Sample records for stem leaf number

  1. Ginseng leaf-stem: bioactive constituents and pharmacological functions

    Microsoft Academic Search

    Hongwei Wang; Dacheng Peng; Jingtian Xie

    2009-01-01

    Ginseng root is used more often than other parts such as leaf stem although extracts from ginseng leaf-stem also contain similar active ingredients with pharmacological functions. Ginseng's leaf-stems are more readily available at a lower cost than its root. This article reviews the pharmacological effects of ginseng leaf-stem on some diseases and adverse effects due to excessive consumption. Ginseng leaf-stem

  2. 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

  3. 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

  4. Characterizing natural cellulose fibers from velvet leaf ( Abutilon theophrasti) stems

    Microsoft Academic Search

    Narendra Reddy; Yiqi Yang

    2008-01-01

    Velvet leaf (Abutilon theophrasti) that is currently considered a weed and an agricultural problem could be used as a source for high quality natural cellulose fibers. The fibers obtained from the velvet leaf stems are mainly composed of approximately 69% cellulose and 17% lignin. The single cells in the fiber have lengths of approximately 0.9mm, shorter than those in common

  5. Inhibitory effect of parthenium ( Parthenium hysterophorus L.) residue on growth of water hyacinth ( Eichhornia crassipes Mart Solms.) II. Relative effect of flower, leaf, stem, and root residue

    Microsoft Academic Search

    D. K. Pandey; L. P. Kauraw; V. M. Bhan

    1993-01-01

    The relative effect of residue of leaf, flower, stem, and root of parthenium (Parthenium hysterophorus L.) on growth of water hyacinth was studied. The inhibitory activity of the residue as shown by its effect on biomass and healthy leaf number (HLN) of treated plants was in the order: leaf and flower >stem >root. Total phenolic acids in the medium after

  6. Structure and enzymatic accessibility of leaf and stem from wheat straw before and after hydrothermal pretreatment

    PubMed Central

    2014-01-01

    Background Biomass recalcitrance is affected by a number of chemical, physical and biological factors. In this study we looked into the differences in recalcitrance between two major anatomical fractions of wheat straw biomass, leaf and stem. A set of twenty-one wheat cultivars was fractionated and illustrated the substantial variation in leaf-to-stem ratio between cultivars. The two fractions were compared in terms of chemical composition, enzymatic convertibility, cellulose crystallinity and glucan accessibility. The use of water as a probe for assessing glucan accessibility was explored using low field nuclear magnetic resonance and infrared spectroscopy in combination with hydrogen-deuterium exchange. Results Leaves were clearly more degradable by lignocellulolytic enzymes than stems, and it was demonstrated that xylose removal was more linked to glucose yield for stems than for leaves. Comparing the locations of water in leaf and stem by low field NMR and FT-IR revealed that the glucan hydroxyl groups in leaves were more accessible to water than glucan hydroxyl groups in stems. No difference in crystallinity between leaf and stem was observed using wide angle x-ray diffraction. Hydrothermal pretreatment increased the accessibility towards water in stems but not in leaves. The results in this study indicate a correlation between the accessibility of glucan to water and to enzymes. Conclusions Enzymatic degradability of wheat straw anatomical fractions can be indicated by the accessibility of the hydroxyl groups to water. This suggests that water may be used to assess glucan accessibility in biomass samples. PMID:24860617

  7. Leaf number, water stress and carbon nutrition effects on poplar leaf growth

    E-print Network

    Paris-Sud XI, Université de

    Leaf number, water stress and carbon nutrition effects on poplar leaf growth J.P. Gaudillère area of a leaf is described by the number and the mean size of epidermal cells. Water stress, nitrogen at different levels in the process of leaf production. The main susceptible physio- logical mechanisms are cell

  8. Characterizing natural cellulose fibers from velvet leaf (Abutilon theophrasti) stems.

    PubMed

    Reddy, Narendra; Yang, Yiqi

    2008-05-01

    Velvet leaf (Abutilon theophrasti) that is currently considered a weed and an agricultural problem could be used as a source for high quality natural cellulose fibers. The fibers obtained from the velvet leaf stems are mainly composed of approximately 69% cellulose and 17% lignin. The single cells in the fiber have lengths of approximately 0.9 mm, shorter than those in common bast fibers, hemp and kenaf. However, the widths of single cells in velvet leaf fibers are similar to the single cells in hemp and kenaf. The fibers exhibited breaking tenacity from 2.4 to 3.9 g/denier (325-500 MPa), breaking elongation of 1.6-2.4% and Young's modulus of 140-294 g/denier (18-38 GPa). Overall, velvet leaf fibers have properties similar to that of common bast fibers such as hemp and kenaf. Velvet leaves fibers could be processed on the current kenaf processing machineries for textile, composite, automotive and other fibrous applications. PMID:17583497

  9. Bacterial leaf and stem blight of safflower in M. Afazal AKHTAR M. Siddique MIRZA M. ASLAM

    E-print Network

    Boyer, Edmond

    NOTE Bacterial leaf and stem blight of safflower in Pakistan M. Afazal AKHTAR M. Siddique MIRZA M SUMMARY Bacterial leaf and stem blight disease on safflower (Carthamus tinctorus L.) was detected in 1985 to be the first identification of this bacterium on safflower from Pakistan. Additional key words : Pseudomonas

  10. First Report of Myrothecium roridum Causing Leaf and Stem Rot Disease on Peperomia quadrangularis in Korea.

    PubMed

    Han, Kyung-Sook; Choi, Seung-Kook; Kim, Hyeong-Hwan; Lee, Sung-Chan; Park, Jong-Han; Cho, Myoung-Rae; Park, Mi-Jeong

    2014-06-01

    In 2010, symptoms of leaf and stem rot were observed on potted plants (Peperomia quadrangularis) in a greenhouse in Yongin, Korea. The causative pathogen was identified as Myrothecium roridum based on morphological data, internal transcribed spacer sequence analysis, and pathogenicity test. To our knowledge, this is the first report of M. roridum causing leaf and stem rot disease on P. quadrangularis in Korea and elsewhere worldwide. PMID:25071393

  11. First Report of Myrothecium roridum Causing Leaf and Stem Rot Disease on Peperomia quadrangularis in Korea

    PubMed Central

    Han, Kyung-Sook; Choi, Seung-Kook; Kim, Hyeong-Hwan; Lee, Sung-Chan; Park, Jong-Han; Cho, Myoung-Rae

    2014-01-01

    In 2010, symptoms of leaf and stem rot were observed on potted plants (Peperomia quadrangularis) in a greenhouse in Yongin, Korea. The causative pathogen was identified as Myrothecium roridum based on morphological data, internal transcribed spacer sequence analysis, and pathogenicity test. To our knowledge, this is the first report of M. roridum causing leaf and stem rot disease on P. quadrangularis in Korea and elsewhere worldwide. PMID:25071393

  12. Identification and correction of spectral contamination in 2 O measured in leaf, stem, and soil water

    E-print Network

    Minnesota, University of

    correction curves for d18 O and d2 H. The contamination effects of different sample types (leaf, stem, soil. There was no contamination observed in soil water. Cleaning plant samples with activated charcoal had minimal effectsIdentification and correction of spectral contamination in 2 H/1 H and 18 O/16 O measured in leaf

  13. Separating soil and leaf water 18O isotopic signals in plant stem cellulose

    Microsoft Academic Search

    Leonel da Silveira Lobo Sternberg; William T. Anderson; Kanema Morrison

    2003-01-01

    The oxygen-18 signal of soil and leaf water are both recorded in heterotrophically synthesized plant stem cellulose. Presently, these signals can only be teased apart with modeling and assumptions on the nature of the isotopic enrichment of leaf water. A method by which these two signals are chemically separated and analyzed is tested here. Heterotrophically synthesized cellulose from germinating seeds

  14. Pretreatment with scutellaria baicalensis stem-leaf total flavonoid prevents cerebral ischemia-reperfusion injury.

    PubMed

    Zhao, Shumin; Kong, Wei; Zhang, Shufeng; Chen, Meng; Zheng, Xiaoying; Kong, Xiangyu

    2013-12-01

    Pretreatment with scutellaria baicalensis stem-leaf total flavonoid has protective effects against ischemia and attenuates myocardial ischemia-reperfusion injury. In this study, rats were given scutellaria baicalensis stem-leaf total flavonoid intragastrically at 50, 100, and 200 mg/kg per day for 7 days before focal cerebral ischemia-reperfusion injury models were established using the suture method. We then determined the protective effects of scutellaria baicalensis stem-leaf total flavonoid pretreatment on focal cerebral ischemia-reperfusion injury. Results showed that neurological deficit scores increased, infarct volumes enlarged, apoptosis increased and Bcl-2 and Bax protein expression were upregulated at 24 hours after reperfusion. Pretreatment with scutellaria baicalensis stem-leaf total flavonoid at any dose lowered the neurological deficit scores, reduced the infarct volume, prevented apoptosis in hippocampal cells, attenuated neuronal and blood-brain barrier damage and upregulated Bcl-2 protein expression but inhibited Bax protein expression. Doses of 100 and 200 mg/kg were the most efficacious. Our findings indicate that pretreatment with scutellaria baicalensis stem-leaf total flavonoid at 100 and 200 mg/kg can improve the neurological functions and have preventive and protective roles after focal cerebral ischemia-reperfusion injury. PMID:25206639

  15. Sorghum mutant RG displays antithetic leaf shoot lignin accumulation resulting in improved stem saccharification properties

    PubMed Central

    2013-01-01

    Background Improving saccharification efficiency in bioenergy crop species remains an important challenge. Here, we report the characterization of a Sorghum (Sorghum bicolor L.) mutant, named REDforGREEN (RG), as a bioenergy feedstock. Results It was found that RG displayed increased accumulation of lignin in leaves and depletion in the stems, antithetic to the trend observed in wild type. Consistent with these measurements, the RG leaf tissue displayed reduced saccharification efficiency whereas the stem saccharification efficiency increased relative to wild type. Reduced lignin was linked to improved saccharification in RG stems, but a chemical shift to greater S:G ratios in RG stem lignin was also observed. Similarities in cellulose content and structure by XRD-analysis support the correlation between increased saccharification properties and reduced lignin instead of changes in the cellulose composition and/or structure. Conclusion Antithetic lignin accumulation was observed in the RG mutant leaf-and stem-tissue, which resulted in greater saccharification efficiency in the RG stem and differential thermochemical product yield in high lignin leaves. Thus, the red leaf coloration of the RG mutant represents a potential marker for improved conversion of stem cellulose to fermentable sugars in the C4 grass Sorghum. PMID:24103129

  16. Antibacterial activity of stem and leaf extract of Kedrostis foetidissima (Jacq.) Cogn.

    PubMed Central

    Priyavardhini, S.; Gowri, S. Shyamala; Vasantha, K.; Umadevi, M.

    2008-01-01

    The present study aimed at evaluating the antimicrobial activity of chloroform extracts of stem and leaf of Kedrostis foetidissima (jacq.) cogn. (Cucurbitaceae) against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Serratia marcescens and Klebsiella pneumoniae. was carried out using agar disc diffusion technique. The results revealed that the chloroform extract of stem presented the highest zone of inhibition against Pseudomonas aeruginosa others show significant zone of inhibition. PMID:22557304

  17. Leaf and Stem Area Relationships to Masses and Their Height Distributions in Native Grasses

    Microsoft Academic Search

    Amare Retta; Dean V. Armbrust; Lawrence J. Hagen; Edward L. Skidmore

    2000-01-01

    i A recently developed wind erasion model (wind erosion prediction system, WEPS) for mop lands is being extended for estimating soil emsion from rangelands, military lands, and desert emsystem,. Wind velocity near the soil surface is calculated as a function of the serial distribution of stem silhouette area and leaf ares of both live plants and standing residue. Grasses either

  18. Antioxidant and anti-dermatophytic properties leaf and stem bark of Xylosma longifolium clos

    PubMed Central

    2013-01-01

    Background The present study was carried out to assess the phytochemical and anti-dermatophytic effect of the leaf and bark extracts of Xylosma longifolium Clos. The leaf and stem bark are used by the indigenous people of Manipur, India for treatment of skin diseases. Methods The leaves and stem barks of Xylosma longifolium were extracted using petroleum ether, chloroform and methanol respectively. The different extracts of each plant parts were tested for antioxidant activity using DPPH assay. The phenolic content was assayed using Folin-Ciocalteu colorimetric method. Each extracts was further analysed by RP-HPLC to quantify some individual flavonoid components. The anti-dermatophytic activity was evaluated both by agar diffusion method and micro wells dilution method against the Microsporum boullardii MTCC 6059, M. canis (MTCC 2820 and MTCC 32700), M. gypseum MTCC 2819, Trichophyton ajelloi MTCC 4878, T. rubrum (MTCC 296 and MTCC 3272). Results The free radical scavenging activity values were ranged from 0.7 to 1.41 mg/ml and 0.6 to 1.23 mg/ml, respectively for leaf and stem bark extracts. The amount of total phenolic contents of the extracts occurred in both leaf and bark in the range of 12 to 56.6 mg GAE/100 g and 16 to 58 mg GAE/100 g respectively. RP-HPLC analysis for flavonoids revealed the presence of two major flavonoid compounds, rutin and catechin. Kaempferol was in trace or absent. Methanol leaf extract showed significant low inhibitory effect against tested fungus Trichophyton ajelloi MTCC 4878 (0.140625 mg/ml) as the most sensitive. These finding suggest that the methanol leaf extract tested contain compounds with antimicrobial properties. Conclusion The results of our study may partially justify the folkloric uses on the plant studied and further provide an evidence that the leaf extract of Xylosma longifolium might be indeed a potential sources of antimicrobial agents. PMID:23819459

  19. Stem rust, leaf rust, and stripe rust comprise a complex of diseases that reduces wheat and barley

    E-print Network

    Murray, Timothy D.

    Stem rust, leaf rust, and stripe rust comprise a complex of diseases that reduces wheat and barley with current wheat varieties, crop growth stage, and weather conditions. Stem rust has been present in North with the greatest losses in the Great Plains. More local- ized outbreaks of wheat stem rust occurred in the southern

  20. Changes in clonal poplar leaf chemistry caused by stem galls alter herbivory and leaf litter decomposition.

    PubMed

    Künkler, Nora; Brandl, Roland; Brändle, Martin

    2013-01-01

    Gall-inducing insects are highly specialized herbivores that modify the phenotype of their host plants. Beyond the direct manipulation of plant morphology and physiology in the immediate environment of the gall, there is also evidence of plant-mediated effects of gall-inducing insects on other species of the assemblages and ecosystem processes associated with the host plant. We analysed the impact of gall infestation by the aphid Pemphigus spirothecae on chemical leaf traits of clonal Lombardy poplars (Populus nigra var. italica) and the subsequent effects on intensity of herbivory and decomposition of leaves across five sites. We measured the herbivory of two feeding guilds: leaf-chewing insects that feed on the blade (e.g. caterpillars and sawfly larvae) and skeletonising insects that feed on the mesophyll of the leaves (e.g. larvae of beetles). Galled leaves had higher phenol (35%) and lower nitrogen and cholorophyll contents (35% respectively 37%) than non-galled leaves, and these differences were stronger in August than in June. Total herbivory intensity was 27% higher on galled than on non-galled leaves; damage by leaf chewers was on average 61% higher on gall infested leaves, whereas damage by skeletonising insects was on average 39% higher on non-galled leaves. After nine months the decomposition rate of galled leaf litter was 15% lower than that of non-galled leaf litter presumably because of the lower nitrogen content of the galled leaf litter. This indicated after-life effects of gall infestation on the decomposers. We found no evidence for galling x environment interactions. PMID:24260333

  1. Changes in Clonal Poplar Leaf Chemistry Caused by Stem Galls Alter Herbivory and Leaf Litter Decomposition

    PubMed Central

    Künkler, Nora; Brandl, Roland; Brändle, Martin

    2013-01-01

    Gall-inducing insects are highly specialized herbivores that modify the phenotype of their host plants. Beyond the direct manipulation of plant morphology and physiology in the immediate environment of the gall, there is also evidence of plant-mediated effects of gall-inducing insects on other species of the assemblages and ecosystem processes associated with the host plant. We analysed the impact of gall infestation by the aphid Pemphigus spirothecae on chemical leaf traits of clonal Lombardy poplars (Populus nigra var. italica) and the subsequent effects on intensity of herbivory and decomposition of leaves across five sites. We measured the herbivory of two feeding guilds: leaf-chewing insects that feed on the blade (e.g. caterpillars and sawfly larvae) and skeletonising insects that feed on the mesophyll of the leaves (e.g. larvae of beetles). Galled leaves had higher phenol (35%) and lower nitrogen and cholorophyll contents (35% respectively 37%) than non-galled leaves, and these differences were stronger in August than in June. Total herbivory intensity was 27% higher on galled than on non-galled leaves; damage by leaf chewers was on average 61% higher on gall infested leaves, whereas damage by skeletonising insects was on average 39% higher on non-galled leaves. After nine months the decomposition rate of galled leaf litter was 15% lower than that of non-galled leaf litter presumably because of the lower nitrogen content of the galled leaf litter. This indicated after-life effects of gall infestation on the decomposers. We found no evidence for galling x environment interactions. PMID:24260333

  2. Comparative effects of plant growth regulators on leaf and stem explants of Labisia pumila var. alata

    PubMed Central

    Ling, Anna Pick Kiong; Tan, Kinn Poay; Hussein, Sobri

    2013-01-01

    Objective: Labisia pumila var. alata, commonly known as ‘Kacip Fatimah’ or ‘Selusuh Fatimah’ in Southeast Asia, is traditionally used by members of the Malay community because of its post-partum medicinal properties. Its various pharmaceutical applications cause an excessive harvesting and lead to serious shortage in natural habitat. Thus, this in vitro propagation study investigated the effects of different plant growth regulators (PGRs) on in vitro leaf and stem explants of L. pumila. Methods: The capabilities of callus, shoot, and root formation were evaluated by culturing both explants on Murashige and Skoog (MS) medium supplemented with various PGRs at the concentrations of 0, 1, 3, 5, and 7 mg/L. Results: Medium supplemented with 3 mg/L indole-3-butyric acid (IBA) showed the optimal callogenesis from both leaf and stem explants with (72.34±19.55)% and (70.40±14.14)% efficacy, respectively. IBA was also found to be the most efficient PGR for root induction. A total of (50.00±7.07)% and (77.78±16.47)% of root formation were obtained from the in vitro stem and leaf explants after being cultured for (26.5±5.0) and (30.0±8.5) d in the medium supplemented with 1 and 3 mg/L of IBA, respectively. Shoot formation was only observed in stem explant, with the maximum percentage of formation ((100.00±0.00)%) that was obtained in 1 mg/L zeatin after (11.0±2.8) d of culture. Conclusions: Callus, roots, and shoots can be induced from in vitro leaf and stem explants of L. pumila through the manipulation of types and concentrations of PGRs. PMID:23825148

  3. Ecological differentiation in xylem cavitation resistance is associated with stem and leaf structural traits.

    PubMed

    Markesteijn, Lars; Poorter, Lourens; Paz, Horacio; Sack, Lawren; Bongers, Frans

    2011-01-01

    Cavitation resistance is a critical determinant of drought tolerance in tropical tree species, but little is known of its association with life history strategies, particularly for seasonal dry forests, a system critically driven by variation in water availability. We analysed vulnerability curves for saplings of 13 tropical dry forest tree species differing in life history and leaf phenology. We examined how vulnerability to cavitation (P??) related to dry season leaf water potentials and stem and leaf traits. P??-values ranged from -0.8 to -6.2 MPa, with pioneers on average 38% more vulnerable to cavitation than shade-tolerants. Vulnerability to cavitation was related to structural traits conferring tissue stress vulnerability, being negatively correlated with wood density, and surprisingly maximum vessel length. Vulnerability to cavitation was negatively related to the Huber-value and leaf dry matter content, and positively with leaf size. It was not related to SLA. We found a strong trade-off between cavitation resistance and hydraulic efficiency. Most species in the field were operating at leaf water potentials well above their P??, but pioneers and deciduous species had smaller hydraulic safety margins than shade-tolerants and evergreens. A trade-off between hydraulic safety and efficiency underlies ecological differentiation across these tropical dry forest tree species. PMID:20946587

  4. Fertilizer Facts: April 1997, Number 16 Correcting Physiologic Leaf Spot Damage in

    E-print Network

    Lawrence, Rick L.

    Fertilizer Facts: April 1997, Number 16 Correcting Physiologic Leaf Spot Damage in `Redwin and Environmental Sciences Dept. Montana State University A winter wheat leaf spot complex of unknown origin referred to as a "physiological leaf spot" by plant pathologists and breeders, meaning it could

  5. Identification and correction of spectral contamination in D/H and 18 measured in leaf, stem, and soil water2

    E-print Network

    Minnesota, University of

    . The contamination effects of29 different sample types (leaf, stem, soil) and different species from agricultural.17 to 13.70 for 2 H and 0.47 to 7.97 for 18 O.32 There was no contamination observed in soil waterIdentification and correction of spectral contamination in D/H and 18 O/16 O1 measured in leaf

  6. Scutellaria baicalensis stem-leaf total flavonoid reduces neuronal apoptosis induced by amyloid beta-peptide (25-35).

    PubMed

    Wang, Ruiting; Shen, Xingbin; Xing, Enhong; Guan, Lihua; Xin, Lisheng

    2013-04-25

    Scutellaria baicalensis stem-leaf total flavonoid might attenuate learning/memory impairment and neuronal loss in rats induced by amyloid beta-peptide. This study aimed to explore the effects of Scutellaria baicalensis stem-leaf total flavonoid on amyloid beta-peptide-induced neuronal apoptosis and the expression of apoptosis-related proteins in the rat hippocampus. Male Wistar rats were given intragastric administration of Scutellaria baicalensis stem-leaf total flavonoid, 50 or 100 mg/kg, once per day. On day 8 after administration, 10 ?g amyloid beta-peptide (25-35) was injected into the bilateral hippocampus of rats to induce neuronal apoptosis. On day 20, hippocampal tissue was harvested and probed with the terminal deoxyribonucleotidyl transferase-mediated biotin-16-dUTP nick-end labeling assay. Scutellaria baicalensis stem-leaf total flavonoid at 50 and 100 mg/kg reduced neuronal apoptosis induced by amyloid beta-peptide (25-35) in the rat hippocampus. Immunohistochemistry and western blot assay revealed that expression of the pro-apoptotic protein Bax, cytochrome c and caspase-3 was significantly diminished by 50 and 100 mg/kg Scutellaria baicalensis stem-leaf total flavonoid, while expression of the anti-apoptotic protein Bcl-2 was increased. Moreover, 100 mg/kg Scutellaria baicalensis stem-leaf total flavonoid had a more dramatic effect than the lower dosage. These experimental findings indicate that Scutellaria baicalensis stem-leaf total flavonoid dose-dependently attenuates neuronal apoptosis induced by amyloid beta-peptide in the hippocampus, and it might mediate this by regulating the expression of Bax, cytochrome c, caspase-3 and Bcl-2. PMID:25206402

  7. Effects of Daniellia oliveri stem bark and leaf extracts on rat skeletal muscle.

    PubMed

    Onwukaeme, N D; Lot, T Y; Udoh, F V

    1999-08-01

    The stem bark and leaves of Daniellia oliveri were screened phytochemically and the effects of their respective methanol extracts on the skeletal muscle of rats were investigated using the isolated phrenic nerve hemidiaphragm muscle preparation. Both were found to contain tannins, cardiac and saponin glycosides. In addition, the bark, but not leaves, contained cyanogenetic glycosides. The methanol extracts were found to possess neuromuscular blocking properties. The leaf extract appeared to act primarily by inhibiting the influx of extracellular Ca(2+) principally by inhibiting K(+) channels. The inhibitory action of the bark extract appeared to be mediated by interference with transmitter release and an action on multiple sites. PMID:10441783

  8. Effect of cytokinins on shoot regeneration from cotyledon and leaf segment of stem mustard ( Brassica juncea var. tsatsai )

    Microsoft Academic Search

    De-Ping Guo; Zhu-Jun Zhu; Xiao-Xiang Hu; Si-Jun Zheng

    2005-01-01

    Cotyledon and leaf segments of stem mustard (Brassica juncea var. tsatsai) were cultured on Murashige and Skoog medium supplemented with various concentrations of different cytokinins [6-benzyladenine (BA), N-(2-chloro-4-pyridyl)-n-phenylurea (CPPU), 6-furfurylaminopurine (KT) and thidiazuron (TDZ)] in combinations with different levels of ?-naphthalene acetic acid (NAA). The shoot regeneration frequency of cotyledon and leaf segment was dependent on the kinds and concentrations

  9. Separating soil and leaf water 18O isotopic signals in plant stem cellulose

    NASA Astrophysics Data System (ADS)

    Sternberg, Leonel da Silveira Lobo; Anderson, William T.; Morrison, Kanema

    2003-07-01

    The oxygen-18 signal of soil and leaf water are both recorded in heterotrophically synthesized plant stem cellulose. Presently, these signals can only be teased apart with modeling and assumptions on the nature of the isotopic enrichment of leaf water. A method by which these two signals are chemically separated and analyzed is tested here. Heterotrophically synthesized cellulose from germinating seeds having a mixture of isotopic signals from the reserve carbohydrate (starch) and that of the water during cellulose synthesis was hydrolyzed and the resulting glucose converted to glucose phenylosazone. The analysis of the 18O/ 16O ratios of cellulose and of glucose phenylosazone were used to calculate the oxygen isotope ratio of the oxygen attached to the second carbon of the glucose moieties of the cellulose molecule. The calculated ? 18O value of this oxygen was highly correlated with that of the water available for cellulose synthesis showing a nearly one-to-one relationship (slope = 1.027) and leading to the conclusion that it completely exchanges with water during heterotrophic cellulose synthesis. Once this method is refined so as to increase precision, it will be possible to derive the ? 18O values of soil water available to plants from the oxygen isotope analysis of stem cellulose and its derivative.

  10. Microscopic characters of the leaf and stem of Lavandula dentata L. (Lamiaceae).

    PubMed

    do Rocio Duarte, Márcia; Carvalho de Souza, Danielle

    2014-08-01

    Lavandula dentata L. is an aromatic plant used in folk medicine for different purposes and, for this reason, phytochemical surveys have been carried out in the search for bioactive substances aiming to support its uses. Since there is little knowledge on the structural aspects of L. dentata, this work has studied the anatomical characters of the leaf and stem using light and scanning electron microscopy, in order to assist the species identification. As a result, there are different types of trichomes: capitate glandular with uni- or bicellular head, peltate glandular with multicellular head, and branched non-glandular. The leaf is hypostomatic showing diacytic stomata. The epidermis is uniseriate and coated with striate cuticle. The mesophyll is dorsiventral and the midrib is concave-convex and traversed by a single collateral vascular bundle. The stem is quadrangular and has alternating strands of collenchyma and cortical parenchyma as well as a typical endodermis in the cortex. The phloem and xylem cylinders are traversed by narrow rays and there is an incomplete sclerenchymatic sheath adjoining the phloem. These results are a novelty for the species and contribute to distinguish it from other lavenders. PMID:24861363

  11. The effect of pelleting on the voluntary intake and digestibility of leaf and stem fractions of three grasses.

    PubMed

    Laredo, M A; Minson, D J

    1975-03-01

    1. Leaf is eaten in greater quantities than stem of similar digestibility. To determine whether this difference is caused by physical or chemical factors, leaf and stem fractions from Digitaria decumbens, Chloris gayana and Setaria splendida were fed ad lib, to sheep in the chopped and pelleted forms. Pellets were made from leaf and stem which had been ground through a screen with 3 mm holes. All sheep received a protein and mineral supplement. 2. Voluntary intake of chopped leaf was 34 percent higher than that of the chopped stem fraction (40-3 and 30-0 g/kg body-weight 0-75 respectively, P smaller than 0.01) although dry matter digestibility ratios were similar (0-478 and 0-450 respectively, P greater than 0-05). The higher intake of leaf was associated with a larger surface area (13 400 and 5200 mm2/g for chopped leaf and stem respectively), lower bulk density (60 and 180 kg/m3 respectively) and lower neutral-detergent fibre (706 and 724 g/kg respectively), acid-detergent fibre (383 and 413 g/kg respectively) and lignin (42 and 59 g/kg respectively) contents. Chopped leaf was retained in the reticulo-rumen for a shorter time than the stem fraction (19.9 and 26.4 h respectively). 3. Grinding and pelleting increased the voluntary intake of the leaf fraction by 88 percent and the stem fraction by 60 percent. This increased voluntary intake caused by grinding and pelleting was not accompanied by any significant changes in the chemical composition of the diet. Grinding and pelleting reduced the time that the food was retained in the reticulo-rumen and this change appeared sufficient to account for the observed increases in voluntary intake. 4. It was concluded that the higher intake of the leaf fraction of grasses is caused by differences in retention time of food in the reticulo-rumen. These differences in retention time are caused by differences in physical properties and not chemical composition. PMID:1115758

  12. Control of Leaf and Stem Growth in Light-grown Pea Seedlings by Two High Irradiance Responses 1

    PubMed Central

    Elliott, William M.

    1979-01-01

    The control exerted by light on leaf and stem growth in light-grown Alaska pea seedlings was studied during the main photoperiod. Two high irradiance responses were observed. The action spectrum for one had a single sharp peak at 600 nanometers. The action spectrum for the other showed a broad peak between 440 and 470 nanometers. These two light responses must be activated simultaneously for any inhibition of stem growth or promotion of leaf growth. Both action spectra may be explained in terms of the high irradiance response of phytochrome. PMID:16660822

  13. Brassica rapa stock description: F1 and F2 Non-purple stem, Yellow-green leaf stocks

    NSDL National Science Digital Library

    The Wisconsin Fast Plants Program

    PDF containing seed stock profile information for and illustration of the F1 and F2 Non-Purple Stem, Yellow-Green Leaf variety of Brassica rapa (Fast Plants). This also includes some brief suggestions for their use as a model organism in teaching Mendelian genetics with a monohybrid cross using Wisconsin Fast Plants.

  14. Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation

    E-print Network

    Sack, Lawren

    Coordination of stem and leaf hydraulic conductance in southern California shrubs: a test of the hydraulic segmentation hypothesis Alexandria L. Pivovaroff1 , Lawren Sack2 and Louis S. Santiago1 1 2014 New Phytologist (2014) 203: 842­850 doi: 10.1111/nph.12850 Key words: chaparral, hydraulic

  15. The effect of leaf presence on the rooting of stem cutting of bitter melon and on changes in polyamine levels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The study was conducted to investigate the optimal hormone treatment for rooting in bitter melon and the effect of defoliation on rooting and polyamine levels. Commercial preparation (diluted 1:10 and 1: 20) gave extensive rooting within five days after treatment. The presence of leaf with the stem ...

  16. The effect of maleic hydrazide and 2,4-dichlorophenoxyacetic acid on the carbohydrate content and leaf and stem rust response of wheat 

    E-print Network

    Lyles, William Earl

    1958-01-01

    THE EFFECT OF MALEIC HYDRAZIDE AND 2, 4-DICHLOROPHENOXYACETIC ACID ON THE CARBOHYDRATE CONTENT AND LEAF AND STEM RUST RESPONSE OF WHEAT A Thesis by WILLIAM EARL LYLES Submitted to the Graduate School of the Agricultural and Mechanical College... of Texas in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE January 1958 Major Subject; Plant Pathology THE EFFECT OF MALEIC HYDRAZIDE AND 2, 4-DICHLOROPHENOXYACETIC ACID ON THE CARBOHYDRATE CONTENT AND LEAF AND STEM RUST...

  17. Sedative effects of Arachis hypogaea L. stem and leaf extracts on sleep-deprived rats

    PubMed Central

    ZU, XIAOYAN; ZHANG, ZHENYA; XIONG, GUANGQUAN; LIAO, TAO; QIAO, YU; LI, YITING; GENG, SHENGRONG; LI, XIN

    2013-01-01

    Arachis hypogaea L. stem and leaf extracts (AHSLE) are reputed to aid sleep. The purpose of this study was to evaluate the sedative effects of AHSLE on sleep-deprived (SD) rats and the effect on energy system pathways. Furthermore, we analyzed the essential oil components of Arachis hypogaea L. stems and leaves (AHSL) to explain the sedative effects. AHSLE were obtained by extracting AHSL twice with water at 98°C for 3 h. Animal experiments were performed in the Laboratory Animal Resource Center, University of Tsukuba, Japan, and the levels of neurotransmitters were analyzed by high performance liquid chromatography (HPLC). The essential oil of the AHSL was obtained by simultaneous distillation and extraction (SDE) and analyzed by gas chromatography-mass spectrometry (GC-MS). Following treatment with AHSLE, the adenosine triphosphate (ATP) levels of the SD rats increased, which is a different effect from that previously observed in freely behaving rats. Adenosine (Ad) were not elevated by AHSLE uniformly throughout the brain, but accumulated in site-specific and time-prolonged manners. Following GC-MS analysis of the AHSL essential oil, a total of 37 compounds were identified; the major components were linalool (16.17%, which has sedative-like activity), n-hexadecanoic acid (16.42%), and 1-octen-3-ol (8.48%; a product of linalool decomposition). AHSLE affect the target neurotransmitters related to the rat circadian rhythms in specific brain regions, suggesting that AHSLE have the potential to increase sleep during the SD phase, and the sedative effects of AHSLE may be due to high levels of linalool and its decomposition products. AHSLE are potentially useful as sedatives or sleep aids in hypnotic therapy. PMID:24137234

  18. Sedative effects of Arachis hypogaea L. stem and leaf extracts on sleep-deprived rats.

    PubMed

    Zu, Xiaoyan; Zhang, Zhenya; Xiong, Guangquan; Liao, Tao; Qiao, Yu; Li, Yiting; Geng, Shengrong; Li, Xin

    2013-08-01

    Arachis hypogaea L. stem and leaf extracts (AHSLE) are reputed to aid sleep. The purpose of this study was to evaluate the sedative effects of AHSLE on sleep-deprived (SD) rats and the effect on energy system pathways. Furthermore, we analyzed the essential oil components of Arachis hypogaea L. stems and leaves (AHSL) to explain the sedative effects. AHSLE were obtained by extracting AHSL twice with water at 98°C for 3 h. Animal experiments were performed in the Laboratory Animal Resource Center, University of Tsukuba, Japan, and the levels of neurotransmitters were analyzed by high performance liquid chromatography (HPLC). The essential oil of the AHSL was obtained by simultaneous distillation and extraction (SDE) and analyzed by gas chromatography-mass spectrometry (GC-MS). Following treatment with AHSLE, the adenosine triphosphate (ATP) levels of the SD rats increased, which is a different effect from that previously observed in freely behaving rats. Adenosine (Ad) were not elevated by AHSLE uniformly throughout the brain, but accumulated in site-specific and time-prolonged manners. Following GC-MS analysis of the AHSL essential oil, a total of 37 compounds were identified; the major components were linalool (16.17%, which has sedative-like activity), n-hexadecanoic acid (16.42%), and 1-octen-3-ol (8.48%; a product of linalool decomposition). AHSLE affect the target neurotransmitters related to the rat circadian rhythms in specific brain regions, suggesting that AHSLE have the potential to increase sleep during the SD phase, and the sedative effects of AHSLE may be due to high levels of linalool and its decomposition products. AHSLE are potentially useful as sedatives or sleep aids in hypnotic therapy. PMID:24137234

  19. Striking similarities between the nucleotide sequence and genome organization of citrus tatter leaf and apple stem grooving capilloviruses

    Microsoft Academic Search

    N. Yoshikawa; M. Imaizumi; T. Takahashi; N. Inouye

    1993-01-01

    The sequence of the T-terminal 2956 nucleotides, excluding the poly(A) tail, of the citrus tatter leaf virus (CTLV) genome was determined and compared with that of the apple stem grooving virus (ASGV) genome. The sequence of the 3'-terminal region of CTLV contains two overlapping open reading frames (ORFs) and a 3'-terminal non-coding region of 142 nucleotides. The long, incomplete ORF1

  20. Phenolic contents and antioxidant activities of bitter gourd ( Momordica charantia L.) leaf, stem and fruit fraction extracts in vitro

    Microsoft Academic Search

    Jittawan Kubola; Sirithon Siriamornpun

    2008-01-01

    Bitter gourd (Momordica charantia L.) has long been regarded as a food and medicinal plant. We investigated the antioxidant activity of the water extract of leaf, stem and fruit fractions by several in vitro systems of assay, namely DPPH radical-scavenging activity, hydroxyl radical-scavenging activity, ?-carotene–linoleate bleaching assay, ferric reducing\\/antioxidant power (FRAP) assay and total antioxidant capacity. Total phenolic content was

  1. Isothiocyanate profile and selective antibacterial activity of root, stem, and leaf extracts derived from Raphanus sativus L.

    PubMed

    Beevi, Syed Sultan; Mangamoori, Lakshmi Narasu; Dhand, Vivek; Ramakrishna, Damaraju Siva

    2009-01-01

    Acetone and hexane extracts derived from the root, stem, and leaf of Raphanus sativus were investigated for their antibacterial activity against foodborne and resistant pathogens, such as Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Salmonella typhimurium, Enterobacter aerogenes, Enterobacter cloacae, and Escherichia coli. Total and individual isothiocyanate (ITC) components and their relationship with the antibacterial activity of R. sativus were also evaluated. Both acetone and hexane fractions of root, stem, and leaf exhibited selective antibacterial activity against the organisms tested. Antibacterial activity was strongest in the acetone fraction of root with larger zone of inhibition and lower minimum inhibitory concentration. The results obtained were comparable to that seen with standard antibiotics. Of the different parts of R. sativus studied, root tended to be more active than the stem and leaf extracts in inhibiting the bacterial growth. Gas chromatographic analysis revealed the presence of variable amounts of five different ITCs such as allyl isothiocyanate (AITC), phenyl isothiocyanate (PITC), benzyl isothiocyanate (BITC), phenethyl isothiocyanate, and 4-(methylthio)-3-butenyl isothiocyanate (MTBITC) in different parts of the plant. The low linear correlation between the total ITC content and antibacterial activity implied that bacterial growth inhibitory ability of R. sativus was not dependent on the total ITC content. However, the antibacterial activity of R. sativus was well correlated with AITC, PITC, and BITC for all organisms except for Enteroc. faecalis, whose inhibitory effect was more related to MTBITC. PMID:19182965

  2. Arachis hypogaea L. stem and leaf extract improves the sleep behavior of pentobarbital-treated rats

    PubMed Central

    ZU, XIAO-YAN; XIONG, GUANG-QUAN; GENG, SHENG-RONG; LIAO, TAO; LI, XIN; ZHANG, ZHEN-YA

    2014-01-01

    This study was conducted to evaluate the sedative effects of Arachis hypogaea L. stem and leaf extract (AHSLE) and determine its effect pathways through ?-aminobutyric acid (GABA)-gated channels on male Sprague-Dawley rats treated with pentobarbital. AHSLE was obtained from 98°C water (3 h, extracted twice). AHSLE and flumazenil (a GABA type A receptor antagonist) were administered to the rats orally, whereas pentobarbital sodium and muscimol (a GABA type A receptor agonist) were administered intraperitoneally (i.p.). The results demonstrated that AHSLE decreased sleep latency and increased sleep time in pentobarbital-treated rats (50 mg/kg, i.p.). The coadministration of AHSLE and muscimol (0.05 mg/kg) significantly increased sleep time and reduced sleep latency in pentobarbital-treated rats and these actions were significantly antagonized by flumazenil at a dose of 3.5 mg/kg. These results indicated that AHSLE improved the sleep behavior in pentobarbital-treated rats, possibly through GABA-gated channel-related mechanisms. PMID:24748980

  3. LEAF MARGIN INFLORESCENCE

    E-print Network

    Holland, Jeffrey

    { LEAF BLADE LEAF MARGIN PETIOLE INFLORESCENCE WS-27-W Guidelines for Submitting Digital Plant RAGWEED VELVETLEAF Leaf arrangement on the plant stem. Alternate Opposite Alternate CANADA THISTLE COMMON RAGWEED VELVETLEAF Leaf attachment to the plant stem. Sessile Petiole Petiole CANADA THISTLE COMMON

  4. Transient changes in transpiration, and stem and soil CO 2 efflux in longleaf pine ( Pinus palustris Mill.) following fire-induced leaf area reduction

    Microsoft Academic Search

    Barton D. Clinton; Chris A. Maier; Chelcy R. Ford; Robert J. Mitchell

    In 20-year-old longleaf pine, we examined short-term effects of reduced live leaf area (A\\u000a L) via canopy scorching on sap flow (Q; kg H2O h?1), transpiration per unit leaf area (E\\u000a L; mm day?1), stem CO2 efflux (R\\u000a stem; ?mol m?2 s?1) and soil CO2 efflux (R\\u000a soil; ?mol m?2 s?1) over a 2-week period during early summer. R\\u000a stem and Q were measured at two positions

  5. Analysis of salinity effects on basil leaf surface area, photosynthetic activity, and growth

    Microsoft Academic Search

    Houneida AttiaChayma; Chayma Ouhibi; Ahlem Ellili; Najoua Msilini; Ghaïth Bouzaïen; Najoua Karray; Mokhtar Lachaâl

    2011-01-01

    Basil (Ocimum basilicum L.) seedlings were cultured on liquid medium in controlled conditions. Two varieties differing in leaf size were compared.\\u000a When plants were 30 days old, the medium was supplemented with 50 mM NaCl. After 15 days of treatment, root, stem and leaf\\u000a biomass, leaf number, and leaf surface area were measured. Ion accumulation was determined in roots, stems, and leaves. Photosynthetic

  6. Cell Stem Cell Dynamic Changes in the Copy Number of Pluripotency

    E-print Network

    Shamir, Ron

    Cell Stem Cell Resource Dynamic Changes in the Copy Number of Pluripotency and Cell Proliferation University, Tel Aviv 69978, Israel 8Department of Anatomy and Neurobiology, Sue and Bill Gross Stem Cell 11Centro de Medicina Regenerativa de Barcelona, Barcelona E-08003, Spain 12International Stem Cell

  7. Sasa quelpaertensis Leaf Extract Inhibits Colon Cancer by Regulating Cancer Cell Stemness in Vitro and in Vivo

    PubMed Central

    Min, Soo Jin; Lim, Ji Ye; Kim, Haeng Ran; Kim, Se-Jae; Kim, Yuri

    2015-01-01

    A rare subpopulation of cancer cells, termed cancer stem cells (CSCs), may be responsible for tumor relapse and resistance to conventional chemotherapy. The development of a non-toxic, natural treatment for the elimination of CSCs is considered a strategy for cancer treatment with minimal side effects. In the present study, the potential for Sasa quelpaertensis leaf extract (SQE) and its two bioactive compounds, tricin and p-coumaric acid, to exert anti-CSC effects by suppressing cancer stemness characteristics were evaluated in colon cancer cells. CD133+CD44+ cells were isolated from HT29 and HCT116 cell lines using flow-activated cell sorting (FACs). SQE treatment was found to significantly suppress the self-renewal capacity of both cell lines. SQE treatment was also associated with the down-regulation of ?-catenin and phosphorylated GSK3?, while significantly enhancing cell differentiation by up-regulating CK20 expression and blocking the expression of several stem cell markers, including DLK1, Notch1, and Sox-2. In vivo, SQE supplementation suppressed tumor growth in a xenograft model by down-regulating stem cell markers and ?-catenin as well as HIF-1? signaling. Compared with two bioactive compounds of SQE, SQE exhibited the most effective anti-CSC properties. Taken together, these results provide evidence that SQE inhibits colon cancer by regulating the characteristics of CSCs. PMID:25941936

  8. Drought responses at leaf, stem and fine root levels of competitive Fagus sylvatica L. and Quercus petraea (Matt.) Liebl. trees in dry and wet years

    Microsoft Academic Search

    Ch Leuschner; K Backes; D Hertel; F Schipka; U Schmitt; O Terborg; M Runge

    2001-01-01

    The inter-annual variability of four growth-related parameters (light-saturated photosynthesis Amax, leaf area index L, annual stem diameter growth S, and fine root production P) was investigated together with various leaf water status parameters in adult Fagussylvatica and Quercuspetraea trees during five summers with weak, moderate or severe soil water deficit. Study aims were (i) to identify differences in drought sensitivity

  9. Structural characteristics of water-soluble polysaccharides from Rabdosia serra (MAXIM.) HARA leaf and stem and their antioxidant capacities.

    PubMed

    Lin, Lianzhu; Zhuang, Mingzhu; Zou, Linwu; Lei, Fenfen; Yang, Bao; Zhao, Mouming

    2012-11-15

    Water-soluble polysaccharides of Rabdosia serra leaf and stem were fractionated by ultrafiltration and DEAE-Sepharose fast flow chromatogram to obtain water (RSLP-I and RSSP-I), 0.1M NaCl (RSLP-II and RSSP-II) and 0.2M NaCl (RSLP-III and RSSP-III) eluates. Their molecular weights were determined by high performance gel permeation chromatography. Monosaccharide composition analysis indicated that the water eluates comprised of rhamnose, arabinose, xylose, mannose, glucose and galactose. The ascending percentage of galactose and descending percentage of glucose in the eluates were observed with the increase of NaCl concentration. The branched RSLP-I and RSSP-I were composed mainly of ?6)-Glcp-(1?, ?6)-Galp-(1?, and ?5)-Araf-(1? residues with the ratio of 15.0:4.2:3.8 and 5.5:6.4:3.5, respectively. However, a low level of 1,6-linked glucosyl was observed in RSLP-II, RSSP-II, RSLP-III and RSSP-III. The structural characteristics were further analysed by infrared spectrophotometry. The purified leaf and stem polysaccharides possessed moderate antioxidant capacities. PMID:22868152

  10. Protection of wheat against leaf and stem rust and powdery mildew diseases by inhibition of polyamine metabolism

    NASA Technical Reports Server (NTRS)

    Weinstein, L. H.; Osmeloski, J. F.; Wettlaufer, S. H.; Galston, A. W.

    1987-01-01

    In higher plants, polyamines arise from arginine by one of two pathways: via ornithine and ornithine decarboxylase or via agmatine and arginine decarboxylase but in fungi, only the ornithine decarboxylase pathway is present. Since polyamines are required for normal growth of microorganisms and plants and since the ornithine pathway can be irreversibly blocked by alpha-difluoromethylornithine (DFMO) which has no effect on arginine decarboxylase, fungal infection of green plants might be controlled by the site-directed use of such a specific metabolic inhibitor. DFMO at relatively low concentrations provided effective control of the three biotrophic fungal pathogens studied, Puccinia recondita (leaf rust), P. graminis f. sp. tritici (stem rust), and Erysiphe graminis (powdery mildew) on wheat (Triticum aestivum L.) Effective control of infection by leaf or stem rust fungi was obtained with sprays of DFMO that ranged from about 0.01 to 0.20 mM in experiments where the inhibitor was applied after spore inoculation. The powdery mildew fungus was somewhat more tolerant of DFMO, but good control of the pathogen was obtained at less than 1.0 mM. In general, application of DFMO after spore inoculation was more effective than application before inoculation. Less control was obtained following treatment with alpha-difluoromethylarginine (DFMA) but the relatively high degree of control obtained raises the possibility of a DFMA to DFMO conversion by arginase.

  11. An Immunocapture RT-PCR Procedure Using Apple stem grooving virus Antibodies Facilitates Molecular Genetic Characterization of Citrus tatter leaf virus from the Original Meyer Lemon Host

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A magnetic bead-based immonocapture system using polyclonal antiserum against Apple stem grooving virus (ASGV) successfully facilitated polymerase chain reaction (PCR) amplification of sequences from three Citrus tatter leaf virus (CTLV) isolates originally isolated from the citrus host Meyer lemon....

  12. The effect of development stage on chemical composition of alfalfa leaf and stem

    Microsoft Academic Search

    J. Markovic; J. Radovic; Z. Lugic; D. Sokolovic

    2007-01-01

    Content of crude protein and cell wall constituents in leaves and stems of alfalfa (Medicago sativa L.) cv K-22 with advancing maturity was investigated. Sampling was done in 7-day intervals in second cut. During growth and development, crude protein content decreased in leaves and stems, from 332,6 to 328,8 gkg-1DM and from 138,6 to 122,0 gkg-1DM, respectively. From first to

  13. Mycosphaerellaceae and Teratosphaeriaceae associated with Eucalyptus leaf diseases and stem cankers in Uruguay

    E-print Network

    Blanchette, Robert A.

    in Uruguay By C. A. Pe´rez1,2,5 , M. J. Wingfield3 , N. A. Altier4 and R. A. Blanchette1 1 Department´, Uruguay; 3 Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, Uruguay; 5 E-mail: caperez@fagro.edu.uy (for correspondence) Summary Mycosphaerella leaf diseases

  14. Changes in leaf hydraulic conductance correlate with leaf vein embolism in Cercis siliquastrum L

    Microsoft Academic Search

    Andrea Nardini; Sebastiano Salleo; Fabio Raimondo

    2003-01-01

    The impact of xylem cavitation and embolism on leaf ( K leaf) and stem ( K stem) hydraulic conductance was measured in current-year shoots of Cercis siliquastrum L. (Judas tree) using the vacuum chamber technique. K stem decreased at leaf water potentials (? L) lower than -1.0 MPa, while K leaf started to decrease only at ? L L K leaf

  15. Development of Leaf Spectral Models for Evaluating Large Numbers of Sugarcane Genotypes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leaf reflectance has been used to estimate crop leaf chemical and physiological characters. Sugarcane (Saccharum spp.) leaf N, C, and chlorophyll levels are important traits for high yields and perhaps useful for genotype evaluation. The objectives of this study were to identify sugarcane genotypic ...

  16. Asymmetric leaves1 mediates leaf patterning and stem cell function in Arabidopsis

    Microsoft Academic Search

    Mary E. Byrne; Ross Barley; Mark Curtis; Juana Maria Arroyo; Maitreya Dunham; Andrew Hudson; Robert A. Martienssen

    2000-01-01

    Meristem function in plants requires both the maintenance of stem cells and the specification of founder cells from which lateral organs arise. Lateral organs are patterned along proximodistal, dorsoventral and mediolateral axes. Here we show that the Arabidopsis mutant asymmetric leaves1 (as1) disrupts this process. AS1 encodes a myb domain protein, closely related to PHANTASTICA in Antirrhinum and ROUGH SHEATH2

  17. Alfalfa leaf protein and stem cell wall polysaccharide yields under hay and biomass management systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alfalfa (Medicago sativa L.) has been proposed as a biofuel feedstock in which the stems would be processed to produce ethanol and the leaves sold separately as a livestock feed. We propose a modified management regime with reduced population density and delayed, less frequent harvests be implemente...

  18. Net photosynthesis, dark respiration, specific leaf weight, and growth of young apple trees as influenced by light regime

    Microsoft Academic Search

    Barden

    1974-01-01

    Eight different light treatments did not affect shoot length, leaf number, or total leaf area of young Red Yorking apple (Malus pumila Mill.) trees grown in a greenhouse. Dry weights of leaves and stems were suppressed by 80% shade. Net photosynthesis Pn, dark respiration (Rd), and specific leaf weight (SLW) were higher in sun than in shade leaves and adaptations

  19. Striking similarities between the nucleotide sequence and genome organization of citrus tatter leaf and apple stem grooving capilloviruses.

    PubMed

    Yoshikawa, N; Imaizumi, M; Takahashi, T; Inouye, N

    1993-12-01

    The sequence of the 3'-terminal 2956 nucleotides, excluding the poly(A) tail, of the citrus tatter leaf virus (CTLV) genome was determined and compared with that of the apple stem grooving virus (ASGV) genome. The sequence of the 3'-terminal region of CTLV contains two overlapping open reading frames (ORFs) and a 3'-terminal non-coding region of 142 nucleotides. The long, incomplete ORF1 ends at UAG (position 2812) and encodes a protein with at least 938 amino acids (M(r) > 108,703). This protein contains the GDD motif associated with the RNA polymerase. ORF2, in a different frame within ORF1, starts at AUG (position 1248) and stops at UGA (position 2208) encoding a protein with an M(r) of 36,179 (36K). Partial homologies were found among the 36K protein of CTLV, the 50K protein of apple chlorotic leaf spot closterovirus, the 40K protein of potato virus T and the gene 1 products of caulimoviruses. The arrangement of ORFs in the 3'-terminal region of the CTLV genome is in perfect agreement with that of the ASGV genome. The sequence of the 3'-terminal 2956 nucleotides, excluding the poly(A) tail, of the CTLV genome shows 86.1% identity to that of the ASGV genome. Similarities of amino acid sequences encoded by ORF1 and ORF2 of CTLV with the corresponding regions of ASGV are 86.1% and 97.3%, respectively. These results indicate that CTLV is a capillovirus closely related to ASGV. PMID:8277280

  20. A multiple resistance locus on chromosome arm 3BS in wheat confers resistance to stem rust ( Sr2 ), leaf rust ( Lr27 ) and powdery mildew

    Microsoft Academic Search

    R. MagoL; L. Tabe; R. A. McIntosh; Z. Pretorius; R. Kota; E. Paux; T. Wicker; J. Breen; E. S. Lagudah; J. G. Ellis; W. Spielmeyer

    Sr2 is the only known durable, race non-specific adult plant stem rust resistance gene in wheat. The Sr2 gene was shown to be tightly linked to the leaf rust resistance gene Lr27 and to powdery mildew resistance. An analysis of recombinants and mutants suggests that a single gene on chromosome arm 3BS\\u000a may be responsible for resistance to these three

  1. GENETIC CONTROL OF THE NUMBER OF NODES PER STEM IN MILLET (Panicum miliaceum L.)

    Microsoft Academic Search

    Mihai Pricop

    The number of nodes per stem in millet has a special contribution to plant growth and development, being directly, positively and significantly correlated with the number of leaves and panicles per plant, TKW, green mass, grain and protein yield. The researches performed at Agricultural Research and Development Station Podu- Iloaiei pointed out an average variability for this trait. Hybridological analyses

  2. Piper nigrum Leaf and Stem Assisted Green Synthesis of Silver Nanoparticles and Evaluation of Its Antibacterial Activity Against Agricultural Plant Pathogens

    PubMed Central

    Paulkumar, Kanniah; Gnanajobitha, Gnanadhas; Vanaja, Mahendran; Rajeshkumar, Shanmugam; Malarkodi, Chelladurai; Pandian, Kannaiyan; Annadurai, Gurusamy

    2014-01-01

    Utilization of biological materials in synthesis of nanoparticles is one of the hottest topics in modern nanoscience and nanotechnology. In the present investigation, the silver nanoparticles were synthesized by using the leaf and stem extract of Piper nigrum. The synthesized nanoparticle was characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and Fourier Transform Infrared Spectroscopy (FTIR). The observation of the peak at 460?nm in the UV-vis spectra for leaf- and stem-synthesized silver nanoparticles reveals the reduction of silver metal ions into silver nanoparticles. Further, XRD analysis has been carried out to confirm the crystalline nature of the synthesized silver nanoparticles. The TEM images show that the leaf- and stem-synthesized silver nanoparticles were within the size of about 7–50?nm and 9–30?nm, respectively. The FTIR analysis was performed to identify the possible functional groups involved in the synthesis of silver nanoparticles. Further, the antibacterial activity of the green-synthesized silver nanoparticles was examined against agricultural plant pathogens. The antibacterial property of silver nanoparticles is a beneficial application in the field of agricultural nanotechnology. PMID:24558336

  3. Grain Amaranths Are Defoliation Tolerant Crop Species Capable of Utilizing Stem and Root Carbohydrate Reserves to Sustain Vegetative and Reproductive Growth after Leaf Loss

    PubMed Central

    Vargas-Ortiz, Erandi; Espitia-Rangel, Eduardo; Tiessen, Axel; Délano-Frier, John Paul

    2013-01-01

    Tolerance to defoliation can be defined as the degree to which productivity is affected by photosynthetic area reduction. This trait was studied in grain amaranth (Amaranthus cruentus and A. hypochondriacus), which are considered to be a highly defoliation-tolerant species. The physiological and biochemical responses to increasing levels of mechanical leaf removal up to total defoliation were quantified. Tolerance appeared to be dependent on various factors: ( i) amount of lost tissue; (ii) mechanics of leaf tissue removal; (iii) environment, and (iv) species tested. Thus, grain amaranth was found to be a highly tolerant species under green-house conditions when leaf tissue loss was performed by gradual perforation. However, tolerance was compromised under similar conditions when defoliation was done by gradual cutting of the leaf. Also tolerance in completely defoliated plants tended to decrease under field conditions, where differences between A. cruentus and A. hypochondriacus were observed. All non-structural carbohydrate (NSC) levels were reduced in stems and roots of totally defoliated amaranths one day after treatment. Such depletion probably provided the carbon (C) resources needed to sustain the early recovery process in the absence of photosynthetic capacity. This was corroborated by shading of intact plants, which produced the same rapid and drastic reduction of NSC levels in these tissues. These results emphasize the role of stored NSCs, particularly starch, in buffering the impact of severe defoliation in amaranth. The fall in sucrose synthase and cell wall invertase activity observed in stems and roots soon after defoliation was consistent with their predicted shift from sink to source tissues. It is concluded that mobilization of C stores in stems and roots, is a physiologically important trait underlying tolerance to defoliation in grain amaranth. PMID:23861825

  4. Is a Gall an Extended Phenotype of the Inducing Insect? A Comparative Study of Selected Morphological and Physiological Traits of Leaf and Stem Galls on Machilus thunbergii (Lauraceae) Induced by Five Species of Daphnephila (Diptera: Cecidomyiidae) in Northeastern Taiwan.

    PubMed

    Pan, Liang-Yu; Chen, Wen-Neng; Chiu, Shau-Ting; Raman, Anantanarayanan; Chiang, Tung-Chuang; Yang, Man-Miao

    2015-06-01

    Mature galls induced by Daphnephila truncicola, D. taiwanensis, D. sueyenae, D. stenocalia, and D. ornithocephala on Machilus thunbergii in northern Taiwan were examined to verify the dictum that the morphology of galls is an expression of the extended phenotype of the respective gall-inducing insect. Based on their length-width ratio, the materials were grouped into either fleshy (those induced by D. taiwanensis and D. sueyenae) or slim galls (those induced by D. truncicola, D. stenocalia, and D. ornithocephala). Stem galls induced by D. truncicola showed an energy level of 0.0178 kJ/g. Among leaf galls, the greatest energy level was in the one induced by D. stenocalia (0.0193 kJ/g), followed by D. sueyenae (0.0192 kJ/g), D. taiwanensis (0.0189 kJ/g), and D. ornithocephala (0.0160 kJ/g). The numbers of reserve and nutritive cell layers in galls were greater in the stem galls induced by D. truncicola, similar to those in the fleshy leaf galls, than in the slim leaf galls. Based on the fungal taxa isolated from the larval chambers and considering the similarities and divergences among gall characteristics, the galls induced by D. truncicola and D. taiwanensis clustered into one, whereas those of D. sueyenae aligned with the 'D. stenocalia-D. ornithocephala' cluster. The present study verified that shapes, structure, nutritive tissues, energy levels, and multiple coexisting fungal taxa within galls reinforce that they are extended phenotypes of the respective gall-inducing Daphnephila species and they represent adaptive evolution of Daphnephila on M. thunbergii. PMID:26003988

  5. Olea europaea leaf extract improves the treatment response of GBM stem cells by modulating miRNA expression

    PubMed Central

    Tezcan, Gulcin; Tunca, Berrin; Bekar, Ahmet; Budak, Ferah; Sahin, Saliha; Cecener, Gulsah; Egeli, Unal; Taskap?l?oglu, Mevlut Ozgur; Kocaeli, Hasan; Tolunay, Sahsine; Malyer, Hulusi; Demir, Cevdet; Tumen, Gulendam

    2014-01-01

    The stem-like cells of Glioblastoma multiforme (GBM) tumors (GSCs) are one of the important determinants of recurrence and drug resistance. The aims of the current study were to evaluate the anticancer effect of Olea europaea leaf extract (OLE) on GBM cell lines, the association between OLE and TMZ responses, and the effect of OLE and the OLE-TMZ combination in GSCs and to clarify the molecular mechanism of this effect on the expression of miRNAs related to cell death. The anti-proliferative activity of OLE and the effect of the OLE-TMZ combination were tested in the T98G, U-138MG and U-87MG GBM cell lines using WST-1 assay. The mechanism of cell death was analyzed with Annexin V/FITC and TUNEL assays. The effects of OLE on the expression levels of miR-181b, miR-153, miR-145 and miR-137 and potential mRNA targets were analyzed in GSCs using RT-qPCR. OLE exhibited anti-proliferative effects via apoptosis and necrosis in the GBM cell lines. In addition, OLE significantly induced the expression of miR-153, miR-145, and miR-137 and decreased the expression of the target genes of these miRNAs in GSCs (p < 0.05). OLE causes cell death in GBM cells with different TMZ responses, and this effect is synergistically increased when the cells are treated with a combination of OLE and TMZ. This is the first study to indicate that OLE may interfere with the pluripotency of GSCs by modulating miRNA expression. Further studies are required, but we suggest that OLE may have a potential for advanced therapeutic cancer drug studies in GBM. PMID:25232498

  6. STORM: A General Model to Determine the Number and Adaptive Changes of Epithelial Stem Cells in Teleost, Murine and Human Intestinal Tracts

    E-print Network

    Wang, Zhengyuan

    Intestinal stem cells play a pivotal role in the epithelial tissue renewal, homeostasis and cancer development. The lack of a general marker for intestinal stem cells across species has hampered analysis of stem cell number ...

  7. Microclimatic conditions determined by stem density influence leaf anatomy and leaf physiology of beech ( Fagus sylvatica L.) growing within stands that naturally regenerate from clear-cutting

    Microsoft Academic Search

    Iván Closa; Juan José Irigoyen; Nieves Goicoechea

    2010-01-01

    Beech forests naturally regenerating from clear-cutting can exhibit different microclimates depending on size of saplings\\u000a and stem density. When beech trees are young and stem density is low, the level of radiation inside the ecosystem reaching\\u000a the soil surface is high; consequently, air and soil temperatures rise and the soil water content may decrease. These microclimatic\\u000a parameters presumably will affect

  8. Reduction of stem growth and site dependency of leaf injury in Massachusetts black cherries exhibiting ozone symptoms

    Microsoft Academic Search

    P. Vollenweider; H. Woodcock; M. J. Kelty; R.-M. Hofer

    2003-01-01

    Leaf ozone symptoms in natural ecosystems are increasingly reported but ozone effects on tree growth and the mediation of site conditions are still little documented. This study tests two hypotheses: (1) leaf injury in black cherry is associated with decline in radial growth, (2) symptoms are more prevalent on mesic sites. On sites supporting black cherry across Massachusetts, tree growth

  9. Plant regeneration in Actinidia polygama Miq. by leaf, stem, and petiole culture with zeatin, and from stem-derived calli on low-sucrose medium

    Microsoft Academic Search

    Wataru Takahashi; Fuyuki Sugawara; Noriko Yamamoto; Eriko Bando; Junjo Matsushita; Osamu Tanaka

    2004-01-01

    We examined the effect of zeatin on the formation of shoot buds from explants and callus tissues derived from stem segments of Actinidia polygama Miq. ( matatabi or silver vine). Stem and petiole segments cultured on combined broad-leaved tree medium and woody plant medium (BW medium) supplemented with zeatin for 40 days formed many shoot buds. Callus tissues derived from

  10. The influence of physiological age, stem numbers and fertility on yield and grade of Russet Burbank potatoes

    Microsoft Academic Search

    W. M. Iritani; D. L. Weller

    1987-01-01

    The present study was initiated to determine if increased stem numbers produced by physiologically older seed can be compensated\\u000a for by increased fertilizer rate. Seed tubers held for 2 months at 16 C (physiological older seed) which averaged 3.7 main\\u000a stems were compared in yield parameters to physiologically younger seed kept at 4 C (average 2.4 stems). The comparison was

  11. GC/MS analysis of volatiles obtained by headspace solid-phase microextraction and simultaneous-distillation extraction from Rabdosia serra (MAXIM.) HARA leaf and stem.

    PubMed

    Lin, Lianzhu; Zhuang, Mingzhu; Lei, Fenfen; Yang, Bao; Zhao, Mouming

    2013-01-15

    Volatiles in Rabdosia serra were investigated by headspace solid phase microextraction (HS-SPME) and simultaneous-distillation extraction (SDE). The HS-SPME technique was previously evaluated to optimise sampling conditions. A total of 56 and 48 compounds including alcohols, aldehydes, hydrocarbons, ketones, carboxylic acid, ester, and aromatics were identified in leaf and stem by optimised HS-SPME method (CAR/PDMS fibre; incubation time, 10 min; extraction temperature, 50°C; extraction time, 40 min), respectively. 1-Octen-3-ol and (2E)-hexenal had significant contribution to R. serra aroma. Cluster analysis indicated that leaf and stem exhibited different volatile diversity. Air drying was favourable for the retention of the volatiles, while freeze- and sun-drying led to the loss of volatiles. SDE method preferred to the analysis of compounds with low volatility including fatty acids and esters. HS-SPME was a useful technique for the analysis of readily volatile components for the characteristics of R. serra aroma. PMID:23122097

  12. CO[sub 2] and temperature effects on leaf area production in two annual plant species

    SciTech Connect

    Ackerly, D.D.; Coleman, J.S.; Morse, S.R.; Bazzaz, F.A. (Harvard University, Cambridge, MA (United States))

    1992-08-01

    The authors studied leaf area production in two annual plant species, Abutilon theophrasti and Amaranthus retroflexus, under three day/night temperature regimes and two concentrations of carbon dioxide. The production of whole-plant leaf area during the first 30 d of growth was analyzed in terms of the leaf initiation rate, leaf expansion, individual leaf area, and, in Amaranthus, production of branch leaves. Temperature and CO[sub 2] influenced leaf area production through effects on the rate of development, determined by the production of nodes on the main stem, and through shifts in the relationship between whole-plant leaf area and the number of main stem nodes. In Abutilon, leaf initiation rate was highest at 38[degree], but area of individual leaves was greatest at 28[degree]. Total leaf area was greatly reduced at 18[degree] due to slow leaf initiation rates. Elevated CO[sub 2] concentration increased leaf initiation rate at 28[degree], resulting in an increase in whole-part leaf area. In Amaranthus, leaf initiation rate increased with temperature, and was increased by elevated CO[sub 2] at 28[degree]. Individual leaf area was greatest at 28[degree], and was increased by elevated CO[sub 2] at 28[degree] but decreased at 38[degree]. Branch leaf area displayed a similar response to CO[sub 2], butt was greater at 38[degree]. Overall, wholeplant leaf area was slightly increased at 38[degree] relative to 28[degree], and elevated CO[sub 2] levels resulted in increased leaf area at 28[degree] but decreased leaf area at 38[degree].

  13. Stems

    NSDL National Science Digital Library

    Olivia Worland (Purdue University; Biological Sciences)

    2008-06-03

    Some mature plants can produce new plants by cutting a piece of stem off of the original plant. Most members of the mint family and ivy family can do this readily. The new plant will grow its own root system.

  14. Simulating nectarine tree transpiration and dynamic water storage from responses of leaf conductance to light and sap flow to stem water potential and vapor pressure deficit.

    PubMed

    Paudel, Indira; Naor, Amos; Gal, Yoni; Cohen, Shabtai

    2015-04-01

    For isohydric trees mid-day water uptake is stable and depends on soil water status, reflected in pre-dawn leaf water potential (?pd) and mid-day stem water potential (?md), tree hydraulic conductance and a more-or-less constant leaf water potential (?l) for much of the day, maintained by the stomata. Stabilization of ?l can be represented by a linear relationship between canopy resistance (Rc) and vapor pressure deficit (D), and the slope (BD) is proportional to the steady-state water uptake. By analyzing sap flow (SF), meteorological and ?md measurements during a series of wetting and drying (D/W) cycles in a nectarine orchard, we found that for the range of ?md relevant for irrigated orchards the slope of the relationship of Rc to D, BD is a linear function of ?md. Rc was simulated using the above relationships, and its changes in the morning and evening were simulated using a rectangular hyperbolic relationship between leaf conductance and photosynthetic irradiance, fitted to leaf-level measurements. The latter was integrated with one-leaf, two-leaf and integrative radiation models, and the latter gave the best results. Simulated Rc was used in the Penman-Monteith equation to simulate tree transpiration, which was validated by comparing with SF from a separate data set. The model gave accurate estimates of diurnal and daily total tree transpiration for the range of ?mds used in regular and deficit irrigation. Diurnal changes in tree water content were determined from the difference between simulated transpiration and measured SF. Changes in water content caused a time lag of 90-105?min between transpiration and SF for ?md between -0.8 and -1.55?MPa, and water depletion reached 3?l?h(-1) before noon. Estimated mean diurnal changes in water content were 5.5?l?day(-1)?tree(-1) at ?md of -0.9?MPa and increased to 12.5?l?day(-1)?tree(-1) at -1.45?MPa, equivalent to 6.5 and 16.5% of daily tree water use, respectively. Sixteen percent of the dynamic water volume was in the leaves. Inversion of the model shows that ?md can be predicted from D and Rc, which may have some importance for irrigation management to maintain target values of ?md. That relationship will be explored in future research. PMID:25618897

  15. Leaf-wax n-alkanes record the plantwater environment at leaf ush

    E-print Network

    Tipple, Brett

    Leaf-wax n-alkanes record the plant­water environment at leaf ush Brett J. Tipple1 , Melissa A, UT, and approved December 26, 2012 (received for review August 13, 2012) Leaf-wax n-alkanes 2 H/1 H the 2 H values of leaf-wax n-alkanes and of stem, leaf, stream, and atmospheric waters throughout

  16. SD of maximum Stem Diameter (in cm)

    E-print Network

    Schierup, Mikkel Heide

    SD of maximum Stem Diameter (in cm) 1,4 - 13,3 13,4 - 14,8 14,9 - 15,6 15,7 - 16,5 16,6 - 17,3 17,8 12,9 - 14,3 14,4 - 16,1 16,2 - 30,0 Mean of maximum Stem Diameter (in cm) 0,0 - 13,3 13,4 - 14,5 14 look quite similar. Mean of Stem Height, Stem Diameter and Leaf Number seem to show higher values

  17. Original article Photosynthesis, leaf area and productivity

    E-print Network

    Paris-Sud XI, Université de

    Original article Photosynthesis, leaf area and productivity of 5 poplar clones during; The stem volume and biomass (stem + branches) production, net photosynthesis of mature leaves and leaf area found in volume production, woody biomass production, total leaf area and net photosynthesis. Above

  18. Identification and correction of spectral contamination in 2H/1H and 18O/16O measured in leaf, stem, and soil water.

    PubMed

    Schultz, Natalie M; Griffis, Timothy J; Lee, Xuhui; Baker, John M

    2011-11-15

    Plant water extracts typically contain organic materials that may cause spectral interference when using isotope ratio infrared spectroscopy (IRIS), resulting in errors in the measured isotope ratios. Manufacturers of IRIS instruments have developed post-processing software to identify the degree of contamination in water samples, and potentially correct the isotope ratios of water with known contaminants. Here, the correction method proposed by an IRIS manufacturer, Los Gatos Research, Inc., was employed and the results were compared with those obtained from isotope ratio mass spectrometry (IRMS). Deionized water was spiked with methanol and ethanol to create correction curves for ?(18)O and ?(2)H. The contamination effects of different sample types (leaf, stem, soil) and different species from agricultural fields, grasslands, and forests were compared. The average corrections in leaf samples ranged from 0.35 to 15.73‰ for ?(2)H and 0.28 to 9.27‰ for ?(18)O. The average corrections in stem samples ranged from 1.17 to 13.70‰ for ?(2)H and 0.47 to 7.97‰ for ?(18)O. There was no contamination observed in soil water. Cleaning plant samples with activated charcoal had minimal effects on the degree of spectral contamination, reducing the corrections, by on average, 0.44‰ for ?(2)H and 0.25‰ for ?(18)O. The correction method eliminated the discrepancies between IRMS and IRIS for ?(18)O, and greatly reduced the discrepancies for ?(2)H. The mean differences in isotope ratios between IRMS and the corrected IRIS method were 0.18‰ for ?(18)O, and -3.39‰ for ?(2)H. The inability to create an ethanol correction curve for ?(2)H probably caused the larger discrepancies. We conclude that ethanol and methanol are the primary compounds causing interference in IRIS analyzers, and that each individual analyzer will probably require customized correction curves. PMID:22006400

  19. Lsd1 restricts the number of germline stem cells by regulating multiple targets in escort cells.

    PubMed

    Eliazer, Susan; Palacios, Victor; Wang, Zhaohui; Kollipara, Rahul K; Kittler, Ralf; Buszczak, Michael

    2014-03-01

    Specialized microenvironments called niches regulate tissue homeostasis by controlling the balance between stem cell self-renewal and the differentiation of stem cell daughters. However the mechanisms that govern the formation, size and signaling of in vivo niches remain poorly understood. Loss of the highly conserved histone demethylase Lsd1 in Drosophila escort cells results in increased BMP signaling outside the cap cell niche and an expanded germline stem cell (GSC) phenotype. Here we present evidence that loss of Lsd1 also results in gradual changes in escort cell morphology and their eventual death. To better characterize the function of Lsd1 in different cell populations within the ovary, we performed Chromatin immunoprecipitation coupled with massive parallel sequencing (ChIP-seq). This analysis shows that Lsd1 associates with a surprisingly limited number of sites in escort cells and fewer, and often, different sites in cap cells. These findings indicate that Lsd1 exhibits highly selective binding that depends greatly on specific cellular contexts. Lsd1 does not directly target the dpp locus in escort cells. Instead, Lsd1 regulates engrailed expression and disruption of engrailed and its putative downstream target hedgehog suppress the Lsd1 mutant phenotype. Interestingly, over-expression of engrailed, but not hedgehog, results in an expansion of GSC cells, marked by the expansion of BMP signaling. Knockdown of other potential direct Lsd1 target genes, not obviously linked to BMP signaling, also partially suppresses the Lsd1 mutant phenotype. These results suggest that Lsd1 restricts the number of GSC-like cells by regulating a diverse group of genes and provide further evidence that escort cell function must be carefully controlled during development and adulthood to ensure proper germline differentiation. PMID:24625679

  20. Nucleotide sequences of a Korean isolate of apple stem grooving virus associated with black necrotic leaf spot disease on pear (Pyrus pyrifolia).

    PubMed

    Shim, Hyekyung; Min, Yeonju; Hong, Sungyoul; Kwon, Moonsik; Kim, Daehyun; Kim, Hyunran; Choi, Yongmoon; Lee, Sukchan; Yang, Jaemyung

    2004-10-31

    Pear black necrotic leaf spot (PBNLS) is a disease of pears caused by capillovirus-like particles, which can be observed under the electron microscope. The disease was analyzed by Western blot analysis with antisera raised against apple stem grooving virus (ASGV) coat protein. cDNAs covering the entire genome were synthesized by RT-PCR and RACE using RNA isolated from Chenopodium quinoa infected with sap extracted from pear leaves carrying black necrotic spot disease. The complete genome sequence of the putative pear virus, 6497 nucleotides in length excluding the poly (A) tail, was determined and analyzed. It contains two overlapping open reading frames (ORFs). ORF1, spans from nucleotide position 37 to 6354, producing a putative protein of 241 kDa. ORF2, which is in a different reading frame within ORF1, begins at nucleotide 4788 and terminates at 5750, and produces a putative protein of 36 kDa. The 241 kDa protein contains sequences related to the NTP-binding motifs of helicases and RNA-dependent RNA polymerases. The 36-kDa protein contains the consensus sequence GDSG found in the active sites of several cellular and viral serine proteases. Morphological and serological analysis, and sequence comparison between the putative pear virus, ASGV, citrus tatter leaf virus and cherry virus A of the capillovirus suggest that PBNLS may be caused by a Korean isolate of ASGV. PMID:15528995

  1. Are lianas more drought-tolerant than trees? A test for the role of hydraulic architecture and other stem and leaf traits.

    PubMed

    van der Sande, Masha T; Poorter, Lourens; Schnitzer, Stefan A; Markesteijn, Lars

    2013-08-01

    Lianas are an important component of neotropical forests, where evidence suggests that they are increasing in abundance and biomass. Lianas are especially abundant in seasonally dry tropical forests, and as such it has been hypothesized that they are better adapted to drought, or that they are at an advantage under the higher light conditions in these forests. However, the physiological and morphological characteristics that allow lianas to capitalize more on seasonal forest conditions compared to trees are poorly understood. Here, we evaluate how saplings of 21 tree and liana species from a seasonal tropical forest in Panama differ in cavitation resistance (P50) and maximum hydraulic conductivity (K(h)), and how saplings of 24 tree and liana species differ in four photosynthetic leaf traits (e.g., maximum assimilation and stomatal conductance) and six morphological leaf and stem traits (e.g., wood density, maximum vessel length, and specific leaf area). At the sapling stage, lianas had a lower cavitation resistance than trees, implying lower drought tolerance, and they tended to have a higher potential hydraulic conductivity. In contrast to studies focusing on adult trees and lianas, we found no clear differences in morphological and photosynthetic traits between the life forms. Possibly, lianas and trees are functionally different at later ontogenetic stages, with lianas having deeper root systems than trees, or experience their main growth advantage during wet periods, when they are less vulnerable to cavitation and can achieve high conductivity. This study shows, however, that the hydraulic characteristics and functional traits that we examined do not explain differences in liana and tree distributions in seasonal forests. PMID:23277211

  2. Clonal propagation of Stevia rebaudiana Bertoni by stem-tip culture

    Microsoft Academic Search

    Yukiyoshi Tamura; Shigeharu Nakamura; Hiroshi Fukui; Mamoru Tabata

    1984-01-01

    Clonal propagation of Stevia rebaudiana has been established by culturing stem-tips with a few leaf primordia on an agar medium supplemented with a high concentration (10 mg\\/l) of kinetin. Anatomical examination has suggested that these multiple shoots originate from a number of adventitious buds formed on the margin of the leaf. Innumerable shoots can be obtained by repeating the cycle

  3. Genetic Basis for Developmental Homeostasis of Germline Stem Cell Niche Number: A Network of Tramtrack-Group Nuclear BTB Factors

    PubMed Central

    Chalvet, Fabienne; Netter, Sophie; Dos Santos, Nicolas; Poisot, Emilie; Paces-Fessy, Mélanie; Cumenal, Delphine; Peronnet, Frédérique; Pret, Anne-Marie; Théodore, Laurent

    2012-01-01

    The potential to produce new cells during adult life depends on the number of stem cell niches and the capacity of stem cells to divide, and is therefore under the control of programs ensuring developmental homeostasis. However, it remains generally unknown how the number of stem cell niches is controlled. In the insect ovary, each germline stem cell (GSC) niche is embedded in a functional unit called an ovariole. The number of ovarioles, and thus the number of GSC niches, varies widely among species. In Drosophila, morphogenesis of ovarioles starts in larvae with the formation of terminal filaments (TFs), each made of 8–10 cells that pile up and sort in stacks. TFs constitute organizers of individual germline stem cell niches during larval and early pupal development. In the Drosophila melanogaster subgroup, the number of ovarioles varies interspecifically from 8 to 20. Here we show that pipsqueak, Trithorax-like, batman and the bric-à-brac (bab) locus, all encoding nuclear BTB/POZ factors of the Tramtrack Group, are involved in limiting the number of ovarioles in D. melanogaster. At least two different processes are differentially perturbed by reducing the function of these genes. We found that when the bab dose is reduced, sorting of TF cells into TFs was affected such that each TF contains fewer cells and more TFs are formed. In contrast, psq mutants exhibited a greater number of TF cells per ovary, with a normal number of cells per TF, thereby leading to formation of more TFs per ovary than in the wild type. Our results indicate that two parallel genetic pathways under the control of a network of nuclear BTB factors are combined in order to negatively control the number of germline stem cell niches. PMID:23185495

  4. Osmotic adjustment and the inhibition of leaf, root, stem and silk growth at low water potentials in maize

    Microsoft Academic Search

    M. E. Westgate I; J. S. Boyer

    1985-01-01

    The expansion growth of plant organs is inhibited at low water potentials (?w), but the inhibition has not been compared in different organs of the same plant. Therefore, we determined elongation rates of the roots, stems, leaves, and styles (silks) of maize (Zea mays L.) as soil water was depleted. The ?w was measured in the region of cell expansion

  5. Alfalfa leaf protein and stem cell wall polysaccharide yields and theoretical ethanol production under hay and biomass management systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alfalfa (Medicago sativa L.) has been proposed as a biofuel feedstock, where the stems would be processed to produce ethanol and the leaves sold separately as a livestock feed. We propose a different management regime reducing population density, delaying harvest and cutting less frequently per grow...

  6. ALFALFA LEAF PROTEIN AND STEM CELL WALL POLYSACCHARIDE YIELDS AND THEORETICAL ETHANOL PRODUCTION UNDER HAY AND BIOMASS MANAGEMENT SYSTEMS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alfalfa (Medicago sativa L.) has been proposed as a biofuel feedstock, where the stems would be processed to produce ethanol and the leaves sold separately as a livestock feed. We propose a different management regime reducing population density, delaying harvest, and cutting less frequently per gro...

  7. Myrothecium roridum leaf spot and stem canker on watermelon in the southern Great Plains: Possible factors for its outbreak

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diseases are generally the greatest yield-limiting factor for watermelon across the U.S. In 2010, a foliar and stem-lesion disease was observed for the first time in Oklahoma causing moderate to severe defoliation. Using microscopic examination, the physical features of the fungus were consistent ...

  8. 7 CFR 30.4 - Stemmed.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.4 Stemmed. A form of leaf tobacco consisting of a collection of leaves from which the stems or midribs have been...

  9. 7 CFR 30.4 - Stemmed.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.4 Stemmed. A form of leaf tobacco consisting of a collection of leaves from which the stems or midribs have been...

  10. 7 CFR 30.4 - Stemmed.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.4 Stemmed. A form of leaf tobacco consisting of a collection of leaves from which the stems or midribs have been...

  11. Stem Morphology and Anatomy in Amaranthus L. (Amaranthaceae)—Taxonomic Significance

    Microsoft Academic Search

    Mihai Costea; Darleen A. DeMason

    2001-01-01

    The range of variation within the genus Amaranthus L. (Amaranthaceae) is described for a number of stem characters including: morphology, epidermis, primary stem vasculature and mechanism of secondary growth. The results provide new characters (phyllotaxy, complexity of leaf vascular supply and relative amount of secondary growth) that support (1) a new infrageneric classification (subgenus Amaranthus vs subgenus Albersia (Kunth)Gren. &

  12. Evidence of hydraulic lift for pre-rainy season leaf out and dry-season stem water enrichment in Sclerocarya birrea, a tropical agroforestry tree

    NASA Astrophysics Data System (ADS)

    Ceperley, Natalie; Mande, Theophile; Rinaldo, Andrea; Parlange, Marc B.

    2014-05-01

    We use stable isotopes of water as tracers to follow water use by five Sclerocarya birrea trees in a catchment in South Eastern Burkina Faso interspersed with millet fields, gallery forest, Sudanian savanna, and fallow fields. Isotopic ratios were determined from water extracted from stems of the trees and sub-canopy soil of two of them, while nearby ground water, precipitation, and surface water was sampled weekly. A unique configuration of sensors connected with a wireless sensor network of meteorological stations measured sub-canopy shading, the temperature and humidity in the canopy, through-fall, and soil moisture under two of the trees. Both water extracted from sap and water extracted from soil is extremely enriched in the dry season, but drop to levels close to the ground water in February or March, which coincides with the growth of leaves. Dates of leaf out were confirmed by changes in ?DH and ?O18 concentrations of water, photographic documentation & pixel analysis, and analysis of sub-canopy radiation and proceeded the rise in humidity and flow that was later detected in the sub-canopy soil, the trunk of the tree (sap-flow), and atmosphere (canopy VPD). Examination of the isotopic signature suggests that size of tree plays an important role in duration and timing of this leaf-out as well as the degree of enrichment during the peak of the dry season. Further examination of the isotopic signatures of the roots suggested that the trees are performing hydraulic redistribution, or lifting the ground water and "sharing it" with the soil in the rooting zone in the dry season. The enriched level of xylem in this case is a product of water loss, and enrichment, along the travel path of the water from the roots to the tip of the stem, as evidenced by the variation according to size of tree. Vapor pressure deficit, soil water, and soil moisture interactions support this picture of interacting controls, separate from hydrologic triggers on the water movement in the tree.

  13. Stem, root, and older leaf N:P ratios are more responsive indicators of soil nutrient availability than new foliage.

    PubMed

    Schreeg, L A; Santiago, L S; Wright, S J; Turner, B L

    2014-08-01

    Foliar nitrogen to phosphorus (N:P) ratios are widely used to indicate soil nutrient availability and limitation, but the foliar ratios of woody plants have proven more complicated to interpret than ratios from whole biomass of herbaceous species. This may be related to tissues in woody species acting as nutrient reservoirs during active growth, allowing maintenance of optimal N:P ratios in recently produced, fully expanded leaves (i.e., "new" leaves, the most commonly sampled tissue). Here we address the hypothesis that N:P ratios of newly expanded leaves are less sensitive indicators of soil nutrient availability than are other tissue types in woody plants. Seedlings of five naturally established tree species were harvested from plots receiving two years of fertilizer treatments in a lowland tropical forest in the Republic of Panama. Nutrient concentrations were determined in new leaves, old leaves, stems, and roots. For stems and roots, N:P ratios increased after N addition and decreased after P addition, and trends were consistent across all five species. Older leaves also showed strong responses to N and P addition, and trends were consistent for four of five species. In comparison, overall N:P ratio responses in new leaves were more variable across species. These results indicate that the N:P ratios of stems, roots, and older leaves are more responsive indicators of soil nutrient availability than are those of new leaves. Testing the generality of this result could improve the use of tissue nutrient ratios as indices of soil nutrient availability in woody plants. PMID:25230458

  14. Effect of Urtica dioica Leaf Alcoholic and Aqueous Extracts on the Number and the Diameter of the Islets in Diabetic Rats.

    PubMed

    Qujeq, Durdi; Tatar, Mohsen; Feizi, Farideh; Parsian, Hadi; Sohan Faraji, Alieh; Halalkhor, Sohrab

    2013-01-01

    Urtica dioica has been known as a plant that decreases blood glucose. Despite the importance of this plant in herbal medicine, relatively little research has been down on effects of this plant on islets yet. The objective of the current study was to evaluate the effect of dried Urtica dioica leaf alcoholic and aqueous extracts on the number and the diameter of the islets and histological parameters in streptozocin-induced diabetic rats. Six rats were used in each group. Group I: Normal rats were administered saline daily for 8 weeks. Group II: Diabetic rats were administered streptozotocin, 50 mg/kg of body weight; Group III: Diabetic rats were administered dried Urtica dioica leaf aqueous extracts for 8 weeks; Group IV: Diabetic rats were administered dried Urtica dioica leaf alcoholic extracts for 8 weeks. The animals, groups of diabetic and normal, were sacrificed by ether anaesthesia. Whole pancreas was dissected. The tissue samples were formalin fixed and paraffin embedded for microscopic examination. Histologic examination and grading were carried out on hematoxylin-eosin stained sections. The effects of administration of dried Urtica dioica leaf alcoholic and aqueous extracts to diabetic rats were determined by histopathologic examination. The pancreas from control rats showed normal pancreatic islets histoarchitecture. Our results also, indicate that the pancreas from diabetic rats show injury of pancreas tissue while the pancreas from diabetic rats treated with dried Urtica dioica leaf alcoholic and aqueous extracts show slight to moderate rearrangement of islets. According to our findings, dried Urtica dioica leaf alcoholic and aqueous extracts can cause a suitable repair of pancreatic tissue in streptozocin-induced diabetic experimental model. PMID:24551786

  15. Chemical composition of essential oil and anti trichomonas activity of leaf, stem, and flower of Rheum ribes L. extracts

    PubMed Central

    Naemi, Forough; Asghari, Gholamreza; Yousofi, Hossein; Yousefi, Hossein Ali

    2014-01-01

    Objectives: Trichomoniasis is one of the most common sexually transmitted diseases in humans and is caused by the protozoan Trichomonas vaginalis. Nowadays, increasing resistance to drugs such as metronidazole resulted in many problem, so new effective remedies are needed. In this study, we evaluate constituents of essential oil and anti-trichomonas activity of Rheum ribes. Materials and Methods: The essential oil from Rheum ribes L. flower growing wild in Iran was analyzed by GC/MS. The parasites were treated with different extract and fractions of the flower, stem, and leave of the plant. Anti-trichomonas activity was evaluated using an in vitro assay. Results: In all, 19 compounds were identified; palmitic acid [27.08%], n-eicosane [9.9%], n-tetracosane [7.34%], linoleic acid [6.56%], and ethyl linoleate [4.76%] were the main components of the oil. Rheum ribes extracts and fractions concentration dependently inhibited the ability of parasites to growth. This was associated with polarity of solvent used for fractionation and plant parts used for extraction. Conclusion: Findings demonstrate the potential of Rheum ribes extracts as an anti-trichomonas agent for human use. Further studies are required to evaluate its toxicity and safety. PMID:25050317

  16. Leaf litter leachates have the potential to increase lifespan, body size, and offspring numbers in a clone of Moina macrocopa.

    PubMed

    Hofmann, Sylva; Timofeyev, Maxim A; Putschew, Anke; Saul, Nadine; Menzel, Ralph; Steinberg, Christian E W

    2012-03-01

    Leaf litter processing is one major pathway of the global organic carbon cycle. During this process, a variety of small reactive organic compounds are released and transported to the aquatic environment, and may directly impact aquatic organisms as natural xenobiotics. We hypothesize that different forest stockings produce different leachate qualities, which in turn, stress the aquatic communities and, eventually, separate sensitive from tolerant species. Particularly, leachates from coniferous trees are suspected to have strongly adverse impacts on sensitive species. We exposed individuals of a clone of the model organism, Moina macrocopa, to comparable concentrations (approximately 2mM) of litter leachates of Norway spruce, Picea abies, Colorado blue spruce, Picea pungens, black poplar, Populus nigra, and sessile oak, Quercus petraea. The animals were fed ad libitum. The following life trait variables were recorded: growth, lifespan, and lifetime offspring. To identify, whether or not exposure to litter leachates provokes an internal oxidative stress in the exposed animals we measured the superoxide anion radical scavenging capacity via photoluminescence. Except of P. abies, exposure to the leachates reduced this antioxidant capacity by approximately 50%. Leachate exposures, except that of Quercus, increased body size and extended lifespan; furthermore, particularly the leachates of both Picea species significantly increased the offspring numbers. This unexpected behavior of exposed Moina may be based on food supplements (e.g., high carbohydrate contents) in the leachates or on yet to be identified regulatory pathways of energy allocation. Overall, our results suggest that the potentially adverse effects of litter leachates can be overruled by either bacterial-growth supporting fractions in the leachates or an internal compensation mechanism in the Moina individuals. PMID:22115468

  17. QTL mapping of stripe, leaf and stem rust resistance genes in a Kariega × Avocet S doubled haploid wheat population

    Microsoft Academic Search

    R. Prins; Z. A. Pretorius; C. M. Bender; A. Lehmensiek

    2011-01-01

    Adult plant resistance to stripe (yellow) rust in the wheat cultivar Kariega has previously been ascribed to a major quantitative\\u000a trait locus (QTL) on each of chromosomes 2B and 7D, along with a number of minor QTL. We have extended both the size of the\\u000a cv. Kariega × cv. Avocet S mapping population, and the marker coverage within it, by assembling a

  18. New multilocus variable-number tandem-repeat analysis tool for surveillance and local epidemiology of bacterial leaf blight and bacterial leaf streak of rice caused by Xanthomonas oryzae.

    PubMed

    Poulin, L; Grygiel, P; Magne, M; Gagnevin, L; Rodriguez-R, L M; Forero Serna, N; Zhao, S; El Rafii, M; Dao, S; Tekete, C; Wonni, I; Koita, O; Pruvost, O; Verdier, V; Vernière, C; Koebnik, R

    2015-01-01

    Multilocus variable-number tandem-repeat analysis (MLVA) is efficient for routine typing and for investigating the genetic structures of natural microbial populations. Two distinct pathovars of Xanthomonas oryzae can cause significant crop losses in tropical and temperate rice-growing countries. Bacterial leaf streak is caused by X. oryzae pv. oryzicola, and bacterial leaf blight is caused by X. oryzae pv. oryzae. For the latter, two genetic lineages have been described in the literature. We developed a universal MLVA typing tool both for the identification of the three X. oryzae genetic lineages and for epidemiological analyses. Sixteen candidate variable-number tandem-repeat (VNTR) loci were selected according to their presence and polymorphism in 10 draft or complete genome sequences of the three X. oryzae lineages and by VNTR sequencing of a subset of loci of interest in 20 strains per lineage. The MLVA-16 scheme was then applied to 338 strains of X. oryzae representing different pathovars and geographical locations. Linkage disequilibrium between MLVA loci was calculated by index association on different scales, and the 16 loci showed linear Mantel correlation with MLSA data on 56 X. oryzae strains, suggesting that they provide a good phylogenetic signal. Furthermore, analyses of sets of strains for different lineages indicated the possibility of using the scheme for deeper epidemiological investigation on small spatial scales. PMID:25398857

  19. New Multilocus Variable-Number Tandem-Repeat Analysis Tool for Surveillance and Local Epidemiology of Bacterial Leaf Blight and Bacterial Leaf Streak of Rice Caused by Xanthomonas oryzae

    PubMed Central

    Poulin, L.; Grygiel, P.; Magne, M.; Rodriguez-R, L. M.; Forero Serna, N.; Zhao, S.; El Rafii, M.; Dao, S.; Tekete, C.; Wonni, I.; Koita, O.; Pruvost, O.; Verdier, V.; Vernière, C.

    2014-01-01

    Multilocus variable-number tandem-repeat analysis (MLVA) is efficient for routine typing and for investigating the genetic structures of natural microbial populations. Two distinct pathovars of Xanthomonas oryzae can cause significant crop losses in tropical and temperate rice-growing countries. Bacterial leaf streak is caused by X. oryzae pv. oryzicola, and bacterial leaf blight is caused by X. oryzae pv. oryzae. For the latter, two genetic lineages have been described in the literature. We developed a universal MLVA typing tool both for the identification of the three X. oryzae genetic lineages and for epidemiological analyses. Sixteen candidate variable-number tandem-repeat (VNTR) loci were selected according to their presence and polymorphism in 10 draft or complete genome sequences of the three X. oryzae lineages and by VNTR sequencing of a subset of loci of interest in 20 strains per lineage. The MLVA-16 scheme was then applied to 338 strains of X. oryzae representing different pathovars and geographical locations. Linkage disequilibrium between MLVA loci was calculated by index association on different scales, and the 16 loci showed linear Mantel correlation with MLSA data on 56 X. oryzae strains, suggesting that they provide a good phylogenetic signal. Furthermore, analyses of sets of strains for different lineages indicated the possibility of using the scheme for deeper epidemiological investigation on small spatial scales. PMID:25398857

  20. Brain injury expands the numbers of neural stem cells and progenitors in the SVZ by enhancing their responsiveness to EGF

    PubMed Central

    Alagappan, Dhivyaa; Lazzarino, Deborah A; Felling, Ryan J; Balan, Murugabaskar; Kotenko, Sergei V; Levison, Steven W

    2009-01-01

    There is an increase in the numbers of neural precursors in the SVZ (subventricular zone) after moderate ischaemic injuries, but the extent of stem cell expansion and the resultant cell regeneration is modest. Therefore our studies have focused on understanding the signals that regulate these processes towards achieving a more robust amplification of the stem/progenitor cell pool. The goal of the present study was to evaluate the role of the EGFR [EGF (epidermal growth factor) receptor] in the regenerative response of the neonatal SVZ to hypoxic/ischaemic injury. We show that injury recruits quiescent cells in the SVZ to proliferate, that they divide more rapidly and that there is increased EGFR expression on both putative stem cells and progenitors. With the amplification of the precursors in the SVZ after injury there is enhanced sensitivity to EGF, but not to FGF (fibroblast growth factor)-2. EGF-dependent SVZ precursor expansion, as measured using the neurosphere assay, is lost when the EGFR is pharmacologically inhibited, and forced expression of a constitutively active EGFR is sufficient to recapitulate the exaggerated proliferation of the neural stem/progenitors that is induced by hypoxic/ischaemic brain injury. Cumulatively, our results reveal that increased EGFR signalling precedes that increase in the abundance of the putative neural stem cells and our studies implicate the EGFR as a key regulator of the expansion of SVZ precursors in response to brain injury. Thus modulating EGFR signalling represents a potential target for therapies to enhance brain repair from endogenous neural precursors following hypoxic/ischaemic and other brain injuries. PMID:19570028

  1. Leaf development: a cellular perspective

    PubMed Central

    Kalve, Shweta; De Vos, Dirk; Beemster, Gerrit T. S.

    2014-01-01

    Through its photosynthetic capacity the leaf provides the basis for growth of the whole plant. In order to improve crops for higher productivity and resistance for future climate scenarios, it is important to obtain a mechanistic understanding of leaf growth and development and the effect of genetic and environmental factors on the process. Cells are both the basic building blocks of the leaf and the regulatory units that integrate genetic and environmental information into the developmental program. Therefore, to fundamentally understand leaf development, one needs to be able to reconstruct the developmental pathway of individual cells (and their progeny) from the stem cell niche to their final position in the mature leaf. To build the basis for such understanding, we review current knowledge on the spatial and temporal regulation mechanisms operating on cells, contributing to the formation of a leaf. We focus on the molecular networks that control exit from stem cell fate, leaf initiation, polarity, cytoplasmic growth, cell division, endoreduplication, transition between division and expansion, expansion and differentiation and their regulation by intercellular signaling molecules, including plant hormones, sugars, peptides, proteins, and microRNAs. We discuss to what extent the knowledge available in the literature is suitable to be applied in systems biology approaches to model the process of leaf growth, in order to better understand and predict leaf growth starting with the model species Arabidopsis thaliana. PMID:25132838

  2. Leaf water status and stem xylem flux in relation to soil drought in five temperate broad-leaved tree species with contrasting water use strategies

    Microsoft Academic Search

    Paul Köcher; Tobias Gebauer; Viviana Horna; Christoph Leuschner

    2009-01-01

    – \\u000a \\u000a • Five temperate broad-leaved tree species were compared with respect to their water consumption strategies under ample and\\u000a restricted water supply. We measured synchronously leaf conductance (g\\u000a L) in the sun canopy, xylem sap flux (J\\u000a s) and leaf water potential (predawn, ?pd and noon, ?noon) in adult trees in a mixed stand and related them to the fluctuations

  3. Growth synchrony between leaves and stems during twig development differs among plant functional types of subtropical rainforest woody species.

    PubMed

    Meng, Fengqun; Zhang, Guangfu; Li, Xincheng; Niklas, Karl J; Sun, Shucun

    2015-06-01

    During the development of woody twigs, the growth in leaf may or may not be proportional to the growth in stem. The presence or absence of a synchronicity between these two phenologies may reflect differences in life history adaptive strategies concerning carbon gain. We hypothesized that sun-adapted species are more likely to be less synchronous between growths in total leaf area (TLA) and stem length compared with shade-adapted species, with a bias in growth in stem length, and that shade-adapted species are more likely to be more synchronous between increases in individual leaf area (ILA) (leaf size) and leaf number (LN) during twig development compared with sun-adapted species, giving priority to growth of leaf size. We tested these two hypotheses by recording the phenologies of leaf emergence, leaf expansion and stem elongation during twig development for 19 evergreen woody species (including five shade-adapted understory species, six sun-adapted understory species and eight sun-adapted canopy species) in a subtropical evergreen broad-leaved forest in eastern China. We constructed indices to characterize the synchronicity between TLA and stem length (?LS) and between leaf size and leaf number (?SN) and we derived the ? values from logistic functions taking the general form of A?=?Amax/[1?+?exp(??-??B)] (where A is the TLA or average ILA, B is the corresponding stem length or LN at a specific time, and Amax is the maximum TLA or the maximum ILA of a twig; the higher the numerical value of ?, the less synchronous the corresponding phenologies). Consistent with our hypotheses, sun-adapted species were higher both in ?LS and ?SN, showing less synchronous patterns in the growths of TLA vs stem length and leaf size vs LN during twig development. Moreover, ?LS and ?SN were significantly positively correlated with relative growth rates of LN and leaf size across species, as indicated by both analyses of ordinary regression and phylogenetic generalized least squares. The across-species synchronies during twig development show that the temporal dynamics of the leaf size-twig size spectrum is of adaptive significance in plants. We suggest that temporal dynamics of plant functional traits should be extensively studied to characterize plant life history. PMID:25813701

  4. An analysis of leaf shapes for a selection of deciduous trees

    E-print Network

    Rydeheard, David

    An analysis of leaf shapes for a selection of deciduous trees David E. Rydeheard #3; 1 Introduction. Measure at half-way point Measure at quarter-way point Measure at three-quarter-way point Leaf base: join with leaf-stem Leaf length Figure 1: Diagram of leaf measurements. To capture the range of shapes

  5. An analysis of leaf shapes for a selection of deciduous trees

    E-print Network

    Rydeheard, David

    An analysis of leaf shapes for a selection of deciduous trees David E. Rydeheard 1 Introduction. Measure at half-way pointMeasure at quarter-way point Measure at three-quarter-way point Leaf base: join with leaf-stem Leaf length Figure 1: Diagram of leaf measurements. To capture the range of shapes

  6. Novel Antioxidant Tripeptide “ACQ” Can Prevent UV-Induced Cell Death and Preserve the Number of Epidermal Stem Cells

    PubMed Central

    Choi, Hye-Ryung; Shin, Jung-Won; Na, Jung-Im; Nam, Kyung-Mi; Lee, Hyun-Sun; Park, Kyoung-Chan

    2015-01-01

    We found that tripeptide “ACQ: alanine-cysteine-glutamine” has significant DPPH scavenging activity compared to that of glutathione. Antioxidant effects of ACQ were tested in in vitro and in vivo models. When treated with H2O2, mock treated fibroblasts and keratinocytes showed strong staining by H2DCFA. But, ACQ showed good protective effects against hydrogen peroxide treatment. When mice were fed for 2 or 4 weeks, similar protective effects were observed. In the control group, epidermis was severely damaged by UV irradiation and apoptotic keratinocytes were observed. There were also numerous TUNEL positive cells. But in the ACQ group, epidermis became thicker and there was no sign of severe damage. Interestingly, the number of p63 cells was also higher in ACQ fed mice. To confirm the stem cell rescuing effects of ACQ, three-dimensional skin samples were constructed. Results showed that ACQ increased the expression of integrin ?6 and the number of p63 positive cells. These findings showed that ACQ has good antioxidant activity and may increase stem cell activities by the regulation of integrin ?6. PMID:26199677

  7. Leaf hydraulic conductance for a tank bromeliad: axial and radial pathways for moving and conserving water.

    PubMed

    North, Gretchen B; Lynch, Frank H; Maharaj, Franklin D R; Phillips, Carly A; Woodside, Walter T

    2013-01-01

    Epiphytic plants in the Bromeliaceae known as tank bromeliads essentially lack stems and absorptive roots and instead take up water from reservoirs formed by their overlapping leaf bases. For such plants, leaf hydraulic conductance is plant hydraulic conductance. Their simple strap-shaped leaves and parallel venation make them suitable for modeling leaf hydraulic conductance based on vasculature and other anatomical and morphological traits. Plants of the tank bromeliad Guzmania lingulata were investigated in a lowland tropical forest in Costa Rica and a shaded glasshouse in Los Angeles, CA, USA. Stomatal conductance to water vapor and leaf anatomical variables related to hydraulic conductance were measured for both groups. Tracheid diameters and numbers of vascular bundles (veins) were used with the Hagen-Poiseuille equation to calculate axial hydraulic conductance. Measurements of leaf hydraulic conductance using the evaporative flux method were also made for glasshouse plants. Values for axial conductance and leaf hydraulic conductance were used in a model based on leaky cable theory to estimate the conductance of the radial pathway from the vein to the leaf surface and to assess the relative contributions of both axial and radial pathways. In keeping with low stomatal conductance, low stomatal density, low vein density, and narrow tracheid diameters, leaf hydraulic conductance for G. lingulata was quite low in comparison with most other angiosperms. Using the predicted axial conductance in the leaky cable model, the radial resistance across the leaf mesophyll was predicted to predominate; lower, more realistic values of axial conductance resulted in predicted radial resistances that were closer to axial resistance in their impact on total leaf resistance. Tracer dyes suggested that water uptake through the tank region of the leaf was not limiting. Both dye movement and the leaky cable model indicated that the leaf blade of G. lingulata was structurally and hydraulically well-suited to conserve water. PMID:23596446

  8. Leaf Hydraulic Conductance for a Tank Bromeliad: Axial and Radial Pathways for Moving and Conserving Water

    PubMed Central

    North, Gretchen B.; Lynch, Frank H.; Maharaj, Franklin D. R.; Phillips, Carly A.; Woodside, Walter T.

    2013-01-01

    Epiphytic plants in the Bromeliaceae known as tank bromeliads essentially lack stems and absorptive roots and instead take up water from reservoirs formed by their overlapping leaf bases. For such plants, leaf hydraulic conductance is plant hydraulic conductance. Their simple strap-shaped leaves and parallel venation make them suitable for modeling leaf hydraulic conductance based on vasculature and other anatomical and morphological traits. Plants of the tank bromeliad Guzmania lingulata were investigated in a lowland tropical forest in Costa Rica and a shaded glasshouse in Los Angeles, CA, USA. Stomatal conductance to water vapor and leaf anatomical variables related to hydraulic conductance were measured for both groups. Tracheid diameters and numbers of vascular bundles (veins) were used with the Hagen–Poiseuille equation to calculate axial hydraulic conductance. Measurements of leaf hydraulic conductance using the evaporative flux method were also made for glasshouse plants. Values for axial conductance and leaf hydraulic conductance were used in a model based on leaky cable theory to estimate the conductance of the radial pathway from the vein to the leaf surface and to assess the relative contributions of both axial and radial pathways. In keeping with low stomatal conductance, low stomatal density, low vein density, and narrow tracheid diameters, leaf hydraulic conductance for G. lingulata was quite low in comparison with most other angiosperms. Using the predicted axial conductance in the leaky cable model, the radial resistance across the leaf mesophyll was predicted to predominate; lower, more realistic values of axial conductance resulted in predicted radial resistances that were closer to axial resistance in their impact on total leaf resistance. Tracer dyes suggested that water uptake through the tank region of the leaf was not limiting. Both dye movement and the leaky cable model indicated that the leaf blade of G. lingulata was structurally and hydraulically well-suited to conserve water. PMID:23596446

  9. WOX13-like genes are required for reprogramming of leaf and protoplast cells into stem cells in the moss Physcomitrella patens.

    PubMed

    Sakakibara, Keiko; Reisewitz, Pascal; Aoyama, Tsuyoshi; Friedrich, Thomas; Ando, Sayuri; Sato, Yoshikatsu; Tamada, Yosuke; Nishiyama, Tomoaki; Hiwatashi, Yuji; Kurata, Tetsuya; Ishikawa, Masaki; Deguchi, Hironori; Rensing, Stefan A; Werr, Wolfgang; Murata, Takashi; Hasebe, Mitsuyasu; Laux, Thomas

    2014-04-01

    Many differentiated plant cells can dedifferentiate into stem cells, reflecting the remarkable developmental plasticity of plants. In the moss Physcomitrella patens, cells at the wound margin of detached leaves become reprogrammed into stem cells. Here, we report that two paralogous P. patens WUSCHEL-related homeobox 13-like (PpWOX13L) genes, homologs of stem cell regulators in flowering plants, are transiently upregulated and required for the initiation of cell growth during stem cell formation. Concordantly, ?ppwox13l deletion mutants fail to upregulate genes encoding homologs of cell wall loosening factors during this process. During the moss life cycle, most of the ?ppwox13l mutant zygotes fail to expand and initiate an apical stem cell to form the embryo. Our data show that PpWOX13L genes are required for the initiation of cell growth specifically during stem cell formation, in analogy to WOX stem cell functions in seed plants, but using a different cellular mechanism. PMID:24715456

  10. Volume 156, number 1,2 PHYSICS LETTERS A 3 June 1991 Poisson bracket for the Vlasov equation on a symplectic leaf

    E-print Network

    Morrison, Philip J.,

    for the Vlasov equation on a symplectic leaf Huanchun Ye, P.J. Morrison Physics Department and Institute to a given symplectic leaf. The restricted equation of motion is written in terms of a generating function leaf is the phase space of an ordinary Hamiltonian system.) Thus it is of interest to study

  11. 7 CFR 29.1029 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Agriculture 2 2014-01-01 2014-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco....

  12. 7 CFR 29.1029 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Agriculture 2 2013-01-01 2013-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco....

  13. 7 CFR 29.1029 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Agriculture 2 2012-01-01 2012-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco....

  14. Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions.

    PubMed

    Tomasetti, Cristian; Vogelstein, Bert

    2015-01-01

    Some tissue types give rise to human cancers millions of times more often than other tissue types. Although this has been recognized for more than a century, it has never been explained. Here, we show that the lifetime risk of cancers of many different types is strongly correlated (0.81) with the total number of divisions of the normal self-renewing cells maintaining that tissue's homeostasis. These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to "bad luck," that is, random mutations arising during DNA replication in normal, noncancerous stem cells. This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes. PMID:25554788

  15. Effect of spores of saprophytic fungi on phytoalexin accumulation in seeds of frog-eye leaf spot and stem canker-resistant and -susceptible soybean (Glycine max L.) cultivars.

    PubMed

    Garcez, W S; Martins, D; Garcez, F R; Marques, M R; Pereira, A A; Oliveira, L A; Rondon, J N; Peruca, A D

    2000-08-01

    Two saprophytic fungi (Mucor ramosissimus and Rhizopus sp.) were tested for their ability to induce phytoalexin production by seeds of frog-eye leaf spot and stem canker-resistant and -susceptible soybean (Glycine max L.) cultivars. Only M. ramosissimus was shown to elicit a response and qualitative differences in phytoalexin accumulation were found between the susceptible and resistant cultivars. Glyceollins I, II, and III and glycinol were isolated from the susceptible cultivar, whereas Glyceollins I, II, and III, glycinol, glyceocarpin, genistein, isoformononetin, and N-acetyltyramine accumulated in the resistant cultivar in response to the same fungal elicitor. Genistein was found to be an inducibly formed isoflavonoid instead of a constitutive metabolite in the resistant cultivar, whereas N-acetyltyramine is described for the first time as a soybean phytoalexin. All the compounds, except genistein, showed fungitoxic activity against Cladosporium sphaerospermum. Spectral data of the pterocarpan phytoalexins, genistein, and N-acetyltyramine are also given in this work. PMID:10956166

  16. Are leaf physiological traits related to leaf water isotopic enrichment in restinga woody species?

    PubMed

    Rosado, Bruno H P; De Mattos, Eduardo A; Sternberg, Leonel Da S L

    2013-09-01

    During plant-transpiration, water molecules having the lighter stable isotopes of oxygen and hydrogen evaporate and diffuse at a faster rate through the stomata than molecules having the heavier isotopes, which cause isotopic enrichment of leaf water. Although previous models have assumed that leaf water is well-mixed and isotopically uniform, non-uniform stomatal closure, promoting different enrichments between cells, and different pools of water within leaves, due to morpho-physiological traits, might lead to inaccuracies in isotopic models predicting leaf water enrichment. We evaluate the role of leaf morpho-physiological traits on leaf water isotopic enrichment in woody species occurring in a coastal vegetation of Brazil known as restinga. Hydrogen and oxygen stable isotope values of soil, plant stem and leaf water and leaf traits were measured in six species from restinga vegetation during a drought and a wet period. Leaf water isotopic enrichment relative to stem water was more homogeneous among species during the drought in contrast to the wet period suggesting convergent responses to deal to temporal heterogeneity in water availability. Average leaf water isotopic enrichment relative to stem water during the drought period was highly correlated with relative apoplastic water content. We discuss this observation in the context of current models of leaf water isotopic enrichment as a function of the Péclet effect. We suggest that future studies should include relative apoplastic water content in isotopic models. PMID:24068091

  17. A number of bone marrow mesenchymal stem cells but neither phenotype nor differentiation capacities changes with age of rats.

    PubMed

    Tokalov, Sergey V; Gruener, Susanne; Schindler, Sebastian; Iagunov, Alexey S; Baumann, Michael; Abolmaali, Nasreddin D

    2007-10-31

    Bone marrow (BM) derived mesenchymal stem cells (MSC) are pluripotent cells which can differentiate into osteogenic, adipogenic and other lineages. In spite of the broad interest, the information about the changes in BM cell composition, in particularly about the variation of MSC number and their properties in relation to the age of the donor is still controversial. The aim of this study was to investigate the age associated changes in variations of BM cell composition, phenotype and differentiation capacities of MSC using a rat model. Cell populations were characterized by flow cytometry using light scattering parameters, DNA content and a set of monoclonal antibodies. Single cell analysis was performed by conventional fluorescent microscopy. In vitro culture of MSC was established and their phenotype and capability for in vitro differentiation into osteogenic and adipogenic cells was shown. Age related changes in tibiae and femurs, amount of BM tissue, BM cell composition, proportions of separated MSC and yield of MSC in 2 weeks of in vitro culture were found. At the same time, neither change in phenotype no in differentiation capacities of MSC was registered. Age-related changes of the number of MSC should be taken into account whenever MSC are intended to be used for investigations. PMID:17978579

  18. Leaf Activities.

    ERIC Educational Resources Information Center

    Mingie, Walter

    Leaf activities can provide a means of using basic concepts of outdoor education to learn in elementary level subject areas. Equipment needed includes leaves, a clipboard with paper, and a pencil. A bag of leaves may be brought into the classroom if weather conditions or time do not permit going outdoors. Each student should pick a leaf, examine…

  19. Efficient Isolation and Gene Expression Profiling of Small Numbers of Neural Crest Stem Cells and Developing Schwann Cells

    Microsoft Academic Search

    Johanna Buchstaller; Lukas Sommer; Matthias Bodmer; Reinhard Hoffmann; Ueli Suter; Ned Mantei

    2004-01-01

    Schwann cells develop from multipotent neural crest stem cells and are important for neuronal survival, maintenance of axonal integrity, and myelination. We used transgenic mice expressing green fluorescent protein in a tissue-specific manner to isolate viable, pure populations of neural crest stem cells and developing Schwann cells, which are not readily accessible by microdissection. Starting with the minute amounts of

  20. Anatomy of chewed leaf blade particles of Cenchrus ciliaris and Lolium perenne in relation to digestion

    E-print Network

    Boyer, Edmond

    Anatomy of chewed leaf blade particles of Cenchrus ciliaris and Lolium perenne in relation of a larger programme, we have examined the anatomy of chewed leaf blade particles and intact blades to distinguish between leaf blade, leaf sheath and stem. The sheep ate C. ciliaris more slowly than L. perenne

  1. Leaf Development

    PubMed Central

    2013-01-01

    Leaves are the most important organs for plants. Without leaves, plants cannot capture light energy or synthesize organic compounds via photosynthesis. Without leaves, plants would be unable perceive diverse environmental conditions, particularly those relating to light quality/quantity. Without leaves, plants would not be able to flower because all floral organs are modified leaves. Arabidopsis thaliana is a good model system for analyzing mechanisms of eudicotyledonous, simple-leaf development. The first section of this review provides a brief history of studies on development in Arabidopsis leaves. This history largely coincides with a general history of advancement in understanding of the genetic mechanisms operating during simple-leaf development in angiosperms. In the second section, I outline events in Arabidopsis leaf development, with emphasis on genetic controls. Current knowledge of six important components in these developmental events is summarized in detail, followed by concluding remarks and perspectives. PMID:23864837

  2. Enhancing the Number of African Americans Who Pursue STEM PhDs: Meyerhoff Scholarship Program Outcomes, Processes, and Individual Predictors

    PubMed Central

    Maton, Kenneth I.; Sto Domingo, Mariano R.; Stolle-McAllister, Kathleen E.; Zimmerman, J. Lynn; Hrabowski, Freeman A.

    2011-01-01

    The current study examines the outcomes, processes, and individual predictors of pursuit of a STEM PhD among African-American students in the Meyerhoff Scholarship Program. Meyerhoff students were nearly five times more likely than comparison students to pursue a STEM PhD. Program components consistently rated as important were financial scholarship, being part of the Meyerhoff Program community, the Summer Bridge program, study groups, staff academic advising, and summer research opportunities. Furthermore, focus group findings revealed student internalization of key Meyerhoff Program values, including a commitment to excellence, accountability, group success, and giving back. In terms of individual predictors, multinomial logit regression analyses revealed that Meyerhoff students with higher levels of research excitement at college entry were more likely to pursue a STEM PhD. PMID:21841904

  3. Enhancing the Number of African Americans Who Pursue STEM PhDs: Meyerhoff Scholarship Program Outcomes, Processes, and Individual Predictors.

    PubMed

    Maton, Kenneth I; Sto Domingo, Mariano R; Stolle-McAllister, Kathleen E; Zimmerman, J Lynn; Hrabowski, Freeman A

    2009-01-01

    The current study examines the outcomes, processes, and individual predictors of pursuit of a STEM PhD among African-American students in the Meyerhoff Scholarship Program. Meyerhoff students were nearly five times more likely than comparison students to pursue a STEM PhD. Program components consistently rated as important were financial scholarship, being part of the Meyerhoff Program community, the Summer Bridge program, study groups, staff academic advising, and summer research opportunities. Furthermore, focus group findings revealed student internalization of key Meyerhoff Program values, including a commitment to excellence, accountability, group success, and giving back. In terms of individual predictors, multinomial logit regression analyses revealed that Meyerhoff students with higher levels of research excitement at college entry were more likely to pursue a STEM PhD. PMID:21841904

  4. Perspectives on leaf dorsoventral polarity

    Microsoft Academic Search

    Dóra Szakonyi; Alexis Moschopoulos; Mary E. Byrne

    2010-01-01

    Leaves occur in a vast array of shapes and sizes, with complex diversity contributing to optimization of the principal function\\u000a of photosynthesis. The program of development from a self-renewing stem cell population to a mature leaf has been of interest\\u000a to biologists for years. Many genes involved in this process have been identified, particularly in the model eudicot Arabidopsis,\\u000a so

  5. Predicting Stem Length of Cut Flower Roses at Harvest Using Stem Elongation Rates in Relationship to Developmental Events

    E-print Network

    Lieth, J. Heinrich

    113 Predicting Stem Length of Cut Flower Roses at Harvest Using Stem Elongation Rates Sciences, One Shields Ave. University of California, Davis, CA 95616 USA Keywords: Richards function, stem quality, leaf unfolding, Rosa hybrida Abstract Stem length is a major determinant of rose productivity

  6. Understanding STEM: Current Perceptions

    ERIC Educational Resources Information Center

    Brown, Ryan; Brown, Joshua; Reardon, Kristin; Merrill, Chris

    2011-01-01

    In many ways, the push for STEM (science, technology, engineering, and mathematics) education appears to have grown from a concern for the low number of future professionals to fill STEM jobs and careers and economic and educational competitiveness. The proponents of STEM education believe that by increasing math and science requirements in…

  7. Variable Number of Tandem Repeat Markers in the Genome Sequence of Mycosphaerella Fijiensis, the Causal Agent of Black Leaf Streak Disease of Banana (Musa spp.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mycosphaerella fijiensis, the causal agent of banana leaf streak disease (commonly known as black Sigatoka), is the most devastating pathogen attacking bananas (Musa spp). Recently the whole genome sequence of M. fijiensis became available. This sequence was screened for the presence of Variable Num...

  8. Species-Specific Effects on Throughfall Kinetic Energy in Subtropical Forest Plantations Are Related to Leaf Traits and Tree Architecture.

    PubMed

    Goebes, Philipp; Bruelheide, Helge; Härdtle, Werner; Kröber, Wenzel; Kühn, Peter; Li, Ying; Seitz, Steffen; von Oheimb, Goddert; Scholten, Thomas

    2015-01-01

    Soil erosion is a key threat to many ecosystems, especially in subtropical China where high erosion rates occur. While the mechanisms that induce soil erosion on agricultural land are well understood, soil erosion processes in forests have rarely been studied. Throughfall kinetic energy (TKE) is influenced in manifold ways and often determined by the tree's leaf and architectural traits. We investigated the role of species identity in mono-specific stands on TKE by asking to what extent TKE is species-specific and which leaf and architectural traits account for variation in TKE. We measured TKE of 11 different tree species planted in monocultures in a biodiversity-ecosystem-functioning experiment in subtropical China, using sand-filled splash cups during five natural rainfall events in summer 2013. In addition, 14 leaf and tree architectural traits were measured and linked to TKE. Our results showed that TKE was highly species-specific. Highest TKE was found below Choerospondias axillaris and Sapindus saponaria, while Schima superba showed lowest TKE. These species-specific effects were mediated by leaf habit, leaf area (LA), leaf pinnation, leaf margin, stem diameter at ground level (GD), crown base height (CBH), tree height, number of branches and leaf area index (LAI) as biotic factors and throughfall as abiotic factor. Among these, leaf habit, tree height and LA showed the highest effect sizes on TKE and can be considered as major drivers of TKE. TKE was positively influenced by LA, GD, CBH, tree height, LAI, and throughfall amount while it was negatively influenced by the number of branches. TKE was lower in evergreen, simple leaved and dentate leaved than in deciduous, pinnated or entire leaved species. Our results clearly showed that soil erosion in forest plantations can be mitigated by the appropriate choice of tree species. PMID:26079260

  9. Species-Specific Effects on Throughfall Kinetic Energy in Subtropical Forest Plantations Are Related to Leaf Traits and Tree Architecture

    PubMed Central

    Bruelheide, Helge; Härdtle, Werner; Kröber, Wenzel; Li, Ying; von Oheimb, Goddert

    2015-01-01

    Soil erosion is a key threat to many ecosystems, especially in subtropical China where high erosion rates occur. While the mechanisms that induce soil erosion on agricultural land are well understood, soil erosion processes in forests have rarely been studied. Throughfall kinetic energy (TKE) is influenced in manifold ways and often determined by the tree’s leaf and architectural traits. We investigated the role of species identity in mono-specific stands on TKE by asking to what extent TKE is species-specific and which leaf and architectural traits account for variation in TKE. We measured TKE of 11 different tree species planted in monocultures in a biodiversity-ecosystem-functioning experiment in subtropical China, using sand-filled splash cups during five natural rainfall events in summer 2013. In addition, 14 leaf and tree architectural traits were measured and linked to TKE. Our results showed that TKE was highly species-specific. Highest TKE was found below Choerospondias axillaris and Sapindus saponaria, while Schima superba showed lowest TKE. These species-specific effects were mediated by leaf habit, leaf area (LA), leaf pinnation, leaf margin, stem diameter at ground level (GD), crown base height (CBH), tree height, number of branches and leaf area index (LAI) as biotic factors and throughfall as abiotic factor. Among these, leaf habit, tree height and LA showed the highest effect sizes on TKE and can be considered as major drivers of TKE. TKE was positively influenced by LA, GD, CBH, tree height, LAI, and throughfall amount while it was negatively influenced by the number of branches. TKE was lower in evergreen, simple leaved and dentate leaved than in deciduous, pinnated or entire leaved species. Our results clearly showed that soil erosion in forest plantations can be mitigated by the appropriate choice of tree species. PMID:26079260

  10. Numbers

    NSDL National Science Digital Library

    2013-06-14

    The purpose of this video tutorial is to review a couple ways in which we think about numbers. Thinking in terms of street numbers, money in bank accounts, and quantum particles (e.g. Bose-Einstein condensate) is contrasted with focusing on associating numbers with distinguishable manipulatives, as is more familiar in K-8 courses. This video concludes with a reminder that the symbol "infinity" is not, itself, a number.

  11. The Analysis of Leaf Shape Using Fractal Geometry.

    ERIC Educational Resources Information Center

    Hartvigsen, Gregg

    2000-01-01

    Describes ways to examine leaf structure and shape using fractal geometry. Students can test hypotheses using the leaves of replicated plants to look for non-linear trends in leaf shape along the stems of plants, across species, and under different environmental growth conditions. (SAH)

  12. Numbers

    NSDL National Science Digital Library

    Jo Edkins

    2006-01-01

    This engaging web site contains information and interactive applets related to various number systems: Egyptian, Babylonian, Chinese, Greek, Roman, Mayan, and Arabic. Users learn the history and structure of each system as well as how to count and write numbers. The site also allows users to explore finger systems, calculating machines, other number bases, and "interesting numbers." A series of pages on data and graphs includes information and activities on gathering, analyzing, graphing and sorting data. (Because the section on the Arabic number system is so extensive, it is cataloged separately as a related resource.)

  13. LeafJ: An ImageJ Plugin for Semi-automated Leaf Shape Measurement

    PubMed Central

    Mumbach, Maxwell R.; Palmer, Christine M.

    2013-01-01

    High throughput phenotyping (phenomics) is a powerful tool for linking genes to their functions (see review1 and recent examples2-4). Leaves are the primary photosynthetic organ, and their size and shape vary developmentally and environmentally within a plant. For these reasons studies on leaf morphology require measurement of multiple parameters from numerous leaves, which is best done by semi-automated phenomics tools5,6. Canopy shade is an important environmental cue that affects plant architecture and life history; the suite of responses is collectively called the shade avoidance syndrome (SAS)7. Among SAS responses, shade induced leaf petiole elongation and changes in blade area are particularly useful as indices8. To date, leaf shape programs (e.g. SHAPE9, LAMINA10, LeafAnalyzer11, LEAFPROCESSOR12) can measure leaf outlines and categorize leaf shapes, but can not output petiole length. Lack of large-scale measurement systems of leaf petioles has inhibited phenomics approaches to SAS research. In this paper, we describe a newly developed ImageJ plugin, called LeafJ, which can rapidly measure petiole length and leaf blade parameters of the model plant Arabidopsis thaliana. For the occasional leaf that required manual correction of the petiole/leaf blade boundary we used a touch-screen tablet. Further, leaf cell shape and leaf cell numbers are important determinants of leaf size13. Separate from LeafJ we also present a protocol for using a touch-screen tablet for measuring cell shape, area, and size. Our leaf trait measurement system is not limited to shade-avoidance research and will accelerate leaf phenotyping of many mutants and screening plants by leaf phenotyping. PMID:23380664

  14. ``Stemness'': Transcriptional Profiling of Embryonic and Adult Stem Cells

    Microsoft Academic Search

    Miguel Ramalho-Santos; Soonsang Yoon; Yumi Matsuzaki; Richard C. Mulligan; Douglas A. Melton

    2002-01-01

    The transcriptional profiles of mouse embryonic, neural, and hematopoietic stem cells were compared to define a genetic program for stem cells. A total of 216 genes are enriched in all three types of stem cells, and several of these genes are clustered in the genome. When compared to differentiated cell types, stem cells express a significantly higher number of genes

  15. Geminin deletion increases the number of fetal hematopoietic stem cells by affecting the expression of key transcription factors.

    PubMed

    Karamitros, Dimitris; Patmanidi, Alexandra L; Kotantaki, Panoraia; Potocnik, Alexandre J; Bähr-Ivacevic, Tomi; Benes, Vladimir; Lygerou, Zoi; Kioussis, Dimitris; Taraviras, Stavros

    2015-01-01

    Balancing stem cell self-renewal and initiation of lineage specification programs is essential for the development and homeostasis of the hematopoietic system. We have specifically ablated geminin in the developing murine hematopoietic system and observed profound defects in the generation of mature blood cells, leading to embryonic lethality. Hematopoietic stem cells (HSCs) accumulated in the fetal liver following geminin ablation, while committed progenitors were reduced. Genome-wide transcriptome analysis identified key HSC transcription factors as being upregulated upon geminin deletion, revealing a gene network linked with geminin that controls fetal hematopoiesis. In order to obtain mechanistic insight into the ability of geminin to regulate transcription, we examined Hoxa9 as an example of a key gene in definitive hematopoiesis. We demonstrate that in human K562 cells geminin is associated with HOXA9 regulatory elements and its absence increases HOXA9 transcription similarly to that observed in vivo. Moreover, silencing geminin reduced recruitment of the PRC2 component SUZ12 to the HOXA9 locus and resulted in an increase in RNA polymerase II recruitment and H3K4 trimethylation (H3K4me3), whereas the repressive marks H3K9me3 and H3K27me3 were reduced. The chromatin landscape was also modified at the regulatory regions of HOXA10 and GATA1. K562 cells showed a reduced ability to differentiate to erythrocytes and megakaryocytes upon geminin silencing. Our data suggest that geminin is indispensable for fetal hematopoiesis and regulates the generation of a physiological pool of stem and progenitor cells in the fetal hematopoietic system. PMID:25516969

  16. From the Cover: Remodeling of the postnatal mouse testis is accompanied by dramatic changes in stem cell number and niche accessibility

    Microsoft Academic Search

    Takashi Shinohara; Kyle E. Orwig; Mary R. Avarbock; Ralph L. Brinster

    2001-01-01

    Little is known about stem cell biology or the specialized environments or niches believed to control stem cell renewal and differentiation in self-renewing tissues of the body. Functional assays for stem cells are available only for hematopoiesis and spermatogenesis, and the microenvironment, or niche, for hematopoiesis is relatively inaccessible, making it difficult to analyze donor stem cell colonization events in

  17. Original article Allometric relationships for biomass and leaf area of

    E-print Network

    Boyer, Edmond

    variance; regressions improved when tree height was used as well. Crown dimensions increased with stem size increased from the tree top down to the crown base; this pattern did not significantly differ among trees were i) to establish allometric relationships among stem and crown dimensions, biomass, and leaf area

  18. 7 CFR 29.2301 - Stem.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Agriculture 2 2010-01-01 2010-01-01 false Stem. 29.2301 Section 29.2301 Agriculture Regulations...Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2301 Stem. The midrib or large central vein of a tobacco leaf....

  19. 7 CFR 29.3549 - Stem.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Agriculture 2 2012-01-01 2012-01-01 false Stem. 29.3549 Section 29.3549 Agriculture Regulations...s. Types 35, 36, 37 and Foreign Type 95) § 29.3549 Stem. The midrib or large central vein of a tobacco leaf....

  20. 7 CFR 29.1061 - Stem.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Agriculture 2 2011-01-01 2011-01-01 false Stem. 29.1061 Section 29.1061 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1061 Stem. The midrib or large central vein of a tobacco leaf....

  1. 7 CFR 29.1061 - Stem.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Agriculture 2 2010-01-01 2010-01-01 false Stem. 29.1061 Section 29.1061 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1061 Stem. The midrib or large central vein of a tobacco leaf....

  2. 7 CFR 29.2301 - Stem.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Agriculture 2 2011-01-01 2011-01-01 false Stem. 29.2301 Section 29.2301 Agriculture Regulations...Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2301 Stem. The midrib or large central vein of a tobacco leaf....

  3. 7 CFR 29.3059 - Stem.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.3059 Section 29.3059 Agriculture Regulations...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3059 Stem. The midrib or large central vein of a tobacco leaf....

  4. 7 CFR 29.1061 - Stem.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Agriculture 2 2014-01-01 2014-01-01 false Stem. 29.1061 Section 29.1061 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1061 Stem. The midrib or large central vein of a tobacco leaf....

  5. 7 CFR 29.2301 - Stem.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Agriculture 2 2012-01-01 2012-01-01 false Stem. 29.2301 Section 29.2301 Agriculture Regulations...Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2301 Stem. The midrib or large central vein of a tobacco leaf....

  6. 7 CFR 29.3549 - Stem.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Agriculture 2 2014-01-01 2014-01-01 false Stem. 29.3549 Section 29.3549 Agriculture Regulations...s. Types 35, 36, 37 and Foreign Type 95) § 29.3549 Stem. The midrib or large central vein of a tobacco leaf....

  7. 7 CFR 29.2553 - Stem.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Agriculture 2 2014-01-01 2014-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) § 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

  8. 7 CFR 29.2553 - Stem.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Agriculture 2 2010-01-01 2010-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) § 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

  9. 7 CFR 29.3549 - Stem.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Agriculture 2 2011-01-01 2011-01-01 false Stem. 29.3549 Section 29.3549 Agriculture Regulations...s. Types 35, 36, 37 and Foreign Type 95) § 29.3549 Stem. The midrib or large central vein of a tobacco leaf....

  10. 7 CFR 29.3549 - Stem.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.3549 Section 29.3549 Agriculture Regulations...s. Types 35, 36, 37 and Foreign Type 95) § 29.3549 Stem. The midrib or large central vein of a tobacco leaf....

  11. 7 CFR 29.3549 - Stem.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Agriculture 2 2010-01-01 2010-01-01 false Stem. 29.3549 Section 29.3549 Agriculture Regulations...s. Types 35, 36, 37 and Foreign Type 95) § 29.3549 Stem. The midrib or large central vein of a tobacco leaf....

  12. 7 CFR 29.2301 - Stem.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Agriculture 2 2014-01-01 2014-01-01 false Stem. 29.2301 Section 29.2301 Agriculture Regulations...Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2301 Stem. The midrib or large central vein of a tobacco leaf....

  13. 7 CFR 29.3059 - Stem.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Agriculture 2 2011-01-01 2011-01-01 false Stem. 29.3059 Section 29.3059 Agriculture Regulations...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3059 Stem. The midrib or large central vein of a tobacco leaf....

  14. 7 CFR 29.2553 - Stem.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Agriculture 2 2011-01-01 2011-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) § 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

  15. 7 CFR 29.1061 - Stem.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Agriculture 2 2012-01-01 2012-01-01 false Stem. 29.1061 Section 29.1061 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1061 Stem. The midrib or large central vein of a tobacco leaf....

  16. 7 CFR 29.2301 - Stem.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.2301 Section 29.2301 Agriculture Regulations...Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2301 Stem. The midrib or large central vein of a tobacco leaf....

  17. 7 CFR 29.3059 - Stem.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Agriculture 2 2012-01-01 2012-01-01 false Stem. 29.3059 Section 29.3059 Agriculture Regulations...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3059 Stem. The midrib or large central vein of a tobacco leaf....

  18. 7 CFR 29.2553 - Stem.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) § 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

  19. 7 CFR 29.3059 - Stem.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Agriculture 2 2014-01-01 2014-01-01 false Stem. 29.3059 Section 29.3059 Agriculture Regulations...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3059 Stem. The midrib or large central vein of a tobacco leaf....

  20. 7 CFR 29.1061 - Stem.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Agriculture 2 2013-01-01 2013-01-01 false Stem. 29.1061 Section 29.1061 Agriculture Regulations...Types 11, 12, 13, 14 and Foreign Type 92) § 29.1061 Stem. The midrib or large central vein of a tobacco leaf....

  1. 7 CFR 29.3059 - Stem.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Agriculture 2 2010-01-01 2010-01-01 false Stem. 29.3059 Section 29.3059 Agriculture Regulations...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3059 Stem. The midrib or large central vein of a tobacco leaf....

  2. 7 CFR 29.2553 - Stem.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Agriculture 2 2012-01-01 2012-01-01 false Stem. 29.2553 Section 29.2553 Agriculture Regulations...u.s. Types 22, 23, and Foreign Type 96) § 29.2553 Stem. The midrib or large central vein of a tobacco leaf....

  3. STEM CELL REGULATION IN THE ARABIDOPSIS SHOOT APICAL MERISTEM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aerial structure of higher plants is generated dynamically throughout the life cycle through the activity of stem cells that are located at the growing shoot tip, the apical meristem. The stem cells continuously divide to renew themselves and provide cells for leaf, stem and flower formation. St...

  4. Better Algorithms and Bounds for Directed Maximum Leaf Problems

    E-print Network

    Krivelevich, Michael

    Better Algorithms and Bounds for Directed Maximum Leaf Problems Noga Alon 1 , Fedor V. Fomin 2 of Mathematical Sciences Chennai, 600 017, India saket@imsc.res.in Abstract. The Directed Maximum Leaf Out Maximum Leaf Out­Branching problem is to find an out­branching in a given digraph with the maximum number

  5. Physical Activity Increases the Total Number of Bone-Marrow-Derived Mesenchymal Stem Cells, Enhances Their Osteogenic Potential, and Inhibits Their Adipogenic Properties

    PubMed Central

    Mar?dziak, Monika; ?mieszek, Agnieszka; Chrz?stek, Klaudia; Basinska, Katarzyna; Marycz, Krzysztof

    2015-01-01

    Aging and sedentary lifestyle are common nowadays and are associated with the increasing number of chronic diseases. Thus, physical activity is recommended as one of three healthy behavior factors that play a crucial role in health prophylaxis. In the present study, we were interested whether physical activity influences the number and potential of bone-marrow-derived mesenchymal stem cells BMMSCs. In this study, four-week-old male C57Bl/6 mice were trained on a treadmill at progressive speeds over a 5-week period. Comparisons made between exercised (EX) and sedentary animal groups revealed (i) significantly higher number of MSCs in EX animals, (ii) elevated alkaline phosphatase (ALP) activity, (iii) increased level of osteopontin (OPN) and osteocalcin (OCL), and (iv) reduced marrow cavity fat. The results obtained support the thesis that EX may play a substantial role in the regeneration of mesenchymal tissues. Therefore, EX may represent a novel, nonpharmacological strategy of slowing down age-related decline of the musculoskeletal functions.

  6. Auxin depletion from leaf primordia contributes to organ patterning.

    PubMed

    Qi, Jiyan; Wang, Ying; Yu, Ting; Cunha, Alexandre; Wu, Binbin; Vernoux, Teva; Meyerowitz, Elliot; Jiao, Yuling

    2014-12-30

    Stem cells are responsible for organogenesis, but it is largely unknown whether and how information from stem cells acts to direct organ patterning after organ primordia are formed. It has long been proposed that the stem cells at the plant shoot apex produce a signal, which promotes leaf adaxial-abaxial (dorsoventral) patterning. Here we show the existence of a transient low auxin zone in the adaxial domain of early leaf primordia. We also demonstrate that this adaxial low auxin domain contributes to leaf adaxial-abaxial patterning. The auxin signal is mediated by the auxin-responsive transcription factor MONOPTEROS (MP), whose constitutive activation in the adaxial domain promotes abaxial cell fate. Furthermore, we show that auxin flow from emerging leaf primordia to the shoot apical meristem establishes the low auxin zone, and that this auxin flow contributes to leaf polarity. Our results provide an explanation for the hypothetical meristem-derived leaf polarity signal. Opposite to the original proposal, instead of a signal derived from the meristem, we show that a signaling molecule is departing from the primordium to the meristem to promote robustness in leaf patterning. PMID:25512543

  7. Auxin depletion from leaf primordia contributes to organ patterning

    PubMed Central

    Qi, Jiyan; Wang, Ying; Yu, Ting; Cunha, Alexandre; Wu, Binbin; Vernoux, Teva; Meyerowitz, Elliot; Jiao, Yuling

    2014-01-01

    Stem cells are responsible for organogenesis, but it is largely unknown whether and how information from stem cells acts to direct organ patterning after organ primordia are formed. It has long been proposed that the stem cells at the plant shoot apex produce a signal, which promotes leaf adaxial-abaxial (dorsoventral) patterning. Here we show the existence of a transient low auxin zone in the adaxial domain of early leaf primordia. We also demonstrate that this adaxial low auxin domain contributes to leaf adaxial-abaxial patterning. The auxin signal is mediated by the auxin-responsive transcription factor MONOPTEROS (MP), whose constitutive activation in the adaxial domain promotes abaxial cell fate. Furthermore, we show that auxin flow from emerging leaf primordia to the shoot apical meristem establishes the low auxin zone, and that this auxin flow contributes to leaf polarity. Our results provide an explanation for the hypothetical meristem-derived leaf polarity signal. Opposite to the original proposal, instead of a signal derived from the meristem, we show that a signaling molecule is departing from the primordium to the meristem to promote robustness in leaf patterning. PMID:25512543

  8. Leaf Modeling and Constrained Leaf Morphing in Leaf Space Saurabh Garg1

    E-print Network

    Leow, Wee Kheng

    Leaf Modeling and Constrained Leaf Morphing in Leaf Space Saurabh Garg1 , Leow Wee Kheng1 1 School@comp.nus.edu.sg Morphing from an elliptic leaf (first row, first image) to a deltoid leaf (second row, last image) with a constraint of a leaf with both basal and apical extension (second row, first image). Abstract Leaf modeling

  9. Effects of Integrating and Non-Integrating Reprogramming Methods on Copy Number Variation and Genomic Stability of Human Induced Pluripotent Stem Cells

    PubMed Central

    Huang, Yuling; Song, Bing; Chen, Yaoyong; Gao, Xingcheng; He, Wenyin; Sun, Xiaofang; Fan, Yong

    2015-01-01

    Human-induced pluripotent stem cells (iPSCs) are derived from differentiated somatic cells using defined factors and provide a renewable source of autologous cells for cell therapy. Many reprogramming methods have been employed to generate human iPSCs, including the use of integrating vectors and non-integrating vectors. Maintenance of the genomic integrity of iPSCs is highly desirable if the cells are to be used in clinical applications. Here, using the Affymetrix Cytoscan HD array, we investigated the genomic aberration profiles of 19 human cell lines: 5 embryonic stem cell (ESC) lines, 6 iPSC lines derived using integrating vectors (“integrating iPSC lines”), 6 iPSC lines derived using non-integrating vectors (“non-integrating iPSC lines”), and the 2 parental cell lines from which the iPSCs were derived. The genome-wide copy number variation (CNV), loss of heterozygosity (LOH) and mosaicism patterns of integrating and non-integrating iPSC lines were investigated. The maximum sizes of CNVs in the genomes of the integrating iPSC lines were 20 times higher than those of the non-integrating iPSC lines. Moreover, the total number of CNVs was much higher in integrating iPSC lines than in other cell lines. The average numbers of novel CNVs with a low degree of overlap with the DGV and of likely pathogenic CNVs with a high degree of overlap with the ISCA (International Symposium on Computer Architecture) database were highest in integrating iPSC lines. Different single nucleotide polymorphisms (SNP) calls revealed that, using the parental cell genotype as a reference, integrating iPSC lines displayed more single nucleotide variations and mosaicism than did non-integrating iPSC lines. This study describes the genome stability of human iPSCs generated using either a DNA-integrating or non-integrating reprogramming method, of the corresponding somatic cells, and of hESCs. Our results highlight the importance of using a high-resolution method to monitor genomic aberrations in iPSCs intended for clinical applications to avoid any negative effects of reprogramming or cell culture. PMID:26131765

  10. Root Hypoxia Reduces Leaf Growth 1

    PubMed Central

    Smit, Barbara A.; Neuman, Dawn S.; Stachowiak, Matthew L.

    1990-01-01

    This study examined the potential role of restricted phloem export, or import of substances from the roots in the leaf growth response to root hypoxia. In addition, the effects of root hypoxia on abscisic acid (ABA) and zeatin riboside (ZR) levels were measured and their effects on in vitro growth determined. Imposition of root hypoxia in the dark when transpirational water flux was minimal delayed the reduction in leaf growth until the following light period. Restriction of phloem transport by stem girdling did not eliminate the hypoxia-induced reduction in leaf growth. In vitro growth of leaf discs was inhibited in the presence of xylem sap collected from hypoxic roots, and also by millimolar ABA. Disc growth was promoted by sap from aerated roots and by 0.1 micromolar ZR. The flux of both ABA and ZR was reduced in xylem sap from hypoxic roots. Leaf ABA transiently increased twofold after 24 hours of hypoxia exposure but there were no changes in leaf cytokinin levels. Images Figure 3 Figure 4 PMID:16667366

  11. Discovering candidate genes that regulate resin canal number in Pinus taeda stems by integrating genetic analysis across environments, ages, and populations.

    PubMed

    Westbrook, Jared W; Walker, Alejandro R; Neves, Leandro G; Munoz, Patricio; Resende, Marcio F R; Neale, David B; Wegrzyn, Jill L; Huber, Dudley A; Kirst, Matias; Davis, John M; Peter, Gary F

    2015-01-01

    Genetically improving constitutive resin canal development in Pinus stems may enhance the capacity to synthesize terpenes for bark beetle resistance, chemical feedstocks, and biofuels. To discover genes that potentially regulate axial resin canal number (RCN), single nucleotide polymorphisms (SNPs) in 4027 genes were tested for association with RCN in two growth rings and three environments in a complex pedigree of 520 Pinus taeda individuals (CCLONES). The map locations of associated genes were compared with RCN quantitative trait loci (QTLs) in a (P. taeda × Pinus elliottii) × P. elliottii pseudo-backcross of 345 full-sibs (BC1). Resin canal number was heritable (h(2) ˜ 0.12-0.21) and positively genetically correlated with xylem growth (rg ˜ 0.32-0.72) and oleoresin flow (rg ˜ 0.15-0.51). Sixteen well-supported candidate regulators of RCN were discovered in CCLONES, including genes associated across sites and ages, unidirectionally associated with oleoresin flow and xylem growth, and mapped to RCN QTLs in BC1. Breeding is predicted to increase RCN 11% in one generation and could be accelerated with genomic selection at accuracies of 0.45-0.52 across environments. There is significant genetic variation for RCN in loblolly pine, which can be exploited in breeding for elevated terpene content. PMID:25266813

  12. Stem Cells and Renal Regeneration

    Microsoft Academic Search

    C. Roufosse; H. T. Cook

    2008-01-01

    The role of embryonal or adult stem cells, in particular bone marrow (BM)-derived stem cells, in regenerating the kidney after injury has been the subject of intensive investigation. BM-derived stem cells have been shown to give rise to small numbers of most renal cell types, including tubular cells, mesangial cells, podocytes, vascular cells and interstitial cells. However, the role this

  13. Elm Leaf Beetle

    E-print Network

    Patrick, Carl D.

    2002-05-22

    Elm leaf beetles damage all varieties of elm trees. Learn how to identify this insect and understand its biology and life cycle. There are suggestions for controlling elm leaf beetles, as well as a table of insecticides effective against...

  14. Revisiting the Boundary Layer Leaf Water Isotopic Model

    NASA Astrophysics Data System (ADS)

    Feng, X.; Shu, Y.; Posmentier, E. S.; Sonder, L. J.; Yakir, D.

    2007-12-01

    The boundary layer (BL) model for oxygen or hydrogen isotopic composition of leaf water has been widely used in the past four decades, and has been incorporated into models that require information about leaf water isotopic variations. However, since its introduction, model predictions of the bulk leaf water have often exceeded observed isotopic enrichments. There are also cases in which the model yielded lower than observed isotopic enrichments of bulk leaf water. In general, underpredictions occur under relatively high humidity. In order to explain why the BL model overpredicts the isotopic composition, several modifications of the model have been proposed. However, no explanation exists for why the BL model underestimates observed isotopic enrichments. We recently developed a 2D model that successfully simulates the observed along-leaf 18O enrichment of pine needles, and can explain why the BL model could have over- or under-predicted the bulk leaf water ?18O values. In the BL model, bulk leaf water is isotopically equivalent to water at the evaporation site, fed directly by stem water. In a real leaf, however, stem water enters the base of the leaf and becomes progressively enriched in 18O towards the tip due to fractionation by transpiration, consistent with both our observations and behavior of the 2D model. Therefore, at least part of the leaf water, that near the base, would have isotopic values lower than water at transpiration sites predicted by the BL model, which might thus overestimate bulk isotope values. On the other hand, as water moves through a leaf, it becomes increasingly enriched in 18O, and the leaf water near the tip may have ?18O values well above the BL model prediction. Therefore, it is also possible for the BL model to underestimate the bulk leaf water ?18O. The actual isotopic composition of the bulk leaf water is a combination of these two effects. It is clear then that the BL model may not accurately predict the ?18O value of the bulk leaf water, because to do so would require the volumetric average of the ?18O in the depleted and enriched parts of the leaf to exactly equal the BL model prediction. Furthermore, if leaves are assumed to transpire fast under low humidity, our 2D model can also reproduce the humidity dependence of the discrepancy between observation and the BL model prediction. This suggests an interaction between environmental conditions and the physiological behavior of plants. If the simplicity of the BL model justifies its continued use, then it is important to investigate its accuracy further under different environmental conditions and for leaves with different morphologies and water transport pathways.

  15. Functional relationships between leaf hydraulics and leaf economic traits in response to nutrient addition in subtropical tree species.

    PubMed

    Villagra, Mariana; Campanello, Paula I; Bucci, Sandra J; Goldstein, Guillermo

    2013-12-01

    Leaves can be both a hydraulic bottleneck and a safety valve against hydraulic catastrophic dysfunctions, and thus changes in traits related to water movement in leaves and associated costs may be critical for the success of plant growth. A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) addition was done in a semideciduous Atlantic forest in northeastern Argentina. Saplings of five dominant canopy species were grown in similar gaps inside the forests (five control and five N?+?P addition plots). Leaf lifespan (LL), leaf mass per unit area (LMA), leaf and stem vulnerability to cavitation, leaf hydraulic conductance (K(leaf_area) and K(leaf_mass)) and leaf turgor loss point (TLP) were measured in the five species and in both treatments. Leaf lifespan tended to decrease with the addition of fertilizers, and LMA was significantly higher in plants with nutrient addition compared with individuals in control plots. The vulnerability to cavitation of leaves (P50(leaf)) either increased or decreased with the nutrient treatment depending on the species, but the average P50(leaf) did not change with nutrient addition. The P50(leaf) decreased linearly with increasing LMA and LL across species and treatments. These trade-offs have an important functional significance because more expensive (higher LMA) and less vulnerable leaves (lower P50(leaf)) are retained for a longer period of time. Osmotic potentials at TLP and at full turgor became more negative with decreasing P50(leaf) regardless of nutrient treatment. The K(leaf) on a mass basis was negatively correlated with LMA and LL, indicating that there is a carbon cost associated with increased water transport that is compensated by a longer LL. The vulnerability to cavitation of stems and leaves were similar, particularly in fertilized plants. Leaves in the species studied may not function as safety valves at low water potentials to protect the hydraulic pathway from water stress-induced cavitation. The lack of rainfall seasonality in the subtropical forest studied probably does not act as a selective pressure to enhance hydraulic segmentation between leaves and stems. PMID:24284866

  16. The inheritance of host plant effect on latency period of wheat leaf rust in spring wheat. II: Number of segregating factors and evidence for trangressive segregation in F3 and F5 generations

    Microsoft Academic Search

    L. H. M. Broers; Th. Jacobs

    1989-01-01

    Three partially resistant spring wheat cultivars, with a long latency period were crossed among each other and with the highly susceptible Little Club, with a very short latency period. Parents, F3 and F5 plants have been inoculated with the leaf rust race Flamingo in the young flag leaf stage to determine the latency period. From the crosses with Little Club,

  17. The inheritance of host plant effect on latency period of wheat leaf rust in spring wheat. I: Estimation of gene action and number of effective factors in F1, F2 and backcross generations

    Microsoft Academic Search

    Th. Jacobs; L. H. M. Broers

    1989-01-01

    Crosses were made between the highly susceptible Little Club and the partially resistant cultivars Westphal 12A, Akabozu and BH 1146 to obtain F1, F2 and backcross generations. Latency period (LP) was determined in plants inoculated at the young flag leaf stage with a monospore culture of race ‘Flamingo’ of wheat leaf rust. Broad sense heritability of LP in the F2

  18. STEM Career

    NSDL National Science Digital Library

    There are many groups and organizations in the United States working to encourage young people to enter STEM-related careers, and this website represents one of those endeavors. The STEM Career website was created by Professor Rich Feller of Colorado State University to help encourage young people to select just such a career path. The website contains updates on STEM career possibilities, and basic answers to questions like "Why STEM?" and "Why STEM Centric Career Development?" Visitors should also scan through the "STEM Disciplines" area on the homepage, as it contains resources about the job outlook for related STEM disciplines, such as biochemical engineering and engineering managers. Moving on, the site also features news updates from Professor Feller and his colleagues on subjects that include the ways in which corporations are promoting STEM education and women in STEM.

  19. First report of leaf spot caused by Cladosporium herbarum on Centaurea solstitialis in Greece

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the summer of 2003, an epidemic of dying yellow starthistle (YST) plants was found near Kozani, Greece. Plants had necrotic tan-brown leaf spots on most of the lower leaves and on the decurrent leaf bases along the stems. Virtually all plants in a solid stand of YST (about 0.5 ha) showed disease ...

  20. Antimicrobial and anti-inflammatory activity of folklore: Mallotus peltatus leaf extract

    Microsoft Academic Search

    Debprasad Chattopadhyay; G Arunachalam; Asit B Mandal; Tapas K Sur; Subash C Mandal; S. K Bhattacharya

    2002-01-01

    Since ages Mallotus peltatus (Geist) Muell. Arg. var acuminatus (Euphorbiaceae) leaf and stem bark is used in folk medicine to cure intestinal ailments and skin infections. In several intestinal ailments, localized inflammation is of common occurrence and hence we have evaluated the antimicrobial as well as anti-inflammatory activity of M. peltatus leaf extract. The crude methanol extract of M. peltatus

  1. Plant biomass and stem juice of the C4 sugarcane at elevated growth CO2 and temperature

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant biomass, stem juice and stem sugar were determined for four sugarcane cultivars grown for three months at daytime [CO2] of 360 (ambient) and 720 (doubled) ppm and temperatures (T) of 1.5 (near-ambient) and 6.0C higher than outside ambient T. Leaf area and biomass, stem biomass, stem juice and ...

  2. Derivation of normal diploid human embryonic stem cells from tripronuclear zygotes with analysis of their copy number variation and loss of heterozygosity.

    PubMed

    Chen, Xuemei; Niu, Wenbin; Wang, Fang; Yu, Wenzhu; Dai, Shanjun; Kong, Huijuan; Shu, Yimin; Sun, Yingpu

    2015-05-01

    This study sought to establish archives of genetic copy number variation (CNV) in human embryonic stem cell (hESC) lines that are associated with known diseases. We collected patients' fresh, discarded zygotes from in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) protocols. A total of 208 fresh, tripronuclear, discarded zygotes were also collected in this study from patients on the third day of their treatment cycle, prior to transfer. The blastula-formation rates were 13.51% (26/192) and 26.7% (4/15) while the high-quality blastocyst formation rates were 5.8% (11/192) and 20% (3/15) in the IVF and ICSI groups, respectively. The inner cell mass (ICM) from each embryo was mechanically separated, and then grown on feeder layers consisting of mouse embryonic fibroblasts and human foreskin fibroblasts (a 1:1 mixture). The hESC karyotype was determined by traditional G-banding; analysis of the results for the Zh19P25 and Zh20P24 cell lines showed that both were 46 XY. CNV and loss-of-heterozygosity analysis of hESC gDNA was performed to assess the genetic characteristics associated with molecular diseases using the high-resolution Infinium High-Density HumanCytoSNP-12 DNA chip. Seven CNVs in Zh19P25 and Zh20P24 were deletions, and a region that corresponds to Potocki-Shaffer disease, 11p11.2-11p11.12 in Zh20P24, showed a 2.98-Mb loss. These data together suggest that single-nucleotide polymorphism (SNP) microarray analysis for molecular cytogenetic features can help to distinguish hESC lines with a normal karyotype from tripronuclear zygotes with known, disease-related characteristics. Mol. Reprod. Dev. 82: 344-355, 2015. © 2015 Wiley Periodicals, Inc. PMID:25988573

  3. Leaf Pack Network

    NSDL National Science Digital Library

    The Leaf Pack Network (LPN) is a network of teachers and students investigating their local stream ecosystems by participating in the leaf pack experiment, which involves creating an artificial leaf pack (dry leaves in a mesh bag), immersing it in a stream for 3-4 weeks, and examining it for signs of aquatic insects as indicators of stream health. Participating classrooms share their data through the internet. This activity highlights the connection between streamside forests and the ecology of rivers and streams.

  4. Renal Stem Cells and Kidney Regeneration

    Microsoft Academic Search

    Takashi Yokoo; Akira Fukui; Kei Matsumoto; Tetsuya Kawamura

    \\u000a Significant advances have been made in stem cell research over the past decade. A number of non-hematopoietic sources of stem\\u000a cells (or progenitor cells) have been identified including endothelial stem cells and neural stem cells. These discoveries\\u000a have been a major step towards the potential regeneration of organs for clinical applications using stem cells. The worldwide\\u000a shortage of donor kidneys

  5. New perspectives in human stem cell therapeutic research

    Microsoft Academic Search

    Alan Trounson

    2009-01-01

    Human stem cells are in evaluation in clinical stem cell trials, primarily as autologous bone marrow studies, autologous and allogenic mesenchymal stem cell trials, and some allogenic neural stem cell transplantation projects. Safety and efficacy are being addressed for a number of disease state applications. There is considerable data supporting safety of bone marrow and mesenchymal stem cell transplants but

  6. Biomass reallocation and the mobilization of leaf resources support dune plant growth after sand burial.

    PubMed

    Gilbert, Matthew E; Ripley, Brad S

    2008-11-01

    The stimulation of dune plant growth in response to burial is a vital attribute allowing survival in areas of mobile sand. Numerous resource-related and physiological mechanisms of growth stimulation have been suggested in the past, but few have been tested comparatively. Manipulation experiments using Scaevola plumieri, an important subtropical coastal dune forming species, demonstrated that physiological shifts were of great importance in determining the nature of the stimulation response to burial. The production of stem length and replacement of leaf area were stimulated by burial, whereas net mass production was similar between buried and unburied treatments. Remobilization of buried leaf resources, seasonal effects, and a shift in biomass allocation to stem production played the greatest role in the compensatory growth response. Other factors, such as increased soil nutrients, changes in photosynthesis, and changes in the costs of producing tissue were of less importance. Thus, the stimulated growth of species adapted to live on mobile dunes is explained by a number of resource-related and physiological mechanisms acting in concert. PMID:18636986

  7. Multipotent somatic stem cells contribute to the stem cell niche in the Drosophila testis

    Microsoft Academic Search

    Justin Voog; Cecilia D'Alterio; D. Leanne Jones

    2008-01-01

    Adult stem cells reside in specialized microenvironments, or niches, that have an important role in regulating stem cell behaviour. Therefore, tight control of niche number, size and function is necessary to ensure the proper balance between stem cells and progenitor cells available for tissue homeostasis and wound repair. The stem cell niche in the Drosophila male gonad is located at

  8. STEM crisis or STEM surplus?

    E-print Network

    Xue, Yi, S.M. Massachusetts Institute of Technology

    2014-01-01

    The science, technology, engineering, and mathematics (STEM) workforce is a crucial driver of the U.S. economy. Over the last decade, there has been significant concern regarding the adequacy of the supply of STEM workers ...

  9. [Molecular mechanism of leaf development].

    PubMed

    Yan, Song; Yan, Chang-Jie; Gu, Ming-Hong

    2008-09-01

    Leaf plays important roles during plant development for their function of photosynthesis and transpiration. Leaf development includes initiation of leaf primordium and establishment of leaf polarity. Various studies indicate that leaf development is controlled through the interaction of transcription factors, small RNAs and auxin. This review focuses on re-cent advances in studying on leaf development and morphogenesis, and provides information on the regulation network in the process. PMID:18779169

  10. ASCOCHYTA LEAF SPOT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ascochyta leaf spot is a plant disease of wheat. It is often overlooked in association with other leaf spot diseases on wheat and is generally of minor economic importance in Europe, Japan, New Zealand, and North America. However, its distribution and frequency may be greater than realized, becaus...

  11. Leaf cutter ants

    NSDL National Science Digital Library

    N/A N/A (None; )

    2007-12-15

    There is much diversity between ants. Leaf cutter ants use their mandibles to cut leaf fragments and take them back to their home. They don't eat the leaves, but instead use them to grow fungus on. They then eat the fungus.

  12. GeoFORCE Texas: An Outreach Program that is Increasing the Number and Diversity of Students Completing STEM Degrees and Entering the Workforce

    NASA Astrophysics Data System (ADS)

    Snow, E.; Moore, S. L.

    2014-12-01

    GeoFORCE Texas is an outreach program of the Jackson School of Geosciences, University of Texas at Austin. Established in 2005 with the goal of increasing the number and diversity of students studying geosciences and engineering and entering the high-tech workforce, GeoFORCE has been highly successful. Key elements to that success will be presented here. GeoFORCE targets bright students in rural and inner-city schools where they are generally not academically challenged. Every summer throughout high school we take them on geologic field trips all over the country. In 2014, GeoFORCE led 15 field academies for about 600 students. The program is rigorous and academic. We emphasize college-level thinking skills. Because it is a 4-year program, they have a pretty good grounding in physical geology by the time they graduate. More importantly, they develop confidence in their ability to handle college, and a strong motivation to earn a college degree. GeoFORCE students are mostly minority (85%) and more than half will be the first in their family to graduate from college. GeoFORCE students exceed national averages in rates of going to college (97%), majoring in STEM fields (66%), majoring in geosciences (15%) and engineering (13%), and graduating from college (~85%). GeoFORCE is a public/private partnership and a workforce-focused program. The Jackson School funds staff and operating expenses (37%). Money for student programs comes from private industry (44%), state and federal grants (14%), and foundations and individual donors (5%). Our corporate partners are in the energy sector. In addition to funding, corporate sponsors attend the summer field programs, mentor GeoFORCE students, and provide opportunities for the students to visit the companies. As our students move toward college graduation, our industry and government partners have begun to hire them as interns. GeoFORCE graduates are now entering the workforce. Our first two cohorts are 4 and 5 years past high school graduation. That group of 155 students boasts 70 college graduates and another 60 still pursuing degrees. There are 19 geoscience majors and 9 engineers. They are also contributing to the body of science with a growing list of publications, including at least one at this meeting.

  13. Adult Stem and Progenitor Cells

    Microsoft Academic Search

    Martine Geraerts; Catherine M. Verfaillie

    2009-01-01

    \\u000a The discovery of adult stem cells in most adult tissues is the basis of a number of clinical studies that are carried out,\\u000a with therapeutic use of hematopoietic stem cells as a prime example. Intense scientific debate is still ongoing as to whether\\u000a adult stem cells may have a greater plasticity than previously thought. Although cells with some features of

  14. Comparison of changes in stem diameter and water potential values for detecting water stress in young almond trees

    Microsoft Academic Search

    P. A. Nortes; A. Pérez-Pastor; G. Egea; W. Conejero; R. Domingo

    2005-01-01

    Trunk diameter fluctuations (TDF) and the leaf water relation parameters, predawn and midday leaf water potential (?pd and ?md), midday stem water potential (?st) and midday leaf conductance (gl) were compared for use in detecting water stress and for helping with irrigation management in young almond trees. TDF were monitored throughout 2002 in three irrigation treatments: T1 (control), irrigated at

  15. Global Leaf Trait Relationships: Mass, Area, and the Leaf

    E-print Network

    Minnesota, University of

    Global Leaf Trait Relationships: Mass, Area, and the Leaf Economics Spectrum Jeanne L. D. Osnas,1,2 * Jeremy W. Lichstein,2 Peter B. Reich,3,4 Stephen W. Pacala1 The leaf economics spectrum (LES) describes multivariate correlations that constrain leaf traits of plant species primarily to a single axis of variation

  16. Short communication Leaf optical properties and photosynthetic leaf absorptances

    E-print Network

    Durako, Michael J.

    Short communication Leaf optical properties and photosynthetic leaf absorptances in several-species variability in the leaf optical properties of eight large-bodied seagrasses, Posidonia australis, Posidonia of Australia. Leaf spectral transmittance [TL(l)], reflectance [RL(l)], and non-photosynthetic absorptance [AL

  17. Soybean Endo-?-Mannanase GmMAN1 Is Not Associated with Leaf Abscission, but Might Be Involved in the Response to Wounding

    PubMed Central

    Yan, Min; Zhang, Yifan; Guo, Wenjuan; Wang, Xiaofeng

    2012-01-01

    The objective of this work is to investigate the relationship between endo-?-mannanase and leaf abscission, and response to wounding in soybean (Glycine max). An endo-?-mannanase gene GmMAN1 was cloned from the abscission zone in petiole explants, and was heterologously expressed in E. coli. Polyclonal antibodies were raised against the fusion protein. The increases in activity, isoform numbers, and amounts of transcripts and proteins of GmMAN1 were found not only in the abscission zone but also in the non-abscission zone during petiole abscission in the explants, but not in these two tissues during leaf abscission artificially induced by ethephon treatment in the intact plants. The changes in endo-?-mannanase expression patterns in these two tissues were probably induced by the inherent mechanical wounding during the preparation of explants. When soybean plants were wounded by removing half of the leaf blade of the first pair of true leaves, the transcripts and proteins of GmMAN1 were induced in the leaves and stem, leading to the increases in enzyme activity and isoform numbers in them. It is concluded that the soybean endo-?-mannanase GmMAN1 is not associated with leaf abscission, but might be involved in the response to wounding. PMID:23173047

  18. Arabidopsis thaliana homeobox 12 (ATHB12), a homeodomain-leucine zipper protein, regulates leaf growth by promoting cell expansion and endoreduplication.

    PubMed

    Hur, Yoon-Sun; Um, Ji-Hyun; Kim, Sunghan; Kim, Kyunga; Park, Hee-Jung; Lim, Jong-Seok; Kim, Woo-Young; Jun, Sang Eun; Yoon, Eun Kyung; Lim, Jun; Ohme-Takagi, Masaru; Kim, Donggiun; Park, Jongbum; Kim, Gyung-Tae; Cheon, Choong-Ill

    2015-01-01

    Arabidopsis thaliana homeobox 12 (ATHB12), a homeodomain-leucine zipper class I (HD-Zip I) gene, is highly expressed in leaves and stems, and induced by abiotic stresses, but its role in development remains obscure. To understand its function during plant development, we studied the effects of loss and gain of function. Expression of ATHB12 fused to the EAR-motif repression domain (SRDX) - P35 S ::ATHB12SRDX (A12SRDX) and PATHB 12 ::ATHB12SRDX - slowed both leaf and root growth, while the growth of ATHB12-overexpressing seedlings (A12OX) was accelerated. Microscopic examination revealed changes in the size and number of leaf cells. Ploidy was reduced in A12SRDX plants, accompanied by decreased cell expansion and increased cell numbers. By contrast, cell size was increased in A12OX plants, along with increased ploidy and elevated expression of cell cycle switch 52s (CCS52s), which are positive regulators of endoreduplication, indicating that ATHB12 promotes leaf cell expansion and endoreduplication. Overexpression of ATHB12 led to decreased phosphorylation of Arabidopsis thaliana ribosomal protein S6 (AtRPS6), a regulator of cell growth. In addition, induction of ATHB12 in the presence of cycloheximide increased the expression of several genes related to cell expansion, such as EXPANSIN A10 (EXPA10) and DWARF4 (DWF4). Our findings strongly suggest that ATHB12 acts as a positive regulator of endoreduplication and cell growth during leaf development. PMID:25187356

  19. Wind induced deformation and vibration of a Platanus acerifolia leaf

    NASA Astrophysics Data System (ADS)

    Shao, Chuan-Ping; Chen, Ye-Jun; Lin, Jian-Zhong

    2012-06-01

    Deformation and vibration of twig-connected single leaf in wind is investigated experimentally. Results show that the Reynolds number based on wind speed and length of leaf blade is a key parameter to the aerodynamic problem. In case the front surface facing the wind and with an increase of Reynolds number, the leaf experiences static deformation, large amplitude and low frequency sway, reconfiguration to delta wing shape, flapping of tips, high frequency vibration of whole leaf blade, recovery of delta wing shape, and twig-leaf coupling vibration. Abrupt changes from one state to another occur at critical Reynolds numbers. In case the back surface facing the wind, the large amplitude and low frequency sway does not occur, the recovered delta wing shape is replaced by a conic shape, and the critical Reynolds numbers of vibrations are higher than the ones corresponding to the case with the front surface facing the wind. A pair of ram-horn vortex is observed behind the delta wing shaped leaf. A single vortex is found downstream of the conic shaped leaf. A lift is induced by the vortex, and this lift helps leaf to adjust position and posture, stabilize blade distortion and reduce drag and vibration.

  20. Elm Leaf Beetle 

    E-print Network

    Patrick, Carl D.

    2002-05-22

    stream_source_info pdf_1591.pdf.txt stream_content_type text/plain stream_size 5918 Content-Encoding UTF-8 stream_name pdf_1591.pdf.txt Content-Type text/plain; charset=UTF-8 Elm Leaf Beetles L-1812 5-02 Carl D. Patrick... overwintering sites. *Extension Entomologist, The Texas A&M University System. Elm leaf beetle adult. Damage Elm leaf beetles feed exclusively on foliage. Adult feeding causes small, circular holes in leaves. Larval feeding removes most of the green material...

  1. Plant stem cell maintenance involves direct transcriptional repression of differentiation program.

    PubMed

    Yadav, Ram Kishor; Perales, Mariano; Gruel, Jérémy; Ohno, Carolyn; Heisler, Marcus; Girke, Thomas; Jönsson, Henrik; Reddy, G Venugopala

    2013-01-01

    In animal systems, master regulatory transcription factors (TFs) mediate stem cell maintenance through a direct transcriptional repression of differentiation promoting TFs. Whether similar mechanisms operate in plants is not known. In plants, shoot apical meristems serve as reservoirs of stem cells that provide cells for all above ground organs. WUSCHEL, a homeodomain TF produced in cells of the niche, migrates into adjacent cells where it specifies stem cells. Through high-resolution genomic analysis, we show that WUSCHEL represses a large number of genes that are expressed in differentiating cells including a group of differentiation promoting TFs involved in leaf development. We show that WUS directly binds to the regulatory regions of differentiation promoting TFs; KANADI1, KANADI2, ASYMMETRICLEAVES2 and YABBY3 to repress their expression. Predictions from a computational model, supported by live imaging, reveal that WUS-mediated repression prevents premature differentiation of stem cell progenitors, being part of a minimal regulatory network for meristem maintenance. Our work shows that direct transcriptional repression of differentiation promoting TFs is an evolutionarily conserved logic for stem cell regulation. PMID:23549482

  2. Excising the Root from STEM

    ERIC Educational Resources Information Center

    Lock, Roger

    2009-01-01

    There are a number of well-intentioned STEM initiatives, some designed to improve the recruitment and retention of science teachers. Sometimes it appears that the initiators are remote from direct contact with the "grass roots" issues that feed the "stem" on which the blossoms of young enthusiastic recruits to the science teaching profession are…

  3. Relationships between leaf pigment content and spectral reflectance across a wide range of species, leaf structures and developmental stages

    Microsoft Academic Search

    Daniel A. Sims; John A. Gamon

    2002-01-01

    Leaf pigment content can provide valuable insight into the physiological performance of leaves. Measurement of spectral reflectance provides a fast, nondestructive method for pigment estimation. A large number of spectral indices have been developed for estimation of leaf pigment content. However, in most cases these indices have been tested for only one or at most a few related species and

  4. Human Embryonic Stem Cell Registry

    NSDL National Science Digital Library

    The National Institutes of Health (NIH) has recently released the Human Embryonic Stem Cell Registry in response to the President's announcement on August 9, 2001 to allow federal funds for stem cell research. The site lists the eleven laboratories or companies that meet the specific criteria for approved stem cell lines and explains the criteria themselves. The NIH gives the number of actual lines for each entity, the NIC and providers code for each, as well as contact information. The Website also provides links to those seeking additional information about NIH stem cell information, grants and funding opportunities, technology transfer issues, and further facts about the NIH.

  5. Electronic Leaf Project

    NSDL National Science Digital Library

    Carolyn Houston

    2000-05-01

    This article demonstrates the benefits of a direct application of technology into a science classroom by transferring a traditional activity, such as leaf identification, into an electronic format. The new dynamic medium possesses attributes that can enha

  6. Leaf Tissue Senescence

    PubMed Central

    Manos, Peter J.; Goldthwaite, Jonathan

    1975-01-01

    During winter, excised leaf tissue from Rumex obtusifolius degrades chlorophyll at twice the summer rate but the plant hormones, gibberellic acid and zeatin, inhibit the senescence rate by a constant percentage, regardless of season. PMID:16659225

  7. Leaf to Landscape

    Microsoft Academic Search

    Alessandro Cescatti; Ülo Niinemets

    \\u000a Temporal dynamics and structural complexity of plant canopies strongly affect light harvesting, generating variable spatio-temporal\\u000a distributions of the irradiance on leaf area (Baldocchi and Collineau 1994). Leaf light interception scales linearly with\\u000a incident irradiance, but plant photosynthesis and photomorphogenesis typically exhibit a saturating response to light. Because\\u000a of the inherent nonlinearity in light responses, estimates of the photosynthetic rate at

  8. A niche opportunity for stem cell therapeutics

    Microsoft Academic Search

    G B Adams; D T Scadden

    2008-01-01

    The success of hematopoietic stem cell (HSC)-based therapies relies on the ability of the stem cells to both engraft and self-renew sufficiently in the bone marrow microenvironment. Previous studies identified that a number of components of bone contribute to the regulation of HSCs indicating that they participate in a stem cell ‘niche’. This niche is a dynamic microenvironment that changes

  9. Volatile Oils from the Root, Stem and Leaves of Schefflera stellata (Gaertn.) Harms (Araliaceae): Chemical Characterization and Antimicrobial Activity

    Microsoft Academic Search

    Baby Sabulal; Varughese George; Nediyaparambu Sukumaran Pradeep; Mathew Dan

    2008-01-01

    Volatile oils from the roots, stem and leaves of Schefflera stellata (Gaertn.) Harms were isolated by hydrodistillation and characterized by analytical gas chromatography and gas chromatography-mass spectroscopy. Sixty-nine (98.3%), seventy-eight (97.9%) and sixty-seven (98.0%) constituents were identified from the root, stem and leaf oils, respectively. Sesquiterpene hydrocarbons were the most abundant compounds in the root (73.8%), stem (68.8%) and leaf

  10. FPT Algorithms and Kernels for the Directed k-Leaf Problem

    E-print Network

    Paris-Sud XI, Université de

    FPT Algorithms and Kernels for the Directed k-Leaf Problem Jean Daligault , Gregory Gutin , Eun-degree zero are leaves. In the Directed Max Leaf Problem, we wish to find the maximum number of leaves in an out-branching of a given digraph D (or, to report that D has no out-branching). In the Directed k-Leaf

  11. STEM Thinking!

    ERIC Educational Resources Information Center

    Reeve, Edward M.

    2015-01-01

    Science, Technology, Engineering, and Mathematics (STEM) is a term seen almost daily in the news. In 2009, President Obama launched the Educate to Innovate initiative to move American students from the middle to the top of the pack in science and math achievement over the next decade (The White House, n.d.). Learning about the attributes of STEM

  12. Stem Cells

    Microsoft Academic Search

    Gwen Lomberk

    2007-01-01

    In this issue, ‘Pancreatology and the Web’ focuses on stem cell research, one of the 21st century’s most exciting areas of science. Stem cell research has been advancing our knowledge about how an organism develops from a single cell and how healthy cells replace damaged cells in adult organisms. Although still in its infancy, this field also offers a revolutionary

  13. STEM At Work

    NSDL National Science Digital Library

    STEM (Science Technology Engineering & Math) at work, presented by the Florida Advanced Technological Education Center, includes a number of educational puzzles for use in the classroom. Puzzles include an energy audit exercise, measurement of air bag movement, and diesel fuel additive volatility.

  14. Application of leaf extract causes repetitive action potentials in Biophytum sensitivum

    Microsoft Academic Search

    Takao Sibaoka

    1997-01-01

    A wound stimulus evoked a number of repetivite action potentials in the leaf ofBiophytum sensitivum. When the cut end of a leaf was immersed in a leaf extract, the resulting repetitive action potentials continue for a long\\u000a time. These repetitive action potentials disappeared immediately when the leaf extract, which contains a proposed stimulant,\\u000a was removed and the cut end was

  15. Treatment of oral mucositis in hematologic patients undergoing autologous or allogeneic transplantation of peripheral blood stem cells: a prospective, randomized study with a mouthwash containing camelia sinensis leaf extract.

    PubMed

    Carulli, Giovanni; Rocco, Melania; Panichi, Alessia; Chios, Chiara Feira; Ciurli, Ester; Mannucci, Chiara; Sordi, Elisabetta; Caracciolo, Francesco; Papineschi, Federico; Benedetti, Edoardo; Petrini, Mario

    2013-01-25

    Oral mucositis is an important side effect of hematopoietic stem cell transplantation (HCST), mainly due to toxicity of conditioning regimens. It produces significant pain and morbidity. The present study reports a prospective, randomized, non-blinded study testing the efficacy of a new mouthwash, called Baxidil Onco(®) (Sanitas Farmaceutici Srl, Tortona, Italy) in 60 hematologic patients undergoing HCST (28 autologous, 32 allogeneic). Baxidil Onco(®), used three times a day from Day -1 to Day +30, in addition to standard prophylactic schedules, was administered to 14 patients undergoing autologous and 14 patients undergoing allogeneic HCST. The remaining 32 patients (14 autologous and 18 HCST) were treated only with standard prophylactic schedules and served as control. In our study, the overall incidence of oral mucositis, measured according to the World Health Organization 0-4 scale, was 50% in the Baxidl Onco(®) group versus 82% in the control group (P=0.022). In addition, a significant reduction in scale 2-4 oral mucositis was observed in the Baxidil Onco(®) group (25% vs 56.2%; P=0.0029). The results obtained indicate that incidence, severity and duration of oral mucositis induced by conditioning regimens for HCST can be significantly reduced by oral rinsing with Baxidil Onco(®), in addition to the standard prophylaxis scheme. Since Camelia Sinensin extract, which is used to produce green tea, is the main agent in this mouthwash, we hypothesize that the anti-oxidative properties of polyphenolic compounds of tea might exert protective effects on oral mucosa. PMID:23888242

  16. Treatment of Oral Mucositis in Hematologic Patients Undergoing Autologous or Allogeneic Transplantation of Peripheral Blood Stem Cells: a Prospective, Randomized Study with a Mouthwash Containing Camelia Sinensis Leaf Extract

    PubMed Central

    Carulli, Giovanni; Rocco, Melania; Panichi, Alessia; Chios, Chiara Feira; Ciurli, Ester; Mannucci, Chiara; Sordi, Elisabetta; Caracciolo, Francesco; Papineschi, Federico; Benedetti, Edoardo; Petrini, Mario

    2013-01-01

    Oral mucositis is an important side effect of hematopoietic stem cell transplantation (HCST), mainly due to toxicity of conditioning regimens. It produces significant pain and morbidity. The present study reports a prospective, randomized, non-blinded study testing the efficacy of a new mouthwash, called Baxidil Onco® (Sanitas Farmaceutici Srl, Tortona, Italy) in 60 hematologic patients undergoing HCST (28 autologous, 32 allogeneic). Baxidil Onco®, used three times a day from Day -1 to Day +30, in addition to standard prophylactic schedules, was administered to 14 patients undergoing autologous and 14 patients undergoing allogeneic HCST. The remaining 32 patients (14 autologous and 18 HCST) were treated only with standard prophylactic schedules and served as control. In our study, the overall incidence of oral mucositis, measured according to the World Health Organization 0-4 scale, was 50% in the Baxidl Onco® group versus 82% in the control group (P=0.022). In addition, a significant reduction in scale 2-4 oral mucositis was observed in the Baxidil Onco® group (25% vs 56.2%; P=0.0029). The results obtained indicate that incidence, severity and duration of oral mucositis induced by conditioning regimens for HCST can be significantly reduced by oral rinsing with Baxidil Onco®, in addition to the standard prophylaxis scheme. Since Camelia Sinensin extract, which is used to produce green tea, is the main agent in this mouthwash, we hypothesize that the anti-oxidative properties of polyphenolic compounds of tea might exert protective effects on oral mucosa. PMID:23888242

  17. Physics strategies for sparing neural stem cells during whole-brain radiation treatments

    SciTech Connect

    Kirby, Neil; Chuang, Cynthia; Pouliot, Jean; Hwang, Andrew; Barani, Igor J. [Department of Radiation Oncology, University of California San Francisco, San Francisco, California 94143-1708 (United States)

    2011-10-15

    Purpose: Currently, there are no successful long-term treatments or preventive strategies for radiation-induced cognitive impairments, and only a few possibilities have been suggested. One such approach involves reducing the dose to neural stem cell compartments (within and outside of the hippocampus) during whole-brain radiation treatments for brain metastases. This study investigates the fundamental physics issues associated with the sparing of neural stem cells during photon radiotherapy for brain metastases. Methods: Several factors influence the stem cell dose: intracranial scattering, collimator leakage, beam energy, and total number of beams. The relative importance of these factors is investigated through a set of radiation therapy plans, which are all variations of an initial 6 MV intensity-modulated radiation therapy (IMRT) plan designed to simultaneously deliver a whole-brain dose of 30 Gy and maximally reduce stem cell compartment dose. Additionally, an in-house leaf segmentation algorithm was developed that utilizes jaw motion to minimize the collimator leakage. Results: The plans are all normalized such that 50% of the PTV receives 30 Gy. For the initial 6 MV IMRT plan, 50% of the stem cells receive a dose greater than 6.3 Gy. Calculations indicate that 3.6 Gy of this dose originates from intracranial scattering. The jaw-tracking segmentation algorithm, used in conjunction with direct machine parameter optimization, reduces the 50% stem cell dose to 4.3 and 3.7 Gy for 6 and 10 MV treatment beams, respectively. Conclusions: Intracranial scattering alone is responsible for a large dose contribution to the stem cell compartment. It is, therefore, important to minimize other contributing factors, particularly the collimator leakage, to maximally reduce dose to these critical structures. The use of collimator jaw tracking in conjunction with modern collimators can minimize this leakage.

  18. Damped leaf flexure hinge

    NASA Astrophysics Data System (ADS)

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  19. Damped leaf flexure hinge.

    PubMed

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage. PMID:26026549

  20. BOREAS TE-9 NSA Leaf Chlorophyll Density

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Sy, Mikailou

    2000-01-01

    The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves in boreal forest tree species. These data were collected to help provide an explanation of potential seasonal and spatial changes of leaf pigment properties in boreal forest species at the NSA. At different dates (FFC-Winter, FFC-Thaw, IFC-1, IFC-2, and IMC-3), foliage samples were collected from the upper third of the canopy for five NSA sites (YJP, OJP, OBS, UBS, and OA) near Thompson, Manitoba. Subsamples of 100 needles for black spruce, 20 needles for jack pine, and single leaf for trembling aspen were cut into pieces and immersed in a 20-mL DMF aliquot in a Nalgene test tube. The extracted foliage materials were then oven-dried at 68 C for 48 hours and weighed. Extracted leaf dry weight was converted to a total leaf area basis to express the chlorophyll content in mg/sq cm of total leaf area. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  1. Hydraulic differences along the water transport system of South American Nothofagus species: do leaves protect the stem functionality?

    PubMed

    Bucci, Sandra J; Scholz, Fabian G; Campanello, Paula I; Montti, Lia; Jimenez-Castillo, Mylthon; Rockwell, Fulton A; Manna, Ludmila La; Guerra, Pedro; Bernal, Pablo Lopez; Troncoso, Oscar; Enricci, Juan; Holbrook, Michele N; Goldstein, Guillermo

    2012-07-01

    Hydraulic traits were studied for six Nothofagus species from South America (Argentina and Chile), and for three of these species two populations were studied. The main goal was to determine if properties of the water conductive pathway in stems and leaves are functionally coordinated and to assess if leaves are more vulnerable to cavitation than stems, consistent with the theory of hydraulic segmentation along the vascular system of trees in ecosystems subject to seasonal drought. Vulnerability to cavitation, hydraulic conductivity of stems and leaves, leaf water potential, wood density and leaf water relations were examined. Large variations in vulnerability to cavitation of stems and leaves were observed across populations and species, but leaves were consistently more vulnerable than stems. Water potential at 50% loss of maximum hydraulic efficiency (P(50)) ranged from -0.94 to -2.44 MPa in leaves and from -2.6 to -5.3 MPa in stems across species and populations. Populations in the driest sites had sapwood and leaves more vulnerable to cavitation than those grown in the wettest sites. Stronger diurnal down-regulation in leaf hydraulic conductance compared with stem hydraulic conductivity apparently has the function to slow down potential water loss in stems and protect stem hydraulics from cavitation. Species-specific differences in wood density and leaf hydraulic conductance (K(Leaf)) were observed. Both traits were functionally related: species with higher wood density had lower K(Leaf). Other stem and leaf hydraulic traits were functionally coordinated, resulting in Nothofagus species with an efficient delivery of water to the leaves. The integrity of the more expensive woody portion of the water transport pathway can thus be maintained at the expense of the replaceable portion (leaves) of the stem-leaf continuum under prolonged drought. Compensatory adjustments between hydraulic traits may help to decrease the rate of embolism formation in the trees more vulnerable to cavitation. PMID:22684354

  2. A high proportion of blue light increases the photosynthesis capacity and leaf formation rate of Rosa × hybrida but does not affect time to flower opening.

    PubMed

    Terfa, Meseret Tesema; Solhaug, Knut Asbjørn; Gislerød, Hans Ragnar; Olsen, Jorunn Elisabeth; Torre, Sissel

    2013-05-01

    Alterations in light quality affect plant morphogenesis and photosynthetic responses but the effects vary significantly between species. Roses exhibit an irradiance-dependent flowering control but knowledge on light quality responses is scarce. In this study we analyzed, the responses in morphology, photosynthesis and flowering of Rosa × hybrida to different blue (B) light proportions provided by light-emitting diodes (LED, high B 20%) and high pressure sodium (HPS, low B 5%) lamps. There was a strong morphological and growth effect of the light sources but no significant difference in total dry matter production and flowering. HPS-grown plants had significantly higher leaf area and plant height, yet a higher dry weight proportion was allocated to leaves than stems under LED. LED plants showed 20% higher photosynthetic capacity (Amax ) and higher levels of soluble carbohydrates. The increase in Amax correlated with an increase in leaf mass per unit leaf area, higher stomata conductance and CO2 exchange, total chlorophyll (Chl) content per area and Chl a/b ratio. LED-grown leaves also displayed a more sun-type leaf anatomy with more and longer palisade cells and a higher stomata frequency. Although floral initiation occurred at a higher leaf number in LED, the time to open flowers was the same under both light conditions. Thereby the study shows that a higher portion of B light is efficient in increasing photosynthesis performance per unit leaf area, enhancing growth and morphological changes in roses but does not affect the total Dry Matter (DM) production or time to open flower. PMID:23020549

  3. LEAF GUI: User Manual (Leaf Extraction and Analysis Framework Graphical User Interface)

    E-print Network

    Weitz, Joshua S.

    LEAF GUI: User Manual (Leaf Extraction and Analysis Framework Graphical User Interface) #12;LEAF GUI User Manual Price et al. Index How to cite the LEAF GUI.......................................................................................................................Page 4 Overview of the LEAF GUI layout

  4. [A inversion model for remote sensing of leaf water content based on the leaf optical property].

    PubMed

    Fang, Mei-hong; Ju, Wei-min

    2015-01-01

    Leaf water content is a fundamental physiological characteristic parameter of crops, and plays an important role in the study of the ecological environment. The aim of the work reported in this paper was to focus upon the retrieval of leaf water content from leaf-scale reflectance spectra by developing a physical inversion model based on the radiative transfer theory and wavelet analysis techniques. A continuous wavelet transform was performed on each of leaf component specific absorption coefficients to pick wavelet coefficients that were identified as highly sensitive to leaf water content and insensitive to other components. In the present study, for identifying the most appropriate wavelet, the six frequently used wavelet functions available within MATLAB were tested. Two biorl. 5 wavelet coefficients observed at the scale of 200 nm are provided with good performance, their wave-length positions are located at 1 405 and 1 488 nm, respectively. Two factors (? and ?) of the predictive theoretical models based on the biorl. 5 wavelet coefficients of the leaf-scale reflectance spectra were determined by leaf structure parameter N. We built a database composed of thousands of simulated leaf reflectance spectra with the PROSPECT model. The entire dataset was split into two parts, with 60% the calibration subset assigned to calibrating two factors (? and ?) of the predictive theoretical model. The remaining 40% the validation subset combined with the LOPEX93 experimental dataset used for validating the models. The results showed that the accuracy of the models compare to the statistical regression models derived from the traditional vegetation indices has improved with the highest predictive coefficient of determination (R2) of 0. 987, and the model becomes more robust. This study presented that wavelet analysis has the potential to capture much more of the information contained with reflectance spectra than previous analytical approaches which have tended to focus on using a small number of optimal wavebands while discarding the majority of the spectrum. PMID:25993842

  5. Leaf Area Adjustment As an Optimal Drought-Adaptation Strategy

    NASA Astrophysics Data System (ADS)

    Manzoni, S.; Beyer, F.; Thompson, S. E.; Vico, G.; Weih, M.

    2014-12-01

    Leaf phenology plays a major role in land-atmosphere mass and energy exchanges. Much work has focused on phenological responses to light and temperature, but less to leaf area changes during dry periods. Because the duration of droughts is expected to increase under future climates in seasonally-dry as well as mesic environments, it is crucial to (i) predict drought-related phenological changes and (ii) to develop physiologically-sound models of leaf area dynamics during dry periods. Several optimization criteria have been proposed to model leaf area adjustment as soil moisture decreases. Some theories are based on the plant carbon (C) balance, hypothesizing that leaf area will decline when instantaneous net photosynthetic rates become negative (equivalent to maximization of cumulative C gain). Other theories draw on hydraulic principles, suggesting that leaf area should adjust to either maintain a constant leaf water potential (isohydric behavior) or to avoid leaf water potentials with negative impacts on photosynthesis (i.e., minimization of water stress). Evergreen leaf phenology is considered as a control case. Merging these theories into a unified framework, we quantify the effect of phenological strategy and climate forcing on the net C gain over the entire growing season. By accounting for the C costs of leaf flushing and the gains stemming from leaf photosynthesis, this metric assesses the effectiveness of different phenological strategies, under different climatic scenarios. Evergreen species are favored only when the dry period is relatively short, as they can exploit most of the growing season, and only incur leaf maintenance costs during the short dry period. In contrast, deciduous species that lower maintenance costs by losing leaves are advantaged under drier climates. Moreover, among drought-deciduous species, isohydric behavior leads to lowest C gains. Losing leaves gradually so as to maintain a net C uptake equal to zero during the driest period in the growing season provides the highest gain. Since these strategies are all defined based on often-modeled quantities, they can be implemented in ecosystem models depending on plant functional type and climate.

  6. Recovery of diurnal depression of leaf hydraulic conductance in a subtropical woody bamboo species: embolism refilling by nocturnal root pressure.

    PubMed

    Yang, Shi-Jian; Zhang, Yong-Jiang; Sun, Mei; Goldstein, Guillermo; Cao, Kun-Fang

    2012-04-01

    Despite considerable investigations of diurnal water use characteristics in different plant functional groups, the research on daily water use strategies of woody bamboo grasses remains lacking. We studied the daily water use and gas exchange of Sinarundinaria nitida (Mitford) Nakai, an abundant subtropical bamboo species in Southwest China. We found that the stem relative water content (RWC) and stem hydraulic conductivity (K(s)) of this bamboo species did not decrease significantly during the day, whereas the leaf RWC and leaf hydraulic conductance (K(leaf)) showed a distinct decrease at midday, compared with the predawn values. Diurnal loss of K(leaf) was coupled with a midday decline in stomatal conductance (g(s)) and CO(2) assimilation. The positive root pressures in the different habitats were of sufficient magnitude to refill the embolisms in leaves. We concluded that (i) the studied bamboo species does not use stem water storage for daily transpiration; (ii) diurnal down-regulation in K(leaf) and gs has the function to slow down potential water loss in stems and protect the stem hydraulic pathway from cavitation; (iii) since K(leaf) did not recover during late afternoon, refilling of embolism in bamboo leaves probably fully depends on nocturnal root pressure. The embolism refilling mechanism by root pressure could be helpful for the growth and persistence of this woody monocot species. PMID:22499596

  7. Another call to increase STEM education

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2011-07-01

    As science, technology, engineering, and mathematics (STEM) education becomes increasingly important, U.S. students are lagging behind other nations on international assessments, according to a recent Trends in International Mathematics and Science study. A 22 June report from the U.S. National Research Council (NRC) calls for increasing the focus on STEM education in the United States. “To make progress in improving STEM education for all students, policy makers at the national, state, and local levels should elevate science to the same level of importance as reading and mathematics,” states the report, “Successful K-12 STEM Education: Identifying Effective Approaches in Science, Technology, Engineering, and Mathematics.” It outlines several goals: expand the number of students who pursue advanced degrees and careers in STEM fields; expand the STEM-capable workforce, while also broadening the participation of women and minorities; and increase STEM literacy for all students, whether or not they pursue STEM-related careers or additional study in those areas.

  8. Stomatal conductance and leaf water potential responses to hydraulic conductance variation in Pinus pinaster seedlings

    Microsoft Academic Search

    Francesco Ripullone; Maria Rosa Guerrieri; Angelo Nole’; Federico Magnani; Marco Borghetti

    2007-01-01

    In this study, tree hydraulic conductance (K\\u000a tree) was experimentally manipulated to study effects on short-term regulation of stomatal conductance (g\\u000a s), net photosynthesis (A) and bulk leaf water potential (?leaf) in well watered 5–6 years old and 1.2 m tall maritime pine seedlings (Pinus pinaster Ait.). K\\u000a tree was decreased by notching the stem and increased by progressively excising the root

  9. LSD: a leaf senescence database

    PubMed Central

    Liu, Xiaochuan; Li, Zhonghai; Jiang, Zhiqiang; Zhao, Yi; Peng, Jinying; Jin, Jinpu; Guo, Hongwei; Luo, Jingchu

    2011-01-01

    By broad literature survey, we have developed a leaf senescence database (LSD, http://www.eplantsenescence.org/) that contains a total of 1145 senescence associated genes (SAGs) from 21 species. These SAGs were retrieved based on genetic, genomic, proteomic, physiological or other experimental evidence, and were classified into different categories according to their functions in leaf senescence or morphological phenotypes when mutated. We made extensive annotations for these SAGs by both manual and computational approaches, and users can either browse or search the database to obtain information including literatures, mutants, phenotypes, expression profiles, miRNA interactions, orthologs in other plants and cross links to other databases. We have also integrated a bioinformatics analysis platform WebLab into LSD, which allows users to perform extensive sequence analysis of their interested SAGs. The SAG sequences in LSD can also be downloaded readily for bulk analysis. We believe that the LSD contains the largest number of SAGs to date and represents the most comprehensive and informative plant senescence-related database, which would facilitate the systems biology research and comparative studies on plant aging. PMID:21097471

  10. A model for leaf initiation

    PubMed Central

    Abraham-Shrauner, Barbara; Pickard, Barbara G

    2011-01-01

    A biophysical model is proposed for how leaf primordia are positioned on the shoot apical
    meristem in both spiral and whorl phyllotaxes. Primordia are initiated by signals that propagate
    in the epidermis in both azimuthal directions away from the cotyledons or the most recently
    specified primordia. The signals are linear waves as inferred from the spatial periodicity of the
    divergence angle and a temporal periodicity. The periods of the waves, which represent actively
    transported auxin, are much smaller than the plastochron interval. Where oppositely directed
    waves meet at one or more angular positions on the periphery of the generative circle, auxin
    concentration builds and as in most models this stimulates local movement of auxin to
    underlying cells, where it promotes polarized cell division and expansion. For higher order
    spirals the wave model requires asymmetric function of auxin transport; that is, opposite wave
    speeds differ. An algorithm for determination of the angular positions of leaves in common leaf
    phyllotaxic configurations is proposed. The number of turns in a pattern repeat, number of leaves
    per level and per pattern repeat, and divergence angle are related to speed of auxin transport and
    radius of the generative circle. The rule for composition of Fibonacci or Lucas numbers
    associated with some phyllotaxes is discussed. A subcellular model suggests how the shoot
    meristem might specify either symmetric or asymmetric transport of auxin away from the
    forming primordia that produce it. Biological tests that could make or break the mathematical
    and molecular hypotheses are proposed. PMID:22212121

  11. Leaf Hydraulics Lawren Sack1

    E-print Network

    Sack, Lawren

    Leaf Hydraulics Lawren Sack1 and N. Michele Holbrook2 1 Department of Botany, University of Hawai the leaf constitute a substantial (30%) part of the resistance to water flow through plants, and thus influence rates of transpiration and photosynthesis. Leaf hydraulic conductance (Kleaf) varies more than 65

  12. Linking xylem hydraulic conductivity and vulnerability to the leaf economics spectrum--a cross-species study of 39 evergreen and deciduous broadleaved subtropical tree species.

    PubMed

    Kröber, Wenzel; Zhang, Shouren; Ehmig, Merten; Bruelheide, Helge

    2014-01-01

    While the fundamental trade-off in leaf traits related to carbon capture as described by the leaf economics spectrum is well-established among plant species, the relationship of the leaf economics spectrum to stem hydraulics is much less known. Since carbon capture and transpiration are coupled, a close connection between leaf traits and stem hydraulics should be expected. We thus asked whether xylem traits that describe drought tolerance and vulnerability to cavitation are linked to particular leaf traits. We assessed xylem vulnerability, using the pressure sleeve technique, and anatomical xylem characteristics in 39 subtropical tree species grown under common garden conditions in the BEF-China experiment and tested for correlations with traits related to the leaf economics spectrum as well as to stomatal control, including maximum stomatal conductance, vapor pressure deficit at maximum stomatal conductance and vapor pressure deficit at which stomatal conductance is down-regulated. Our results revealed that specific xylem hydraulic conductivity and cavitation resistance were closely linked to traits represented in the leaf economic spectrum, in particular to leaf nitrogen concentration, as well as to log leaf area and leaf carbon to nitrogen ratio but not to any parameter of stomatal conductance. The study highlights the potential use of well-known leaf traits from the leaf economics spectrum to predict plant species' drought resistance. PMID:25423316

  13. Bacterial leaf spot

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bacterial leaf spot has been reported in Australia (Queensland), Egypt, El Salvador, India, Japan, Nicaragua, Sudan, and the United States (Florida, Iowa, Kansas, Maryland, and Wisconsin). It occasionally causes locally severe defoliation and post-emergence damping-off and stunting. The disease is...

  14. Leaf drop in evergreen Ceanothus velutinus as a means of reducing herbivory.

    PubMed

    Karban, Richard

    2008-09-01

    Conventional explanations for deciduousness do not include losses to herbivory. However, a recent explanation posits that deciduous leaf drop allows trees to reduce their herbivore loads and that this benefit of the deciduous habit may partly offset lost opportunities for photosynthesis. Much of the damage caused by chewing herbivores occurs early in the season when adult insects colonize as new leaves are expanding; trees without leaves from previous leaf flushes at this time are less attractive and suffer less cost of herbivory. I tested this hypothesis using Ceanothus velutinus, an evergreen shrub that shows considerable individual variation in leaf retention. Stems that held more leaves through winter experienced more chewing damage the following season. Stems with leaves experimentally removed through winter also were less likely to receive chewing damage the following season. At least some herbivores in this system make oviposition decisions before new leaves have expanded, and old leaves may provide cues about the suitability of the stem. Holding leaves through winter increased the likelihood of herbivory, and experimental protection from herbivores caused 60% greater inflorescence production compared to unprotected stems. However, the cost of leaf retention was more than offset by an overall benefit. Stems that were allowed to keep winter leaves produced larger new leaves in summer and expanded them more rapidly in the season than stems with winter leaves experimentally removed. As a result, stems with leaves through winter experienced higher survival, four times as many inflorescences, and 40 times as many fruits as shoots that were experimentally defoliated. Losses to herbivores may be an unappreciated cost of leaf retention, and cost-benefit models of deciduous and evergreen behavior should include these losses. PMID:18831166

  15. Adult skeletal muscle stem cells.

    PubMed

    Sambasivan, Ramkumar; Tajbakhsh, Shahragim

    2015-01-01

    Skeletal muscles in vertebrates have a phenomenal regenerative capacity. A muscle that has been crushed can regenerate fully both structurally and functionally within a month. Remarkably, efficient regeneration continues to occur following repeated injuries. Thousands of muscle precursor cells are needed to accomplish regeneration following acute injury. The differentiated muscle cells, the multinucleated contractile myofibers, are terminally withdrawn from mitosis. The source of the regenerative precursors is the skeletal muscle stem cells-the mononucleated cells closely associated with myofibers, which are known as satellite cells. Satellite cells are mitotically quiescent or slow-cycling, committed to myogenesis, but undifferentiated. Disruption of the niche after muscle damage results in their exit from quiescence and progression towards commitment. They eventually arrest proliferation, differentiate, and fuse to damaged myofibers or make de novo myofibers. Satellite cells are one of the well-studied adult tissue-specific stem cells and have served as an excellent model for investigating adult stem cells. They have also emerged as an important standard in the field of ageing and stem cells. Several recent reviews have highlighted the importance of these cells as a model to understand stem cell biology. This chapter begins with the discovery of satellite cells as skeletal muscle stem cells and their developmental origin. We discuss transcription factors and signalling cues governing stem cell function of satellite cells and heterogeneity in the satellite cell pool. Apart from satellite cells, a number of other stem cells have been shown to make muscle and are being considered as candidate stem cells for amelioration of muscle degenerative diseases. We discuss these "offbeat" muscle stem cells and their status as adult skeletal muscle stem cells vis-a-vis satellite cells. The ageing context is highlighted in the concluding section. PMID:25344672

  16. The hematopoietic stem cell number in the peripheral blood of pediatric recipients correlates with the outcome after living donor liver transplantation.

    PubMed

    Gautier, Sergey V; Shevchenko, Olga P; Tsirulnikova, Olga M; Kurabekova, Rivada M; Lugovskaya, Svetlana A; Naumova, Elena V; Tsirulnikova, Irina E; Dolgov, Vladimir V

    2015-08-01

    It has been proposed that circulating HSCs play a role in graft survival after liver transplantation. The aim was to analyze the relationship between the number of HSCs before and after LDLT and liver function, immune biomarkers, and clinical outcomes in pediatric patients. We studied 15 pairs of adult healthy liver donors and pediatric recipients with ESLD. The CD34/CD45+ cell number was measured in the blood via flow cytometry, and plasma levels of immune biomarkers - via ELISA. CD34/CD45+ cell number in the recipients decreased within the first week after LDLT. The cell number before LDLT was negatively correlated with the plasma levels of CRP and the development of graft dysfunction in the early post-transplant period. After LDLT, the CD34/CD45+ cell number was positively correlated with the pretransplant plasma level of sCD40L, a T-cell activation marker. In adult liver donors, the cell number did not change within the first week after liver resection and was lower than in pediatric recipients. The results suggest that in pediatric recipients, the HSC number may be associated with graft function and could be regarded as a potential predictor of the clinical outcome after LDLT. PMID:25951239

  17. Endometrial stem/progenitor cells.

    PubMed

    Maruyama, Tetsuo

    2014-09-01

    Human endometrium regenerates and regresses with each menstrual cycle under hormonal control throughout a woman's reproductive life. The cyclical regeneration and remodeling potentials allude to the existence of stem/progenitor cells in the endometrium. There is increasing evidence that human endometrium contains small numbers of stem-like cells capable of self-renewal, multiple differentiation and tissue reconstitution. Although the precise identity of endometrial stem/progenitor cells remains elusive, these cells are thought to play pivotal role(s) in the physiological remodeling and regeneration of the human endometrium and also in the pathogenesis of endometrium-associated diseases, such as endometriosis. PMID:25160689

  18. Understanding how the leaf physiology of mangrove plants differs from fresh water plants: a fundamental step to use cellulose as a proxy for sea level rise

    Microsoft Academic Search

    P. Ellsworth; L. O. Sternberg

    2010-01-01

    We studied the leaf water isotopic enrichment pattern of mangrove (halophytes) and hammock (glycophytes) plants as an attempt to explain why the delta18O of stem cellulose from mangrove and hammock species have no relationship with the delta18O of source water. A better understanding of leaf physiology of mangroves and its effect on the delta18O of stem cellulose is the first

  19. Perspectives and controversies in the field of stem cell research.

    PubMed

    Romano, Gaetano

    2006-09-01

    The fourth annual meeting of the International Society for Stem Cell Research focused on a number of pressing issues, including: (I) the need to better characterize the biology of stem cells; (II) the need to exploit and optimize the great therapeutic potential of stem cells in tissue regeneration; (III) ethical and safety considerations related to the use of human embryonic stem cells; (IV) the contribution of adult stem cells to carcinogenesis; (V) the need to investigate the biology of cancer stem cells. The purpose of this report is to summarize the current status of stem cell research, as surmised by the proceedings of this meeting. PMID:17080207

  20. Variable depth recursion algorithm for leaf sequencing

    SciTech Connect

    Siochi, R. Alfredo C. [Department of Radiation Oncology, University of Iowa, 200 Hawkins Street, Iowa City, Iowa 52240 (United States)

    2007-02-15

    The processes of extraction and sweep are basic segmentation steps that are used in leaf sequencing algorithms. A modified version of a commercial leaf sequencer changed the way that the extracts are selected and expanded the search space, but the modification maintained the basic search paradigm of evaluating multiple solutions, each one consisting of up to 12 extracts and a sweep sequence. While it generated the best solutions compared to other published algorithms, it used more computation time. A new, faster algorithm selects one extract at a time but calls itself as an evaluation function a user-specified number of times, after which it uses the bidirectional sweeping window algorithm as the final evaluation function. To achieve a performance comparable to that of the modified commercial leaf sequencer, 2-3 calls were needed, and in all test cases, there were only slight improvements beyond two calls. For the 13 clinical test maps, computation speeds improved by a factor between 12 and 43, depending on the constraints, namely the ability to interdigitate and the avoidance of the tongue-and-groove under dose. The new algorithm was compared to the original and modified versions of the commercial leaf sequencer. It was also compared to other published algorithms for 1400, random, 15x15, test maps with 3-16 intensity levels. In every single case the new algorithm provided the best solution.

  1. Leaf absorbance and photosynthesis

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

  2. Kernelization for Maximum Leaf Spanning Tree with Positive Vertex Weights

    Microsoft Academic Search

    Bart Jansen

    2010-01-01

    \\u000a In this paper we consider a natural generalization of the well-known Max Leaf Spanning Tree problem. In the generalized Weighted Max Leaf problem we get as input an undirected connected graph G?=?(V,E), a rational number k???1 and a weight function w: V ®<\\/font\\u000a> Q ³<\\/font\\u000a> 1w: V \\\\longmapsto Q_{\\\\geq 1} on the vertices, and are asked whether a spanning

  3. ETIOLOGY AND HOST RANGE OF A CLOSTEROVIRUS ASSOCIATED WITH PLUM BARK NECROSIS-STEM PITTING DISEASE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diseased plum (Prunus salicina) cv. Black Beaut trees developed stem gumming, severe bark necrosis, and stem pitting symptoms on the woody cylinder of the main trunk and scaffold branches. The sucker shoots of the peach (Prunus persica) cv. Nemaguard understocks exhibited oak-leaf patterns, but lack...

  4. Leaf surface and histological perturbations of leaves of Phaseolus vulgaris and Helianthus annuus after exposure to simulated acid rain

    Microsoft Academic Search

    Lance S. Evans; Nicholas F. Gmur; Filomena Da Costa

    1977-01-01

    Initial injury to adaxial leaf surfaces of Phaseolus vulgaris and Helianthus annuus occurred near trichomes and stomata after exposure to simulated sulfate acid rain. Lesion frequency was not correlated with density of either stomata or trichomes but was correlated with degree of leaf expansion. The number of lesions per unit area increased with total leaf area. Results suggest that characteristics

  5. Leaf-to-leaf distances in Catalan tree graphs

    E-print Network

    Andrew M. Goldsborough; Jonathan M. Fellows; Matthew Bates; S. Alex Rautu; George Rowlands; Rudolf A. Römer

    2015-03-02

    We study the average leaf-to-leaf path lengths on ordered Catalan tree graphs with $n$ nodes and show that these are equivalent to the average length of paths starting from the root node. We give an explicit analytic formula for the average leaf-to-leaf path length as a function of separation of the leaves and study its asymptotic properties. At the heart of our method is a strategy based on an abstract graph representation of generating functions which we hope can be useful also in other contexts.

  6. Cellulose Synthase-Like D1 Is Integral to Normal Cell Division, Expansion, and Leaf Development in Maize1[W][OA

    PubMed Central

    Hunter, Charles T.; Kirienko, Daniel Hill; Sylvester, Anne W.; Peter, Gary F.; McCarty, Donald R.; Koch, Karen E.

    2012-01-01

    The Cellulose Synthase-Like D (CslD) genes have important, although still poorly defined, roles in cell wall formation. Here, we show an unexpected involvement of CslD1 from maize (Zea mays) in cell division. Both division and expansion were altered in the narrow-organ and warty phenotypes of the csld1 mutants. Leaf width was reduced by 35%, due mainly to a 47% drop in the number of cell files across the blade. Width of other organs was also proportionally reduced. In leaf epidermis, the deficiency in lateral divisions was only partially compensated by a modest, uniform increase in cell width. Localized clusters of misdivided epidermal cells also led to the formation of warty lesions, with cell clusters bulging from the epidermal layer, and some cells expanding to volumes 75-fold greater than normal. The decreased cell divisions and localized epidermal expansions were not associated with detectable changes in the cell wall composition of csld1 leaf blades or epidermal peels, yet a greater abundance of thin, dense walls was indicated by high-resolution x-ray tomography of stems. Cell-level defects leading to wart formation were traced to sites of active cell division and expansion at the bases of leaf blades, where cytokinesis and cross-wall formation were disrupted. Flow cytometry confirmed a greater frequency of polyploid cells in basal zones of leaf blades, consistent with the disruption of cytokinesis and/or the cell cycle in csld1 mutants. Collectively, these data indicate a previously unrecognized role for CSLD activity in plant cell division, especially during early phases of cross-wall formation. PMID:22123901

  7. Stem cells, cancer, and cancer stem cells

    Microsoft Academic Search

    Tannishtha Reya; Sean J. Morrison; Michael F. Clarke; Irving L. Weissman

    2001-01-01

    Stem cell biology has come of age. Unequivocal proof that stem cells exist in the haematopoietic system has given way to the prospective isolation of several tissue-specific stem and progenitor cells, the initial delineation of their properties and expressed genetic programmes, and the beginnings of their utility in regenerative medicine. Perhaps the most important and useful property of stem cells

  8. Cell Stem Cell Stem Cell States, Fates,

    E-print Network

    Peterson, Carsten

    and Stem Cell Research, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, Lund SE-223 62, Sweden 4Lund Strategic Research Center for Stem Cell Biology and Cell Therapy, LundCell Stem Cell Review Stem Cell States, Fates, and the Rules of Attraction Tariq Enver,1 Martin

  9. Stemming the Stem Cell Setback

    Microsoft Academic Search

    Patrick J. Fleis

    2003-01-01

    This Comment highlights the recent federal funding setbacks in the biotechnology industry and considers the resulting challenges to future research collaboration. After providing a historical background to stem cell technology, Mr. Fleis examines the passionately opposed public responses to the technology's use of embryos and to its future applications. Fleis continues by noting past legislative initiatives that have accelerated the

  10. Adult Stem and Progenitor Cells

    NASA Astrophysics Data System (ADS)

    Geraerts, Martine; Verfaillie, Catherine M.

    The discovery of adult stem cells in most adult tissues is the basis of a number of clinical studies that are carried out, with therapeutic use of hematopoietic stem cells as a prime example. Intense scientific debate is still ongoing as to whether adult stem cells may have a greater plasticity than previously thought. Although cells with some features of embryonic stem cells that, among others, express Oct4, Nanog and SSEA1 are isolated from fresh tissue, it is not clear if the greater differentiation potential is acquired during cell culture. Moreover, adult more pluripotent cells do not have all pluripotent characteristics typical for embryonic stem cells. Recently, some elegant studies were published in which adult cells could be completely reprogrammed to embryonic stem cell-like cells by overexpression of some key transcription factors for pluripotency (Oct4, Sox2, Klf4 and c-Myc). It will be interesting for the future to investigate the exact mechanisms underlying this reprogramming and whether similar transcription factor pathways are present and/or can be activated in adult more pluripotent stem cells.

  11. WRKY13 acts in stem development in Arabidopsis thaliana.

    PubMed

    Li, Wei; Tian, Zhaoxia; Yu, Diqiu

    2015-07-01

    Stems are important for plants to grow erectly. In stems, sclerenchyma cells must develop secondary cell walls to provide plants with physical support. The secondary cell walls are mainly composed of lignin, xylan and cellulose. Deficiency of overall stem development could cause weakened stems. Here we prove that WRKY13 acts in stem development. The wrky13 mutants take on a weaker stem phenotype. The number of sclerenchyma cells, stem diameter and the number of vascular bundles were reduced in wrky13 mutants. Lignin-synthesis-related genes were repressed in wrky13 mutants. Chromatin immunoprecipitation assays proved that WRKY13 could directly bind to the promoter of NST2. Taken together, we proposed that WRKY13 affected the overall development of stem. Identification of the role of WRKY13 may help to resolve agricultural problems caused by weaker stems. PMID:26025534

  12. Effect of CO sub 2 enriched air on the kinetics of leaf expansion. [Pisum sativa; Glycine max

    SciTech Connect

    Potter, J.R. (Dept. of Agriculture, Corvallis, OR (United States))

    1991-05-01

    Vegetative plants of Pisum sativum (pea) and Glycine max (soybean) were transferred from 350 to 1,200 ppm CO{sub 2} when they had one (pea) or two (soybean) mature leaves and several developing leaves. Controls were kept at 350 ppm. For pea, high CO{sub 2} for 8 days increased dry mass of root, stem, and leaf fractions by 30-50%. Leaf dry mass increase was due primarily to carbohydrate, particularly starch. Dawn levels of starch increased 10-fold within 1 day at high CO{sub 2} and 20-fold at 2 days. At 2 days after transfer leaf starch levels were 1.0 mg cm{sup {minus}2} of leaf area or nearly 30% of leaf dry weight. Soybean data are less complete, but 10 days at high CO{sub 2} increased leaf + stem dry mass by 50% and leaf weight per unit area increased by 14 and 48% at dawn within 1 and 2 days, respectively, at high CO{sub 2}. However 8-10 days at high CO{sub 2} increased total leaf area only slightly (about 15%) for both species, with all the leaf area increase occurring at nodes that were nearly microscopic at the time of transfer. For soybean, most of the increased leaf area due to high CO{sub 2} was from lateral bud break despite a high CO{sub 2} did not stimulated more leaves per plant. Apparently, extra photosynthate had a delayed effect on leaf expansion and did not increase nodes along the main axis. Leaf expansion under high CO{sub 2} was not limited by photosynthate.

  13. Pluripotent stem cells and their niches

    Microsoft Academic Search

    M. William Lensch; Laurence Daheron; Thorsten M. Schlaeger

    2006-01-01

    The ability of stem cells to self-renew and to replace mature cells is fundamental to ontogeny and tissue regeneration. Stem\\u000a cells of the adult organism can be categorized as mono-, bi-, or multipotent, based on the number of mature cell types to\\u000a which they can give rise. In contrast, pluripotent stem cells of the early embryo have the ability to

  14. Lessons from development: A role for asymmetric stem cell division in cancer

    Microsoft Academic Search

    Anne E. Powell; Chia-Yi Shung; Katherine W. Saylor; Karin A. Müllendorf; Joseph B. Weiss; Melissa H. Wong

    2010-01-01

    Asymmetric stem cell division has emerged as a major regulatory mechanism for physiologic control of stem cell numbers. Reinvigoration of the cancer stem cell theory suggests that tumorigenesis may be regulated by maintaining the balance between asymmetric and symmetric cell division. Therefore, mutations affecting this balance could result in aberrant expansion of stem cells. Although a number of molecules have

  15. Controlled differentiation of stem cells?

    PubMed Central

    Hwang, Nathaniel S.; Varghese, Shyni; Elisseeff, Jennifer

    2009-01-01

    The extracellular microenvironment plays a significant role in controlling cellular behavior. Identification of appropriate biomaterials that support cellular attachment, proliferation and, most importantly in the case of human embryonic stem cells, lineage-specific differentiation is critical for tissue engineering and cellular therapy. In addition to growth factors and morphogenetic factors known to induce lineage commitment of stem cells, a number of scaffolding materials, including synthetic and naturally-derived biomaterials, have been utilized in tissue engineering approaches to direct differentiation. This review focuses on recent emerging findings and well-characterized differentiation models of human embryonic stem cells. Additionally, we also discuss about various strategies that have been used in stem cell expansion. PMID:18006108

  16. Strigolactone signaling regulates rice leaf senescence in response to a phosphate deficiency.

    PubMed

    Yamada, Yusuke; Furusawa, Soya; Nagasaka, Seiji; Shimomura, Koichiro; Yamaguchi, Shinjiro; Umehara, Mikihisa

    2014-08-01

    Strigolactones (SLs) act as plant hormones that inhibit shoot branching and stimulate secondary growth of the stem, primary root growth, and root hair elongation. In the moss Physcomitrella patens, SLs regulate branching of chloronemata and colony extension. In addition, SL-deficient and SL-insensitive mutants show delayed leaf senescence. To explore the effects of SLs on leaf senescence in rice (Oryza sativa L.), we treated leaf segments of rice dwarf mutants with a synthetic SL analogue, GR24, and evaluated their chlorophyll contents, ion leakage, and expression levels of senescence-associated genes. Exogenously applied GR24 restored normal leaf senescence in SL-deficient mutants, but not in SL-insensitive mutants. Most plants highly produce endogenous SLs in response to phosphate deficiency. Thus, we evaluated effects of GR24 under phosphate deficiency. Chlorophyll levels did not differ of in the wild-type between the sufficient and deficient phosphate conditions, but increased in the SL-deficient mutants under phosphate deficiency, leading in the strong promotion of leaf senescence by GR24 treatment. These results indicate that the mutants exhibited increased responsiveness to GR24 under phosphate deficiency. In addition, GR24 accelerated leaf senescence in the intact SL-deficient mutants under phosphate deficiency as well as dark-induced leaf senescence. The effects of GR24 were stronger in d10 compared to d17. Based on these results, we suggest that SLs regulate leaf senescence in response to phosphate deficiency. PMID:24888863

  17. COMMON SOYBEAN INSECTS 1. BEAN LEAF BEETLE, Cerotoma trifurcata (Forster). The adult

    E-print Network

    Ginzel, Matthew

    feeds on stems of soybean seedlings and also eats holes in leaves and pods. The slender white larvae eat away the leaf surface, giv ing foliage a lacy appearance. The beetles are about 1/4 inch long emerge in early July, one of their favorite food plants is soybeans. They collect on upper leaves and eat

  18. Leaf Area and Above and Belowground Growth Responses of Loblolly Pine to Nutrient and Water Additions

    Microsoft Academic Search

    Timothy J. Albaugh; H. Lee Allen; Phillip M. Dougherty; Lance W. Kress; John S. King

    1998-01-01

    A 2 x 2 nutrient and water factorial experiment with four replications was installed in an 8-yr-old stand of Ioblolly pine (Pinus taeda L.) growing on an infertile, excessively drained sandy site in Scotland County, North Carolina. After the fourth year of treatment, estimated stem volume increment, total biomass production, and peak leaf area index (LAI) increased 152%, 99%, and

  19. Shoot Meristem Function and Leaf Polarity: The Role of Class III HD–ZIP Genes

    Microsoft Academic Search

    Mary E. Byrne

    2006-01-01

    The shoot apical meristem comprises an organized cluster of cells with a central region population of self-maintaining stem cells providing peripheral region cells that are recruited to form differentiated lateral organs. Leaves, the principal lateral organ of the shoot, develop as polar structures typically with distinct dorsoventrality. Interdependent interactions between the meristem and developing leaf provide essential cues that serve

  20. Combining Leaf Salient Points and Leaf Contour Descriptions for Plant Species Recognition

    E-print Network

    Verroust-Blondet, Anne

    Combining Leaf Salient Points and Leaf Contour Descriptions for Plant Species Recognition Sofiene for plant species recognition, based on the leaf observation. We consider two sources of information: the leaf margin and the leaf salient points. For the leaf shape description, we investigate the shape

  1. BOREAS TE-5 Leaf Carbon Isotope Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

    2000-01-01

    The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. This documentation describes leaf carbon isotope data that were collected in 1993 and 1994 at the NSA and SSA OJP sites, the SSA OBS site, and the NSA UBS site. In addition, leaf carbon isotope data were collected in 1994 only at the NSA and SSA OA sites. These data was collected to provide seasonal integrated physiological information for 10 to 15 common species at these 6 BOREAS sites. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  2. Alterations in soybean leaf development and photosynthesis in a CO sub 2 -enriched atmosphere

    SciTech Connect

    Cure, J.D. (Duke Univ., Durham, NC (USA)); Rufty, T.W. Jr.; Israel, D.W. (North Carolina State Univ., Raleigh (USA))

    1989-12-01

    This study was conducted to characterize changes in the canopy photosynthetic leaf area of developing soybean (Glycine max (L.) Merr. cv Lee) exposed to a CO{sub 2}-enriched atmosphere. Young, vegetative plants were exposed to 350 or 700 {mu}L L{sup {minus}1} CO{sub 2} for 15 d. Plant dry mass and total leaf area were greater in the CO{sub 2}-enriched environment. Emergence and expansion rates of main stem leaves increased at high CO{sub 2}, but the areas of individual leaves at full expansion were affected very little (5%-10% greater than controls). More rapid leaf expansion rates occurred in the light and dark. Under CO{sub 2}-enriched conditions, the net CO{sub 2} exchange rates of all leaves on the main stem were higher before and after full expansion. Stomatal conductance was lower in high CO{sub 2} only after leaves approached full expansion. Leaf development on the lateral branches also was increased at high CO{sub 2}, accounting for 40% of the total increase in leaf area by the end of the experiment. The authors conclude that more rapid rates of leaf development under CO{sub 2} enrichment likely resulted from increased photosynthesis rates and that both direct and indirect effects were involved.

  3. Education research Making STEM

    E-print Network

    Rambaut, Andrew

    Education research Working Together: Making STEM happen in secondary schools #12;STEM education | 1 The Camden School STEM Initiative Interdisciplinary STEM education stimulates interest in science, technology on the combined application of all four subjects. Students of Maria Fidelis consider how to use their STEM garden

  4. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture...INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

  5. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2 2014-01-01 2014-01-01 false Leaf structure. 29.6023 Section 29.6023...INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its porosity. The degrees...

  6. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  7. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  8. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture...INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

  9. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  10. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture...INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

  11. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2 2012-01-01 2012-01-01 false Leaf structure. 29.6023 Section 29.6023...INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its porosity. The degrees...

  12. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2 2013-01-01 2013-01-01 false Leaf structure. 29.6023 Section 29.6023...INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its porosity. The degrees...

  13. 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

  14. Change in hydraulic properties and leaf traits in a tall rainforest tree species subjected to long-term throughfall exclusion in the perhumid tropics

    NASA Astrophysics Data System (ADS)

    Schuldt, B.; Leuschner, C.; Horna, V.; Moser, G.; Köhler, M.; van Straaten, O.; Barus, H.

    2011-08-01

    A large-scale replicated throughfall exclusion experiment was conducted in a pre-montane perhumid rainforest in Sulawesi (Indonesia) exposing the trees for two years to pronounced soil desiccation. The lack of regularly occurring dry periods and shallow rooting patterns distinguish this experiment from similar experiments conducted in the Amazonian rainforest. We tested the hypotheses that a tree's sun canopy is more affected by soil drought than its shade crown, making tall trees particularly vulnerable even under a perhumid climate, and that extended drought periods stimulate an acclimation in the hydraulic system of the sun canopy. In the abundant and tall tree species Castanopsis acuminatissima (Fagaceae), we compared 31 morphological, anatomical, hydraulic and chemical variables of leaves, branches and the stem together with stem diameter growth between drought and control plots. There was no evidence of canopy dieback. However, the drought treatment led to a 30 % reduction in sapwood-specific hydraulic conductivity of sun canopy branches, possibly caused by the formation of smaller vessels and/or vessel filling by tyloses. Drought caused an increase in leaf size, but a decrease in leaf number, and a reduction in foliar calcium content. The ?13C and ?18O signatures of sun canopy leaves gave no indication of a permanent down-regulation of stomatal conductance during the drought, indicating that pre-senescent leaf shedding may have improved the water status of the remaining leaves. Annual stem diameter growth decreased during the drought, while the density of wood in the recently produced xylem increased in both the stem and sun canopy branches (marginally significant). The sun canopy showed a more pronounced drought response than the shade crown indicating that tall trees with a large sun canopy are more vulnerable to drought stress. We conclude that the extended drought prompted a number of medium- to long-term responses in the leaves, branches and the trunk, which may have reduced drought susceptibility. However, unlike a natural drought, our drought simulation experiment was carried out under conditions of high humidity, which may have dampened drought induced damages.

  15. Self-shading, carbon gain and leaf dynamics: a test of alternative optimality models

    Microsoft Academic Search

    David Ackerly

    1999-01-01

    A simple model of shoot-level carbon gain is presented addressing the optimal number and life span of leaves in relation\\u000a to alternative optimality criteria: (1) maximizing carbon export from the shoot, or (2) maximizing the rate of leaf production\\u000a at the shoot tip. Additionally, the processes that cause declining assimilation with leaf age are considered in relation to\\u000a (1) leaf

  16. The artificial leaf.

    PubMed

    Nocera, Daniel G

    2012-05-15

    To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a corner-sharing, head-to-tail dimer. The ability to perform the oxygen-evolving reaction in water at neutral or near-neutral conditions has several consequences for the construction of the artificial leaf. The NiMoZn alloy may be used in place of Pt to generate hydrogen. To stabilize silicon in water, its surface is coated with a conducting metal oxide onto which the Co-OEC may be deposited. The net result is that immersing a triple-junction Si wafer coated with NiMoZn and Co-OEC in water and holding it up to sunlight can effect direct solar energy conversion via water splitting. By constructing a simple, stand-alone device composed of earth-abundant materials, the artificial leaf provides a means for an inexpensive and highly distributed solar-to-fuels system that employs low-cost systems engineering and manufacturing. Through this type of system, solar energy can become a viable energy supply to those in the non-legacy world. PMID:22475039

  17. The worldwide leaf economics spectrum

    Microsoft Academic Search

    Ian J. Wright; Peter B. Reich; Mark Westoby; David D. Ackerly; Zdravko Baruch; Frans Bongers; Jeannine Cavender-Bares; Terry Chapin; Johannes H. C. Cornelissen; Matthias Diemer; Jaume Flexas; Eric Garnier; Philip K. Groom; Javier Gulias; Kouki Hikosaka; Byron B. Lamont; Tali Lee; William Lee; Christopher Lusk; Jeremy J. Midgley; Marie-Laure Navas; Ülo Niinemets; Jacek Oleksyn; Noriyuki Osada; Pieter Poot; Lynda Prior; Vladimir I. Pyankov; Catherine Roumet; Sean C. Thomas; Mark G. Tjoelker; Erik J. Veneklaas; Rafael Villar

    2004-01-01

    Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional

  18. Effects of Roads on Castanopsis carlesii Seedlings and Their Leaf Herbivory in a Subtropical Forest in China

    PubMed Central

    Dai, Xiao-Hua; Xu, Jia-Sheng; Cai, Lu-Rong

    2014-01-01

    The effects of a forest road on Castanopsis carlesii (Hemsley) Hayata (Fagales: Fagaceae) seedlings and their leaf herbivory were investigated in a subtropical forest at Jiulianshan National Nature Reserve, Jiangxi, China. A total of 1124 seedlings, 33949 leaves, 468 leaf mines, and 205 leaf galls were found. Generally, individual numbers, tree heights, and leaf numbers of C. carlesii seedlings became lower with increasing distances from the road. These results might indicate that old seedlings were fewer and survival rate of seedlings was lower in forest interiors. Leaf miners preferred the seedlings close to the forest road, while leaf gallers preferred the seedlings about 2 m from the road. Species diversity of leaf miners was higher in the forest interior area, while species diversity of leaf gallers was higher near the road. However, both leaf miners and leaf gallers decreased in general from the road to the interior forest. There were interspecific differences in the effects of roads on leaf miner species and leaf galler species. The effects of the road on seedlings and insects could be explained by varying microhabitat conditions and different ecological strategies. PMID:25373164

  19. Genetic Dissection of Leaf Development in Brassica rapa Using a Genetical Genomics Approach1[W

    PubMed Central

    Xiao, Dong; Wang, Huange; Basnet, Ram Kumar; Zhao, Jianjun; Lin, Ke; Hou, Xilin; Bonnema, Guusje

    2014-01-01

    The paleohexaploid crop Brassica rapa harbors an enormous reservoir of morphological variation, encompassing leafy vegetables, vegetable and fodder turnips (Brassica rapa, ssp. campestris), and oil crops, with different crops having very different leaf morphologies. In the triplicated B. rapa genome, many genes have multiple paralogs that may be regulated differentially and contribute to phenotypic variation. Using a genetical genomics approach, phenotypic data from a segregating doubled haploid population derived from a cross between cultivar Yellow sarson (oil type) and cultivar Pak choi (vegetable type) were used to identify loci controlling leaf development. Twenty-five colocalized phenotypic quantitative trait loci (QTLs) contributing to natural variation for leaf morphological traits, leaf number, plant architecture, and flowering time were identified. Genetic analysis showed that four colocalized phenotypic QTLs colocalized with flowering time and leaf trait candidate genes, with their cis-expression QTLs and cis- or trans-expression QTLs for homologs of genes playing a role in leaf development in Arabidopsis (Arabidopsis thaliana). The leaf gene BRASSICA RAPA KIP-RELATED PROTEIN2_A03 colocalized with QTLs for leaf shape and plant height; BRASSICA RAPA ERECTA_A09 colocalized with QTLs for leaf color and leaf shape; BRASSICA RAPA LONGIFOLIA1_A10 colocalized with QTLs for leaf size, leaf color, plant branching, and flowering time; while the major flowering time gene, BRASSICA RAPA FLOWERING LOCUS C_A02, colocalized with QTLs explaining variation in flowering time, plant architectural traits, and leaf size. Colocalization of these QTLs points to pleiotropic regulation of leaf development and plant architectural traits in B. rapa. PMID:24394778

  20. Stem cell niches

    Microsoft Academic Search

    V. V. Terskikh; A. V. Vasiliev; E. A. Vorotelyak

    2007-01-01

    The nature of the stem cell niche and its interaction with stem cells is one of fundamental problems in the biology of stem\\u000a cells. Stem cell niches are formed during ontogeny. A niche can remain vacant and exist independently of stem cells; however,\\u000a stem cell self-renewal cannot be maintained for long periods outside of the niche except for particular conditions,

  1. STEM: Science Technology Engineering Mathematics. State-Level Analysis

    ERIC Educational Resources Information Center

    Carnevale, Anthony P.; Smith, Nicole; Melton, Michelle

    2011-01-01

    The science, technology, engineering, and mathematics (STEM) state-level analysis provides policymakers, educators, state government officials, and others with details on the projections of STEM jobs through 2018. This report delivers a state-by-state snapshot of the demand for STEM jobs, including: (1) The number of forecast net new and…

  2. Final report on the safety assessment of AloeAndongensis Extract, Aloe Andongensis Leaf Juice,aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice,aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract.

    PubMed

    2007-01-01

    Plant materials derived from the Aloe plant are used as cosmetic ingredients, including Aloe Andongensis Extract, Aloe Andongensis Leaf Juice, Aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice, Aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract. These ingredients function primarily as skin-conditioning agents and are included in cosmetics only at low concentrations. The Aloe leaf consists of the pericyclic cells, found just below the plant's skin, and the inner central area of the leaf, i.e., the gel, which is used for cosmetic products. The pericyclic cells produce a bitter, yellow latex containing a number of anthraquinones, phototoxic compounds that are also gastrointestinal irritants responsible for cathartic effects. The gel contains polysaccharides, which can be acetylated, partially acetylated, or not acetylated. An industry established limit for anthraquinones in aloe-derived material for nonmedicinal use is 50 ppm or lower. Aloe-derived ingredients are used in a wide variety of cosmetic product types at concentrations of raw material that are 0.1% or less, although can be as high as 20%. The concentration of Aloe in the raw material also may vary from 100% to a low of 0.0005%. Oral administration of various anthraquinone components results in a rise in their blood concentrations, wide systemic distribution, accumulation in the liver and kidneys, and excretion in urine and feces; polysaccharide components are distributed systemically and metabolized into smaller molecules. aloe-derived material has fungicidal, antimicrobial, and antiviral activities, and has been effective in wound healing and infection treatment in animals. Aloe barbadensis (also known as Aloe vera)-derived ingredients were not toxic in acute oral studies using mice and rats. In parenteral studies, the LD(50) using mice was > 200 mg/kg, rats was > 50 mg/kg, and using dogs was > 50 mg/kg. In intravenous studies the LD(50) using mice was > 80 mg/kg, rats was > 15 mg/kg, and dogs was > 10 mg/kg. The 14-day no observed effect level (NOEL) for the Aloe polysaccharide, acemannan, in the diet of Sprague-Dawley rats, was 50,000 ppm or 4.1 to 4.6 g/kg day(-1). In a 3-month study using mice, Aloe vera (extracted in ethanol) given orally in drinking water at 100 mg/kg produced reproductive toxicity, inflammation, and mortality above that seen in control animals. Aloe vera extracted in methanol and given to mice at 100 mg/kg in drinking water for 3 months caused significant sperm damage compared to controls. Aloe barbadensis extracted with water and given to pregnant Charles Foster albino rats on gestational days (GDs) 0 through 9 was an abortifacient and produced skeletal abnormalities. Both negative and positive results were found in bacterial and mammalian cell genotoxicity assays using Aloe barbadensis-derived material, Aloe Ferox-derived material, and various anthraquinones derived from Aloe. Aloin (an anthraquinone) did not produce tumors when included in the feed of mice for 20 weeks, nor did aloin increase the incidence of colorectal tumors induced with 1,2-dimethylhydrazine. Aloe-emodin (an anthraquinone) given to mice in which tumor cells had been injected inhibited growth of malignant tumors. Other animal data also suggest that components of Aloe inhibit tumor growth and improve survival. Various in vitro assays also demonstrated anticarcinogenic activity of aloe-emodin. Diarrhea was the only adverse effect of note with the use of Aloe-derived ingredients to treat asthma, ischemic heart disease, diabetes, ulcers, skin disease, and cancer. Case reports include acute eczema, contact urticaria, and dermatitis in individuals who applied Aloe-derived ingredients topically. The Cosmetic Ingredient Review Expert Panel concluded that anthraquinone levels in the several Aloe Barbaden

  3. Isolation of 6-hydroxykynurenic acid from the tobacco leaf

    PubMed Central

    Macnicol, P. K.

    1968-01-01

    1. 6-Hydroxykynurenic acid (4,6-dihydroxyquinoline-2-carboxylic acid, 6-HKA) was isolated in crystalline form from both green and cured tobacco leaves. 2. A method for the determination of 6-HKA by paper chromatography and fluorimetry is described. 3. The content of 6-HKA in the flowers, stem and roots of the tobacco plant was much lower than that in the leaf. 4. The 6-HKA content increased throughout leaf development and senescence. 5. 6-HKA was detected in the leaves of plants representing 11 out of 27 families sampled. 6. 6-HKA was found to be devoid of antibacterial and antifungal activity, and was inactive in the Avena-coleoptile and cress-seed-germination tests. 7. The presence of 6-HKA is taken as evidence in plants of the tryptophan-catabolic pathway already known in mammals and micro-organisms. PMID:5665251

  4. Relationships between hydraulic architecture and leaf photosynthetic capacity in nitrogen-fertilized Eucalyptus grandis trees.

    PubMed

    Clearwater, M J; Meinzer, F C

    2001-07-01

    We compared the effects of nitrogen fertilization on shoot hydraulic architecture and leaf photosynthetic properties of Eucalyptus grandis Hill ex Maiden trees in Hawaii. It was hypothesized that water transport capacity would adjust to nutrient availability, with leaf specific hydraulic conductivity (kl) increasing in fertilized trees in coordination with higher photosynthetic capacity per unit leaf area. Trees were grown from seedlings in the field for 10 months at four rates of nitrogen (N) fertilization between 0 and 336 kg x ha(-1). Leaf water potentials, photosynthetic capacity and kl were measured before whole shoots were harvested to determine total growth, leaf area and sapwood density. Mean tree height increased from 4 to 5.3 m, stem basal area increased from 27 to 67 cm2 and total leaf area increased from 15 to 40 m2 between the lowest and highest rates of fertilizer addition. When trees were compared on the basis of leaf nitrogen per unit area (N(area)), light-saturated rates of photosynthesis on an area and mass basis and the maximum rate of electron transport all increased from 50% to more than 100% as N(area) increased from 0.8 to 2.1 g x m(-2). Branch specific hydraulic conductivity (ks) and kl increased with height in the crown. However, there was no change in branch kl or the ratio of leaf area to sapwood area of the whole shoot in response to fertilization, and ks and density of the sapwood were unrelated to leaf N(area). In contrast to photosynthesis, stomatal conductance did not respond to fertilization, leading to decreased internal carbon dioxide partial pressure (p(i)/p(a)) in fertilized plants and similar leaf water potentials in all plants. Consistent with the behavior of p(i)/p(a), carbon isotope discrimination decreased by 2% with increasing leaf N(area), supporting the conclusion that intrinsic water-use efficiency was enhanced by fertilization. Increased growth in response to fertilization involved adjustment at the leaf level rather than a change in the balance between water transport capacity and leaf area. It is proposed that, when there are changes in leaf properties without any external change in water availability or evaporative demand, leaf photosynthesis and stomatal conductance are partially constrained by the hydraulic architecture of the tree. PMID:11446997

  5. STEM Attrition: College Students' Paths into and out of STEM Fields. Statistical Analysis Report. NCES 2014-001

    ERIC Educational Resources Information Center

    Chen, Xianglei

    2013-01-01

    Producing sufficient numbers of graduates who are prepared for science, technology, engineering, and mathematics (STEM) occupations has become a national priority in the United States. To attain this goal, some policymakers have targeted reducing STEM attrition in college, arguing that retaining more students in STEM fields in college is a…

  6. Leaf hydraulics II: vascularized tissues.

    PubMed

    Rockwell, Fulton E; Holbrook, N Michele; Stroock, Abraham D

    2014-01-01

    Current models of leaf hydration employ an Ohm's law analogy of the leaf as an ideal capacitor, neglecting the resistance to flow between cells, or treat the leaf as a plane sheet with a source of water at fixed potential filling the mid-plane, neglecting the discrete placement of veins as well as their resistance. We develop a model of leaf hydration that considers the average conductance of the vascular network to a representative areole (region bounded by the vascular network), and represent the volume of tissue within the areole as a poroelastic composite of cells and air spaces. Solutions to the 3D flow problem are found by numerical simulation, and these results are then compared to 1D models with exact solutions for a range of leaf geometries, based on a survey of temperate woody plants. We then show that the hydration times given by these solutions are well approximated by a sum of the ideal capacitor and plane sheet times, representing the time for transport through the vasculature and tissue respectively. We then develop scaling factors relating this approximate solution to the 3D model, and examine the dependence of these scaling factors on leaf geometry. Finally, we apply a similar strategy to reduce the dimensions of the steady state problem, in the context of peristomatal transpiration, and consider the relation of transpirational gradients to equilibrium leaf water potential measurements. PMID:24012489

  7. STEM Careers Exploration

    NSDL National Science Digital Library

    This activity includes a presentation with links to videos about scientists and engineers working with NASA's Global Precipitation Measurement Mission (from the Faces of GPM series), as well as other STEM careers videos, followed by a number of links to online career resources. It is designed to be used by students working at their own pace, choosing which videos and links they are interested in watching and exploring, but could also be used with a larger group. As part of the activity, students identify personal skills and abilities related to career interests and develop a career goal. Includes a student capture sheet with guiding questions.

  8. STEM and Career Exploratory Classes

    ERIC Educational Resources Information Center

    Chase, Darrell

    2010-01-01

    Districts face increasing pressure to improve students' mastery of curriculum in the fields of science, technology, engineering and mathematics (STEM). Yet the number of students enrolling in science and math courses drops dramatically in middle and high school. At Sylvester Middle School, Chinook Middle School and Cascade Middle School of the…

  9. Stem Cell Therapy for Heart Failure

    PubMed Central

    2013-01-01

    The last decade has witnessed the publication of a large number of clinical trials primarily using bone marrow-derived stem cells as the injected cell. These “first-generation” clinical trials have advanced our understanding and shown us that (1) cell therapy is safe, (2) cell therapy has been modestly effective, and (3) in humans, bone marrow-derived stem cells do not transdifferentiate into cardiomyocytes or new blood vessels (or at least in sufficient numbers to have any effect). The primary mechanism of action for cell therapy is now believed to be through paracrine effects that include the release of cytokines, chemokines, and growth factors that inhibit apoptosis and fibrosis, enhance contractility, and activate endogenous regenerative mechanisms through endogenous circulating or site-specific stem cells. The new direction for clinical trials includes the use of stem cells capable of cardiac lineage, such as endogenous cardiac stem cells. PMID:24298308

  10. Evolution of leaf warbler songs (Aves: Phylloscopidae).

    PubMed

    Tietze, Dieter Thomas; Martens, Jochen; Fischer, Balduin S; Sun, Yue-Hua; Klussmann-Kolb, Annette; Päckert, Martin

    2015-02-01

    Songs in passerine birds are important for territory defense and mating. Speciation rates in oscine passerines are so high, due to cultural evolution, that this bird lineage makes up half of the extant bird species. Leaf warblers are a speciose Old-World passerine family of limited morphological differentiation, so that songs are even more important for species delimitation. We took 16 sonographic traits from song recordings of 80 leaf warbler taxa and correlated them with 15 potentially explanatory variables, pairwise, and in linear models. Based on a well-resolved molecular phylogeny of the same taxa, all pairwise correlations were corrected for relatedness with phylogenetically independent contrasts and phylogenetic generalized linear models were used. We found a phylogenetic signal for most song traits, but a strong one only for the duration of the longest and of the shortest element, which are presumably inherited instead of learned. Body size of a leaf warbler species is a constraint on song frequencies independent of phylogeny. At least in this study, habitat density had only marginal impact on song features, which even disappeared through phylogenetic correction. Maybe most leaf warblers avoid the deterioration through sound propagation in dense vegetation by singing from exposed perches. Latitudinal (and longitudinal) extension of the breeding ranges was correlated with most song features, especially verse duration (longer polewards and westwards) and complexity (lower polewards). Climate niche or expansion history might explain these correlations. The number of different element types per verse decreases with elevation, possibly due to fewer resources and congeneric species at higher elevations. PMID:25691998

  11. Evolution of leaf warbler songs (Aves: Phylloscopidae)

    PubMed Central

    Tietze, Dieter Thomas; Martens, Jochen; Fischer, Balduin S; Sun, Yue-Hua; Klussmann-Kolb, Annette; Päckert, Martin

    2015-01-01

    Songs in passerine birds are important for territory defense and mating. Speciation rates in oscine passerines are so high, due to cultural evolution, that this bird lineage makes up half of the extant bird species. Leaf warblers are a speciose Old-World passerine family of limited morphological differentiation, so that songs are even more important for species delimitation. We took 16 sonographic traits from song recordings of 80 leaf warbler taxa and correlated them with 15 potentially explanatory variables, pairwise, and in linear models. Based on a well-resolved molecular phylogeny of the same taxa, all pairwise correlations were corrected for relatedness with phylogenetically independent contrasts and phylogenetic generalized linear models were used. We found a phylogenetic signal for most song traits, but a strong one only for the duration of the longest and of the shortest element, which are presumably inherited instead of learned. Body size of a leaf warbler species is a constraint on song frequencies independent of phylogeny. At least in this study, habitat density had only marginal impact on song features, which even disappeared through phylogenetic correction. Maybe most leaf warblers avoid the deterioration through sound propagation in dense vegetation by singing from exposed perches. Latitudinal (and longitudinal) extension of the breeding ranges was correlated with most song features, especially verse duration (longer polewards and westwards) and complexity (lower polewards). Climate niche or expansion history might explain these correlations. The number of different element types per verse decreases with elevation, possibly due to fewer resources and congeneric species at higher elevations. PMID:25691998

  12. Inheritance of Leaf Rust Resistance in Wheat Cultivars Grandin and CDC Teal

    Microsoft Academic Search

    J. Q. Liu; J. A. Kolmer

    1997-01-01

    Liu, J. Q., and Kolmer, J. A. 1997. Inheritance of leaf rust resistance in wheat cu ltivars Grandin and CDC Teal. Plant Dis. 81:505-508. The hard red spring wheat cultivars Grandin and CDC Teal were genetically examined to de- termine the number and identity of the leaf rust resistance genes present in both wheats. The two cultivars were crossed with

  13. Leaf conductance and carbon gain under salt-stressed conditions S. Manzoni,2,3

    E-print Network

    Katul, Gabriel

    salinity effects on plant functioning [Marani et al., 2007; Bromberg Gedan et al., 2009]. [3] Exposure number of studies have focused on salt-stress effects on plant growth, leaf photosynthetic rates, CO2; published 29 December 2011. [1] Exposure of plants to salt stress is often accompanied by reductions in leaf

  14. Understanding the effect of carbon status on stem diameter variations

    PubMed Central

    De Swaef, Tom; Driever, Steven M.; Van Meulebroek, Lieven; Vanhaecke, Lynn; Marcelis, Leo F. M.; Steppe, Kathy

    2013-01-01

    Background Carbon assimilation and leaf-to-fruit sugar transport are, along with plant water status, the driving mechanisms for fruit growth. An integrated comprehension of the plant water and carbon relationships is therefore essential to better understand water and dry matter accumulation. Variations in stem diameter result from an integrated response to plant water and carbon status and are as such a valuable source of information. Methods A mechanistic water flow and storage model was used to relate variations in stem diameter to phloem sugar loading and sugar concentration dynamics in tomato. The simulation results were compared with an independent model, simulating phloem sucrose loading at the leaf level based on photosynthesis and sugar metabolism kinetics and enabled a mechanistic interpretation of the ‘one common assimilate pool’ concept for tomato. Key Results Combining stem diameter variation measurements and mechanistic modelling allowed us to distinguish instantaneous dynamics in the plant water relations and gradual variations in plant carbon status. Additionally, the model combined with stem diameter measurements enabled prediction of dynamic variables which are difficult to measure in a continuous and non-destructive way, such as xylem water potential and phloem hydrostatic potential. Finally, dynamics in phloem sugar loading and sugar concentration were distilled from stem diameter variations. Conclusions Stem diameter variations, when used in mechanistic models, have great potential to continuously monitor and interpret plant water and carbon relations under natural growing conditions. PMID:23186836

  15. Assessing Quantitative Resistance against Leptosphaeria maculans (Phoma Stem Canker) in Brassica napus (Oilseed Rape) in Young Plants

    PubMed Central

    Huang, Yong-Ju; Qi, Aiming; King, Graham J.; Fitt, Bruce D. L.

    2014-01-01

    Quantitative resistance against Leptosphaeria maculans in Brassica napus is difficult to assess in young plants due to the long period of symptomless growth of the pathogen from the appearance of leaf lesions to the appearance of canker symptoms on the stem. By using doubled haploid (DH) lines A30 (susceptible) and C119 (with quantitative resistance), quantitative resistance against L. maculans was assessed in young plants in controlled environments at two stages: stage 1, growth of the pathogen along leaf veins/petioles towards the stem by leaf lamina inoculation; stage 2, growth in stem tissues to produce stem canker symptoms by leaf petiole inoculation. Two types of inoculum (ascospores; conidia) and three assessment methods (extent of visible necrosis; symptomless pathogen growth visualised using the GFP reporter gene; amount of pathogen DNA quantified by PCR) were used. In stage 1 assessments, significant differences were observed between lines A30 and C119 in area of leaf lesions, distance grown along veins/petioles assessed by visible necrosis or by viewing GFP and amount of L. maculans DNA in leaf petioles. In stage 2 assessments, significant differences were observed between lines A30 and C119 in severity of stem canker and amount of L. maculans DNA in stem tissues. GFP-labelled L. maculans spread more quickly from the stem cortex to the stem pith in A30 than in C119. Stem canker symptoms were produced more rapidly by using ascospore inoculum than by using conidial inoculum. These results suggest that quantitative resistance against L. maculans in B. napus can be assessed in young plants in controlled conditions. Development of methods to phenotype quantitative resistance against plant pathogens in young plants in controlled environments will help identification of stable quantitative resistance for control of crop diseases. PMID:24454767

  16. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture...12, 13, 14 and Foreign Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  17. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  18. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 2014-01-01 false Leaf surface. 29.3036 Section 29...and Foreign Type 93) § 29.3036 Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

  19. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 2012-01-01 false Leaf surface. 29.3036 Section 29...and Foreign Type 93) § 29.3036 Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

  20. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture...12, 13, 14 and Foreign Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  1. Very Sparse Leaf Languages Lance Fortnow

    E-print Network

    Fortnow, Lance

    Very Sparse Leaf Languages Lance Fortnow Department of Computer Science University of Chicago studied the balanced leaf languages defined via poly-logarithmically sparse leaf pattern sets. Unger shows that NP-complete sets are not polynomial-time many-one reducible to such balanced leaf language unless

  2. 7 CFR 29.3528 - Leaf surface.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 2012-01-01 false Leaf surface. 29.3528 Section 29...and Foreign Type 95) § 29.3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf. Leaf surface is affected to some...

  3. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture...s. Type 31 and Foreign Type 93) § 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  4. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 2013-01-01 false Leaf surface. 29.3036 Section 29...and Foreign Type 93) § 29.3036 Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is affected to...

  5. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture...s. Type 31 and Foreign Type 93) § 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  6. Very Sparse Leaf Languages # Lance Fortnow +

    E-print Network

    Fortnow, Lance

    Very Sparse Leaf Languages # Lance Fortnow + Department of Computer Science University of Chicago studied the balanced leaf languages defined via poly­logarithmically sparse leaf pattern sets. Unger shows that NP­complete sets are not polynomial­time many­one reducible to such balanced leaf language unless

  7. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture...35, 36, 37 and Foreign Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  8. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture...s. Type 31 and Foreign Type 93) § 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  9. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  10. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  11. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture...12, 13, 14 and Foreign Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  12. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture...35, 36, 37 and Foreign Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  13. 7 CFR 29.3528 - Leaf surface.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 2013-01-01 false Leaf surface. 29.3528 Section 29...and Foreign Type 95) § 29.3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf. Leaf surface is affected to some...

  14. 7 CFR 29.3528 - Leaf surface.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 2014-01-01 false Leaf surface. 29.3528 Section 29...and Foreign Type 95) § 29.3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf. Leaf surface is affected to some...

  15. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture...35, 36, 37 and Foreign Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip...

  16. Thinkfinity: STEM

    NSDL National Science Digital Library

    The Verizon Foundation's Thinkfinity website has a very large section of STEM resources for students and teachers. Near the bottom of the homepage visitors will find "Lesson Plans", "Podcasts", and "Resources and Tools". In addition, there is a community forum where members discuss their thoughts on some of the resources from the website they have found useful, or how they have modified them to suit their classroom situation. Visitors to the site can easily register for free to join the community. The "At Home and Afterschool" tab near the top of the page has a "games and tools" section that includes activities, videos, and collections, as well as other types of resources. The literacy section of the "Afterschool" area has many resources for families and games for early literacy. Visitors can also use the "Professional Development" tab to find information on how to utilize the many Thinkfinity resources.

  17. Switchgrass (Panicum virgatum L) flag leaf transcriptomes reveal molecular signatures of leaf development, senescence, and mineral dynamics.

    PubMed

    Palmer, Nathan A; Donze-Reiner, Teresa; Horvath, David; Heng-Moss, Tiffany; Waters, Brian; Tobias, Christian; Sarath, Gautam

    2015-01-01

    Switchgrass flag leaves can be expected to be a source of carbon to the plant, and its senescence is likely to impact the remobilization of nutrients from the shoots to the rhizomes. However, many genes have not been assigned a function in specific stages of leaf development. Here, we characterized gene expression in flag leaves over their development. By merging changes in leaf chlorophyll and the expression of genes for chlorophyll biosynthesis and degradation, a four-phase molecular roadmap for switchgrass flag leaf ontogeny was developed. Genes associated with early leaf development were up-regulated in phase 1. Phase 2 leaves had increased expression of genes for chlorophyll biosynthesis and those needed for full leaf function. Phase 3 coincided with the most active phase for leaf C and N assimilation. Phase 4 was associated with the onset of senescence, as observed by declining leaf chlorophyll content, a significant up-regulation in transcripts coding for enzymes involved with chlorophyll degradation, and in a large number of senescence-associated genes. Of considerable interest were switchgrass NAC transcription factors with significantly higher expression in senescing flag leaves. Two of these transcription factors were closely related to a wheat NAC gene that impacts mineral remobilization. The third switchgrass NAC factor was orthologous to an Arabidopsis gene with a known role in leaf senescence. Other genes coding for nitrogen and mineral utilization, including ureide, ammonium, nitrate, and molybdenum transporters, shared expression profiles that were significantly co-regulated with the expression profiles of the three NAC transcription factors. These data provide a good starting point to link shoot senescence to the onset of dormancy in field-grown switchgrass. PMID:25173486

  18. BOREAS TE-12 Leaf Gas Exchange Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Arkebauer, Timothy J.; Yang, Litao

    2000-01-01

    The BOREAS TE-12 team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, and gas exchange of boreal vegetation. This data set contains measurements of leaf gas exchange conducted in the SSA during the growing seasons of 1994 and 1995 using a portable gas exchange system. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Center (DAAC).

  19. PLANT SPECIES RECOGNITION USING SPATIAL CORRELATION BETWEEN THE LEAF MARGIN AND THE LEAF SALIENT POINTS

    E-print Network

    Paris-Sud XI, Université de

    PLANT SPECIES RECOGNITION USING SPATIAL CORRELATION BETWEEN THE LEAF MARGIN AND THE LEAF SALIENT by the plant leaves. More precisely, we consider two sources of information: the leaf margin and the leaf salient points. We investigate two shape context based descriptors: the first one describes the leaf

  20. Multi-trait interactions, not phylogeny, fine-tune leaf size reduction with increasing altitude

    PubMed Central

    Milla, Rubén; Reich, Peter B.

    2011-01-01

    Background and Aims Despite long-held interest, knowledge on why leaf size varies widely among species is still incomplete. This study was conducted to assess whether abiotic factors, phylogenetic histories and multi-trait interactions act together to shape leaf size. Methods Fifty-seven pairs of altitudinal vicariant species were selected in northern Spain, and leaf area and a number of functionally related leaf, shoot and whole plant traits were measured for each pair. Structural equation modelling helped unravel trait interactions affecting leaf size, and Mantel tests weighed the relative relevance of phylogeny, environment and trait interactions to explain leaf size reduction with altitude. Key Results Leaves of highland vicariants were generally smaller than those of lowlands. However, the extent of leaf size reduction with increasing altitude was widely variable among genera: from approx. 700 cm2 reduction (96 % in Polystichum) to approx. 30 cm2 increase (37 % in Sorbus). This was partially explained by shifts in leaf, shoot and whole plant traits (35–64 % of explained variance, depending on models), with size/number trade-offs more influential than shifts in leaf form and leaf economics. Shifts in traits were more important than phylogenetic distances or site-specific environmental variation in explaining the degree of leaf size reduction with altitude. Conclusions Ecological filters, constraints due to phylogenetic history (albeit modest in the study system), and phenotypic integration contribute jointly to shape single-trait evolution. Here, it was found that phenotypic change was far more important than shared ancestry to explaine leaf size differences of closely related species segregated along altitudes. PMID:21199835

  1. Epidermal Stem Cells

    Microsoft Academic Search

    V. V. Terskikh; A. V. Vasil'ev

    2001-01-01

    Epidermis contains a compartment of stem cells but currently there is no common criterion to recognize individual stem cells with any confidence. Epidermis appears to contain stem cells of different levels of maturity and it is very likely that the main repository of epidermal stem cells is located in the hair follicle from which cells can emigrate into epidermis and

  2. Rotatable stem and lock

    DOEpatents

    Deveney, Joseph E. (Albuquerque, NM); Sanderson, Stephen N. (Albuquerque, NM)

    1984-01-01

    A valve stem and lock include a housing surrounding a valve stem, a solenoid affixed to an interior wall of the housing, an armature affixed to the valve stem and a locking device for coupling the armature to the housing body. When the solenoid is energized, the solenoid moves away from the housing body, permitting rotation of the valve stem.

  3. Rotatable stem and lock

    DOEpatents

    Deveney, J.E.; Sanderson, S.N.

    1981-10-27

    A valve stem and lock is disclosed which includes a housing surrounding a valve stem, a solenoid affixed to an interior wall of the housing, an armature affixed to the valve stem and a locking device for coupling the armature to the housing body. When the solenoid is energized, the solenoid moves away from the housing body, permitting rotation of the valve stem.

  4. Stem cells in urology

    Microsoft Academic Search

    Tamer Aboushwareb; Anthony Atala

    2008-01-01

    The shortage of donors for organ transplantation has stimulated research on stem cells as a potential resource for cell-based therapy in all human tissues. Stem cells have been used for regenerative medicine applications in many organ systems, including the genitourinary system. The potential applications for stem cell therapy have, however, been restricted by the ethical issues associated with embryonic stem

  5. Toward ‘SMART’ stem cells

    Microsoft Academic Search

    T Cheng

    2008-01-01

    Stem cell research is at the heart of regenerative medicine, which holds great promise for the treatment of many devastating disorders. However, in addition to hurdles posed by well-publicized ethical issues, this emerging field presents many biological challenges. What is a stem cell? How are embryonic stem cells different from adult stem cells? What are the physiological bases for therapeutically

  6. Comparison of Modeled and Observed Environmental Influences on the Stable Oxygen and Hydrogen Isotope Composition of Leaf Water in Phaseolus vulgaris L. 1

    PubMed Central

    Flanagan, Lawrence B.; Comstock, Jonathan P.; Ehleringer, James R.

    1991-01-01

    In this paper we describe how a model of stable isotope fractionation processes, originally developed by H. Craig and L. I. Gordon ([1965] in E Tongiorgi, ed, Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, Italy, pp 9-130) for evaporation of water from the ocean, can be applied to leaf transpiration. The original model was modified to account for turbulent conditions in the leaf boundary layer. Experiments were conducted to test the factors influencing the stable isotopic composition of leaf water under controlled environment conditions. At steady state, the observed leaf water isotopic composition was enriched above that of stem water with the extent of the enrichment dependent on the leaf-air vapor pressure difference (VPD) and the isotopic composition of atmospheric water vapor (AWV). The higher the VPD, the larger was the observed heavy isotope content of leaf water. At a constant VPD, leaf water was relatively depleted in heavy isotopes when exposed to AWV with a low heavy isotope composition, and leaf water was relatively enriched in heavy isotopes when exposed to AWV with a large heavy isotope composition. However, the observed heavy isotope composition of leaf water was always less than that predicted by the model. The extent of the discrepancy between the modeled and observed leaf water isotopic composition was a strong linear function of the leaf transpiration rate. PMID:16668226

  7. Why do leaf-tying caterpillars abandon their leaf ties?

    PubMed Central

    Sliwinski, Michelle

    2013-01-01

    Leaf-tying caterpillars act as ecosystem engineers by building shelters between overlapping leaves, which are inhabited by other arthropods. Leaf-tiers have been observed to leave their ties and create new shelters (and thus additional microhabitats), but the ecological factors affecting shelter fidelity are poorly known. For this study, we explored the effects of resource limitation and occupant density on shelter fidelity and assessed the consequences of shelter abandonment. We first quantified the area of leaf material required for a caterpillar to fully develop for two of the most common leaf-tiers that feed on white oak, Quercus alba. On average, Psilocorsis spp. caterpillars consumed 21.65 ± 0.67 cm2 leaf material to complete development. We also measured the area of natural leaf ties found in a Maryland forest, to determine the distribution of resources available to caterpillars in situ. Of 158 natural leaf ties examined, 47% were too small to sustain an average Psilocorsis spp. caterpillar for the entirety of its development. We also manipulated caterpillar densities within experimental ties on potted trees to determine the effects of cohabitants on the likelihood of a caterpillar to leave its tie. We placed 1, 2, or 4 caterpillars in ties of a standard size and monitored the caterpillars twice daily to track their movement. In ties with more than one occupant, caterpillars showed a significantly greater propensity to leave their tie, and left sooner and at a faster rate than those in ties as single occupants. To understand the consequences of leaf tie abandonment, we observed caterpillars searching a tree for a site to build a shelter in the field. This is a risky behavior, as 17% of the caterpillars observed died while searching for a shelter site. Caterpillars that successfully built a shelter traveled 110 ± 20 cm and took 28 ± 7 min to find a suitable site to build a shelter. In conclusion, leaf-tying caterpillars must frequently abandon their leaf tie due to food limitation and interactions with other caterpillars, but this is a costly behavior. PMID:24109557

  8. What determines a leaf's shape?

    PubMed

    Dkhar, Jeremy; Pareek, Ashwani

    2014-01-01

    The independent origin and evolution of leaves as small, simple microphylls or larger, more complex megaphylls in plants has shaped and influenced the natural composition of the environment. Significant contributions have come from megaphyllous leaves, characterized usually as flat, thin lamina entrenched with photosynthetic organelles and stomata, which serve as the basis of primary productivity. During the course of evolution, the megaphylls have attained complexity not only in size or venation patterns but also in shape. This has fascinated scientists worldwide, and research has progressed tremendously in understanding the concept of leaf shape determination. Here, we review these studies and discuss the various factors that contributed towards shaping the leaf; initiated as a small bulge on the periphery of the shoot apical meristem (SAM) followed by asymmetric outgrowth, expansion and maturation until final shape is achieved. We found that the underlying factors governing these processes are inherently genetic: PIN1 and KNOX1 are indicators of leaf initiation, HD-ZIPIII, KANADI, and YABBY specify leaf outgrowth while ANGUSTIFOLIA3 and GROWTH-REGULATING FACTOR5 control leaf expansion and maturation; besides, recent research has identified new players such as APUM23, known to specify leaf polarity. In addition to genetic control, environmental factors also play an important role during the final adjustment of leaf shape. This immense amount of information available will serve as the basis for studying and understanding innovative leaf morphologies viz. the pitchers of the carnivorous plant Nepenthes which have evolved to provide additional support to the plant survival in its nutrient-deficient habitat. In hindsight, formation of the pitcher tube in Nepenthes might involve the recruitment of similar genetic mechanisms that occur during sympetaly in Petunia. PMID:25584185

  9. Stem Cell 101 What is a stem cell?

    E-print Network

    Minnesota, University of

    Stem Cell 101 What is a stem cell? A stem cell is a parent cell in the body that has two specific into all types of tissue in the body ­ this is called differentiation. Where are stem cells found? There are two types of stem cells: embryonic stem cells, found in embryos, and adult stem cells, which can

  10. Stem Cells, Phenotypic Inversion, and Differentiation

    PubMed Central

    Siggins, Robert W.; Zhang, Ping; Welsh, David; LeCapitaine, Nicole J.; Nelson, Steve

    2008-01-01

    Stem cells possess the potential to cure a myriad of ailments ranging from congenital diseases to illnesses acquired through the physiological process of aging. In the adult, these cells are extremely rare and often difficult to isolate in numbers sufficient to apply to medical treatment. Ex vivo expansion of these cells will be required for most meaningful interventions. The discovery of stem/progenitor cell inversion offers a new avenue for obtaining sufficient numbers of stem cells. Adult progenitor cells are much more common than quiescent stem cells and can be isolated with minimal interventions; therefore, inversion of progenitors to stem cells may become a feasible approach for therapeutic purposes. Stem cells are known to possess few mitochondria, and mitochondrial biogenesis is required for stem cell differentiation. The microtubule cytoskeleton is a major regulator for mitochondrial biogenesis. Investigations in the area of controlling cell differentiation and inducing phenotypic inversion, possibly through manipulation of mitochondrial biogenesis, may contribute to stem cell-based therapies. PMID:19079683

  11. Response of azalea cuttings to leaf damage and leaf removal

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Binucleate Rhizoctonia species, the pathogens that cause azalea web blight, can be carried on stem cuttings, perpetuating the disease through subsequent crops. Previous studies have demonstrated that submerging Rhizoctonia-infested stem pieces of 'Gumpo White' azalea in 122°F (50°C) water for 20 min...

  12. Verbal stem space and verb to noun conversion in French1

    E-print Network

    Paris-Sud XI, Université de

    Verbal stem space and verb to noun conversion in French1 Delphine Tribout Abstract In this paper I present the verbal stem space in French and its use in lexeme formation. First, I present the stem spaces stem space needs to be extended with an extra slot in order to account for a number of lexeme

  13. Cell reprogramming: expectations and challenges for chemistry in stem cell biology and regenerative medicine

    Microsoft Academic Search

    L Anastasia; G Pelissero; B Venerando; G Tettamanti

    2010-01-01

    The possibility of reprogramming adult somatic cells into pluripotent stem cells (iPSCs) has generated a renewed interest into stem cell research and promises to overcome several key issues, including the ethical concerns of using human embryonic stem cells and the difficulty of obtaining large numbers of adult stem cells (Belmonte et al., Nat Rev Genet, 2009). This approach is also

  14. Degradation of mangrove leaf litter under aerobic conditions

    Microsoft Academic Search

    F. M. M. Chale

    1993-01-01

    Degradation ofAvicennia marina (Forsk) Vierh. leaf litter was studied in the laboratory for three months. The leaves were incubated in filtered estuarine water in erlenmeyer flasks for various number of days and the amounts of N, P, and K+ remaining in the leaves determined. Weight loss was rapid within the first 24 hours (19%), but slowed down thereafter reaching 30%

  15. Colony morphology of Xylella fastidiosa almond leaf scorch strains

    Microsoft Academic Search

    Jianchi Chen; Russell Groves; Edwin L. Civerolo; Yiwei Zheng; Mario Viveros; Mark Freeman

    2007-01-01

    Xylella fastidiosa is the causal agent of almond leaf scorch disease (ALSD), which is currently reemerging in California as a potential threat to almond (Prunus dulcis) production. We previously reported the presence of different colony morphotypes of X. fastidiosa ALSD strains on periwinkle wilt medium solidified with Gelrite and their association with genotypes or pathotypes after a low number of

  16. Direct regeneration of Drosera from leaf explants and shoot tips

    Microsoft Academic Search

    Anna Kawiak; Aleksandra Królicka; Ewa Lojkowska

    2003-01-01

    An efficient protocol for the micropropagation of Drosera anglica, D. binata and D. cuneifolia is described. Proliferation was obtained from leaf segments and shoot tips, which served as initial explants. The regeneration capacity of explants was influenced by factors such as nutrient media, concentrations of growth regulators and the type of medium (liquid or solid). The highest number of plants

  17. Seasonal polyphenism and leaf mimicry in the comma butterfly

    E-print Network

    Tullberg, Birgitta

    Seasonal polyphenism and leaf mimicry in the comma butterfly CHRISTER WIKLUND & BIRGITTA S 2003; final acceptance 21 December 2003; MS. number: 7774) The comma butterfly, Polygonia c as a result of high predation pressure. Although butterflies in temperate areas that start reproduction soon

  18. NON-DESTRUCTIVE ASSESSMENT OF ARUNDO DONAX (POACEAE) LEAF QUALITY.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leaf quality information (i.e., leaf C content, leaf N content, leaf C:N ratio) is especially useful for understanding plant-herbivore interactions and may be important in developing control methods for the invasive riparian plant Arundo donax L. We measured leaf C content, leaf N content, leaf C:N ...

  19. Pharmacognostic studies of the leaves and stem of Careya arborea Roxb.

    PubMed Central

    Gupta, Prakash Chandra; Sharma, Nisha; Rao, Ch V

    2012-01-01

    Objective To study detailed pharmacognostic profile of leaves and stem of Careya arborea (C. arborea) Roxb. (Lecthyidaceae), an important medicinal plant in the Indian system of medicine. Methods Leaf and stem samples of C. arborea were studied by macroscopical, microscopical, physicochemical, phytochemical, fluorescence analysis of powder of the plant and other methods for standardization recommended by WHO. Results Macroscopically, the leaves are simple, broadly obovate in shape, acuminate apex with crenate, dentate margin, petioles (0.1–1.8 cm) long. Microscopically, the leaf showed the presence of median large size vascular bundle covered with fibrous bundle sheath, arrangement of xylem in cup shape and presence of cortical vascular bundle, patches of sclerenchyma, phloem fibers in groups and brown pigment containing cells in stem are some of the diagnostic features noted from anatomical study. Powder microscopy of leaf revealed the presence of parenchyma cells, xylem with pitted vessels and epidermis with anisocytic stomata. The investigations also included leaf surface data; quantitative leaf microscopy and fluorescence analysis. Physiochemical parameters such as loss on drying, swelling index, extractive values and ash values were also determined and results showed that total ash of the stem bark was about two times higher than leaf and water soluble extractive value of leaf and stem bark was two times higher than alcohol soluble extractive value. Preliminary phytochemical screening showed the presence of triterpenoids, saponins, tannins and flavonoids. Conclusions The results of the study can serve as a valuable source of information and provide suitable standards for identification of this plant material in future investigations and applications. PMID:23569939

  20. First Record of Alternaria simsimi Causing Leaf Spot on Sesame (Sesamum indicum L.) in Korea

    PubMed Central

    Choi, Young Phil; Paul, Narayan Chandra

    2014-01-01

    Leaf spot disease was observed in sesame (Sesamum indicum L.) during 2009 and 2010 in Korea. The pathogen was identified as Alternaria simsimi based on morphological and cultural characteristics. The morphological identification was well supported by phylogenetic analysis of the ribosomal DNA-internal transcribed spacer region. A. simsimi isolates caused spot symptoms on leaves and stems of sesame plants 2 wk after artificial inoculation, which were similar to those observed in the field. This is the first record of leaf spot disease in Korea caused by A. simsimi. PMID:25606015

  1. First Record of Alternaria simsimi Causing Leaf Spot on Sesame (Sesamum indicum L.) in Korea.

    PubMed

    Choi, Young Phil; Paul, Narayan Chandra; Lee, Hyang Burm; Yu, Seung Hun

    2014-12-01

    Leaf spot disease was observed in sesame (Sesamum indicum L.) during 2009 and 2010 in Korea. The pathogen was identified as Alternaria simsimi based on morphological and cultural characteristics. The morphological identification was well supported by phylogenetic analysis of the ribosomal DNA-internal transcribed spacer region. A. simsimi isolates caused spot symptoms on leaves and stems of sesame plants 2 wk after artificial inoculation, which were similar to those observed in the field. This is the first record of leaf spot disease in Korea caused by A. simsimi. PMID:25606015

  2. Stem cell transplantation for treating Parkinson's disease

    PubMed Central

    Li, Runhui

    2012-01-01

    OBJECTIVE: To identify global research trends of stem cell transplantation for treating Parkinson's disease using a bibliometric analysis of the Web of Science. DATA RETRIEVAL: We performed a bibliometric analysis of data retrievals for stem cell transplantation for treating Parkinson's disease from 2002 to 2011 using the Web of Science. SELECTION CRITERIA: Inclusion criteria: (a) peer-reviewed articles on stem cell transplantation for treating Parkinson's disease which were published and indexed in the Web of Science; (b) type of articles: original research articles, reviews, meeting abstracts, proceedings papers, book chapters, editorial material and news items; (c) year of publication: 2002–2011. Exclusion criteria: (a) articles that required manual searching or telephone access; (b) we excluded documents that were not published in the public domain; (c) we excluded a number of corrected papers from the total number of articles. MAIN OUTCOME MEASURES: (1) Type of literature; (2) annual publication output; (3) distribution according to journals; (4) distribution according to subject areas; (5) distribution according to country; (6) distribution according to institution; (7) comparison of countries that published the most papers on stem cell transplantation from different cell sources for treating Parkinson's disease; (8) comparison of institutions that published the most papers on stem cell transplantation from different cell sources for treating Parkinson's disease in the Web of Science from 2002 to 2011; (9) comparison of studies on stem cell transplantation from different cell sources for treating Parkinson's disease RESULTS: In total, 1 062 studies on stem cell transplantation for treating Parkinson's disease appeared in the Web of Science from 2002 to 2011, almost one third of which were from American authors and institutes. The number of studies on stem cell transplantation for treating Parkinson's disease had gradually increased over the past 10 years. Papers on stem cell transplantation for treating Parkinson's disease appeared in journals such as Stem Cells and Experimental Neurology. Although the United States published more articles addressing neural stem cell and embryonic stem cell transplantation for treating Parkinson's disease, China ranked first for articles published on bone marrow mesenchymal stem cell transplantation for treating Parkinson's disease. CONCLUSION: From our analysis of the literature and research trends, we found that stem cell transplantation for treating Parkinson's disease may offer further benefits in regenerative medicine. PMID:25709626

  3. STEm Minority Graduate Program

    SciTech Connect

    Kaen E. Nicholas

    2012-09-20

    ABSTRACT The state of science, technology, engineering and math (STEM) education in the United States has seen some unfavorable assessments over the past decade. In early February, 2010 the House of Representatives heard testimony on undergraduate and graduate education. The message from the panel, which included experts from academia, STEM-based industries, and the National Science Foundation (NSF) was dire and required an urgent response. The experts along with the committee���¢��������s chairperson, U. S. Representative Daniel Lipinski (D-IL) cited that the complexity of Science, Technology, Engineering, and Mathematics applications and coursework and the methodology utilized to teach these subjects are forcing students out of these disciplines. As the National Academies described in its 2007 report Rising Above the Gathering Storm, successful STEM education is not just an academic pursuit���¢��������it���¢��������s a necessity for competing in the knowledge-based economy that the United States had a key role in creating. The potential for action is being made available again as the America COMPETES Act of 2007 is up for reauthorization. Its initial focus was on STEM education at the K-12 levels, but efforts at the undergraduate and graduate levels are needed to retain students to fill the jobs left vacant as baby boomers retire. The Educational Advancement Alliance, Inc. (EAA) has for two decades created programs that have not only addressed the issues of ensuring that students are aptly prepared for college but have focused its efforts over the past decade on increasing the number of students who pursue degrees in STEM disciplines. For the EAA, the introduction of the wonders of science begins at the elementary and middle school level via the Learning Lab, a state-of-the-art mobile science laboratory that visits students in grades 4-6 at the various schools throughout Philadelphia and The Math/Tech Academy which meets on Saturdays for students in grades 5-7. For the past two years the EAA has assisted college graduates in their quest to attain advanced degrees in STEM by providing fellowships. The EAA continued this effort by recruiting and providing fellowships to students who aspired to continue their education at the graduate level. The fellowships provided funding for tuition, fees, books, technology, and stipends to assist with room, board, and living expenses during the academic year and salary, transportation, and living expenses to those students who secured internships with the Department of Energy. Additionally the EAA designed and implemented needed support systems to ensure successful completion of the Masters degree programs, including but not limited to membership in professional associations, attendance at industry and academic conferences, and professional development workshops, and tutorial assistance if needed. This program assisted over 80 students directly and society-at-large by helping to educate and develop future physicists, engineers, biostatisticians, and researchers who will have the necessary skillsets to fill the increasing numbers of positions that require such expertise.

  4. Mesenchymal stem cells secreting angiopoietin-like-5 support efficient expansion of human hematopoietic stem cells without compromising their repopulating potential

    E-print Network

    Drake, Adam

    Clinical and preclinical applications of human hematopoietic stem cells (HSCs) are often limited by scarcity of cells. Expanding human HSCs to increase their numbers while maintaining their stem cell properties has therefore ...

  5. Effects of mechanical stress or abscisic acid on growth, water status and leaf abscisic acid content of eggplant seedlings

    NASA Technical Reports Server (NTRS)

    Latimer, J. G.; Mitchell, C. A.

    1988-01-01

    Container-grown eggplant (Solanum melongena L. var esculentum Nees. 'Burpee's Black Beauty') seedlings were conditioned with brief, periodic mechanical stress or abscisic acid (ABA) in a greenhouse prior to outdoor exposure. Mechanical stress consisted of seismic (shaking) or thigmic (stem flexing) treatment. Exogenous ABA (10(-3) or 10(-4)M) was applied as a soil drench 3 days prior to outdoor transfer. During conditioning, only thigmic stress reduced stem elongation and only 10(-3) M ABA reduced relative growth rate (RGR). Both conditioning treatments increased leaf specific chlorophyll content, but mechanical stress did not affect leaf ABA content. Outdoor exposure of unconditioned eggplant seedlings decreased RGR and leaf-specific chlorophyll content, but tended to increase leaf ABA content relative to that of plants maintained in the greenhouse. Conditioning did not affect RGR of plants subsequently transferred outdoors, but did reduce stem growth. Seismic stress applied in the greenhouse reduced dry weight gain by plants subsequently transferred outdoors. Mechanical stress treatments increased leaf water potential by 18-25% relative to that of untreated plants.

  6. Survival, germination, and growth of Epichloe typhina and significance of leaf wounds and insects in infection of orchardgrass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Epichloë typhina, [choke] is an important stroma-producing endophytic ascomycete that is responsible for significant yield loss in orchardgrass seed production fields. Although infections are presumed to occur through leaves and stems, details of the infection process and conditions that favor leaf ...

  7. Stem Cell Origin of Testicular Seminoma

    PubMed Central

    Som, Avik; Wen, Sijin; Tu, Shi-Ming

    2013-01-01

    A major question regarding cancer is its cells of origin. The discovery of diverse tumors being derived from a hierarchy of stem cells may pave the way to prove the theory of a stem cell origin of cancers. To our knowledge, we have evidence for the first time in human samples that unique germ cell tumors are linked to particular germline stem cells on the basis of their molecular expression profile. We postulated that distinct malignant subtypes arise from certain stem cells in a stem cell hierarchy. Introduction A major question concerning cancer is its cells of origin. We hypothesized that distinct cancer subtypes arise from unique cancer-initiating cells. By performing a microarray meta-analysis of seminomas and spermatogonial stem cells, we investigated a putative cell of origin for seminoma. Materials and Methods We obtained published microarray data for 6 human adult germ cell lines, 16 embryonic stem cell lines, 3 normal testicular tissue samples, and 40 seminomas from the Gene Expression Omnibus database. By assessing correlations between various tissue microarrays, we determined the number of transitional events and the distance between seminomas and human spermatogonial stem cells. Results Our meta-analysis showed that spermatogonial stem cells correlated similarly with seminoma (95% CI of Spearman ?, 0.33–0.44) and with normal somatic testicular tissue cells (95% CI, 0.39–0.40), which suggests parallel paths of cellular origins. Conclusion Analysis of our results suggests that a unique cancer subtype, namely seminoma, may have originated from an undifferentiated cell with stemness features rather than from a differentiated cell that acquired stemness features. PMID:23850550

  8. Leaf-inhabiting genera of the Gnomoniaceae, Diaporthales

    PubMed Central

    Sogonov, M.V.; Castlebury, L.A.; Rossman, A.Y.; Mejía, L.C.; White, J.F.

    2008-01-01

    The Gnomoniaceae are characterised by ascomata that are generally immersed, solitary, without a stroma, or aggregated with a rudimentary stroma, in herbaceous plant material especially in leaves, twigs or stems, but also in bark or wood. The ascomata are black, soft-textured, thin-walled, and pseudoparenchymatous with one or more central or eccentric necks. The asci usually have a distinct apical ring. The Gnomoniaceae includes species having ascospores that are small, mostly less than 25 ?m long, although some are longer, and range in septation from non-septate to one-septate, rarely multi-septate. Molecular studies of the Gnomoniaceae suggest that the traditional classification of genera based on characteristics of the ascomata such as position of the neck and ascospores such as septation have resulted in genera that are not monophyletic. In this paper the concepts of the leaf-inhabiting genera in the Gnomoniaceae are reevaluated using multiple genes, specifically nrLSU, translation elongation factor 1-alpha (tef1-?), and RNA polymerase II second largest subunit (rpb2) for 64 isolates. ITS sequences were generated for 322 isolates. Six genera of leaf-inhabiting Gnomoniaceae are defined based on placement of their type species within the multigene phylogeny. The new monotypic genus Ambarignomonia is established for an unusual species, A. petiolorum. A key to 59 species of leaf-inhabiting Gnomoniaceae is presented and 22 species of Gnomoniaceae are described and illustrated. PMID:19287541

  9. Stemming heart failure with cardiac- or reprogrammed-stem cells.

    PubMed

    Tateishi, Kento; Takehara, Naofumi; Matsubara, Hiroaki; Oh, Hidemasa

    2008-12-01

    Despite extensive efforts to control myocyte growth by genetic targeting of the cell cycle machinery and small molecules for cardiac repair, adult myocytes themselves appeared to divide a limited number of times in response to a variety of cardiac muscle stresses. Rare tissue-resident stem cells are thought to exist in many adult organs that are capable of self-renewal and differentiation and possess a range of actions that are potentially therapeutic. Recent studies suggest that a population of cardiac stem cells (CSCs) is maintained after cardiac development in the adult heart in mammals including human beings; however, homeostatic cardiomyocyte replacement might be stem cell-dependent, and functional myocardial regeneration after cardiac muscle damage is not yet considered as sufficient to fully maintain or reconstitute the cardiovascular system and function. Although it is clear that adult CSCs have limitations in their capabilities to proliferate extensively and differentiate in response to injury in vivo for replenishing mature car-diomyocytes and potentially function as resident stem cells. Transplantation of CSCs expanded ex vivo seems to require an integrated strategy of cell growth-enhancing factor(s) and tissue engineering technologies to support the donor cell survival and subsequent proliferation and differentiation in the host microenvironment. There has been substantial interest regarding the evidence that mammalian fibroblasts can be genetically reprogrammed to induced pluripotent stem (iPS) cells, which closely resemble embryonic stem (ES) cell properties capable of differentiating into functional cardiomyocytes, and these cells may provide an alternative cell source for generating patient-specific CSCs for therapeutic applications. PMID:18754813

  10. The master degree: A critical transition in STEM doctoral education

    Microsoft Academic Search

    Sheila Edwards Lange

    2006-01-01

    The need to broaden participation in the nation's science, technology, engineering, and mathematics (STEM) undergraduate and graduate programs is currently a matter of national urgency. The small number of women and underrepresented minorities (URM) earning doctoral degrees in STEM is particularly troubling given significant increases in the number of students earning master's degrees since 1990. In the decade between 1990

  11. OPT STEM EXTENSION APPLICATION What is the OPT STEM Extension?

    E-print Network

    OPT STEM EXTENSION APPLICATION What is the OPT STEM Extension? The OPT STEM Extension is a 17-month based on a bachelor's, master's, or Ph.D in certain STEM (Science, Technology, Engineering, Math) fields. Who is Eligible for the OPT STEM Extension? F-1 students who: 1). hold a STEM degree (see pg. 2

  12. Stem cell therapy in neurodegenerative diseases

    PubMed Central

    Sakthiswary, Rajalingham; Raymond, Azman Ali

    2012-01-01

    The lack of curative therapies for neurodegenerative diseases has high economic impact and places huge burden on the society. The contribution of stem cells to cure neurodegenerative diseases has been unraveled and explored extensively over the past few years. Beyond substitution of the lost neurons, stem cells act as immunomodulators and neuroprotectors. A large number of preclinical and a small number of clinical studies have shown beneficial outcomes in this context. In this review, we have summarized the current concepts of stem cell therapy in neurodegenerative diseases and the recent advances in this field, particularly between 2010 and 2012. Further studies should be encouraged to resolve the clinical issues and vague translational findings for maximum optimization of the efficacy of stem cell therapy in neurodegenerative diseases. PMID:25624807

  13. Life in the Leaf Litter

    NSDL National Science Digital Library

    Produced by the Center for Biodiversity and Conservation, Life in the Leaf Litter is a guide to the diversity of soil organisms and the crucial role that invertebrates play in woodland ecosystems. The booklet was based, in part, on a leaf litter survey conducted by the CBC's Metro Program and the Museum's Division of Invertebrate Zoology in Central Park's woodlands, which led to the discovery of a new genus and species of centipede, Nannarrup hoffmani. The booklet may be downloaded as a pdf or ordered free of charge.

  14. Biophysical control of leaf temperature

    NASA Astrophysics Data System (ADS)

    Dong, N.; Prentice, I. C.; Wright, I. J.

    2014-12-01

    In principle sunlit leaves can maintain their temperatures within a narrower range than ambient temperatures. This is an important and long-known (but now overlooked) prediction of energy balance theory. Net radiation at leaf surface in steady state (which is reached rapidly) must be equal to the combination of sensible and latent heat exchanges with surrounding air, the former being proportional to leaf-to-air temperature difference (?T), the latter to the transpiration rate. We present field measurements of ?T which confirm the existence of a 'crossover temperature' in the 25-30?C range for species in a tropical savanna and a tropical rainforest environment. This finding is consistent with a simple representation of transpiration as a function of net radiation and temperature (Priestley-Taylor relationship) assuming an entrainment factor (?) somewhat greater than the canonical value of 0.26. The fact that leaves in tropical forests are typically cooler than surrounding air, often already by solar noon, is consistent with a recently published comparison of MODIS day-time land-surface temperatures with air temperatures. Theory further predicts a strong dependence of leaf size (which is inversely related to leaf boundary-layer conductance, and therefore to absolute magnitude of ?T) on moisture availability. Theoretically, leaf size should be determined by either night-time constraints (risk of frost damage to active leaves) or day-time constraints (risk of heat stress damage),with the former likely to predominate - thereby restricting the occurrence of large leaves - at high latitudes. In low latitudes, daytime maximum leaf size is predicted to increase with temperature, provided that water is plentiful. If water is restricted, however, transpiration cannot proceed at the Priestley-Taylor rate, and it quickly becomes advantageous for plants to have small leaves, which do not heat up much above the temperature of their surroundings. The difference between leaf and air temperature is generally neglected in terrestrial ecosystem and carbon cycle models. This is a significant omission that could lead to an over-estimation of the heat-stress vulnerability of carbon uptake in the wet tropics. Leaf energy balance theory is well established, and should be included in the next generation of models.

  15. SEMI-ROLLED LEAF1 Encodes a Putative Glycosylphosphatidylinositol-Anchored Protein and Modulates Rice Leaf Rolling by Regulating the Formation of Bulliform Cells1[W][OA

    PubMed Central

    Xiang, Jing-Jing; Zhang, Guang-Heng; Qian, Qian; Xue, Hong-Wei

    2012-01-01

    Leaf rolling is an important agronomic trait in rice (Oryza sativa) breeding and moderate leaf rolling maintains the erectness of leaves and minimizes shadowing between leaves, leading to improved photosynthetic efficiency and grain yields. Although a few rolled-leaf mutants have been identified and some genes controlling leaf rolling have been isolated, the molecular mechanisms of leaf rolling still need to be elucidated. Here we report the isolation and characterization of SEMI-ROLLED LEAF1 (SRL1), a gene involved in the regulation of leaf rolling. Mutants srl1-1 (point mutation) and srl1-2 (transferred DNA insertion) exhibit adaxially rolled leaves due to the increased numbers of bulliform cells at the adaxial cell layers, which could be rescued by complementary expression of SRL1. SRL1 is expressed in various tissues and is expressed at low levels in bulliform cells. SRL1 protein is located at the plasma membrane and predicted to be a putative glycosylphosphatidylinositol-anchored protein. Moreover, analysis of the gene expression profile of cells that will become epidermal cells in wild type but probably bulliform cells in srl1-1 by laser-captured microdissection revealed that the expression of genes encoding vacuolar H+-ATPase (subunits A, B, C, and D) and H+-pyrophosphatase, which are increased during the formation of bulliform cells, were up-regulated in srl1-1. These results provide the transcript profile of rice leaf cells that will become bulliform cells and demonstrate that SRL1 regulates leaf rolling through inhibiting the formation of bulliform cells by negatively regulating the expression of genes encoding vacuolar H+-ATPase subunits and H+-pyrophosphatase, which will help to understand the mechanism regulating leaf rolling. PMID:22715111

  16. UW Summer STEM Undergraduate

    E-print Network

    Kaminsky, Werner

    UW Summer STEM Undergraduate Research Poster SessionWednesday, August 21st, 2013 9:00 am--12 noon to conduct research in STEM fields. For more information, contact the Undergraduate Research Program at: urp

  17. Choosing a STEM Career

    NSDL National Science Digital Library

    2009-11-10

    Students will view video clips about graduate and middle school students with interests in STEM careers and compare technologies from yesterday with today. They will explore careers on-line before writing about their futures as STEM professionals.

  18. Stem Cell Information: Glossary

    MedlinePLUS

    ... medicine Reproductive cloning Signals Somatic cell Somatic cell nuclear transfer (SCNT) Somatic (adult) stem cell Stem cells ... refer to an animal produced by somatic cell nuclear transfer (SCNT) or parthenogenesis . Cloning —See Clone . Cord ...

  19. Effects of drought stress on photosynthetic gas exchange, chlorophyll fluorescence and stem diameter of soybean plants

    Microsoft Academic Search

    Y. Ohashi; N. Nakayama; H. Saneoka; K. Fujita

    2006-01-01

    Changes in plant growth, photosynthetic gas exchange, chlorophyll fluorescence and stem diameter of soybean [Glycine max (L.) Merr.] plants under drought stress were studied. Total plant dry mass was reduced by 30 % compared to well-watered control\\u000a plants. Leaf water potential was slightly decreased by water stress. Water stress induced daytime shrinkage and reduced night-time\\u000a expansion of stem. Photosynthetic rate,

  20. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 2012-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

  1. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 2014-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

  2. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 2013-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

  3. Cord Blood Stem Cells for Hematopoietic Transplantation

    Microsoft Academic Search

    Anfisa Stanevsky; Avichai Shimoni; Ronit Yerushalmi; Arnon Nagler

    2011-01-01

    Cord blood (CB) is an important alternative source of hematopoietic stem cells (HSCs) for transplantation today. The principal\\u000a drawbacks of cord blood transplantation are the limited number of hematopoietic stem cells and a long time to engraftment.\\u000a Several promising approaches for engraftment enhancement are under intensive investigation. Such are transplantation with\\u000a two cord blood units, co transplantation of cord blood

  4. Therapeutic Approaches to Target Cancer Stem Cells

    Microsoft Academic Search

    Lisa R. Rogers; Maxs Wicha

    \\u000a Cancer stem cells (CSCs) have been identified in hematologic malignancies as well as a number of solid tumors. Among solid\\u000a tumors, the isolation and characterization of the tumorigenicity and signaling pathways of CSCs have been studied most thoroughly\\u000a in brain and breast cancers. These tumor types share similar normal stem cell and oncogenic regulatory pathways and will be\\u000a the focus

  5. An Innovative Way to Monitor Leaf Age

    NASA Astrophysics Data System (ADS)

    Garnello, A.; Paredes, K.; Trinh, U.; Saleska, S. R.; Wu, J.

    2013-12-01

    Anthony John Garnello, Karina Paredes, Uyen Khanh Ho Trinh, Jin Wu, Scott Saleska Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA Abstract: Leaf age is an important characteristic for controlling plant functional performance and is associated with the changes of leaf physical, chemical, and physiological properties. Understanding how plant physiology changes over time will allow more accurate predictions of growth patterns, and a more comprehensive understanding of vegetative life histories. There still lacks an efficient technique in monitoring leaf age, tagging leaves is still the only way to accurately monitor leaf age. The goal of this study is to develop a multi-metric, accurate technique for better monitoring of leaf age. In order to acquire true leaf age records, 10 individual plant species were selected at the University of Arizona campus, and newly flushing leaves were tagged and monitored during the Monsoon season (from early June, 2013, to mid October, 2013). Every 2 weeks, 10 to 15 leaves in relative age order were harvested from each 1-meter branch to measure multiple key leaf metrics, including leaf thickness (via micrometer), fresh and dry weight, fresh and dry area (via ImageJ software), and leaf hyperspectral reflectance (via a handheld ASD Field Pro). Other leaf traits were also derived from our measurements, such as specific leaf area (SLA), leaf density (fresh weight/leaf volume), water percentage, and shrinkage ratio (1-dry area/fresh area). The hyperspectral version of vegetation index (a ratio derived from two spectral channels) was generated for each branch sample, by randomly selecting two channels from within the spectral domain of 350 nm to 2500 nm. The preliminary result documents three types of hyperspectral vegetation index (VI) which are highly related with leaf relative age order (R2>0.9). These include the sensitive spectral domains correlated with (a) leaf pigments (~550nm) and leaf physical structure (750nm-1000nm), (b) leaf pigments (~550nm) and leaf water concentration (1400nm-2300nm), and (c) leaf physical structure (750nm-1000nm) and leaf water concentration (1400nm-2300nm). Preliminary results showed that (1) among the key leaf traits, leaf shrinkage is the only trait that showed a consistent correlation with relative age order across the samples; (2) a power function best modeled the interspecies relationship between leaf shrinkage and leaf age (R2 = 0.81, p-value < 0.01, 22 data points for 7 species); (3) a strong correlation was found between the predicted leaf age using the species specific power functions of leaf shrinkage and true leaf age (R2= 0.96, p-value < 0.01), suggesting that leaf shrinkage could be a useful trait for prediction of absolute leaf age in the future. In the next step, we will integrate leaf shrinkage based leaf age prediction with hyperspectral VI framework, aiming to derive some reliable VIs which can be universal for leaf aging prediction among all the species.

  6. Umbilical Cord Stem Cells

    Microsoft Academic Search

    Kathy E. Mitchell

    The two most basic properties of stem cells are the capacities to self-renew and to differentiate into multiple cell or tissue\\u000a types (1–3). Generally, stem cells are categorized as one of three types: embryonic stem cells (ES), embryonic germ cells (EG), or adult\\u000a stem cells. ES cells are derived from the inner cell mass of the blastula (Fig. 1). They

  7. The scaling of leaf area and mass: the cost of light interception increases with leaf size

    E-print Network

    Minnesota, University of

    The scaling of leaf area and mass: the cost of light interception increases with leaf size Rube (specific leaf area, SLA) is a key trait from physiological, ecological and biophysical perspectives. To address whether SLA declines with leaf size, as hypothesized due to increasing costs of support in larger

  8. Relationships between sugarcane leaf hyperspectral reflectance, leaf nitrogen content, and yield components

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leaf spectral reflectance has been used to estimate crop leaf chemical composition and other physiological characters. Leaf reflectance of sugarcane (Saccharum spp.) may be of use in evaluating genotypes. The objectives of this study were: (1) to identify sugarcane genotypic variation in leaf hypers...

  9. STEM Bridge Scholarship Program

    E-print Network

    Buehrer, R. Michael

    2015-2016 STEM Bridge Scholarship Program Virginia Space Grant Consortium (VSGC) provides renewable STEM Bridge Scholarships of $1,000 to sophomore students from any federally recognized minority group enrolled full-time in a program of study in science, technology, engineering, or math (STEM) at one

  10. Understanding Embryonic Stem Cells

    NSDL National Science Digital Library

    Douglas A. Melton, Ph.D. (Howard Hughes Medical Institute; )

    2008-04-10

    This indexed webcast video along with synchronized lecture slides is from Howard Hughes Medical Institute's 2006 Holiday LecturesPotent Biology: Stem Cells, Cloning, and Regeneration. Douglas A. Melton presents an introduction to stem cells, as well as answers to questions about the role of stem cells in the human body. This video requires RealPlayer 10.

  11. AGO1 defines a novel locus of Arabidopsis controlling leaf development

    Microsoft Academic Search

    Karen Bohmert; Isabelle Camus; Catherine Bellini; David Bouchez

    1998-01-01

    An allelic series of the novel argonaute mutant (ago1-1 to ago1-6) of the herbaceous plant Arabidopsis thaliana has been isolated. The ago1 mutation pleotropically affects general plant architecture. The apical shoot meristem generates rosette leaves and a single stem, but axillary meristems rarely develop. Rosette leaves lack a leaf blade but still show adaxial\\/abaxial differen- tiation. Instead of cauline leaves,

  12. iSTEM Summer Institute: An Integrated Approach to Teacher Professional Development inSTEM

    SciTech Connect

    Anne Seifert; Louis Nadelson

    2012-04-01

    The importance of STEM education to our national prosperity and global competitiveness was recently reinforced by the Obama administration support for Change the Equation. Change the Equation is a multi-entity initiative formed in response to the rapidly increasing demand for STEM related careers and the potential lack of preparation by many Americans to be employed in these positions. To address the issue many are calling for increased emphasis on K-12 STEM education, as early preparation in STEM provides the foundation essential for further learning and competencies (National Research Council, 2007). Achieving and sustaining depth and breadth of K-12 STEM education is inextricably linked to ongoing professional development of K-12 educators. The need for teacher continuing education in STEM education and the link between teacher effectiveness and student preparation in STEM was the impetus behind our i- STEM professional development summer institute. The i-STEM initiative is a collaborative effort between business, industry, government, K-12, and higher education. Although the organization is working on a number of projects, including policy, research, communication, and collaborations, the i-STEM group has directed significant resources toward K-12 educator professional development opportunities in STEM. Our report focuses on the structure and impact of the intensive four-day i-STEM residential professional development institute which we designed to increase the capacity of grade 4-9 teachers to teach STEM content. We structured the summer institute using the outcome of a survey we conducted of grade 4-9 teachers’ to assess their STEM professional development needs, the extant literature on teacher development, the increasing need for a STEM informed society, and our desire to use evidence based practices to enhance teacher capacity to teach STEM content. We developed this investigation to determine if our summer institute influenced the participating teachers comfort with teaching STEM, efficacy for teaching STEM, content knowledge of STEM, inquiry implementation in STEM, and perceptions of STEM education. These parameters in-part have been gathered previously for specific areas of math or science education, but we are not aware of any study in which these variables have been attended to and assessed in the context of enhancing inservice teacher preparation to teach STEM. Therefore, our project provides a unique contribution to the literature because of our focus on STEM education and our adaptation and use of an array of assessment tools to measure the impact on our participants’ perceptions of teaching STEM, affective perspectives, and knowledge of the related content. Further, we are responding to the position of Putnam and Borko (2000) who contend there has been a dearth of attention paid toward creating teacher professional development experiences consistent with the teacher learning and investigations of the impact of the experience on the participating educators. Before we present our research and results, we discuss the relevant literature establishing the justification for our study. Following the presentation of our study results we discuss the related implications and directions for future research. We conclude with a discussion of study limitations and some closing remarks of our study contributions to the field of teacher professional development in STEM education.

  13. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture...Tobacco (u.s. Type 21) § 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  14. 7 CFR 29.2278 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2 2012-01-01 2012-01-01 false Leaf structure. 29.2278 Section 29.2278...Fire-Cured Tobacco (u.s. Type 21) § 29.2278 Leaf structure. The cell development of a leaf as indicated by its porosity. (See...

  15. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture...36, 37 and Foreign Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

  16. 7 CFR 29.2278 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2 2013-01-01 2013-01-01 false Leaf structure. 29.2278 Section 29.2278...Fire-Cured Tobacco (u.s. Type 21) § 29.2278 Leaf structure. The cell development of a leaf as indicated by its porosity. (See...

  17. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture...Type 31 and Foreign Type 93) § 29.3034 Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  18. Leaf Sequencing Algorithms for Segmented Multileaf Collimation

    E-print Network

    Sahni, Sartaj K.

    Leaf Sequencing Algorithms for Segmented Multileaf Collimation Srijit Kamath, Sartaj Sahni fluence map into a leaf sequence file that controls the movement of the MLC during radiation delivery. It is imperative that the fluence map delivered using the leaf sequence file is as close as possible to the fluence

  19. 7 CFR 29.2278 - Leaf structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2 2014-01-01 2014-01-01 false Leaf structure. 29.2278 Section 29.2278...Fire-Cured Tobacco (u.s. Type 21) § 29.2278 Leaf structure. The cell development of a leaf as indicated by its porosity. (See...

  20. Parameterized Algorithms for Directed Maximum Leaf Problems

    E-print Network

    Krivelevich, Michael

    Parameterized Algorithms for Directed Maximum Leaf Problems Noga Alon 1 , Fedor V. Fomin 2 spanning tree, then D contains one with at least (n/2) 1/5 - 1 leaves. 1 Introduction The Maximum Leaf a digraph D, the Directed Maximum Leaf Out­Branching problem is the problem of finding an out­branching in D

  1. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture...Tobacco (u.s. Type 21) § 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  2. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture...Type 31 and Foreign Type 93) § 29.3034 Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  3. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture...Tobacco (u.s. Type 21) § 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  4. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture...36, 37 and Foreign Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

  5. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture...Type 31 and Foreign Type 93) § 29.3034 Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed...

  6. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture...36, 37 and Foreign Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed...

  7. Exobasidium leaf and fruit spot

    Technology Transfer Automated Retrieval System (TEKTRAN)

    During the past five or so years blueberry growers in south Mississippi have discovered the disease Exobasidium leaf and fruit spot on some of their blueberry plants. In the past this disease was considered to be of minor importance occurring infrequently on isolated farms. But in recent years it ...

  8. XANTHOMONAS LEAF BLIGHT OF ONION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Xanthomonas leaf blight, caused by the bacterium Xanthomonas axonopodis pv. allii, is a common foliar disease of onion. This extension bulletin presents a review of disease symptomology, etiology, epidemiology, and management. The association of environment, host, and cultural and disease severity ...

  9. Leaf Photosynthesis Under Drought Stress

    Microsoft Academic Search

    Gabriel Cornic; Angelo Massacci

    The photosynthetic apparatus is resistant to drought. Net CO2 uptake of a leaf submitted to a mild desiccation decreases because of stomatal closure. As aresult, CO2 concentration in the chloroplast decreases in plants exposed to water shortage. This drop in the chloroplast CO2 concentration causes: (i) a decrease in photochemical yield of open PS II centers and, consequently, an increase

  10. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...percent may be waste. B4G—Fair Quality Green Leaf Immature, close leaf structure...percent may be waste. B5G—Low Quality Green Leaf Immature, tight leaf structure...percent may be waste. B6G—Poor Quality Green Leaf Immature, tight leaf...

  11. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...percent may be waste. B4G—Fair Quality Green Leaf Immature, close leaf structure...percent may be waste. B5G—Low Quality Green Leaf Immature, tight leaf structure...percent may be waste. B6G—Poor Quality Green Leaf Immature, tight leaf...

  12. Stem Cell Quick Guide: Stem Cell Basics What is a Stem Cell?

    E-print Network

    Schladow, S. Geoffrey

    Stem Cell Quick Guide: Stem Cell Basics What is a Stem Cell? Stem cells are the starting point from to line blood vessels. All of these highly specialized cells have to grow from unspecialized stem cells. Stem cells produce new cells by dividing. In the right conditions, these new cells can then continue

  13. Algorithm for retrieving vegetative canopy and leaf parameters from multi- and hyperspectral imagery

    NASA Astrophysics Data System (ADS)

    Borel, Christoph

    2009-05-01

    In recent years hyper-spectral data has been used to retrieve information about vegetative canopies such as leaf area index and canopy water content. For the environmental scientist these two parameters are valuable, but there is potentially more information to be gained as high spatial resolution data becomes available. We developed an Amoeba (Nelder-Mead or Simplex) based program to invert a vegetative canopy radiosity model coupled with a leaf (PROSPECT5) reflectance model and modeled for the background reflectance (e.g. soil, water, leaf litter) to a measured reflectance spectrum. The PROSPECT5 leaf model has five parameters: leaf structure parameter Nstru, chlorophyll a+b concentration Cab, carotenoids content Car, equivalent water thickness Cw and dry matter content Cm. The canopy model has two parameters: total leaf area index (LAI) and number of layers. The background reflectance model is either a single reflectance spectrum from a spectral library() derived from a bare area pixel on an image or a linear mixture of soil spectra. We summarize the radiosity model of a layered canopy and give references to the leaf/needle models. The method is then tested on simulated and measured data. We investigate the uniqueness, limitations and accuracy of the retrieved parameters on canopy parameters (low, medium and high leaf area index) spectral resolution (32 to 211 band hyperspectral), sensor noise and initial conditions.

  14. Molecular diversity of Cotton leaf curl Gezira virus isolates and their satellite DNAs associated with okra leaf curl disease in Burkina Faso

    PubMed Central

    2010-01-01

    Okra leaf curl disease (OLCD) is a major constraint on okra (Abelmoschus esculentus) production and is widespread in Africa. Using a large number of samples representative of the major growing regions in Burkina Faso (BF), we show that the disease is associated with a monopartite begomovirus and satellite DNA complexes. Twenty-three complete genomic sequences of Cotton leaf curl Gezira virus (CLCuGV) isolates associated with OLCD, sharing 95 to 99% nucleotide identity, were cloned and sequenced. Six betasatellite and four alphasatellite (DNA-1) molecules were also characterized. The six isolates of betasatellite associated with CLCuGV isolates correspond to Cotton leaf curl Gezira betasatellite (CLCuGB) (88 to 98% nucleotide identity). One isolate of alphasatellite is a variant of Cotton leaf curl Gezira alphasatellite (CLCuGA) (89% nucleotide identity), whereas the three others isolates appear to correspond to a new species of alphasatellite (CLCuGA most similar sequence present 52 to 60% nucleotide identity), provisionally named Okra leaf curl Burkina Faso alphasatellite (OLCBFA). Recombination analysis of the viruses demonstrated the interspecies recombinant origin of all CLCuGV isolates, with parents being close to Hollyhock leaf crumple virus (AY036009) and Tomato leaf curl Diana virus (AM701765). Combined with the presence of satellites DNA, these results highlight the complexity of begomoviruses associated with OLCD. PMID:20178575

  15. Leaf area dynamics of conifer forests

    SciTech Connect

    Margolis, H.; Oren, R.; Whitehead, D.; Kaufmann, M.R.

    1995-07-01

    Estimating the surface area of foliage supported by a coniferous forest canopy is critical for modeling its biological properties. Leaf area represents the surface area available for the interception of energy, the absorption of carbon dioxide, and the diffusion of water from the leaf to the atmosphere. The concept of leaf area is pertinent to the physiological and ecological dynamics of conifers at a wide range of spatial scales, from individual leaves to entire biomes. In fact, the leaf area of vegetation at a global level can be thought of as a carbon-absorbing, water-emitting membrane of variable thickness, which can have an important influence on the dynamics and chemistry of the Earth`s atmosphere over both the short and the long term. Unless otherwise specified, references to leaf area herein refer to projected leaf area, i.e., the vertical projection of needles placed on a flat plane. Total leaf surface area is generally from 2.0 to 3.14 times that of projected leaf area for conifers. It has recently been suggested that hemisurface leaf area, i.e., one-half of the total surface area of a leaf, a more useful basis for expressing leaf area than is projected area. This chapter is concerned with the dynamics of coniferous forest leaf area at different spatial and temporal scales. In the first part, we consider various hypotheses related to the control of leaf area development, ranging from simple allometric relations with tree size to more complex mechanistic models that consider the movement of water and nutrients to tree canopies. In the second part, we consider various aspects of leaf area dynamics at varying spatial and temporal scales, including responses to perturbation, seasonal dynamics, genetic variation in crown architecture, the responses to silvicultural treatments, the causes and consequences of senescence, and the direct measurement of coniferous leaf area at large spatial scales using remote sensing.

  16. Effect of light and gibberellic acid on cell division in the first foliage leaf of durum wheat ( Triticum durum Desf.)

    Microsoft Academic Search

    S. Baroncelli; A. Cavallini; B. Lercari; P. G. Cionini; F. D'Amato

    1988-01-01

    The present paper is part of a research program which aims at a quantitative analysis of the effects of light and gibberellic acid (GA3) on growth of the first foliage leaf in durum wheat (Triticum durum Desf.). Since leaf growth is the combined result of the increase in cell number (cell division) and cell enlargement, the influence of light and

  17. Leaf hairs influence phytopathogenic fungus infection and confer an increased resistance when expressing a Trichoderma  -1,3-glucanase

    Microsoft Academic Search

    Leticia Calo; Irene Garcia; Cecilia Gotor; Luis C. Romero

    2006-01-01

    The leaf surface of a very large number of plant species are covered by trichomes. Non-glandular trichomes are specialized unicellular or multicellular structures that occur in many different plant species and function in xenobiotic detoxification and protecting the plant against pest attack. By analysing the susceptibility of trichome mutants, evidence is provided that indicates the influence of leaf trichomes on

  18. Time to Reconsider Stem Cell Induction Strategies

    PubMed Central

    Denker, Hans-Werner

    2012-01-01

    Recent developments in stem cell research suggest that it may be time to reconsider the current focus of stem cell induction strategies. During the previous five years, approximately, the induction of pluripotency in somatic cells, i.e., the generation of so-called ‘induced pluripotent stem cells’ (iPSCs), has become the focus of ongoing research in many stem cell laboratories, because this technology promises to overcome limitations (both technical and ethical) seen in the production and use of embryonic stem cells (ESCs). A rapidly increasing number of publications suggest, however, that it is now possible to choose instead other, alternative ways of generating stem and progenitor cells bypassing pluripotency. These new strategies may offer important advantages with respect to ethics, as well as to safety considerations. The present communication discusses why these strategies may provide possibilities for an escape from the dilemma presented by pluripotent stem cells (self-organization potential, cloning by tetraploid complementation, patenting problems and tumor formation risk). PMID:24710555

  19. HLA Association with Hematopoietic Stem Cell Transplantation Outcome: The Number of Mismatches at HLA-A, B, -C, -DRB1, or -DQB1 Is Strongly Associated with Overall Survival

    Microsoft Academic Search

    Pascale Loiseau; Marc Busson; Marie-Lorraine Balere; Anne Dormoy; Jean-Denis Bignon; Katia Gagne; Lucette Gebuhrer; Valérie Dubois; Isabelle Jollet; Monique Bois; Pascale Perrier; Dominique Masson; Agnès Moine; Léna Absi; Denis Reviron; Virginia Lepage; Ryad Tamouza; Antoine Toubert; Evelyne Marry; Zina Chir; Jean-Pierre Jouet; Didier Blaise; Dominique Charron; Colette Raffoux

    2007-01-01

    HLA matching between the donor and recipient improves the success of unrelated hematopoietic stem cell transplantation (HSCT). Because many patients in need of an unrelated transplant have only donors with mismatch, information is needed to evaluate the limits of HLA mismatching. We examined the association of survival, acute graft-versus-host disease (aGVHD) and relapse with HLA-A, -B, -C, -DRB, -DQB1, and

  20. Tumor Angiogenesis and the Cancer Stem Cell Model

    Microsoft Academic Search

    Chris Folkins; Robert S. Kerbel

    In recent years, research and interest in the area of cancer stem cells has grown tremendously. An increasing number of studies\\u000a are finding that many different cancers contain a subpopulation of tumor cells that display several defining characteristics\\u000a of adult tissue stem cells, including multipotent differentiation potential, long-term self-renewal capacity, and the expression\\u000a of various molecular markers of stemness. Most

  1. Mobilization of Stem Cells\\/Progenitor Cells by Physical Activity

    Microsoft Academic Search

    Patrick Wahl; Wilhelm Bloch

    \\u000a A number of publications have provided evidence that exercise and physical activity are linked to the activation, mobilization,\\u000a and differentiation of various types of stem cells. Exercise may improve organ regeneration and function. This review characterizes\\u000a different stem and progenitor cells and their sources and summarizes mechanisms by which exercise contributes to stem-cell-induced\\u000a regeneration and adaptation in different tissues. The

  2. Reducing mammary cancer risk through premature stem cell senescence

    Microsoft Academic Search

    Corinne A Boulanger; Gilbert H Smith

    2001-01-01

    The reproductive capacity of the mammary epithelial stem cell is reduced coincident with the number of symmetric divisions it must perform. In a study of FVB\\/N mice with the transgene, WAP-TGF?1, we discovered that mammary epithelial stem cells were prematurely aged due to ectopic expression of TGF-?1. To test whether premature aging of mammary epithelial stem cells would have an

  3. Dnmt3a is essential for hematopoietic stem cell differentiation

    Microsoft Academic Search

    Grant A Challen; Deqiang Sun; Mira Jeong; Min Luo; Jaroslav Jelinek; Jonathan S Berg; Christoph Bock; Aparna Vasanthakumar; Hongcang Gu; Yuanxin Xi; Shoudan Liang; Yue Lu; Gretchen J Darlington; Alexander Meissner; Jean-Pierre J Issa; Lucy A Godley; Wei Li; Margaret A Goodell

    2011-01-01

    Loss of the de novo DNA methyltransferases Dnmt3a and Dnmt3b in embryonic stem cells obstructs differentiation; however, the role of these enzymes in somatic stem cells is largely unknown. Using conditional ablation, we show that Dnmt3a loss progressively impairs hematopoietic stem cell (HSC) differentiation over serial transplantation, while simultaneously expanding HSC numbers in the bone marrow. Dnmt3a-null HSCs show both

  4. Isotopic characteristics of canopies in simulated leaf assemblages

    NASA Astrophysics Data System (ADS)

    Graham, Heather V.; Patzkowsky, Mark E.; Wing, Scott L.; Parker, Geoffrey G.; Fogel, Marilyn L.; Freeman, Katherine H.

    2014-11-01

    The geologic history of closed-canopy forests is of great interest to paleoecologists and paleoclimatologists alike. Closed canopies have pronounced effects on local, continental and global rainfall and temperature patterns. Although evidence for canopy closure is difficult to reconstruct from the fossil record, the characteristic isotope gradients of the "canopy effect" could be preserved in leaves and proxy biomarkers. To assess this, we employed new carbon isotopic data for leaves collected in diverse light environments within a deciduous, temperate forest (Maryland, USA) and for leaves from a perennially closed canopy, moist tropical forest (Bosque Protector San Lorenzo, Panamá). In the tropical forest, leaf carbon isotope values range 10‰, with higher ?13Cleaf values occurring both in upper reaches of the canopy, and with higher light exposure and lower humidity. Leaf fractionation (?leaf) varied negatively with height and light and positively with humidity. Vertical 13C enrichment in leaves largely reflects changes in ?leaf, and does not trend with ?13C of CO2 within the canopy. At the site in Maryland, leaves express a more modest ?13C range (?6‰), with a clear trend that follows both light and leaf height. Using a model we simulate leaf assemblage isotope patterns from canopy data binned by elevation. The re-sampling (bootstrap) model determined both the mean and range of carbon isotope values for simulated leaf assemblages ranging in size from 10 to over 1000 leaves. For the tropical forest data, the canopy's isotope range is captured with 50 or more randomly sampled leaves. Thus, with a sufficient number of fossil leaves it is possible to distinguish isotopic gradients in an ancient closed canopy forest from those in an open forest. For very large leaf assemblages, mean isotopic values approximate the ?13C of carbon contributed by leaves to soil and are similar to observed ?13Clitter values at forested sites within Panamá, including the site where leaves were sampled. The model predicts a persistent ?1‰ difference in ?13Clitter for the two sites which is consistent with higher water availability in the tropical forests. This work provides a new framework for linking contemporary ecological observations to the geochemical record using flux-weighted isotope data and lends insights to the effect of forest architecture on organic and isotopic records of ancient terrestrial ecosystems.

  5. The relationship of leaf photosynthetic traits – Vcmax and Jmax – to leaf nitrogen, leaf phosphorus, and specific leaf area: a meta-analysis and modeling study

    PubMed Central

    Walker, Anthony P; Beckerman, Andrew P; Gu, Lianhong; Kattge, Jens; Cernusak, Lucas A; Domingues, Tomas F; Scales, Joanna C; Wohlfahrt, Georg; Wullschleger, Stan D; Woodward, F Ian

    2014-01-01

    Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (Vcmax) and the maximum rate of electron transport (Jmax). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between Vcmax and Jmax and leaf nitrogen (N) are typically derived from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between Vcmax and Jmax and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of Vcmax and Jmax with leaf N, P, and SLA. Vcmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of Vcmax to leaf N. Jmax was strongly related to Vcmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm?2), increasing leaf P from 0.05 to 0.22 gm?2 nearly doubled assimilation rates. Finally, we show that plants may employ a conservative strategy of Jmax to Vcmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting. PMID:25473475

  6. The relationship of leaf photosynthetic traits - V cmax and J max - to leaf nitrogen, leaf phosphorus, and specific leaf area: a meta-analysis and modeling study.

    PubMed

    Walker, Anthony P; Beckerman, Andrew P; Gu, Lianhong; Kattge, Jens; Cernusak, Lucas A; Domingues, Tomas F; Scales, Joanna C; Wohlfahrt, Georg; Wullschleger, Stan D; Woodward, F Ian

    2014-08-01

    Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (V cmax) and the maximum rate of electron transport (J max). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between V cmax and J max and leaf nitrogen (N) are typically derived from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between V cmax and J max and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of V cmax and J max with leaf N, P, and SLA. V cmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of V cmax to leaf N. J max was strongly related to V cmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm(-2)), increasing leaf P from 0.05 to 0.22 gm(-2) nearly doubled assimilation rates. Finally, we show that plants may employ a conservative strategy of J max to V cmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting. PMID:25473475

  7. Neural stem cells: Brain building blocks and beyond

    PubMed Central

    Bergström, Tobias

    2012-01-01

    Neural stem cells are the origins of neurons and glia and generate all the differentiated neural cells of the mammalian central nervous system via the formation of intermediate precursors. Although less frequent, neural stem cells persevere in the postnatal brain where they generate neurons and glia. Adult neurogenesis occurs throughout life in a few limited brain regions. Regulation of neural stem cell number during central nervous system development and in adult life is associated with rigorous control. Failure in this regulation may lead to e.g. brain malformation, impaired learning and memory, or tumor development. Signaling pathways that are perturbed in glioma are the same that are important for neural stem cell self-renewal, differentiation, survival, and migration. The heterogeneity of human gliomas has impeded efficient treatment, but detailed molecular characterization together with novel stem cell-like glioma cell models that reflect the original tumor gives opportunities for research into new therapies. The observation that neural stem cells can be isolated and expanded in vitro has opened new avenues for medical research, with the hope that they could be used to compensate the loss of cells that features in several severe neurological diseases. Multipotent neural stem cells can be isolated from the embryonic and adult brain and maintained in culture in a defined medium. In addition, neural stem cells can be derived from embryonic stem cells and induced pluripotent stem cells by in vitro differentiation, thus adding to available models to study stem cells in health and disease. PMID:22512245

  8. Leaf hydraulic conductance is coordinated with leaf morpho-anatomical traits and nitrogen status in the genus Oryza.

    PubMed

    Xiong, Dongliang; Yu, Tingting; Zhang, Tong; Li, Yong; Peng, Shaobing; Huang, Jianliang

    2015-02-01

    Leaf hydraulic conductance (K leaf) is a major determinant of photosynthetic rate in plants. Previous work has assessed the relationships between leaf morpho-anatomical traits and K leaf with woody species, but there has been very little focus on cereal crops. The genus Oryza, which includes rice (Oryza sativa) and wild species (such as O. rufipogon cv. Griff), is ideal material for identifying leaf features associated with K leaf and gas exchange. Leaf morpho-anatomical traits, K leaf, leaf N content per leaf area, and CO2 diffusion efficiency were investigated in 11 Oryza cultivars. K leaf was positively correlated with leaf thickness and related traits, and therefore positively correlated with leaf mass per area and leaf N content per leaf area, and negatively with inter-veinal distance. K leaf was also positively correlated with leaf area and its related traits, and therefore negatively correlated with the proportion of minor vein length per area. In addition, coordination between K leaf and CO2 diffusion conductance in leaves was observed. We conclude that leaf morpho-anatomical traits and N content per leaf area strongly influence K leaf. Our results suggest that more detailed anatomical and structural studies are needed to elucidate the impacts of leaf feature traits on K leaf and gas exchange in grasses. PMID:25429002

  9. Leaf hydraulic conductance is coordinated with leaf morpho-anatomical traits and nitrogen status in the genus Oryza

    PubMed Central

    Xiong, Dongliang; Yu, Tingting; Zhang, Tong; Li, Yong; Peng, Shaobing; Huang, Jianliang

    2015-01-01

    Leaf hydraulic conductance (K leaf) is a major determinant of photosynthetic rate in plants. Previous work has assessed the relationships between leaf morpho-anatomical traits and K leaf with woody species, but there has been very little focus on cereal crops. The genus Oryza, which includes rice (Oryza sativa) and wild species (such as O. rufipogon cv. Griff), is ideal material for identifying leaf features associated with K leaf and gas exchange. Leaf morpho-anatomical traits, K leaf, leaf N content per leaf area, and CO2 diffusion efficiency were investigated in 11 Oryza cultivars. K leaf was positively correlated with leaf thickness and related traits, and therefore positively correlated with leaf mass per area and leaf N content per leaf area, and negatively with inter-veinal distance. K leaf was also positively correlated with leaf area and its related traits, and therefore negatively correlated with the proportion of minor vein length per area. In addition, coordination between K leaf and CO2 diffusion conductance in leaves was observed. We conclude that leaf morpho-anatomical traits and N content per leaf area strongly influence K leaf. Our results suggest that more detailed anatomical and structural studies are needed to elucidate the impacts of leaf feature traits on K leaf and gas exchange in grasses. PMID:25429002

  10. The serrate leaf margined Juniperus (Section Sabina) of the western hemisphere: systematics and evolution based on leaf essential oils and Random Amplified Polymorphic DNAs (RAPDs).

    PubMed

    Adams

    2000-12-01

    The volatile leaf essential compositions of all 17 serrate leaf margin species of Juniperus (sect. Sabina) of the western hemisphere are reported and compared: J. angosturana, J. ashei, J. californica, J. coahuilensis, J. comitana, J. deppeana, J. durangensis, J. flaccida, J. gamboana, J. jaliscana, J. monosperma, J. monticola, J. osteosperma, J. occidentalis, J. pinchotii, J. saltillensis, and J. standleyi. A number of previously unidentified compounds of the leaf essential oils have now been identified. In addition, DNA data (RAPDs) of all these species were analyzed. Both the leaf essential oils and DNA show these species to be quite distinct with few apparent subgroups, such that the species groupings were not strong in either data set. These data support the hypothesis that this group of junipers originated in Mexico as part of the Madro-Tertiary flora by rapid radiation into new arid land habitats, leaving few extant intermediate taxa. PMID:10996262

  11. MOLECULAR DETECTION OF A CLOSTEROVIRUS ASSOCIATED WITH APRICOT STEM PITTING IN SOUTHERN ITALY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Electrophoretic analysis of cortical and leaf tissue extracts from apricot trees of cv. 'Tyrinthos' from Apulia (southern Italy) affected by stem pitting, contained multiple double-stranded RNA (dsRNA) species, the largest with an estimated size of 15 kbp. A segment of 590 nucleotides, showing seque...

  12. Seeing Stem Cells at Work In Vivo

    PubMed Central

    Srivastava, Amit K.; Bulte, Jeff W. M.

    2013-01-01

    Stem cell based-therapies are novel therapeutic strategies that hold key for developing new treatments for diseases conditions with very few or no cures. Although there has been an increase in the number of clinical trials involving stem cell-based therapies in the last few years, the long-term risks and benefits of these therapies are still unknown. Detailed in vivo studies are needed to monitor the fate of transplanted cells, including their distribution, differentiation, and longevity over time. Advancements in non-invasive cellular imaging techniques to track engrafted cells in real-time present a powerful tool for determining the efficacy of stem cell-based therapies. In this review, we describe the latest approaches to stem cell labeling and tracking using different imaging modalities. PMID:23975604

  13. The PAWS and STEM reliability analysis programs

    NASA Technical Reports Server (NTRS)

    Butler, Ricky W.; Stevenson, Philip H.

    1988-01-01

    The PAWS and STEM programs are new design/validation tools. These programs provide a flexible, user-friendly, language-based interface for the input of Markov models describing the behavior of fault-tolerant computer systems. These programs produce exact solutions of the probability of system failure and provide a conservative estimate of the number of significant digits in the solution. PAWS uses a Pade approximation as a solution technique; STEM uses a Taylor series as a solution technique. Both programs have the capability to solve numerically stiff models. PAWS and STEM possess complementary properties with regard to their input space; and, an additional strength of these programs is that they accept input compatible with the SURE program. If used in conjunction with SURE, PAWS and STEM provide a powerful suite of programs to analyze the reliability of fault-tolerant computer systems.

  14. Cell Stem Cell Dear Student: Stem Cell Scientists' Advice

    E-print Network

    Cell Stem Cell Forum Dear Student: Stem Cell Scientists' Advice to the Next Generation Emily L on Stem Cells in Society, Stanford, CA 94305, USA 2Department of Family Practice, University of British@stanford.edu (C.T.S.) http://dx.doi.org/10.1016/j.stem.2013.05.007 For the field of pluripotent stem cell biology

  15. Original article Compatible stem taper and stem volume functions

    E-print Network

    Boyer, Edmond

    as merchantable vol- ume at any stem diameter along the trunk. Such functions may be used on their ownOriginal article Compatible stem taper and stem volume functions for oak (Quercus robur L and Q - In this paper we develop compatible stem taper and stem volume functions for oak (Quercus robur L and Q petraea

  16. Leaf respiratory acclimation to climate: comparisons among boreal and temperate tree species along a latitudinal transect.

    PubMed

    Dillaway, Dylan N; Kruger, Eric L

    2011-10-01

    In common gardens along an ?900 km latitudinal transect through Wisconsin and Illinois, U.S.A., tree species typical of boreal and temperate forests were compared with respect to the nature and magnitude of leaf respiratory acclimation to contrasting climates. The boreal representatives were trembling aspen (Populus tremuloides Michx.) and paper birch (Betula papyrifera Marsh.), while the temperate species were eastern cottonwood (Populus deltoides Bartr ex. Marsh var. deltoides) and sweetgum (Liquidambar styraciflua L.). Assessments were conducted on seedlings grown from seed sources collected near southern and northern range boundaries, respectively. Nighttime rates of leaf dark respiration (R(d)) at common temperatures, as well as R(d)'s short-term temperature sensitivity (energy of activation, E(o)), were assessed for all species and gardens twice during a growing season. Little evidence of R(d) thermal acclimation was observed, despite a 12 °C range in average air temperature across gardens. Instead, R(d) variation at warm temperatures was linked most closely with prior leaf photosynthetic performance, while R(d) variation at cooler temperatures was most strongly related to leaf nitrogen concentration. Moreover, E(o) differences across species and gardens appeared to stem from the somewhat independent limitations on warm versus cool R(d). Based on this construct, an empirical model relying on R(d) estimates from leaf photosynthesis and nitrogen concentration explained 55% of the observed E(o) variation. PMID:21990024

  17. Leaf orientation and distribution in a Phaseolus vulgaris L. crop and their relation to light microclimate

    NASA Astrophysics Data System (ADS)

    Barradas, V. L.; Jones, H. G.; Clark, Jerry A.

    Changes in canopy structure parameters (leaflet orientation, leaflet inclination and leaf area index) were measured in crops of beans (Phaseolus vulgaris L.) in the field as the canopy developed between July and October. These changes were compared with the corresponding changes in seasonal light transmission. The beans showed clear heliotropic behaviour, with preferential orientation of leaflets towards the sun's beam, especially on sunny days. Nevertheless a significant proportion of the leaves pointed in other directions, with as much as 20% oriented towards the north. The highest proportion of leaf inclinations was in the range 30-40° on cloudy days and between 40° and 50° on sunny days. Two methods were compared for assessing changes in light transmission: (a) the use of a Sunfleck Ceptometer and (b) the use of continuous records obtained with sensors installed in the canopy. Over the growth period studied, the total of the leaf plus stem area indices (LS) increased from 0.26 to 5.2 with the transmission coefficient (?) for photosynthetic photon flux density (PPFD), obtained using the Ceptometer, correspondingly decreasing from 0.72 to 0.05, and the canopy extinction coefficient decreasing from 1.4 to 0.62. The continuous records of light transmission gave generally similar estimates of ?. Some contrasting leaf angle distribution functions were compared for estimation of LS from the light measurements. The best leaf angle function to predict LS from the observed light transmission was a conical function corrected by the degree of heliotropism.

  18. Temporal Isotopic Variations of Leaf Water in Pine Needles

    NASA Astrophysics Data System (ADS)

    Shu, Y.; Feng, X.; Faiia, A. M.

    2005-05-01

    Understanding the isotopic variations in a plant's leaf water is important for a number of climatological and biogeochemical studies. Leaf water isotopic composition is affected by the isotopic composition of the source water and the relative humidity of the air, both of which are related to climate. This dependency is the basis for climate reconstruction using isotopic compositions of tree-ring cellulose. The isotopic composition of leaf water is also important for the assessment of terrestrial biological productivity and the quantification of the Dole effect. We have studied the oxygen and hydrogen isotopic variations in leaf water of biennial needles from red pine (Pinus resinosa) and white pine (Pinus strobes) in Hanover, New Hampshire, USA. We have examined the leaf water ?D and ?18O values along pine needles from base to tip, and the isotopic differences between young and old leaves. Within a needle, progressive enrichments of both oxygen-18 and deuterium were observed toward the tip, ranging for ?D from -60.1 to 9.4 permil in white pine and -67.1 to -34.9 permil in red pine, and for ?18O from -3.1 to 19.1 for white pine and -7.3 to 5.5 permil in red pine. For both species, ?D and ?18O were higher in old leaves than in young leaves. The isotopic difference between old and young leaves was most pronounced earlier in the growing season; the gap narrowed with time and finally disappeared in early fall. Early in the growing season, the ?D values of young needles were -21 and -30 permil in white and red pine, respectively, and that of old needles were -3.0 and -8.0 permil, respectively. The ?18O values showed similar trends, and the ?D vs. ?18O slope for the young leaves decreased from 3.6 in spring to ~1 in early autumn. Our observations can be simulated using the progressive isotopic enrichment model proposed by Barnes and Farquhar for monocotyledoneous leaves. Two variables, the transpiration rate and length of the needle, can explain the observed isotopic variations. These two variables can be combined into one parameter in the model as the longitudinal Peclet number of the leaf. In addition, the model can also explain the change in the slope of the ?D vs. ?18O relationship in leaf water.

  19. Carbon Dioxide Metabolism in Leaf Epidermal Tissue 1

    PubMed Central

    Willmer, C. M.; Pallas, J. E.; Black, C. C.

    1973-01-01

    A number of plant species were surveyed to obtain pure leaf epidermal tissue in quantity. Commelina communis L. and Tulipa gesnariana L. (tulip) were chosen for further work. Chlorophyll a/b ratios of epidermal tissues were 2.41 and 2.45 for C. communis and tulip, respectively. Phosphoenolpyruvate carboxylase, ribulose-1,5-diphosphate carboxylase, malic enzyme, and NAD+ and NADP+ malate dehydrogenases were assayed with epidermal tissue and leaf tissue minus epidermal tissue. In both species, there was less ribulose 1,5-diphosphate than phosphoenolpyruvate carboxylase activity in epidermal tissue whether expressed on a protein or chlorophyll basis whereas the reverse was true for leaf tissue minus epidermal tissue. In both species, malic enzyme activities were higher in epidermal tissue than in the remaining leaf tissue when expressed on a protein or chlorophyll basis. In both species, NAD+ and NADP+ malate dehydrogenase activities were higher in the epidermal tissue when expressed on a chlorophyll basis; however, on a protein basis, the converse was true. Microautoradiography of C. communis epidermis and histochemical tests for keto acids suggested that CO2 fixation occurred predominantly in the guard cells. The significance and possible location of the enzymes are discussed in relation to guard cell metabolism. Images PMID:16658581

  20. 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

  1. [Allogenic stem cell transplantation after non-myeloablative conditioning regimen (mini-allogenic" stem cell transplantation)].

    PubMed

    Milpied, N

    2002-02-01

    Allogeneic stem cell transplantation is able to cure many hematologic malignancies, through, at least partially, a graft versus disease effect of the donor's immune system transfer. However, the toxicity of this technique limits its use to selected patients. The aim of non-myeloablative stem cell transplantation is to reduce the toxicity of the conditioning regimen while allowing the engrafement of donor's stem cells and the immunological antitumoral activity of the donor's immune system. Several reports have already demonstrated the validity of this concept. This new multi-step therapeutic strategy is complex, raises many questions and deserves further studies to be fully applicable to a greater number of patients. PMID:11873629

  2. Stem Cells and Stem Cell-derived Tissues and Their Use in Safety Assessment*

    PubMed Central

    Kolaja, Kyle

    2014-01-01

    Toxicology has long relied on animal models in a tedious approach to understanding risk of exposure to an uncharacterized molecule. Stem cell-derived tissues can be made in high purity, quality, and quantity to enable a new approach to this problem. Currently, stem cell-derived tissues are primarily “generic” genetic backgrounds; the future will see the integration of various genetic backgrounds and complex three-dimensional models to create truly unique in vitro organoids. This minireview focuses on the state of the art of a number of stem cell-derived tissues and details their application in toxicology. PMID:24362027

  3. Morphogenesis of the antenna of the male silkmoth, Antheraea polyphemus. I. The leaf-shaped antenna of the pupa from diapause to apolysis.

    PubMed

    Keil, T A; Steiner, C

    1990-01-01

    The antenna of the male silkmoth Antheraea polyphemus is a featherlike structure consisting of a central stem and ca. 120 side branches, which altogether carry about 70,000 olfactory sensilla. We investigate the development during the pupal phase. At the end of diapause, the antennal rudiment consists of a leaf-shaped, one-layered epidermal sac. It is supplied with oxygen via a central main trachea, which gives off numerous thin side branches. These are segmentally arranged into bundles which run to the periphery of the antennal blade. When the epidermis retracts from the pupal cuticle (apolysis; stage 1), it consists of cells which are morphologically uniform. The epidermal cells form a network of long, irregular basal protrusions (epidermal feet), which crisscross the antennal lumen. During the first day post-apolysis (stage 2), the antennal epidermis differentiates into alternating thick 'sensillogenic' and thin 'non-sensillogenic' areas arranged in stripes which run in parallel to the tracheal bundles. Numerous dark, elongated cells, which might be the sensillar stem cells, are scattered in the sensillogenic epithelium. A number of very early sensilla has been found at the distal edges of the sensillogenic stripes in positions which later will be occupied by sensilla chaetica. The whole antennal blade is enveloped by the transparent ecdysial membrane, consisting of the innermost layers of the pupal cuticle which are detached during apolysis. PMID:18620306

  4. Tracking adult stem cells

    Microsoft Academic Search

    Hugo J Snippert; Hans Clevers

    2011-01-01

    The maintenance of stem-cell-driven tissue homeostasis requires a balance between the generation and loss of cell mass. Adult stem cells have a close relationship with the surrounding tissue—known as their niche—and thus, stem-cell studies should preferably be performed in a physiological context, rather than outside their natural environment. The mouse is an attractive model in which to study adult mammalian

  5. Stem Cell Biology

    Microsoft Academic Search

    Elizabeth O. Hexner; Stephen G. Emerson

    \\u000a Stem cells are functionally defined as long-lived cells that can both self-renew and differentiate into multiple cell types.\\u000a Embryonic stem cells, considered totipotent cells, give rise to all embryonic tissue layers and, consequently, all tissue\\u000a types. Hematologists\\/oncologists are perhaps most familiar with hematopoietic stem cells (HSCs): the single pluripotent cell\\u000a that can give rise to all lymphoid, myeloid and erythroid

  6. Stem Cell Niche, the Microenvironment and Immunological Crosstalk

    Microsoft Academic Search

    Law Sujata; S. Chaudhuri

    2008-01-01

    The concept of stem cells, their physiological existence, the intricate anatomical localization, the known and the unknown functions, and their exclusive utility for the purpose of regenerative medicine, are all now encompassed within an emergent question, ‘how compatible these cells are immunologically?’ Indeed, the medical aspects of stem cells are dependent on a large number of queries based on the

  7. A Quantitative and Dynamic Model for Plant Stem Cell Regulation

    Microsoft Academic Search

    Florian Geier; Jan U. Lohmann; Moritz Gerstung; Annette T. Maier; Jens Timmer; Christian Fleck; Raya Khanin

    2008-01-01

    Plants maintain pools of totipotent stem cells throughout their entire life. These stem cells are embedded within specialized tissues called meristems, which form the growing points of the organism. The shoot apical meristem of the reference plant Arabidopsis thaliana is subdivided into several distinct domains, which execute diverse biological functions, such as tissue organization, cell-proliferation and differentiation. The number of

  8. How Industry Can Help Improve STEM Graduation Rates

    Microsoft Academic Search

    R. Recio; L. Gable

    2007-01-01

    Based on Census and NSF data, the percent of US, college graduation age residents that earned Science, Technology, Engineering and Math (STEM) Bachelor's degrees in 2000 was 10.42%. Between 2000 and 2004, the number of STEM Bachelor graduates grew at a relatively low .86% compound growth rate (CGR) per year. In that same time period, the overall US resident population

  9. Intracoronary Autologous CD34+ Stem Cell Therapy for Intractable Angina

    Microsoft Academic Search

    Shihong Wang; Junyu Cui; Wei Peng; Min Lu

    2010-01-01

    Background\\/Objectives: A large number of patients with coronary artery disease experience angina that is not suitable for revascularization and is refractory to conventional medical therapy. Laboratory and preclinical studies have provided evidence for the safety and potential efficacy of autologous CD34+ stem cell therapies as treatment for angina. Clinical studies investigating intramyocardial transplantation of autologous CD34+ stem cells by catheter

  10. Valve stem oil deflector

    SciTech Connect

    Stritzke, B.G.

    1988-08-16

    This patent describes an oil deflector for attachment to a valve stem of an internal combustion engine or the like comprising a molded plastic cup having a generally cylindrical wall section and an enlarged transversely extending end wall defining a neck portion, having an opening for receiving a valve stem, a radially inwardly opening annular groove on an inner face of the opening in the neck portion, an O-ring in the groove, circumferentially spaced teeth on opposite sides of the groove each of which is engageable with a valve stem extending through the neck portion of the deflector to preclude tipping of the deflector relative to the valve stem.

  11. Hypertensive brain stem encephalopathy.

    PubMed

    Liao, Pen-Yuan; Lee, Chien-Chang; Chen, Cheng-Yu

    2015-01-01

    A 48-year-old man presented with headache and extreme hypertension. Computed tomography showed diffuse brain stem hypodensity. Magnetic resonance imaging revealed diffuse brain stem vasogenic edema. Hypertensive brain stem encephalopathy is an uncommon manifestation of hypertensive encephalopathy, which classically occurs at parietooccipital white matter. Because of its atypical location, the diagnosis can be challenging. Moreover, the coexistence of hypertension and brain stem edema could also direct clinicians toward a diagnosis of ischemic infarction, leading to a completely contradictory treatment goal. PMID:25082596

  12. Effects of stomatal density and leaf water content on the ¹?O enrichment of leaf water.

    PubMed

    Larcher, Leticia; Hara-Nishimura, Ikuko; Sternberg, Leonel

    2015-04-01

    Leaf water isotopic composition is imprinted in several biomarkers of interest and it is imperative that we understand the isotopic enrichment of leaf water. Here, we test the effect of stomatal density and leaf water content on the oxygen isotopic composition of leaf water in transgenic Arabidopsis plants expressing different stomatal densities, and several other species showing a range of stomatal density. We grew Arabidopsis plants hydroponically and collected other species in the field. Stomatal density and leaf water content were determined for each plant. We measured transpiration and extracted leaf water for isotopic determination. Using these measurements and the current leaf water isotope model, we calculated several of the parameters related to leaf water isotopic enrichment. High stomatal density promoted leaf water isotope enrichment. No conclusion, however, can be drawn regarding the effect of leaf water content on leaf water isotope enrichment. Factors such as transpiration might mask the effect of stomatal density on leaf water isotopic enrichment. We propose a method by which stomatal density can be incorporated in the current Peclet model of leaf water isotope enrichment. These findings have important applications in the use of plant-based metabolic proxies in paleoclimate studies. PMID:25408145

  13. Stem cell policies in the United States and in Germany.

    PubMed

    Gottweis, Herbert

    2002-01-01

    The article compares policymaking in the field of human embryonic stem cell research in the United States and Germany. Although experimental research with human stem cells is controversial in both countries, restrictions on research are much more strict in Germany than in the United States. In order to explain the contrast between the United States and Germany in dealing with human embryonic stem cell research and to predict possible future developments, we need to look carefully at a number of important differences in the interpretations and discourses of embryonic stem cell research and their consequences for the strategies of institutions and actors in the political-regulatory realm. PMID:17256227

  14. Evaluation of Aqueous Leaf Extract of Cardiospermum halicacabum (L.) on Fertility of Male Rats.

    PubMed

    Peiris, L Dinithi C; Dhanushka, M A T; Jayathilake, T A H D G

    2015-01-01

    Treatment with 100?mg/kg and 200?mg/kg body weight of aqueous leaf extract (ALE) of Cardiospermum halicacabum for 30 days produced a significant dose dependent increase in the sperm counts and sperm motility in both caput and cauda regions. Further, significant increase in serum testosterone level was evident at all applied doses. However, no significant changes in the weight of sex organs were observed. Aqueous leaf extract also increased the number of females impregnated, number of implantations, and number of viable fetuses while decreasing the total number of resorption sites in the pregnant females. However, the total cholesterol level in the serum remained unchanged and there were no records on renotoxicity; nevertheless ALE exhibited a hepatoprotective effect. It was concluded that aqueous leaf extract of Cardiospermum halicacabum enhanced sperm concentration, motility, and testosterone, leading to positive results in fertility. PMID:26064883

  15. Evaluation of Aqueous Leaf Extract of Cardiospermum halicacabum (L.) on Fertility of Male Rats

    PubMed Central

    Peiris, L. Dinithi. C.; Dhanushka, M. A. T.; Jayathilake, T. A. H. D. G.

    2015-01-01

    Treatment with 100?mg/kg and 200?mg/kg body weight of aqueous leaf extract (ALE) of Cardiospermum halicacabum for 30 days produced a significant dose dependent increase in the sperm counts and sperm motility in both caput and cauda regions. Further, significant increase in serum testosterone level was evident at all applied doses. However, no significant changes in the weight of sex organs were observed. Aqueous leaf extract also increased the number of females impregnated, number of implantations, and number of viable fetuses while decreasing the total number of resorption sites in the pregnant females. However, the total cholesterol level in the serum remained unchanged and there were no records on renotoxicity; nevertheless ALE exhibited a hepatoprotective effect. It was concluded that aqueous leaf extract of Cardiospermum halicacabum enhanced sperm concentration, motility, and testosterone, leading to positive results in fertility. PMID:26064883

  16. POLICY NUMBER 2006-16 August 11. 2006

    E-print Network

    Oliver, Douglas L.

    POLICY NUMBER 2006-16 August 11. 2006 POLICY: HUMAN EMBRYONIC STEM CELL RESEARCH AT UCHC PURPOSE: To ensure that all human embryonic stem cell (hESC) research conducted at the Institution is approved research involving in-eligible human embryonic stem cell lines. In 2005, the state of Connecticut

  17. Leaf endophyte load influences fungal garden development in leaf-cutting ants

    E-print Network

    Bermingham, Eldredge

    their symbiont fungus. The ants' fungal symbiont then partially degrades the leaf material, converting leaf; in the latter endophyte composition changed * Correspondence: svanbael@tulane.edu 1 Department of Ecology

  18. Measurement of leaf area index using image-processing technology

    NASA Astrophysics Data System (ADS)

    Qiu, Zhengjun; Fang, Hui; Zhang, Yun; He, Yong

    2005-10-01

    Leaf Area Index (LAI), as a fundamental parameter to evaluate the physiological condition of plants, was calculated by image processing based on machine vision technology. The measurement system hardware consisted primarily of the MS3100 3CCD camera, the image grabber card, a desktop computer and the acquired images were processed by Matlab and ENVI. After acquiring the 3 images by the 3CCD camera of Green, Red and NIR channels, the NIR image was considered more effective in separating the soil background for its higher contrast value. Thus, it was selected for image processing to calculate the leaf area index (LAI). The transect method was applied to obtain the threshold 50 in the binary image conversion and the soil background was thus eliminated as a result that most of its reflectance in the image was under 50. Then the 'imerode'-'imdilate' operation in the image processing box of Matlab was used to remove the left crop stem noises, including those small weeds in the binary image background. Consequently, the LAI of the acquired NIR image was calculated as 0.523 by dividing the total image pixel amount by that of the black pixels in the binary image.

  19. GELATION OF ALFALFA SOLUBLE LEAF PROTEINS

    Microsoft Academic Search

    B. P. Lamsal; R. G. Koegel; S. Gunasekaran

    Various alfalfa soluble leaf protein concentrates were prepared by freeze-drying acid-precipitated proteins (pH 3.5), resolubilized proteins (pH 7), and membrane-concentrated clarified alfalfa juice. Dilute leaf protein solutions were prepared by dissolving these concentrates in water. Storage modulus (G ) of soluble leaf protein solutions as they gel was monitored with a cone-and-plate probe during temperature sweep from 25°C to 90°C

  20. 7 CFR 28.467 - Leaf Grade 7.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf Grade 7. 28.467 Section 28.467 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.467 Leaf Grade 7. Leaf Grade 7 is leaf which...

  1. 7 CFR 28.466 - Leaf Grade 6.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf Grade 6. 28.466 Section 28.466 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.466 Leaf Grade 6. Leaf Grade 6 is leaf which is...

  2. 7 CFR 28.464 - Leaf Grade 4.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf Grade 4. 28.464 Section 28.464 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.464 Leaf Grade 4. Leaf Grade 4 is leaf which is...

  3. 7 CFR 28.462 - Leaf Grade 2.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf Grade 2. 28.462 Section 28.462 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.462 Leaf Grade 2. Leaf Grade 2 is leaf which is...

  4. 7 CFR 28.463 - Leaf Grade 3.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf Grade 3. 28.463 Section 28.463 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.463 Leaf Grade 3. Leaf Grade 3 is leaf which is...

  5. 7 CFR 28.462 - Leaf Grade 2.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf Grade 2. 28.462 Section 28.462 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.462 Leaf Grade 2. Leaf Grade 2 is leaf which is...

  6. 7 CFR 28.463 - Leaf Grade 3.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf Grade 3. 28.463 Section 28.463 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.463 Leaf Grade 3. Leaf Grade 3 is leaf which is...

  7. 7 CFR 28.466 - Leaf Grade 6.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf Grade 6. 28.466 Section 28.466 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.466 Leaf Grade 6. Leaf Grade 6 is leaf which is...

  8. 7 CFR 28.465 - Leaf Grade 5.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf Grade 5. 28.465 Section 28.465 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.465 Leaf Grade 5. Leaf Grade 5 is leaf which is...

  9. 7 CFR 28.466 - Leaf Grade 6.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf Grade 6. 28.466 Section 28.466 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.466 Leaf Grade 6. Leaf Grade 6 is leaf which is...

  10. 7 CFR 28.464 - Leaf Grade 4.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf Grade 4. 28.464 Section 28.464 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.464 Leaf Grade 4. Leaf Grade 4 is leaf which is...

  11. 7 CFR 28.461 - Leaf Grade 1.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf Grade 1. 28.461 Section 28.461 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.461 Leaf Grade 1. Leaf Grade 1 is leaf which is...

  12. 7 CFR 28.461 - Leaf Grade 1.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf Grade 1. 28.461 Section 28.461 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.461 Leaf Grade 1. Leaf Grade 1 is leaf which is...

  13. 7 CFR 28.461 - Leaf Grade 1.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf Grade 1. 28.461 Section 28.461 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.461 Leaf Grade 1. Leaf Grade 1 is leaf which is...

  14. 7 CFR 28.464 - Leaf Grade 4.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf Grade 4. 28.464 Section 28.464 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.464 Leaf Grade 4. Leaf Grade 4 is leaf which is...

  15. 7 CFR 28.465 - Leaf Grade 5.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf Grade 5. 28.465 Section 28.465 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.465 Leaf Grade 5. Leaf Grade 5 is leaf which is...

  16. 7 CFR 28.462 - Leaf Grade 2.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 2013-01-01 2013-01-01 false Leaf Grade 2. 28.462 Section 28.462 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.462 Leaf Grade 2. Leaf Grade 2 is leaf which is...

  17. 7 CFR 28.467 - Leaf Grade 7.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf Grade 7. 28.467 Section 28.467 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.467 Leaf Grade 7. Leaf Grade 7 is leaf which...

  18. 7 CFR 28.465 - Leaf Grade 5.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf Grade 5. 28.465 Section 28.465 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.465 Leaf Grade 5. Leaf Grade 5 is leaf which is...

  19. 7 CFR 28.463 - Leaf Grade 3.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 2012-01-01 2012-01-01 false Leaf Grade 3. 28.463 Section 28.463 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.463 Leaf Grade 3. Leaf Grade 3 is leaf which is...

  20. 7 CFR 28.467 - Leaf Grade 7.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 2014-01-01 2014-01-01 false Leaf Grade 7. 28.467 Section 28.467 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.467 Leaf Grade 7. Leaf Grade 7 is leaf which...

  1. The Clinical Status of Stem Cell Therapy for Ischemic Cardiomyopathy

    PubMed Central

    Wang, Xianyun; Zhang, Jun; Zhang, Fan; Li, Jing; Li, Yaqi; Tan, Zirui; Hu, Jie; Qi, Yixin; Yan, Baoyong

    2015-01-01

    Ischemic cardiomyopathy (ICM) is becoming a leading cause of morbidity and mortality in the whole world. Stem cell-based therapy is emerging as a promising option for treatment of ICM. Several stem cell types including cardiac-derived stem cells (CSCs), bone marrow-derived stem cells, mesenchymal stem cells (MSCs), skeletal myoblasts (SMs), and CD34+ and CD 133+ stem cells have been applied in clinical researches. The clinical effect produced by stem cell administration in ICM mainly depends on the transdifferentiation and paracrine effect. One important issue is that low survival and residential rate of transferred stem cells in the infracted myocardium blocks the effective advances in cardiac improvement. Many other factors associated with the efficacy of cell replacement therapy for ICM mainly including the route of delivery, the type and number of stem cell infusion, the timing of injection, patient's physical condition, the particular microenvironment onto which the cells are delivered, and clinical condition remain to be addressed. Here we provide an overview of the pros and cons of these transferred cells and discuss the current state of their therapeutic potential. We believe that stem cell translation will be an ideal option for patients following ischemic heart disease in the future.

  2. A Gata6Wnt pathway required for epithelial stem cell development and airway regeneration

    Microsoft Academic Search

    Yuzhen Zhang; Ashley M Goss; Ethan David Cohen; Rachel Kadzik; John J Lepore; Karthika Muthukumaraswamy; Jifu Yang; Francesco J DeMayo; Jeffrey A Whitsett; Michael S Parmacek; Edward E Morrisey

    2008-01-01

    Epithelial organs, including the lung, are known to possess regenerative abilities through activation of endogenous stem cell populations, but the molecular pathways regulating stem cell expansion and regeneration are not well understood. Here we show that Gata6 regulates the temporal appearance and number of bronchioalveolar stem cells (BASCs) in the lung, its absence in Gata6-null lung epithelium leading to the

  3. Cellular and Molecular Regulation of Hematopoietic and Intestinal Stem Cell Behavior

    Microsoft Academic Search

    Xi C. He; Jiwang Zhang; Linheng Li

    2005-01-01

    Two fundamental questions in stem cell research are what controls stem cell number in vivo and which signal pathways regulate self-renewal. Here we summarize our recent studies regarding the role of BMP signaling in regulation of stem cell behavior in both the hematopoietic and intestinal systems. These studies provide evidence to show that BMP signaling plays an important role in

  4. Asymmetric and symmetric stem-cell divisions in development and cancer

    Microsoft Academic Search

    Sean J. Morrison; Judith Kimble

    2006-01-01

    Much has been made of the idea that asymmetric cell division is a defining characteristic of stem cells that enables them to simultaneously perpetuate themselves (self-renew) and generate differentiated progeny. Yet many stem cells can divide symmetrically, particularly when they are expanding in number during development or after injury. Thus, asymmetric division is not necessary for stem-cell identity but rather

  5. Using Community Colleges to Build a STEM-Skilled Workforce. Issue Brief

    ERIC Educational Resources Information Center

    NGA Center for Best Practices, 2011

    2011-01-01

    Education and skills in science, technology, engineering, and mathematics (STEM) are important in a global economy increasingly focused on high-growth, technology-driven occupations. Yet, many states face a shortage of STEM-skilled students and workers. A number of states have built powerful and productive STEM education and skills strategies to…

  6. If a Stem Cell Dies in the Crypt, and No One Is Around to See It.

    E-print Network

    Klein, Ophir

    If a Stem Cell Dies in the Crypt, and No One Is Around to See It. Ysbrand M. Nusse1,2 and Ophir D://dx.doi.org/10.1016/j.stem.2013.03.009 Tworecentstudiescontinue repair after damage. A small number of self-re- newing stem cells are the source of new cells in many

  7. What Afterschool STEM Does Best: How Stakeholders Describe Youth Learning Outcomes

    ERIC Educational Resources Information Center

    Krishnamurthi, Anita; Bevan, Bronwyn; Rinehart, Jen; Coulon, Vicky Ragan

    2013-01-01

    As more stakeholders get involved in the effort to engage youth in STEM outside of school, afterschool providers are being asked to document a wide range of outcomes, from generating interest in STEM to improving standardized test scores in math and science and to increasing the number of students who pursue STEM majors in college. This issue has…

  8. Generation of Human Embryonic Stem Cell-Derived Mesoderm and Cardiac Cells

    E-print Network

    Zandstra, Peter W.

    ARTICLE Generation of Human Embryonic Stem Cell-Derived Mesoderm and Cardiac Cells Using Size pluripotent stem cell-derived cell types at sufficiently high numbers and in a reproducible manner for the differentiation of pluripotent cells such as human embryonic stem cells (hESC) rely on the generation

  9. Membrane Glycolipids in Stem Cells

    PubMed Central

    Yu, Robert K.; Suzuki, Yusuke; Yanagisawa, Makoto

    2015-01-01

    Stem cells, such as embryonic stem cells, hematopoietic stem cells, neural stem cells, mesenchymal stem cells, and very small embryonic-like stem cells, are undifferentiated cells that are endowed with a high potential for proliferation and the capacity for self-renewal with retention of pluri/multipotency to differentiate into their progenies. Recently, studies regarding the biological functions of glycolipids and cell surface microdomains (caveolae, lipid rafts, or glycolipid-enriched microdomains) in stem cells are emerging. In this review, we introduce the expression patterns of glycolipids and the functional roles of cell surface microdomains in stem cells. PMID:19716368

  10. Designing for STEM Integration

    ERIC Educational Resources Information Center

    Berland, Leema K.

    2013-01-01

    We are increasingly seeing an emphasis on STEM integration in high school classrooms such that students will learn and apply relevant math and science content while simultaneously developing engineering habits of mind. However, research in both science education and engineering education suggests that this goal of truly integrating STEM is rife…

  11. Lock For Valve Stem

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.; Guirguis, Kamal S.

    1991-01-01

    Simple, cheap device locks valve stem so its setting cannot be changed by unauthorized people. Device covers valve stem; cover locked in place with standard padlock. Valve lock made of PVC pipe and packing band. Shears, drill or punch, and forming rod only tools needed.

  12. Adult stem cell plasticity

    Microsoft Academic Search

    Richard Poulsom; Malcolm R. Alison; Stuart J. Forbes; Nicholas A. Wright

    2002-01-01

    Observations made in the last few years support the existence of pathways, in adult humans and rodents, that allow adult stem cells to be surprisingly flexible in their differentiation repertoires. Termed plasticity, this property allows adult stem cells, assumed, until now, to be committed to generating a fixed range of progeny, to switch, when they have been relocated, to make

  13. Bioreactors Stem Cells

    E-print Network

    Schüler, Axel

    Keywords Bioreactors Stem Cells Regenerative Medicine Tissue Engineering Pharmacology » Prof. M.; yeZhelyev, M.; eMMrich, F.; o'regan, r.; bader, a. Quantum dots for human mesenchymal stem cells and mechanical forces mediated to the cells by the matrix. The in vivo extracellular matrix constitutes

  14. How Undergraduate Women Choose STEM Careers

    NASA Astrophysics Data System (ADS)

    Hughes, Roxanne

    2013-03-01

    In 2010 women represented half of the US population and over half of current graduates from college (57%) but less than a third of undergraduate degrees in science and engineering (STEM). This underrepresentation is worse in certain fields such as physics (21%), and engineering (22%) compared to 52% in chemistry. This underrepresentation is not only a social and cultural issue, but it is also cause for alarm in regard to the United States' ability to maintain its technological and economic dominance in the global economy. STEM fields provide valuable contributions to the nation's economic and environmental security (Augustine, 2005; Chang, 2009; Riegle-Crumb and King, 2010; Robelen, 2010; Tessler, 2008), paying practitioners well and bringing in revenue for successful businesses and governments (National Science Board [NSB], 2008; Riegle-Crumb and King). Consequently, addressing the underrepresentation of women and increasing their persistence in STEM fields will increase the number of scientists and engineers contributing to these fields, which could, in turn, improve the nation's economy, safety, and technological revenues. Research indicates that there are internal and external factors that affect the ability of women to see future success in STEM and to identify with the STEM and consequently persist. This presentation will summarize the current literature on issues affecting undergraduate women's retention in STEM as well as present strategies to improve this retention. Part of this presentation will draw from my own research studies in this area. The findings from my study and others reveal that only women who participate in redefinition strategies related to their marginalized status are able to persist; those who cannot redefine their marginality in relation to the dominant discourse of STEM begin to lose interest or doubt their competence in the field, resulting in their departure from STEM.

  15. I-STEM

    NSDL National Science Digital Library

    The University of Illinois at Urbana-Champaign has developed a multi-pronged approach to remedying the lack of academic emphasis on the STEM subjects, from preschool through college, as well as the lack of interest in STEM subjects on the part of youth in the United States. Visitors can read about the University's four goals under the "Goals" tab at the top of any page. The "STEM Ed Projects" tab contains a directory of externally funded projects divided into four categories, and which are then further divided into subcategories. Visitors will find such projects as "Improving Supply and Demand Data for the Preparation of Secondary Science and Math Teachers" and "Clean Energy Education Workshop", under the category that aims to shape policy and advocate for STEM education. The "Resources" tab contains half a dozen categories under which visitors will find Outreach Resources, Teacher Development and Resources, and Policy and Advocacy for STEM Ed.

  16. Identification of putative fallopian tube stem cells.

    PubMed

    Snegovskikh, Victoria; Mutlu, Levent; Massasa, Effi; Taylor, Hugh S

    2014-12-01

    Stem cells are used to repair and regenerate multiple tissues in the adult. We have previously shown that stem cells play a significant role in mediating endometrial repair and tissue regeneration. We hypothesized that the oviduct may possess a similar population of stem cells that contribute to the maintenance of this tissue. Here we identify label-retaining cells (LRCs) in the murine oviduct which indicate the presence of a stem/progenitor cell population in this tissue as well. Two-day-old CD-1 mice were injected intraperitoneally with 5-bromo-2-deoxyuridine (BrdU) or vehicle control. Female animals (n = 36 for each group) were killed at 6 weeks post injection. Reproductive tracts were removed, specimens were embedded in paraffin, and 5-µ sections were prepared. Oviduct was identified by hematoxylin and eosin staining and morphology. Immunofluorescence studies were performed on serial sections tissues (n = 12 per animal) using antibodies against BrdU. Confocal microscopy was used to identify 4',6-diamidino-2-phenylindole (DAPI)- and BrdU-stained nuclei. In the group of mice exposed to BrdU, we identified a population of LRCs in all specimens and not in controls. The putative stem cells are located at the base of each villi, suggesting the location of the stem cell niche. The number of DAPI-stained nuclei divided by the number of LRCs; LRCs constituted 0.5% of all nucleated cells. The oviduct contains a population of progenitor cells, likely used in the repair and regeneration of fallopian tube. Defective or insufficient stem cell reserve may underlie common tubal diseases, including hydrosalpinx and ectopic pregnancy. PMID:25305130

  17. Clinical grade adult stem cell banking

    PubMed Central

    Thirumala, Sreedhar; Goebel, W Scott

    2009-01-01

    There has been a great deal of scientific interest recently generated by the potential therapeutic applications of adult stem cells in human care but there are several challenges regarding quality and safety in clinical applications and a number of these challenges relate to the processing and banking of these cells ex-vivo. As the number of clinical trials and the variety of adult cells used in regenerative therapy increases, safety remains a primary concern. This has inspired many nations to formulate guidelines and standards for the quality of stem cell collection, processing, testing, banking, packaging and distribution. Clinically applicable cryopreservation and banking of adult stem cells offers unique opportunities to advance the potential uses and widespread implementation of these cells in clinical applications. Most current cryopreservation protocols include animal serum proteins and potentially toxic cryoprotectant additives (CPAs) that prevent direct use of these cells in human therapeutic applications. Long term cryopreservation of adult stem cells under good manufacturing conditions using animal product free solutions is critical to the widespread clinical implementation of ex-vivo adult stem cell therapies. Furthermore, to avoid any potential cryoprotectant related complications, reduced CPA concentrations and efficient post-thaw washing to remove CPA are also desirable. The present review focuses on the current strategies and important aspects of adult stem cell banking for clinical applications. These include current good manufacturing practices (cGMPs), animal protein free freezing solutions, cryoprotectants, freezing & thawing protocols, viability assays, packaging and distribution. The importance and benefits of banking clinical grade adult stem cells are also discussed. PMID:20046678

  18. The Paradoxical Dynamism of Marrow Stem Cells: Considerations of Stem Cells, Niches, and Microvesicles

    PubMed Central

    Aliotta, Jason M.

    2015-01-01

    Marrow stem cell regulation represents a complex and flexible system. It has been assumed that the system was intrinsically hierarchical in nature, but recent data has indicated that at the progenitor/stem cell level the system may represent a continuum with reversible alterations in phenotype occurring as the stem cells transit cell cycle. Short and long-term engraftment, in vivo and in vitro differentiation, gene expression, and progenitor numbers have all been found to vary reversibly with cell cycle. In essence, the stem cells appear to show variable potential, probably based on transcription factor access, as they proceed through cell cycle. Another critical component of the stem cell regulation is the microenvironment, so-called niches. We propose that there are not just several unique niche cells, but a wide variety of niche cells which continually change phenotype to appropriately interact with the continuum of stem cell phenotypes. A third component of the regulatory system is microvesicle transfer of genetic information between cells. We have shown that marrow cells can express the genetic phenotype of pulmonary epithelial cells after microvesicle transfer from lung to marrow cells. Similar transfers of tissue specific mRNA occur between liver, brain, and heart to marrow cells. Thus, there would appear to be a continuous genetic modulation of cells through microvesicle transfer between cells. We propose that there is an interactive triangulated Venn diagram with continuously changing stem cells interacting with continuously changing areas of influence, both being modulated by transfer of genetic information by microvesicles. PMID:18665337

  19. Complex Interactions Among Detritivorous Insects Inhabiting Leaf Packs in a North Carolina Stream

    NASA Astrophysics Data System (ADS)

    Pflaum, J. R.

    2005-05-01

    Large detritivorous insects may influence the distribution and abundance of other invertebrates that inhabit leaf packs. In a previous study we observed a complementary distribution between the caddisfly Pycnopsyche and ephemerellid and leptophlebiid mayflies in a headwater stream. Initially, we hypothesized that encounter competition between these organisms was the mechanism responsible for this distribution. When presented with a choice of leaf packs in an enclosure, one of which contained Pycnopsyche, neither ephemerellids nor leptophebiids exhibited significant avoidance of leaf packs inhabited by Pycnopsyche. However, a significant number of mayflies from both families were not recovered suggesting that intraguild predation was occurring. A preliminary stable isotope analysis does not support the intraguild predation hypothesis. In a field experiment we examined invertebrate colonization of leaf packs on which we placed 0, 3, and 6 Pycnopsyche. We hypothesized that leaf packs with no Pycnopsyche would have higher numbers of colonizing invertebrates (particularly mayflies) than leaf packs with Pycnopsyche. Results of this study showed that some taxa increased in the presence of Pycnopsyche while other taxa declined. Our results suggest that Pycnopsyche may influence the distribution and abundance of other invertebrate taxa through various mechanisms.

  20. Influence of leaf water status on leaf area index and leaf nitrogen concentration inversion of wheat canopy

    NASA Astrophysics Data System (ADS)

    Zhao, Chunjiang; Wang, Jihua; Huang, Wenjiang; Liu, Liangyun

    2005-01-01

    A field trial was conduct to investigate the relationship between spectral feature of winter wheat canopy and LAI as well as leaf nitrogen (N) under different status of leaf water in field situation. The objective of this study is to investigate effect of water status in plants on the accuracy of estimating leaf area index (LAI) and plant nitrogen. The new defined spectral index, IAFC = (R2224-R2054)/ (R2224+R2054), where R is the reflectance at 2224nm or 2054nm, was significantly (?=0.05) or extremely significantly (?=0.01) correlated with LAI at all the six dates for water insufficient plants, but not significantly correlated for water sufficient plants at five of the six dates and the difference of leaf water content between the water insufficient plants and water sufficient plants was only about 2% at some dates. The study provided strong evidence that leaf water has a strong masking effect on the 2000-2300nm spectral feature, which could be strongly associated with LAI and leaf N even when the leaf water content was as high as about 80% if the water was insufficient for plant growth. The results indicated that the masking effect of leaf water on the 2000-2300nm spectral feature was not only dependent on the absolute plant water content but also on the water status and that remotely sensed data in the 2000-2300nm region could be of potential in monitoring plant canopy biophysics and biochemistry in drought condition.

  1. Segmentation and leaf sequencing for intensity modulated arc therapy

    SciTech Connect

    Gladwish, Adam; Oliver, Mike; Craig, Jeff; Chen, Jeff; Bauman, Glenn; Fisher, Barbara; Wong, Eugene [Department of Physics, London Regional Cancer Program, London (Canada) and Medical Biophysics, University of Western Ontario, London (Canada); Department of Physics, London Regional Cancer Program, London (Canada); Department of Physics, London Regional Cancer Program, London (Canada) and Departments of Oncology and Medical Biophysics, University of Western Ontario, London (Canada); Department of Oncology, University of Western Ontario, London (Canada); Department of Physics, London Regional Cancer Program, London (Canada) and Departments of Oncology and Medical Biophysics, University of Western Ontario, London (Canada)

    2007-05-15

    A common method in generating intensity modulated radiation therapy (IMRT) plans consists of a three step process: an optimized fluence intensity map (IM) for each beam is generated via inverse planning, this IM is then segmented into discrete levels, and finally, the segmented map is translated into a set of MLC apertures via a leaf sequencing algorithm. To date, limited work has been done on this approach as it pertains to intensity modulated arc therapy (IMAT), specifically in regards to the latter two steps. There are two determining factors that separate IMAT segmentation and leaf sequencing from their IMRT equivalents: (1) the intrinsic 3D nature of the intensity maps (standard 2D maps plus the angular component), and (2) that the dynamic multileaf collimator (MLC) constraints be met using a minimum number of arcs. In this work, we illustrate a technique to create an IMAT plan that replicates Tomotherapy deliveries by applying IMAT specific segmentation and leaf-sequencing algorithms to Tomotherapy output sinograms. We propose and compare two alternative segmentation techniques, a clustering method, and a bottom-up segmentation method (BUS). We also introduce a novel IMAT leaf-sequencing algorithm that explicitly takes leaf movement constraints into consideration. These algorithms were tested with 51 angular projections of the output leaf-open sinograms generated on the Hi-ART II treatment planning system (Tomotherapy Inc.). We present two geometric phantoms and 2 clinical scenarios as sample test cases. In each case 12 IMAT plans were created, ranging from 2 to 7 intensity levels. Half were generated using the BUS segmentation and half with the clustering method. We report on the number of arcs produced as well as differences between Tomotherapy output sinograms and segmented IMAT intensity maps. For each case one plan for each segmentation method is chosen for full Monte Carlo dose calculation (NumeriX LLC) and dose volume histograms (DVH) are calculated. In all cases, the BUS method outperformed the clustering, method. We recommend using the BUS algorithm and discuss potential improvements to the clustering algorithms.

  2. Vascular potential of human pluripotent stem cells

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cardiovascular disease is the number one cause of death and disability in the US. Understanding the biological activity of stem and progenitor cells, and their ability to contribute to the repair, regeneration and remodeling of the heart and blood vessels affected by pathological processes is an ess...

  3. Extrinsic regulation of pluripotent stem cells

    Microsoft Academic Search

    Martin F. Pera; Patrick P. L. Tam

    2010-01-01

    During early mammalian development, as the pluripotent cells that give rise to all of the tissues of the body proliferate and expand in number, they pass through transition states marked by a stepwise restriction in developmental potential and by changes in the expression of key regulatory genes. Recent findings show that cultured stem-cell lines derived from different stages of mouse

  4. Stem Cells in the Postnatal Pituitary?

    Microsoft Academic Search

    Hugo Vankelecom

    2007-01-01

    Tissue-specific stem cells are uncovered in a growing number of organs by their molecular expression profile and their potential for self-renewal, multipotent differentiation and tissue regeneration. Whether the pituitary gland also contains a pool of versatile ’master’ cells that drive homeostatic, plastic and regenerative cell ontogenesis is at present unknown. Here, I will give an overview of data that may

  5. Recruiting and Hiring Women in STEM Fields

    Microsoft Academic Search

    Christy Glass; Krista Lynn Minnotte

    2010-01-01

    The number of women earning advanced degrees in science, technology, engineering, and mathematics (STEM) has increased, yet women remain underrepresented at all ranks of the academic hierarchy in these fields. To help explain this pattern, we explored mechanisms in the recruitment and hiring process at the level of the department that hinder or promote the hiring of women into tenure-track

  6. Direct leaf trajectory optimization for volumetric modulated arc therapy planning with sliding window delivery

    E-print Network

    Papp, Dávid

    2013-01-01

    We propose a novel optimization model for volumetric modulated arc therapy (VMAT) planning that directly optimizes deliverable leaf trajectories in the treatment plan optimization problem, and eliminates the need for a separate arc-sequencing step. In this model, a 360-degree arc is divided into a given number of arc segments in which the leaves move unidirectionally. This facilitates an algorithm that determines the optimal piecewise linear leaf trajectories for each arc segment, which are deliverable in a given treatment time. Multi-leaf collimator (MLC) constraints, including maximum leaf speed and interdigitation, are accounted for explicitly. The algorithm is customized to allow for VMAT delivery using constant gantry speed and dose rate, however, the algorithm generalizes to variable gantry speed if beneficial. We demonstrate the method for three different tumor sites: a head-and-neck case, a prostate case, and a paraspinal case. For that purpose, we first obtain a reference plan for intensity modulated...

  7. Factors influencing the production of stem cuttings by glasshouse-grown potato plants

    Microsoft Academic Search

    H. A. Hepburn; S. Matthews

    1985-01-01

    The effects of nitrogen nutrition, main stem number and degree of defoliation of potato mother plants on stem-cutting production were investigated in glasshouse experiments with the cultivars Désirée, Record and Sutton's Foremost. Defoliation of the mother plants increased the number of cuttings produced, the total axillary growth, and the rate of cutting production. An increase in the number of main

  8. Hydro-ecological Effects on the Isotopic Composition of Soil and Leaf Water in Humid Deciduous Forests of Southern United States.

    NASA Astrophysics Data System (ADS)

    Mora, G.; Jahren, A. H.

    2001-05-01

    Paleoclimatic information inferred from the oxygen and hydrogen isotope abundance of fossil plant tissues and biomarkers relies on the observed close relationship between values of ? D and ? 18O for rainwater and environmental parameters (i.e., temperature, humidity, etc). However, the isotope content of rainwater can be altered during its passage through the canopy and the soil zone. Moreover, large isotope fractionations can occur after water enters the vascular system of plants as a result of leaf evaporation and biological processes. A number of studies, for instance, have addressed the effect of soil evaporation in arid and semi-arid regions that produces an enrichment of up to 20‰ in 18O and 80‰ in D in soil and stem water. Little is known, however, about fractionation effects in highly productive sub-tropical/temperate areas. With this study, we seek to evaluate evaporation effect on three humid deciduous forests of southern United States located along a 460-km transect that shows a precipitation gradient of about 200-mm in annual precipitation. The predominant tree species at the studied sites include dogwood, sugar gum, and silver maple. Rainwater was collected for isotopic determinations at the three localities, showing values that plot along the Meteoric Water Line. No significant difference (up to 0.4‰ for ? 18O and 4‰ for ? D) was observed in the isotopic composition of open rainfall and throughfall precipitation at the three sites. Soil water was cryogenically extracted from samples collected every 25-cm at the three sites during the growing season of 1997. Soil water from the upper soil horizons at the wettest site (Saint Bernard Park, Mississippi) showed isotopic values similar to those of rainfall. Moreover, isotopic values for soil water at this site were similar with depth, having a maximum difference of about 0.3‰ for ? 18O and of about 2‰ for ? D. Isotopic values for soil water at the driest locality (Natchez Lake, Arkansas) showed a decreasing trend with depth, exhibiting an isotopic enrichment of about 0.6‰ in 18O and of about 5‰ in D in the upper horizon. These preliminary results point to small isotopic differences between rainwater and soil water along the observed gradient, suggesting a small effect of soil evaporation along this precipitation gradient in the southern United States. Consequently, these results indicate that the isotopic composition of plant tissues in humid deciduous forests may contain valuable paleoclimatic information by reflecting the isotopic composition of rainwater. Ongoing isotopic determinations of leaf and stem water will allow for an evaluation of leaf evaporation.

  9. Genome-scale transcriptomic and epigenomic analysis of stem cells 

    E-print Network

    Halbritter, Florian

    2012-11-30

    Embryonic stem cells (ESCs) are a special type of cell marked by two key properties: The capacity to create an unlimited number of identical copies of themselves (self-renewal) and the ability to give rise to differentiated ...

  10. Stem cell sources for regenerative medicine: the immunological point of view

    Microsoft Academic Search

    Olivier Preynat-Seauve; Karl-Heinz Krause

    Stem cell transplantation consists in the introduction of stem cells or derived products in a diseased organism. Because of\\u000a the differentiation properties of stem cells, the goal is to replace damaged cells or tissues. Numbers of stem cell were identified\\u000a and isolated from embryos, fetuses, or adult organs, harboring different properties, and thus providing multiple strategies\\u000a of regenerative medicine for

  11. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade...

  12. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...2010-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade...

  13. Leaf element concentrations of terrestrial plants across China are

    E-print Network

    Slik, Ferry

    extracted from publications. The links between envi- ronmental variables, taxonomy and leaf elements wereRESEARCH PAPER Leaf element concentrations of terrestrial plants across China are influenced cycles of terrestrial eco- systems are strongly affected by leaf element concentrations. Understanding

  14. Elevated CO22 and Leaf Longevity in the C44 Grassland-Dominant Andropogon gerardii.

    PubMed

    Knapp; Bargmann; Maragni; McAllister; Bremer; Ham; Owensby

    1999-11-01

    In central U.S. grasslands, plant and ecosystem responses to elevated CO2 are most pronounced when water availability is limited. In a northeast Kansas grassland, responses to elevated CO2 in leaf area, number, development, and longevity were quantified for the tallgrass prairie dominant, Andropogon gerardii. Plants were grown in open-top chambers (OTCs) modified to limit water availability and to maximize responses to elevated CO2. In OTCs with elevated (x2 ambient) levels of CO2, aboveground biomass production and leaf water potentials were increased significantly compared with those of plants in OTCs with ambient CO2. There were no differences in leaf area or leaf number per tiller in A. gerardii in elevated compared with ambient OTCs. However, leaf area in adjacent unchambered plots with greater water availability was significantly higher than in the OTCs. The time required for developing leaves to achieve maximum leaf area was reduced by 29%, and the period of time until leaves senesced was increased by 20% for plants exposed to elevated compared with ambient CO2. Thus, leaves of this C4 grass species expanded more rapidly (6 d) and remained green longer (9 d) when exposed to elevated CO2. Such CO2-mediated increases in leaf longevity in the dominant species may allow this grassland to respond more opportunistically to temporally variable rainfall patterns in high-CO2 environments. These responses should be included in leaf-based simulation models that attempt to mechanistically link physiological alterations to predicted canopy responses to increased CO2. PMID:10568772

  15. ADULT MESENCHYMAL STEM CELLS DERIVED FROM EMBRYONIC STEM CELLS

    Microsoft Academic Search

    N. L. BOYD; P. BOSCH; S. L. STICE

    Mesenchymal stem cells (MSC) are useful in cell therapy and stem cell research but they have a limited lifespan in culture. Our goal was to develop a unique and limitless supply of mesenchymal stem cells derived from human embryonic stem cells, opening up new uses and enhance existing uses of these important cell types. For any application that uses large

  16. Cell Stem Cell Stem Cell Epigenetics: Looking Forward

    E-print Network

    Sander, Maike

    Cell Stem Cell Voices Stem Cell Epigenetics: Looking Forward Epigenetics in Adult SCs The integrity of tissues is maintained by adult stem cells during adulthood. How- ever, recent work indicates that tissues often contain more than one population of stem cells that are located at distinct niches and display

  17. Cell Stem Cell Control of Stem Cell Fate by Physical

    E-print Network

    Chen, Christopher S.

    Cell Stem Cell Review Control of Stem Cell Fate by Physical Interactions with the Extracellular, Philadelphia, PA 19104, USA 5Stem Cell Laboratory, Pennington Biomedical Research Center, Louisiana State.06.016 A diverse array of environmental factors contributes to the overall control of stem cell activity

  18. Wheat Leaf Rust Caused by Puccinia triticina

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leaf rust, caused by Puccinia triticina, is the most common rust disease of wheat. The fungus is an obligate parasite capable of producing infectious urediniospores as long as the host remains healthy. Urediniospores can be wind-disseminated hundreds of kilometers and may result in wheat leaf rust e...

  19. EFFECTS OF DEOXYNIVALENOL ON BARLEY LEAF PIGMENTATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a first step in characterizing the role deoxynivalenol (DON) plays in pathogenesis of Fusarium graminearum in leaf and head tissues, we treated detached barley leaf tissues with DON and examined them daily for signs of injury or other alterations. As shown here, DON had pronounced and unexpected ...

  20. 7 CFR 29.1030 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See Elements of Quality Chart.) [42 FR 21092, Apr. 25, 1977. Redesignated at 49 FR 16755, Apr. 20, 1984, and 51 FR 25027,...