingement point could easily be reduced to the values without shock impingement by a relatively small increase in the transpiration cooling in this region. Surprisingly, this increase in cooling rate did not result in a significant increase in size of the region ahead of the incident shock or create a significantly enlarged interaction region with a resultant increase in the distortion level in the inviscid flow. Thus, transpiration cooling appears to be a very effective technique to cool the internal surfaces of scramjet engines, where shocks in the engine would induce large local increases in wall heating and create viscous/inviscid interactions that could significantly disturb the smooth flow through the combustor. However, if hydrogen is used as the coolant, burning upstream of shock impingement might result in localized hot spots. Clearly, further research is needed in this area.

  17. Genetic variability for leaf growth rate and duration under water deficit in sunflower: analysis of responses at cell, organ, and plant level.

    PubMed

    Pereyra-Irujo, Gustavo A; Velázquez, Luciano; Lechner, Leandra; Aguirrezábal, Luis A N

    2008-01-01

    Plants under water deficit reduce leaf growth, thereby reducing transpiration rate at the expense of reduced photosynthesis. The objective of this work was to analyse the response of leaf growth to water deficit in several sunflower genotypes in order to identify and quantitatively describe sources of genetic variability for this trait that could be used to develop crop varieties adapted to specific scenarios. The genetic variability of the response of leaf growth to water deficit was assessed among 18 sunflower (Helianthus annuus L.) inbred lines representing a broad range of genetic diversity. Plants were subjected to long-term, constant-level, water-deficit treatments, and the response to water deficit quantified by means of growth models at cell-, leaf-, and plant-scale. Significant variation among lines was found for the response of leaf expansion rate and of leaf growth duration, with an equal contribution of these responses to the variability in the reduction of leaf area. Increased leaf growth duration under water deficit is usually suggested to be caused by changes in the activity of cell-wall enzymes, but the present results suggest that the duration of epidermal cell division plays a key role in this response. Intrinsic genotypic responses of rate and duration at a cellular scale were linked to genotypic differences in whole-plant leaf area profile to water deficit. The results suggest that rate and duration responses are the result of different physiological mechanisms, and therefore capable of being combined to increase the variability in leaf area response to water deficit. PMID:18448477

  18. Transpiration along an age series of Eucalyptus globulus plantations in southeastern Australia

    Microsoft Academic Search

    David I. Forrester; John J. Collopy; Jim D. Morris

    2010-01-01

    Many of the world's Eucalyptus plantations are grown on short rotations of 15 years or less, which often covers the most rapid phase of stand development and peaks in growth rates and leaf areas. Since transpiration is related to stand leaf area these short rotations that make use of rapid early growth rates, may also maximise plantation water use, which

  19. Effects of atmospheric humidity on net photosynthesis, transpiration, and stomatal resistance

    Microsoft Academic Search

    D. Overdieck; B. R. Strain

    1981-01-01

    Rhizomes ofHydrocotyle plants from three contrasting habitats were cloned and the ramets grown under controlled environmental conditions. Measurements of net photosynthesis, transpiration, and total leaf diffusion resistance were used to examine possible physiological adaptations to specific field environments. Increasing dryness of the growth chamber environment had large effects on gas exchange (CO2 and water vapor) and on total diffusion resistance

  20. ENVIRONMENTAL AND GENETIC VARIATION INFLUENCE NIGHTTIME TRANSPIRATION IN THE C4 GRASS DISTICHLIS SPICATA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Theory predicts that plants should close their stomata at night to decrease water loss when photosynthetic carbon gain cannot occur. However, significant nighttime stomatal conductance (g) and transpiration (E) have been measured in a wide range of species and functional groups. Little is currentl...

  1. NIGHTIME TRANSPIRATION AND NUTRIENT ACQUISITION: IS THERE A BENEFIT OF LOSING WATER AT NIGHT?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nighttime stomatal conductance and transpiration can lead to substantial water loss occurring at non-photosynthetic times in C3 and C4 plants. Water loss without simultaneous carbon gain is intuitively wasteful, however it is possible that either there is no cost when water supply is sufficient or ...

  2. NIGHTTIME TRANSPIRATION AND NUTRIENT ACQUISITION: IS THERE A BENEFIT OF LOSING WATER AT NIGHT?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nighttime stomatal conductance and transpiration can lead to a substantial amount of water loss occurring at non-photosynthetic times in C3 and C4 plants. Water loss without simultaneous carbon gain is intuitively wasteful, however it is possible that either the phenomenon is not a cost under non-w...

  3. Mycorrhizal association between the desert truffle Terfezia boudieri and Helianthemum sessiliflorum alters plant physiology and fitness to arid conditions

    Microsoft Academic Search

    Tidhar Turgeman; Jiftach Ben Asher; Nurit Roth-Bejerano; Varda Kagan-Zur; Yoram Kapulnik; Yaron Sitrit

    The host plant Helianthemum sessiliflorum was inoculated with the mycorrhizal desert truffle Terfezia boudieri Chatin, and the subsequent effects of the ectomycorrhizal relationship on host physiology were determined. Diurnal measurements\\u000a revealed that mycorrhizal (M) plants had higher rates of photosynthesis (35%), transpiration (18%), and night respiration\\u000a (49%) than non-mycorrhizal (NM) plants. Consequently, M plants exhibited higher biomass accumulation, higher shoot-to-root

  4. Energy conversion using thermal transpiration : optimization of a Knudsen compressor

    E-print Network

    Klein, Toby A. (Toby Anna)

    2012-01-01

    Knudsen compressors are devices without any moving parts that use the nanoscale phenomenon of thermal transpiration to pump or compress a gas. Thermal transpiration takes place when a gas is in contact with a solid boundary ...

  5. Groundwater Constraints on Simulated Transpiration Variability over Southeastern Australian Forests

    E-print Network

    Evans, Jason

    Groundwater Constraints on Simulated Transpiration Variability over Southeastern Australian Forests 2012) ABSTRACT A land surface scheme with and without groundwater­vegetation interactions is used to explore the impact of rainfall variability on transpiration over drought-vulnerable regions

  6. Multiple major increases and decreases in mitochondrial substitution rates in the plant family Geraniaceae

    Microsoft Academic Search

    Christopher L Parkinson; Jeffrey P Mower; Yin-Long Qiu; Andrew J Shirk; Keming Song; Nelson D Young; Claude W dePamphilis; Jeffrey D Palmer

    2005-01-01

    BACKGROUND: Rates of synonymous nucleotide substitutions are, in general, exceptionally low in plant mitochondrial genomes, several times lower than in chloroplast genomes, 10–20 times lower than in plant nuclear genomes, and 50–100 times lower than in many animal mitochondrial genomes. Several cases of moderate variation in mitochondrial substitution rates have been reported in plants, but these mostly involve correlated changes

  7. Influence of leaf size, orientation, and arrangement on temperature and transpiration in three high-elevation, large-leafed herbs

    Microsoft Academic Search

    G. N. Geller; W. K. Smith

    1982-01-01

    The temperature and water relations of the largleafed, high-elevation species Frasera speciosa, Balsamorhiza sagittata, and Rumex densiflorus were evaluated in the Medicine Bow Mountains of southeast Wyoming (USA) to determine the influence of leaf size, orientation, and arrangement on transpiration. These species characteristically have low minimum stomatal resistances (-1) and high maximum transpiration rates (>260 mg m-2s-1 for F. speciosa).

  8. APPLICATION OF THE TRANSPIRATION METHOD FOR AEROSERVOELASTIC PREDICTION USING CFD

    Microsoft Academic Search

    Cole H. Stephens; Andrew S. Arena; Kajal K. Gupta

    Research presented in this paper illustrates the implementation of the transpiration boundary condition in steady and unsteady aeroelastic and aeroservoelastic simulations. For two reference cases, the AGARD 445.6 wing and the BACT wing with a finite-span flap, application of the transpiration method has demonstrated the effectiveness of applying the transpiration boundary condition at a variety of Mach numbers on configurations

  9. Oxygen isotope signatures of transpired water vapor - the role of isotopic non-steady-state transpiration of Mediterranean cork-oaks (Quercus suber L.)under natural conditions

    NASA Astrophysics Data System (ADS)

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Werner, Christiane

    2014-05-01

    Oxygen isotope signatures of transpired water vapor (?T) are a powerful tracer of water movement from plants to the global scale, but little is known on short-term variability of ?T as direct high-frequency measurements are lacking. A laser spectrometer was coupled to a gas-exchange chamber directly estimating branch-level fluxes and ?T to evaluate a modeling approach and investigate the role of isotopic non-steady-state transpiration under natural conditions in distinct seasons in cork-oaks (Quercus suber L.). The isotope signature of transpiration (?T) always deviated from steady-state predictions (?T) throughout most of the day even when leaf water at the evaporating sites is near isotopic steady-state. Thus, ?T is further amplified compared to deviations of leaf water isotopes from steady-state, specifically in dry conditions. High agreement was found for direct estimates and modeled ?T assuming non-steady-state conditions of leaf-water at the evaporating sites. Strong isoforcing on the atmosphere of transpiration in isotopic non-steady-state imply that short-term variations in ?T have likely consequences for large-scale applications, e.g. partitioning of ecosystem evapotranspiration or carbon fluxes using C18O16O, or satellite-based applications.

  10. Effects of Kaolin and Pinolene Film-forming Polymers on Water Relations and Photosynthetic Rate of Tuberose (Polianthes tuberosa L.)

    Microsoft Academic Search

    Ansary E. Moftah; Abdulrahman I. Al-Humaid

    2005-01-01

    The effects of pinolene-base Vapor Gard (VG) emulsion type film and Kaolin (Surround WP) particle type film antitranspirants on stomatal behavior, water status, carbon assimilation and transpiration rate of tuberose (Polianthes tuberosa L.) cv. double plants grown under the irrigation regimes of 100, 80 and 60% of total evapotranspiration (ET) values were investigated to select the most suitable antitranspirant for

  11. Planting Thoughts

    NSDL National Science Digital Library

    Integrated Teaching and Learning Program,

    Students gain an understanding of the parts of a plant, plant types and how they produce their own food from sunlight through photosynthesis. They also learn about transpiration, the process by which plants release moisture to the atmosphere. With this understanding, students test the effects of photosynthesis and transpiration by growing a plant from seed. They learn how plants play an important part in maintaining a balanced environment in which the living organisms of the Earth survive. This lesson is part of a series of six lessons in which students use their evolving understanding of various environments and the engineering design process, to design and create their own model biodome ecosystems.

  12. Real-time variable rate Pix® application system using a plant height sensor 

    E-print Network

    Beck, Andy Dwayne

    2001-01-01

    The objective of this study was to develop a chemical application system that could measure plant size, determine the optimum chemical rate to apply and control that application. A plant height sensor, the MEPRT growth relationship software...

  13. Real-time variable rate Pix® application system using a plant height sensor

    E-print Network

    Beck, Andy Dwayne

    2001-01-01

    The objective of this study was to develop a chemical application system that could measure plant size, determine the optimum chemical rate to apply and control that application. A plant height sensor, the MEPRT growth relationship software...

  14. Relating xylem cavitation to transpiration in cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Acoustic emmisions (AEs) from xylem cavitation events are characteristic of transpiration processes. Even though a body of work employing AE exists with a large number of species, cotton and other agronomically important crops have either not been investigated, or limited information exists. A few s...

  15. Transpiration characteristics of a rubber plantation in central Cambodia.

    PubMed

    Kobayashi, Nakako; Kumagai, Tomo'omi; Miyazawa, Yoshiyuki; Matsumoto, Kazuho; Tateishi, Makiko; Lim, Tiva K; Mudd, Ryan G; Ziegler, Alan D; Giambelluca, Thomas W; Yin, Song

    2014-03-01

    The rapid and widespread expansion of rubber plantations in Southeast Asia necessitates a greater understanding of tree physiology and the impacts of water consumption on local hydrology. Sap flow measurements were used to study the intra- and inter-annual variations in transpiration rate (Et) in a rubber stand in the low-elevation plain of central Cambodia. Mean stand sap flux density (JS) indicates that rubber trees actively transpire in the rainy season, but become inactive in the dry season. A sharp, brief drop in JS occurred simultaneously with leaf shedding in the middle of the dry season in January. Although the annual maxima of JS were approximately the same in the two study years, the maximum daily stand Et of ?2.0 mm day(-1) in 2010 increased to ?2.4 mm day(-1) in 2011. Canopy-level stomatal response was well explained by changes in solar radiation, vapor pressure deficit, soil moisture availability, leaf area, and stem diameter. Rubber trees had a relatively small potential to transpire at the beginning of the study period, compared with average diffuse-porous species. After 2 years of growth in stem diameter, transpiration potential was comparable to other species. The sensitivity of canopy conductance (gc) to atmospheric drought indicates isohydric behavior of rubber trees. Modeling also predicted a relatively small sensitivity of gc to the soil moisture deficit and a rapid decrease in gc under extreme drought conditions. However, annual observations suggest the possibility of a change in leaf characteristics with tree maturity and/or initiation of latex tapping. The estimated annual stand Et was 469 mm year(-1) in 2010, increasing to 658 mm year(-1) in 2011. Diagnostic analysis using the derived gc model showed that inter-annual change in stand Et in the rapidly growing young rubber stand was determined mainly by tree growth rate, not by differences in air and soil variables in the surrounding environment. Future research should focus on the potentially broad applicability of the relationship between Et and tree size as well as environmental factors at stands different in terms of clonal type and age. PMID:24646689

  16. The transpiration of water at negative pressures in a synthetic tree

    Microsoft Academic Search

    Tobias D. Wheeler; Abraham D. Stroock

    2008-01-01

    Plant scientists believe that transpiration-the motion of water from the soil, through a vascular plant, and into the air-occurs by a passive, wicking mechanism. This mechanism is described by the cohesion-tension theory: loss of water by evaporation reduces the pressure of the liquid water within the leaf relative to atmospheric pressure; this reduced pressure pulls liquid water out of the

  17. Processes driving nocturnal transpiration and implications for estimating land evapotranspiration

    PubMed Central

    de Dios, Víctor Resco; Roy, Jacques; Ferrio, Juan Pedro; Alday, Josu G.; Landais, Damien; Milcu, Alexandru; Gessler, Arthur

    2015-01-01

    Evapotranspiration is a major component of the water cycle, yet only daytime transpiration is currently considered in Earth system and agricultural sciences. This contrasts with physiological studies where 25% or more of water losses have been reported to occur occurring overnight at leaf and plant scales. This gap probably arose from limitations in techniques to measure nocturnal water fluxes at ecosystem scales, a gap we bridge here by using lysimeters under controlled environmental conditions. The magnitude of the nocturnal water losses (12–23% of daytime water losses) in row-crop monocultures of bean (annual herb) and cotton (woody shrub) would be globally an order of magnitude higher than documented responses of global evapotranspiration to climate change (51–98 vs. 7–8?mm yr?1). Contrary to daytime responses and to conventional wisdom, nocturnal transpiration was not affected by previous radiation loads or carbon uptake, and showed a temporal pattern independent of vapour pressure deficit or temperature, because of endogenous controls on stomatal conductance via circadian regulation. Our results have important implications from large-scale ecosystem modelling to crop production: homeostatic water losses justify simple empirical predictive functions, and circadian controls show a fine-tune control that minimizes water loss while potentially increasing posterior carbon uptake. PMID:26074373

  18. Processes driving nocturnal transpiration and implications for estimating land evapotranspiration.

    PubMed

    de Dios, Víctor Resco; Roy, Jacques; Ferrio, Juan Pedro; Alday, Josu G; Landais, Damien; Milcu, Alexandru; Gessler, Arthur

    2015-01-01

    Evapotranspiration is a major component of the water cycle, yet only daytime transpiration is currently considered in Earth system and agricultural sciences. This contrasts with physiological studies where 25% or more of water losses have been reported to occur occurring overnight at leaf and plant scales. This gap probably arose from limitations in techniques to measure nocturnal water fluxes at ecosystem scales, a gap we bridge here by using lysimeters under controlled environmental conditions. The magnitude of the nocturnal water losses (12-23% of daytime water losses) in row-crop monocultures of bean (annual herb) and cotton (woody shrub) would be globally an order of magnitude higher than documented responses of global evapotranspiration to climate change (51-98 vs. 7-8?mm yr(-1)). Contrary to daytime responses and to conventional wisdom, nocturnal transpiration was not affected by previous radiation loads or carbon uptake, and showed a temporal pattern independent of vapour pressure deficit or temperature, because of endogenous controls on stomatal conductance via circadian regulation. Our results have important implications from large-scale ecosystem modelling to crop production: homeostatic water losses justify simple empirical predictive functions, and circadian controls show a fine-tune control that minimizes water loss while potentially increasing posterior carbon uptake. PMID:26074373

  19. Studies of shock/shock interaction on smooth and transpiration-cooled hemispherical nosetips in hypersonic flow

    NASA Technical Reports Server (NTRS)

    Holden, M. S.; Rodriguez, K. M.; Nowak, R. J.

    1991-01-01

    Experimental studies are conducted to examine the utilization of transpiration cooling to reduce the peak-heating loads in areas of shock/shock interaction. Smooth and transpiration-cooled nosetip models, 12 inches in diameter, were employed in these studies, which focused on defining the pressure distributions and heat transfer in type III and IV interaction areas. Transpiration cooling was determined to significantly increase the size of the shock layer and to move the peak-heating point around the body. A transpiration-cooling rate of more than 30 percent of the freestream maximum flux did not lower the peak-heating level more than 10 percent, but the integrated heating loads were reduced.

  20. Enhancement of transpiration by ethylene is responsible for absence of internodal elongation in floating rice at low humidity.

    PubMed

    Azuma, Tetsushi; Hatanaka, Tomoko; Uchida, Naotsugu; Yasuda, Takeshi

    2003-09-01

    Internodal elongation in floating rice (Oryza sativa) is known to be enhanced by treatment with ethylene or gibberellic acid (GA3) at high relative humidity (RH). However, ethylene-induced internodal elongation is inhibited at low RH, while GA3-induced internodal elongation is hardly affected by humidity. We examined the effects of ethylene and GA3 on the rate of transpiration in stem segments incubated at 30% or 100% RH. Ethylene promoted the transpiration of stem segments at 30% RH, but not at 100% RH, while GA3 had little effect on transpiration at either 30% or 100% RH. We propose that the absence of ethylene-induced internodal elongation at low RH is due, at least in part, to ethylene-induced transpiration. PMID:14593815

  1. Canopy photosynthesis and transpiration in micro-gravity: Gas exchange measurements aboard Mir

    Microsoft Academic Search

    O. Monje; G. E. Bingham; J. G. Carman; W. F. Campbell; F. B. Salisbury; B. K. Eames; V. Sytchev; M. A. Levinskikh; I. Podolsky

    2000-01-01

    The SVET Greenhouse on-board the Orbital Station Mir was used to measure canopy photosynthesis and transpiration rates for the first time in space. During the Greenhouse IIB experiment on Mir (June – January 1997), carbon and water vapor fluxes from two wheat (cv. Superdwarf) canopies were measured using the US developed Gas Exchange Measurement System (GEMS). Gas analyzers capable of

  2. Temporal and spatial changes in grassland transpiration detected using Landsat TM and ETM+ imagery

    Microsoft Academic Search

    C. D. Holifield; S. McElroy; M. S. Moran; R. Bryant; T. Miura; W. E. Emmerich

    The water deficit index (WDI) derived from Landsat imagery was used to detect temporal and spatial changes in grassland transpiration. The WDI, which estimates relative evapotranspiration rates based on meteorological data and the relation between surface reflectance and temperature, has been successfully applied over heterogeneous terrain with little a priori information. In this study, WDI was derived from a 10-year,

  3. Reduction of Transpiration of Leaves through Stomatal Closure Induced by Alkenylsuccinic Acids

    Microsoft Academic Search

    Israel Zelitch

    1964-01-01

    Low concentrations of long-chain alkenylsuccinic acids and certain of their derivatives inhibit stomatal opening in a tobacco-leaf disk assay, and when used as a spray. The monomethyl ester of decenylsuccinic acid is presently the most effective of this class of compounds. Stomatal closure induced with this substance is accompanied by a significant reduction in the rate of transpiration. These inhibitors

  4. Modelling orange tree root water uptake active area by minimally invasive ERT data and transpiration measurements

    NASA Astrophysics Data System (ADS)

    Vanella, Daniela; Boaga, Jacopo; Perri, Maria Teresa; Consoli, Simona; Cassiani, Giorgio

    2015-04-01

    The comprehension of the hydrological processes involving plant root dynamics is crucial for implementing water saving measures in agriculture. This is particular urgent in areas, like those Mediterranean, characterized by scarce water availability. The study of root water dynamics should not be separated from a more general analysis of the mass and energy fluxes transferred in the soil-plant-atmosphere continuum. In our study, in order to carry this inclusive approach, minimal invasive 3D time-lapse electrical resistivity tomography (ERT) for soil moisture estimation was combined with plant transpiration fluxes directly measured with Sap Flow (SF) techniques and Eddy Covariance methods, and volumetric soil moisture measurements by TDR probes. The main objective of this inclusive approach was to accurately define root-zone water dynamics and individuate the root-area effectively active for water and nutrient uptake process. The monitoring was carried out in Eastern Sicily (south Italy) in summers 2013 and 2014, within an experimental orange orchard farm. During the first year of experiment (October 2013), ERT measurements were carried out around the pertinent volume of one fully irrigated tree, characterized by a vegetation ground cover of 70%; in the second year (June 2014), ERT monitoring was conducted considering a cutting plant, thus to evaluate soil water dynamics without the significant plant transpiration contribution. In order to explore the hydrological dynamics of the root zone volume surrounded by the monitored tree, the resistivity data acquired during the ERT monitoring were converted into soil moisture content distribution by a laboratory calibration based on the soil electrical properties as a function of moisture content and pore water electrical conductivity. By using ERT data in conjunction with the agro-meteorological information (i.e. irrigation rates, rainfall, evapotranspiration by Eddy Covariance, transpiration by Sap Flow and soil moisture content by TRD) of the test area, a spatially distributed one-dimensional (1D) model that solves the Richards' equation was applied; in the model the van Genuchten parameters were obtained by laboratory analysis of soil water retention and soil permeability at saturation. Results of the 1D model were successfully compared with both ERT-based soil moisture dynamics and TDR measurements of soil moisture. The modelling allows to defining the soil volume interested by root water uptake process and its extent. In particular, this volume results significantly smaller (i.e. surface area of 1.75 m2, with 0.4 m cm thickness) than expected, considering the design of the drip irrigation scheme adopted in the farm. The obtained results confirm that ERT is a technique that (i) can provide a lot of information on small scale and vegetation related processes; (ii) the integration with physical modelling is essential to capture the meaning of space-time signal changes; (iii) in the case of the orange orchard, this approach shows that about half of the irrigated water is wasted.

  5. Nitrogen to phosphorus ratio of plant biomass versus soil solution in a tropical pioneer tree, Ficus insipida

    PubMed Central

    Garrish, Valerie; Cernusak, Lucas A.; Winter, Klaus; Turner, Benjamin L.

    2010-01-01

    It is commonly assumed that the nitrogen to phosphorus (N:P) ratio of a terrestrial plant reflects the relative availability of N and P in the soil in which the plant grows. Here, this was assessed for a tropical pioneer tree, Ficus insipida. Seedlings were grown in sand and irrigated with nutrient solutions containing N:P ratios ranging from <1 to >100. The experimental design further allowed investigation of physiological responses to N and P availability. Homeostatic control over N:P ratios was stronger in leaves than in stems or roots, suggesting that N:P ratios of stems and roots are more sensitive indicators of the relative availability of N and P at a site than N:P ratios of leaves. The leaf N:P ratio at which the largest plant dry mass and highest photosynthetic rates were achieved was ?11, whereas the corresponding whole-plant N:P ratio was ?6. Plant P concentration varied as a function of transpiration rate at constant nutrient solution P concentration, possibly due to transpiration-induced variation in the mass flow of P to root surfaces. The transpiration rate varied in response to nutrient solution N concentration, but not to nutrient solution P concentration, demonstrating nutritional control over transpiration by N but not P. Water-use efficiency varied as a function of N availability, but not as a function of P availability. PMID:20591897

  6. Nitrogen to phosphorus ratio of plant biomass versus soil solution in a tropical pioneer tree, Ficus insipida.

    PubMed

    Garrish, Valerie; Cernusak, Lucas A; Winter, Klaus; Turner, Benjamin L

    2010-08-01

    It is commonly assumed that the nitrogen to phosphorus (N:P) ratio of a terrestrial plant reflects the relative availability of N and P in the soil in which the plant grows. Here, this was assessed for a tropical pioneer tree, Ficus insipida. Seedlings were grown in sand and irrigated with nutrient solutions containing N:P ratios ranging from <1 to >100. The experimental design further allowed investigation of physiological responses to N and P availability. Homeostatic control over N:P ratios was stronger in leaves than in stems or roots, suggesting that N:P ratios of stems and roots are more sensitive indicators of the relative availability of N and P at a site than N:P ratios of leaves. The leaf N:P ratio at which the largest plant dry mass and highest photosynthetic rates were achieved was approximately 11, whereas the corresponding whole-plant N:P ratio was approximately 6. Plant P concentration varied as a function of transpiration rate at constant nutrient solution P concentration, possibly due to transpiration-induced variation in the mass flow of P to root surfaces. The transpiration rate varied in response to nutrient solution N concentration, but not to nutrient solution P concentration, demonstrating nutritional control over transpiration by N but not P. Water-use efficiency varied as a function of N availability, but not as a function of P availability. PMID:20591897

  7. Plant genotypic diversity reduces the rate of consumer resource utilization

    PubMed Central

    McArt, Scott H.; Thaler, Jennifer S.

    2013-01-01

    While plant species diversity can reduce herbivore densities and herbivory, little is known regarding how plant genotypic diversity alters resource utilization by herbivores. Here, we show that an invasive folivore—the Japanese beetle (Popillia japonica)—increases 28 per cent in abundance, but consumes 24 per cent less foliage in genotypic polycultures compared with monocultures of the common evening primrose (Oenothera biennis). We found strong complementarity for reduced herbivore damage among plant genotypes growing in polycultures and a weak dominance effect of particularly resistant genotypes. Sequential feeding by P. japonica on different genotypes from polycultures resulted in reduced consumption compared with feeding on different plants of the same genotype from monocultures. Thus, diet mixing among plant genotypes reduced herbivore consumption efficiency. Despite positive complementarity driving an increase in fruit production in polycultures, we observed a trade-off between complementarity for increased plant productivity and resistance to herbivory, suggesting costs in the complementary use of resources by plant genotypes may manifest across trophic levels. These results elucidate mechanisms for how plant genotypic diversity simultaneously alters resource utilization by both producers and consumers, and show that population genotypic diversity can increase the resistance of a native plant to an invasive herbivore. PMID:23658201

  8. Reaction rate constants of superoxide scavenging by plant antioxidants

    Microsoft Academic Search

    Dirk Taubert; Thomas Breitenbach; Andreas Lazar; Petra Censarek; Steffi Harlfinger; Reinhard Berkels; Wolfgang Klaus; Renate Roesen

    2003-01-01

    Plant phenols may exert protective effects by scavenging superoxide, which is implicated in tissue damage and accelerated inactivation of vasorelaxing nitric oxide. Preventing the interaction of superoxide with tissue biomolecules depends not only on the extent of superoxide scavenging but also on scavenging velocity. However, information on superoxide scavenging kinetics of plant phenols is scarce. We describe an improved lucigenin-based

  9. Coupling time to silking with plant growth rate in maize

    Microsoft Academic Search

    Lucas Borrás; Mark E. Westgate; Juan P. Astini; Laura Echarte

    2007-01-01

    In maize (Zea mays L.), progress towards pistillate flower maturity (silking) is highly dependent upon the environmental conditions around flowering. Under conditions that inhibit plant growth, female flower development is delayed relative to that of the male flowers resulting in an increase in the anthesis–silking interval (ASI). Although variation in ASI has been extensively documented, its relationship to plant growth

  10. Do Plants Sweat? Core Content

    E-print Network

    Kessler, Bruce

    . Preassessment 1. Why is a forest more humid than a field or farmland? 2. Describe some differences that allow, Kentucky, Michigan, (_________ your state)? How? OER Use KIRIS Assessment, Plants and Transpiration. [Show of light, and amount of water. Data on the amount of water each plant loses through transpiration

  11. Inferring dominant controls on transpiration across a hillslope transect from ecohydrological measurements and thermodynamic limits

    NASA Astrophysics Data System (ADS)

    Renner, Maik; Hassler, Sibylle; Blume, Theresa; Weiler, Markus; Hildebrandt, Anke; Guderle, Marcus; Schymanki, Stan; Kleidon, Axel

    2015-04-01

    We combine ecohydrological observations of sapflow and soil moisture-derived root water uptake with a thermodynamically constrained estimate of atmospheric evaporative demand to infer the dominant controls on forest transpiration in complex terrain. Specifically we hypothesize that short term variability is dominated by land-atmosphere interaction, whereas site-specific controls determine the sensitivity of transpiration to atmospheric demand. To explore topographic controls on forest transpiration we use data from a extensive ecohydrological measurement setup which was established within the CAOS (Catchments As Organized Systems) research unit. Specifically, we use data of 5 sites along a steep hillslope transect (15 - 22°) in a deciduous beech forest in Luxembourg. Two sites are located at the north-facing slope, three at the opposite south-facing slope. Each site was equipped with soil moisture sensors at three depths in three profiles as well as heat-pulse sap flow sensors in four trees per site. Meteorological observations (solar radiation, temperature, humidity) are recorded at a nearby pasture. Both sapflow and soil moisture-derived root water uptake allow for an independent assessment of site-scale transpiration. Although each method has specific limitations, there is a robust relation across sites. This relationship can be used to estimate site scale growing season transpiration. Atmospheric evaporative demand is estimated through thermodynamically constrained evaporation which only requires absorbed solar radiation and temperature as input data and thus allows prediction of evaporative demand independent of surface conditions. The joint analysis of daily data shows that sapflow is highly linearly correlated with atmospheric demand (r2 = 0.82) independent of location, tree size and soil moisture content. Hence the sensitivity of sapflow and root water uptake to atmospheric demand allows for estimating long term controls on transpiration. Aspect of the hillslopes and stand characteristics were found to be the major long term control: the south-facing sites with larger atmospheric demand show significantly lower sensitivity to atmospheric demand than the north-facing sites. Interestingly, we find that the sensitivity is decreasing with stand density, which is markedly different between the contrasting hillslopes. Thus periodical water limitation induced by larger absorption of solar radiation on the south-facing slopes may have led to long term plant adaptation or forest management strategies which satisfy the trade-off between highly variable atmospheric demand and the depletion of soil water storage. In summary, the strong linear link of daily transpiration to atmospheric demand as well as the more long-term adaptation to soil moisture availability may allow for the spatially explicit prediction of forest transpiration from solar radiation, temperature and stand characteristics.

  12. Preciptation, Evaporation, and Transpiration Activity

    NSDL National Science Digital Library

    Amy Townsend-Small

    The students must use crayons or colored pencils to create maps of global precipitation and evaporation rates. One worksheet is provided to each group of students. Then a representative from each group explains their map to the rest of the class, and the instructor shows a similar map from NOAA or NASA.

  13. Transpired Air Collectors - Ventilation Preheating

    SciTech Connect

    Christensen, C.

    2006-06-22

    Many commercial and industrial buildings have high ventilation rates. Although all that fresh air is great for indoor air quality, heating it can be very expensive. This short (2-page) fact sheet describes a technology available to use solar energy to preheat ventilation air and dramatically reduce utility bills.

  14. A dynamical system perspective on plant hydraulic failure

    NASA Astrophysics Data System (ADS)

    Manzoni, Stefano; Katul, Gabriel; Porporato, Amilcare

    2014-06-01

    Photosynthesis is governed by leaf water status that depends on the difference between the rates of transpiration and water supply from the soil and through the plant xylem. When transpiration increases compared to water supply, the leaf water potential reaches a more negative equilibrium, leading to water stress. Both high atmospheric vapor pressure deficit and low soil moisture increase the water demand while decreasing the supply due to lowered soil-to-root conductance and xylem cavitation. Therefore, dry conditions may eventually reduce the leaf water potential to the point of collapsing the plant hydraulic system. This "hydraulic failure" is shown to correspond to a fold bifurcation where the environmental parameters (vapor pressure deficit and soil moisture) trigger the loss of a physiologically sustainable equilibrium. Using a minimal plant hydraulic model, coordination among plant hydraulic traits is shown to result in increased resilience to environmental stresses, thereby impeding hydraulic failure unless hydraulic traits deteriorate due to prolonged water shortage or other damages.

  15. Transpiration in the Global Water Cycle

    NASA Astrophysics Data System (ADS)

    Schlesinger, W. H.; Jasechko, S.

    2014-12-01

    A compilation of 81 studies that have partitioned evapotranspiration (ET) into its components—transpiration (T) and evaporation (E)—at the ecosystem scale indicates that T accounts for 61% (±15% s.d.) of ET and returns approximately 39±10% of incident precipitation (P) to the atmosphere, creating a dominant force in the global water cycle. T as a proportion of ET is highest in tropical rainforests (70±14 %) and lowest in steppes, shrublands and deserts (51±15%), but there is no relationship of T/ET versus P across all available data (R2 = 0.01). Changes to transpiration due to increasing CO2 concentrations, land use changes, shifting ecozones and climate warming are expected to have significant impacts upon runoff and groundwater recharge, reflecting human impacts on the global biogeochemical cycle of water.

  16. Downscaling Model Predictions of Transpiration from Daily to Diurnal Level By Retrieving Physiologically Consistent Model Parameters from Sap Flux Data

    NASA Astrophysics Data System (ADS)

    Mackay, D. S.

    2002-05-01

    Hydrologic models that calculate transpiration rely on estimates of stomatal conductance (Gs), obtained using a combination of factors that emphasize carbon assimilation rates or environmental factors such as atmospheric vapor pressure deficit (D) and soil water limitation. Soil water limitation has been focus of many studies into understanding the role of hydrologic processes on vegetation function. However, diurnal transpiration, and hence short-term water and energy cycling, responds more intensely to D when soil water is not limiting. While empirical equations are widely available to relate Gs to D, they pose many challenges for capturing diurnal water fluxes among species. Recent theory and a growing volume of data suggest that at moderate to high water loss rates stomata close to regulate leaf water potential and to prevent runaway cavitation. It has been shown that when vegetation is regulating water potential they follow the relation, Gs = Gsref - m*ln(D) where m = 0.6 * Gsref and Gsref is a reference conductance at D=1kPa. TREES (Terrestrial Regional Ecosystem Exchange Simulator), a diurnal land surface process model with canopy processes operating at half-hourly time-steps, was evaluated using sap flux data for a number of conifer and deciduous tree species from northern Wisconsin. Daily transpiration varied by 2-3 times among species. Monte Carlo parameter sampling was combined with automated calibration of daily predictions of transpiration to daily sap flux transpiration. Diurnal fluxes were then compared to the diurnal sap flux rates without further parameter adjustment. Numerous model realizations explained the variation in daily transpiration over the course of two months. However, among the best predictors of daily transpiration, those that followed water potential regulation theory (m = 0.6 * Gsref) were better able to match the measured diurnal flux rates.

  17. A new look at water transport regulation in plants.

    PubMed

    Martínez-Vilalta, Jordi; Poyatos, Rafael; Aguadé, David; Retana, Javier; Mencuccini, Maurizio

    2014-10-01

    Plant function requires effective mechanisms to regulate water transport at a variety of scales. Here, we develop a new theoretical framework describing plant responses to drying soil, based on the relationship between midday and predawn leaf water potentials. The intercept of the relationship (?) characterizes the maximum transpiration rate per unit of hydraulic transport capacity, whereas the slope (?) measures the relative sensitivity of the transpiration rate and plant hydraulic conductance to declining water availability. This framework was applied to a newly compiled global database of leaf water potentials to estimate the values of ? and ? for 102 plant species. Our results show that our characterization of drought responses is largely consistent within species, and that the parameters ? and ? show meaningful associations with climate across species. Parameter ? was ?1 in most species, indicating a tight coordination between the gas and liquid phases of water transport, in which canopy transpiration tended to decline faster than hydraulic conductance during drought, thus reducing the pressure drop through the plant. The quantitative framework presented here offers a new way of characterizing water transport regulation in plants that can be used to assess their vulnerability to drought under current and future climatic conditions. PMID:24985503

  18. When do plants modify fluvial processes? Plant-hydraulic interactions under variable flow and sediment supply rates

    NASA Astrophysics Data System (ADS)

    Manners, Rebecca B.; Wilcox, Andrew C.; Kui, Li; Lightbody, Anne F.; Stella, John C.; Sklar, Leonard S.

    2015-02-01

    Flow and sediment regimes shape alluvial river channels; yet the influence of these abiotic drivers can be strongly mediated by biotic factors such as the size and density of riparian vegetation. We present results from an experiment designed to identify when plants control fluvial processes and to investigate the sensitivity of fluvial processes to changes in plant characteristics versus changes in flow rate or sediment supply. Live seedlings of two species with distinct morphologies, tamarisk (Tamarix spp.) and cottonwood (Populus fremontii), were placed in different configurations in a mobile sand-bed flume. We measured the hydraulic and sediment flux responses of the channel at different flow rates and sediment supply conditions representing equilibrium (sediment supply = transport rate) and deficit (sediment supply < transport rate). We found that the hydraulic and sediment flux responses during sediment equilibrium represented a balance between abiotic and biotic factors and was sensitive to increasing flow rates and plant species and configuration. Species-specific traits controlled the hydraulic response: compared to cottonwood, which has a more tree-like morphology, the shrubby morphology of tamarisk resulted in less pronation and greater reductions in near-bed velocities, Reynolds stress, and sediment flux rates. Under sediment-deficit conditions, on the other hand, abiotic factors dampened the effect of variations in plant characteristics on the hydraulic response. We identified scenarios for which the highest stem-density patch, independent of abiotic factors, dominated the fluvial response. These results provide insight into how and when plants influence fluvial processes in natural systems.

  19. Relationship between Hexokinase and the Aquaporin PIP1 in the Regulation of Photosynthesis and Plant Growth

    PubMed Central

    Kelly, Gilor; Sade, Nir; Attia, Ziv; Secchi, Francesca; Zwieniecki, Maciej; Holbrook, N. Michele; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Granot, David

    2014-01-01

    Increased expression of the aquaporin NtAQP1, which is known to function as a plasmalemma channel for CO2 and water, increases the rate of both photosynthesis and transpiration. In contrast, increased expression of Arabidopsis hexokinase1 (AtHXK1), a dual-function enzyme that mediates sugar sensing, decreases the expression of photosynthetic genes and the rate of transpiration and inhibits growth. Here, we show that AtHXK1 also decreases root and stem hydraulic conductivity and leaf mesophyll CO2 conductance (gm). Due to their opposite effects on plant development and physiology, we examined the relationship between NtAQP1 and AtHXK1 at the whole-plant level using transgenic tomato plants expressing both genes simultaneously. NtAQP1 significantly improved growth and increased the transpiration rates of AtHXK1-expressing plants. Reciprocal grafting experiments indicated that this complementation occurs when both genes are expressed simultaneously in the shoot. Yet, NtAQP1 had only a marginal effect on the hydraulic conductivity of the double-transgenic plants, suggesting that the complementary effect of NtAQP1 is unrelated to shoot water transport. Rather, NtAQP1 significantly increased leaf mesophyll CO2 conductance and enhanced the rate of photosynthesis, suggesting that NtAQP1 facilitated the growth of the double-transgenic plants by enhancing mesophyll conductance of CO2. PMID:24498392

  20. Urban tree transpiration over turf and asphalt surfaces

    Microsoft Academic Search

    Roger Kjelgren; Thayne Montague

    1998-01-01

    We used a two-layer canopy model to study transpiration of tree species as affected by energy-balance properties of a vegetated and paved surface. During several dawn-to-dusk studies, tree transpiration, stomatal conductance, leaf temperature (Tl), and several microclimate variables, were measured over turf and an asphalt surface. Cumulative transpiration was estimated from a leaf energy-balance equation applied to a tree crown

  1. Effect of a chemical manufacturing plant on community cancer rates

    Microsoft Academic Search

    Trish Mannes; Katy Emmett; Alan Willmore; Tim Churches; Vicky Sheppeard; Jill Kaldor

    2005-01-01

    BACKGROUND: We conducted a retrospective study to determine if potential past exposure to dioxin had resulted in increased incidence of cancer in people living near a former manufacturing plant in New South Wales, Australia. During operation, from 1928 to 1970, by-products of the manufacturing process, including dioxin and other chemical waste, were dumped into wetlands and mangroves, discharged into a

  2. Cytokinin Import Rate as a Signal for Photosynthetic Acclimation to Canopy Light Gradients1[W][OA

    PubMed Central

    Boonman, Alex; Prinsen, Els; Gilmer, Frank; Schurr, Ulrich; Peeters, Anton J.M.; Voesenek, Laurentius A.C.J.; Pons, Thijs L.

    2007-01-01

    Plants growing in dense canopies are exposed to vertical light gradients and show photosynthetic acclimation at the whole-plant level, resulting in efficient photosynthetic carbon gain. We studied the role of cytokinins transported through the transpiration stream as one of probably multiple signals for photosynthetic acclimation to light gradients using both tobacco (Nicotiana tabacum) and Arabidopsis (Arabidopsis thaliana). We show that substantial variation in leaf transpiration parallels the light gradient in tobacco canopies and experimental reduction of the transpiration rate of a leaf, independent of light, is sufficient to reduce photosynthetic capacity in both species, as well as transcript levels of the small subunit of Rubisco (rbcS) gene in Arabidopsis. Mass spectrometric analysis of xylem sap collected from intact, transpiring tobacco plants revealed that shaded leaves import less cytokinin than leaves exposed to high light. In Arabidopsis, reduced transpiration rate of a leaf in the light is associated with lower cytokinin concentrations, including the bioactive trans-zeatin and trans-zeatin riboside, as well as reduced expression of the cytokinin-responsive genes ARR7 and ARR16. External application of cytokinin to shaded leaves rescued multiple shade effects, including rbcS transcript levels in both species, as did locally induced cytokinin overproduction in transgenic tobacco plants. From these data, we conclude that light gradients over the foliage of a plant result in reduced cytokinin activity in shaded leaves as a consequence of reduced import through the xylem and that cytokinin is involved in the regulation of whole-plant photosynthetic acclimation to light gradients in canopies. PMID:17277095

  3. On the representativeness of plot size and location for scaling transpiration from trees to a stand

    NASA Astrophysics Data System (ADS)

    Mackay, D. Scott; Ewers, Brent E.; Loranty, Michael M.; Kruger, Eric L.

    2010-06-01

    Scaling transpiration from trees to larger areas is a fundamental problem in ecohydrology. For scaling stand transpiration from sap flux sensors we asked if plot representativeness depended on plot size and location, the magnitude of environmental drivers, parameter needs for ecosystem models, and whether the goal was to estimate transpiration per unit ground area (EC), per unit leaf area (EL), or canopy stomatal conductance (GS). Sap flux data were collected in 108 trees with heat dissipation probes, and biometric properties were measured for 752 trees within a 1.44 ha Populus tremuloides stand along an upland-to-wetland gradient. EC was estimated for the stand using eight different plot sizes spanning a radius of 2.0-12.0 m. Each estimate of EC was derived from 200 plots placed randomly throughout the stand. We also derived leaf area index (L), canopy closure (PCC), and the canopy average reference stomatal conductance (GSref), which are key parameters used in modeling transpiration and evapotranspiration. With increasing plot size, EC declined monotonically but EL and GSref were largely invariant. Interplot variance of EC also declined with increasing plot size, at a rate that was independent of vapor pressure deficit. Plot representativeness was dependent on location within the stand. Scaling to the stand required three plots spanning the upland to wetland, with one to at most 10 trees instrumented for sap flux. Plots that were chosen to accurately reflect the spatial covariation of L, PCC, and GSref were most representative of the stand.

  4. Transpiration and water relations of poplar trees growing close to the water table.

    PubMed

    Zhang, Heping; Morison, James I. L.; Simmonds, Lester P.

    1999-07-01

    Sap flow was measured on five branches of two poplar (Populus trichocarpa Torr. & A. Gray x P. tacamahaca L.) trees from June to September 1994 in the south of England with stem-surface, heat balance gauges, and was scaled up to estimate transpiration from single trees on the basis of leaf area. On six days, stomatal conductance and plant water potential were measured simultaneously with a porometer and pressure chamber, respectively. The effects of solar radiation (S), vapor pressure deficit (D) and stomatal conductance on transpiration were evaluated. Sap flow per unit leaf area (F(a)) was closely related to the time course of demand attributable to S and D throughout the season, and only slightly affected by the water content of the top 120 cm of soil. Although F(a) increased linearly at low values of D, it showed a plateau with increases in D above 1.2 kPa. The canopy coupling coefficient (1 - Omega) ranged from 0.48 to 0.78 with a mean of 0.65 +/- 0.01, indicating that transpiration was controlled more by stomatal conductance than by incident radiation. The seasonal pattern of tree water loss followed potential evaporation with a peak in late June or early July. On bright days, daily transpiration over the projected crown area was 3.6 mm early in the season, 3.8 mm in mid-season, and 2.7 mm late in the season. The water balance of the system indicated that poplar trees took 15-60% of water transpired from groundwater, with the proportion increasing as the soil in the unsaturated zone dried out. Access to the water table resulted in high predawn water potentials throughout the season. Estimated hydraulic resistance to water flow in the soil-tree system was in the range of 1.5 to 1.93 x 10(6) MPa s m(-3). PMID:12651530

  5. Effect of gender on sap-flux-scaled transpiration in a dominant riparian tree species: Box elder (Acer negundo)

    E-print Network

    Ehleringer, Jim

    is a dioecious riparian tree species with a spatial segregation of the sexes along soil moisture gradients of dioecious riparian trees has direct consequences on ecosystem ET, particularly along stream margins. Shifts000232. 1. Introduction [2] Plants take up and transpire large amounts of water to the extent

  6. Understanding Tree Water Use Across the Snow-Rain Transition in Idaho's Mountain Watersheds: Feedbacks Between Stream Networks, Transpiration, and Basin Geomorphology

    NASA Astrophysics Data System (ADS)

    Whiting, J. A.; Godsey, S.; Reinhardt, K.; Thackray, G. D.

    2014-12-01

    Warming trends are expected to reduce mountain snow pack, increase evapotranspiration, and thus diminish the sometimes limited water supplies of many intermountain streams and rivers. While it is believed that water that is transpired is no longer available for streamflow, it remains uncertain how the timing and quantity of transpiration differ between snow-dominated and rain-dominated elevations, and how alterations in transpiration in these regions affect surface water flow in mountain stream networks. To understand the spatiotemporal relationships of transpiration, we measured Douglas fir water use across the snow-rain transition line/elevation in the Pioneer Creek watershed of Idaho's Frank Church River of No Return Wilderness in 2014. We also recorded stream discharge and monitored surface flow areal extent in four subwatersheds with contrasting geomorphologic controls on the channel network, including moraine and fault controls. We sought to test the hypotheses that (1) Douglas fir trees at snow-dominated elevations would transpire less water each year, and do so later in the melt-season compared to Douglas fir trees at rain-dominated elevations, and (2), that patterns of stream network expansion and contraction will reflect patterns of timing in transpiration rates. Preliminary analyses suggest that transpiration timing is similar across all elevations, and that stream network extent varies minimally across a 20 to 60% variation in streamflow. Summer transpiration varied more strongly with tree size and age than with elevation. We present comparisons of drainage density across the sites at different flow rates, and relate them to geomorphic controls present within each basin. Understanding the present relationships of streamflow with transpiration across snowline contributes to more robust predictions of changes in water resources as a result of climate change.

  7. Determination of methane emission rates on a biogas plant using data from laser absorption spectrometry.

    PubMed

    Groth, Angela; Maurer, Claudia; Reiser, Martin; Kranert, Martin

    2015-02-01

    The aim of the work was to establish a method for emission control of biogas plants especially the observation of fugitive methane emissions. The used method is in a developmental stage but the topic is crucial to environmental and economic issues. A remote sensing measurement method was adopted to determine methane emission rates of a biogas plant in Rhineland-Palatinate, Germany. An inverse dispersion model was used to deduce emission rates. This technique required one concentration measurement with an open path tunable diode laser absorption spectrometer (TDLAS) downwind and upwind the source and basic wind information, like wind speed and direction. Different operating conditions of the biogas plant occurring on the measuring day (December 2013) could be represented roughly in the results. During undisturbed operational modes the methane emission rate averaged 2.8 g/s, which corresponds to 4% of the methane gas production rate of the biogas plant. PMID:25446786

  8. Organ-distinctive changes in respiration rates of rice plants under nickel stress

    Microsoft Academic Search

    Andreu Llamas; Amparo Sanz

    2008-01-01

    Nickel (Ni) is an essential mineral element that may accumulate to toxic levels in soils due to anthropogenic activities.\\u000a The growth of rice plants cultured hydroponically was severely impaired when Ni concentration was raised from 0.1 to 0.5 mM.\\u000a However, the decrease in plant growth was not accompanied by any significant effect on respiration rates at the whole plant\\u000a level. Short-term

  9. Rep-rated Z-Pinch Power Plant Concept - Direct Energy Conversion and Shrapnel Generation

    Microsoft Academic Search

    John S. de Groot; Niels Gronbech-Jensen; Greg Miller; Craig L. Olsen; Gary E. Rochau; Mark S. Derzon; Steven A. Slutz; Rick B. Spielman; Per F. Peterson; Gregory A. Rochau; Robert R. Pederson

    2000-01-01

    We are developing direct energy conversion schemes and shrapnel generation models to be used to optimize a high yield z-pinch IFE power plant concept. The concept uses high yield ( 10 GJ) at low rep-rate ( 0.1 Hz), with a Recyclable Transmission Line (RTL) to provide the necessary standoff between the fusion target and the power plant chamber. The RTL

  10. Contemporary evolution of plant growth rate following experimental removal of herbivores.

    PubMed

    Turley, Nash E; Odell, Walter C; Schaefer, Hanno; Everwand, Georg; Crawley, Michael J; Johnson, Marc T J

    2013-05-01

    Herbivores are credited with driving the evolutionary diversification of plant defensive strategies over macroevolutionary time. For this to be true, herbivores must also cause short-term evolution within plant populations, but few studies have experimentally tested this prediction. We addressed this gap using a long-term manipulative field experiment where exclosures protected 22 plant populations from natural rabbit herbivory for <1 to 26 years. We collected seeds of Rumex acetosa L. (Polygonaceae) from our plots and grew them in a common greenhouse environment to quantify evolved differences among populations in individual plant growth rate, tolerance to herbivory, competitive ability, and the concentration of secondary metabolites (tannins and oxalate) implicated in defense against herbivores. In 26 years without rabbit herbivory, plant growth rate decreased linearly by 30%. We argue that plant growth rate has evolved as a defense against intense rabbit herbivory. In contrast, we found no change in tolerance to herbivory or concentrations of secondary metabolites. We also found no change in competitive ability, suggesting that contemporary evolution may not feed back to alter ecological interactions within this plant community. Our results combined with those of other studies show that the evolution of gross morphological traits such as growth rate in response to herbivory may be common, which calls into question assumptions about some of the most popular theories of plant defense. PMID:23598357

  11. Transpiration and root development of urban trees in structural soil stormwater reservoirs.

    PubMed

    Bartens, Julia; Day, Susan D; Harris, J Roger; Wynn, Theresa M; Dove, Joseph E

    2009-10-01

    Stormwater management that relies on ecosystem processes, such as tree canopy interception and rhizosphere biology, can be difficult to achieve in built environments because urban land is costly and urban soil inhospitable to vegetation. Yet such systems offer a potentially valuable tool for achieving both sustainable urban forests and stormwater management. We evaluated tree water uptake and root distribution in a novel stormwater mitigation facility that integrates trees directly into detention reservoirs under pavement. The system relies on structural soils: highly porous engineered mixes designed to support tree root growth and pavement. To evaluate tree performance under the peculiar conditions of such a stormwater detention reservoir (i.e., periodically inundated), we grew green ash (Fraxinus pennsylvanica Marsh.) and swamp white oak (Quercus bicolor Willd.) in either CUSoil or a Carolina Stalite-based mix subjected to three simulated below-system infiltration rates for two growing seasons. Infiltration rate affected both transpiration and rooting depth. In a factorial experiment with ash, rooting depth always increased with infiltration rate for Stalite, but this relation was less consistent for CUSoil. Slow-drainage rates reduced transpiration and restricted rooting depth for both species and soils, and trunk growth was restricted for oak, which grew the most in moderate infiltration. Transpiration rates under slow infiltration were 55% (oak) and 70% (ash) of the most rapidly transpiring treatment (moderate for oak and rapid for ash). We conclude this system is feasible and provides another tool to address runoff that integrates the function of urban green spaces with other urban needs. PMID:19707704

  12. EFFECTS OF ELEVATED ATMOSPHERIC CO{sub 2} ON CANOPY TRANSPIRATION IN SENESCENT SPRING WHEAT

    SciTech Connect

    GROSSMAN,S.; KIMBALL,B.A.; HUNSAKER,D.J.; LONG,S.P.; GARCIA,R.L.; KARTSCHALL,TH.; WALL,G.W.; PINTER,P.J,JR.; WECHSUNG,F.; LAMORTE,R.L.

    1998-12-31

    The seasonal course of canopy transpiration and the diurnal courses of latent heat flux of a spring wheat crop were simulated for atmospheric CO{sub 2} concentrations of 370 {micro}mol mol{sup {minus}1} and 550 {micro}mol mol{sup {minus}1}. The hourly weather data, soil parameters and the irrigation and fertilizer treatments of the Free-Air Carbon Dioxide Enrichment wheat experiment in Arizona (1992/93) were used to drive the model. The simulation results were tested against field measurements with special emphasis on the period between anthesis and maturity. A model integrating leaf photosynthesis and stomatal conductance was scaled to a canopy level in order to be used in the wheat growth model. The simulated intercellular CO{sub 2} concentration, C{sub i} was determined from the ratio of C{sub i} to the CO{sub 2} concentration at the leaf surface, C{sub s} the leaf to air specific humidity deficit and a possibly unfulfilled transpiration demand. After anthesis, the measured assimilation rates of the flag leaves decreased more rapidly than their stomatal conductances, leading to a rise in the C{sub i}/C{sub s} ratio. In order to describe this observation, an empirical model approach was developed which took into account the leaf nitrogen content for the calculation of the C{sub i}/C{sub s} ratio. Simulation results obtained with the new model version were in good agreement with the measurements. If changes in the C{sub i}/C{sub s} ratio accorded to the decrease in leaf nitrogen content during leaf senescence were not considered in the model, simulations revealed an underestimation of the daily canopy transpiration of up to 20% and a decrease in simulated seasonal canopy transpiration by 10%. The measured reduction in the seasonal sum of canopy transpiration and soil evaporation owing to CO{sub 2} enrichment, in comparison, was only about 5%.

  13. Desiccant cooling using unglazed transpired solar collectors

    SciTech Connect

    Pesaran, A.A. [National Renewable Energy Lab., Golden, CO (United States)] [National Renewable Energy Lab., Golden, CO (United States); Wipke, K. [Stanford Univ., CA (United States)] [Stanford Univ., CA (United States)

    1992-05-01

    The use of unglazed solar collectors for desiccant regeneration in a solid desiccant cooling cycle was investigated because these collectors are lower in cost than conventional glazed flat-plate collectors. Using computer models, the performance of a desiccant cooling ventilation cycle integrated with either unglazed transpired collectors or conventional glazed flat-plate collectors was obtained. We found that the thermal performance of the unglazed system was lower than the thermal performance of the glazed system because the unglazed system could not take advantage of the heat of adsorption released during the dehumidification process. For a 3-ton cooling system, although the area required for the unglazed collector was 69% more than that required for the glazed collector, the cost of the unglazed collector array was 44% less than the cost of the glazed collector array. The simple payback period of the unglazed system was half of the payback period of the glazed collector when compared to an equivalent gas-fired system. Although the use of unglazed transpired collectors makes economic sense, some practical considerations may limit their use in desiccant regeneration. 8 refs.

  14. Desiccant cooling using unglazed transpired solar collectors

    NASA Astrophysics Data System (ADS)

    Pesaran, A. A.; Wipke, K.

    1992-05-01

    The use of unglazed solar collectors for desiccant regeneration in a solid desiccant cooling cycle was investigated because these collectors are lower in cost than conventional glazed flat-plate collectors. Using computer models, the performance of a desiccant cooling ventilation cycle integrated with either unglazed transpired collectors or conventional glazed flat-plate collectors was obtained. We found that the thermal performance of the unglazed system was lower than the thermal performance of the glazed system because the unglazed system could not take advantage of the heat of adsorption released during the dehumidification process. For a 3-ton cooling system, although the area required for the unglazed collector was 69 percent more than that required for the glazed collector, the cost of the unglazed collector array was 44 percent less than the cost of the glazed collector array. The simple payback period of the unglazed system was half of the payback period of the glazed collector when compared to an equivalent gas-fired system. Although the use of unglazed transpired collectors makes economic sense, some practical considerations may limit their use in desiccant regeneration.

  15. Combustion chamber struts can be effectively transpiration cooled

    NASA Technical Reports Server (NTRS)

    Palmer, G. H.

    1966-01-01

    Vapor-deposited sintering technique increases the feasible temperature range of transpiration-cooled structural members in combustion chambers. This technique produces a porous mass of refractory metal wires around a combustion chamber structural member. This mass acts as a transpiration-cooled surface for a thick-walled tube.

  16. Transpiring wall supercritical water oxidation test reactor design report

    Microsoft Academic Search

    B. L. Haroldsen; D. Y. Ariizumi; B. E. Mills; B. G. Brown; D. C. Rousar

    1996-01-01

    Sandia National Laboratories is working with GenCorp, Aerojet and Foster Wheeler Development Corporation to develop a transpiring wall supercritical water oxidation reactor. The transpiring wall reactor promises to mitigate problems of salt deposition and corrosion by forming a protective boundary layer of pure supercritical water. A laboratory scale test reactor has been assembled to demonstrate the concept. A 1\\/4 scale

  17. The relative role of stomata in transpiration and assimilation

    Microsoft Academic Search

    I. R. Cowan; J. H. Troughton

    1971-01-01

    The ways in which transpiration and assimilation depend on stomatal aperture are compared. It is shown that transpiration and assimilation are equally sensitive to change of stomatal aperture when the internal resistance to assimilation is equal to an effective resistance to evaporation which exists because of the coupling of heat and vapour exchanges between leaf and atmosphere. Generally the ratio

  18. Dioecy is associated with higher diversification rates in flowering plants.

    PubMed

    Käfer, J; de Boer, H J; Mousset, S; Kool, A; Dufay, M; Marais, G A B

    2014-07-01

    In angiosperms, dioecious clades tend to have fewer species than their nondioecious sister clades. This departure from the expected equal species richness in the standard sister clade test has been interpreted as implying that dioecious clades diversify less and has initiated a series of studies suggesting that dioecy might be an 'evolutionary dead end'. However, two of us recently showed that the 'equal species richness' null hypothesis is not valid in the case of derived char acters, such as dioecy, and proposed a new test for sister clade comparisons; preliminary results, using a data set available in the litterature, indicated that dioecious clades migth diversify more than expected. However, it is crucial for this new test to distinguish between ancestral and derived cases of dioecy, a criterion that was not taken into account in the available data set. Here, we present a new data set that was obtained by searching the phylogenetic literature on more than 600 completely dioecious angiosperm genera and identifying 115 sister clade pairs for which dioecy is likely to be derived (including > 50% of the dioecious species). Applying the new sister clade test to this new dataset, we confirm the preliminary result that dioecy is associated with an increased diversification rate, a result that does not support the idea that dioecy is an evolutionary dead end in angiosperms. The traits usually associated with dioecy, that is, an arborescent growth form, abiotic pollination, fleshy fruits or a tropical distribution, do not influence the diversification rate. Rather than a low diversification rate, the observed species richness patterns of dioecious clades seem to be better explained by a low transition rate to dioecy and frequent losses. PMID:24797166

  19. Rootstock does not affect net photosynthesis, dark respiration, specific leaf weight, and transpiration of apple leaves

    Microsoft Academic Search

    J. A. Barden; D. C. Ferree

    1979-01-01

    There was no effect of rootstock on the net photosynthesis Pn of 1-year-old vegetative, container-grown Delicious trees in 2 experiments. Rootstock effects on specific leaf weight (SLW) were slight in one experiment, and absent in another. There was no influence of rootstock on shoot growth, leaf number, transpiration rate (Tr) or dark respiration (Rd), each of which was determined in

  20. Reference Canopy Stomatal Conductance Explains Spatiotemporal Patterns of Tree Transpiration

    NASA Astrophysics Data System (ADS)

    Loranty, M. M.; Mackay, D. S.; Ewers, B. E.; Kruger, E. L.; Traver, E.

    2007-12-01

    Increased heterogeneity in patterns of whole tree transpiration (EC) with increasing atmospheric vapor pressure deficit (D) suggests a dynamic response of sap flow velocity (JS) to environmental drivers. We hypothesized that differences in reference stomatal conductance (GSref), stomatal conductance at D = 1kPa, would explain the spatiotemporal dynamics of JS. Using a coupled model of plant hydraulic and biochemical processes we tested this hypothesis with sap flux data for 106 aspen ( Populus tremuloides) and 108 sugar maple ( Acer saccharum) trees collected from plots using in 2-D cyclic sampling scheme during the summer of 2005 in northern Wisconsin. Inverse modeling is used to estimate GSref for each tree. For each species, trees from across the ranges of JS and diameter distributions are compared. GSref explained temporal variability in spatial patterns of EC We explore several possible mechanistic explanations for differences in GSref among trees. Topoedaphic factors are considered to determine if location within a stand has an effect. We also consider competition with neighboring individuals as a possible explanation. Variations in GSref in aspen were explained in part by competition for light between neighboring individuals, while competition for light was not a significant factor for sugar maple. Based on simulation analysis we identify possible biochemical feedbacks as drivers of the variability in plant hydraulics. Other factors examined included micro-topography within both sites.

  1. Improvement of growth rate of plants by bubble discharge in water

    NASA Astrophysics Data System (ADS)

    Takahata, Junichiro; Takaki, Koichi; Satta, Naoya; Takahashi, Katsuyuki; Fujio, Takuya; Sasaki, Yuji

    2015-01-01

    The effect of bubble discharge in water on the growth rate of plants was investigated experimentally for application to plant cultivation systems. Spinach (Spinacia oleracea), radish (Raphanus sativus var. sativus), and strawberry (Fragaria × ananassa) were used as specimens to clarify the effect of the discharge treatment on edible parts of the plants. The specimens were cultivated in pots filled with artificial soil, which included chicken manure charcoal. Distilled water was sprayed on the artificial soil and drained through a hole in the pots to a water storage tank. The water was circulated from the water storage tank to the cultivation pots after 15 or 30 min discharge treatment on alternate days. A magnetic compression-type pulsed power generator was used to produce the bubble discharge with a repetition rate of 250 pps. The plant height in the growth phase and the dry weight of the harvested plants were improved markedly by the discharge treatment in water. The soil and plant analyzer development (SPAD) value of the plants also improved in the growth phase of the plants. The concentration of nitrate nitrogen, which mainly contributed to the improvement of the growth rate, in the water increased with the discharge treatment. The Brix value of edible parts of Fragaria × ananassa increased with the discharge treatment. The inactivation of bacteria in the water was also confirmed with the discharge treatment.

  2. Ethylene synthesis and sensitivity in crop plants

    NASA Technical Reports Server (NTRS)

    Klassen, Stephen P.; Bugbee, Bruce

    2004-01-01

    Closed and semi-closed plant growth chambers have long been used in studies of plant and crop physiology. These studies include the measurement of photosynthesis and transpiration via photosynthetic gas exchange. Unfortunately, other gaseous products of plant metabolism can accumulate in these chambers and cause artifacts in the measurements. The most important of these gaseous byproducts is the plant hormone ethylene (C2H4). In spite of hundreds of manuscripts on ethylene, we still have a limited understanding of the synthesis rates throughout the plant life cycle. We also have a poor understanding of the sensitivity of intact, rapidly growing plants to ethylene. We know ethylene synthesis and sensitivity are influenced by both biotic and abiotic stresses, but such whole plant responses have not been accurately quantified. Here we present an overview of basic studies on ethylene synthesis and sensitivity.

  3. A study on the optimal hydraulic loading rate and plant ratios in recirculation aquaponic system

    Microsoft Academic Search

    Azizah Endut; A. Jusoh; N. Ali; W. B. Wan Nik; A. Hassan

    2010-01-01

    The growths of the African catfish (Clarias gariepinus) and water spinach (Ipomoea aquatica) were evaluated in recirculation aquaponic system (RAS). Fish production performance, plant growth and nutrient removal were measured and their dependence on hydraulic loading rate (HLR) was assessed. Fish production did not differ significantly between hydraulic loading rates. In contrast to the fish production, the water spinach yield

  4. Rates of molecular evolution and diversification in plants: chloroplast substitution rates correlate with species-richness in the Proteaceae

    PubMed Central

    2013-01-01

    Background Many factors have been identified as correlates of the rate of molecular evolution, such as body size and generation length. Analysis of many molecular phylogenies has also revealed correlations between substitution rates and clade size, suggesting a link between rates of molecular evolution and the process of diversification. However, it is not known whether this relationship applies to all lineages and all sequences. Here, in order to investigate how widespread this phenomenon is, we investigate patterns of substitution in chloroplast genomes of the diverse angiosperm family Proteaceae. We used DNA sequences from six chloroplast genes (6278bp alignment with 62 taxa) to test for a correlation between diversification and the rate of substitutions. Results Using phylogenetically-independent sister pairs, we show that species-rich lineages of Proteaceae tend to have significantly higher chloroplast substitution rates, for both synonymous and non-synonymous substitutions. Conclusions We show that the rate of molecular evolution in chloroplast genomes is correlated with net diversification rates in this large plant family. We discuss the possible causes of this relationship, including molecular evolution driving diversification, speciation increasing the rate of substitutions, or a third factor causing an indirect link between molecular and diversification rates. The link between the synonymous substitution rate and clade size is consistent with a role for the mutation rate of chloroplasts driving the speed of reproductive isolation. We find no significant differences in the ratio of non-synonymous to synonymous substitutions between lineages differing in net diversification rate, therefore we detect no signal of population size changes or alteration in selection pressures that might be causing this relationship. PMID:23497266

  5. Growth rates of rhizosphere microorganisms depend on competitive abilities of plants for nitrogen

    NASA Astrophysics Data System (ADS)

    Blagodatskaya, Evgenia; Littschwager, Johanna; Lauerer, Marianna; Kuzyakov, Yakov

    2010-05-01

    Rhizosphere - one of the most important ‘hot spots' in soil - is characterized not only by accelerated turnover of microbial biomass and nutrients but also by strong intra- and inter-specific competition. Intra-specific competition occurs between individual plants of the same species, while inter-specific competition can occur both at population level (plant species-specific, microbial species-specific interactions) and at community level (plant - microbial interactions). Such plant - microbial interactions are mainly governed by competition for available N sources, since N is one of the main growth limiting nutrients in natural ecosystems. Functional structure and activity of microbial community in rhizosphere is not uniform and is dependent on quantity and quality of root exudates which are plant specific. It is still unclear how microbial growth and turnover in the rhizosphere are dependent on the features and competitive abilities of plants for N. Depending on C and N availability, acceleration and even retardation of microbial activity and carbon mineralization can be expected in the rhizosphere of plants with high competitive abilities for N. We hypothesized slower microbial growth rates in the rhizosphere of plants with smaller roots, as they usually produce less exudates compared to plants with small shoot-to-root ratio. As the first hypothesis is based solely on C availability, we also expected the greater effect of N availability on microbial growth in rhizosphere of plants with smaller root mass. These hypothesis were tested for two plant species of strawberry: Fragaria vesca L. (native species), and Duchesnea indica (Andrews) Focke (an invasive plant in central Europe) growing in intraspecific and interspecific competition. Microbial biomass and the kinetic parameters of microbial growth in the rhizosphere were estimated by dynamics of CO2 emission from the soil amended with glucose and nutrients. Specific growth rate (µ) of soil microorganisms was estimated by fitting the parameters of the equation: CO2(t) = A + B × exp(µ×t), to the measured CO2 production rate (CO2(t)) after glucose addition, where A is the initial respiration rate uncoupled from ATP production, B the initial rate of the growing fraction of total respiration coupled with ATP generation and cell growth, and t time. Our study revealed the linkage between growth strategies of rhizosphere microorganisms and different adaptation strategies of F. vesca and D. indica to N limitation. Plant - strong competitor for N (D. indica) did not change root mass under N limitation causing the deficit of N in the rhizosphere and altering the structure of rhizosphere microbial community. Benefiting of slow growing microorganisms with K-strategy under N limiting conditions was indicated by strong decrease in specific microbial growth rates in the rhizosphere of D. indica. Root mass of the plant with weak competitive abilities for N (F. vesca) increased under lack of N to compensate the lack of nutrients. The increase in root mass and possible increase in amount of root exudates coincided with no structural changes in microbial community in rhizosphere of F. vesca. By intraspecific competition at low N level a 2.4-fold slower microbial specific growth rates were observed under D. indica (0.09 h-1) characterized by smaller root biomass and lower N content in roots compared with F. vesca. The generation time of actively growing microbial biomass was for the 6 hours longer in rhizosphere of D. indica than under F. vesca (10.7 to 4.6 h, respectively). Thus, under N limitation the strong competition for N between plant and microorganisms decreased microbial growth rates and carbon turnover in rhizosphere. By interspecific competition of both plants at low N level, microbial growth rates were similar to those for D. indica indicating that plant with stronger competitive abilities for N controls microbial community in the rhizosphere. At high N availability the root biomass did not differ significantly between both plants. This resulted in similar microbial growt

  6. Parasitic plants have increased rates of molecular evolution across all three genomes

    PubMed Central

    2013-01-01

    Background Theoretical models and experimental evidence suggest that rates of molecular evolution could be raised in parasitic organisms compared to non-parasitic taxa. Parasitic plants provide an ideal test for these predictions, as there are at least a dozen independent origins of the parasitic lifestyle in angiosperms. Studies of a number of parasitic plant lineages have suggested faster rates of molecular evolution, but the results of some studies have been mixed. Comparative analysis of all parasitic plant lineages, including sequences from all three genomes, is needed to examine the generality of the relationship between rates of molecular evolution and parasitism in plants. Results We analysed DNA sequence data from the mitochondrial, nuclear and chloroplast genomes for 12 independent evolutionary origins of parasitism in angiosperms. We demonstrated that parasitic lineages have a faster rate of molecular evolution than their non-parasitic relatives in sequences for all three genomes, for both synonymous and nonsynonymous substitutions. Conclusions Our results prove that raised rates of molecular evolution are a general feature of parasitic plants, not confined to a few taxa or specific genes. We discuss possible causes for this relationship, including increased positive selection associated with host-parasite arms races, relaxed selection, reduced population size or repeated bottlenecks, increased mutation rates, and indirect causal links with generation time and body size. We find no evidence that faster rates are due to smaller effective populations sizes or changes in selection pressure. Instead, our results suggest that parasitic plants have a higher mutation rate than their close non-parasitic relatives. This may be due to a direct connection, where some aspect of the parasitic lifestyle drives the evolution of raised mutation rates. Alternatively, this pattern may be driven by an indirect connection between rates and parasitism: for example, parasitic plants tend to be smaller than their non-parasitic relatives, which may result in more cell generations per year, thus a higher rate of mutations arising from DNA copy errors per unit time. Demonstration that adoption of a parasitic lifestyle influences the rate of genomic evolution is relevant to attempts to infer molecular phylogenies of parasitic plants and to estimate their evolutionary divergence times using sequence data. PMID:23782527

  7. Impact of plant shoot architecture on leaf cooling: a coupled heat and mass transfer model

    PubMed Central

    Bridge, L. J.; Franklin, K. A.; Homer, M. E.

    2013-01-01

    Plants display a range of striking architectural adaptations when grown at elevated temperatures. In the model plant Arabidopsis thaliana, these include elongation of petioles, and increased petiole and leaf angles from the soil surface. The potential physiological significance of these architectural changes remains speculative. We address this issue computationally by formulating a mathematical model and performing numerical simulations, testing the hypothesis that elongated and elevated plant configurations may reflect a leaf-cooling strategy. This sets in place a new basic model of plant water use and interaction with the surrounding air, which couples heat and mass transfer within a plant to water vapour diffusion in the air, using a transpiration term that depends on saturation, temperature and vapour concentration. A two-dimensional, multi-petiole shoot geometry is considered, with added leaf-blade shape detail. Our simulations show that increased petiole length and angle generally result in enhanced transpiration rates and reduced leaf temperatures in well-watered conditions. Furthermore, our computations also reveal plant configurations for which elongation may result in decreased transpiration rate owing to decreased leaf liquid saturation. We offer further qualitative and quantitative insights into the role of architectural parameters as key determinants of leaf-cooling capacity. PMID:23720538

  8. Root controls on water redistribution and carbon uptake in the soil-plant system under current and future climate

    NASA Astrophysics Data System (ADS)

    Volpe, V.; Marani, M.; Albertson, J. D.; Katul, G.

    2013-10-01

    Understanding photosynthesis and plant water management as a coupled process remains an open scientific problem. Current eco-hydrologic models characteristically describe plant photosynthetic and hydraulic processes through ad hoc empirical parameterizations with no explicit accounting for the main pathways over which carbon and water uptake interact. Here, a soil-plant-atmosphere continuum model is proposed that mechanistically couples photosynthesis and transpiration rates, including the main leaf physiological controls exerted by stomata. The proposed approach links the soil-to-leaf hydraulic transport to stomatal regulation, and closes the coupled photosynthesis-transpiration problem by maximizing leaf carbon gain subject to a water loss constraint. The approach is evaluated against field data from a grass site and is shown to reproduce the main features of soil moisture dynamics and hydraulic redistribution. In particular, it is shown that the differential soil drying produced by diurnal root water uptake drives a significant upward redistribution of moisture both through a conventional Darcian flow and through the root system, consistent with observations. In a numerical soil drying experiment, it is demonstrated that more than 50% of diurnal transpiration is supplied by nocturnal upward water redistribution, and some 12% is provided directly through root hydraulic redistribution. For a prescribed leaf area density, the model is then used to diagnose how elevated atmospheric CO2 concentration and increased air temperature jointly impact soil moisture, transpiration, photosynthesis, and whole-plant water use efficiency, along with compensatory mechanisms such as hydraulic lift using several canonical forms of root-density distribution.

  9. Design of Transpiration Cooled Thermal Protection Systems

    NASA Technical Reports Server (NTRS)

    Callens, E. Eugene, Jr.; Vinet, Robert F.

    1999-01-01

    This study explored three approaches for the utilization of transpiration cooling in thermal protection systems. One model uses an impermeable wall with boiling water heat transfer at the backface (Model I). A second model uses a permeable wall with a boiling water backface and additional heat transfer to the water vapor as it flows in channels toward the exposed surface (Model II). The third model also uses a permeable wall, but maintains a boiling condition at the exposed surface of the material (Model III). The governing equations for the models were developed in non-dimensional form and a comprehensive parametric investigation of the effects of the independent variables on the important dependent variables was performed. In addition, detailed analyses were performed for selected materials to evaluate the practical limitations of the results of the parametric study.

  10. Transpiration from a Cryptomeria japonica plantation, part 1: aerodynamic control of transpiration

    NASA Astrophysics Data System (ADS)

    Komatsu, Hikaru; Kang, Yihuei; Kume, Tomonori; Yoshifuji, Natsuko; Hotta, Norifumi

    2006-04-01

    To our knowledge, no one has examined the canopy conductance of a Cryptomeria japonica plantation, although such forests are very common in Japan. We plan to examine the canopy conductance of a Cryptomeria japonica plantation (canopy height 8 m) based on 1-year sap-flow data using the simplified Penman-Monteith equation. This study examines the effect of the aerodynamic control of transpiration before calculating canopy conductance using the simplified Penman-Monteith equation, because the equation assumes that the effect of aerodynamic control is negligible. To examine the effect of aerodynamic control, we examined the dependency of the relationship between the vapour pressure deficit (VPD) and transpiration on wind speed, when solar radiation, air temperature, and soil water content do not limit transpiration greatly. The relationship between VPD and the heat pulse velocity measured 11 m above the ground was dependent on wind speed only when the wind speed was <0.7 m s-1. This suggests that the effect of aerodynamic control was negligible when the wind speed was 0.7 m s-1, but that the effect was not negligible when the wind speed was <0.7 m s-1. Therefore, we should use data from when the wind speed was 0.7 m s-1 for calculating canopy conductance Gc, based on the simplified Penman-Monteith equation. Although this criterion is site specific, the methods used to develop it are applicable to other sites.

  11. Transpiration sensitivity of urban trees in a semi-arid climate is constrained by xylem vulnerability to cavitation.

    PubMed

    Litvak, Elizaveta; McCarthy, Heather R; Pataki, Diane E

    2012-04-01

    Establishing quantitative links between plant hydraulic properties and the response of transpiration to environmental factors such as atmospheric vapor pressure deficit (D) is essential for improving our ability to understand plant water relations across a wide range of species and environmental conditions. We studied stomatal responses to D in irrigated trees in the urban landscape of Los Angeles, California. We found a strong linear relationship between the sensitivity of tree-level transpiration estimated from sap flux (m(T); slope of the relationship between tree transpiration and ln D) and transpiration at D=1 kPa (E(Tref)) that was similar to previous surveys of stomatal behavior in natural environments. In addition, m(T) was significantly related to vulnerability to cavitation of branches (P(50)). While m(T) did not appear to differ between ring- and diffuse-porous species, the relationship between m(T) and P(50) was distinct by wood anatomy. Therefore, our study confirms systematic differences in water relations in ring- versus diffuse-porous species, but these differences appear to be more strongly related to the relationship between stomatal sensitivity to D and vulnerability to cavitation rather than to stomatal sensitivity per se. PMID:22447283

  12. A study on the optimal hydraulic loading rate and plant ratios in recirculation aquaponic system.

    PubMed

    Endut, Azizah; Jusoh, A; Ali, N; Wan Nik, W B; Hassan, A

    2010-03-01

    The growths of the African catfish (Clarias gariepinus) and water spinach (Ipomoea aquatica) were evaluated in recirculation aquaponic system (RAS). Fish production performance, plant growth and nutrient removal were measured and their dependence on hydraulic loading rate (HLR) was assessed. Fish production did not differ significantly between hydraulic loading rates. In contrast to the fish production, the water spinach yield was significantly higher in the lower hydraulic loading rate. Fish production, plant growth and percentage nutrient removal were highest at hydraulic loading rate of 1.28 m/day. The ratio of fish to plant production has been calculated to balance nutrient generation from fish with nutrient removal by plants and the optimum ratio was 15-42 gram of fish feed/m(2) of plant growing area. Each unit in RAS was evaluated in terms of oxygen demand. Using specified feeding regime, mass balance equations were applied to quantify the waste discharges from rearing tanks and treatment units. The waste discharged was found to be strongly dependent on hydraulic loading rate. PMID:19819130

  13. Chilling rate effects on pork loin tenderness in commercial processing plants.

    PubMed

    Shackelford, S D; King, D A; Wheeler, T L

    2012-08-01

    The present experiment was conducted to provide a large-scale objective comparison of pork LM tenderness and other meat quality traits among packing plants that differ in stunning method and carcass chilling rate. For each of 2 replicates, pigs were sourced from a single barn of a commercial finishing operation that fed pigs from a single terminal crossbred line. On each day, 3 trucks were loaded, with each of those trucks delivering the pigs to a different plant. Plant A used CO(2) stunning and conventional spray chilling; Plant B used CO(2) stunning and blast chilling; and Plant C used electrical stunning and blast chilling. The boneless, vacuum-packaged loin was obtained from the left side of each carcass (n = 597; 100 · plant(-1) · replicate(-1)). As designed, HCW, LM depth, and LM intramuscular fat percentage did not differ among plants (P > 0.05). By 1.67 h postmortem (1 h after the carcasses exited the harvest floor), the average deep LM temperature was >10°C warmer for Plant A than Plants B and C (32.1°C, 21.6°C, and 19.3°C, for Plants A, B, and C, respectively) and deep LM temperature continued to be >10°C warmer for Plant A until 4.17 h or 6.33 h postmortem than for Plants C and B, respectively. Both plants that used blast chilling produced loins with greater LM slice shear force at 15 d postmortem than did the plant that used conventional spray chilling (P < 0.0001). The frequency of loins with excessively high (>25 kg) LM slice shear force values was greater for Plant B than Plant A (14.7% vs. 1%; P < 0.01). Among all the traits studied, including visual and instrumental evaluations of LM color, ultimate pH, marbling score, and lean color stability, the only other difference between Plants A and B was that purge loss during 13 d (from d 1 to 14) of vacuum-packaged storage was greater for Plant B (P < 0.05). That is, with this sample of pigs and CO(2) stunning, no loin quality advantages were detected for blast chilling. Regardless of chilling method, CO(2) stunning resulted in darker LM lean color and greater LM water-holding capacity than did electrical stunning (P < 0.05). This research shows that differences in chilling systems among pork packing plants can have a strong influence on loin chop tenderness. PMID:22307481

  14. Grazing-induced losses of biodiversity affect the transpiration of an arid ecosystem.

    PubMed

    Verón, Santiago R; Paruelo, José M; Oesterheld, Martín

    2011-02-01

    Degradation processes often lead to species loss. Such losses would impact on ecosystem functioning depending on the extinction order and the functional and structural aspects of species. For the Patagonian arid steppe, we used a simulation model to study the effects of species loss on the rate and variability (i.e. stability) of transpiration as a key attribute of ecosystem functioning. We addressed (1) the differences between the overgrazing extinction order and other potential orders, and (2) the role of biomass abundance, biomass distribution, and functional diversity on the effect of species loss due to overgrazing. We considered a community composed of ten species which were assigned an order of extinction due to overgrazing based on their preference by livestock. We performed four model simulations to test for overgrazing effects through different combinations of species loss, and reductions of biomass and functional diversity. In general, transpiration rate and variability were positively associated to species richness and remained fairly constant until half the species were lost by overgrazing. The extinction order by overgrazing was the most conservative of all possible orders. The amount of biomass was more important than functional diversity in accounting for the impacts of species richness on transpiration. Our results suggest that, to prevent Patagonian steppes from shifting to stable, low-production systems (by overgrazing), maintaining community biomass is more important than preserving species richness or species functional diversity. PMID:20865282

  15. An experimental study on the efficiency of transpiration cooling in laminar and turbulent hypersonic flows

    NASA Astrophysics Data System (ADS)

    Gülhan, A.; Braun, S.

    2011-03-01

    An experimental study on the efficiency of transpiration cooling in hypersonic laminar and turbulent flow regimes is carried out in the Hypersonic Windtunnel Cologne with a focus on the aerothermal problems downstream of the cooled model part. The model is made of a material of low thermal conductivity (PEEK) with an integrated probe of a porous material. The experimental setup allows the direct comparison of the thermal behavior of transpiration cooling to a well-defined and radiatively cooled reference surface. Experiments are performed at Mach number of 6 and two different Reynolds numbers. Air, argon and helium are used as coolants at various flow rates, in order to identify the influence of coolant medium on cooling efficiency. The cooling efficiency of air and argon is comparable. Helium provides significantly higher cooling efficiency at the same blowing ratio, i.e. same coolant mass flow rate. The experimental data shows that the efficiency of the transpiration cooling in turbulent flows is much lower than in laminar flow.

  16. Plant Disease / October 2001 1113 Effect of Host Plant Resistance and Reduced Rates and Frequencies

    E-print Network

    Douches, David S.

    , Michigan State University, East Lansing 48824 Late blight of potato (Solanum tubero- sum, L.) caused (12). Unchecked, P. infestans can rapidly defoliate plants in the field and can infect potato tubers blight infection in potato. There are currently no late blight resistant potato cultivars that meet

  17. The importance of micrometeorological variations for photosynthesis and transpiration in a boreal coniferous forest

    NASA Astrophysics Data System (ADS)

    Schurgers, G.; Lagergren, F.; Mölder, M.; Lindroth, A.

    2015-01-01

    Plant canopies affect the canopy micrometeorology, and thereby alter canopy exchange processes. For the simulation of these exchange processes on a regional or global scale, large-scale vegetation models often assume homogeneous environmental conditions within the canopy. In this study, we address the importance of vertical variations in light, temperature, CO2 concentration and humidity within the canopy for fluxes of photosynthesis and transpiration of a boreal coniferous forest in central Sweden. A leaf-level photosynthesis-stomatal conductance model was used for aggregating these processes to canopy level while applying the within-canopy distributions of these driving variables. The simulation model showed good agreement with eddy covariance-derived gross primary production (GPP) estimates on daily and annual timescales, and showed a reasonable agreement between transpiration and observed H2O fluxes, where discrepancies are largely attributable to a lack of forest floor evaporation in the model. Simulations in which vertical heterogeneity was artificially suppressed revealed that the vertical distribution of light is the driver of vertical heterogeneity. Despite large differences between above-canopy and within-canopy humidity, and despite large gradients in CO2 concentration during early morning hours after nights with stable conditions, neither humidity nor CO2 played an important role for vertical heterogeneity of photosynthesis and transpiration.

  18. The importance of micrometeorological variations for photosynthesis and transpiration in a boreal coniferous forest

    NASA Astrophysics Data System (ADS)

    Schurgers, G.; Lagergren, F.; Mölder, M.; Lindroth, A.

    2014-08-01

    Plant canopies affect the canopy micrometeorology, and thereby alter canopy exchange processes. For the simulation of these exchange processes on a regional or global scale, large-scale vegetation models often assume homogeneous environmental conditions within the canopy. In this study, we address the importance of vertical variations in light, temperature, CO2 concentration and humidity within the canopy for photosynthesis and transpiration of a boreal coniferous forest in central Sweden. A leaf-level photosynthesis-stomatal conductance model was used for aggregating these processes to canopy level while applying the within-canopy distributions of these driving variables. The simulation model showed good agreement with eddy covariance-derived gross primary production (GPP) estimates on daily and annual timescales, and showed a reasonable agreement between transpiration and observed H2O fluxes, where discrepancies are largely attributable to a lack of forest floor evaporation in the model. Simulations in which vertical heterogeneity was artificially suppressed revealed that the vertical distribution of light is the driver of vertical heterogeneity. Despite large differences between above-canopy and within canopy humidity, and despite large gradients in CO2 concentration during early morning hours after nights with stable conditions, neither humidity nor CO2 played an important role for vertical heterogeneity of photosynthesis and transpiration.

  19. Rate variation in parasitic plants: correlated and uncorrelated patterns among plastid genes of different function

    PubMed Central

    Young, Nelson D; dePamphilis, Claude W

    2005-01-01

    Background The analysis of synonymous and nonsynonymous rates of DNA change can help in the choice among competing explanations for rate variation, such as differences in constraint, mutation rate, or the strength of genetic drift. Nonphotosynthetic plants of the Orobanchaceae have increased rates of DNA change. In this study 38 taxa of Orobanchaceae and relatives were used and 3 plastid genes were sequenced for each taxon. Results Phylogenetic reconstructions of relative rates of sequence evolution for three plastid genes (rbcL, matK and rps2) show significant rate heterogeneity among lineages and among genes. Many of the non-photosynthetic plants have increases in both synonymous and nonsynonymous rates, indicating that both (1) selection is relaxed, and (2) there has been a change in the rate at which mutations are entering the population in these species. However, rate increases are not always immediate upon loss of photosynthesis. Overall there is a poor correlation of synonymous and nonsynonymous rates. There is, however, a strong correlation of synonymous rates across the 3 genes studied and the lineage-speccific pattern for each gene is strikingly similar. This indicates that the causes of synonymous rate variation are affecting the whole plastid genome in a similar way. There is a weaker correlation across genes for nonsynonymous rates. Here the picture is more complex, as could be expected if there are many causes of variation, differing from taxon to taxon and gene to gene. Conclusions The distinctive pattern of rate increases in Orobanchaceae has at least two causes. It is clear that there is a relaxation of constraint in many (though not all) non-photosynthetic lineages. However, there is also some force affecting synonymous sites as well. At this point, it is not possible to tell whether it is generation time, speciation rate, mutation rate, DNA repair efficiency or some combination of these factors. PMID:15713237

  20. Initiating Event Rates at U.S. Nuclear Power Plants 1988–2013

    SciTech Connect

    John A. Schroeder; Gordon R. Bower

    2014-02-01

    Analyzing initiating event rates is important because it indicates performance among plants and also provides inputs to several U.S. Nuclear Regulatory Commission (NRC) risk-informed regulatory activities. This report presents an analysis of initiating event frequencies at U.S. commercial nuclear power plants since each plant’s low-power license date. The evaluation is based on the operating experience from fiscal year 1988 through 2013 as reported in licensee event reports. Engineers with nuclear power plant experience staff reviewed each event report since the last update to this report for the presence of valid scrams or reactor trips at power. To be included in the study, an event had to meet all of the following criteria: includes an unplanned reactor trip (not a scheduled reactor trip on the daily operations schedule), sequence of events starts when reactor is critical and at or above the point of adding heat, occurs at a U.S. commercial nuclear power plant (excluding Fort St. Vrain and LaCrosse), and is reported by a licensee event report. This report displays occurrence rates (baseline frequencies) for the categories of initiating events that contribute to the NRC’s Industry Trends Program. Sixteen initiating event groupings are trended and displayed. Initiators are plotted separately for initiating events with different occurrence rates for boiling water reactors and pressurized water reactors. p-values are given for the possible presence of a trend over the most recent 10 years.

  1. Evaluating heat rate modifications with the EPRI plant modification operating savings (PMOS) model

    SciTech Connect

    Fahd, G.; Jabbour, S.J. [Decision Focus Incorporated, Mountain View, CA (United States); O`Connor, D. [Electric Power Research Institute, Palo Alto, CA (United States)

    1995-06-01

    The Electric power Research Institute (EPRI) developed the Plant Modification Operating Savings Model (PMOS) to overcome the shortcomings of conventional planning tools in capturing the value of small-scale plant modifications. PMOS focuses on one single plant and determines the value of a modification at that plant to the system, using readily available cost and performance data. PMOS provides decision-makers with accurate results to help select the projects with highest value to the system. it is a powerful, yet easy-to-use, computer model that is a useful addition to the utility planning toolkit. This paper discusses the use of PMOS for evaluation heat rate improvements of power plants, considers utility applications, and describes the model`s methodology, required data, operation, results, and applications.

  2. Cancer rates after the Three Mile Island nuclear accident and proximity of residence to the plant

    SciTech Connect

    Hatch, M.C.; Wallenstein, S.; Beyea, J.; Nieves, J.W.; Susser, M. (Columbia Univ., New York, NY (USA))

    1991-06-01

    In the light of a possible link between stress and cancer promotion or progression, and of previously reported distress in residents near the Three Mile Island (TMI) nuclear power plant, we attempted to evaluate the impact of the March 1979 accident on community cancer rates. Proximity of residence to the plant, which related to distress in previous studies, was taken as a possible indicator of accident stress; the postaccident pattern in cancer rates was examined in 69 'study tracts' within a 10-mile radius of TMI, in relation to residential proximity. A modest association was found between postaccident cancer rates and proximity (OR = 1.4; 95% CI = 1.3, 1.6). After adjusting for a gradient in cancer risk prior to the accident, the odds ratio contrasting those closest to the plant with those living farther out was 1.2 (95% CI = 1.0, 1.4). A postaccident increase in cancer rates near the Three Mile Island plant was notable in 1982, persisted for another year, and then declined. Radiation emissions, as modeled mathematically, did not account for the observed increase. Interpretation in terms of accident stress is limited by the lack of an individual measure of stress and by uncertainty about whether stress has a biological effect on cancer in humans. An alternative mechanism for the cancer increase near the plant is through changes in care-seeking and diagnostic practice arising from postaccident concern.

  3. The influence of plant spacing and rates of nitrogen on the morphology of two rice varieties 

    E-print Network

    Stansel, James Wilbert

    1959-01-01

    LIBAARY A A N COLLE66 OF TEXAS THE INFLUENCE OF PLANT SPACING AND RATES OF NITROGEN ON THE MORPHOLOGY OF TWO RICE VARIETIES A Thesis Ey James Wilbert Stansel ~ ~ ~ Subaitted to the Graduate School of the Agricultural and Mechanical... College of Texas in partial fulfillaent of the requirenents for the degree of MASTER OF SCIENCE January 1959 Ma)or Sub)ect& Agronomy THE INFLUENCE OF PLANT SPACING AND RATES OF NITROGEN ON THE MORPHOLOGY OP TWO RICE VARIETIES A Thesis By James...

  4. ????????????????????????????? (??2)??????????? Research on Improving Air-conditioners ' Energy Efficiency Using Hydroponic Roof Planting (Part 2) Prediction for Air-conditioners ' Efficiency Improvement

    Microsoft Academic Search

    Fulin WANG; Harunori YOSHIDA; Michiko YAMASHITA

    Synopsis This part describes the modeling for calculating leaf transpiration rate, air temperature difference cooled down by roof plant, energy consumption of air-conditioners. The models are validated using the measured data. Finally these models are used to check how much air-conditioners' energy efficiency can be improved using hydroponic-cultivated plant to shade solar radiation and cool down air temperature by its

  5. HTRATE; Heat-Rate Improvement Obtained by Retubing Power-Plant Condenser Enhanced Tubes

    SciTech Connect

    Rabas, T.J. [Argonne National Lab., IL (United States)

    1990-06-01

    A utility will only retube a condenser with enhanced tubes if the incremental cost of the enhanced tubes can be offset with reduced fuel costs. The reduced fuel cost is obtained for some units because of the higher heat-transfer coefficient of enhanced tubes. They lead to improved condenser performance measured by a lower condenser pressure and therefore a more efficient power plant. However, the higher haet-transfer coefficients do not always guarantee that enhanced tubes will be more cost effective. Other issues must be considered such as the cooling-water flow reduction due to the increased pressure drop, the low-pressure turbine heat-rate variation with backpressure, and the cooling-water pump and system characteristics. These and other parameters must be considered to calculate the efficiency improvement of the power plant as commonly measured by the quantity known as the heat rate. Knowing the heat-rate improvement, the fuel cost, and the incremental increase of the enhanced tubes from the supplier, the payback time can be determined. This program calculates the heat-rate improvement that can be obtained by retubing a power plant condenser with enhanced tubes of a particular type called Korodense LPD made by Wolverine Tube, Inc. The fuel savings are easily established knowing the heat-rate improvement. All electrical utilities are potential users because a condenser is used as the heat sink for every power plant.

  6. Numerical Simulation Study on Transpired Solar Air Collector 

    E-print Network

    Wang, C.; Guan, Z.; Zhao, X.; Wang, D.

    2006-01-01

    ICEBO2006, Shenzhen, China Re newable Energy Resources and a Greener Future Vol.VIII-3-4 Numerical Simulation Study on Transpired Solar Air Collector Chongjie Wang Zhenzhong Guan Xueyi Zhao Delin Wang Professor...

  7. Effect, uptake and disposition of nitrobenzene in several terrestrial plants

    SciTech Connect

    McFarlane, C.; Pfleeger, T.; Fletcher, J.

    1990-01-01

    Eight species of plants were exposed to nitrobenzene in a hydroponic solution. Four species experienced no depression of either transpiration or photosynthetic rates, while one was rapidly killed and the other three were temporarily affected but recovered from the treatment. Uptake of nitrobenzene was passive and was shown to be proportional to the rate of water flux in each species. The transpiration stream concentration factor (TSCF) was 0.72. The root concentration factor (RCF) was variable between the species and was higher than expected, presumably due to deposits of insoluble metabolic products. All of the species examined displayed a capacity to chemically alter nonpolar nitrobenzene into both polar and insoluble products. Volatilization of nitrobenzene from the leaves was a major route of chemical loss.

  8. Glutathione and transpiration as key factors conditioning oxidative stress in Arabidopsis thaliana exposed to uranium.

    PubMed

    Aranjuelo, Iker; Doustaly, Fany; Cela, Jana; Porcel, Rosa; Müller, Maren; Aroca, Ricardo; Munné-Bosch, Sergi; Bourguignon, Jacques

    2014-04-01

    Although oxidative stress has been previously described in plants exposed to uranium (U), some uncertainty remains about the role of glutathione and tocopherol availability in the different responsiveness of plants to photo-oxidative damage. Moreover, in most cases, little consideration is given to the role of water transport in shoot heavy metal accumulation. Here, we investigated the effect of uranyl nitrate exposure (50 ?M) on PSII and parameters involved in water transport (leaf transpiration and aquaporin gene expression) of Arabidopsis wild type (WT) and mutant plants that are deficient in tocopherol (vte1: null ?/?-tocopherol and vte4: null ?-tocopherol) and glutathione biosynthesis (high content: cad1.3 and low content: cad2.1). We show how U exposure induced photosynthetic inhibition that entailed an electron sink/source imbalance that caused PSII photoinhibition in the mutants. The WT was the only line where U did not damage PSII. The increase in energy thermal dissipation observed in all the plants exposed to U did not avoid photo-oxidative damage of mutants. The maintenance of control of glutathione and malondialdehyde contents probed to be target points for the overcoming of photoinhibition in the WT. The relationship between leaf U content and leaf transpiration confirmed the relevance of water transport in heavy metals partitioning and accumulation in leaves, with the consequent implication of susceptibility to oxidative stress. PMID:24389672

  9. Transpiration during life cycle in controlled wheat growth

    NASA Technical Reports Server (NTRS)

    Volk, Tyler; Rummel, John D.

    1990-01-01

    A previously developed model of wheat growth, designed for convenient incorporation into system level models of advanced space life support systems is described. The model is applied to data from an experiment that grew wheat under controlled conditions and measured fresh biomass and cumulated transpiration as a function of time. The adequacy of modeling the transpiration as proportional to the inedible biomass and an age factor that varies during the life cycle are discussed.

  10. Modeling the crop transpiration using an optimality-based approach

    Microsoft Academic Search

    HuiMin Lei; DaWen Yang; Stanislaus J. Schymanski; Murugesu Sivapalan

    2008-01-01

    Evapotranspiration constitutes more than 80% of the long-term water balance in Northern China. In this area, crop transpiration\\u000a due to large areas of agriculture and irrigation is responsible for the majority of evapotranspiration. A model for crop transpiration\\u000a is therefore essential for estimating the agricultural water consumption and understanding its feedback to the environment.\\u000a However, most existing hydrological models usually

  11. Effects of row spacing, seed rate and maturity group on late planted soybean under irrigated and dryland

    E-print Network

    Balasundaram, Balabhaskar "Baski"

    Effects of row spacing, seed rate and maturity group on late planted soybean under irrigated, seeding rate, and maturity group (MG) for late planted soybean under irrigated and dryland conditions with three replications and three variables (MG, row spacing, and seeding rate). Table 1 shows all different

  12. Simulation of thermal transpiration flow using a high-order moment method

    NASA Astrophysics Data System (ADS)

    Sheng, Qiang; Tang, Gui-Hua; Gu, Xiao-Jun; Emerson, David R.; Zhang, Yong-Hao

    2014-04-01

    Nonequilibrium thermal transpiration flow is numerically analyzed by an extended thermodynamic approach, a high-order moment method. The captured velocity profiles of temperature-driven flow in a parallel microchannel and in a micro-chamber are compared with available kinetic data or direct simulation Monte Carlo (DSMC) results. The advantages of the high-order moment method are shown as a combination of more accuracy than the Navier-Stokes-Fourier (NSF) equations and less computation cost than the DSMC method. In addition, the high-order moment method is also employed to simulate the thermal transpiration flow in complex geometries in two types of Knudsen pumps. One is based on micro-mechanized channels, where the effect of different wall temperature distributions on thermal transpiration flow is studied. The other relies on porous structures, where the variation of flow rate with a changing porosity or pore surface area ratio is investigated. These simulations can help to optimize the design of a real Knudsen pump.

  13. Measurements of transpiration isotopologues and leaf water to assess enrichment models in cotton.

    PubMed

    Song, Xin; Loucos, Karen E; Simonin, Kevin A; Farquhar, Graham D; Barbour, Margaret M

    2015-04-01

    The two-pool and Péclet effect models represent two theories describing mechanistic controls underlying leaf water oxygen isotope composition at the whole-leaf level (?(18) OL ). To test these models, we used a laser spectrometer coupled to a gas-exchange cuvette to make online measurements of ?(18) O of transpiration (?(18) Otrans ) and transpiration rate (E) in 61 cotton (Gossypium hirsutum) leaves. ?(18) Otrans measurements permitted direct calculation of ?(18) O at the sites of evaporation (?(18) Oe ) which, combined with values of ?(18) OL from the same leaves, allowed unbiased estimation of the proportional deviation of enrichment of ?(18) OL from that of ?(18) Oe (f) under both steady-state (SS) and non-steady-state (NSS) conditions. Among all leaves measured, f expressed relative to both ?(18) O of transpired water (ftrans ) and source water (fsw ) remained relatively constant with a mean ± SD of 0.11 ± 0.05 and 0.13 ± 0.05, respectively, regardless of variation in E spanning 0.8-9.1 mmol m(-2)  s(-1) . Neither ftrans nor fsw exhibited a significant difference between the SS and NSS leaves at the P < 0.05 level. Our results suggest that the simpler two-pool model is adequate for predicting cotton leaf water enrichment at the whole-leaf level. We discuss the implications of adopting a two-pool concept for isotopic applications in ecological studies. PMID:25643590

  14. Physiological studies in young Eucalyptus stands in southern India and their use in estimating forest transpiration

    SciTech Connect

    Roberts, J.M.; Rosier, P.T.W. [Inst. of Hydrology, Wallingford (United Kingdom); Murthy, K.V. [Mysore Paper Mills, Shimoga (India)

    1992-12-31

    Stomatal conductance, leaf water potential and leaf area index were measured in adjacent plantations of Eucalyptus camaldulensis and Eucalyptus tereticornis at Puradal, near Shimoga, Karnataka, southern India. The data were collected in a range of climatic conditions during a two year period immediately following plantation establishment. Physiological differences between the two species were small and confined largely to leaf area index. Stomatal conductance was highest in the post-monsoon period and declined to minimum values immediately prior to the onset of the monsoon, with the lowest conductances observed after the plantations had been established for more than one year. Stomatal conductance, leaf area index and above-canopy meteorological data were combined in a multi-layer transpiration model and used to calculate hourly values of transpiration from the two species. Rates of transpiration up to 6 mm d{sup {minus}1} were estimated for the post-monsoon period but fell to below 1 mm d{sup {minus}1} prior to the monsoon.

  15. Predicting Regional Transpiration at Elevated Atmospheric CO2: Influence of the PBL-Vegetation Interaction.

    NASA Astrophysics Data System (ADS)

    Jacobs, Cor M. J.; de Bruin, Henk A. R.

    1997-12-01

    A coupled planetary boundary layer (PBL)-vegetation model is used to study the influence of the PBL-vegetation interaction and the ambient CO2 concentration on surface resistance rs and regional transpiration E. Vegetation is described using the big-leaf model in which rs is modeled by means of a coupled photosynthesis-resistance model. The PBL part is a one-dimensional, first-order closure model. Nonlocal turbulent transport is accounted for by means of a countergradient correction. The PBL model also describes CO2 fluxes and concentrations, which are driven by photosynthesis of the canopy. A number of sensitivity analyses are presented in which the behavior of rs and E at an atmospheric CO2 concentration representative for the present-day situation is compared to their behavior under an approximately doubled CO2 concentration. The results reveal a positive atmospheric feedback on rs, by which an initial increase of rs, due to changes in ambient CO2 concentration, is magnified. The stomatal humidity response appears to be the key factor here: if rs increases, the air within the canopy dries out, which causes the stomata to close further. The PBL enlarges the effect of this positive feedback loop. The model suggests plants with a C4 photosynthetic pathway to be less sensitive to the humidity-mediated positive feedback than plants with a C3 photosynthetic pathway. Another important aspect of biosphere-atmosphere interaction is the negative feedback of the PBL on transpiration. It is concluded that the interaction between PBL and the vegetation has to be taken into account if transpiration and its changes, due to changing surface characteristics, are to be predicted at the regional scale. This conclusion applies to modeling studies as well as to extrapolation of results from plant physiological research or from small-scale field plots to the regional scale.

  16. Somatic deleterious mutation rate in a woody plant: estimation from phenotypic data

    PubMed Central

    Bobiwash, K; Schultz, S T; Schoen, D J

    2013-01-01

    We conducted controlled crosses in populations of the long-lived clonal shrub, Vaccinium angustifolium (lowbush blueberry) to estimate inbreeding depression and mutation parameters associated with somatic deleterious mutation. Inbreeding depression level was high, with many plants failing to set fruit after self-pollination. We also compared fruit set from autogamous pollinations (pollen collected from within the same inflorescence) with fruit set from geitonogamous pollinations (pollen collected from the same plant but from inflorescences separated by several meters of branch growth). The difference between geitonogamous versus autogamous fitness within single plants is referred to as ‘autogamy depression' (AD). AD can be caused by somatic deleterious mutation. AD was significantly different from zero for fruit set. We developed a maximum-likelihood procedure to estimate somatic mutation parameters from AD, and applied it to geitonogamous and autogamous fruit set data from this experiment. We infer that, on average, approximately three sublethal, partially dominant somatic mutations exist within the crowns of the plants studied. We conclude that somatic mutation in this woody plant results in an overall genomic deleterious mutation rate that exceeds the rate measured to date for annual plants. Some implications of this result for evolutionary biology and agriculture are discussed. PMID:23778990

  17. Response of transpiration to rain pulses for two tree species in a semiarid plantation

    NASA Astrophysics Data System (ADS)

    Chen, Lixin; Zhang, Zhiqiang; Zeppel, Melanie; Liu, Caifeng; Guo, Junting; Zhu, Jinzhao; Zhang, Xuepei; Zhang, Jianjun; Zha, Tonggang

    2014-09-01

    Responses of transpiration ( E c) to rain pulses are presented for two semiarid tree species in a stand of Pinus tabulaeformis and Robinia pseudoacacia. Our objectives are to investigate (1) the environmental control over the stand transpiration after rainfall by analyzing the effect of vapor pressure deficit (VPD), soil water condition, and rainfall on the post-rainfall E c development and recovery rate, and (2) the species responses to rain pulses and implications on vegetation coverage under a changing rainfall regime. Results showed that the sensitivity of canopy conductance ( G c) to VPD varied under different incident radiation and soil water conditions, and the two species exhibited the same hydraulic control (-d G c/dlnVPD to G cref ratio) over transpiration. Strengthened physiological control and low sapwood area of the stand contributed to low E c. VPD after rainfall significantly influenced the magnitude and time series of post-rainfall stand E c. The fluctuation of post-rainfall VPD in comparison with the pre-rainfall influenced the E c recovery. Further, the stand E c was significantly related to monthly rainfall, but the recovery was independent of the rainfall event size. E c enhanced with cumulative soil moisture change (?VWC) within each dry-wet cycle, yet still was limited in large rainfall months. The two species had different response patterns of post-rainfall E c recovery. E c recovery of P. tabulaeformis was influenced by the pre- and post-rainfall VPD differences and the duration of rainless interval. R. pseudoacacia showed a larger immediate post-rainfall E c increase than P. tabulaeformis did. We, therefore, concluded that concentrated rainfall events do not trigger significant increase of transpiration unless large events penetrate the deep soil and the species differences of E c in response to pulses of rain may shape the composition of semiarid woodlands under future rainfall regimes.

  18. Response of transpiration to rain pulses for two tree species in a semiarid plantation.

    PubMed

    Chen, Lixin; Zhang, Zhiqiang; Zeppel, Melanie; Liu, Caifeng; Guo, Junting; Zhu, Jinzhao; Zhang, Xuepei; Zhang, Jianjun; Zha, Tonggang

    2014-09-01

    Responses of transpiration (Ec) to rain pulses are presented for two semiarid tree species in a stand of Pinus tabulaeformis and Robinia pseudoacacia. Our objectives are to investigate (1) the environmental control over the stand transpiration after rainfall by analyzing the effect of vapor pressure deficit (VPD), soil water condition, and rainfall on the post-rainfall Ec development and recovery rate, and (2) the species responses to rain pulses and implications on vegetation coverage under a changing rainfall regime. Results showed that the sensitivity of canopy conductance (Gc) to VPD varied under different incident radiation and soil water conditions, and the two species exhibited the same hydraulic control (-dG c/dlnVPD to Gcref ratio) over transpiration. Strengthened physiological control and low sapwood area of the stand contributed to low Ec. VPD after rainfall significantly influenced the magnitude and time series of post-rainfall stand Ec. The fluctuation of post-rainfall VPD in comparison with the pre-rainfall influenced the Ec recovery. Further, the stand Ec was significantly related to monthly rainfall, but the recovery was independent of the rainfall event size. Ec enhanced with cumulative soil moisture change (?VWC) within each dry-wet cycle, yet still was limited in large rainfall months. The two species had different response patterns of post-rainfall Ec recovery. Ec recovery of P. tabulaeformis was influenced by the pre- and post-rainfall VPD differences and the duration of rainless interval. R. pseudoacacia showed a larger immediate post-rainfall Ec increase than P. tabulaeformis did. We, therefore, concluded that concentrated rainfall events do not trigger significant increase of transpiration unless large events penetrate the deep soil and the species differences of Ec in response to pulses of rain may shape the composition of semiarid woodlands under future rainfall regimes. PMID:24510059

  19. Gas Exchange, Transpiration and Yield of Sweetpotato Grown in a Controlled Environment

    NASA Technical Reports Server (NTRS)

    Barta, Daniel J.; Henderson, Keith E.; Mortley, Desmond G.; Henninger, Donald L.

    2000-01-01

    Sweetpotato was grown to harvest maturity within NASA Johnson Space Center's Variable Pressure Growth Chamber (VPGC) to characterize crop performance for potential use in advanced life support systems as a contributor to food production, air revitalization and resource recovery. Stem cuttings of breeding clone "TU-82-155" were grown hydroponically at a density of 17 plants m(sup -2) using a modified pressure-plate growing system (Patent No. 4860-490, Tuskegee University). Lighting was provided by HPS lamps at a photoperiod of 12h light: 12h dark. The photosynthetic photon flux was maintained at 500, 750 and 1000 micro mol m(sup -2) s(sub -1) during days 1-15, 16-28, 29-119, respectively. Canopy temperatures were maintained at 28 C: light: 22 C:dark. During the light period, relative humidity and carbon dioxide were maintained at 70% and 1200 micro liters l(sup -1), respectively. Nutrient solution was manually adjusted 2 to 4 times per week by addition of 10X concentrated modified half-strength Hoagland nutrient salts and NaOH to return the electrical conductivity and pH to 1.2 mS cm(sup -1) and 6.0, respectively. At 17 weeks (119 days) from transplanting, a total of 56.5 kilograms fresh mass of storage roots (84.1% moisture) were harvested from the 11.2 m(sup 2) chamber, resulting in a yield 5.0 kilograms m(sup -2). Harvest index, based on fresh mass, was 38.6%. Rates of net photosynthesis, dark respiration, transpiration, and ethylene production will be reported.

  20. Transpiration efficiency: new insights into an old story.

    PubMed

    Vadez, Vincent; Kholova, Jana; Medina, Susan; Kakkera, Aparna; Anderberg, Hanna

    2014-11-01

    Producing more food per unit of water has never been as important as it is at present, and the demand for water by economic sectors other than agriculture will necessarily put a great deal of pressure on a dwindling resource, leading to a call for increases in the productivity of water in agriculture. This topic has been given high priority in the research agenda for the last 30 years, but with the exception of a few specific cases, such as water-use-efficient wheat in Australia, breeding crops for water-use efficiency has yet to be accomplished. Here, we review the efforts to harness transpiration efficiency (TE); that is, the genetic component of water-use efficiency. As TE is difficult to measure, especially in the field, evaluations of TE have relied mostly on surrogate traits, although this has most likely resulted in over-dependence on the surrogates. A new lysimetric method for assessing TE gravimetrically throughout the entire cropping cycle has revealed high genetic variation in different cereals and legumes. Across species, water regimes, and a wide range of genotypes, this method has clearly established an absence of relationships between TE and total water use, which dismisses previous claims that high TE may lead to a lower production potential. More excitingly, a tight link has been found between these large differences in TE in several crops and attributes of plants that make them restrict water losses under high vapour-pressure deficits. This trait provides new insight into the genetics of TE, especially from the perspective of plant hydraulics, probably with close involvement of aquaporins, and opens new possibilities for achieving genetic gains via breeding focused on this trait. Last but not least, small amounts of water used in specific periods of the crop cycle, such as during grain filling, may be critical. We assessed the efficiency of water use at these critical stages. PMID:24600020

  1. Modelled hydraulic redistribution by sunflower (Helianthus annuus?L.) matches observed data only after including night-time transpiration.

    PubMed

    Neumann, Rebecca B; Cardon, Zoe G; Teshera-Levye, Jennifer; Rockwell, Fulton E; Zwieniecki, Maciej A; Holbrook, N Michele

    2014-04-01

    The movement of water from moist to dry soil layers through the root systems of plants, referred to as hydraulic redistribution (HR), occurs throughout the world and is thought to influence carbon and water budgets and ecosystem functioning. The realized hydrologic, biogeochemical and ecological consequences of HR depend on the amount of redistributed water, whereas the ability to assess these impacts requires models that correctly capture HR magnitude and timing. Using several soil types and two ecotypes of sunflower (Helianthus annuus?L.) in split-pot experiments, we examined how well the widely used HR modelling formulation developed by Ryel et?al. matched experimental determination of HR across a range of water potential driving gradients. H.?annuus carries out extensive night-time transpiration, and although over the last decade it has become more widely recognized that night-time transpiration occurs in multiple species and many ecosystems, the original Ryel et?al. formulation does not include the effect of night-time transpiration on HR. We developed and added a representation of night-time transpiration into the formulation, and only then was the model able to capture the dynamics and magnitude of HR we observed as soils dried and night-time stomatal behaviour changed, both influencing HR. PMID:24118010

  2. RATE OF TCE DEGRADATION IN PASSIVE REACTIVE BARRIERS CONSTRUCTED WITH PLANT MULCH (BIOWALLS)

    EPA Science Inventory

    This presentation reviews a case study at Altus AFB on the extent of treatment of TCE in a passive reactive barrier constructed with plant mulch. It presents data from a tracer test to estimate the rate of ground water flow at the site, and the residence time of water and TCE in...

  3. Effect of Seeding Rate and Planting Arrangement on Rye Cover Crop and Weed Growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Weed growth in winter cover crops in warm climates may contribute to weed management costs in subsequent crops. A two year experiment was conducted on an organic vegetable farm in Salinas, California, to determine the impact of seeding rate and planting arrangement on rye (Secale cereale L. cv. Merc...

  4. Coal flow aids reduce coke plant operating costs and improve production rates

    SciTech Connect

    Bedard, R.A.; Bradacs, D.J.; Kluck, R.W.; Roe, D.C.; Ventresca, B.P.

    2005-06-01

    Chemical coal flow aids can provide many benefits to coke plants, including improved production rates, reduced maintenance and lower cleaning costs. This article discusses the mechanisms by which coal flow aids function and analyzes several successful case histories. 2 refs., 10 figs., 1 tab.

  5. Effect of frequency of dosing of plant sterols on plasma cholesterol levels and synthesis rate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective was to compare the effects of plant sterols (PS) consumed as a single dose (single) at breakfast or as three doses consumed with breakfast, lunch and dinner (divided) on plasma lipoprotien levels and cholesterol endogenous fractional synthesis rate (FSR). A randomized, placebo-controll...

  6. The effect of proline application on the physiology of raphanus sativus plants grown under salinity stress

    Microsoft Academic Search

    M. A. Shaddad

    1990-01-01

    Transpiration rate, stomatal frequency, growth, contents of pigments, saccharides, total nitrogen, proteins and some nutritive\\u000a elements (K, Ca, Mg, P) of radish plants were significantly lowere dwith the rise in salinization levels using NaCl. Spraying\\u000a radish shoots with proline solution (200 g m-3) counteracted the above adverse effects, especially at low and moderate salinity.

  7. The effect of air humidity on nutrient uptake of some greenhouse plants

    Microsoft Academic Search

    H. R. Gisleröd; A. R. Selmer-Olsen; L. M. Mortensen

    1987-01-01

    Young plants of nine different greenhouse species were grown for 24 to 100 days at 55–60, 70–75, and 90–95% relative air humidity\\u000a (RH) in growth rooms. They were given a complete nutrient solution twice a week. Transpiration rate decreased significantly\\u000a by increasing RH from the lowest to the highest level inEuphorbia pulcherrima (60%), Begonia hiemalis (54%), Saintpaulia ionantha (54%), Nephrolepis

  8. Association between Residential Proximity to Fuel-Fired Power Plants and Hospitalization Rate for Respiratory Diseases

    PubMed Central

    Liu, Xiaopeng; Lessner, Lawrence

    2012-01-01

    Background: Air pollution is known to cause respiratory disease. Unlike motor vehicle sources, fuel-fired power plants are stationary. Objective: Using hospitalization data, we examined whether living near a fuel-fired power plant increases the likelihood of hospitalization for respiratory disease. Methods: Rates of hospitalization for asthma, acute respiratory infection (ARI), and chronic obstructive pulmonary disease (COPD) were estimated using hospitalization data for 1993–2008 from New York State in relation to data for residences near fuel-fired power plants. We also explored data for residential proximity to hazardous waste sites. Results: After adjusting for age, sex, race, median household income, and rural/urban residence, there were significant 11%, 15%, and 17% increases in estimated rates of hospitalization for asthma, ARI, and COPD, respectively, among individuals > 10 years of age living in a ZIP code containing a fuel-fired power plant compared with one that had no power plant. Living in a ZIP code with a fuel-fired power plant was not significantly associated with hospitalization for asthma or ARI among children < 10 years of age. Living in a ZIP code with a hazardous waste site was associated with hospitalization for all outcomes in both age groups, and joint effect estimates were approximately additive for living in a ZIP code that contained a fuel-fired power plant and a hazardous waste site. Conclusions: Our results are consistent with the hypothesis that exposure to air pollution from fuel-fired power plants and volatile compounds coming from hazardous waste sites increases the risk of hospitalization for respiratory diseases. PMID:22370087

  9. Water-use efficiency and transpiration across European forests during the Anthropocene

    NASA Astrophysics Data System (ADS)

    Frank, D. C.; Poulter, B.; Saurer, M.; Esper, J.; Huntingford, C.; Helle, G.; Treydte, K.; Zimmermann, N. E.; Schleser, G. H.; Ahlström, A.; Ciais, P.; Friedlingstein, P.; Levis, S.; Lomas, M.; Sitch, S.; Viovy, N.; Andreu-Hayles, L.; Bednarz, Z.; Berninger, F.; Boettger, T.; D`Alessandro, C. M.; Daux, V.; Filot, M.; Grabner, M.; Gutierrez, E.; Haupt, M.; Hilasvuori, E.; Jungner, H.; Kalela-Brundin, M.; Krapiec, M.; Leuenberger, M.; Loader, N. J.; Marah, H.; Masson-Delmotte, V.; Pazdur, A.; Pawelczyk, S.; Pierre, M.; Planells, O.; Pukiene, R.; Reynolds-Henne, C. E.; Rinne, K. T.; Saracino, A.; Sonninen, E.; Stievenard, M.; Switsur, V. R.; Szczepanek, M.; Szychowska-Krapiec, E.; Todaro, L.; Waterhouse, J. S.; Weigl, M.

    2015-06-01

    The Earth’s carbon and hydrologic cycles are intimately coupled by gas exchange through plant stomata. However, uncertainties in the magnitude and consequences of the physiological responses of plants to elevated CO2 in natural environments hinders modelling of terrestrial water cycling and carbon storage. Here we use annually resolved long-term ?13C tree-ring measurements across a European forest network to reconstruct the physiologically driven response of intercellular CO2 (Ci) caused by atmospheric CO2 (Ca) trends. When removing meteorological signals from the ?13C measurements, we find that trees across Europe regulated gas exchange so that for one ppmv atmospheric CO2 increase, Ci increased by ~0.76 ppmv, most consistent with moderate control towards a constant Ci/Ca ratio. This response corresponds to twentieth-century intrinsic water-use efficiency (iWUE) increases of 14 +/- 10 and 22 +/- 6% at broadleaf and coniferous sites, respectively. An ensemble of process-based global vegetation models shows similar CO2 effects on iWUE trends. Yet, when operating these models with climate drivers reintroduced, despite decreased stomatal opening, 5% increases in European forest transpiration are calculated over the twentieth century. This counterintuitive result arises from lengthened growing seasons, enhanced evaporative demand in a warming climate, and increased leaf area, which together oppose effects of CO2-induced stomatal closure. Our study questions changes to the hydrological cycle, such as reductions in transpiration and air humidity, hypothesized to result from plant responses to anthropogenic emissions.

  10. Interactive Effects of Soil Drainage and Time Since Burn on Transpiration of Boreal Black Spruce Forests

    NASA Astrophysics Data System (ADS)

    Angstmann, J. L.; Ewers, B. E.; Kwon, H.; Bond-Lamberty, B.; Amiro, B.; Gower, S. T.

    2006-12-01

    Boreal forests and their changing fire frequencies are of interest in global climate change because they comprise one-third of the world's forest coverage and store large amounts of carbon. Much of this carbon storage is due to peat formation in cold, poorly-drained boreal soils. Here, evapotranspiration plays a crucial role in the interaction between carbon and water cycles. The main objective of this study is to quantify the amount of water being released through transpiration as boreal forest stands recover from wildfires across well- to poorly-drained soil conditions. Species composition of this region of boreal forest changes during succession in well-drained soils from a mix of Picea mariana (black spruce), Pinus banksiana (jack pine), and Populus tremuloides (trembling aspen) in younger stands to being dominated solely by Picea mariana in older stands. Poorly-drained soils are dominated by Picea mariana throughout the chronosequence. Previous work in well-drained stands recovering from wildfires showed that in all but the oldest black spruce stands 1) tree transpiration changed dramatically with stand age due to sapwood-to-leaf area ratio dynamics and 2) minimum leaf water potential was kept constant to prevent excessive cavitation. Thus, we hypothesized that 1) minimum leaf water potential would be constant and 2) transpiration would be proportional to the sapwood-to- leaf area ratio across both stand age and soil drainage except for the two oldest black spruce stands. We tested these hypotheses by measuring leaf water potential (Psi) of 95 trees and sap flux from 111 trees. Mixed results were found in Picea mariana Psi between well- and poorly-drained areas of each stand age, with only the 17-year-old burn in July (average midday Psi of -0.77 and -1.08 MPa for well- and poorly drained respectively) and the 76-year-old burn in June (average predawn Psi of -0.52 and -0.42 MPa for well- and poorly drained respectively) differing significantly. Growing season averages of Psi for Picea mariana resulted in significantly different values of -0.29, -0.44, -0.42, -0.34 for pre-dawn and -1.09, -1.37, -1.20, -1.25 MPa for mid- day at the17-, 42-, 76-, and 156-year-old burns respectively. Our results show that stand age has more of an influence on black spruce water potentials and, likely, stand transpiration per unit leaf area than soil drainage. Thus, regional scale process models of boreal forest transpiration can be simplified with respect to soil drainage while retaining mechanistic rigor with respect to plant hydraulics.

  11. Visualization of early stress responses in plant leaves

    Microsoft Academic Search

    Laury Chaerle; Martin J. vande Ven; Roland L. Valcke; Dominique Van Der Straeten

    2002-01-01

    Plant leaves possess microscopic valves, called stomata, that enable control of transpirational water loss. In case of water shortage, stomata close, resulting in decreased transpirational cooling. The ensuing temperature increase is readily visualized by thermography. Salicylic acid, a central compound in the defense of plants against pathogens, also closes stomata in several species. In previous work, thermography permitted to monitor

  12. Simulation of Water Transport in the Soil-Plant - System.

    NASA Astrophysics Data System (ADS)

    Guo, Yimei

    1992-01-01

    The objective of this dissertation is to develop a mechanistic model of water transport in the soil-plant -atmosphere system that describes the plant's physical expression of water stress to study the effects of environmental factors, and plant hydraulic and physical properties on plant water transport. The model includes soil moisture uptake, soil heat and water transfer, evapotranspiration, and energy partitioning in the canopy and at the soil surface. The model inputs are: daily weather data (air temperature, dew point temperature, wind speed, and solar radiation); initial soil moisture and temperature profiles; plant characteristics; root density; and soil hydraulic properties. The model user may select from a number of outputs. Principal outputs include: leaf resistance, leaf temperature, soil moisture profile and evapotranspiration rate. The model describes a feedback mechanism by which transpiration controls leaf water potential, leaf water potential influences leaf resistance, and leaf resistance which, in turn, controls transpiration. The simulation runs represented the energy partitioning in the canopy and at the soil surface, and the diurnal variation of temperatures and vapor pressures of the leaf, the canopy air, and the soil surface. The relationships of leaf water potential to soil water potential, leaf resistance and transpiration were also presented. In addition, results show that root water extraction is related to the root length density profile and the soil moisture profile. The model mechanistically describes the water transport in the soil-plant-atmosphere system. The results of model validation indicated that the model is capable of simulating plant water transport under natural conditions with reasonable accuracy. Results show that the model simulates the basic features of the system including feedback processes. The sensitivity studies show that the model may be used to study plant water response to environmental factors and plant properties. The model is also useful for estimating evapotranspiration and the soil moisture profile and may provide information for irrigation and soil water management. (Abstract shortened with permission of author.).

  13. Response of ammonium removal to growth and transpiration of Juncus effusus during the treatment of artificial sewage in laboratory-scale wetlands.

    PubMed

    Wiessner, A; Kappelmeyer, U; Kaestner, M; Schultze-Nobre, L; Kuschk, P

    2013-09-01

    The correlation between nitrogen removal and the role of the plants in the rhizosphere of constructed wetlands are the subject of continuous discussion, but knowledge is still insufficient. Since the influence of plant growth and physiological activity on ammonium removal has not been well characterized in constructed wetlands so far, this aspect is investigated in more detail in model wetlands under defined laboratory conditions using Juncus effusus for treating an artificial sewage. Growth and physiological activity, such as plant transpiration, have been found to correlate with both the efficiency of ammonium removal within the rhizosphere of J. effusus and the methane formation. The uptake of ammonium by growing plant stocks is within in a range of 45.5%, but under conditions of plant growth stagnation, a further nearly complete removal of the ammonium load points to the likely existence of additional nitrogen removal processes. In this way, a linear correlation between the ammonium concentration inside the rhizosphere and the transpiration of the plant stocks implies that an influence of plant physiological activity on the efficiency of N-removal exists. Furthermore, a linear correlation between methane concentration and plant transpiration has been estimated. The findings indicate a fast response of redox processes to plant activities. Accordingly, not only the influence of plant transpiration activity on the plant-internal convective gas transport, the radial oxygen loss by the plant roots and the efficiency of nitrification within the rhizosphere, but also the nitrogen gas released by phytovolatilization are discussed. The results achieved by using an unplanted control system are different in principle and characterized by a low efficiency of ammonium removal and a high methane enrichment of up to a maximum of 72.7% saturation. PMID:23764577

  14. Evaluating a Model of Evaporation and Transpiration with Observations in a Partially Wet Douglas-Fir Forest

    NASA Astrophysics Data System (ADS)

    Bosveld, Fred C.; Bouten, Willem

    The Penman-Monteith equation is extended to describe evaporation of intercepted rain, transpiration and the interaction between these processes in a single explicit function. This single-layer model simulates the effects of heat exchange, stomatal blocking and changed humidity deficit close to the canopy as a function of canopywater storage. Evaporation depends on the distribution of water over the canopy and the energy exchange between wet and dry parts. Transpiration depends on the dry canopy surface resistance that is described with a Jarvis-type response. The explicit functions obtained for water vapour fluxes facilitate a straightforward identificationof the various processes. Canopy water storage amounts and xylem sapflow were measured simultaneously during drying episodes after rainfall in a dense, partially wet, Douglas-fir forest. Estimates of evaporation and transpiration rates are derived from these observations. The analysis shows that evaporation induced transpirationreduction is mainly caused by energy consumption. Changes in water vapour deficit have a minor effect due to a compensating stomatal reaction. The remaining difference between observed and modelled transpiration reduction can be attributed to partial blocking of stomata by the water layer.

  15. Aftereffects of low and high temperature pretreatment on leaf resistance, transpiration, and leaf temperature in xanthium.

    PubMed

    Drake, B G; Salisbury, F B

    1972-11-01

    Leaf resistance for water vapor (total diffusion resistance minus boundary layer resistance), transpiration, and leaf temperature were measured in attached leaves of greenhouse-grown Xanthium strumarium L. plants that had been pretreated for 72 hours with high (40 C day, 35 C night), or low (10 C day, 5 C night) air temperatures. Measurements were made in a wind tunnel at light intensity of 1.15 cal cm(-2) min(-1), air temperatures between 5 and 45 C, and wind speed of 65 cm sec(-1). Leaf resistances in low temperature pretreated plants were higher (8 to 27 sec cm(-1)) than in controls or high temperature pretreated plants (0.5 to 3 sec cm(-1)) at leaf temperatures between 5 and 25 C. Thus, the pretreatment influenced stomatal aperture. PMID:16658219

  16. Transpiration cooled ultraviolet sol-gel silica optics

    NASA Astrophysics Data System (ADS)

    Seth, Vinay K.; Noques, Jean-Luc

    1991-04-01

    All rocket guidance systems essentially require broadband optical transmission windows. These windows must also be temperature insensitive to transmission, thermal shock resistant, thermally stable, reasonably strong, and impact resistant. At hypersonic velocity, convective cooling is preferred to radiative cooling. Transpiration cooling is a novel and effective mode of convective cooling. Porous silica windows offer excellent rocket windows for transpiration cooling at a relatively inexpensive price. Sol-gel technology is an enabling technology which facilitates the fabrication of these rocket windows. This research used sol-gel technology to demonstrate the concept of transpiration-cooled porous silica windows. These windows were fabricated with various pore sizes and characterized with respect to gas diffusion, transpiration, high temperature transmission, thermal stability and shock resistance, hardness, impact resistance, and strength. The manufacturability aspect was also addressed. The diffusion of various gases through porous silica windows was studied and their permeabilities measured. In the experimental range, Knusden diffusion seemed to be the predominant mass transport mechanism. At a low transpiration velocity of 0.52 cm/s of helium, a 44 C temperature drop was observed showing the promise of this material for rocket window application. High temperature spectroscopy showed improved performance. The porous silica windows had thermal stability and thermal shock resistance and reasonable mechanical properties.

  17. Effects of elevated atmospheric CO{sub 2} on canopy transpiration in senescent spring wheat

    SciTech Connect

    Grossman, S.; Kimball, B.A.; Hunsaker, D.J.; Long, S.P. et al

    1998-12-31

    The seasonal course of canopy transpiration and the diurnal courses of latent heat flux of a spring wheat crop were simulated for atmospheric CO{sub 2} concentrations of 370 {micro}mol mol{sup {minus}1} and 550 {micro}mol mol{sup {minus}1}. The hourly weather data, soil parameters and the irrigation and fertilizer treatments of the Free-Air Carbon Dioxide Enrichment wheat experiment in Arizona (1992/93) were used to drive the model. The simulation results were tested against field measurements with special emphasis on the period between anthesis and maturity. A model integrating leaf photosynthesis and stomatal conductance was scaled to a canopy level in order to be used in the wheat growth model. The simulated intercellular CO{sub 2} concentration, C{sub i} was determined from the ratio of C{sub i} to the CO{sub 2} concentration at the leaf surface, C{sub s}, the leaf to air specific humidity deficit and a possibly unfulfilled transpiration demand. After anthesis, the measured assimilation rates of the flag leaves decreased more rapidly than their stomatal conductances, leading to a rise in the C{sub i}/C{sub s} ratio. In order to describe this observation, an empirical model approach was developed which took into account the leaf nitrogen content for the calculation of the C{sub i}/C{sub s} ratio. Simulation results obtained with the new model version were in good agreement with the measurements. If changes in the C{sub i}/C{sub s} ratio accorded to the decrease in leaf nitrogen content during leaf senescence were not considered in the model, simulations revealed an underestimation of the daily canopy transpiration of up to twenty percent and a decrease in simulated seasonal canopy transpiration by ten percent. The measured reduction in the seasonal sum of canopy transpiration and soil evaporation owing to CO{sub 2} enrichment, in comparison, was only about five percent.

  18. [Morphophysiological and biochemical characteristics of potato plants with various expression rates of the ?12 acyl-lipid desaturase gene].

    PubMed

    Zagoskina, N V; Priadekhina, E V; Lapshin, P V; Iur'eva, N O; Goldenkova-Pavlova, I V

    2014-01-01

    This paper reports on morphophysiological and biochemical characteristics of control and potato plants (Solarium tuberosum L., Skoroplodnyi cultivar) transformed with the ?12 acyl-lipid desaturase gene (desA) grown long-term in vitro. The transformed plants showed faster growth and faster ontogenesis as compared to controls, which was accompanied with changes in the accumulation of photosynthetic pigments (chlorophylls a and b, carotenoids) and phenolic compounds, including flavonoids in the leaves. These characteristics were pronounced to a high degree in Line II plants with high expression rates of the desA gene, whereas Line I plants (moderate expression rate) were similar to control plants in many parameters. PMID:25735165

  19. Supplementary documentation for an Environmental Impact Statement regarding the Pantex Plant: a comparison of county and state cancer mortality rates

    Microsoft Academic Search

    L. D. Wiggs; G. S. Wilkinson; G. L. Tietjen; J. F. Acquavella

    1982-01-01

    This report documents work performed in support of preparation of an Environmental Impact Statement (EIS) regarding the Department of Energy's Pantex Plant near Amarillo, Texas. This report considers cancer mortality rates in the region surrounding the Pantex nuclear weapons facility. The working hypothesis was that increased cancer mortality rates would exist in counties proximal to the Pantex Plant. To evaluate

  20. Estimation of Rates of Recombination and Migration in Populations of Plant Pathogens?A Reply

    Microsoft Academic Search

    J. Zhan; C. C. Mundt; B. A. McDonald

    2000-01-01

    Zhan, J., Mundt, C. C., and McDonald, B. A. 2000. Estimation of rates of recombination and migration in populations of plant pathogens —A reply. Phytopathology 90:324-326. We find that the maximum likelihood method proposed by J. K. M. Brown has deficiencies that limit its usefulness for actual data sets. We propose two alternative statistical methods based on maximum likelihood that

  1. Response of Popcorn (Zea mays everta) to Nitrogen Rates and Plant Densities

    Microsoft Academic Search

    Sabri GÖKMEN; Özer SENCAR; Mehmet Ali SAK

    The objective of this study was to evaluate grain yield and yield components of popcorn with different nitrogen rates and plant densities. Field studies were conducted in 1995 and 1996 at Kazova Plain in Tokat. The experiment was designed in a randomized-complete-block design with a split-plot arrangement with three replications. The treatments comprised six levels of nitrogen (0, 50, 100,

  2. Photosynthesis in intact leaves of C 3 plants: Physics, physiology and rate limitations

    Microsoft Academic Search

    Thomas D. Sharkey

    1985-01-01

    The instantaneous rate of photosynthetic CO2 assimilation in C3 plants has generally been studied in model systems such as isolated chloroplasts and algae. From these studies and from theoretical\\u000a analyses of gas exchange behavior it is now possible to study the biochemistry of photosynthesis in intact leaves using a\\u000a combination of methods, most of which are nondestructive.\\u000a \\u000a The limitations to

  3. Numerical reconstruction of high dose rate zones due to the Fukushima Daiichi Nuclear Power Plant accident

    Microsoft Academic Search

    Genki Katata; Hiroaki Terada; Haruyasu Nagai; Masamichi Chino

    To understand how the high dose rate zones were created during the Fukushima Daiichi Nuclear Power Plant (FNPP1) accident on March 2011, the atmospheric dispersion of radionuclides during the period from 15 to 17 March was reproduced by using a computer-based nuclear emergency response system, WSPEEDI-II. With use of limited environmental monitoring data, prediction accuracy of meteorological and radiological fields

  4. The Control of Transpiration. Insights from Arabidopsis

    Microsoft Academic Search

    Sarah E. Nilson; Sarah M. Assmann

    2006-01-01

    Stomatal complexes in the epidermes of aerial plant parts are critical sites for the regulation of gas ex- change between the plant and the atmosphere. Sto- mata consist of microscopic pores, each flanked by a pair of guard cells. Guard cells can increase or de- crease the size of the pore via changes in their turgor status, hence regulating both

  5. Transpiration's inhibition of air pollution fluxes to substomatal cavities. [PRECP

    SciTech Connect

    Slinn, W.G.N.

    1987-05-01

    This report presents an estimate for the resistance to transport through stomatal openings, accounting for the counterflowing flux of water vapor associated with transpiration. The specific goal of this report is to estimate the influence of transpiration on the stomatal resistance, r/sub sto/; others have estimated the substomatal and mesophyll resistances r/sub ssc/ and r/sub mes/. It might be expected that any influence of the water-vapor flux on pollutant transport would be a maximum at the stomatal opening since, at the constricted area of the stoma, the water flux is a maximum. Transpiration through stomata appears to insigifnicantly inhibit the passage of relatively small molecules (e.g., SO/sub 2/, O/sub 3/, HNO/sub 3/, PAN, etc.) through the stomata, and therefore, by entering the substomatal cavity, such pollutants have greater potential for threatening plan survival, if their concentrations are excessive. 7 refs., 5 figs.

  6. Measurement of Effective Canopy Temperature: The Missing Link to Modeling Transpiration in Controlled Environments

    NASA Technical Reports Server (NTRS)

    Monje, O. A.; McCormack, Ann; Bugbee, Bruce; Jones, Harry W., Jr. (Technical Monitor)

    1994-01-01

    The objectives were to apply energy balance principles to plant canopies, and to determine which parameters are essential for predicting plant canopy transpiration (E) in controlled environments. Transpiration was accurately measured in a gas-exchange system. Absorbed radiation (R(sub abs)) by the canopy was measured with a net radiometer and calculated from short and long-wave radiation components. Average canopy foliar temperature T(sub L) can be measured with an infrared radiometer, but since T(sub L) is seldom uniform, a weighed average measurement of T(sub L) must be made. The effective canopy temperature T(sub C) is that temperature that balances the energy flux between absorbed radiation and latent heat L(sub E) and sensible heat (H) fluxes. TC should exactly equal air temperature T(sub A) when L(sub E) equals R(sub abs). When unnecessary thermal radiation from the lighting system is removed by a water filter, the magnitude of L(sub E) from transpiration approaches Rabs and T(sub C) is close to T(sub A). Unlike field models, we included the energy used in photosynthesis and found that up to 10% of Rabs was used in photosynthesis. We calculated aerodynamic conductance for H from measurements of wind speed and canopy height using the wind profile equation. Canopy aerodynamic conductance ranged from.03 to.04 m/s for wind speeds from.6 to 1 m/s; thus a 0.1 C canopy to air temperature difference results in a sensible heat flux of about 4 W/sq m, which is only 1% of R(sub abs). We examined the ability of wide angle infrared transducers to accurately integrate T(sub L) from the top to the bottom of the canopy. We measured evaporation from the hydroponic media to be approximately 1 micro mol/sq m s or 10% of R(sub abs). This result indicates that separating evaporation from transpiration is more important than exact measurement of canopy temperature.

  7. Comparative evapotranspiration rates of thirteen turfgrasses grown under both non-limiting soil moisture and progressive water stress conditions 

    E-print Network

    Kim, Ki Sun

    1983-01-01

    and transpiration from the plants growing thereon. ET rate is commonly expressed quantitatively as -2 -1 milligrams per square meter per second (mg m sec ) or as milli- meters per day (mm/day). The term ET rate is preferred to WUR in scientific literature... yield. Only a limited number of references are available concerning ET rate studies on turfgrasses (2, 4, 14, 15, 16, 22, 23, 27, 28, 29, 31, 32, 35, 41, 47, 51). The general zange reported for ET rates of most turfgrass is 2 to 6 mm (0. 1 to 0. 3...

  8. Cyclic variations in nitrogen uptake rate of soybean plants: ammonium as a nitrogen source

    NASA Technical Reports Server (NTRS)

    Henry, L. T.; Raper, C. D. Jr

    1989-01-01

    When NO3- is the sole nitrogen source in flowing solution culture, the net rate of nitrogen uptake by nonnodulated soybean (Glycine max L. Merr. cv Ransom) plants cycles between maxima and minima with a periodicity of oscillation that corresponds with the interval of leaf emergence. Since soybean plants accumulate similar quantities of nitrogen when either NH4+ or NO3- is the sole source in solution culture controlled at pH 6.0, an experiment was conducted to determine if the oscillations in net rate of nitrogen uptake also occur when NH4+ is the nitrogen source. During a 21-day period of vegetative development, net uptake of NH4+ was measured daily by ion chromatography as depletion of NH4+ from a replenished nutrient solution containing 1.0 millimolar NH4+. The net rate of NH4+ uptake oscillated with a periodicity that was similar to the interval of leaf emergence. Instances of negative net rates of uptake indicate that the transition between maxima and minima involved changes in influx and efflux components of net NH4+ uptake.

  9. Island radiation on a continental scale: Exceptional rates of plant diversification after uplift of the Andes

    PubMed Central

    Hughes, Colin; Eastwood, Ruth

    2006-01-01

    Species radiations provide unique insights into evolutionary processes underlying species diversification and patterns of biodiversity. To compare plant diversification over a similar time period to the recent cichlid fish radiations, which are an order of magnitude faster than documented bird, arthropod, and plant radiations, we focus on the high-altitude flora of the Andes, which is the most species-rich of any tropical mountains. Because of the recent uplift of the northern Andes, the upland environments where much of this rich endemic flora is found have been available for colonization only since the late Pliocene or Pleistocene, 2–4 million years (Myr) ago. Using DNA sequence data we identify a monophyletic group within the genus Lupinus representing 81 species endemic to the Andes. The age of this clade is estimated to be 1.18–1.76 Myr, implying a diversification rate of 2.49–3.72 species per Myr. This exceeds previous estimates for plants, providing the most spectacular example of explosive plant species diversification documented to date. Furthermore, it suggests that the high cichlid diversification rates are not unique. Lack of key innovations associated with the Andean Lupinus clade suggests that diversification was driven by ecological opportunities afforded by the emergence of island-like habitats after Andean uplift. Data from other genera indicate that lupines are one of a set of similarly rapid Andean plant radiations, continental in scale and island-like in stimulus, suggesting that the high-elevation Andean flora provides a system that rivals other groups, including cichlids, for understanding rapid species diversification. PMID:16801546

  10. Fire and grazing influences on rates of riparian woody plant expansion along grassland streams.

    PubMed

    Veach, Allison M; Dodds, Walter K; Skibbe, Adam

    2014-01-01

    Grasslands are threatened globally due to the expansion of woody plants. The few remaining headwater streams within tallgrass prairies are becoming more like typical forested streams due to rapid conversion of riparian zones from grassy to wooded. Forestation can alter stream hydrology and biogeochemistry. We estimated the rate of riparian woody plant expansion within a 30 m buffer zone surrounding the stream bed across whole watersheds at Konza Prairie Biological Station over 25 years from aerial photographs. Watersheds varied with respect to experimentally-controlled fire and bison grazing. Fire frequency, presence or absence of grazing bison, and the historical presence of woody vegetation prior to the study time period (a proxy for proximity of propagule sources) were used as independent variables to predict the rate of riparian woody plant expansion between 1985 and 2010. Water yield was estimated across these years for a subset of watersheds. Riparian woody encroachment rates increased as burning became less frequent than every two years. However, a higher fire frequency (1-2 years) did not reverse riparian woody encroachment regardless of whether woody vegetation was present or not before burning regimes were initiated. Although riparian woody vegetation cover increased over time, annual total precipitation and average annual temperature were variable. So, water yield over 4 watersheds under differing burn frequencies was quite variable and with no statistically significant detected temporal trends. Overall, burning regimes with a frequency of every 1-2 years will slow the conversion of tallgrass prairie stream ecosystems to forested ones, yet over long time periods, riparian woody plant encroachment may not be prevented by fire alone, regardless of fire frequency. PMID:25192194

  11. Fire and Grazing Influences on Rates of Riparian Woody Plant Expansion along Grassland Streams

    PubMed Central

    Veach, Allison M.; Dodds, Walter K.; Skibbe, Adam

    2014-01-01

    Grasslands are threatened globally due to the expansion of woody plants. The few remaining headwater streams within tallgrass prairies are becoming more like typical forested streams due to rapid conversion of riparian zones from grassy to wooded. Forestation can alter stream hydrology and biogeochemistry. We estimated the rate of riparian woody plant expansion within a 30 m buffer zone surrounding the stream bed across whole watersheds at Konza Prairie Biological Station over 25 years from aerial photographs. Watersheds varied with respect to experimentally-controlled fire and bison grazing. Fire frequency, presence or absence of grazing bison, and the historical presence of woody vegetation prior to the study time period (a proxy for proximity of propagule sources) were used as independent variables to predict the rate of riparian woody plant expansion between 1985 and 2010. Water yield was estimated across these years for a subset of watersheds. Riparian woody encroachment rates increased as burning became less frequent than every two years. However, a higher fire frequency (1–2 years) did not reverse riparian woody encroachment regardless of whether woody vegetation was present or not before burning regimes were initiated. Although riparian woody vegetation cover increased over time, annual total precipitation and average annual temperature were variable. So, water yield over 4 watersheds under differing burn frequencies was quite variable and with no statistically significant detected temporal trends. Overall, burning regimes with a frequency of every 1–2 years will slow the conversion of tallgrass prairie stream ecosystems to forested ones, yet over long time periods, riparian woody plant encroachment may not be prevented by fire alone, regardless of fire frequency. PMID:25192194

  12. Cooling Duct Analysis for Transpiration/Film Cooled Liquid Propellant Rocket Engines

    NASA Technical Reports Server (NTRS)

    Micklow, Gerald J.

    1996-01-01

    The development of a low cost space transportation system requires that the propulsion system be reusable, have long life, with good performance and use low cost propellants. Improved performance can be achieved by operating the engine at higher pressure and temperature levels than previous designs. Increasing the chamber pressure and temperature, however, will increase wall heating rates. This necessitates the need for active cooling methods such as film cooling or transpiration cooling. But active cooling can reduce the net thrust of the engine and add considerably to the design complexity. Recently, a metal drawing process has been patented where it is possible to fabricate plates with very small holes with high uniformity with a closely specified porosity. Such a metal plate could be used for an inexpensive transpiration/film cooled liner to meet the demands of advanced reusable rocket engines, if coolant mass flow rates could be controlled to satisfy wall cooling requirements and performance. The present study investigates the possibility of controlling the coolant mass flow rate through the porous material by simple non-active fluid dynamic means. The coolant will be supplied to the porous material by series of constant geometry slots machined on the exterior of the engine.

  13. Studies of shock/shock interaction on smooth and transpiration-cooled hemispherical nosetips in hypersonic flow

    NASA Technical Reports Server (NTRS)

    Holden, Michael S.; Rodriguez, Kathleen M.

    1992-01-01

    A program of experimental research and analysis was conducted to examine the heat transfer and pressure distributions in regions of shock/shock interaction over smooth and transpiration-cooled hemispherical noseshapes. The objective of this investigation was to determine whether the large heat transfer generated in regions of shock/shock interaction can be reduced by transpiration cooling. The experimental program was conducted at Mach numbers of 12 to 16 in the Calspan 48-Inch Shock Tunnel. Type 3 and type 4 interaction regions were generated for a range of freestream unit Reynolds numbers to provide shear layer Reynolds numbers from 10 exp 4 to 10 exp 6 to enable laminar and turbulent interaction regions to be studied. Shock/shock interactions were investigated on a smooth hemispherical nosetip and a similar transpiration-cooled nosetip, with the latter configuration being examined for a range of surface blowing rates up to one-third of the freestream mass flux. While the heat transfer measurements on the smooth hemisphere without shock/shock interaction were in good agreement with Fay-Riddell predictions, those on the transpiration-cooled nosetip indicated that its intrinsic roughness caused heating-enhancement factors of over 1.5. In the shock/shock interaction studies on the smooth nosetip, detailed heat transfer and pressure measurements were obtained to map the variation of the distributions with shock-impingement position for a range of type 3 and type 4 interactions. Such sets of measurements were obtained for a range of unit Reynolds numbers and Mach numbers to obtain both laminar and turbulent interactions. The measurements indicated that shear layer transition has a significant influence on the heating rates for the type 4 interaction as well as the anticipated large effects on type 3 interaction heating. In the absence of blowing, the peak heating in the type 3 and type 4 interaction regions, over the transpiration-cooled model, did not appear to be influenced by the model's rough surface characteristics. The studies of the effects of the transpiration cooling on type 3 and type 4 shock/shock interaction regions demonstrated that large surface blowing rates had significant effect on the structure of the flowfield, enlarging the shock layer and moving the region of peak-heating interaction around the body.

  14. Adapting FAO-56 Spreadsheet Program to estimate olive orchard transpiration fluxes under soil water stress condition

    NASA Astrophysics Data System (ADS)

    Rallo, G.; Provenzano, G.; Manzano-Juárez, J.

    2012-04-01

    In the Mediterranean environment, where the period of crops growth does not coincide with the rainy season, the crop is subject to water stress periods that may be amplified with improper irrigation management. Agro-hydrological models can be considered an economic and simple tool to optimize irrigation water use, mainly when water represents a limiting factor for crop production. In the last two decades, agro-hydrological physically based models have been developed to simulate mass and energy exchange processes in the soil-plant-atmosphere system (Feddes et al., 1978; Bastiaanssen et al., 2007). Unfortunately these models, although very reliable, as a consequence of the high number of required variables and the complex computational analysis, cannot often be used. Therefore, simplified agro-hydrological models may represent an useful and simple tool for practical irrigation scheduling. The main objective of the work is to assess, for an olive orchard, the suitability of FAO-56 spreadsheet agro-hydrological model to estimate a long time series of field transpiration, soil water content and crop water stress dynamic. A modification of the spreadsheet is suggested in order to adapt the simulations to a crop tolerant to water stress. In particular, by implementing a new crop water stress function, actual transpiration fluxes and an ecophysiological stress indicator, i. e. the relative transpiration, are computed in order to evaluate a plant-based irrigation scheduling parameter. Validation of the proposed amendment is carried out by means of measured sap fluxes, measured on different plants and up-scaled to plot level. Spatial and temporal variability of soil water contents in the plot was measured, at several depths, using the Diviner 2000 capacitance probe (Sentek Environmental Technologies, 2000) and TDR-100 (Campbell scientific, Inc.) system. The detailed measurements of soil water content, allowed to explore the high spatial variability of soil water content due to the combined effect of the punctual irrigation and the non-uniform root density distribution. A further validation of the plant-based irrigation-timing indicator will be carried out by considering another ecophysiological stress variable like the predawn leaf water potential. Accuracy of the model output was assessed using the Mean Absolute Difference, the Root Mean Square Difference and the efficiency index of Nash and Sutcliffe. Experimental data, recorded during three years of field observation, allowed, with a great level of detail, to investigate on the dynamic of water fluxes from the soil to atmosphere as well as to validate the proposed amendment of the FAO-56 spreadsheet. The modified model simulated with a satisfactory approximation the measured values of average soil water content in the root zone, with error of estimation equal to about 2.0%. These differences can be considered acceptable for practical applications taking into account the intrinsic variability of the data especially in the soil moisture point measurements. An error less than 1 mm was calculated in the daily transpiration estimation. A good performance was observed in the estimation of the cumulate transpiration fluxes.

  15. A simple method for estimating water loss by transpiration in wetlands

    Microsoft Academic Search

    SALVADOR SÂNCHEZ-CARRILLO; MIGUEL ÂLVAREZ-COBELAS; MANUEL BENITEZ; DAVID G. ANGELER

    Estimates of transpiration are often needed for hydrological management in wetlands. A new and simple method, using a portable steady-state porometer, is presented for estimating transpiration in three aquatic emergent macrophytes (reed, cut-sedge, and cattail). The method was established on the basis of the relationships between transpiration, solar radiation, relative humidity and air temperature. By assessing relationships between all variables

  16. A simple method for estimating water loss by transpiration in wetlands

    Microsoft Academic Search

    SALVADOR SÁNCHEZ-CARRILLO; MIGUEL ÁLVAREZ-COBELAS; MANUEL BENÍTEZ; DAVID G. ANGELER

    2001-01-01

    Estimates of transpiration are often needed for hydrological management in wetlands. A new and simple method, using a portable steady-state porometer, is presented for estimating transpiration in three aquatic emergent macrophytes (reed, cut-sedge, and cattail). The method was established on the basis of the relationships between transpiration, solar radiation, relative humidity and air temperature. By assessing relationships between all variables

  17. Original article Tree canopy and herb layer transpiration in three Scots

    E-print Network

    Paris-Sud XI, Université de

    Original article Tree canopy and herb layer transpiration in three Scots pine stands with different - To evaluate the impact of herb layer structure on the transpiration of Scots pine ecosystems in north-eastern Germany, we measured tree canopy and herb layer transpiration in three stands. Parameters of tree

  18. Effects of plant genotype and insect dispersal rate on the population dynamics of a forest pest.

    PubMed

    Moran, Emily V; Bewick, Sharon; Cobbold, Christina A

    2013-12-01

    It has been shown that plant genotype can strongly affect not only individual herbivore performance, but also community composition and ecosystem function. Few studies, however, have addressed how plant genotype affects herbivore population dynamics. In this paper, we used a simulation modeling approach to ask how the genetic composition of a forest influences pest outbreak dynamics, using the example of aspen (Populus tremuloides) and forest tent caterpillars (FTC; Malacosoma disstria). Specifically, we examined how plant genotype, the relative size of genotypic patches, and the rate of insect dispersal between them, affect the frequency, amplitude, and duration of outbreaks. We found that coupling two different genotypes does not necessarily result in an averaging of insect dynamics. Instead, depending on the ratio of patch sizes, when dispersal rates are moderate, outbreaks in the two-genotype case may be more or less severe than in forests of either genotype alone. Thresholds for different dynamic behaviors were similar for all genotypic combinations. Thus, the qualitative behavior of a stand of two different genotypes can be predicted based on the response of the insect to each genotype, the relative sizes of the two patches, and the scale of insect dispersal. PMID:24597225

  19. Atmospheric CO2 Enrichment of Water Hyacinths: Effects on Transpiration and Water Use Efficiency

    NASA Astrophysics Data System (ADS)

    Idso, Sherwood B.; Kimball, Bruce A.; Anderson, Michael G.

    1985-11-01

    Open-top clear plastic wall chambers enclosing pairs of sunken metal stock tanks, one of each pair of which contained a full cover of water hyacinths, were maintained out-of-doors at Phoenix, Arizona for several weeks during the summer of 1984. One of these chambers represented ambient conditions, while the other three were continuously enriched with carbon dioxide to approximate target concentrations of 500, 650, and 900 ppm. During a 4-week period when plant growth was at its maximum, water hyacinth biomass production increased by 36% for a 300-600 ppm doubling of the atmospheric CO2 content, while water use efficiency, or the biomass produced per unit of water transpired, actually doubled. These results are similar to what has been observed in several terrestrial plants and they indicate the general trend which may be expected to occur as atmospheric CO2 continues to rise in the years ahead.

  20. Boron mobility in plants

    Microsoft Academic Search

    Barry J. Shelp; Eduardo Marentes; Alice M. Kitheka; Pathmanathan Vivekanandan

    1995-01-01

    In the majority of plant species, B distribution between plant organs and the symptoms of B deficiency and toxicity indicate that B has restricted mobility. Nevertheless, B is present in phloem and is retranslocated in phloem, often in sufficient amounts to satisfy the demands of developing sink regions that do not readily transpire. In species that produce significant amounts of

  1. Boron mobility in plants

    Microsoft Academic Search

    Patrick H. Brown; Barry J. Shelp

    1997-01-01

    In the majority of plant species, B distribution between plant organs and the symptoms of B deficiency and toxicity indicate that B has restricted mobility. Nevertheless, B is present in phloem and is retranslocated in phloem, often in sufficient amounts to satisfy the demands of developing sink regions that do not readily transpire. In species that produce significant amounts of

  2. Transpiration of Grapevines in the Humid Northeastern United States

    Microsoft Academic Search

    Danilo Dragoni; Alan N. Lakso; Richard M. Piccioni; Julie M. Tarara

    For irrigation design and scheduling, water use of crops is commonly estimated from grass reference evapo- transpiration (ET0) estimates multiplied by published crop coefficients (kc). This method is assumed to stabilize kc across climates because of the response of ET0 to meteorological variables. However, the simple application of reference grass-based kc models may not be accurate in a cool, humid

  3. Reduction of tropical land region precipitation variability via transpiration

    E-print Network

    Gentine, Pierre

    ; accepted 22 August 2012; published 3 October 2012. [1] Tropical rainforests are known to exhibit low transpiration is disabled in the model. It is also shown that surface turbulent fluxes over tropical rainforests rainforests compared with adjacent oceanic regions [Sobel et al., 2008]. More generally, tropical rainforests

  4. TRANSPIRATION AND HYDRAULIC STRATEGIES IN A PINON-JUNIPER WOODLAND

    Microsoft Academic Search

    A. G. WEST; K. R. HULTINE; J. S. S PERRY; J. R. EHLERINGER

    2008-01-01

    Anthropogenic climate change is likely to alter the patterns of moisture availability globally. The consequences of these changes on species distributions and ecosystem function are largely unknown, but possibly predictable based on key ecophysio- logical differences among currently coexisting species. In this study, we examined the environmental and biological controls on transpiration from a pinon-juniper (Pinus edulis- Juniperus osteosperma) woodland

  5. The transpiration of water at negative pressures in a synthetic tree.

    PubMed

    Wheeler, Tobias D; Stroock, Abraham D

    2008-09-11

    Plant scientists believe that transpiration-the motion of water from the soil, through a vascular plant, and into the air-occurs by a passive, wicking mechanism. This mechanism is described by the cohesion-tension theory: loss of water by evaporation reduces the pressure of the liquid water within the leaf relative to atmospheric pressure; this reduced pressure pulls liquid water out of the soil and up the xylem to maintain hydration. Strikingly, the absolute pressure of the water within the xylem is often negative, such that the liquid is under tension and is thermodynamically metastable with respect to the vapour phase. Qualitatively, this mechanism is the same as that which drives fluid through the synthetic wicks that are key elements in technologies for heat transfer, fuel cells and portable chemical systems. Quantitatively, the differences in pressure generated in plants to drive flow can be more than a hundredfold larger than those generated in synthetic wicks. Here we present the design and operation of a microfluidic system formed in a synthetic hydrogel. This synthetic 'tree' captures the main attributes of transpiration in plants: transduction of subsaturation in the vapour phase of water into negative pressures in the liquid phase, stabilization and flow of liquid water at large negative pressures (-1.0 MPa or lower), continuous heat transfer with the evaporation of liquid water at negative pressure, and continuous extraction of liquid water from subsaturated sources. This development opens the opportunity for technological uses of water under tension and for new experimental studies of the liquid state of water. PMID:18784721

  6. Transpiration as the Leak in a Carbon Factory: A Model of Self-Optimising Vegetation

    NASA Astrophysics Data System (ADS)

    Sivapalan, M.; Schymanski, S. J.; Roderick, M. L.

    2005-12-01

    "Only now it occurred to me that plants are not water pumps but carbon factories" (Anonymous Hydrologist). When thinking of plants as `water pumps', we are led to the conclusion that vegetation would tend to maximise the total amount of transpiration while minimising the occurrence probability of periods without adequate water availability (`stress'). However, this does not do adequate justice to the fact that plants owe their existence to photosynthesis, and can thrive perfectly well even when the relative humidity of the air is very high and transpiration is almost negligible. In this paper, we present a model in which the maximisation of net CO2 uptake rather than maximisation of water use or minimisation of `stress' is assumed to be the driving force behind natural selection. Transpiration is the inevitable consequence of CO2 uptake from the atmosphere and water uptake from the soil incurs construction and maintenance costs of a root system, so that water use strategies become a consequence of the maximisation of net CO2 uptake and `stress' becomes an obsolete feature. We will demonstrate that a simple model based on ecological optimality is capable of reproducing some vegetation and water balance dynamics without any prior knowledge about the vegetation on a particular site. The model is based on a physical water balance model by Reggiani et al. (2000), an ecophysiological gas exchange and photosynthesis model (Cowan and Farquhar 1977; von Caemmerer 2000), and the hypothesis that natural selection leads to a vegetation type that optimally uses available resources to maximise its `net carbon profit' (the net tradeoff between carbon acquired by photosynthesis and carbon spent on maintenance of the organs involved in its uptake). While, at this early stage of its development, the site properties such as soil type and depth, topography and climate still have to be prescribed, the model creates the `optimal' dynamically adjusting vegetation for the particular site and calculates the water- and CO2- fluxes between soil, watershed boundaries, vegetation and atmosphere. Cowan, I. R. and G. D. Farquhar (1977). Stomatal Function in Relation to Leaf Metabolism and Environment. Integration of activity in the higher plant. D. H. Jennings. Cambridge, Cambridge University Press: 471-505. Reggiani, P., M. Sivapalan, et al. (2000). Conservation equations governing hillslope responses: Exploring the physical basis of water balance. Water Resources Research 36(7): 1845-1863. von Caemmerer, S. (2000). Biochemical Models of Leaf Photosynthesis. Collingwood, CSIRO Publishing.

  7. Variation in decomposition rates in the fynbos biome, South Africa: the role of plant species and plant stoichiometry

    PubMed Central

    Janion, Charlene; Chown, Steven L.; Leinaas, Hans Petter

    2010-01-01

    Previous studies in the fynbos biome of the Western Cape, South Africa, have suggested that biological decomposition rates in the fynbos vegetation type, on poor soils, may be so low that fire is the main factor contributing to litter breakdown and nutrient release. However, the fynbos biome also comprises vegetation types on more fertile soils, such as the renosterveld. The latter is defined by the shrub Elytropappus rhinocerotis, while the shrub Galenia africana may become dominant in overgrazed areas. We examined decomposition of litter of these two species and the geophyte Watsonia borbonica in patches of renosterveld in an agricultural landscape. In particular, we sought to understand how plant species identity affects litter decomposition rates, especially through variation in litter stoichiometry. Decomposition (organic matter mass loss) varied greatly among the species, and was related to litter N and P content. G. africana, with highest nutrient content, lost 65% of its original mass after 180 days, while E. rhinocerotis had lost ca. 30%, and the very nutrient poor W. borbonica <10%. Litter placed under G. africana decomposed slightly faster than when placed under E. rhinocerotis. Over the course of the experiment, G. africana and E. rhinocerotis lost N and P, while W. borbonica showed strong accumulation of these elements. Decomposition rates of G. africana and E. rhinocerotis were substantially higher than those previously reported from fynbos vegetation, and variation among the species investigated was considerable. Our results suggest that fire may not always be the main factor contributing to litter breakdown and nutrient release in the fynbos biome. Thus, biological decomposition has likely been underestimated and, along with small-scale variation in ecosystem processes, would repay further study. Electronic supplementary material The online version of this article (doi:10.1007/s00442-010-1753-7) contains supplementary material, which is available to authorized users. PMID:20827492

  8. Numerical analysis of gas separator with thermal transpiration in micro channels II

    NASA Astrophysics Data System (ADS)

    Nakaye, Shoeji; Sugimoto, Hiroshi

    2014-12-01

    A membrane gas separator which operates with only a small temperature difference across a membrane is designed, and its capability is numerically proved. The separator system consists of three Knudsen pumps - a motionless pump that utilizes the thermal transpiration of the rarefied gas. Each pump is composed of a porous membrane and one channel along each of the two surfaces of the membrane. Two of the pumps induce a variation of mole fraction using a combination of the thermal transpiration and pressure driven flow through the membrane, and the other one provides the former two pumps with a required pressure difference. This paper reports the first numerical calculations that demonstrate a neon-argon binary gas mixture can be separated into pure neon gas and argon gas with the proposed design. The temperature difference is no more than 90 K, and the total length of the membrane is ˜ 15 cm at standard ambient temperature and pressure. The production rate of the separator is proportional to the width of the membrane. For example, when the width is 10 cm, the flow rates of the product gases are 0.8 sccm for argon and 1.9 sccm for neon.

  9. A thermal method for measuring the rate of water movement in plants 

    E-print Network

    Bloodworth, Morris Elkins

    1958-01-01

    and thermistor mounted in plastic clips that are permanently spaced 1.9 centimeters 22 8??B? o? ????o??? ???? ? ??o? ??????8?8?A ???8 oA ?B??o??8 AB ?????8 ??B? B?8 ????A ?A8? AB ??BA?8? LoA?o? ? ??AA8? B? ?8?B???V ^?8 8??8?o?8?A?? ??B?8???8 ?B? ???o... ET ER DE FL EC TI O N 8 0 ? 38 70 - 60 50 ? 40 V EFFECT OF TEMPERATURE ? HUMIDITY ? WIND CHANGES UPON WATER MOVEMENT RATES IN A COTTON PLANT 1 T l 1 ^ i 1 1 A- ? - 0 /5 ' / \\ ----------- / i / ? / - V \\ TEMP. R...

  10. Effect of NaCl salinity on growth, pigment and mineral element contents, and gas exchange of broad bean and pea plants

    Microsoft Academic Search

    A. M. HAMADA; A. E. El-Enany

    1994-01-01

    Increasing salinity of growth medium induced a reduction in growth and transpiration rate. The concentrations of chlorophylls\\u000a and carotenoids were increased in most cases in broad bean leaves while in pea plants they remained more or less unchanged\\u000a with the rise of salinization up to 80mM NaCl. Thereabove a significant decrease in these contents was observed. A stimulation\\u000a of the

  11. Transpiration, and Nitrogen Uptake and Flow in Two Maize (Zea mays L.) Inbred Lines as Affected by Nitrogen Supply

    PubMed Central

    Niu, Junfang; Chen, Fanjun; Mi, Guohua; Li, Chunjian; Zhang, Fusuo

    2007-01-01

    Background and Aims The influence of two nitrogen (N) levels on growth, water relations, and N uptake and flow was investigated in two different inbred lines of maize (N-efficient Zi330 and N-inefficient Chen94-11) to analyse the differences in N uptake and cycling within a plant. Methods Xylem sap from different leaves of the inbred lines cultured in quartz sand was collected by application of pressure to the root system. Plant transpiration was measured on a daily basis by weighing five pots of each of the treatments. Key Results N-efficient Zi330 had a higher relative growth rate and water-use efficiency at both high (4 mm) and low (0·08 mm) N levels. At a high N level, the amount of N taken up was similar for the two inbred lines; the amount of N transported in the xylem and retranslocated in the phloem was slight greater in Chen94-11 than in Zi330. At a low N level, however, the total amount of N taken up, transported in the xylem and retranslocated in the phloem of Zi330 was 2·2, 2·7 and 2·7 times more, respectively, than that of Chen94-11. Independent of inbred line and N level, the amounts of N transported in the xylem and cycled in the phloem were far more than that taken up by roots at the same time. Low N supply shifted NO3?1 reduction towards the roots. The major nitrogenous compound in the xylem sap was NO3?1, when plants grew at the high N level, while amino acid-N was predominant when plants grew at the low N level. Conclusions The N-efficient maize inbred line Zi330 had a higher ability to take up N and cycle N within the plant than N-inefficient Chen94-11 when grown under N-deficiency. PMID:17088295

  12. A Plant Notices Insect Egg Deposition and Changes Its Rate of Photosynthesis1

    PubMed Central

    Schröder, Roland; Forstreuter, Manfred; Hilker, Monika

    2005-01-01

    Scots pine (Pinus sylvestris) is known to change its terpenoid metabolism in response to egg deposition by the sawfly Diprion pini (Hymenoptera, Diprionidae). Three days after egg deposition, parts of the pine twig adjacent to the egg-laden one are induced to emit volatiles, which attract egg parasitoids. In this study, we investigated whether egg deposition by this sawfly affects pine photosynthesis. Measurements of photosynthesis were taken from untreated control twigs and from pine twigs adjacent to egg-laden ones (i.e. systemically oviposition-induced twigs) for a period of 3 d starting after egg deposition. The net photosynthetic rate of oviposition-induced pine twigs was lower than that of untreated control twigs, whereas the respiration rate of pine twigs was not affected by egg deposition. CO2 response curves of oviposition-induced twigs tended to be lower than those of controls. The potential rate of electron transport (Jmax) and the maximum rate of Rubisco activity (Vcmax) were calculated from the data of the CO2 response curves. Jmax of oviposition-induced twigs was significantly lower than that of controls at day 1 after egg deposition, while the difference diminished from day 2 to day 3. A similar pattern was observed for Vcmax. Light response curves of oviposition-induced twigs were significantly lower than those of untreated ones during 3 d of measurements. Stomatal conductance was slightly lowered by egg deposition. When considering photosynthetic activity as a physiological currency to measure costs of induction of plant defense, the effects of insect egg deposition on gas exchange of pine are discussed with respect to known effects of insect feeding on the photosynthesis activity of plants. PMID:15821143

  13. Effects of drip irrigation configuration and rate on yield and fruit quality of young highbush blueberry plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A 4-year study was conducted to determine the effects of drip configuration and irrigation rate on yield and fruit quality in a new planting of highbush blueberry in British Columbia, Canada. Plants were grown in a silt loam soil on raised beds and were non-irrigated or irrigated using one line of d...

  14. Effect of nitrogen source, rate and time of application on soil nitrogen status and on the characteristics of the plant 

    E-print Network

    Sadik, Mohamed Kamal

    1962-01-01

    EFFECT OF NITROGEN SOURCE, RATE AND TIME OF APPLICATION ON SOIL NITROGEN STATUS AND ON THE CHARACTERISTICS OF THE PLANT By Mohamed K. Sadik A Thesis Submitted to the Graduate School of the Agricultural and Mechanical College of Texxas... in partial, fulfillment of the requirements for the degree of MASTER OF SCIENCE Major Subject: Soil and Plant Sciences May, 1962 EFFECT F NITROGEN SOURCE, RATE AND TIME OF APPLICATION ON SOIL NITROGEN STATUS AND ON THE CHARACTERISTICS OF THE PI ANT' A...

  15. BELGARD EV 2030 ANTISCALANT TESTING AT LOW DOSE RATE IN AL-JUBAIL PH-II PLANT1

    Microsoft Academic Search

    Osman A. Hamed; Ghulam M. Mustafa; Khalid Ba-Mardouf; Hamed Al-Washmi; Fahd A. Al-Shamri; Rashid E. Al-Bunaian; Eid Al-Rowely

    SUMMARY The Research & Development Center (RDC) in collaboration with Al-Jubail plant is embarking upon an ambitious research plan to optimize antiscalant dose rate. Based on the successful pilot plant tests which was carried out at 98oC and a dose rate of antiscalant Belgard EV 2030 at 0.8 ppm, a trial test of Belgard EV 2030 was conducted in Unit

  16. Testing the Growth Rate Hypothesis in Vascular Plants with Above- and Below-Ground Biomass

    PubMed Central

    Yu, Qiang; Wu, Honghui; He, Nianpeng; Lü, Xiaotao; Wang, Zhiping; Elser, James J.; Wu, Jianguo; Han, Xingguo

    2012-01-01

    The growth rate hypothesis (GRH) proposes that higher growth rate (the rate of change in biomass per unit biomass, ?) is associated with higher P concentration and lower C?P and N?P ratios. However, the applicability of the GRH to vascular plants is not well-studied and few studies have been done on belowground biomass. Here we showed that, for aboveground, belowground and total biomass of three study species, ? was positively correlated with N?C under N limitation and positively correlated with P?C under P limitation. However, the N?P ratio was a unimodal function of ?, increasing for small values of ?, reaching a maximum, and then decreasing. The range of variations in ? was positively correlated with variation in C?N?P stoichiometry. Furthermore, ? and C?N?P ranges for aboveground biomass were negatively correlated with those for belowground. Our results confirm the well-known association of growth rate with tissue concentration of the limiting nutrient and provide empirical support for recent theoretical formulations. PMID:22427823

  17. Cyclic variations in nitrogen uptake rate of soybean plants: effects of external nitrate concentration

    NASA Technical Reports Server (NTRS)

    Tolley-Henry, L.; Raper, C. D. Jr; Granato, T. C.; Raper CD, J. r. (Principal Investigator)

    1988-01-01

    Net uptake of NO3- by non-nodulated soybean plants [Glycine max (L.) Merr. cv. Ransom] growing in flowing hydroponic cultures containing 0.5, 1.0 and 10.0 mol m-3 NO3- was measured daily during a 24-d period of vegetative development to determine if amplitude of maximum and minimum rates of net NO3- uptake are responsive to external concentrations of NO3-. Removal of NO3- from the replenished solutions during each 24-h period was determined by ion chromatography. Neither dry matter accumulation nor the periodicity of oscillations in net uptake rate was altered by the external NO3- concentrations. The maxima of the oscillations in net uptake rate, however, increased nearly 3-fold in response to external NO3- concentrations. The maxima and minima, respectively, changed from 4.0 and 0.6 mmol NO3- per gram root dry weight per day at an external solution level of 0.5 mol m-3 NO3- to 15.2 and -2.7 mmol NO3- per gram root dry weight per day at an external solution level of 10.0 mol m-3 NO3-. The negative values for minimum net uptake rate from 10.0 mol m-3 NO3- solutions show that net efflux was occurring and indicate that the magnitude of the efflux component of net uptake was responsive to external concentration of NO3-.

  18. Increase in recombination rate in Arabidopsis thaliana plants sharing gaseous environment with X-ray and UVC-irradiated plants depends on production of radicals.

    PubMed

    Zemp, Franz J; Sidler, Corinne; Kovalchuk, Igor

    2012-07-01

    X-ray and UVC are the two physical agents that damage DNA directly, with both agents capable of inducing double-strand breaks. Some of our recent work has demonstrated that local exposure to UVC results in a systemic increase in recombination frequency, suggesting that information about exposure can be passed from damaged to non-damaged tissue. Indeed, we recently showed that plants sharing the same enclosed environment with UVC-irradiated plants exhibit similar increase in homologous recombination frequency as irradiated plants. Here, we further tested whether yet another DNA-damaging agent, X-ray, is capable of increasing recombination rate (RR) in neighboring plants grown in a Petri dish. To test this, we grew plants exposed to X-ray or UVC irradiation in an enclosed environment next to non-exposed plants. We found that both X-ray and UVC-irradiated plants and neighboring plants exhibited comparable increases in the levels of strand breaks and the RR. We further showed that pre-exposure of plants to radical scavenger DMSO substantially alleviates the radiation-induced increase in RR and prevents formation of bystander signal. Our results suggest that the increase in RR in bystander plants can also be triggered by X-ray and that radicals may play some role in initiation or maintenance of this signal. PMID:22751301

  19. How to help woody plants to overcome drought stress?-a control study of four tree species in Northwest China.

    NASA Astrophysics Data System (ADS)

    Liu, Xiaozhen; Zhang, Shuoxin

    2010-05-01

    Water is essential for plants and involves most physical and chemical processes within their lifecycles. Drought stress is a crucial limiting factor for plant growth and production. 48% of the land in China is arid and semi-arid, and non-irrigated land occupies approximately 51.9% of the total cultivated areas. Therefore, studies on plant drought resistant mechanisms have great significance for improving water use efficiency and thus increasing productivity of economical plants. Prior research has shown that the application of nitrogenous fertilizer affects the drought-resistant characteristics of plants. This study aimed to reveal the effect of nitrogenous fertilizer on physiological aspects and its impact on the drought resistance of four tree species (Robinia pseudoacacia L., Ligustrum lucidum Ait., Acer truncatum Bge. and Ulmus pumila L. ) in northwest China. Three levels of nitrogen fertilization (46% N based of urea adjusted to: 5g/15g soil, 15g/15g soil and 25g/15g soil) and an additional control study were applied to 2-year-old well-grown seedlings under drought conditions (30% field moisture capacity). Stomatal conductance, transpiration rate and net photosynthetic rate were measured by a LI-6400 photosynthesis system, while water use efficiency was calculated from net photosynthesis rate and transpiration rate. The results revealed that as the amount of urea applied was raised, stomatal conductance, transpiration rate and net photosynthetic rate decreased significantly, and thus water use efficiency significantly increased. It is therefore concluded that the application of nitrogenous fertilizer regulated physiological parameters by reducing stomata conductance to improve water use efficiency. In addition, among the four tree species, U. pumila had the maximum value of water use efficiency under the same drought condition. The outcome of this study provides a guided option for forest management in arid and semi-arid areas of northwest China.

  20. Soil water and transpirable soil water fraction variability within vineyards of the Penedès DO (NE Spain) affected by management practices

    NASA Astrophysics Data System (ADS)

    Concepción Ramos, Maria

    2015-04-01

    This work investigated the variability in soil water recorded within the vineyard plots related to soil properties and management practices and its influence on the transpirable sol water fraction. The study was carried out in vineyards in the Penedès Designation of Origin, planted with Chardonnay, with different disturbance degree and with compost treated and untreated areas within the plots. The response in years with different rainfall distributions, included years with extreme situations were evaluated. The main soil types are Typic Xerorthent and Calcixerollic Xerorthent and soil is bare most of the time. Soil water content was measured at different depths using TDR probes. The transpirable soil water fraction was estimated as the ratio between available soil water (ASW) at a given date and the total transpirable soil water (TTSW). TTSW was estimated as the soil water reserve held between an upper and lower limit (respectively, the soil water content near field capacity and soil water content at the end of a dry summer) and integrated over the estimated effective rooting depth. Both minimum and maximum soil water values varied within the plot at all depths. On the surface the minimum values ranged between 4.45 to about 10%, while on deeper layers it ranged between 7.8 and 17.8%. Regarding the maximum value varied between 17.45 and 24.8%. The transpirable soil water fraction for a given year varied significantly within the plot, with differences greater than 20% between the treated and untreated areas. The results were more exacerbated in the driest years an in those with more irregular distribution. Water available has a significant effect on yield. The results indicate the need of using different strategies for water management within the plots.

  1. Meta-analysis of the effects of plant roots in controlling concentrated flow erosion rates

    NASA Astrophysics Data System (ADS)

    Vannoppen, Wouter; Poesen, Jean; Vanmaercke, Matthias; De Baets, Sarah

    2015-04-01

    Vegetation is often used in ecological restoration programs to control various soil erosion processes. During the last two decades several studies reported on the effects of plant roots in controlling concentrated flow erosion rates. However a global analysis of the now available data on root effects is still lacking. Yet, a meta-data analysis will contribute to a better understanding of the soil-root interactions as our capability to assess the effectiveness of roots in reducing soil erosion rates due to concentrated flow in different environments remains difficult. The objectives of this study are therefore i) to provide a state of the art on studies quantifying the effectiveness of roots in reducing soil erosion rates due to concentrated flow; and ii) to explore the overall trends in erosion reduction as a function of the root (length) density, root system architecture and soil texture, based on a global analysis of published research data. We therefore compiled a dataset of measured relative soil detachment rates (RSD) for the root density (RD; 822 observations) as well as the root length density (RLD; 274 observations). Non-linear regression analyses showed that decreases in RSD as a function of RD and RLD could be best described with the Hill curve model. However, a large proportion of the variability in RSD could not be attributed to RD or RLD, resulting in a relatively low predictive accuracy of the Hill curve model with model efficiencies of 0.11 and 0.17 for RD and RLD respectively. Considering root architecture and soil texture yielded a better predictive model especially for RLD with ME of 0.37 for fibrous roots in a non-sandy soil. The unexplained variance is to a large extent attributable to measuring errors and differences in experimental set ups that could not be explicitly accounted for (e.g. tested plant species, soil and flow characteristics). However, using a Monte Carlo simulation approach, we were able to establish relationships that allow assessing the likely erosion-reducing effects of plant roots, while taking these uncertainties into account. Our analyses further showed that compared to RD, RLD is a much more suitable variable to estimate RSD, because it is indirectly correlated to root system architecture.

  2. Plant diversity does not buffer drought effects on early-stage litter mass loss rates and microbial properties.

    PubMed

    Vogel, Anja; Eisenhauer, Nico; Weigelt, Alexandra; Scherer-Lorenzen, Michael

    2013-09-01

    Human activities are decreasing biodiversity and changing the climate worldwide. Both global change drivers have been shown to affect ecosystem functioning, but they may also act in concert in a non-additive way. We studied early-stage litter mass loss rates and soil microbial properties (basal respiration and microbial biomass) during the summer season in response to plant species richness and summer drought in a large grassland biodiversity experiment, the Jena Experiment, Germany. In line with our expectations, decreasing plant diversity and summer drought decreased litter mass loss rates and soil microbial properties. In contrast to our hypotheses, however, this was only true for mass loss of standard litter (wheat straw) used in all plots, and not for plant community-specific litter mass loss. We found no interactive effects between global change drivers, that is, drought reduced litter mass loss rates and soil microbial properties irrespective of plant diversity. High mass loss rates of plant community-specific litter and low responsiveness to drought relative to the standard litter indicate that soil microbial communities were adapted to decomposing community-specific plant litter material including lower susceptibility to dry conditions during summer months. Moreover, higher microbial enzymatic diversity at high plant diversity may have caused elevated mass loss of standard litter. Our results indicate that plant diversity loss and summer drought independently impede soil processes. However, soil decomposer communities may be highly adapted to decomposing plant community-specific litter material, even in situations of environmental stress. Results of standard litter mass loss moreover suggest that decomposer communities under diverse plant communities are able to cope with a greater variety of plant inputs possibly making them less responsive to biotic changes. PMID:23606531

  3. Estimates of deep drainage rates at the U.S. Department of Energy Pantex Plant, Amarillo, Texas

    SciTech Connect

    Fayer, M.J.; Richmond, M.C.; Wigmosta, M.S. [Pacific Northwest National Lab., Richland, WA (United States); Kelley, M.E. [Battelle Environmental Restoration Dept., Columbus, OH (United States)

    1998-04-01

    In FY 1996, the Pacific Northwest National Laboratory (PNNL) provided technical assistance to Battelle Columbus Operations (BCO) in their ongoing assessment of contaminant migration at the Pantex Plant in Amarillo, Texas. The objective of this report is to calculate deep drainage rates at the Pantex Plant. These deep drainage rates may eventually be used to predict contaminant loading to the underlying unconfined aquifer for the Pantex Plant Baseline Risk Assessment. These rates will also be used to support analyses of remedial activities involving surface alterations or the subsurface injection withdrawal of liquids or gases. The scope of this report is to estimate deep drainage rates for the major surface features at the Pantex Plant, including ditches and playas, natural grassland, dryland crop rotation, unvegetated soil, and graveled surfaces. Areas such as Pantex Lake that are outside the main plant boundaries were not included in the analysis. All estimates were derived using existing data or best estimates; no new data were collected. The modeling framework used to estimate the rates is described to enable future correlations, improvements, and enhancements. The scope of this report includes only data gathered during FY 1996. However, a current review of the data gathered on weather, soil, plants, and other information in the time period since did not reveal anything that would significantly alter the results presented in this report.

  4. Effects of atmospheric humidity on net photosynthesis, transpiration, and stomatal resistance

    NASA Astrophysics Data System (ADS)

    Overdieck, D.; Strain, B. R.

    1981-03-01

    Rhizomes of Hydrocotyle plants from three contrasting habitats were cloned and the ramets grown under controlled environmental conditions. Measurements of net photosynthesis, transpiration, and total leaf diffusion resistance were used to examine possible physiological adaptations to specific field environments. Increasing dryness of the growth chamber environment had large effects on gas exchange (CO2 and water vapor) and on total diffusion resistance of plants from a pond, moderate effects on plants from a mesic forest, but plants from a coastal sand dune were unaffected by the experimentally imposed dryness. Thus the 3 Hydrocotyle types demonstrated adaptive physiological reponses to their specific field habitats. Periodic stomatal oscillations were induced in ramets from the pond by sharply increasing irradiance, but the adaptiveness of the oscillations cannot be determined with the evidence at hand. No stomatal closure could be induced by atmospheric dryness alone as long as soil and plant dessication were prevented. There were no observable differences in stomatal response to increasing atmospheric vapor pressure deficits.

  5. Transpiration cooled electrodes and insulators for MHD generators

    DOEpatents

    Hoover, Jr., Delmer Q. (Churchill Boro, PA)

    1981-01-01

    Systems for cooling the inner duct walls in a magnetohydrodynamic (MHD) generator. The inner face components, adjacent the plasma, are formed of a porous material known as a transpiration material. Selected cooling gases are transpired through the duct walls, including electrically insulating and electrode segments, and into the plasma. A wide variety of structural materials and coolant gases at selected temperatures and pressures can be utilized and the gases can be drawn from the generation system compressor, the surrounding environment, and combustion and seed treatment products otherwise discharged, among many other sources. The conduits conducting the cooling gas are electrically insulated through low pressure bushings and connectors so as to electrically isolate the generator duct from the ground.

  6. How to fit nonlinear plant growth models and calculate growth rates: an update for ecologists

    Microsoft Academic Search

    Charles Eliot Timothy Paine; Toby R. Marthews; Deborah R Vogt; Mark Rees; Drew W. Purves; Andy Hector; Lindsay A. Turnbull

    2011-01-01

    1) Plant growth is a fundamental ecological process, integrating across scales from physiology to community dynamics and ecosystem properties. Recent improvements in plant growth modeling have allowed deeper understanding and more accurate predictions for a wide range of ecological issues, including competition among plants, plant-herbivore interactions and ecosystem functioning. 2) One challenge in modeling plant growth is that, for a

  7. Estimation of the rate of increase in nitrogen dioxide concentrations from power plant stacks using an imaging-DOAS.

    PubMed

    Lee, Hanlim; Kim, Young J; Lee, Chulkyu

    2009-05-01

    The emission of nitrogen compounds from power plants accounts for a significant proportion of the total emissions of nitrogen to the atmosphere. This study seeks to understand the nature of chemical reactions in the atmosphere involving nitrogen, which is important in undertaking quantitative assessments of the contribution of such reactions to local and regional air pollution. The slant column density (SCD) of power-plant-generated NO(2) was derived using imaging differential optical absorption spectroscopy (I-DOAS) with scattered sunlight as a light source. The vertical structure of NO(2) SCD from power plant stacks was simultaneously probed using a pushbroom sensor. Measured SCDs were converted to mixing ratios in calculating the rate of NO(2) increase at the center of the plume. This study presents quantitative measurements of the rate of NO(2) increase in a rising plume. An understanding of the rate of NO(2) increase is important because SO(2) and NO(x) compete for the same oxidizing radicals, and the amount of NO(x) is related to the rates of SO(2) oxidation and sulfate formation. This study is the first to directly obtain the rate of NO(2) increase in power plant plumes using the I-DOAS technique. NO(2) increase rates of 60 and 70 ppb s(-1) were observed at distances of about 45 m from the two stacks of the Pyeongtaek Power Plant, northwest South Korea. PMID:18535919

  8. Nighttime transpiration observed over a larch forest in Hokkaido, Japan

    Microsoft Academic Search

    N. Kobayashi; T. Hiyama; Y. Fukushima; M. L. Lopez; T. Hirano; Y. Fujinuma

    2007-01-01

    Nighttime transpiration in a larch forest in northern Japan was investigated using concurrent measurements of the energy budget below and above the canopy and sap flow velocities. Upward latent heat flux (lE) above the canopy was observed on ?20% of nights during the growing season. Nighttime lE was ?7% of daily totals during the dry season (September–October) and averaged ?3%

  9. DSMC Simulation of thermal transpiration and accomodation pumps

    SciTech Connect

    Hudson, M.L.; Bartel, T.J.

    1998-11-01

    The Direct Simulation Monte Carlo (DSMC) technique is employed to evaluate several configurations of thermal transpiration and accommodation pumps. There is renewed interest in these rarefied flow pumping concepts for Micro-Electro-Mechanical Systems (MEMS) due to advances in micro-fabrication. The simulation results are compared with existing data to understand gas-surface interaction uncertainties in the experiments. Parametric studies are performed to determine the effects of Knudsen number and surface temperature and roughness on the maximum pump pressure ratio.

  10. Transpiration of cottonwood\\/willow forest estimated from sap flux

    Microsoft Academic Search

    Sean M. Schaeffer; David G. Williams; David C. Goodrich

    2000-01-01

    Cottonwood\\/willow forests in the American Southwest consist of discrete, even-aged vegetation patches arranged in narrow strips along active and abandoned stream channels of alluvial flood plains. We used the heat-pulse velocity technique in this study to estimate transpiration in 12 such forest patches along a perennially flowing reach of the San Pedro River in southeastern Arizona, USA during five periods

  11. Urban tree transpiration over turf and asphalt surfaces

    NASA Astrophysics Data System (ADS)

    Kjelgren, Roger; Montague, Thayne

    We used a two-layer canopy model to study transpiration of tree species as affected by energy-balance properties of a vegetated and paved surface. During several dawn-to-dusk studies, tree transpiration, stomatal conductance, leaf temperature (T l), and several microclimate variables, were measured over turf and an asphalt surface. Cumulative transpiration was estimated from a leaf energy-balance equation applied to a tree crown apportioned between sunlit and shaded layers. Afternoon asphalt surface temperatures ( Ts) were 20-25°C higher than turf Ts in all studies. Air-temperature differences between sites were minimal due to the size and proximity of the two surfaces that resulted in mixing of air. Trees over asphalt had consistently higher T, than those over turf, apparently due to interception of the greater upwards long-wave radiation flux from higher Tl. In one study flowering pear over asphalt in a humid environment bad higher Tl resulting in one-third more total water loss compared to trees over turf. In other studies, however, water loss of green ash and Norway maple over asphalt in an arid environment was either equal to or less than that over turf. Less water loss was due to higher Tl over asphalt causing prolonged stomatal closure. Model manipulation indicated that tree water loss over asphalt will depend on the degree of stomatal closure resulting from how interception of increased energy-fluxes and ambient humidity affect leaf-to-air vapor pressure differences.

  12. Development of saline ground water through transpiration of sea water.

    PubMed

    Fass, T; Cook, P G; Stieglitz, T; Herczeg, A L

    2007-01-01

    As vegetation usually excludes salt during water uptake, transpiration will increase the salinity of the residual water. If the source water is sea water, then the residual water may become highly saline. In the unconfined coastal aquifer of the tropical Burdekin River delta, northeastern Australia, areas of highly saline ground water with chloride concentrations up to almost three times that of sea water occur up to 15 km from the present coastline, and are attributed to transpiration by mangrove vegetation during periods of high sea level. Radiogenic ((14)C) carbon isotope analyses indicate that ground water with chloride concentrations between 15,000 and 35,000 mg/L is mostly between 4000 and 6000 years old, at which time sea level was 2 to 3 m higher than present. Stable isotope analyses of oxygen-18 and deuterium show no evidence for evaporative enrichment of this water. Oxygen-18, deuterium, and stable (delta(13)C) carbon isotope analyses of ground water and soil water point to a recharge environment beneath the mangrove forests during this postglacial sea level high stand. During that period, transpiration of the mangrove forests would have led to high chloride concentrations in the residual ground water, without inducing isotopic fractionation. Due to the higher density, this hypersaline water moved downward through the aquifer by gravity and has formed lenses of highly saline ground water at the bottom of the unconfined aquifer. PMID:17973748

  13. Transpiration and water use efficiency in native chilean and exotic species, a usefull tool for catchment management?

    NASA Astrophysics Data System (ADS)

    Hervé-Fernández, P.; Oyarzun, C. E.

    2012-04-01

    Land-use and forest cover change play important roles in socio-economic processes and have been linked with water supply and other ecosystem services in various regions of the world. Water yield from watersheds is a major ecosystem service for human activities but has been altered by landscape management superimposed on climatic variability and change. Sustaining ecosystem services important to humans, while providing a dependable water supply for agriculture and urban needs is a major challenge faced by managers of human-dominated or increased antropical effect over watersheds. Since water is mostly consumed by vegetation (i.e: transpiration), which strongly depends on trees physiological characteristics (i.e: foliar area, transpiration capacity) are very important. The quantity of water consumed by plantations is influenced mainly by forest characteristics (species physiology, age and management), catchment water retention capacity and meteorological characteristics. Eventhough in Chile, the forest sector accounts for 3.6% of the gross domestic product (GDP) and 12.5% of total exports (INFOR, 2003), afforestation with fast growing exotic species has ended up being socially and politically questionable because of the supposed impact on the environment and water resources. We present data of trees transpiration and water use efficiency from three headwater catchments: (a) second growth native evergreen forest (Aetoxicon punctatum, Drimys winterii, Gevuina avellana, Laureliopsis philippiana); (b) Eucalyptus globulus plantation, and (c) a mixed native deciduous (Nothofagus obliqua and some evergreen species) forest and Eucalyptus globulus and Acacia melanoxylon plantation located at the Coastal Mountain Range in southern Chile (40°S). Annual transpiration rates ranged from 1.24 ± 0.41 mol•m-2•s-1 (0.022 ± 0.009 L•m-2•s-1) for E. globulus, while the lowest observed was for L. philippiana 0.44 ± 0.31 mol•m-2•s-1 (0.008 ± 0.006 L•m-2•s-1). However water use efficiency for E. globulus, was the lowest observed (6.78 ± 8.92 ?mol•mol-1) compared to native species, 7.45 ± 4.41 ?mol•mol-1 for A. punctatum which showed the lowest value (p < 0.05). Preliminary results show, that the E. globulus has the highest transpiration rate, but the lowest water use efficiency values, compared to native evergreen and deciduous species. Nevertheless E. globulus showed the highest photosyntethic rate values, which finally traduces that E. globulus is a fast growing, big water drinker but it's less efficient than most native trees used in this experiment. Acknowledges This research has been supported by FONDECYT 1090345. Mr. Hervé-Fernández wishes to thank BECAS CHILE for his scholarship.

  14. Microclimatological and Physiological Controls of Stomatal Conductance and Transpiration of Co-Occurring Seedlings with Varying Shade Tolerance

    NASA Astrophysics Data System (ADS)

    Siegert, C. M.; Levia, D. F.

    2010-12-01

    Forest ecosystems provide a significant portion of fresh water to the hydrologic cycle through transpiration, the majority of which is supplied by saplings and mature trees. However, a smaller, yet measurable, proportion is also supplied by seedlings. The contribution of seedlings is dependent upon physiological characteristics of the species, whose range of habitat is ultimately controlled by microclimate. The objectives of this study were to (1) observe meteorological conditions of two forest microlimates and (2) assess the intra- and interspecific stomatal conductance and transpiration responses of naturally occurring seedlings of varying shade tolerance. Naturally established seedlings in a deciduous forest understory and an adjacent clearing were monitored throughout the 2008 growing season in southeastern Pennsylvania (39°49'N, 75°43'W). Clear spatial and temporal trends of stomatal conductance and transpiration were observed throughout this study. The understory microclimate conditions overall had a lower degree of variability and had consistently lower mean quantum flux density, air temperature, vapor pressure deficit, volumetric water content, and soil temperature than the clearing plot. Shade tolerant understory seedlings (Fagus grandifolia Ehrh. (American beech) and Prunus serotina L. (black cherry)) had significantly lower mean monthly rates of water loss (p = 0.05) than shade intolerant clearing seedlings (P. serotina and Liriodendron tulipifera L. (yellow poplar)). Additionally, water loss by shade grown P. serotina was significantly lower (p = 0.05) than by sun grown P. serotina. Significant intraspecific responses (p = 0.05) were also observed on a monthly basis, with the exception of L. tulipifera. These findings indicate that physiological differences, specifically shade tolerance, play an important role in determining rates of stomatal conductance and transpiration in tree seedlings. To a lesser degree, microclimate variability was also shown to influence rates stomatal conductance and transpiration (3.6% and 7.8% in the understory and 8.2% and 23.2% in the clearing, respectively). Field validations are critical to developing better models and forest management strategies and therefore the results of this study may serve to validate those obtained in previous studies conducted largely under controlled conditions.

  15. Ozone uptake and effects on transpiration, net photosynthesis, and dark respiration in Scots pine. [Pinus sylvestris L

    SciTech Connect

    Skaerby, L.; Troeng, E.; Bostroem, C.

    1987-09-01

    Ozone uptake, transpiration, net photosynthesis, and dark respiration were studied in the field by using an open gas exchange system in a 20-year-old stand of Scots pine (Pinus sylvestris L.). A current shoot was treated with ozone concentrations ranging from 120 to 400 ..mu..g x m/sup -3/ during one month. During daytime there was a linear relationship between ozone concentration and ozone uptake, and the deposition rate varied between 0.05 and 0.13 cm x s/sup -1/. Ozone at the highest concentrations seemed to decrease transpiration somewhat during daytime. At night, ozone was taken up only at the highest concentration. Both transpiration and stomatal conductance increased at night when ozone concentration was 250..mu..g x m/sup -3/ and higher. There was no significant influence on the net photosynthetic performance during exposure to ozone. Dark respiration, however, increased throughout the experimental period, and the accumulated respiration was about 60% higher for the ozone-exposed shoot at the end of the experiment.

  16. A High-Rate Secondary Treatment Based on a Moving Bed Bioreactor and Multimedia Filters for Small Wastewater Treatment Plants

    Microsoft Academic Search

    Z. Liao; V. Rasmussen; H. Ødegaard

    2003-01-01

    For small wastewater treatment plants (WWPTs), high-rate secondary treatment systems with good treatment efficiency and easy, stable, and robust operation are called for. In this paper an experimental study on a high rate secondary treatment based on moving bed biofilm reactor (MBBR) and multimedia filters is presented. A high rate MBBR converts easily biodegradable SCOD in short HRT (0.5 h) directly

  17. Contrasting roles of interception and transpiration in the hydrological cycle

    NASA Astrophysics Data System (ADS)

    van der Ent, R.; Wang-Erlandsson, L.; Keys, P.; Savenije, H.

    2013-12-01

    The contribution of land evaporation to local and remote precipitation (i.e., moisture recycling) has been extensively studied and is found to be of significant importance for water resources, agriculture and ecosystems. Our paper is the first research to present moisture recycling metrics for partitioned evaporation. We use a new land surface model (STEM) to compute land evaporation partitioned into canopy and ground interception (i.e., the fast feedbacks), and transpiration and open water evaporation (i.e., the slow feedbacks). We also use a numerical moisture tracking model (WAM-2layers, with atmospheric variables taken from ERA-Interim) to track the components of land evaporation separately, backward as well as forward in time. Moreover, we include age tracers to study the lifetime of these components. The origin and fate of the fast and slow vapor feedbacks appear to be very different. Global maps indicate that evaporated interception is more likely to return as precipitation on land than transpired water. On average, evaporation from interception is found to have an atmospheric residence time of nine days, while transpiration typically resides ten days in the atmosphere. In the figure it can be seen that interception evaporation recycling has much shorter length scales than transpiration evaporation recycling, thus interception generally precipitates closer to its evaporative source. We conclude that interception mainly works as an intensifier of the local hydrological cycle during wet spells. On the other hand, transpiration is very active during dry spells and is transported over much larger distances downwind where it can act as an important source of moisture, especially during the onset and decline of the rainy period. Land use changes (e.g., forest to cropland conversion) were already known to have an impact on the magnitude of moisture recycling, but here we show that even when total annual evaporation remains equal, a different partitioning will result in different moisture recycling patterns and hence a redistribution of water resources. As such, this research highlights that land use changes can have complex effects on the atmospheric part of the hydrological cycle.

  18. Cyclic variations in nitrogen uptake rate in soybean plants: uptake during reproductive growth

    NASA Technical Reports Server (NTRS)

    Vessey, J. K.; Raper, C. D. Jr; Henry, L. T.; Raper CD, J. r. (Principal Investigator)

    1990-01-01

    Net uptake of NO3- by non-nodulated soybean plants [Glycine max (L.) Merr. cv. Ransom] growing in flowing hydroponic culture was measured daily during a 63 d period of reproductive development between the first florally inductive photoperiod and [unknown word] seed growth. Removal of NO3- from a replenished solution containing 1.0 mol m-3 NO3- was determined by ion chromatography. Uptake of NO3- continued throughout reproductive development. The net uptake rate of NO3- cycled between maxima and minima with a periodicity of oscillation of 3 to 7 d during the floral stage and about 6 d during the fruiting stage. Coupled with increasing concentrations of carbon and C : N ratios in tissues, the oscillations in net uptake rates of NO3- are evidence that the demand for carbohydrate by reproductive organs is contingent on the availability of nitrogen in the shoot pool rather than that the demand for nitrogen follows the flux of carbohydrate into reproductive tissues.

  19. Effect of salinity on water relations of wild barley plants differing in salt tolerance

    PubMed Central

    Vysotskaya, Lidia; Hedley, Peter E.; Sharipova, Guzel; Veselov, Dmitry; Kudoyarova, Guzel; Morris, Jennifer; Jones, Hamlyn G.

    2010-01-01

    Background and aims Certain lines of wild barley (Hordeum spontaneum) are more tolerant of salinity than others. The physiological basis of this difference is examined in a comparative study of a saline-tolerant and saline-intolerant line that emphasizes plant water relations. Methodology Effects of salt-treatment (75 mM maximum) extending from a few hours to 3 weeks were quantified in 8-day-old seedlings of a saline-sensitive wild barley line (‘T-1’) and a less saline-sensitive line (‘20-45’). Plants were grown in nutrient culture. Levels of mRNA of the HtPIP2;4 aquaporin (AQP) gene were determined together with a range of physiological responses including root hydraulic conductivity, osmotic potential of root xylem sap, transpiration, leaf relative water content, root water content, leaf water potential, leaf sap osmolality, leaf length, leaf area and chlorophyll content. Principal results Salt treatment inhibited transpiration and hydraulic conductivity more in salt-tolerant ‘20-45’ plants than in salt-sensitive ‘T-1’. In ‘20-45’, the effect was paralleled by a fast (within a few hours) and persistent (3 days) down-regulation of aquaporin. In salt-sensitive ‘T-1’ plants, aquaporin down-regulation was delayed for up to 24 h. Greater tolerance in ‘20-45’ plants was characterized by less inhibition of leaf area, root fresh weight, leaf water content and chlorophyll concentration. Leaf water potentials were similar in both lines. Conclusions (i) Decline in hydraulic conductivity in salt-treated barley plants is important for stomatal closure, (ii) lowered transpiration rate is beneficial for salt tolerance, at least at the seedling stage and (iii) changes in AQP expression are implicated in the control of whole plant hydraulic conductivity and the regulation of shoot water relations. PMID:22476064

  20. Evaluation of transpiration in a Douglas-fir stand by means of sap flow measurements

    Microsoft Academic Search

    A. GRANIER

    1987-01-01

    Transpiration of a Douglas-fir (Pseudorsuga menziesii (Mirb.) France) stand was evaluated by sap flow measurements during a 4-month period. Between-tree variation in sap flow depended on crown class. On a sunny day, total transpiration was 1.6, 8.0 and 22.0 liters day-' for suppressed, codomi- nant and dominant trees, respectively. Transpiration estimated by sap How fell below potential evapotranspiration when available

  1. Visitation rates and pollinator sets at the periphery and central parts of single-species plant patches

    Microsoft Academic Search

    S. N. Lysenkov

    2009-01-01

    Three model plant species (Aegopodium podagraria, Tripleurospermum inodorum, and Geranium palustri) were used to show the differences in visitation rates and pollinator sets between plant individuals growing at the center\\u000a and periphery of single-species patches. Most of the insect species visited the center more frequently, but Phaonia basalis (Diptera, Muscidae) and Leptura flava (Coleoptera, Cerambycidae) preferred the peripheral parts. The

  2. NRES 725 PLANT PHYSIOLOGICAL ECOLOGY Reading List Water Balance of Plants

    E-print Network

    Nowak, Robert S.

    1 NRES 725 ­ PLANT PHYSIOLOGICAL ECOLOGY Fall 2008 Reading List ­ Water Balance of Plants I) Water Balance of Plants A) Water potential B) Soil, plant, air continuum C) Physiological control 1) Roots and water uptake 2) Hydraulic conductivity 3) Stomatal conductance and transpiration Recommended Kirkham (05

  3. Evaporation, transpiration, and ecosystem water use efficiency in a multi-annual sugarcane production system in Hawai'i, USA

    NASA Astrophysics Data System (ADS)

    Anderson, R. G.; Tirado-corbala, R.; Wang, D.; Ayars, J. E.

    2013-12-01

    Food and biofuel production will require practices that increase water use efficiency in order to have future sustainability in a water-constrained environment. One possible practice is the use of food and energy crops with multi-annual growing periods, which could reduce bare soil evaporation. We integrated field water budgets, micrometeorology, and plant sampling to observe plant growth and evapotranspiration (ET) in two sugarcane (Saccharum officinarum L.) fields in Hawai'i, USA in contrasting environments with unusually long (18-24 month) growing periods. We partitioned observed ET into evaporation and transpiration using a flux partitioning model and calculated ecosystem water use efficiency (EWUE=Net Ecosystem Productivity/ET) and harvest WUE (HWUE=Aboveground Net Ecosystem Productivity/ET) to assess sugarcane water use efficiency. After the start of the mid-period, our higher elevation, less windy field ('Lee') had a slightly higher mean EWUE (31.5 kg C ha-1 mm-1) than our lower elevation, windier ('Windy') field (mean EWUE of 30.7 kg C ha-1 mm-1). HWUE was also very high (HWUE >27 kg C ha-1 mm-1) in both fields due to aboveground biomass composing >87% of total biomass. Transpiration, as a fraction of total ET, increased rapidly with canopy cover in both fields; during the mid-period, transpiration was an average of 84% of total ET in Windy and 80% in Lee, with Lee showing greater variation than Windy. As expected, daily EWUE increased with canopy cover during the initial growing stages; more significantly, EWUE showed no substantial decrease during the 2nd year with an aging crop. The results illustrate the potential for longer-rotation crop cycles for increasing water use efficiency, particularly in tropical regions.

  4. Transpiration cooling in the locality of a transverse fuel jet for supersonic combustors

    NASA Technical Reports Server (NTRS)

    Northam, G. Burton; Capriotti, Diego P.; Byington, Carl S.

    1990-01-01

    The objective of the current work was to determine the feasibility of transpiration cooling for the relief of the local heating rates in the region of a sonic, perpendicular, fuel jet of gaseous hydrogen. Experiments were conducted to determine the interaction between the cooling required and flameholding limits of a transverse jet in a high-enthalpy, Mach 3 flow in both open-jet and direct-connect test mode. Pulsed shadowgraphs were used to illustrate the flow field. Infrared thermal images indicated the surface temperatures, and the OH(-) emission of the flame was used to visualize the limits of combustion. Wall, static presures indicated the location of the combustion within the duct and were used to calculate the combustion efficiency. The results from both series of tests at facility total temperatures of 1700 K and 2000 K are presented.

  5. Tomato fruit cuticular waxes and their effects on transpiration barrier properties: functional characterization of a mutant deficient in a very-long-chain fatty acid  -ketoacyl-CoA synthase

    Microsoft Academic Search

    Gerd Vogg; Stephanie Fischer; Jana Leide; Eyal Emmanuel; Reinhard Jetter; Avraham A. Levy; Markus Riederer

    2004-01-01

    Cuticular waxes play a pivotal role in limiting tran- spirational water loss across the plant surface. The correlation between the chemical composition of the cuticular waxes and their function as a transpiration barrier is still unclear. In the present study, intact tomato fruits (Lycopersicon esculentum) are used, due to their astomatous surface, as a novel integra- tive approach to investigate

  6. Plants

    NSDL National Science Digital Library

    Miss Berneski

    2011-12-10

    Get ready to explore plants! Let's Learn About Plants! Question: What do plants need to live? Watch the video to find out! What does it need to grow? Question: What are the parts of a plant? Click to find out! Parts of a Plant Question: What is the life cycle of a plant? Watch the video to find out! Plant Life Cycle Video Question: ...

  7. Partitioning of Latent Heat Flux between Transpiration and Direct Evaporation

    NASA Astrophysics Data System (ADS)

    Wang, W.; Ramamurthy, P.; Baeck, M. L.; Bou-Zeid, E.; Scanlon, T. M.; Smith, J. A.

    2013-12-01

    The characterization of land surface fluxes is critical to enhancing our understanding of the water cycle and regional climate. The partitioning of available energy into sensible and latent heat fluxes (H and LE), as well as the partitioning of latent heat flux into vegetation transpiration (Et) and bare soil evaporation (Ed), are key elements of biosphere-atmosphere interactions. In this study empirical analyses and numerical modeling studies are carried out for a suburban grass site in Princeton NJ, focusing on a two year period from 2011 - 2013. Measurements from an Eddy-Covariance station play a central role in both empirical analyses and modeling studies. Two methods are used to partition latent heat flux into direct evaporation and transpiration components: flux similarity partitioning and partitioning based on the Penman-Monteith formulation in the Noah Land Surface Model (LSM). The former takes 10Hz water vapor and CO2 flux measurements as input, assuming that the water vapor (q) / CO2 (c)flux pair from stomatal processes (transpiration and photosynthesis) is perfectly negatively correlated. Any deviation of the correlation from -1 is contaminated by the perfect positive correlation of the q c flux pair from non-stomatal processes (soil evaporation and respiration). Thus LE can be partitioned into Et and Ed by analyzing the q c correlation. The latter method is based on a commonly used physics-based model which takes fundamental forcing time series as input, using Penman-Monteith equation. We characterize the seasonal and diurnal partitioning of latent heat flux based on flux similarity analyses and compare these results to partitioning based on Noah LSM simulations. We use wavelet decomposition to examine scale-dependent properties of latent heat flux partitioning and present sensitivity analyses of Noah LSM flux partitioning to model parameters. We also present results from a water vapor isotope analyzer that was developed with the goal of providing an empirical measurement of the Et and Ed flux components.

  8. A Rating of Plants with Reference to their Relative Resistance or Susceptibility to Phymatotrichum Root Rot. 

    E-print Network

    Taubenhaus, J. J. (Jacob Joseph); Ezekiel, Walter N. (Walter Naphtali)

    1936-01-01

    Pesticide-free refuge plantings of sunflower, kale and collards were created in association with other plants to provide habitats for the conservation of parasitic Hymenoptera attacking silverleaf whitefly (SWF), Bemisia ...

  9. A contribution of groundwater to Mojave Desert shrub transpiration

    SciTech Connect

    Hunter, R.B.

    1988-12-31

    Soil moisture was measured to 1-m depths in the northern Mojave Desert on two plots, one of which was denuded of shrubs. The pattern of wetting-drying near the surface and below the depth wet by rainfall suggested roughly 2 mm per month of transpired water was supplied by percolation upward from below the root zone. This deep moisture built up during fall and winter and depleted in spring and summer, which correlates well with local shrub phenology. 10 refs., 3 figs.

  10. Control and Augmentation of Passive Porosity through Transpiration Control

    NASA Technical Reports Server (NTRS)

    Banks, Daniel W. (Inventor); Wood, Richard M. (Inventor); Bauer, Steven X. S. (Inventor)

    1999-01-01

    A device for controlling pressure loading of a member caused by a fluid moving past the member or the member moving through a fluid. The device consists of a porous skin mounted over the solid surface of the member and separated from the solid surface by a plenum. Fluid from an area exerting high pressure on the member may enter the plenum through the porous surface and exit into an area exerting a lower pressure on the member, thus controlling pressure loading of the member. A transpirational control device controls the conditions within the plenum thus controlling the side force and yaw moment on the forebody.

  11. Effect of kinetic boundary condition on the thermal transpiration coefficient

    NASA Astrophysics Data System (ADS)

    Sugimoto, Hiroshi; Amakawa, Kenjiro

    2014-12-01

    The effect of kinetic boundary condition on the free molecular thermal transpiration coefficient ? is analyzed numerically. The Maxwell model boundary condition is applied in its original form in the sense that its accommodation coefficient depends on the speed of incident molecules. The results show that the value of ? depends much on the velocity dependency of the accommodation coefficient. The experimental result, ? < 0.5, can be reproduced if the grazing molecules reflect diffusely. This makes a sharp contrast with the previous works that ? =0.5 for the velocity independent accommodation coefficient.

  12. Transpiration and hydraulic strategies in a piñon-juniper woodland.

    PubMed

    West, A G; Hultine, K R; Sperry, J S; Bush, S E; Ehleringer, J R

    2008-06-01

    Anthropogenic climate change is likely to alter the patterns of moisture availability globally. The consequences of these changes on species distributions and ecosystem function are largely unknown, but possibly predictable based on key ecophysiological differences among currently coexisting species. In this study, we examined the environmental and biological controls on transpiration from a piñon-juniper (Pinus edulis-Juniperus osteosperma) woodland in southern Utah, USA. The potential for climate-change-associated shifts in moisture inputs could play a critical role in influencing the relative vulnerabilities of piñons and junipers to drought and affecting management decisions regarding the persistence of this dominant landscape type in the Intermountain West. We aimed to assess the sensitivity of this woodland to seasonal variations in moisture and to mechanistically explain the hydraulic strategies of P. edulis and J. osteosperma through the use of a hydraulic transport model. Transpiration from the woodland was highly sensitive to variations in seasonal moisture inputs. There were two distinct seasonal pulses of transpiration: a reliable spring pulse supplied by winter-derived precipitation, and a highly variable summer pulse supplied by monsoonal precipitation. Transpiration of P. edulis and J. osteosperma was well predicted by a mechanistic hydraulic transport model (R2 = 0.83 and 0.92, respectively). Our hydraulic model indicated that isohydric regulation of water potential in P. edulis minimized xylem cavitation during drought, which facilitated drought recovery (94% of pre-drought water uptake) but came at the cost of cessation of gas exchange for potentially extended periods. In contrast, the anisohydric J. osteosperma was able to maintain gas exchange at lower water potentials than P. edulis but experienced greater cavitation over the drought and showed a lesser degree of post-drought recovery (55% of pre-drought uptake). As a result, these species should be differentially affected by shifts in the frequency, duration, and intensity of drought. Our results highlight the sensitivity of this woodland type to potential climate-change-associated shifts in seasonal moisture patterns and demonstrate the utility of mechanistic hydraulic models in explaining differential responses of coexisting species to drought. PMID:18536252

  13. Fruit calcium accumulation coupled and uncoupled from its transpiration in kiwifruit.

    PubMed

    Montanaro, Giuseppe; Dichio, Bartolomeo; Lang, Alexander; Mininni, Alba N; Xiloyannis, Cristos

    2015-06-01

    Accumulation of Ca in several fleshy fruit is often supposed to depend, among others, by climatic variables driving fruit transpiration. This study tests the whole causal chain hypothesis: VPD?fruit transpiration?Ca accumulation. Also there are evidences that relationship between fruit transpiration and Ca content is not always clear, hence the hypothesis that low VPD reduces the fraction of xylemic water destined to transpiration was tested by examining the water budget of fruit. Attached fruits of Actinidia deliciosa were subjected to Low (L) and High (H) VPD. Their transpiration was measured from early after fruit-set to day 157 after full bloom (DAFB). Fruits were picked at 70, 130 and 157 DAFB for Ca and K determinations and for water budget analysis. Cumulative transpired water was ?70g and ?16gH2Of(-1) in HVPD and LVPD, respectively. Calcium accumulated linearly (R(2)=0.71) with cumulative transpiration when VPD was high, while correlation was weaker (R(2)=0.24) under LVPD. Under low VPD the fraction of xylem stream destined to transpiration declined to 40-50%. Results suggest that Ca accumulation is coupled to cumulative transpiration under high VPD because under that condition cumulative transpiration equals xylem stream (which carry the nutrient). At LVPD, Ca gain by fruit is uncoupled from transpiration because ?60% of the xylemic water is needed to sustain fruit growth. Results will apply to most fruits (apples, tomatoes, capsicum, grapes etc.) since most suffer Ca deficiency disorders and grow in changing environments with variable VPD, also they could be supportive for the implementation of fruit quality models accounting also for mineral compositions and for a reinterpretation of certain field practices aimed at naturally improve fruit Ca content. PMID:25982084

  14. Responses of transpiration and photosynthesis to reversible changes in photosynthetic foliage area in western red cedar (Thuja plicata) seedlings.

    PubMed

    Pepin, S; Livingston, N J; Whitehead, D

    2002-04-01

    Experiments were conducted on 1-year-old western red cedar (Thuja plicata Donn.) seedlings to determine the response of illuminated foliage to reversible changes in total photosynthetic foliage area (L(A)). Reductions in L(A) were brought about by either shading the lower foliage or by reducing the ambient CO2 concentration (c(a)) of the air surrounding the lower part of the seedling. In the latter case, the vapor pressure was also changed so that transpiration rates (E) could be manipulated independently of photosynthetic rates (A). We hypothesized that following such treatments, short-term compensatory changes would occur in stomatal conductance (g(s)) and A of the remaining foliage. These changes would occur in response to hydraulic signals generated by changes in the water potential gradient rather than changes in the distribution of sources and sinks of carbon within the seedling. When a portion of the foliage was shaded, there was an immediate reduction in whole-seedling E and a concomitant increase in g(s), A and E in the remaining illuminated foliage. However, the intercellular CO2 concentration did not change. These compensatory effects were fully reversed after the shade was removed. When the lower foliage A was reduced to < 0 micromol m-2 s-1, by shading or lowering c(a), and E was either unchanged or increased (by adjusting the vapor pressure deficit), there was no significant increase in g(s) and A in the remaining foliage. We conclude that compensatory responses in illuminated foliage occur only when reductions in L(A) are accompanied by a reduction in whole-plant E. The relationship between the reduction in whole-seedling E and the increase in A is highly linear (r2 = 0.68) and confirms our hypothesis of the strong regulation of g(s) by hydraulic signals generated within the seedling. We suggest that the mechanism of the compensatory effects is a combination of both increased CO2 supply, resulting from increased g(s), and a response of the rate of carboxylation, possibly related to the activity of Rubisco. PMID:11960761

  15. Continuous Observations of Leaf Transpiration Isotopic Composition in Two Dryland Species Highlight Sensitivity to Changes in Irradiance and Soil Water Content.

    NASA Astrophysics Data System (ADS)

    Wayland, H.; Caylor, K. K.

    2014-12-01

    Advances in optical isotope techniques have enabled near-continuous determination of leaf transpiration isotopic composition (?T), allowing researchers to trace water movement through the soil-plant-atmosphere continuum at fine temporal scales. However, to date very few direct measurements of ?T are available. We applied a novel flow-through chamber method developed by Wang et al. (2011) to monitor short-term variability in leaf transpired water isotopic composition of two African savanna trees, Vachiella tortillis and Senegalia mellifera, in response to variable irradiance and soil water content. Single leaves were inserted into a custom cuvette connected to an off-axis integrated cavity output spectroscopy (IA-ICOS) water vapor isotope analyzer and allowed to reach isotopic steady-state. Measurements were taken on alternating species every 10 minutes for two hours during mid-morning when plants were most active. Above-canopy irradiance and soil moisture at rooting depth were recorded daily at 1- and 10-minute intervals, respectively. We found that shading initiated rapid depletion of ?2H and ?18O in both species, though differences were more pronounced in V. tortillis. Similarly, an increase in irradiance caused ?18O enrichment of transpired water by up to 5‰ on the order of minutes. Interestingly, soil water content was positively correlated with ?2H: in drier conditions transpired water was more depleted relative to wetter conditions. Our results suggest that the isotopic composition of leaf water within a canopy may vary considerably depending on leaf location and amount of radiation received. These findings have important implications for models of plant water isotopes and underscore the need for additional direct observations of ?T .

  16. Helianthus Nighttime Conductance and Transpiration Respond to Soil Water But Not Nutrient Availability1[W][OA

    PubMed Central

    Howard, Ava R.; Donovan, Lisa A.

    2007-01-01

    We investigated the response of Helianthus species nighttime conductance (gnight) and transpiration (Enight) to soil nutrient and water limitations in nine greenhouse studies. The studies primarily used wild Helianthus annuus, but also included a commercial and early domesticate of H. annuus and three additional wild species (Helianthus petiolaris Nutt., Helianthus deserticola Heiser, and Helianthus anomalus Blake). Well-watered plants of all species showed substantial gnight (0.023–0.225 mol m?2 s?1) and Enight (0.29–2.46 mmol m?2 s?1) measured as instantaneous gas exchange. Based on the potential for transpiration to increase mass flow of mobile nutrients to roots, we hypothesized that gnight and Enight would increase under limiting soil nutrients but found no evidence of responses in all six studies testing this. Based on known daytime responses to water limitation, we hypothesized that gnight and Enight would decrease when soil water availability was limited, and results from all four studies testing this supported our hypothesis. We also established that stomatal conductance at night was on average 5 times greater than cuticular conductance. Additionally, gnight and Enight varied nocturnally and across plant reproductive stages while remaining relatively constant as leaves aged. Our results further the ability to predict conditions under which nighttime water loss will be biologically significant and demonstrate that for Helianthus, gnight can be regulated. PMID:17142487

  17. Relating leaf photosynthetic rate to whole-plant growth: drought and shade effects on seedlings of four Quercus species

    Microsoft Academic Search

    J. L. Quero Perez; R. Villar; T. Marañón; R. Zamora; D. Vega; L. Sack

    2008-01-01

    Understanding the impacts of combined resource supplies on seedlings is critical to enable prediction of establishment growth, and forest dynamics. We investigated the effects of irradiance and water treatments on absolute growth, and relative growth rate (RGR) and its components, for seedlings of four Quercus species differing in leaf habit and with a wide variation in seed mass. Plants were

  18. Thermographic measurements on plant leaves Christoph S. Garbea, Ulrich Schurrb and Bernd Jhnea

    E-print Network

    Garbe, Christoph S.

    is the transpiration of plant leaves. It is actively controlled by pores (stomata) in the leaf and the governing pores (stomata) formed by a complex of cells in the outermost cell layer of leaves. This transport and the surrounding atmosphere. The cells that form the stomata control transpirational water loss by altering

  19. Multi-Rate Feedforward Tracking Control for Plants With Nonminimum Phase Discrete Time Models

    Microsoft Academic Search

    Yuping Gu; Masayoshi Tomizuka

    2001-01-01

    This paper is concerned with performance enhancementof tracking control systems by multi-rate control. Thefeedback controller is updated at the same rate as thesampling rate of the output measurements. The feedforwardcontroller processes the desired output signalfor high accuracy tracking, and its output is updatedat a rate N-times faster than the sampling rate of theoutput measurements. The discrete time model of thecontrolled

  20. Mycorrhizal and non-mycorrhizal Lactuca sativa plants exhibit contrasting responses to exogenous ABA during drought stress and recovery

    PubMed Central

    Aroca, Ricardo; Vernieri, Paolo; Ruiz-Lozano, Juan Manuel

    2008-01-01

    The arbuscular mycorrhizal (AM) symbiosis enhances plant tolerance to water deficit through the alteration of plant physiology and the expression of plant genes. These changes have been postulated to be caused (among others) by different contents of abscisic acid (ABA) between AM and non-AM plants. However, there are no studies dealing with the effects of exogenous ABA on the expression of stress-related genes and on the physiology of AM plants. The aim of the present study was to evaluate the influence of AM symbiosis and exogenous ABA application on plant development, physiology, and expression of several stress-related genes after both drought and a recovery period. Results show that the application of exogenous ABA had contrasting effects on AM and non-AM plants. Only AM plants fed with exogenous ABA maintained shoot biomass production unaltered by drought stress. The addition of exogenous ABA enhanced considerably the ABA content in shoots of non-AM plants, concomitantly with the expression of the stress marker genes Lsp5cs and Lslea and the gene Lsnced. By contrast, the addition of exogenous ABA decreased the content of ABA in shoots of AM plants and did not produce any further enhancement of the expression of these three genes. AM plants always exhibited higher values of root hydraulic conductivity and reduced transpiration rate under drought stress. From plants subjected to drought, only the AM plants recovered their root hydraulic conductivity completely after the 3 d recovery period. As a whole, the results indicate that AM plants regulate their ABA levels better and faster than non-AM plants, allowing a more adequate balance between leaf transpiration and root water movement during drought and recovery. PMID:18469324

  1. Radome cooling by transpiration of a freezing liquid

    NASA Astrophysics Data System (ADS)

    Schindel, L.; Driftmyer, R.

    1989-06-01

    A supersonic wind tunnel test was carried out, in which temperature distributions and the coolant mass flow were measured on a transpiration-cooled conical radome, with the purpose of obtaining data on liquid transpiration cooling that could be scaled from wind tunnel to free-flight conditions. Water coolant was injected through a small porous nose tip, and immediately froze on the surface of the model, even though the adiabatic wall temperature was about 185 deg F. The experimentally determined temperature distributions were modeled using the method of Rubesin and Inouye (1973), providing a means of scaling the experimental data to other flow conditions. The freezing liquid cooling method can be likened to an ablation-cooled radome which employs one or more bands of ablating material. A copper coolant was examined by an application to free flight at Mach number 8; approximate calculations indicate that ablation from the frozen surface of such a liquid metal might be effective in limiting the temperature of a radome.

  2. Shock/shock interference on a transpiration cooled hemispherical model

    NASA Technical Reports Server (NTRS)

    Nowak, Robert J.; Wieting, Allan R.; Holden, Michael S.

    1990-01-01

    Experimental results are presented which show the effectiveness of transpiration cooling in reducing the peak heat flux caused by an impinging shock on a bow shock of a hemispherical model. The 12-inch diameter hemispherical transpiration model with helium coolant was tested in the Calspan 48-inch Hypersonic Shock Tunnel at nominal Mach 12.1 and freestream unit Reynolds number of 0.33 x 10 to the 6th/ft. An incident shock wave, generated by a blunt flat-plate shock generator inclined at 10 deg to the freestream, intersected the bow shock of the model to produce shock/shock interference. The stagnation heat flux without coolant or shock/shock interference was about 1.6 times a smooth surface laminar prediction due to effective roughness of the coolant ejection slots. A coolant mass flux 31 percent of the freestream mass flux reduced the stagnation heat flux to zero without shock/shock interference. However, for the same coolant mass flux and with shock/shock interference the peak heat flux was only reduced 8.3 percent, even though the total integrated heat load was reduced.

  3. Modeling productivity and transpiration of Pinus radiata: climatic effects.

    PubMed

    Sheriff, D. W.; Mattay, J. P.; McMurtrie, R. E.

    1996-01-01

    Climatic effects on annual net carbon gain, stem biomass and annual transpiration were simulated for Pinus radiata D. Don at Canberra and Mt. Gambier. Simulations were conducted with an existing process-based forest growth model (BIOMASS, Model 1) and with a modified version of the BIOMASS model (Model 2) in which response functions for carbon assimilation and leaf conductance were replaced with those derived from field gas exchange data collected at Mt. Gambier. Simulated carbon gain was compared with a published report stating that mean annual stem volume increment (MAI) at Mt. Gambier was 1.8 times greater than at Canberra and that the difference could be the result solely of differences in climate. Regional differences in climate resulted in a 20% greater simulated annual transpiration at Canberra than at Mt. Gambier but only small differences in simulated productivity, indicating that climatic differences did not account for the reported differences in productivity. With Model 1, simulated annual net carbon gain and annual increase in stem biomass were greater at Canberra than at Mt. Gambier, whereas Model 2 indicated a similar annual net carbon gain and annual stem biomass increase in both regions. PMID:14871762

  4. Physiological tradeoffs in the parameterization of a model of canopy transpiration

    Microsoft Academic Search

    D. S. Mackay; D. E. Ahl; B. E. Ewers; S. Samanta; S. T. Gower; S. N. Burrows

    2003-01-01

    We examined physiological parameter tradeoffs in modeling stomatal control of transpiration from a number of forest species. Measurements of sapflux, micrometeorology, and leaf area index were made in stands representing 85% of the forest ecosystems around the WLEF eddy flux tower in northern Wisconsin. A Jarvis-based canopy conductance model was used to simulate canopy transpiration (EC) for five tree species

  5. Modelling surface conductance and transpiration of an oak forest in The Netherlands

    Microsoft Academic Search

    M. J. Ogink-Hendriks

    1995-01-01

    The surface conductance of an oak forest was modelled as a non-linear function of solar radiation, temperature, specific humidity deficit, soil moisture deficit and leaf area index. Hourly values of the surface conductance were derived from the Penman-Monteith equation, using transpiration measurements of a red oak (Quercus rubra) forest in the Netherlands. The transpiration was determined from the energy balance

  6. Exploring the importance of within-canopy spatial temperature variation on transpiration predictions

    Microsoft Academic Search

    William L. Bauerle; Joseph D. Bowden; G. Geoff Wang; Mohamed A. Shahba

    2009-01-01

    Models seldom consider the effect of leaf-level biochemical acclimation to temperature when scaling forest water use. Therefore, the dependence of transpiration on temperature acclimation was investigated at the within-crown scale in climatically contrasting genotypes of Acer rubrum L., cv. October Glory (OG) and Summer Red (SR). The effects of temperature acclimation on intracanopy gradients in transpiration over a range of

  7. Transpiration method: Vapor pressures and enthalpies of vaporization of some low-boiling esters

    Microsoft Academic Search

    Sergey P. Verevkin; Vladimir N. Emel’yanenko

    2008-01-01

    This investigation was undertaken to reveal the upper limit of vapor pressures which could be measured by using the transpiration method accurately. Molar enthalpies of vaporization of 10 esters of monocarboxylic acids were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. The measured data sets were successfully checked for internal consistency. A large number

  8. Effects of Post-fire Succession and Edaphic Conditions on Tree Transpiration in a Boreal Black Spruce Forest

    NASA Astrophysics Data System (ADS)

    Angstmann, J. L.; Ewers, B. E.; Kwon, H.; Bond-Lamberty, B.; Amiro, B.; Gower, S. T.

    2007-12-01

    Boreal forest ecosystems play an integral role in global climate change because of their large land area and ability to store large quantities of carbon. Quantifying and explaining tree water use in both well- and poorly- drained soils and across successional development is critical in understanding the influence of physiological processes on carbon, water, and energy cycling. Four black spruce stands burned in 1850, 1930, 1964, and 1989 were chosen for this research because they had been shown in previous studies to represent critical stages of forest development that capture the successional impacts of both leaf area and species composition change. We hypothesized that tree transpiration will differ between well- and poorly-drained areas and with age due to 1) tree size and age and edaphic-related hydraulic adjustments and 2) tree size will be explained by species specific growth differences from edaphic conditions. Sap flux, leaf water potential (\\PsiL), site specific allometric relationships between sapwood area and leaf area and soil properties such as texture and organic matter depth in each of the four burn ages were utilized to test these hypotheses. Results show that sap flux for Picea mariana at the 1964 burn age differed between well- and poorly-drained soils when scaled per unit xylem area with trees located on poorly-drained soils experiencing higher sap flux rates than trees in well- drained areas (101.79 & 83.02 g cm-2 day-1 respectively). However, when scaled to transpiration on a per tree basis, taking tree size into account, trees on well-drained soils had higher rates than those in poorly- drained locations (366.96 & 216.82 g tree-1 day-1 respectively). The presence of Pinus banksiana and Populus tremuloides in the well-drained areas increased stand transpiration rates for these areas considerably as compared to the poorly-drained areas. Midday \\PsiL for all four burns show no significant difference between well- and poorly-drained (average midday \\PsiL = -1.23 & -1.29 MPa respectively) sites for Picea mariana (t-value = -0.591, df = 6, p-value = 0.576). This indicates that tree size, which is constrained by growth and anaerobic conditions, drives differences in tree transpiration for well- and poorly-drained soils.

  9. Mechanical regulation of plant growth and development

    NASA Technical Reports Server (NTRS)

    Mitchell, C. A.

    1984-01-01

    Soybean and eggplant grown and shaken in a greenhouse exhibited decreased internode length, internode diameter, leaf area, and fresh and dry weight of roots and shoots in much the same way as outdoor-exposed plants. Perhaps more important than decreased dimensions of plant parts resulting from periodic seismic treatment is the inhibition of photosynthetic productivity that accompanies this stress. Soybeam plants briefly shaken or rubbed twice daily experienced a decrease in relative as well as absolute growth rate compared to that of undisturbed controls. Growth dynamics analysis revealed that virtually all of the decline in relative growth rate (RGR) was due to a decline in net assimilation rate (NAR), but not in leaf area ratio (LAR). Lower NAR suggests that the stress-induced decrease in dry weight gain is due to a decline in photosynthetic efficiency. Possible effects on stomatal aperture was investigated by measuring rates of whole plant transpiration as a function of seismo-stress, and a transitory decrease followed by a gradual, partial recovery was detected.

  10. Physiological responses of Vicia faba plants to sulfur dioxide

    SciTech Connect

    Nandi, P.K.; Agrawal, M.; Agrawal, S.B.; Rao, D.N. (Banaras Hindu Univ., Varanasi (India))

    1990-02-01

    Exposure of broad bean (Vicia faba L.) plants to 270 +/- 32 and 670 +/- 45 micrograms m 3SO{sub 2} for 1.5 hr daily between 40 and 85 days of their ages resulted in an increase in their transpiration rate, water saturation deficit, phenol content, and peroxidase activity and a decrease in protein content. With the increase in number of exposures of plants to SO{sub 2}, chlorotic and brown, necrotic visible injury signs were also developed in leaves. It was further noted that the magnitude of undesirable biochemical changes, which possibly helped in the formation of new pigment characteristic of necrotic tissue of SO{sub 2}-exposed plants, was not totally dependent on the pollutant concentration.

  11. Influence of biochar, mycorrhizal inoculation, and fertilizer rate on growth and flowering of Pelargonium (Pelargonium zonale L.) plants

    PubMed Central

    Conversa, Giulia; Bonasia, Anna; Lazzizera, Corrado; Elia, Antonio

    2015-01-01

    Peat is the most common substrate used in nurseries despite being a very expensive and a non-renewable material. Peat replacement with biochar could be a sound environmental practice, as it is produced from waste biomass, but evaluation of biochar as a potting substrate is needed. Ratios of peat:biochar of 100:0, 70:30, 30:70 (BC0, BC30, and BC70, respectively), two fertilizer rates (FERT1, FERT2), and arbuscular mycorrhizal fungi (AMF) inoculation were tested on potted Pelargonium plants. Plant growth, flowering, bio-physiological and nutritional responses, and root mycorrhization were evaluated. The BC30 mixture did not affect plant growth compared with pure peat. However, BC30 in combination with FERT2 treatment was more effective in enhancing nitrogen (N) and chlorophyll (CHL) leaf concentrations, and leaf and flower numbers. The BC70 mixture depressed plant growth, flowering traits, and root mycorrhization. Leaf N concentration was below the sufficiency range reported for Pelargonium growth. Leaf concentration of phosphorous (P) was adequate in pure peat and in BC30 but it dropped close to sub-optimal values in BC70. The pH value of the mixtures lowered P availability, though in BC30 the mycorrhizal activity could have allowed adequate P plant uptake. In BC70 plants, the deficiency of both N and P might be a reason for the observed growth reduction. The inoculation of the substrate with selected AMF improved plant growth (higher dry biomass, greater floral clusters, larger and more abundant leaves) and quality resulting in unstressed (lower electrolyte leakage and higher relative water content values) and greener leaves (low L? and C?, high CHL content) and in more intensely colored flowers. We conclude that biochar can be applied in nursery/potted plant production provided that the proportion in the peat mixture does not exceed 30%. Furthermore, AMF inoculation contributed to achieving the best plant performance in 30% biochar amended medium. PMID:26136757

  12. Influence of biochar, mycorrhizal inoculation, and fertilizer rate on growth and flowering of Pelargonium (Pelargonium zonale L.) plants.

    PubMed

    Conversa, Giulia; Bonasia, Anna; Lazzizera, Corrado; Elia, Antonio

    2015-01-01

    Peat is the most common substrate used in nurseries despite being a very expensive and a non-renewable material. Peat replacement with biochar could be a sound environmental practice, as it is produced from waste biomass, but evaluation of biochar as a potting substrate is needed. Ratios of peat:biochar of 100:0, 70:30, 30:70 (BC0, BC30, and BC70, respectively), two fertilizer rates (FERT1, FERT2), and arbuscular mycorrhizal fungi (AMF) inoculation were tested on potted Pelargonium plants. Plant growth, flowering, bio-physiological and nutritional responses, and root mycorrhization were evaluated. The BC30 mixture did not affect plant growth compared with pure peat. However, BC30 in combination with FERT2 treatment was more effective in enhancing nitrogen (N) and chlorophyll (CHL) leaf concentrations, and leaf and flower numbers. The BC70 mixture depressed plant growth, flowering traits, and root mycorrhization. Leaf N concentration was below the sufficiency range reported for Pelargonium growth. Leaf concentration of phosphorous (P) was adequate in pure peat and in BC30 but it dropped close to sub-optimal values in BC70. The pH value of the mixtures lowered P availability, though in BC30 the mycorrhizal activity could have allowed adequate P plant uptake. In BC70 plants, the deficiency of both N and P might be a reason for the observed growth reduction. The inoculation of the substrate with selected AMF improved plant growth (higher dry biomass, greater floral clusters, larger and more abundant leaves) and quality resulting in unstressed (lower electrolyte leakage and higher relative water content values) and greener leaves (low L(?) and C(?), high CHL content) and in more intensely colored flowers. We conclude that biochar can be applied in nursery/potted plant production provided that the proportion in the peat mixture does not exceed 30%. Furthermore, AMF inoculation contributed to achieving the best plant performance in 30% biochar amended medium. PMID:26136757

  13. Relative rates of nucleotide substitution at the rbc l locus of monocotyledonous plants

    Microsoft Academic Search

    Brandon S. Gaut; Spencer V. Muse; W. Dennis Clark; Michael T. Clegg

    1992-01-01

    We subjected 35 rbcL nucleotide sequences from monocotyledonous taxa to maximum likelihood relative rate tests and estimated relative differences in rates of nucleotide substitution between groups of sequences without relying on knowledge of divergence times between taxa. Rate tests revealed that there is a hierarchy of substitution rate at the rbcL locus within the monocots. Among the taxa analyzed the

  14. Partitioning of Evaporation and Transpiration in Semiarid Ecosystems Using a Dual-source Surface Energy Model (TVET)

    Microsoft Academic Search

    H. Guan; J. L. Wilson; E. E. Small

    2006-01-01

    Vegetation transpiration is strongly connected to photosynthesis, and thus the ability of vegetation to store carbon and utilize soil nutrients. Transpiration draws water from throughout the root zone, but the vertical spatial distribution of evaporation is much shallower. Because of these and other unique processes it has become important to understand the partitioning of evaporation (E) and transpiration (T) in

  15. Plants

    NSDL National Science Digital Library

    Anne Barron

    2011-04-14

    What is the cycle plants go through? First use Write out the Plant Cycle Watch the Plant Powerpoint write down what you learned. Next watch the movie Plant Cycle Movie What did you think was interesting? Next, search around on the website and write down facts about plants. LIfe Cycle of Plants Next, play around with the part of the plants http://www.sciencekids.co.nz/gamesactivities/lifecycles.htmlFinally learn all about growing a plant. Growing a plant After you are finished come see me ...

  16. Comparisons among species composition, leaf area, and water relations in three shrub-steppe plant communities

    SciTech Connect

    Link, S.O.; Kirkham, R.R.; Thiede, M.E.; Downs, J.L.; Gee, G.W.

    1987-03-01

    Observations were made on plant communities dominated by Bromus tectorum (cheatgrass site), Artemisia tridentata (sagebrush site), and Grayia spinosa (hopsage site). Leaf area on a ground area basis of sagebrush was nor significantly different between the sagebrush and hopsage sites; however, the leaf area of hopsage was one-quarter that of sagebrush at the hopsage site. Pre-dawn xylem water potential of sagebrush was -2.91 MPa, while that of hopsage was -4.79 MPa. Stomatal conductance and transpiration rate of sagebrush and hopsage were nearly the same. 11 refs., 4 figs., 2 tabs.

  17. Thermal simulation and economic assessment of unglazed transpired collector systems

    SciTech Connect

    Summers, D.N.; Mitchell, J.W.; Klein, S.A.; Beckman, W.A.

    1996-10-01

    Unglazed transpired collectors (UTCs) have recently emerged as a new solar air heating technology. They are relatively inexpensive, efficient, and particularly suited to applications in which a high outdoor air requirement must be met. A TRNSYS model has been created for UTC systems. Annual simulations are performed for several representative buildings. The statewide economic potential of UTC systems is assessed for Wisconsin. UTC systems on existing buildings are competitive with electric heating systems but not with gas or oil heating. Electric heating is not widely used in most buildings that are well-suited for UTC systems, with the exception of large apartment buildings. Therefore, there is no significant statewide economic potential for retrofit of UTC systems on existing buildings except in the residential sector. However, UTC systems are cost effective for new buildings because their low first cost allows them to compete with gas and oil heating.

  18. The effect of rates of sedimentation and tidal submersion regimes on the growth of salt marsh plants

    NASA Astrophysics Data System (ADS)

    Boorman, Laurence A.; Hazelden, J.; Boorman, M.

    2001-12-01

    A system of tidal mesocosms has been constructed in order to determine interactions between rates of accretion and duration of inundation. Plants are grown in three tanks in which different tidal regimes are simulated by a system of electronically controlled pumps. Sediment is added to give four different rates of accretion and the mesocosms are run under controlled greenhouse conditions. To date experiments have been conducted with seedlings of Salicornia europaea and Aster tripolium. The longest duration of immersion reduces the growth rate of root and shoot of Salicornia seedlings but Aster was unaffected by 5 h submersion daily. Both species, however, responded positively to all rates of sediment addition up to the equivalent of 60 mm per year. The implication of these findings are discussed in relation to salt marsh development.

  19. A prototype photovoltaic/thermal system integrated with transpired collector

    SciTech Connect

    Athienitis, Andreas K.; Bambara, James; O'Neill, Brendan; Faille, Jonathan [Dept. of Building, Civil and Environmental Engineering, Concordia University, 1455 Maisonneuve W., Montreal, Quebec (Canada)

    2011-01-15

    Building-integrated photovoltaic/thermal (BIPV/T) systems may be utilized to produce useful heat while simultaneously generating electricity from the same building envelope surface. A well known highly efficient collector is the open-loop unglazed transpired collector (UTC) which consists of dark porous cladding through which outdoor air is drawn and heated by absorbed solar radiation. Commercially available photovoltaic systems typically produce electricity with efficiencies up to about 18%. Thus, it is beneficial to obtain much of the normally wasted heat from the systems, possibly by combining UTC with photovoltaics. Combination of BIPV/T and UTC systems for building facades is considered in this paper - specifically, the design of a prototype facade-integrated photovoltaic/thermal system with transpired collector (BIPV/T). A full scale prototype is constructed with 70% of UTC area covered with PV modules specially designed to enhance heat recovery and compared to a UTC of the same area under outdoor sunny conditions with low wind. The orientation of the corrugations in the UTC is horizontal and the black-framed modules are attached so as to facilitate flow into the UTC plenum. While the overall combined thermal efficiency of the UTC is higher than that of the BIPV/T system, the value of the generated energy - assuming that electricity is at least four times more valuable than heat - is between 7% and 17% higher. Also, the electricity is always useful while the heat is usually utilized only in the heating season. The BIPV/T concept is applied to a full scale office building demonstration project in Montreal, Canada. The ratio of photovoltaic area coverage of the UTC may be selected based on the fresh air heating needs of the building, the value of the electricity generated and the available building surfaces. (author)

  20. Association of Biodiversity with the Rates of Micropollutant Biotransformations among Full-Scale Wastewater Treatment Plant Communities

    PubMed Central

    Helbling, Damian E.; Lee, Tae Kwon; Park, Joonhong; Fenner, Kathrin; Kohler, Hans-Peter E.; Ackermann, Martin

    2014-01-01

    Biodiversities can differ substantially among different wastewater treatment plant (WWTP) communities. Whether differences in biodiversity translate into differences in the provision of particular ecosystem services, however, is under active debate. Theoretical considerations predict that WWTP communities with more biodiversity are more likely to contain strains that have positive effects on the rates of particular ecosystem functions, thus resulting in positive associations between those two variables. However, if WWTP communities were sufficiently biodiverse to nearly saturate the set of possible positive effects, then positive associations would not occur between biodiversity and the rates of particular ecosystem functions. To test these expectations, we measured the taxonomic biodiversity, functional biodiversity, and rates of 10 different micropollutant biotransformations for 10 full-scale WWTP communities. We have demonstrated that biodiversity is positively associated with the rates of specific, but not all, micropollutant biotransformations. Thus, one cannot assume whether or how biodiversity will associate with the rate of any particular micropollutant biotransformation. We have further demonstrated that the strongest positive association is between biodiversity and the collective rate of multiple micropollutant biotransformations. Thus, more biodiversity is likely required to maximize the collective rates of multiple micropollutant biotransformations than is required to maximize the rate of any individual micropollutant biotransformation. We finally provide evidence that the positive associations are stronger for rare micropollutant biotransformations than for common micropollutant biotransformations. Together, our results are consistent with the hypothesis that differences in biodiversity can indeed translate into differences in the provision of particular ecosystem services by full-scale WWTP communities. PMID:25398862

  1. ZPMHD-a Rep-rated Z-Pinch Power Plant Direct Conversion Concept

    Microsoft Academic Search

    John S. de Groot; El Houssein Alki

    2001-01-01

    We have performed a preliminary conceptual study of ZPMHD, a z-pinch driven IFE power plant with Compact Fusion Advanced Rankine (CFARII) MHD direct conversion [B. G. Logan, Fusion Eng. and Des. 22, 151 (1993)]. We find that a competitive power plant could be built that has a Cost of Electricity (CoE) Å 40 mills\\/kWh for a compact blanket of Lithium

  2. Growth rates of rhizosphere microorganisms depend on competitive abilities of plants for nitrogen

    Microsoft Academic Search

    Evgenia Blagodatskaya; Johanna Littschwager; Marianna Lauerer; Yakov Kuzyakov

    2010-01-01

    Rhizosphere - one of the most important `hot spots' in soil - is characterized not only by accelerated turnover of microbial biomass and nutrients but also by strong intra- and inter-specific competition. Intra-specific competition occurs between individual plants of the same species, while inter-specific competition can occur both at population level (plant species-specific, microbial species-specific interactions) and at community level

  3. Wheat cultivars selected for high Fv /Fm under heat stress maintain high photosynthesis, total chlorophyll, stomatal conductance, transpiration and dry matter.

    PubMed

    Sharma, Dew Kumari; Andersen, Sven Bode; Ottosen, Carl-Otto; Rosenqvist, Eva

    2015-02-01

    The chlorophyll fluorescence parameter Fv /Fm reflects the maximum quantum efficiency of photosystem II (PSII) photochemistry and has been widely used for early stress detection in plants. Previously, we have used a three-tiered approach of phenotyping by Fv /Fm to identify naturally existing genetic variation for tolerance to severe heat stress (3 days at 40°C in controlled conditions) in wheat (Triticum aestivum L.). Here we investigated the performance of the previously selected cultivars (high and low group based on Fv /Fm value) in terms of growth and photosynthetic traits under moderate heat stress (1 week at 36/30°C day/night temperature in greenhouse) closer to natural heat waves in North-Western Europe. Dry matter accumulation after 7 days of heat stress was positively correlated to Fv /Fm . The high Fv /Fm group maintained significantly higher total chlorophyll and net photosynthetic rate (PN ) than the low group, accompanied by higher stomatal conductance (gs ), transpiration rate (E) and evaporative cooling of the leaf (?T). The difference in PN between the groups was not caused by differences in PSII capacity or gs as the variation in Fv /Fm and intracellular CO2 (Ci ) was non-significant under the given heat stress. This study validated that our three-tiered approach of phenotyping by Fv /Fm performed under increasing severity of heat was successful in identifying wheat cultivars differing in photosynthesis under moderate and agronomically more relevant heat stress. The identified cultivars may serve as a valuable resource for further studies to understand the physiological mechanisms underlying the genetic variability in heat sensitivity of photosynthesis. PMID:24962705

  4. Exploring the importance of within-canopy spatial temperature variation on transpiration predictions

    PubMed Central

    Bauerle, William L.; Bowden, Joseph D.; Wang, G. Geoff; Shahba, Mohamed A.

    2009-01-01

    Models seldom consider the effect of leaf-level biochemical acclimation to temperature when scaling forest water use. Therefore, the dependence of transpiration on temperature acclimation was investigated at the within-crown scale in climatically contrasting genotypes of Acer rubrum L., cv. October Glory (OG) and Summer Red (SR). The effects of temperature acclimation on intracanopy gradients in transpiration over a range of realistic forest growth temperatures were also assessed by simulation. Physiological parameters were applied, with or without adjustment for temperature acclimation, to account for transpiration responses to growth temperature. Both types of parameterization were scaled up to stand transpiration (expressed per unit leaf area) with an individual tree model (MAESTRA) to assess how transpiration might be affected by spatial and temporal distributions of foliage properties. The MAESTRA model performed well, but its reproducibility was dependent on physiological parameters acclimated to daytime temperature. Concordance correlation coefficients between measured and predicted transpiration were higher (0.95 and 0.98 versus 0.87 and 0.96) when model parameters reflected acclimated growth temperature. In response to temperature increases, the southern genotype (SR) transpiration responded more than the northern (OG). Conditions of elevated long-term temperature acclimation further separate their transpiration differences. Results demonstrate the importance of accounting for leaf-level physiological adjustments that are sensitive to microclimate changes and the use of provenance-, ecotype-, and/or genotype-specific parameter sets, two components likely to improve the accuracy of site-level and ecosystem-level estimates of transpiration flux. PMID:19561047

  5. Effects of nitrogen form on growth, CO? assimilation, chlorophyll fluorescence, and photosynthetic electron allocation in cucumber and rice plants.

    PubMed

    Zhou, Yan-hong; Zhang, Yi-li; Wang, Xue-min; Cui, Jin-xia; Xia, Xiao-jian; Shi, Kai; Yu, Jing-quan

    2011-02-01

    Cucumber and rice plants with varying ammonium (NH(4)(+)) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO(3)(-))-grown plants, cucumber plants grown under NH(4)(+)-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO(2)) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O(2)-independent alternative electron flux, and increased O(2)-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH(4)(+)-grown plants had a higher O(2)-independent alternative electron flux than NO(3)(-)-grown plants. NO(3)(-) reduction activity was rarely detected in leaves of NH(4)(+)-grown cucumber plants, but was high in NH(4)(+)-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO(3)(-) assimilation, an effect more significant in NO(3)(-)-grown plants than in NH(4)(+)-grown plants. Meanwhile, NH(4)(+)-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO(3)(-) reduction, regardless of the N form supplied, while NH(4)(+)-sensitive plants had a high water-water cycle activity when NH(4)(+) was supplied as the sole N source. PMID:21265044

  6. Substitution rates in the X- and Y-linked genes of the plants, Silene latifolia and S. dioica.

    PubMed

    Filatov, Dmitry A; Charlesworth, Deborah

    2002-06-01

    Theory predicts that selection should be less effective in the nonrecombining genes of Y-chromosomes, relative to the situation for genes on the other chromosomes, and this should lead to the accumulation of deleterious nonsynonymous substitutions. In addition, synonymous substitution rates may differ between X- and Y-linked genes because of the male-driven evolution effect and also because of actual differences in per-replication mutation rates between the sex chromosomes. Here, we report the first study of synonymous and nonsynonymous substitution rates on plant sex chromosomes. We sequenced two pairs of sex-linked genes, SlX1-SlY1 and SlX4-SlY4, from dioecious Silene latifolia and S. dioica, and their non-sex-linked homologues from nondioecious S. vulgaris and Lychnis flos-jovis, respectively. The rate of nonsynonymous substitutions in the SlY4 gene is significantly higher than that in the SlX4 gene. Silent substitution rates are also significantly higher in both Y-linked genes, compared with their X-linked homologues. The higher nonsynonymous substitution rate in the SlY4 gene is therefore likely to be caused by a mutation rate difference between the sex chromosomes. The difference in silent substitution rates between the SlX4 and SlY4 genes is too great to be explained solely by a higher per-generation mutation rate in males than females. It is thus probably caused by a difference in per-replication mutation rates between the sex chromosomes. This suggests that the local mutation rate can change in a relatively short evolutionary time. PMID:12032246

  7. Differential Atmospheric Controls on Transpiration of Boreal Trees: A Potential Factor in Pre-mature Tree Mortality in Green-Tree Retention Strategies

    NASA Astrophysics Data System (ADS)

    Bladon, K. D.; Silins, U.; Lieffers, V. J.

    2004-05-01

    Green-tree retention, a harvesting strategy that involves the preservation of isolated and interconnected patches of live trees within the boundaries of harvested areas, is assumed to emulate natural disturbance, while preserving forest canopy continuity for wildlife habitat, maintaining forest biodiversity, and many other landscape level objectives. Unfortunately, many of the retention trees die within a few years after harvesting, thus much of the desired function of these trees is lost. This research focuses on understanding the relationship between changes in micro-climate following harvesting and transpiration, potentially leading to drought-induced mortality of aspen, balsam poplar, white spruce, and white birch. Continuous measurements of whole-tree water use (sap flow) and micro-climate were taken before and after harvesting of two adjacent boreal mixedwood stands in west-central Alberta in the summer of 2003. Differences in micro-climate including radiation, air temperature, relative humidity and wind penetration into the canopy produced large differences in atmospheric moisture demand (PET) between partially harvested (green-tree retention) and undisturbed forest canopies. The variability in atmospheric conditions created large differences in sap flow velocity and transpiration rates among these four boreal species. Differential transpiration rates among species will be discussed in context of atmospheric controls on water use and drought tolerance of boreal trees with differing autecology and/or hydraulic architecture.

  8. Quantification of excess water loss in plant canopies warmed with infrared heating.

    PubMed

    De Boeck, Hans J; Kimball, Bruce A; Miglietta, Franco; Nijs, Ivan

    2012-09-01

    Here we investigate the extent to which infrared heating used to warm plant canopies in climate manipulation experiments increases transpiration. Concerns regarding the impact of the infrared heater technique on the water balance have been raised before, but a quantification is lacking. We calculate transpiration rates under infrared heaters and compare these with air warming at constant relative humidity. As infrared heating primarily warms the leaves and not the air, this method increases both the gradient and the conductance for water vapour. Stomatal conductance is determined both independently of vapour pressure differences and as a function thereof, while boundary layer conductance is calculated using several approaches. We argue that none of these approaches is fully accurate, and opt to present results as an interval in which the actual water loss is likely to be found. For typical conditions in a temperate climate, our results suggest a 12-15% increase in transpiration under infrared heaters for a 1 °C warming. This effect decreases when stomatal conductance is allowed to vary with the vapour pressure difference. Importantly, the artefact is less of a concern when simulating heat waves. The higher atmospheric water demand underneath the heaters reflects naturally occurring increases of potential evapotranspiration during heat waves resulting from atmospheric feedback. While air warming encompasses no increases in transpiration, this fully depends on the ability to keep humidity constant, which in the case of greenhouses requires the presence of an air humidification system. As various artefacts have been associated with chamber experiments, we argue that manipulating climate in the field should be prioritized, while striving to limit confounding factors. The excess water loss underneath infrared heaters reported upon here could be compensated by increasing irrigation or applying newly developed techniques for increasing air humidity in the field. PMID:24501063

  9. Multivariate genetic analysis of plant responses to water deficit and high temperature revealed contrasting adaptive strategies

    PubMed Central

    Vasseur, François; Bontpart, Thibaut; Dauzat, Myriam; Granier, Christine; Vile, Denis

    2014-01-01

    How genetic factors control plant performance under stressful environmental conditions is a central question in ecology and for crop breeding. A multivariate framework was developed to examine the genetic architecture of performance-related traits in response to interacting environmental stresses. Ecophysiological and life history traits were quantified in the Arabidopsis thaliana Ler×Cvi mapping population exposed to constant soil water deficit and high air temperature. The plasticity of the genetic variance–covariance matrix (G-matrix) was examined using mixed-effects models after regression into principal components. Quantitative trait locus (QTL) analysis was performed on the predictors of genotype effects and genotype by environment interactions (G×E). Three QTLs previously identified for flowering time had antagonistic G×E effects on carbon acquisition and the other traits (phenology, growth, leaf morphology, and transpiration). This resulted in a size-dependent response of water use efficiency (WUE) to high temperature but not soil water deficit, indicating that most of the plasticity of carbon acquisition and WUE to temperature is controlled by the loci that control variation of development, size, growth, and transpiration. A fourth QTL, MSAT2.22, controlled the response of carbon acquisition to specific combinations of watering and temperature irrespective of plant size and development, growth, and transpiration rate, which resulted in size-independent plasticity of WUE. These findings highlight how the strategies to optimize plant performance may differ in response to water deficit and high temperature (or their combination), and how different G×E effects could be targeted to improve plant tolerance to these stresses. PMID:25246443

  10. Dry season foliar fog uptake, reverse sapflow, and nighttime transpiration in the tropical montane cloud forests of Mexico

    NASA Astrophysics Data System (ADS)

    Gotsch, S. G.; Asbjornsen, H.; Holwerda, F.; Goldsmith, G. R.; Dawson, T. E.

    2010-12-01

    Dry season fog is a ubiquitous feature of seasonal tropical cloud forests. Although cloud forests receive generous inputs of yearly precipitation, rainfall occurs primarily in the wet season. In the tropical montane forests of Veracruz Mexico, 80% of rainfall occurs in the wet season while fog occurs primarily in the dry season. Since dry-season fog occurs during months when precipitation is low or absent, this meteorological phenomenon may be important in alleviating dry-season water stress either directly through foliar fog uptake, or indirectly through a reduction in transpiration causing relaxation in xylem water tension. We determined the importance of fog on the water relations of a dominant tropical montane forest tree in La Cortadura Reserve in Veracruz, Mexico by using micrometeorological data and by measuring sap flow, leaf water potential and stomatal conductance throughout the canopies of three mature oak trees. Although the relative humidity is generally high in this habitat, in the dry season, humidity is lower and at times can be as low as 20% which causes high vapor pressure deficit and evaporative demand. We also screened sap flow data to detect periods of nighttime transpiration. Reverse sap flow occurred frequently in this site during periods of fog/drizzle. Foliar fog uptake occurred 30% of the time in the dry season although this reverse flow is likely insignificant in the water balance of cloud forest trees. Furthermore we detected low, but positive, flow rates flow at night. Finally, we conducted diurnal courses of leaf water potential and stomatal conductance at the end of the dry season to determine whether these trees were undergoing water stress. Results/Conclusions We found that reverse sap flow is a common phenomena in the dry season, indicating foliar fog uptake. Although the addition of fog to whole-tree water balance may be minimal, high dry season leaf water potential may indicate the importance of fog in reducing the negative physiological impact of dry periods. Nighttime transpiration is also a common phenomena in these forests and accounts for approximately 30% of total water transpired in the dry season. Climate change scenarios often predict a reduction of fog in montane habitats; our results indicate that this may have important repercussions on the physiology of montane forest trees and persistence of montane cloud forest vegetation in this region.

  11. Parameter estimation of a plant uptake model for cyanide: application to hydroponic data.

    PubMed

    Bushey, Joseph T; Small, Mitchell J; Dzombak, David A; Ebbs, Stephen D

    2006-01-01

    A plant uptake model is applied to describe free cyanide and ferrocyanide transport and fate in willow (Salix eriocephala var. Michaux) grown in hydroponics. The model is applied to experimental data to determine best-fit parameter values, their associated uncertainty, and their relative importance to field-scale phytoremediation applications. The fitted model results, using least-squares optimization of the observed log concentrations, indicate that free cyanide volatilization from leaf tissue and free cyanide cell wall adsorption were negligible. The free cyanide maximum uptake rate and assimilate (noncyanide 15N) first-order leaf loss rate were the only coefficients that significantly affected the model goodness of fit and were concurrently sensitive to data uncertainty in the parameter optimization. Saturation kinetics may be applicable for free cyanide uptake into plants, but not for ferrocyanide uptake, which may occur via preferential protein-mediated or inefficient transpiration stream uptake. Within the free cyanide system, the relative magnitudes of the saturation uptake parameters and the demonstration of an active role for plants in uptake relative to transpiration suggest the potential importance of preferential diffusion through the cell membranes as reported in the literature, rather than protein-mediated uptake. The fitted 13-parameter model matched the observed data well except for the predicted stem and leaf tissue assimilate concentrations, which were significantly underestimated, particularly in the free cyanide system. These low predicted values, combined with the slightly underestimated solution free cyanide removal, suggest that noncyanide 15N redistribution in phloem should be considered. PMID:16615307

  12. Responses of Leaf-level Carbon Assimilation and Transpiration to Root-zone Water Potential Changes in a Subtropical Tree Species

    NASA Astrophysics Data System (ADS)

    Cicheng, Z.; Guan, H.; Han, G.; Zhang, X.

    2013-12-01

    Photosynthetic carbon assimilation in terrestrial ecosystems significantly contributes to global carbon balance in the atmosphere. While vegetation photosynthesizes to fix CO2, it simultaneously transpires H2O. These two interdependent processes are regulated by leaf stomata which are sensitive to environmental conditions (such as root zone soil moisture). Knowledge of the responses of leaf-level transpiration and carbon assimilation to a change of root-zone soil moisture condition is important to understand how these processes influence water balance and carbon sequestration in terrestrial ecosystems, and to understand the capacity of trees to cope with future climate changes.We will present the results of a one-year observational study on a subtropical evergreen broadleaf tree species (Osmanthus fragrans) in the central south China. The observations were carried out on two 8-year Osmanthus fragrans trees in a plantation site from 1 Sep, 2012 to 31 Aug, 2013. A portable infrared gas exchange analyzer (Li-6400, Li-COR, Inc., Lincoln, Nebraska, USA) was used to measure leaf photosynthesis and leaf transpiration on clear days. Root zone soil water potential was estimated from predawn stem water potential using stem psychrometers (ICT, Australia). Sap flow and micrometeorological data were also collected. The results show that the average leaf carbon assimilation rate at light saturation decreases quickly with the root zone water potential from 0 to -1 MPa, and slowly after the root zone water potential falls below -1 MPa. The average leaf transpiration at light saturation shows a similar pattern. Leaf-level water use efficiency increases slowly with a decrease of root-zone water potential from 0 to -1 MPa, and keeps constant when the root zone gets drier. This relationship provides a potential to estimate whole-tree carbon assimilation from sap flow measurements. Leaf assimilation rates at light saturation in early morning vs. root-zone water potential for Osmanthus fragrans.

  13. Evaluating the Performance and Economics of Transpired Solar Collectors for Commercial Applications: Preprint

    SciTech Connect

    Kozubal, E.; Deru, M.; Slayzak, S.; Norton, P.; Barker, G.; McClendon, J,

    2008-07-01

    Using transpired solar collectors to preheat ventilation air has recently become recognized as an economic alternative for integrating renewable energy into commercial buildings in heating climates. The collectors have relatively low installed costs and operate on simple principles. Theory and performance testing have shown that solar collection efficiency can exceed 70% of incident solar. However, implementation and current absorber designs have adversely affected the efficiency and associated economics from this initial analysis. The National Renewable Energy Laboratory has actively studied this technology and monitored performance at several installations. A calibrated model that uses typical meteorological weather data to determine absorber plate efficiency resulted from this work. With this model, an economic analysis across heating climates was done to show the effects of collector size, tilt, azimuth, and absorptivity. The analysis relates the internal rate of return of a system based on the cost of the installed absorber area. In general, colder and higher latitude climates return a higher rate of return because the heating season extends into months with good solar resource.

  14. Hydraulic lift through transpiration suppression in shrubs from two arid ecosystems: patterns and control mechanisms.

    PubMed

    Prieto, Iván; Martínez-Tillería, Karina; Martínez-Manchego, Luis; Montecinos, Sonia; Pugnaire, Francisco I; Squeo, Francisco A

    2010-08-01

    Hydraulic lift (HL) is the passive movement of water through the roots from deep wet to dry shallow soil layers when stomata are closed. HL has been shown in different ecosystems and species, and it depends on plant physiology and soil properties. In this study we explored HL patterns in several arid land shrubs, and developed a simple model to simulate the temporal evolution and magnitude of HL during a soil drying cycle under relatively stable climatic conditions. This model was then used to evaluate the influence of soil texture on the quantity of water lifted by shrubs in different soil types. We conducted transpiration suppression experiments during spring 2005 in Chile and spring 2008 in Spain on five shrub species that performed HL, Flourensia thurifera, Senna cumingii and Pleocarphus revolutus (Chile), Retama sphaerocarpa and Artemisia barrelieri (Spain). Shrubs were covered with a black, opaque plastic fabric for a period of 48-72 h, and soil water potential was recorded at different depths under the shrubs. While the shrubs remained covered, water potential continuously increased in shallow soil layers until the cover was removed. The model output indicated that the amount of water lifted by shrubs is heavily dependent on soil texture, as shrubs growing in loamy soils redistributed up to 3.6 times more water than shrubs growing on sandy soils. This could be an important consideration for species growing in soils with different textures, as their ability to perform HL would be context dependent. PMID:20364271

  15. Long-term starvation and subsequent reactivation of a high-rate partial nitrification activated sludge pilot plant.

    PubMed

    Torà, Josep A; Lafuente, Javier; Baeza, Juan A; Carrera, Julián

    2011-11-01

    The starvation process of a high-rate partial nitrification system during 30 days and its controlled recovery were studied in an activated sludge pilot plant. Four ammonium-starved reactors under anoxic, aerobic and two different alternating aerobic/anoxic conditions were evaluated. The highest and the lowest decay rates of ammonia oxidizing bacteria (AOB) were obtained under full aerobic (0.24 d(-1)) and full anoxic (0.11 d(-1)) conditions, respectively. The evolution of biomass activity correlated well with the AOB quantification using FISH technique. AOB fractions lower than 1% were measured in the four reactors after 23 days of starvation. The recovery of the system was achieved in only 5 days using a nitrogen loading rate (NLR) control loop, obtaining the same conditions than before the long-term starvation period with a NLR of 1.2 g N L(-1)d(-1) and 98% of nitrite accumulation in the effluent. PMID:21890345

  16. Seasonal photosynthetic gas exchange and water-use efficiency in a constitutive CAM plant, the giant saguaro cactus (Carnegiea gigantea).

    PubMed

    Bronson, Dustin R; English, Nathan B; Dettman, David L; Williams, David G

    2011-11-01

    Crassulacean acid metabolism (CAM) and the capacity to store large quantities of water are thought to confer high water use efficiency (WUE) and survival of succulent plants in warm desert environments. Yet the highly variable precipitation, temperature and humidity conditions in these environments likely have unique impacts on underlying processes regulating photosynthetic gas exchange and WUE, limiting our ability to predict growth and survival responses of desert CAM plants to climate change. We monitored net CO(2) assimilation (A(net)), stomatal conductance (g(s)), and transpiration (E) rates periodically over 2 years in a natural population of the giant columnar cactus Carnegiea gigantea (saguaro) near Tucson, Arizona USA to investigate environmental and physiological controls over carbon gain and water loss in this ecologically important plant. We hypothesized that seasonal changes in daily integrated water use efficiency (WUE(day)) in this constitutive CAM species would be driven largely by stomatal regulation of nighttime transpiration and CO(2) uptake responding to shifts in nighttime air temperature and humidity. The lowest WUE(day) occurred during time periods with extreme high and low air vapor pressure deficit (D(a)). The diurnal with the highest D(a) had low WUE(day) due to minimal net carbon gain across the 24 h period. Low WUE(day) was also observed under conditions of low D(a); however, it was due to significant transpiration losses. Gas exchange measurements on potted saguaro plants exposed to experimental changes in D(a) confirmed the relationship between D(a) and g(s). Our results suggest that climatic changes involving shifts in air temperature and humidity will have large impacts on the water and carbon economy of the giant saguaro and potentially other succulent CAM plants of warm desert environments. PMID:21822726

  17. Transpirational water use and its regulation in the mountainous terrain of S. Korea

    NASA Astrophysics Data System (ADS)

    Otieno Dennis, O.; Eunyoung, J.; Sinkyu, K.; Tenhunen, J. D.

    2009-12-01

    Quantifying water use by forests growing on complex mountainous terrain is difficult and understanding of controls on water use by these forests a challenge. Yet mountains are crucial as water towers and better understanding of their hydrology and ecology is critical for sustainable management. Consequently, there is a growing need for new research approaches designed with attention to the particular needs and constraints of large-scale studies and that have the potential to generate reliable and accurate data. The use of a combination of different sapflow-measurement techniques provides a unique opportunity to monitor water use by the understory and canopy forest tree species at micro-scale, allowing for accurate estimation of total forest water use. The obtained data, in conjunction with intensively measured climatic variables, allow for better understanding and interpretation of transpiration results. A research initiative under the International Training Group: Complex Terrain and Ecological Heterogeneity (TERRECO) seeks to address pertinent issues related to forest water use and production in complex terrain. Stem Heat balance (SHB) and Heat Dissipation techniques have been employed to measure sapflow in the understory woody plants and tree branches and on stems of canopy trees respectively. Measurements have been stratified to account for differences in tree sizes and species diversity. To better understand the data, we are intensively monitoring soil moisture at 5, 10 and 30 cm depths, in addition to a range of micrometeorology sensors that have been set up below, within and above the canopy. These measurements have been planned, taking into account altitudinal/elevation gradient, aspect and within site differences in species composition and tree sizes and to generate data for large-scale modeling of the entire catchment. A total of 70 trees from 9 species growing in six different locations at varying elevations and aspects are being monitored. Peak daily water use by trees during mid summer amounts to 45 kg d-1 but varies significantly with sapwood area. Within a species, there is a consistent relationship between tree size (DBH) and sapwood area irrespective of elevation. We have also established a common trend in the relationship between wood density and sap flux density (Js) that transcends the boundaries of species differences. These initial findings are critical for our planned upscaling of water use by the forest catchment. In addition to soil moisture, vapor pressure deficit (VPD) and light play a crucial regulatory role on forest water use. We are at the stage of establishing a common link that brings together micrometeorology and transpiration that will allow for large scale modeling of forest water use.

  18. Rice (Oryza sativa L.) response to clomazone as influenced by rate, soil type, and planting date

    E-print Network

    O'Barr, John Houston

    2006-08-16

    Literature Review?????????????... 2 II SOIL CHARACTERISTICS AND WATER POTENTIAL EFFECTS ON PLANT AVAILABLE CLOMAZONE IN RICE????????????????????????... 8... ix LIST OF FIGURES FIGURE Page 1 Relationship between mass water content (Thetam) and water potential (kPa) of four soils?????????????????????. 13 2 Centrifugation double-tube apparatus?????????????.. 16 3 Bleaching...

  19. The evolution of inquilinism, host-plant use and mitochondrial substitution rates in Tamalia gall aphids

    Microsoft Academic Search

    D. G. Miller; B. Crespi

    2003-01-01

    We used mitochondrial DNA data to infer phylogenies for 28 samples of gall- inducing Tamalia aphids from 12 host-plant species, and for 17 samples of Tamalia inquilinus, aphid 'inquilines' that obligately inhabit galls of the gall inducers and do not form their own galls. Our phylogenetic analyses indicate that the inquilines are monophyletic and closely related to their host aphids.

  20. Estimating the relative rates of pollen and seed migration among plant populations

    Microsoft Academic Search

    R A Ennos

    1994-01-01

    Interpopulation gene flow in plants is mediated by a combination of pollen and seed dispersal. The effectiveness of pollen and seeds in bringing about gene flow depends upon the mode of inheritance of the genetic marker. For nuclear and paternally inherited markers, gene flow occurs in both pollen and seed. For maternally inherited markers, genes are only dispersed in seeds.