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Sample records for delays drought-induced leaf

  1. Drought-Induced Leaf Proteome Changes in Switchgrass Seedlings

    PubMed Central

    Ye, Zhujia; Sangireddy, Sasikiran; Okekeogbu, Ikenna; Zhou, Suping; Yu, Chih-Li; Hui, Dafeng; Howe, Kevin J.; Fish, Tara; Thannhauser, Theodore W.

    2016-01-01

    Switchgrass (Panicum virgatum) is a perennial crop producing deep roots and thus highly tolerant to soil water deficit conditions. However, seedling establishment in the field is very susceptible to prolonged and periodic drought stress. In this study, a “sandwich” system simulating a gradual water deletion process was developed. Switchgrass seedlings were subjected to a 20-day gradual drought treatment process when soil water tension was increased to 0.05 MPa (moderate drought stress) and leaf physiological properties had expressed significant alteration. Drought-induced changes in leaf proteomes were identified using the isobaric tags for relative and absolute quantitation (iTRAQ) labeling method followed by nano-scale liquid chromatography mass spectrometry (nano-LC-MS/MS) analysis. Additionally, total leaf proteins were processed using a combinatorial library of peptide ligands to enrich for lower abundance proteins. Both total proteins and those enriched samples were analyzed to increase the coverage of the quantitative proteomics analysis. A total of 7006 leaf proteins were identified, and 257 (4% of the leaf proteome) expressed a significant difference (p < 0.05, fold change <0.6 or >1.7) from the non-treated control to drought-treated conditions. These proteins are involved in the regulation of transcription and translation, cell division, cell wall modification, phyto-hormone metabolism and signaling transduction pathways, and metabolic pathways of carbohydrates, amino acids, and fatty acids. A scheme of abscisic acid (ABA)-biosynthesis and ABA responsive signal transduction pathway was reconstructed using these drought-induced significant proteins, showing systemic regulation at protein level to deploy the respective mechanism. Results from this study, in addition to revealing molecular responses to drought stress, provide a large number of proteins (candidate genes) that can be employed to improve switchgrass seedling growth and establishment under

  2. Drought-Induced Leaf Proteome Changes in Switchgrass Seedlings.

    PubMed

    Ye, Zhujia; Sangireddy, Sasikiran; Okekeogbu, Ikenna; Zhou, Suping; Yu, Chih-Li; Hui, Dafeng; Howe, Kevin J; Fish, Tara; Thannhauser, Theodore W

    2016-01-01

    Switchgrass (Panicum virgatum) is a perennial crop producing deep roots and thus highly tolerant to soil water deficit conditions. However, seedling establishment in the field is very susceptible to prolonged and periodic drought stress. In this study, a "sandwich" system simulating a gradual water deletion process was developed. Switchgrass seedlings were subjected to a 20-day gradual drought treatment process when soil water tension was increased to 0.05 MPa (moderate drought stress) and leaf physiological properties had expressed significant alteration. Drought-induced changes in leaf proteomes were identified using the isobaric tags for relative and absolute quantitation (iTRAQ) labeling method followed by nano-scale liquid chromatography mass spectrometry (nano-LC-MS/MS) analysis. Additionally, total leaf proteins were processed using a combinatorial library of peptide ligands to enrich for lower abundance proteins. Both total proteins and those enriched samples were analyzed to increase the coverage of the quantitative proteomics analysis. A total of 7006 leaf proteins were identified, and 257 (4% of the leaf proteome) expressed a significant difference (p < 0.05, fold change <0.6 or >1.7) from the non-treated control to drought-treated conditions. These proteins are involved in the regulation of transcription and translation, cell division, cell wall modification, phyto-hormone metabolism and signaling transduction pathways, and metabolic pathways of carbohydrates, amino acids, and fatty acids. A scheme of abscisic acid (ABA)-biosynthesis and ABA responsive signal transduction pathway was reconstructed using these drought-induced significant proteins, showing systemic regulation at protein level to deploy the respective mechanism. Results from this study, in addition to revealing molecular responses to drought stress, provide a large number of proteins (candidate genes) that can be employed to improve switchgrass seedling growth and establishment under soil

  3. A Potential Role of Flag Leaf Potassium in Conferring Tolerance to Drought-Induced Leaf Senescence in Barley

    PubMed Central

    Hosseini, Seyed A.; Hajirezaei, Mohammad R.; Seiler, Christiane; Sreenivasulu, Nese; von Wirén, Nicolaus

    2016-01-01

    Terminal drought stress decreases crop yields by inducing abscisic acid (ABA) and premature leaf senescence. As potassium (K) is known to interfere with ABA homeostasis we addressed the question whether there is genetic variability regarding the role of K nutrition in ABA homeostasis and drought tolerance. To compare their response to drought stress, two barley lines contrasting in drought-induced leaf senescence were grown in a pot experiment under high and low K supply for the analysis of flag leaves from the same developmental stage. Relative to the drought-sensitive line LPR, the line HPR retained more K in its flag leaves under low K supply and showed delayed flag leaf senescence under terminal drought stress. High K retention was further associated with a higher leaf water status, a higher concentration of starch and other primary carbon metabolites. With regard to ABA homeostasis, HPR accumulated less ABA but higher levels of the ABA degradation products phaseic acid (PA) and dehydro-PA. Under K deficiency this went along with higher transcript levels of ABA8′-HYDROXYLASE, encoding a key enzyme in ABA degradation. The present study provides evidence for a positive impact of the K nutritional status on ABA homeostasis and carbohydrate metabolism under drought stress. We conclude that genotypes with a high K nutritional status in the flag leaf show superior drought tolerance by promoting ABA degradation but attenuating starch degradation which delays flag leaf senescence. Flag leaf K levels may thus represent a useful trait for the selection of drought-tolerant barley cultivars. PMID:26955376

  4. A Potential Role of Flag Leaf Potassium in Conferring Tolerance to Drought-Induced Leaf Senescence in Barley.

    PubMed

    Hosseini, Seyed A; Hajirezaei, Mohammad R; Seiler, Christiane; Sreenivasulu, Nese; von Wirén, Nicolaus

    2016-01-01

    Terminal drought stress decreases crop yields by inducing abscisic acid (ABA) and premature leaf senescence. As potassium (K) is known to interfere with ABA homeostasis we addressed the question whether there is genetic variability regarding the role of K nutrition in ABA homeostasis and drought tolerance. To compare their response to drought stress, two barley lines contrasting in drought-induced leaf senescence were grown in a pot experiment under high and low K supply for the analysis of flag leaves from the same developmental stage. Relative to the drought-sensitive line LPR, the line HPR retained more K in its flag leaves under low K supply and showed delayed flag leaf senescence under terminal drought stress. High K retention was further associated with a higher leaf water status, a higher concentration of starch and other primary carbon metabolites. With regard to ABA homeostasis, HPR accumulated less ABA but higher levels of the ABA degradation products phaseic acid (PA) and dehydro-PA. Under K deficiency this went along with higher transcript levels of ABA8'-HYDROXYLASE, encoding a key enzyme in ABA degradation. The present study provides evidence for a positive impact of the K nutritional status on ABA homeostasis and carbohydrate metabolism under drought stress. We conclude that genotypes with a high K nutritional status in the flag leaf show superior drought tolerance by promoting ABA degradation but attenuating starch degradation which delays flag leaf senescence. Flag leaf K levels may thus represent a useful trait for the selection of drought-tolerant barley cultivars. PMID:26955376

  5. A Drought-Inducible Transcription Factor Delays Reproductive Timing in Rice.

    PubMed

    Zhang, Chunyu; Liu, Jun; Zhao, Tao; Gomez, Adam; Li, Cong; Yu, Chunsheng; Li, Hongyu; Lin, Jianzhong; Yang, Yuanzhu; Liu, Bin; Lin, Chentao

    2016-05-01

    The molecular mechanisms underlying photoperiod or temperature control of flowering time have been recently elucidated, but how plants regulate flowering time in response to other external factors, such as water availability, remains poorly understood. Using a large-scale Hybrid Transcription Factor approach, we identified a bZIP transcriptional factor, O. sativa ABA responsive element binding factor 1 (OsABF1), which acts as a suppressor of floral transition in a photoperiod-independent manner. Simultaneous knockdown of both OsABF1 and its closest homologous gene, OsbZIP40, in rice (Oryza sativa) by RNA interference results in a significantly earlier flowering phenotype. Molecular and genetic analyses demonstrate that a drought regime enhances expression of the OsABF1 gene, which indirectly suppresses expression of the Early heading date 1 (Ehd1) gene that encodes a key activator of rice flowering. Furthermore, we identified a drought-inducible gene named OsWRKY104 that is under the direct regulation of OsABF1 Overexpression of OsWRKY104 can suppress Ehd1 expression and confers a later flowering phenotype in rice. Together, these findings reveal a novel pathway by which rice modulates heading date in response to the change of ambient water availability. PMID:26945049

  6. A Drought-Inducible Transcription Factor Delays Reproductive Timing in Rice1[OPEN

    PubMed Central

    Zhang, Chunyu; Zhao, Tao; Gomez, Adam; Li, Cong; Yu, Chunsheng; Lin, Jianzhong; Lin, Chentao

    2016-01-01

    The molecular mechanisms underlying photoperiod or temperature control of flowering time have been recently elucidated, but how plants regulate flowering time in response to other external factors, such as water availability, remains poorly understood. Using a large-scale Hybrid Transcription Factor approach, we identified a bZIP transcriptional factor, O. sativa ABA responsive element binding factor 1 (OsABF1), which acts as a suppressor of floral transition in a photoperiod-independent manner. Simultaneous knockdown of both OsABF1 and its closest homologous gene, OsbZIP40, in rice (Oryza sativa) by RNA interference results in a significantly earlier flowering phenotype. Molecular and genetic analyses demonstrate that a drought regime enhances expression of the OsABF1 gene, which indirectly suppresses expression of the Early heading date 1 (Ehd1) gene that encodes a key activator of rice flowering. Furthermore, we identified a drought-inducible gene named OsWRKY104 that is under the direct regulation of OsABF1. Overexpression of OsWRKY104 can suppress Ehd1 expression and confers a later flowering phenotype in rice. Together, these findings reveal a novel pathway by which rice modulates heading date in response to the change of ambient water availability. PMID:26945049

  7. Large drought-induced variations in oak leaf volatile organic compound emissions during PINOT NOIR 2012

    SciTech Connect

    Geron, Chris; Gu, Lianhong; Daly, Ryan; Harley, Peter; Rasmussen, Rei; Seco, Roger; Guenther, Alex; Karl, Thomas

    2015-12-17

    Here, leaf-level isoprene and monoterpene emissions were collected and analyzed from five of the most abundant oak (Quercus) species in Central Missouri's Ozarks Region in 2012 during PINOT NOIR (Particle Investigations at a Northern Ozarks Tower – NOx, Oxidants, Isoprene Research). June measurements, prior to the onset of severe drought, showed isoprene emission rates and leaf temperature responses similar to those previously reported in the literature and used in Biogenic Volatile Organic Compound (BVOC) emission models. During the peak of the drought in August, isoprene emission rates were substantially reduced, and response to temperature was dramatically altered, especially for the species in the red oak subgenus (Erythrobalanus).

  8. Overexpression of Nitrate Reductase in Tobacco Delays Drought-Induced Decreases in Nitrate Reductase Activity and mRNA1

    PubMed Central

    Ferrario-Méry, Sylvie; Valadier, Marie-Hélène; Foyer, Christine H.

    1998-01-01

    Transformed (cauliflower mosaic virus 35S promoter [35S]) tobacco (Nicotiana plumbaginifolia L.) plants constitutively expressing nitrate reductase (NR) and untransformed controls were subjected to drought for 5 d. Drought-induced changes in biomass accumulation and photosynthesis were comparable in both lines of plants. After 4 d of water deprivation, a large increase in the ratio of shoot dry weight to fresh weight was observed, together with a decrease in the rate of photosynthetic CO2 assimilation. Foliar sucrose increased in both lines during water stress, but hexoses increased only in leaves from untransformed controls. Foliar NO3− decreased rapidly in both lines and was halved within 2 d of the onset of water deprivation. Total foliar amino acids decreased in leaves of both lines following water deprivation. After 4 d of water deprivation no NR activity could be detected in leaves of untransformed plants, whereas about 50% of the original activity remained in the leaves of the 35S-NR transformants. NR mRNA was much more stable than NR activity. NR mRNA abundance increased in the leaves of the 35S-NR plants and remained constant in controls for the first 3 d of drought. On the 4th d, however, NR mRNA suddenly decreased in both lines. Rehydration at d 3 caused rapid recovery (within 24 h) of 35S-NR transcripts, but no recovery was observed in the controls. The phosphorylation state of the protein was unchanged by long-term drought. There was a strong correlation between maximal extractable NR activity and ambient photosynthesis in both lines. We conclude that drought first causes increased NR protein turnover and then accelerates NR mRNA turnover. Constitutive NR expression temporarily delayed drought-induced losses in NR activity. 35S-NR expression may therefore allow more rapid recovery of N assimilation following short-term water deficit. PMID:9576799

  9. Chitosan effects on physiochemical indicators of drought-induced leaf stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water deficit stress in crops is associated with leaf senescence, a damaging oxidative process that is irreversible once it is initiated. This study was conducted to assess the effect of chitosan, a marine polysaccharide with unique bioactive properties that scavenges for reactive oxygen species; h...

  10. Large Drought-Induced Variations in Oak Leaf Volatile Organic Compound Emissions during PINOT NOIR 2012

    EPA Science Inventory

    Leaf-level isoprene and monoterpene emissions were collected and analyzed from five of the most abundant oak (Quercus) species in Central Missouri’s Ozarks Region in 2012 during PINOT NOIR (Particle Investigations at a Northern Ozarks Tower ‐ NOx, Oxidants, Isoprene Research). Ju...

  11. Large drought-induced variations in oak leaf volatile organic compound emissions during PINOT NOIR 2012

    DOE PAGESBeta

    Geron, Chris; Gu, Lianhong; Daly, Ryan; Harley, Peter; Rasmussen, Rei; Seco, Roger; Guenther, Alex; Karl, Thomas

    2015-12-17

    Here, leaf-level isoprene and monoterpene emissions were collected and analyzed from five of the most abundant oak (Quercus) species in Central Missouri's Ozarks Region in 2012 during PINOT NOIR (Particle Investigations at a Northern Ozarks Tower – NOx, Oxidants, Isoprene Research). June measurements, prior to the onset of severe drought, showed isoprene emission rates and leaf temperature responses similar to those previously reported in the literature and used in Biogenic Volatile Organic Compound (BVOC) emission models. During the peak of the drought in August, isoprene emission rates were substantially reduced, and response to temperature was dramatically altered, especially for themore » species in the red oak subgenus (Erythrobalanus).« less

  12. Large drought-induced variations in oak leaf volatile organic compound emissions during PINOT NOIR 2012.

    PubMed

    Geron, Chris; Daly, Ryan; Harley, Peter; Rasmussen, Rei; Seco, Roger; Guenther, Alex; Karl, Thomas; Gu, Lianhong

    2016-03-01

    Leaf-level isoprene and monoterpene emissions were collected and analyzed from five of the most abundant oak (Quercus) species in Central Missouri's Ozarks Region in 2012 during PINOT NOIR (Particle Investigations at a Northern Ozarks Tower - NOx, Oxidants, Isoprene Research). June measurements, prior to the onset of severe drought, showed isoprene emission rates and leaf temperature responses similar to those previously reported in the literature and used in Biogenic Volatile Organic Compound (BVOC) emission models. During the peak of the drought in August, isoprene emission rates were substantially reduced, and response to temperature was dramatically altered, especially for the species in the red oak subgenus (Erythrobalanus). Quercus stellata (in the white oak subgenus Leucobalanus), on the other hand, increased its isoprene emission rate during August, and showed no decline at high temperatures during June or August, consistent with its high tolerance to drought and adaptation to xeric sites at the prairie-deciduous forest interface. Mid-late October measurements were conducted after soil moisture recharge, but were affected by senescence and cooler temperatures. Isoprene emission rates were considerably lower from all species compared to June and August data. The large differences between the oaks in response to drought emphasizes the need to consider BVOC emissions at the species level instead of just the whole canopy. Monoterpene emissions from Quercus rubra in limited data were highest among the oaks studied, while monoterpene emissions from the other oak species were 80-95% lower and less than assumed in current BVOC emission models. Major monoterpenes from Q. rubra (and in ambient air) were p-cymene, α-pinene, β-pinene, d-limonene, γ-terpinene, β-ocimene (predominantly1,3,7-trans-β-ocimene, but also 1,3,6-trans-β-ocimene), tricyclene, α-terpinene, sabinene, terpinolene, and myrcene. Results are discussed in the context of canopy flux studies

  13. The contribution of vascular and extra-vascular water pathways to drought-induced decline of leaf hydraulic conductance.

    PubMed

    Trifiló, Patrizia; Raimondo, Fabio; Savi, Tadeja; Lo Gullo, Maria A; Nardini, Andrea

    2016-09-01

    Drought stress can impair leaf hydraulic conductance (Kleaf), but the relative contribution of changes in the efficiency of the vein xylem water pathway and in the mesophyll route outside the xylem in driving the decline of Kleaf is still debated. We report direct measurements of dehydration-induced changes in the hydraulic resistance (R=1/K) of whole leaf (Rleaf), as well as of the leaf xylem (Rx) and extra-vascular pathways (Rox) in four Angiosperm species. Rleaf, Rx, and Rox were measured using the vacuum chamber method (VCM). Rleaf values during progressive leaf dehydration were also validated with measurements performed using the rehydration kinetic method (RKM). We analysed correlations between changes in Rx or Rox and Rleaf, as well as between morpho-anatomical traits (including dehydration-induced leaf shrinkage), vulnerability to embolism, and leaf water relation parameters. Measurements revealed that the relative contribution of vascular and extra-vascular hydraulic properties in driving Kleaf decline during dehydration is species-specific. Whilst in two study species the progressive impairment of both vascular and extra-vascular pathways contributed to leaf hydraulic vulnerability, in the other two species the vascular pathway remained substantially unaltered during leaf dehydration, and Kleaf decline was apparently caused only by changes in the hydraulic properties of the extra-vascular compartment. PMID:27388214

  14. Drought Induces Distinct Growth Response, Protection, and Recovery Mechanisms in the Maize Leaf Growth Zone1[OPEN

    PubMed Central

    Avramova, Viktoriya; AbdElgawad, Hamada; Zhang, Zhengfeng; Fotschki, Bartosz; Casadevall, Romina; Vergauwen, Lucia; Knapen, Dries; Taleisnik, Edith; Guisez, Yves; Asard, Han; Beemster, Gerrit T.S.

    2015-01-01

    Drought is the most important crop yield-limiting factor, and detailed knowledge of its impact on plant growth regulation is crucial. The maize (Zea mays) leaf growth zone offers unique possibilities for studying the spatiotemporal regulation of developmental processes by transcriptional analyses and methods that require more material, such as metabolite and enzyme activity measurements. By means of a kinematic analysis, we show that drought inhibits maize leaf growth by inhibiting cell division in the meristem and cell expansion in the elongation zone. Through a microarray study, we observed the down-regulation of 32 of the 54 cell cycle genes, providing a basis for the inhibited cell division. We also found evidence for an up-regulation of the photosynthetic machinery and the antioxidant and redox systems. This was confirmed by increased chlorophyll content in mature cells and increased activity of antioxidant enzymes and metabolite levels across the growth zone, respectively. We demonstrate the functional significance of the identified transcriptional reprogramming by showing that increasing the antioxidant capacity in the proliferation zone, by overexpression of the Arabidopsis (Arabidopsis thaliana) iron-superoxide dismutase gene, increases leaf growth rate by stimulating cell division. We also show that the increased photosynthetic capacity leads to enhanced photosynthesis upon rewatering, facilitating the often-observed growth compensation. PMID:26297138

  15. Effects of stomatal delays on the economics of leaf gas exchange under intermittent light regimes.

    PubMed

    Vico, Giulia; Manzoni, Stefano; Palmroth, Sari; Katul, Gabriel

    2011-11-01

    • Understory plants are subjected to highly intermittent light availability and their leaf gas exchanges are mediated by delayed responses of stomata and leaf biochemistry to light fluctuations. In this article, the patterns in stomatal delays across biomes and plant functional types were studied and their effects on leaf carbon gains and water losses were quantified. • A database of more than 60 published datasets on stomatal responses to light fluctuations was assembled. To interpret these experimental observations, a leaf gas exchange model was developed and coupled to a novel formulation of stomatal movement energetics. The model was used to test whether stomatal delays optimize light capture for photosynthesis, whilst limiting transpiration and carbon costs for stomatal movement. • The data analysis showed that stomatal opening and closing delays occurred over a limited range of values and were strongly correlated. Plant functional type and climate were the most important drivers of stomatal delays, with faster responses in graminoids and species from dry climates. • Although perfectly tracking stomata would maximize photosynthesis and minimize transpiration at the expense of large opening costs, the observed combinations of opening and closure times appeared to be consistent with a near-optimal balance of carbon gain, water loss and movement costs. PMID:21851359

  16. Drought induces alterations in the stomatal development program in Populus

    PubMed Central

    Campbell, Malcolm M

    2012-01-01

    Much is known about the physiological control of stomatal aperture as a means by which plants adjust to water availability. By contrast, the role played by the modulation of stomatal development to limit water loss has received much less attention. The control of stomatal development in response to water deprivation in the genus Populus is explored here. Drought induced declines in stomatal conductance as well as an alteration in stomatal development in two genotypes of Populus balsamifera. Leaves that developed under water-deficit conditions had lower stomatal indices than leaves that developed under well-watered conditions. Transcript abundance of genes that could hypothetically underpin drought-responsive changes in stomatal development was examined, in two genotypes, across six time points, under two conditions, well-watered and with water deficit. Populus homologues of STOMAGEN, ERECTA (ER), STOMATA DENSITY AND DISTRIBUTION 1 (SDD1), and FAMA had variable transcript abundance patterns congruent with their role in the modulation of stomatal development in response to drought. Conversely, there was no significant variation in transcript abundance between genotypes or treatments for the Populus homologues of YODA (YDA) and TOO MANY MOUTHS (TMM). The findings highlight the role that could be played by stomatal development during leaf expansion as a longer term means by which to limit water loss from leaves. Moreover, the results point to the key roles played by the regulation of the homologues of STOMAGEN, ER, SDD1, and FAMA in the control of this response in poplar. PMID:22760471

  17. A crinkly leaf and delay flowering mutant of tobacco obtained from recoverable satellite-flown seeds

    NASA Astrophysics Data System (ADS)

    Cai, Liu-Ti; Zheng, Shao-Qing; Huang, Xue-Lin

    Dry seeds of Nicotiana tabacum (L) cv. K346 were flown with a recoverable satellite, the Chinese "Shen Zhou III" for 162 h. After spaceflight, a crinkly leaf and delay flowering mutant of tobacco ( T-cldf), which phenotype differed from the ground control (K346), was obtained from the seedlings after 48 d of the recoverable satellite-flown seeds germination. Major characteristics of T-cldf phenotype included crinkly leaf with outgrowth of the adaxial surface among the secondary veins and delay flowering. Amplified fragment length polymorphism (AFLP) analysis showed that five polymorphic bands were detected between T-cldf and ground control. The results suggested that recoverable satellite-flown condition could bring inheritable mutagenic effects on tobacco seeds and maybe used as a tool for accelerating the progress in tobacco breeding.

  18. Redox markers for drought-induced nodule senescence, a process occurring after drought-induced senescence of the lowest leaves in soybean (Glycine max)

    PubMed Central

    Marquez-Garcia, Belén; Shaw, Daniel; Cooper, James William; Karpinska, Barbara; Quain, Marian Dorcas; Makgopa, Eugene Matome; Kunert, Karl; Foyer, Christine Helen

    2015-01-01

    Background and Aims Water is an increasingly scarce resource that limits crop productivity in many parts of the world, and the frequency and severity of drought are predicted to increase as a result of climate change. Improving tolerance to drought stress is therefore important for maximizing future crop yields. The aim of this study was to compare the effects of drought on soybean (Glycine max) leaves and nodules in order to define phenotypic markers and changes in cellular redox state that characterize the stress response in different organs, and to characterize the relationships between leaf and nodule senescence during drought. Methods Leaf and crown nodule metabolite pools were measured together with leaf and soil water contents, and leaf chlorophyll, total protein contents and chlorophyll a fluorescence quenching parameters in nodulated soybeans that were grown under either well-watered conditions or deprived of water for up to 21 d. Key Results Ureides, ascorbate, protein, chlorophyll and the ratios of variable chlorophyll a fluorescence (Fv′) to maximal chlorophyll a fluorescence (Fm′) fell to levels below detection in the oldest leaves after 21 d of drought. While these drought-induced responses were not observed in the youngest leaf ranks, the Fv′/Fm′ ratios, pyridine nucleotide levels and the reduction state of the ascorbate pool were lower in all leaf ranks after 21 d of drought. In contrast to leaves, total nodule protein, pyridine nucleotides, ureides, ascorbate and glutathione contents increased as a result of the drought treatment. However, the nodule ascorbate pool was significantly less reduced as a result of drought. Higher levels of transcripts encoding two peroxiredoxins were detected in nodules exposed to drought stress but senescence-associated transcripts and other mRNAs encoding redox-related proteins were similar under both conditions. Conclusions While the physiological impact of the drought was perceived throughout the

  19. Phosphatidylinositol 3-Kinase Promotes Activation and Vacuolar Acidification and Delays Methyl Jasmonate-Induced Leaf Senescence.

    PubMed

    Liu, Jian; Ji, Yingbin; Zhou, Jun; Xing, Da

    2016-03-01

    PI3K and its product PI3P are both involved in plant development and stress responses. In this study, the down-regulation of PI3K activity accelerated leaf senescence induced by methyl jasmonate (MeJA) and suppressed the activation of vacuolar H(+)-ATPase (V-ATPase). Yeast two-hybrid analyses indicated that PI3K bound to the V-ATPase B subunit (VHA-B). Analysis of bimolecular fluorescence complementation in tobacco guard cells showed that PI3K interacted with VHA-B2 in the tonoplasts. Through the use of pharmacological and genetic tools, we found that PI3K and V-ATPase promoted vacuolar acidification and stomatal closure during leaf senescence. Vacuolar acidification was suppressed by the PIKfyve inhibitor in 35S:AtVPS34-YFP Arabidopsis during MeJA-induced leaf senescence, but the decrease was lower than that in YFP-labeled Arabidopsis. These results suggest that PI3K promotes V-ATPase activation and consequently induces vacuolar acidification and stomatal closure, thereby delaying MeJA-induced leaf senescence. PMID:26739232

  20. Mutation of SPOTTED LEAF3 (SPL3) impairs abscisic acid-responsive signalling and delays leaf senescence in rice

    PubMed Central

    Wang, Seung-Hyun; Lim, Jung-Hyun; Kim, Sang-Sook; Cho, Sung-Hwan; Yoo, Soo-Cheul; Koh, Hee-Jong; Sakuraba, Yasuhito; Paek, Nam-Chon

    2015-01-01

    Lesion mimic mutants commonly display spontaneous cell death in pre-senescent green leaves under normal conditions, without pathogen attack. Despite molecular and phenotypic characterization of several lesion mimic mutants, the mechanisms of the spontaneous formation of cell death lesions remain largely unknown. Here, the rice lesion mimic mutant spotted leaf3 (spl3) was examined. When grown under a light/dark cycle, the spl3 mutant appeared similar to wild-type at early developmental stages, but lesions gradually appeared in the mature leaves close to heading stage. By contrast, in spl3 mutants grown under continuous light, severe cell death lesions formed in developing leaves, even at the seedling stage. Histochemical analysis showed that hydrogen peroxide accumulated in the mutant, likely causing the cell death phenotype. By map-based cloning and complementation, it was shown that a 1-bp deletion in the first exon of Oryza sativa Mitogen-Activated Protein Kinase Kinase Kinase1 (OsMAPKKK1)/OsEDR1/OsACDR1 causes the spl3 mutant phenotype. The spl3 mutant was found to be insensitive to abscisic acid (ABA), showing normal root growth in ABA-containing media and delayed leaf yellowing during dark-induced and natural senescence. Expression of ABA signalling-associated genes was also less responsive to ABA treatment in the mutant. Furthermore, the spl3 mutant had lower transcript levels and activities of catalases, which scavenge hydrogen peroxide, probably due to impairment of ABA-responsive signalling. Finally, a possible molecular mechanism of lesion formation in the mature leaves of spl3 mutant is discussed. PMID:26276867

  1. SnRK1 Phosphorylation of AL2 Delays Cabbage Leaf Curl Virus Infection in Arabidopsis

    PubMed Central

    Shen, Wei; Dallas, Mary Beth; Goshe, Michael B.

    2014-01-01

    ABSTRACT Geminivirus AL2/C2 proteins play key roles in establishing infection and causing disease in their plant hosts. They are involved in viral gene expression, counter host defenses by suppressing transcriptional gene silencing, and interfere with the host signaling involved in pathogen resistance. We report here that begomovirus and curtovirus AL2/C2 proteins interact strongly with host geminivirus Rep-interacting kinases (GRIKs), which are upstream activating kinases of the protein kinase SnRK1, a global regulator of energy and nutrient levels in plants. We used an in vitro kinase system to show that GRIK-activated SnRK1 phosphorylates recombinant AL2/C2 proteins from several begomoviruses and to map the SnRK1 phosphorylation site to serine-109 in the AL2 proteins of two New World begomoviruses: Cabbage Leaf Curl Virus (CaLCuV) and Tomato mottle virus. A CaLCuV AL2 S109D phosphomimic mutation did not alter viral DNA levels in protoplast replication assays. In contrast, the phosphomimic mutant was delayed for symptom development and viral DNA accumulation during infection of Arabidopsis thaliana, demonstrating that SnRK1 contributes to host defenses against CaLCuV. Our observation that serine-109 is not conserved in all AL2/C2 proteins that are SnRK1 substrates in vitro suggested that phosphorylation of viral proteins by plant kinases contributes to the evolution of geminivirus-host interactions. IMPORTANCE Geminiviruses are single-stranded DNA viruses that cause serious diseases in many crops. Dicot-infecting geminiviruses carry genes that encode multifunctional AL2/C2 proteins that are essential for infection. However, it is not clear how AL2/C2 proteins are regulated. Here, we show that the host protein kinase SnRK1, a central regulator of energy balance and nutrient metabolism in plants, phosphorylates serine-109 in AL2 proteins of three subgroups of New World begomoviruses, resulting in a delay in viral DNA accumulation and symptom appearance. Our results

  2. Is drought-induced forest dieback globally increasing?

    NASA Astrophysics Data System (ADS)

    Steinkamp, J.; Hickler, T.

    2013-12-01

    Based on field observations from 88 forest and savannah regions across the world, it has recently been suggested that forest mortality has been increasing as a result of decreasing moisture availability, but it is not yet clear if these observations are representative for forests globally. We used historical climate data and a dynamic global vegetation model (LPJ-GUESS) to assess i.) if the field observations are representative for all forests, ii.) which forests are affected by drought, and iii.) if the LPJ-GUESS model can reproduce the reported mortality events. Using two climate data sets and three drought indices, we identified a minor global drying trend with large variability from 1948 to 2006, but no increase in extreme drought events in forests generally. However, a weak drying trend and an increase in extreme drought events are apparent for forests in already dry climates and savannah areas, and the locations or regions for which drought-induced mortality trends have been reported are predominantly in dry climates. 51% of the reported drought-induced forest mortality events are apparent in the drought indices of the two climatic data sets and 71% is apparent in the simulated mortality with any of the two climate drivers. However, only in 32% of the cases, exceptional drought coincides with simulated increased forest mortality, implying that climatic drought might not be the main driver of all these events. We conclude that an increase in drought-induced mortality in dry forest and savannah areas is indeed likely, but the general trends are not very strong and the spatial variability is large. According to average climate change projections, many already dry forest areas are likely to become even drier in the future, but projections of the impacts of such climatic trends on forest mortality are highly uncertain because forest impact models have not been thoroughly tested against historical events of increased forest mortality. Furthermore, extreme impacts

  3. Mutation of Rice Early Flowering3.1 (OsELF3.1) delays leaf senescence in rice.

    PubMed

    Sakuraba, Yasuhito; Han, Su-Hyun; Yang, Hyun-Jung; Piao, Weilan; Paek, Nam-Chon

    2016-09-01

    In Arabidopsis, EARLY FLOWERING3 (ELF3) has pivotal roles in controlling circadian rhythm and photoperiodic flowering. In addition, ELF3 negatively regulates leaf senescence by repressing the transcription of PHYTOCHROME-INTERACTING FACTOR4 (PIF4) and PHYTOCHROME-INTERACTING FACTOR5 (PIF5); elf3 mutants senesce earlier and ELF3-overexpressing (ELF3-OX) plants senesce later than wild type (WT). Here, we show that in contrast to Arabidopsis ELF3, which represses senescence, the rice homolog OsELF3.1 promotes leaf senescence; oself3.1 mutants showed delayed senescence and OsELF3.1-OX plants senesced earlier under both dark-induced and natural senescence conditions. Microarray analysis revealed that in the senescing leaves, a number of senescence-associated genes, phytohormone-related genes, and NAC and WRKY family genes (OsNAP, ONAC106, and OsWRKY42) were differentially expressed in oself3.1 mutants compared with WT. Interestingly, we found that Arabidopsis plants overexpressing OsELF3.1 show delayed leaf senescence, produce short petioles, and flower late in long days, just like Arabidopsis ELF3-OX plants. This demonstrates that the regulatory functions of ELF3 and OsELF3.1 are conserved between Arabidopsis and rice, but the downstream regulatory cascades have opposite effects. PMID:27380315

  4. Distinguishing warming-induced drought from drought-induced warming

    NASA Astrophysics Data System (ADS)

    Roderick, M. L.; Yin, D.

    2015-12-01

    It is usually observed that temperatures, especially maximum temperatures are higher during drought. A very widely held public perception is that the increase in temperature is a cause of drought. This represents the warming-induced drought scenario. However, the agricultural and hydrologic scientific communities have a very different interpretation with drought being the cause of increasing temperature. In essence, those communities assume the warming is a surface feedback and their interpretation is for drought-induced warming. This is a classic cause-effect problem that has resisted definitive explanation due to the lack of radiative observations at suitable spatial and temporal scales. In this presentation we first summarise the observations and then use theory to untangle the cause-effect relationships that underlie the competing interpretations. We then show how satellite data (CERES, NASA) can be used to disentangle the cause-effect relations.

  5. Mulberry leaf polyphenols delay aging and regulate fat metabolism via the germline signaling pathway in Caenorhabditis elegans.

    PubMed

    Zheng, Shanqing; Liao, Sentai; Zou, Yuxiao; Qu, Zhi; Shen, Weizhi; Shi, Ying

    2014-01-01

    Mulberry leaves are an important ingredient in some traditional Chinese medicinal formulas and has been developed for use in functional food products. The antioxidant activity of mulberry leaf extract has been reported to have beneficial effects on diseases in vitro; however, it is not clear which components in mulberry leaf extracts have these functions. Furthermore, the mechanisms of action of these ingredients have not been extensively investigated. In this study, we extracted total mulberry leaf polyphenols (MLP) and identified its 13 phenolic monomers. Our results, using Caenorhabditis elegans as a model, indicated that MLPs delayed aging, improved oxidative stress resistance, and reduced fatty acid storage in vivo. Subsequent genetic screens and gene expression analyses demonstrated that the functions of MLP mainly depended on the germline signaling pathway, thus influencing the activities of downstream transcription factors (DAF-12, DAF-16, PHA-4, and NHR-80) as well as the expression levels of their target genes (fat-6, lipl-4, sod-3, unc-51, and fard-1). Our study determined that diverse modes of action on longevity were promoted by MLP exposure. These observations provide the first insight into MLP's multifaceted functions on aging, fat accumulation, and reproduction in vivo and indicate a specific model for the mechanism of action of MLP. This is a significant finding that lends support to the hypotheses that mulberry leaf extracts can have an impact on human health. PMID:25323576

  6. Tree ring carbon isotopes record predisposition to drought-induced mortality and survival.

    NASA Astrophysics Data System (ADS)

    McDowell, N.; Allen, C.; Levanič, T.; Marshall, L.

    2009-04-01

    Drought-induced tree mortality is predicted to increase in intensity and frequency in mid-latitude regions over the next 50 years. We report on tree ring records of growth and carbon isotope discrimination in a variety of species from N. America and Europe that demonstrate a consistent pattern of predisposition to mortality during drought. Trees that die show greater sensitivity of growth to climate as has been previously demonstrated. Trees that die; however, have consistently lower discrimination and significantly less sensitivity of discrimination to climate than trees that survive. A simple hydraulic model based on Darcy's law successfully recreated the observed patterns of discrimination, and supports the interpretation that trees that die have consistently lower leaf-level stomatal conductance than trees that survive. Furthermore, the model supports the conclusion that these trees are less responsive to inter-annual climate variation due to chronic water stress. It appears that such chronic water stress predisposes trees to mortality. Consideration of the sensitivity of these isotope records to mesophyll conductance, photosynthetic capacity, photorespiration, and carbon recyling is critical to robust conclusions. Continued intensification of drought in mid-latitude regions may force trees undergoing chronic water stress to undergo increased mortality, resulting in ecotone shifts and regional mortality events in temperate forests.

  7. Detection system of acid rain pollution using light-induced delayed fluorescence of plant leaf in vivo

    NASA Astrophysics Data System (ADS)

    Zeng, Lizhang; Xing, Da

    2006-09-01

    Photosynthetic apparatus is susceptible to environmental stress. Light-induced delayed fluorescence (DF) in plant is an intrinsic label of the efficiency of charge separation at P680 in photosystem II (PS II). In this investigation, we have developed a biosensor that can accurately inspect acid rain pollution by means of DF in vivo. Compared with traditional methods, the proposed technique can continuously monitor environmental changes, making fast, real-time and noninvasive inspection possible. The biosensor is an all-weather measuring instrument; it has its own illumination power and utilizes intrinsic DF as the measurement marker. With soybean (Glycine max (L.) Merr.) seedling as a testing model, which is sensitive to acid rain pollution, the relationship that delayed fluorescence properties and capability of photosynthetic apparatus after being affected by simulated acid rain with different pH value was studied. The current investigation has revealed that the changes of delayed fluorescence (equation available in paper) can probably characterize the pollution degree of simulated acid rain, Inspecting the changes in DF characteristics (φ i) of plant leaf in vivo may be a new approach for the detection of acid rain pollution and its impact on the ecosystem.

  8. A pivotal role of phosphatidylinositol 3-kinase in delaying of methyl jasmonate-induced leaf senescence.

    PubMed

    Liu, Jian; Zhou, Jun; Xing, Da

    2016-06-01

    Phosphatidylinositol 3-kinase (PI3K) and its product PI3P are involved in plant development and stress responses. Our recent report has suggested that down-regulation of PI3K activity accelerated leaf senescence induced by methyl jasmonate (MeJA) and suppressed the activation of vacuolar H(+)-ATPase (V-ATPase). In vitro and in vivo experiment revealed that PI3K interact with VHA-B2. The inhibition of V-ATPase activity suppressed the vacuolar acidification and enhanced the stomatal opening, thereby accelerating MeJA-induced leaf senescence. It was shown that there is close relationship between PI3K and V-ATPase. However, the factor which initiates the PI3K-V-ATPase pathway needs further improvement, and the domain of VHA-B that binds to PI3K is still not clear enough. By using the Arabidopsis and MeJA as the research model, studies have been performed to investigate the upstream regulation of PI3K and downstream function of PI3K-V-ATPase pathway in the plant senescence. PMID:26906642

  9. A Mutation in Plant-Specific SWI2/SNF2-Like Chromatin-Remodeling Proteins, DRD1 and DDM1, Delays Leaf Senescence in Arabidopsis thaliana

    PubMed Central

    Kim, Ji Hong; Kim, Ji Eun; Lee, Min Hee; Chung, Byung Yeoup; Woo, Hye Ryun; Kim, Jin-Hong

    2016-01-01

    Leaf senescence is a finely regulated complex process; however, evidence for the involvement of epigenetic processes in the regulation of leaf senescence is still fragmentary. Therefore, we chose to examine the functions of DRD1, a SWI2/SNF2 chromatin remodeling protein, in epigenetic regulation of leaf senescence, particularly because drd1-6 mutants exhibited a delayed leaf senescence phenotype. Photosynthetic parameters such as Fv/Fm and ETRmax were decreased in WT leaves compared to leaves of drd1-6 mutants after dark treatment. The WT leaves remarkably lost more chlorophyll and protein content during dark-induced senescence (DIS) than the drd1-6 leaves did. The induction of senescence-associated genes was noticeably inhibited in the drd1-6 mutant after 5-d of DIS. We compared changes in epigenetic regulation during DIS via quantitative expression analysis of 180-bp centromeric (CEN) and transcriptionally silent information (TSI) repeats. Their expression levels significantly increased in both the WT and the drd1-6 mutant, but did much less in the latter. Moreover, the delayed leaf senescence was observed in ddm1-2 mutants as well as the drd1-6, but not in drd1-p mutants. These data suggest that SWI2/SNF2 chromatin remodeling proteins such as DRD1 and DDM1 may influence leaf senescence possibly via epigenetic regulation. PMID:26752684

  10. Regulated Expression of a Cytokinin Biosynthesis Gene IPT Delays Leaf Senescence and Improves Yield under Rainfed and Irrigated Conditions in Canola (Brassica napus L.)

    PubMed Central

    Kant, Surya; Burch, David; Badenhorst, Pieter; Palanisamy, Rajasekaran; Mason, John; Spangenberg, German

    2015-01-01

    Delay of leaf senescence through genetic modification can potentially improve crop yield, through maintenance of photosynthetically active leaves for a longer period. Plant growth hormones such as cytokinin regulate and delay leaf senescence. Here, the structural gene (IPT) encoding the cytokinin biosynthetic enzyme isopentenyltransferase was fused to a functionally active fragment of the AtMYB32 promoter and was transformed into canola plants. Expression of the AtMYB32xs::IPT gene cassette delayed the leaf senescence in transgenic plants grown under controlled environment conditions and field experiments conducted for a single season at two geographic locations. The transgenic canola plants retained higher chlorophyll levels for an extended period and produced significantly higher seed yield with similar growth and phenology compared to wild type and null control plants under rainfed and irrigated treatments. The yield increase in transgenic plants was in the range of 16% to 23% and 7% to 16% under rainfed and irrigated conditions, respectively, compared to control plants. Most of the seed quality parameters in transgenic plants were similar, and with elevated oleic acid content in all transgenic lines and higher oil content and lower glucosinolate content in one specific transgenic line as compared to control plants. The results suggest that by delaying leaf senescence using the AtMYB32xs::IPT technology, productivity in crop plants can be improved under water stress and well-watered conditions. PMID:25602960

  11. Trends and Tipping Points of Drought-induced Tree Mortality

    NASA Astrophysics Data System (ADS)

    Huang, K.; Yi, C.; Wu, D.; Zhou, T.; Zhao, X.; Blanford, W. J.; Wei, S.; Wu, H.; Du, L.

    2014-12-01

    Drought-induced tree mortality worldwide has been recently reported in a review of the literature by Allen et al. (2010). However, a quantitative relationship between widespread loss of forest from mortality and drought is still a key knowledge gap. Specifically, the field lacks quantitative knowledge of tipping point in trees when coping with water stress, which inhibits the assessments of how climate change affects the forest ecosystem. We investigate the statistical relationships for different (seven) conifer species between Ring Width Index (RWI) and Standardized Precipitation Evapotranspiration Index (SPEI), based on 411 chronologies from the International Tree-Ring Data Bank across 11 states of the western United States. We found robust species-specific relationships between RWI and SPEI for all seven conifer species at dry condition. The regression models show that the RWI decreases with SPEI decreasing (drying) and more than 76% variation of tree growth (RWI) can be explained by the drought index (SPEI). However, when soil water is sufficient (i.e., SPEI>SPEIu), soil water is no longer a restrictive factor for tree growth and, therefore, the RWI shows a weak correlation with SPEI. Based on the statistical models, we derived the tipping point of SPEI (SPEItp) where the RWI equals 0, which means the carbon efflux by tree respiration equals carbon influx by tree photosynthesis. When the severity of drought exceeds this tipping point(i.e. SPEI

  12. The Thiol Reductase Activity of YUCCA6 Mediates Delayed Leaf Senescence by Regulating Genes Involved in Auxin Redistribution.

    PubMed

    Cha, Joon-Yung; Kim, Mi R; Jung, In J; Kang, Sun B; Park, Hee J; Kim, Min G; Yun, Dae-Jin; Kim, Woe-Yeon

    2016-01-01

    Auxin, a phytohormone that affects almost every aspect of plant growth and development, is biosynthesized from tryptophan via the tryptamine, indole-3-acetamide, indole-3-pyruvic acid, and indole-3-acetaldoxime pathways. YUCCAs (YUCs), flavin monooxygenase enzymes, catalyze the conversion of indole-3-pyruvic acid (IPA) to the auxin (indole acetic acid). Arabidopsis thaliana YUC6 also exhibits thiol-reductase and chaperone activity in vitro; these activities require the highly conserved Cys-85 and are essential for scavenging of toxic reactive oxygen species (ROS) in the drought tolerance response. Here, we examined whether the YUC6 thiol reductase activity also participates in the delay in senescence observed in YUC6-overexpressing (YUC6-OX) plants. YUC6 overexpression delays leaf senescence in natural and dark-induced senescence conditions by reducing the expression of SENESCENCE-ASSOCIATED GENE 12 (SAG12). ROS accumulation normally occurs during senescence, but was not observed in the leaves of YUC6-OX plants; however, ROS accumulation was observed in YUC6-OX(C85S) plants, which overexpress a mutant YUC6 that lacks thiol reductase activity. We also found that YUC6-OX plants, but not YUC6-OX(C85S) plants, show upregulation of three genes encoding NADPH-dependent thioredoxin reductases (NTRA, NTRB, and NTRC), and GAMMA-GLUTAMYLCYSTEINE SYNTHETASE 1 (GSH1), encoding an enzyme involved in redox signaling. We further determined that excess ROS accumulation caused by methyl viologen treatment or decreased glutathione levels caused by buthionine sulfoximine treatment can decrease the levels of auxin efflux proteins such as PIN2-4. The expression of PINs is also reduced in YUC6-OX plants. These findings suggest that the thiol reductase activity of YUC6 may play an essential role in delaying senescence via the activation of genes involved in redox signaling and auxin availability. PMID:27242830

  13. The Thiol Reductase Activity of YUCCA6 Mediates Delayed Leaf Senescence by Regulating Genes Involved in Auxin Redistribution

    PubMed Central

    Cha, Joon-Yung; Kim, Mi R.; Jung, In J.; Kang, Sun B.; Park, Hee J.; Kim, Min G.; Yun, Dae-Jin; Kim, Woe-Yeon

    2016-01-01

    Auxin, a phytohormone that affects almost every aspect of plant growth and development, is biosynthesized from tryptophan via the tryptamine, indole-3-acetamide, indole-3-pyruvic acid, and indole-3-acetaldoxime pathways. YUCCAs (YUCs), flavin monooxygenase enzymes, catalyze the conversion of indole-3-pyruvic acid (IPA) to the auxin (indole acetic acid). Arabidopsis thaliana YUC6 also exhibits thiol-reductase and chaperone activity in vitro; these activities require the highly conserved Cys-85 and are essential for scavenging of toxic reactive oxygen species (ROS) in the drought tolerance response. Here, we examined whether the YUC6 thiol reductase activity also participates in the delay in senescence observed in YUC6-overexpressing (YUC6-OX) plants. YUC6 overexpression delays leaf senescence in natural and dark-induced senescence conditions by reducing the expression of SENESCENCE-ASSOCIATED GENE 12 (SAG12). ROS accumulation normally occurs during senescence, but was not observed in the leaves of YUC6-OX plants; however, ROS accumulation was observed in YUC6-OXC85S plants, which overexpress a mutant YUC6 that lacks thiol reductase activity. We also found that YUC6-OX plants, but not YUC6-OXC85S plants, show upregulation of three genes encoding NADPH-dependent thioredoxin reductases (NTRA, NTRB, and NTRC), and GAMMA-GLUTAMYLCYSTEINE SYNTHETASE 1 (GSH1), encoding an enzyme involved in redox signaling. We further determined that excess ROS accumulation caused by methyl viologen treatment or decreased glutathione levels caused by buthionine sulfoximine treatment can decrease the levels of auxin efflux proteins such as PIN2-4. The expression of PINs is also reduced in YUC6-OX plants. These findings suggest that the thiol reductase activity of YUC6 may play an essential role in delaying senescence via the activation of genes involved in redox signaling and auxin availability. PMID:27242830

  14. Sorghum stay-green QTL individually reduce post-flowering drought-induced leaf senescence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sorghum is an important source of food and feed, especially in the semi-arid tropics because this cereal is well adapted to harsh, drought-prone environments. Post-flowering drought adaptation in sorghum is associated with the stay-green phenotype. Alleles that contribute to this complex trait hav...

  15. Runoff and erosional response to a drought-induced shift in a desert grassland community composition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study investigates how drought-induced change in semiarid grassland community composition affected runoff and sediment yield in a small 1.8 ha watershed in southeast Arizona, USA. Three distinct periods in ecosystem composition and associated runoff and sediment yield were identified according ...

  16. Vulnerability to drought-induced cavitation in poplars: synthesis and future opportunities.

    PubMed

    Fichot, Régis; Brignolas, Franck; Cochard, Hervé; Ceulemans, Reinhart

    2015-07-01

    Vulnerability to drought-induced cavitation is a key trait of plant water relations. Here, we summarize the available literature on vulnerability to drought-induced cavitation in poplars (Populus spp.), a genus of agronomic, ecological and scientific importance. Vulnerability curves and vulnerability parameters (including the water potential inducing 50% loss in hydraulic conductivity, P50) were collected from 37 studies published between 1991 and 2014, covering a range of 10 species and 12 interspecific hybrid crosses. Results of our meta-analysis confirm that poplars are among the most vulnerable woody species to drought-induced cavitation (mean P50  = -1.44 and -1.55 MPa across pure species and hybrids, respectively). Yet, significant variation occurs among species (P50 range: 1.43 MPa) and among hybrid crosses (P50 range: 1.12 MPa), within species and hybrid crosses (max. P50 range reported: 0.8 MPa) as well as in response to environmental factors including nitrogen fertilization, irradiance, temperature and drought (max. P50 range reported: 0.75 MPa). Potential implications and gaps in knowledge are discussed in the context of poplar cultivation, species adaptation and climate modifications. We suggest that poplars represent a valuable model for studies on drought-induced cavitation, especially to elucidate the genetic and molecular basis of cavitation resistance in Angiosperms. PMID:25444560

  17. Drought-induced vegetation shifts in terrestrial ecosystems: The key role of regeneration dynamics

    NASA Astrophysics Data System (ADS)

    Martínez-Vilalta, Jordi; Lloret, Francisco

    2016-09-01

    Ongoing climate change is modifying climatic conditions worldwide, with a trend towards drier conditions in most regions. Vegetation will respond to these changes, eventually adjusting to the new climate. It is unclear, however, how close different ecosystems are to climate-related tipping points and, thus, how dramatic these vegetation changes will be in the short- to mid-term, given the existence of strong stabilizing processes. Here, we review the published evidence for recent drought-induced vegetation shifts worldwide, addressing the following questions: (i) what are the necessary conditions for vegetation shifts to occur? (ii) How much evidence of drought-induced vegetation shifts do we have at present and where are they occurring? (iii) What are the main processes that favor/oppose the occurrence of shifts at different ecological scales? (iv) What are the complications in detecting and attributing drought-induced vegetation shifts? (v) What ecological factors can interact with drought to promote shifts or stability? We propose a demographic framework to classify the likely outcome of instances of drought-induced mortality, based upon the survival of adults of potential replacement species and the regeneration of both formerly dominant affected species and potential replacement species. Out of 35 selected case studies only eight were clearly consistent with the occurrence of a vegetation shift (species or biome shift), whereas three corresponded to self-replacements in which the affected, formerly dominant species was able to regenerate after suffering drought-induced mortality. The other 24 cases were classified as uncertain, either due to lack of information or, more commonly, because the initially affected and potential replacement species all showed similar levels of regeneration after the mortality event. Overall, potential vegetation transitions were consistent with more drought-resistant species replacing less resistant ones. However, almost half (44

  18. Drought-induced Changes in Dryland Soil Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Belnap, J.; Darrouzet-Nardi, A.; Duniway, M.; Ferrenberg, S.; Hoover, D. L.; Reed, S.

    2015-12-01

    Approximately 41% of Earth´s terrestrial surface consists of drylands and they are an important biome on all continents. Although dryland biota would be expected to be drought adapted, they can be surprisingly vulnerable to extended dry periods with subsequent consequences for biogeochemical cycles. Biological soil crusts, constituting up to 70% of the living cover in these regions, are important in these cycles. They fix both N and C, providing a significant percentage of regional and global inputs. However, extended drought reduces both types of inputs, as biocrusts are only metabolically active when wet, yet losses continue even when soils are dry. In addition, extended droughts can result in their mortality. The amount of net soil C exchange of biocrusted soils is controversial, but in SE Utah, soil C uptake only occurred when only when soils were wet. As soils are infrequently wet, annual balances were negative during the 2 year study and with future extended droughts or increased temperatures that reduce soil moisture, these losses will become even greater. As with C, N fixation also requires biocrusts be wet and thus inputs decline with extended drought or higher temperatures that both reduce input and result in lichen and cyanobacterial mortality. And similarly, N losses continue even when soils are dry. Loss of biocrust mosses can profoundly alter N cycles. Desert plants are also affected by drought: in plots where experimental drought was imposed, plants had lower photosynthetic rates and higher leaf C:N, which will likely affect productivity and decomposition rates and thus have further impacts on soil biogeochemical cycles.

  19. Green Leaf Volatile Emissions during High Temperature and Drought Stress in a Central Amazon Rainforest.

    PubMed

    Jardine, Kolby J; Chambers, Jeffrey Q; Holm, Jennifer; Jardine, Angela B; Fontes, Clarissa G; Zorzanelli, Raquel F; Meyers, Kimberly T; de Souza, Vinicius Fernadez; Garcia, Sabrina; Gimenez, Bruno O; Piva, Luani R de O; Higuchi, Niro; Artaxo, Paulo; Martin, Scot; Manzi, Antônio O

    2015-01-01

    Prolonged drought stress combined with high leaf temperatures can induce programmed leaf senescence involving lipid peroxidation, and the loss of net carbon assimilation during early stages of tree mortality. Periodic droughts are known to induce widespread tree mortality in the Amazon rainforest, but little is known about the role of lipid peroxidation during drought-induced leaf senescence. In this study, we present observations of green leaf volatile (GLV) emissions during membrane peroxidation processes associated with the combined effects of high leaf temperatures and drought-induced leaf senescence from individual detached leaves and a rainforest ecosystem in the central Amazon. Temperature-dependent leaf emissions of volatile terpenoids were observed during the morning, and together with transpiration and net photosynthesis, showed a post-midday depression. This post-midday depression was associated with a stimulation of C₅ and C₆ GLV emissions, which continued to increase throughout the late afternoon in a temperature-independent fashion. During the 2010 drought in the Amazon Basin, which resulted in widespread tree mortality, green leaf volatile emissions (C₆ GLVs) were observed to build up within the forest canopy atmosphere, likely associated with high leaf temperatures and enhanced drought-induced leaf senescence processes. The results suggest that observations of GLVs in the tropical boundary layer could be used as a chemical sensor of reduced ecosystem productivity associated with drought stress. PMID:27135346

  20. Green Leaf Volatile Emissions during High Temperature and Drought Stress in a Central Amazon Rainforest

    PubMed Central

    Jardine, Kolby J.; Chambers, Jeffrey Q.; Holm, Jennifer; Jardine, Angela B.; Fontes, Clarissa G.; Zorzanelli, Raquel F.; Meyers, Kimberly T.; de Souza, Vinicius Fernadez; Garcia, Sabrina; Gimenez, Bruno O.; de O. Piva, Luani R.; Higuchi, Niro; Artaxo, Paulo; Martin, Scot; Manzi, Antônio O.

    2015-01-01

    Prolonged drought stress combined with high leaf temperatures can induce programmed leaf senescence involving lipid peroxidation, and the loss of net carbon assimilation during early stages of tree mortality. Periodic droughts are known to induce widespread tree mortality in the Amazon rainforest, but little is known about the role of lipid peroxidation during drought-induced leaf senescence. In this study, we present observations of green leaf volatile (GLV) emissions during membrane peroxidation processes associated with the combined effects of high leaf temperatures and drought-induced leaf senescence from individual detached leaves and a rainforest ecosystem in the central Amazon. Temperature-dependent leaf emissions of volatile terpenoids were observed during the morning, and together with transpiration and net photosynthesis, showed a post-midday depression. This post-midday depression was associated with a stimulation of C5 and C6 GLV emissions, which continued to increase throughout the late afternoon in a temperature-independent fashion. During the 2010 drought in the Amazon Basin, which resulted in widespread tree mortality, green leaf volatile emissions (C6 GLVs) were observed to build up within the forest canopy atmosphere, likely associated with high leaf temperatures and enhanced drought-induced leaf senescence processes. The results suggest that observations of GLVs in the tropical boundary layer could be used as a chemical sensor of reduced ecosystem productivity associated with drought stress. PMID:27135346

  1. Growth at elevated CO2 delays the adverse effects of drought stress on leaf photosynthesis of the C4 sugarcane

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sugarcane was grown in sunlit greenhouses at 360 and 720 ppm CO2, and drought was imposed for 13 days on 4-month old plants. Leaf CO2 exchange rate (CER) and activity of Rubisco were marginally affected by high CO2 but were reduced by drought, whereas activity of PEP carboxylase was reduced by high ...

  2. Research frontiers in drought-induced tree mortality: Crossing scales and disciplines

    SciTech Connect

    Hartmann, Henrik; Adams, Henry D.; Anderegg, William R. L.; Jansen, Steven; Zeppel, Melanie J. B.

    2015-01-12

    Sudden and widespread forest die-back and die-off (e.g., Huang & Anderegg, 2012) and increased mortality rates (e.g., Peng et al., 2011) in many forest ecosystems across the globe have been linked to drought and elevated temperatures (Allen et al., 2010, Fig. 1). Furthermore, these observations have caused a focus on the physiological mechanisms of drought-induced tree mortality (e.g. McDowell et al., 2008) and many studies, both observational and manipulative, have been carried out to explain tree death during drought from a physiological perspective.

  3. Multiyear drought-induced morbidity preceding tree death in southeastern U.S. forests.

    PubMed

    Berdanier, Aaron B; Clark, James S

    2016-01-01

    Recent forest diebacks, combined with threats of future drought, focus attention on the extent to which tree death is caused by catastrophic events as opposed to chronic declines in health that accumulate over years. While recent attention has focused on large-scale diebacks, there is concern that increasing drought stress and chronic morbidity may have pervasive impacts on forest composition in many regions. Here we use long-term, whole-stand inventory data from southeastern U.S. forests to show that trees exposed to drought experience multiyear declines in growth prior to mortality. Following a severe, multiyear drought, 72% of trees that did not recover their pre-drought growth rates died within 10 yr. This pattern was mediated by local moisture availability. As an index of morbidity prior to death, we calculated the difference in cumulative growth after drought relative to surviving conspecifics. The strength of drought-induced morbidity varied among species and was correlated with drought tolerance. These findings support the ability of trees to avoid death during drought events but indicate shifts that could occur over decades. Tree mortality following drought is predictable in these ecosystems based on growth declines, highlighting an opportunity to address multiyear drought-induced morbidity in models, experiments, and management decisions. PMID:27039506

  4. Predicting drought-induced tree mortality in the western United States

    NASA Astrophysics Data System (ADS)

    Anderegg, W.; Wolf, A.; Shevliakova, E.; Pacala, S. W.

    2015-12-01

    Projected responses of forest ecosystems to warming and drying associated with 21st century climate change vary widely from resiliency to widespread dieback. A major shortcoming of current vegetation models is the inability to account for mortality of overstory trees during extreme drought due to uncertainties in mechanisms and thresholds. In this talk, I discuss two modeling efforts to predict drought-induced tree mortality in the western United States. In the first, we identify a lethal drought threshold in the loss of vascular transport capacity from xylem cavitation, which provides insight into what initiates mortality, in Populus tremuloides in the southwestern United States. We then use the hydraulic-based threshold to produce a hindcast of a drought-induced forest dieback and compare predictions against three independent regional mortality datasets. The hydraulic threshold predicted major regional patterns of tree mortality with high accuracy based on field plots and mortality maps derived from Landsat imagery. Climate model simulations project increasing drought stress in this region that exceeds the observed mortality threshold in the high emissions scenario by the 2050s, likely triggering further widespread diebacks. In the second approach, we build a dynamic plant hydraulic model into a land-surface model and compare predictions against observed mortality patterns across multiple species. These methods provide powerful and tractable approaches for incorporating tree mortality into vegetation models to resolve uncertainty over the fate of forest ecosystems in a changing climate.

  5. In Vivo Visualizations of Drought-Induced Embolism Spread in Vitis vinifera1[W][OA

    PubMed Central

    Brodersen, Craig Robert; McElrone, Andrew Joseph; Choat, Brendan; Lee, Eric Franklin; Shackel, Kenneth Andrew; Matthews, Mark Allen

    2013-01-01

    Long-distance water transport through plant xylem is vulnerable to hydraulic dysfunction during periods of increased tension on the xylem sap, often coinciding with drought. While the effects of local and systemic embolism on plant water transport and physiology are well documented, the spatial patterns of embolism formation and spread are not well understood. Using a recently developed nondestructive diagnostic imaging tool, high-resolution x-ray computed tomography, we documented the dynamics of drought-induced embolism in grapevine (Vitis vinifera) plants in vivo, producing the first three-dimensional, high-resolution, time-lapse observations of embolism spread. Embolisms formed first in the vessels surrounding the pith at stem water potentials of approximately –1.2 megapascals in drought experiments. As stem water potential decreased, embolisms spread radially toward the epidermis within sectored vessel groupings via intervessel connections and conductive xylem relays, and infrequently (16 of 629 total connections) through lateral connections into adjacent vessel sectors. Theoretical loss of conductivity calculated from the high-resolution x-ray computed tomography images showed good agreement with previously published nuclear magnetic resonance imaging and hydraulic conductivity experiments also using grapevine. Overall, these data support a growing body of evidence that xylem organization is critically important to the isolation of drought-induced embolism spread and confirm that air seeding through the pit membranes is the principle mechanism of embolism spread. PMID:23463781

  6. Drought-induced site-specific DNA methylation and its association with drought tolerance in rice (Oryza sativa L.)

    PubMed Central

    Wang, Wen-Sheng; Pan, Ya-Jiao; Zhao, Xiu-Qin; Dwivedi, D.; Zhu, Ling-Hua; Ali, J.; Fu, Bin-Ying; Li, Zhi-Kang

    2011-01-01

    An indica pyramiding line, DK151, and its recurrent parent, IR64, were evaluated under drought stress and non-stress conditions for three consecutive seasons. DK151 showed significantly improved tolerance to drought. The DNA methylation changes in DK151 and IR64 under drought stress and subsequent recovery were assessed using methylation-sensitive amplified polymorphism analysis. Our results indicate that drought-induced genome-wide DNA methylation changes accounted for ∼12.1% of the total site-specific methylation differences in the rice genome. This drought-induced DNA methylation pattern showed three interesting properties. The most important one was its genotypic specificity reflected by large differences in the detected DNA methylation/demethylation sites between DK151 and IR64, which result from introgressed genomic fragments in DK151. Second, most drought-induced methylation/demethylation sites were of two major types distinguished by their reversibility, including 70% of the sites at which drought-induced epigenetic changes were reversed to their original status after recovery, and 29% of sites at which the drought-induced DNA demethylation/methylation changes remain even after recovery. Third, the drought-induced DNA methylation alteration showed a significant level of developmental and tissue specificity. Together, these properties are expected to have contributed greatly to rice response and adaptation to drought stress. Thus, induced epigenetic changes in rice genome can be considered as a very important regulatory mechanism for rice plants to adapt to drought and possibly other environmental stresses. PMID:21193578

  7. Who Died, Where? Quantification of Drought-Induced Tree Mortality in Texas

    NASA Astrophysics Data System (ADS)

    Schwantes, A.; Swenson, J. J.; Johnson, D. M.; Domec, J. C.; Jackson, R. B.

    2014-12-01

    During 2011, Texas experienced a severe drought that killed millions of trees across the state. Drought-induced tree mortality can have significant ecological impacts and is expected to increase with climate change. We identify methods to quantify tree mortality in central Texas by using remotely sensed images before and after the drought at multiple spatial resolutions. Fine-scale tree mortality maps were created by classifying 1-m orthophotos from the National Agriculture Imagery Program. These classifications showed a high correlation with field estimates of percent canopy loss (RMSE = 2%; R2=0.9), and were thus used to calibrate coarser scale 30-m Landsat imagery. Random Forest, a machine learning method, was applied to obtain sub-pixel estimates of tree mortality. Traditional per-pixel classification techniques can map mortality of whole stands of trees (e.g. fire). However, these methods are often inadequate in detecting subtle changes in land cover, such as those associated with drought-induced tree mortality, which is often a widespread but scattered disturbance. Our method is unique, because it is capable of mapping death of individual canopies within a pixel. These 30-m tree mortality maps were then used to identify ecological systems most impacted by the drought and edaphic factors that control spatial distributions of tree mortality across central Texas. Ground observations coupled with our remote sensing analyses revealed that the majority of the mortality was Juniperus ashei. From a physiological standpoint this is surprising, because J. ashei is a drought-resistant tree. However, over the last century, this species has recently encroached into many areas previously dominated by grassland. Also, J. ashei tends to occupy landscape positions with lower available water storage, which could explain its high mortality rate. Predominantly tree mortality occurred in dry landscape positions (e.g. areas dominated by shallow soils, a low compound topographic

  8. Leaf senescence is delayed in tobacco plants expressing the maize knotted1 gene under the control of a wound-inducible promoter.

    PubMed

    Luo, Keming; Deng, Wei; Xiao, Yuehua; Zheng, Xuelian; Li, Yi; Pei, Yan

    2006-11-01

    To extend the shelf life of freshly harvested vegetables and cut flowers, a maize homeobox gene Knotted1 (kn1) was placed under the control of a wound-inducible promoter win3.12 from hybrid poplar (Populus trichocarpa x P. deltoides) and introduced into tobacco plants (Nicotiana tabacum cv. Xanthi). Transgenic win3.12::kn1 plants were morphologically normal. A leaf-detachment assay demonstrated that senescence in win3.12::kn1 leaves could be delayed by at least 2 weeks compared with wild type leaves. Furthermore, all leaves of win3.12::kn1 shoots remained green and healthy 3 weeks after excision and incubation in water, while older leaves of control shoots senesced under the same conditions. Additionally, a number of adventitious roots produced at the cut ends of wild type shoots after a 3-week incubation, but much a less number of adventitious roots appeared in win3.12::kn1 shoots. The delay in senescence was also confirmed by a higher total chlorophyll (a + b) content in win3.12::kn1 leaves relative to that of the control plants. RT-PCR analysis showed that the kn1 transcript was detected in win3.12::kn1 leaves with wounding treatment, but otherwise was not observed in leaves of wild type and unwounded transgenic plants. The results presented here indicate that expression of kn1 gene driven by the wound-inducible promoter win3.12 is potentially useful to delay senescence of vegetable crops and commercial horticulture after harvest. PMID:16794826

  9. Approaches to modeling landscape-scale drought-induced forest mortality

    USGS Publications Warehouse

    Gustafson, Eric J.; Shinneman, Douglas

    2015-01-01

    Drought stress is an important cause of tree mortality in forests, and drought-induced disturbance events are projected to become more common in the future due to climate change. Landscape Disturbance and Succession Models (LDSM) are becoming widely used to project climate change impacts on forests, including potential interactions with natural and anthropogenic disturbances, and to explore the efficacy of alternative management actions to mitigate negative consequences of global changes on forests and ecosystem services. Recent studies incorporating drought-mortality effects into LDSMs have projected significant potential changes in forest composition and carbon storage, largely due to differential impacts of drought on tree species and interactions with other disturbance agents. In this chapter, we review how drought affects forest ecosystems and the different ways drought effects have been modeled (both spatially and aspatially) in the past. Building on those efforts, we describe several approaches to modeling drought effects in LDSMs, discuss advantages and shortcomings of each, and include two case studies for illustration. The first approach features the use of empirically derived relationships between measures of drought and the loss of tree biomass to drought-induced mortality. The second uses deterministic rules of species mortality for given drought events to project changes in species composition and forest distribution. A third approach is more mechanistic, simulating growth reductions and death caused by water stress. Because modeling of drought effects in LDSMs is still in its infancy, and because drought is expected to play an increasingly important role in forest health, further development of modeling drought-forest dynamics is urgently needed.

  10. Overexpression of Medicago sativa TMT elevates the α-tocopherol content in Arabidopsis seeds, alfalfa leaves, and delays dark-induced leaf senescence.

    PubMed

    Jiang, Jishan; Jia, Huili; Feng, Guangyan; Wang, Zan; Li, Jun; Gao, Hongwen; Wang, Xuemin

    2016-08-01

    Alfalfa (Medicago sativa L.) is a major forage legume for livestock and a target for improving their dietary quality. Vitamin E is an essential vitamin that animals must obtain from their diet for proper growth and development. γ-tocopherol methyltransferase (γ-TMT), which catalyzes the conversion of δ- and γ-tocopherols (or tocotrienols) to β- and α-tocopherols (or tocotrienols), respectively, is the final enzyme involved in the vitamin E biosynthetic pathway. The overexpression of M. sativa L.'s γ-TMT (MsTMT) increased the α-tocopherol content 10-15 fold above that of wild type Arabidopsis seeds without altering the total content of vitamin E. Additionally, in response to osmotic stress, the biomass and the expression levels of several osmotic marker genes were significantly higher in the transgenic lines compared with wild type. Overexpression of MsTMT in alfalfa led to a modest, albeit significant, increase in α-tocopherol in leaves and was also responsible for a delayed leaf senescence phenotype. Additionally, the crude protein content was increased, while the acid and neutral detergent fiber contents were unchanged in these transgenic lines. Thus, increased α-tocopherol content occurred in transgenic alfalfa without compromising the nutritional qualities. The targeted metabolic engineering of vitamin E biosynthesis through MsTMT overexpression provides a promising approach to improve the α-tocopherol content of forage crops. PMID:27297993

  11. Regional Estimates of Drought-Induced Tree Canopy Loss across Texas

    NASA Astrophysics Data System (ADS)

    Schwantes, A.; Swenson, J. J.; González-Roglich, M.; Johnson, D. M.; Domec, J. C.; Jackson, R. B.

    2015-12-01

    The severe drought of 2011 killed millions of trees across the state of Texas. Drought-induced tree-mortality can have significant impacts to carbon cycling, regional biophysics, and community composition. We quantified canopy cover loss across the state using remotely sensed imagery from before and after the drought at multiple scales. First, we classified ~200 orthophotos (1-m spatial resolution) from the National Agriculture Imagery Program, using a supervised maximum likelihood classification. Area of canopy cover loss in these classifications was highly correlated (R2 = 0.8) with ground estimates of canopy cover loss, measured in 74 plots across 15 different sites in Texas. These 1-m orthophoto classifications were then used to calibrate and validate coarser scale (30-m) Landsat imagery to create wall-to-wall tree canopy cover loss maps across the state of Texas. We quantified percent dead and live canopy within each pixel of Landsat to create continuous maps of dead and live tree cover, using two approaches: (1) a zero-inflated beta distribution model and (2) a random forest algorithm. Widespread canopy loss occurred across all the major natural systems of Texas, with the Edwards Plateau region most affected. In this region, on average, 10% of the forested area was lost due to the 2011 drought. We also identified climatic thresholds that controlled the spatial distribution of tree canopy loss across the state. However, surprisingly, there were many local hot spots of canopy loss, suggesting that not only climatic factors could explain the spatial patterns of canopy loss, but rather other factors related to soil, landscape, management, and stand density also likely played a role. As increases in extreme droughts are predicted to occur with climate change, it will become important to define methods that can detect associated drought-induced tree mortality across large regions. These maps could then be used (1) to quantify impacts to carbon cycling and regional

  12. Strong resilience of soil respiration components to drought-induced die-off resulting in forest secondary succession.

    PubMed

    Barba, Josep; Curiel Yuste, Jorge; Poyatos, Rafael; Janssens, Ivan A; Lloret, Francisco

    2016-09-01

    How forests cope with drought-induced perturbations and how the dependence of soil respiration on environmental and biological drivers is affected in a warming and drying context are becoming key questions. The aims of this study were to determine whether drought-induced die-off and forest succession were reflected in soil respiration and its components and to determine the influence of climate on the soil respiration components. We used the mesh exclusion method to study seasonal variations in soil respiration (R S) and its components: heterotrophic (R H) and autotrophic (R A) [further split into fine root (R R) and mycorrhizal respiration (R M)] in a mixed Mediterranean forest where Scots pine (Pinus sylvestris L.) is undergoing a drought-induced die-off and is being replaced by holm oak (Quercus ilex L.). Drought-induced pine die-off was not reflected in R S nor in its components, which denotes a high functional resilience of the plant and soil system to pine die-off. However, the succession from Scots pine to holm oak resulted in a reduction of R H and thus in an important decrease of total respiration (R S was 36 % lower in holm oaks than in non-defoliated pines). Furthermore, R S and all its components were strongly regulated by soil water content-and-temperature interaction. Since Scots pine die-off and Quercus species colonization seems to be widely occurring at the driest limit of the Scots pine distribution, the functional resilience of the soil system over die-off and the decrease of R S from Scots pine to holm oak could have direct consequences for the C balance of these ecosystems. PMID:26879544

  13. Modelling drought-induced dieback of Aleppo pine at the arid timberline

    NASA Astrophysics Data System (ADS)

    Wingate, Lisa; Preisler, Yakir; Bert, Didier; Rotenberg, Eyal; Yakir, Dan; Maseyk, Kadmiel; Ogee, Jerome

    2016-04-01

    During the mid 1960's an ambitious afforestation programme was initiated in the Negev desert of Israel. After five decades enduring harsh growing conditions, the Aleppo pine forest of Yatir is now exhibiting signs of 'drought-induced' dieback. Since 2010, 5-10% of the entire Yatir population have died, however the pattern of mortality is extremely patchy with some areas exhibiting >80% mortality whilst others display none. In this presentation, we reflect on historic climatic and edaphic conditions that have triggered this landscape mosaic of survival and mortality and how physiological and hydraulic traits vary within this patchwork. In addition, we explore how these pine trees have responded physiologically over recent years (1996-2010) to a series of severe drought events using a combined approach that brings together micrometeorological, dendro-isotopic and dendro-climatological datasets alongside process-based modelling. In particular the dataset trends were investigated with the isotope-enabled ecosystem model MuSICA to explore the consequences of subsequent droughts and embolism on modelled carbohydrate and water pool dynamics and their impact on carbon allocation and ecosystem function.

  14. Regional drought-induced reduction in the biomass carbon sink of Canada's boreal forests.

    PubMed

    Ma, Zhihai; Peng, Changhui; Zhu, Qiuan; Chen, Huai; Yu, Guirui; Li, Weizhong; Zhou, Xiaolu; Wang, Weifeng; Zhang, Wenhua

    2012-02-14

    The boreal forests, identified as a critical "tipping element" of the Earth's climate system, play a critical role in the global carbon budget. Recent findings have suggested that terrestrial carbon sinks in northern high-latitude regions are weakening, but there has been little observational evidence to support the idea of a reduction of carbon sinks in northern terrestrial ecosystems. Here, we estimated changes in the biomass carbon sink of natural stands throughout Canada's boreal forests using data from long-term forest permanent sampling plots. We found that in recent decades, the rate of biomass change decreased significantly in western Canada (Alberta, Saskatchewan, and Manitoba), but there was no significant trend for eastern Canada (Ontario and Quebec). Our results revealed that recent climate change, and especially drought-induced water stress, is the dominant cause of the observed reduction in the biomass carbon sink, suggesting that western Canada's boreal forests may become net carbon sources if the climate change-induced droughts continue to intensify. PMID:22308340

  15. Drought-induced xylem cavitation and hydraulic deterioration: risk factors for urban trees under climate change?

    PubMed

    Savi, Tadeja; Bertuzzi, Stefano; Branca, Salvatore; Tretiach, Mauro; Nardini, Andrea

    2015-02-01

    Urban trees help towns to cope with climate warming by cooling both air and surfaces. The challenges imposed by the urban environment, with special reference to low water availability due to the presence of extensive pavements, result in high rates of mortality of street trees, that can be increased by climatic extremes. We investigated the water relations and xylem hydraulic safety/efficiency of Quercus ilex trees growing at urban sites with different percentages of surrounding impervious pavements. Seasonal changes of plant water potential and gas exchange, vulnerability to cavitation and embolism level, and morpho-anatomical traits were measured. We found patterns of increasing water stress and vulnerability to drought at increasing percentages of impervious pavement cover, with a consequent reduction in gas exchange rates, decreased safety margins toward embolism development, and increased vulnerability to cavitation, suggesting the occurrence of stress-induced hydraulic deterioration. The amount of impermeable surface and chronic exposure to water stress influence the site-specific risk of drought-induced dieback of urban trees under extreme drought. Besides providing directions for management of green spaces in towns, our data suggest that xylem hydraulics is key to a full understanding of the responses of urban trees to global change. PMID:25354036

  16. Runoff and erosional responses to a drought-induced shift in a desert grassland community composition

    NASA Astrophysics Data System (ADS)

    Polyakov, V. O.; Nearing, M. A.; Stone, J. J.; Hamerlynck, E. P.; Nichols, M. H.; Holifield Collins, C. D.; Scott, R. L.

    2010-12-01

    This study investigates how drought-induced change in semiarid grassland community affected runoff and sediment yield in a small watershed in southeast Arizona, USA. Three distinct periods in ecosystem composition and associated runoff and sediment yield were identified according to dominant species: native bunchgrass (1974-2005), forbs (2006), and the invasive grass, Eragrostis lehmanniana (2007-2009). Precipitation, runoff, and sediment yield for each period were analyzed and compared at watershed and plot scales. Average watershed annual sediment yield was 0.16 t ha-1 yr-1. Despite similarities in precipitation characteristics, decline in plant canopy cover during the transition period of 2006 caused watershed sediment yield to increase 23-fold to 1.64 t ha-1 yr-1 comparing with preceding period under native bunchgrasses (0.06 t ha-1 yr-1) or succeeding period under E. lehmanniana (0.06 t ha-1 yr-1). In contrast, measurements on small runoff plots on the hillslopes of the same watershed showed a significant increase in sediment discharge that continued after E. lehmanniana replaced native grasses. Together, these findings suggest alteration in plant community increased sediment yield but that hydrological responses to this event differ at watershed and plot scales, highlighting the geomorphological controls at the watershed scale that determine sediment transport efficiency and storage. Resolving these scalar issues will help identify critical landform features needed to preserve watershed integrity under changing climate conditions.

  17. Noninvasive Measurement of Vulnerability to Drought-Induced Embolism by X-Ray Microtomography.

    PubMed

    Choat, Brendan; Badel, Eric; Burlett, Regis; Delzon, Sylvain; Cochard, Herve; Jansen, Steven

    2016-01-01

    Hydraulic failure induced by xylem embolism is one of the primary mechanisms of plant dieback during drought. However, many of the methods used to evaluate the vulnerability of different species to drought-induced embolism are indirect and invasive, increasing the possibility that measurement artifacts may occur. Here, we utilize x-ray computed microtomography (microCT) to directly visualize embolism formation in the xylem of living, intact plants with contrasting wood anatomy (Quercus robur, Populus tremula × Populus alba, and Pinus pinaster). These observations were compared with widely used centrifuge techniques that require destructive sampling. MicroCT imaging provided detailed spatial information regarding the dimensions and functional status of xylem conduits during dehydration. Vulnerability curves based on microCT observations of intact plants closely matched curves based on the centrifuge technique for species with short vessels (P. tremula × P. alba) or tracheids (P. pinaster). For ring porous Q. robur, the centrifuge technique significantly overestimated vulnerability to embolism, indicating that caution should be used when applying this technique to species with long vessels. These findings confirm that microCT can be used to assess the vulnerability to embolism on intact plants by direct visualization. PMID:26527655

  18. Experimental evidence for drought induced alternative stable states of soil moisture.

    PubMed

    Robinson, David A; Jones, Scott B; Lebron, Inma; Reinsch, Sabine; Domínguez, María T; Smith, Andrew R; Jones, Davey L; Marshall, Miles R; Emmett, Bridget A

    2016-01-01

    Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction. PMID:26804897

  19. Experimental evidence for drought induced alternative stable states of soil moisture

    NASA Astrophysics Data System (ADS)

    Robinson, David. A.; Jones, Scott B.; Lebron, Inma; Reinsch, Sabine; Domínguez, María T.; Smith, Andrew R.; Jones, Davey L.; Marshall, Miles R.; Emmett, Bridget A.

    2016-01-01

    Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction.

  20. Experimental evidence for drought induced alternative stable states of soil moisture

    PubMed Central

    Robinson, David. A.; Jones, Scott B.; Lebron, Inma; Reinsch, Sabine; Domínguez, María T.; Smith, Andrew R.; Jones, Davey L.; Marshall, Miles R.; Emmett, Bridget A.

    2016-01-01

    Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction. PMID:26804897

  1. Epigenetics of drought-induced trans-generational plasticity: consequences for range limit development.

    PubMed

    Alsdurf, Jacob; Anderson, Cynthia; Siemens, David H

    2015-01-01

    Genetic variation gives plants the potential to adapt to stressful environments that often exist beyond their geographic range limits. However, various genetic, physiological or developmental constraints might prevent the process of adaptation. Alternatively, environmentally induced epigenetic changes might sustain populations for several generations in stressful areas across range boundaries, but previous work on Boechera stricta, an upland mustard closely related to Arabidopsis, documented a drought-induced trans-generational plastic trade-off that could contribute to range limit development. Offspring of parents who were drought treated had higher drought tolerance, but lower levels of glucosinolate toxins. Both drought tolerance and defence are thought to be needed to expand the range to lower elevations. Here, we used methylation-sensitive amplified fragment length polymorphisms to determine whether environmentally induced DNA methylation and thus epigenetics could be a mechanism involved in the observed trans-generational plastic trade-off. We compared 110 offspring from the same self-fertilizing lineages whose parents were exposed to experimental drought stress treatments in the laboratory. Using three primer combinations, 643 polymorphic epi-loci were detected. Discriminant function analysis (DFA) on the amount of methylation detected resulted in significant combinations of epi-loci that distinguished the parent drought treatments in the offspring. Principal component (PC) and univariate association analyses also detected the significant differences, even after controlling for lineage, planting flat, developmental differences and multiple testing. Univariate tests also indicated significant associations between the amount of methylation and drought tolerance or glucosinolate toxin concentration. One epi-locus that was implicated in DFA, PC and univariate association analysis may be directly involved in the trade-off because increased methylation at this

  2. Epigenetics of drought-induced trans-generational plasticity: consequences for range limit development

    PubMed Central

    Alsdurf, Jacob; Anderson, Cynthia; Siemens, David H.

    2016-01-01

    Genetic variation gives plants the potential to adapt to stressful environments that often exist beyond their geographic range limits. However, various genetic, physiological or developmental constraints might prevent the process of adaptation. Alternatively, environmentally induced epigenetic changes might sustain populations for several generations in stressful areas across range boundaries, but previous work on Boechera stricta, an upland mustard closely related to Arabidopsis, documented a drought-induced trans-generational plastic trade-off that could contribute to range limit development. Offspring of parents who were drought treated had higher drought tolerance, but lower levels of glucosinolate toxins. Both drought tolerance and defence are thought to be needed to expand the range to lower elevations. Here, we used methylation-sensitive amplified fragment length polymorphisms to determine whether environmentally induced DNA methylation and thus epigenetics could be a mechanism involved in the observed trans-generational plastic trade-off. We compared 110 offspring from the same self-fertilizing lineages whose parents were exposed to experimental drought stress treatments in the laboratory. Using three primer combinations, 643 polymorphic epi-loci were detected. Discriminant function analysis (DFA) on the amount of methylation detected resulted in significant combinations of epi-loci that distinguished the parent drought treatments in the offspring. Principal component (PC) and univariate association analyses also detected the significant differences, even after controlling for lineage, planting flat, developmental differences and multiple testing. Univariate tests also indicated significant associations between the amount of methylation and drought tolerance or glucosinolate toxin concentration. One epi-locus that was implicated in DFA, PC and univariate association analysis may be directly involved in the trade-off because increased methylation at this

  3. Changes in soil bacterial community triggered by drought-induced gap succession preceded changes in soil C stocks and quality.

    PubMed

    Yuste, Jorge Curiel; Barba, Josep; Fernandez-Gonzalez, Antonio José; Fernandez-Lopez, Manuel; Mattana, Stefania; Martinez-Vilalta, Jordi; Nolis, Pau; Lloret, Francisco

    2012-12-01

    The aim of this study was to understand how drought-induced tree mortality and subsequent secondary succession would affect soil bacterial taxonomic composition as well as soil organic matter (SOM) quantity and quality in a mixed Mediterranean forest where the Scots pine (Pinus sylvestris) population, affected by climatic drought-induced die-off, is being replaced by Holm-oaks (HO; Quercus ilex). We apply a high throughput DNA pyrosequencing technique and (13)C solid-state Nuclear Magnetic Resonance (CP-MAS (13)C NMR) to soils within areas of influence (defined as an surface with 2-m radius around the trunk) of different trees: healthy and affected (defoliated) pines, pines that died a decade ago and healthy HOs. Soil respiration was also measured in the same spots during a spring campaign using a static close-chamber method (soda lime). A decade after death, and before aerial colonization by the more competitive HOs have even taken place, we could not find changes in soil C pools (quantity and/or quality) associated with tree mortality and secondary succession. Unlike C pools, bacterial diversity and community structure were strongly determined by tree mortality. Convergence between the most abundant taxa of soil bacterial communities under dead pines and colonizer trees (HOs) further suggests that physical gap colonization was occurring below-ground before above-ground colonization was taken place. Significantly higher soil respiration rates under dead trees, together with higher bacterial diversity and anomalously high representation of bacteria commonly associated with copiotrophic environments (r-strategic bacteria) further gives indications of how drought-induced tree mortality and secondary succession were influencing the structure of microbial communities and the metabolic activity of soils. PMID:23301169

  4. Changes in soil bacterial community triggered by drought-induced gap succession preceded changes in soil C stocks and quality

    PubMed Central

    Yuste, Jorge Curiel; Barba, Josep; Fernandez-Gonzalez, Antonio José; Fernandez-Lopez, Manuel; Mattana, Stefania; Martinez-Vilalta, Jordi; Nolis, Pau; Lloret, Francisco

    2012-01-01

    The aim of this study was to understand how drought-induced tree mortality and subsequent secondary succession would affect soil bacterial taxonomic composition as well as soil organic matter (SOM) quantity and quality in a mixed Mediterranean forest where the Scots pine (Pinus sylvestris) population, affected by climatic drought-induced die-off, is being replaced by Holm-oaks (HO; Quercus ilex). We apply a high throughput DNA pyrosequencing technique and 13C solid-state Nuclear Magnetic Resonance (CP-MAS 13C NMR) to soils within areas of influence (defined as an surface with 2-m radius around the trunk) of different trees: healthy and affected (defoliated) pines, pines that died a decade ago and healthy HOs. Soil respiration was also measured in the same spots during a spring campaign using a static close-chamber method (soda lime). A decade after death, and before aerial colonization by the more competitive HOs have even taken place, we could not find changes in soil C pools (quantity and/or quality) associated with tree mortality and secondary succession. Unlike C pools, bacterial diversity and community structure were strongly determined by tree mortality. Convergence between the most abundant taxa of soil bacterial communities under dead pines and colonizer trees (HOs) further suggests that physical gap colonization was occurring below-ground before above-ground colonization was taken place. Significantly higher soil respiration rates under dead trees, together with higher bacterial diversity and anomalously high representation of bacteria commonly associated with copiotrophic environments (r-strategic bacteria) further gives indications of how drought-induced tree mortality and secondary succession were influencing the structure of microbial communities and the metabolic activity of soils. PMID:23301169

  5. The dynamics of carbon stored in xylem sapwood to drought-induced hydraulic stress in mature trees

    PubMed Central

    Yoshimura, Kenichi; Saiki, Shin-Taro; Yazaki, Kenichi; Ogasa, Mayumi Y.; Shirai, Makoto; Nakano, Takashi; Yoshimura, Jin; Ishida, Atsushi

    2016-01-01

    Climate-induced forest die-off is widespread in multiple biomes, strongly affecting the species composition, function and primary production in forest ecosystems. Hydraulic failure and carbon starvation in xylem sapwood are major hypotheses to explain drought-induced tree mortality. Because it is difficult to obtain enough field observations on drought-induced mortality in adult trees, the current understanding of the physiological mechanisms for tree die-offs is still controversial. However, the simultaneous examination of water and carbon uses throughout dehydration and rehydration processes in adult trees will contribute to clarify the roles of hydraulic failure and carbon starvation in tree wilting. Here we show the processes of the percent loss of hydraulic conductivity (PLC) and the content of nonstructural carbohydrates (NSCs) of distal branches in woody plants with contrasting water use strategy. Starch was converted to soluble sugar during PLC progression under drought, and the hydraulic conductivity recovered following water supply. The conversion of NSCs is strongly associated with PLC variations during dehydration and rehydration processes, indicating that stored carbon contributes to tree survival under drought; further carbon starvation can advance hydraulic failure. We predict that even slow-progressing drought degrades forest ecosystems via carbon starvation, causing more frequent catastrophic forest die-offs than the present projection. PMID:27079677

  6. The dynamics of carbon stored in xylem sapwood to drought-induced hydraulic stress in mature trees.

    PubMed

    Yoshimura, Kenichi; Saiki, Shin-Taro; Yazaki, Kenichi; Ogasa, Mayumi Y; Shirai, Makoto; Nakano, Takashi; Yoshimura, Jin; Ishida, Atsushi

    2016-01-01

    Climate-induced forest die-off is widespread in multiple biomes, strongly affecting the species composition, function and primary production in forest ecosystems. Hydraulic failure and carbon starvation in xylem sapwood are major hypotheses to explain drought-induced tree mortality. Because it is difficult to obtain enough field observations on drought-induced mortality in adult trees, the current understanding of the physiological mechanisms for tree die-offs is still controversial. However, the simultaneous examination of water and carbon uses throughout dehydration and rehydration processes in adult trees will contribute to clarify the roles of hydraulic failure and carbon starvation in tree wilting. Here we show the processes of the percent loss of hydraulic conductivity (PLC) and the content of nonstructural carbohydrates (NSCs) of distal branches in woody plants with contrasting water use strategy. Starch was converted to soluble sugar during PLC progression under drought, and the hydraulic conductivity recovered following water supply. The conversion of NSCs is strongly associated with PLC variations during dehydration and rehydration processes, indicating that stored carbon contributes to tree survival under drought; further carbon starvation can advance hydraulic failure. We predict that even slow-progressing drought degrades forest ecosystems via carbon starvation, causing more frequent catastrophic forest die-offs than the present projection. PMID:27079677

  7. Knockdown of WHIRLY1 Affects Drought Stress-Induced Leaf Senescence and Histone Modifications of the Senescence-Associated Gene HvS40.

    PubMed

    Janack, Bianka; Sosoi, Paula; Krupinska, Karin; Humbeck, Klaus

    2016-01-01

    The plastid-nucleus located protein WHIRLY1 has been described as an upstream regulator of leaf senescence, binding to the promoter of senescence-associated genes like HvS40. To investigate the impact of WHIRLY1 on drought stress-induced, premature senescence, transgenic barley plants with an RNAi-mediated knockdown of the HvWHIRLY1 gene were grown under normal and drought stress conditions. The course of leaf senescence in these lines was monitored by physiological parameters and studies on the expression of senescence- and drought stress-related genes. Drought treatment accelerated leaf senescence in WT plants, whereas WHIRLY 1 knockdown lines (RNAi-W1) showed a stay-green phenotype. Expression of both senescence-associated and drought stress-responsive genes, was delayed in the transgenic plants. Notably, expression of transcription factors of the WRKY and NAC families, which are known to function in senescence- and stress-related signaling pathways, was affected in plants with impaired accumulation of WHIRLY1, indicating that WHIRLY1 acts as an upstream regulator of drought stress-induced senescence. To reveal the epigenetic indexing of HvS40 at the onset of drought-induced senescence in WT and RNAi-W1 lines, stress-responsive loading with histone modifications of promoter and coding sequences of HvS40 was analyzed by chromatin immunoprecipitation and quantified by qRT-PCR. In the wildtype, the euchromatic mark H3K9ac of the HvS40 gene was low under control conditions and was established in response to drought treatment, indicating the action of epigenetic mechanisms in response to drought stress. However, drought stress caused no significant increase in H3K9ac in plants impaired in accumulation of WHIRLY1. The results show that WHIRLY1 knockdown sets in motion a delay in senescence that involves all aspects of gene expression, including changes in chromatin structure. PMID:27608048

  8. Soil respiration shifts as drought-induced tree substitution advances from Scots pine to Holm oak forest

    NASA Astrophysics Data System (ADS)

    Barba, Josep; Curiel Yuste, Jorge; Poyatos, Rafael; Janssens, Ivan A.; Lloret, Francisco

    2014-05-01

    There is more and more evidences that the current global warming trend and the increase of frequency and intensity of drought events during the last decades in the Northern hemisphere are currently producing an increment of drought-induced forest die-off events, being the Mediterranean region one of the most affected areas. This drought-induced mortality could lead in a vegetation shift with unpredicted consequences in carbon pools, where soils are the most determinant factor in this carbon balance as they contain over two-thirds of carbon on forest ecosystems. There are several uncertainties related on the interaction between soil, environmental conditions and vegetation shifts that could modify their capability to be net carbon sinks or sources in a warming context. We studied soil respiration and its heterotrophic (RH) and autotrophic (Ra) (split in fine roots [Rr] and mycorrhizal respiration [Rs]) components in a mixed Mediterranean forest where Scots pine (Pinus sylvestris L.) are suffering from drought-induced die-off and replaced by Holm oak (Quercus ilex L.) as the dominant tree species. Soil respiration fluxes and its fractions were measured every two weeks during one year at four stages of the substitution process (non defoliated pines [NDP], defoliated pines [DFP], dead pines [DP] and Holm oak [HO]), using the mesh exclusion method. The aims were (i) to describe soil respiration fluxes in a drought-induced secondary successional process, (ii) to test whether the changes in vegetation affected soil respiration fluxes and (iii) to determine the influence of environmental and abiotic variables on the different soil respiration fractions. Total soil respiration was 10.10±6.17 TC ha-1 y-1, RH represented the 67% of the total, Ra represented the 34% of the total, and Rr and Rs were the 22 and 12%, respectively. Significant differences were found in total soil respiration and RH between NDP and HO, being lower in HO than in NDP (34% in total and 48% in RH). No

  9. Global change-type drought-induced tree mortality: vapor pressure deficit is more important than temperature per se in causing decline in tree health.

    PubMed

    Eamus, Derek; Boulain, Nicolas; Cleverly, James; Breshears, David D

    2013-08-01

    Drought-induced tree mortality is occurring across all forested continents and is expected to increase worldwide during the coming century. Regional-scale forest die-off influences terrestrial albedo, carbon and water budgets, and land-surface energy partitioning. Although increased temperatures during drought are widely identified as a critical contributor to exacerbated tree mortality associated with "global-change-type drought", corresponding changes in vapor pressure deficit (D) have rarely been considered explicitly and have not been disaggregated from that of temperature per se. Here, we apply a detailed mechanistic soil-plant-atmosphere model to examine the impacts of drought, increased air temperature (+2°C or +5°C), and increased vapor pressure deficit (D; +1 kPa or +2.5 kPa), singly and in combination, on net primary productivity (NPP) and transpiration and forest responses, especially soil moisture content, leaf water potential, and stomatal conductance. We show that increased D exerts a larger detrimental effect on transpiration and NPP, than increased temperature alone, with or without the imposition of a 3-month drought. Combined with drought, the effect of increased D on NPP was substantially larger than that of drought plus increased temperature. Thus, the number of days when NPP was zero across the 2-year simulation was 13 or 14 days in the control and increased temperature scenarios, but increased to approximately 200 days when D was increased. Drought alone increased the number of days of zero NPP to 88, but drought plus increased temperature did not increase the number of days. In contrast, drought and increased D resulted in the number of days when NPP = 0 increasing to 235 (+1 kPa) or 304 days (+2.5 kPa). We conclude that correct identification of the causes of global change-type mortality events requires explicit consideration of the influence of D as well as its interaction with drought and temperature. This study disaggregates

  10. Involvement of CDSP 32, a drought-induced thioredoxin, in the response to oxidative stress in potato plants.

    PubMed

    Broin, M; Cuiné, S; Peltier, G; Rey, P

    2000-02-11

    In animal cells, yeast and bacteria, thioredoxins are known to participate in the response to oxidative stress. We recently identified a novel type of plant thioredoxin named CDSP 32 for chloroplastic drought-induced stress protein of 32 kDa. In the present work, we measured comparable increases in the glutathione oxidation ratio and in the level of chlorophyll thermoluminescence, a specific marker for thylakoid lipid peroxidation in Solanum tuberosum plants subjected to drought or oxidative treatments (photooxidative stress, gamma irradiation and methyl viologen spraying). Further, substantial accumulations of CDSP 32 mRNA and protein were revealed upon oxidative treatments. These data show for the first time in plants the induction of a thioredoxin by oxidative stress. We conclude that CDSP 32 may preserve chloroplastic structures against oxidative injury upon drought. PMID:10675547

  11. Drought-induced changes in flow regimes lead to long-term losses in mussel-provided ecosystem services.

    PubMed

    Vaughn, Caryn C; Atkinson, Carla L; Julian, Jason P

    2015-03-01

    Extreme hydro-meteorological events such as droughts are becoming more frequent, intense, and persistent. This is particularly true in the south central USA, where rapidly growing urban areas are running out of water and human-engineered water storage and management are leading to broad-scale changes in flow regimes. The Kiamichi River in southeastern Oklahoma, USA, has high fish and freshwater mussel biodiversity. However, water from this rural river is desired by multiple urban areas and other entities. Freshwater mussels are large, long-lived filter feeders that provide important ecosystem services. We ask how observed changes in mussel biomass and community composition resulting from drought-induced changes in flow regimes might lead to changes in river ecosystem services. We sampled mussel communities in this river over a 20-year period that included two severe droughts. We then used laboratory-derived physiological rates and river-wide estimates of species-specific mussel biomass to estimate three aggregate ecosystem services provided by mussels over this time period: biofiltration, nutrient recycling (nitrogen and phosphorus), and nutrient storage (nitrogen, phosphorus, and carbon). Mussel populations declined over 60%, and declines were directly linked to drought-induced changes in flow regimes. All ecosystem services declined over time and mirrored biomass losses. Mussel declines were exacerbated by human water management, which has increased the magnitude and frequency of hydrologic drought in downstream reaches of the river. Freshwater mussels are globally imperiled and declining around the world. Summed across multiple streams and rivers, mussel losses similar to those we document here could have considerable consequences for downstream water quality although lost biofiltration and nutrient retention. While we cannot control the frequency and severity of climatological droughts, water releases from reservoirs could be used to augment stream flows and

  12. Drought-induced changes in flow regimes lead to long-term losses in mussel-provided ecosystem services

    PubMed Central

    Vaughn, Caryn C; Atkinson, Carla L; Julian, Jason P

    2015-01-01

    Extreme hydro-meteorological events such as droughts are becoming more frequent, intense, and persistent. This is particularly true in the south central USA, where rapidly growing urban areas are running out of water and human-engineered water storage and management are leading to broad-scale changes in flow regimes. The Kiamichi River in southeastern Oklahoma, USA, has high fish and freshwater mussel biodiversity. However, water from this rural river is desired by multiple urban areas and other entities. Freshwater mussels are large, long-lived filter feeders that provide important ecosystem services. We ask how observed changes in mussel biomass and community composition resulting from drought-induced changes in flow regimes might lead to changes in river ecosystem services. We sampled mussel communities in this river over a 20-year period that included two severe droughts. We then used laboratory-derived physiological rates and river-wide estimates of species-specific mussel biomass to estimate three aggregate ecosystem services provided by mussels over this time period: biofiltration, nutrient recycling (nitrogen and phosphorus), and nutrient storage (nitrogen, phosphorus, and carbon). Mussel populations declined over 60%, and declines were directly linked to drought-induced changes in flow regimes. All ecosystem services declined over time and mirrored biomass losses. Mussel declines were exacerbated by human water management, which has increased the magnitude and frequency of hydrologic drought in downstream reaches of the river. Freshwater mussels are globally imperiled and declining around the world. Summed across multiple streams and rivers, mussel losses similar to those we document here could have considerable consequences for downstream water quality although lost biofiltration and nutrient retention. While we cannot control the frequency and severity of climatological droughts, water releases from reservoirs could be used to augment stream flows and

  13. Soil degradation in farmlands of California's San Joaquin Valley resulting from drought-induced land-use changes

    NASA Astrophysics Data System (ADS)

    Scudiero, Elia; Skaggs, Todd; Anderson, Ray; Corwin, Dennis

    2016-04-01

    Irrigation in California's Central Valley (USA) has decreased significantly due to water shortages resulting from the current drought, which began in 2010. In particular, fallow fields in the west side of the San Joaquin Valley (WSJV), which is the southwest portion of the Central Valley, increased from around 12% in the years before the drought (2007-2010) to 20-25% in the following years (2011-2015). We monitored and mapped drought-induced edaphic changes in salinity at two scales: (i) field scale (32.4-ha field in Kings County) and (ii) water district scale (2400 ha at -former- Broadview Water District in Fresno County). At both scales drought-induced land-use changes (i.e., shift from irrigated agriculture to fallow) drastically decreased soil quality by increasing salinity (and sodicity), especially in the root-zone (top 1.2 m). The field study monitors the spatial (three dimensions) changes of soil salinity (and sodicity) in the root-zone during 10 years of irrigation with drainage water followed by 4 years of no applied irrigation water (only rainfall) due to drought conditions. Changes of salinity (and other edaphic properties), through the soil profile (down to 1.2 m, at 0.3-m increments), were monitored and modeled using geospatial apparent electrical conductivity measurements and extensive soil sampling in 1999, 2002, 2004, 2009, 2011, and 2013. Results indicate that when irrigation was applied, salts were leached from the root-zone causing a remarkable improvement in soil quality. However, in less than two years after termination of irrigation, salinity in the soil profile returned to original levels or higher across the field. At larger spatial scales the effect of drought-induced land-use change on root-zone salinity is also evident. Up to spring 2006, lands in Broadview Water District (BWD) were used for irrigated agriculture. Water rights were then sold and the farmland was retired. Soil quality decreased since land retirement, especially during the

  14. Drought-induced stomatal closure probably cannot explain divergent white spruce growth in the Brooks Range, Alaska, USA.

    PubMed

    Brownlee, Annalis H; Sullivan, Patrick F; Csank, Adam Z; Sveinbjörnsson, Bjartmar; Ellison, Sarah B Z

    2016-01-01

    Increment cores from the boreal forest have long been used to reconstruct past climates. However, in recent years, numerous studies have revealed a deterioration of the correlation between temperature and tree growth that is commonly referred to as divergence. In the Brooks Range of northern Alaska, USA, studies of white spruce (Picea glauca) revealed that trees in the west generally showed positive growth trends, while trees in the central and eastern Brooks Range showed mixed and negative trends during late 20th century warming. The growing season climate of the eastern Brooks Range is thought to be drier than the west. On this basis, divergent tree growth in the eastern Brooks Range has been attributed to drought stress. To investigate the hypothesis that drought-induced stomatal closure can explain divergence in the Brooks Range, we synthesized all of the Brooks Range white spruce data available in the International Tree Ring Data Bank (ITRDB) and collected increment cores from our primary sites in each of four watersheds along a west-to-east gradient near the Arctic treeline. For cores from our sites, we measured ring widths and calculated carbon isotope discrimination (δ13C), intrinsic water-use efficiency (iWUE), and needle intercellular CO2 concentration (C(i)) from δ13C in tree-ring alpha-cellulose. We hypothesized that trees exhibiting divergence would show a corresponding decline in δ13C, a decline in C(i), and a strong increase in iWUE. Consistent with the ITRDB data, trees at our western and central sites generally showed an increase in the strength of the temperature-growth correlation during late 20th century warming, while trees at our eastern site showed strong divergence. Divergent tree growth was not, however, associated with declining δ13C. Meanwhile, estimates of C(i) showed a strong increase at all of our study sites, indicating that more substrate was available for photosynthesis in the early 21st than in the early 20th century. Our

  15. Linking carbon and water relations to drought-induced mortality in Pinus flexilis seedlings.

    PubMed

    Reinhardt, Keith; Germino, Matthew J; Kueppers, Lara M; Domec, Jean-Christophe; Mitton, Jeffry

    2015-07-01

    Survival of tree seedlings at high elevations has been shown to be limited by thermal constraints on carbon balance, but it is unknown if carbon relations also limit seedling survival at lower elevations, where water relations may be more important. We measured and modeled carbon fluxes and water relations in first-year Pinus flexilis seedlings in garden plots just beyond the warm edge of their natural range, and compared these with dry-mass gain and survival across two summers. We hypothesized that mortality in these seedlings would be associated with declines in water relations, more so than with carbon-balance limitations. Rather than gradual declines in survivorship across growing seasons, we observed sharp, large-scale mortality episodes that occurred once volumetric soil-moisture content dropped below 10%. By this point, seedling water potentials had decreased below -5 MPa, seedling hydraulic conductivity had decreased by 90% and seedling hydraulic resistance had increased by >900%. Additionally, non-structural carbohydrates accumulated in aboveground tissues at the end of both summers, suggesting impairments in phloem-transport from needles to roots. This resulted in low carbohydrate concentrations in roots, which likely impaired root growth and water uptake at the time of critically low soil moisture. While photosynthesis and respiration on a leaf area basis remained high until critical hydraulic thresholds were exceeded, modeled seedling gross primary productivity declined steadily throughout the summers. At the time of mortality, modeled productivity was insufficient to support seedling biomass-gain rates, metabolism and secondary costs. Thus the large-scale mortality events that we observed near the end of each summer were most directly linked with acute, episodic declines in plant hydraulic function that were linked with important changes in whole-seedling carbon relations. PMID:26116925

  16. [Nucleotide polymorphism in the drought induced transcription factor CBF4 region of Arabidopsis thaliana and its molecular evolution analyses].

    PubMed

    Hao, Gang-Ping; Wu, Zhong-Yi; Cao, Ming-Qing; Pelletier, Georges; Brunel, Dominique; Huang, Cong-Lin; Yang, Qing

    2004-12-01

    Intraspecific nucleotide polymorphism in the drought induced transcription factor CBF4 region of Arabidopsis thaliana was analyzed with 17 core accessions growing in different ecoclimate. High density of single nucleotide polymorphism (SNP) and insertion/deletion (Indel) were found, on average 1 SNP per 35.8 bp and 1 Indel per 143 bp. Nucleotide polymorphism in non-coding region was three times higher than that in coding region. In coding region of CBF4, SNP frequency is one SNP per 96.4 bp, one nonsynonymous mutation was detected from 25 av, 203 av and 244 av accessions, which is the 205th site amino acid variation: gly <--> val caused by the 1034th site (corresponding to 19,696 site nucleotide of GenBank No. AB015478 as 1) nucleotide variation: G <--> T. Statistical result of nucleotide diversity showed that linkage disequilibrium (LD) existed in large-scale region of CBF4 and recombination event was also detected in 5' non-coding region. Identical to the results of other genes of Arabidopsis, different regions of the gene were seemingly under different selective pressures. Balancing selection resulted in high nucleotide diversity in 3' non-coding region, and the neutral mutation hypothesis can explain the DNA polymorphism in coding region, whereas, nature positive selection in the population affected nucleotide variation in 5' non-coding region of gene. PMID:15633649

  17. Drought-induced sulphate release from a wetland in south-central Ontario.

    PubMed

    Eimers, M Catherine; Watmough, Shaun A; Buttle, James M; Dillon, Peter J

    2007-04-01

    Increased sulphate (SO(4)) export from wetlands following summer droughts in central Ontario, Canada has been associated with the delayed chemical recovery of downstream surface waters following decreased sulphur (S) emissions. Prolonged summer droughts result in a decrease or cessation of stream flow, declines in wetland water table level and oxidation of reduced S compounds to SO(4), which is subsequently flushed into drainage streams when stream flow resumes. Sulphate input-output budget calculations (1983-1995 and 1999-2001) at a conifer Sphagnum swamp in the Plastic Lake catchment, indicate that SO(4) is retained in most years but is exported on a net basis following particularly severe summer droughts that result in the cessation of stream flow for more than 54 days (95% CI: 41-72 days). Hindcast calculations using long-term (1916-2000) stream discharge records from a nearby station indicate that while droughts occurred frequently in south-central Ontario over the past 85 years, sufficiently dry conditions to cause net SO(4) export occurred in only 18 of the past 85 years, and indicate a cumulative positive SO(4) balance for the swamp (i.e. net SO(4) retention). Furthermore, the S pool at the Plastic Lake swamp has been estimated to be approximately 1500 kg S/ha in the upper 40 cm peat layer, which is large compared to the amount of net SO(4) export that occurs even in years with particularly dry summers (e.g. -43 kg S/ha in 1987/88). Together, these data suggest that the wetland S pool at Plastic Lake has not been depleted by previous droughts and will continue to sustain episodic drought-related SO(4) export for the foreseeable future. PMID:16957853

  18. Drought-induced enrichment of soil nitrogen leads to record high nitrate loading to agricultural river networks (Invited)

    NASA Astrophysics Data System (ADS)

    Burgin, A. J.; Loecke, T. D.; Davis, C.; Ward, A. S.; St. Clair, M.; Riveros-Iregui, D.; Thomas, S. A.

    2013-12-01

    Nitrogen (N) fertilization is a cornerstone of modern agriculture, but the practice also leads to eutrophication, hypoxia, and harmful algal blooms in both inland and coastal waters. Several studies identify Iowa, Illinois and Indiana as major source areas of N discharged by the Mississippi River to the Gulf of Mexico where large-scale hypoxia develops annually. Continental-scale management of nitrogen requires a comprehensive understanding of watershed-specific hydrologic dynamics and their consequences for nitrate flushing from agricultural landscapes, as well as quantification of fertilizer export in relation to interannual climate variability. This study addresses the following questions: (1) How do climate and precipitation patterns control the magnitude and timing of nitrate flushing from agricultural landscapes; and (2) How does the stream nitrate pulse change in relation to position within the stream network? We instrumented five streams of varying order (1st to 4th) and watershed size (5 ha to 3240000 ha) with real-time nitrate sensors. We combined this information with 15 existing USGS stations, located throughout the Iowa-Cedar River basin (Iowa, USA). We then coupled 15-min nitrate measurements at selected streams with seasonal (May, July, September) synoptic sampling at 100+ locations through the basin. We demonstrate that drought-induced accumulation of soil N over winter (2012), followed by an unseasonably cool, wet spring (2013) sent record levels of stream N into the Mississippi River. Our results show extreme variations in nitrate concentrations and flux associated with pronounced wet/dry cycles, and rapid shifts in hydrologic connectivity within the same year. Information connecting storm events, antecedent environmental conditions and nutrient dynamics is critical for improving our predictions of nitrate loading to riverine networks under increased climatic variation. Furthermore, our findings clearly demonstrate that understanding and

  19. Use of NAP gene to manipulate leaf senescence in plants

    DOEpatents

    Gan, Susheng; Guo, Yongfeng

    2013-04-16

    The present invention discloses transgenic plants having an altered level of NAP protein compared to that of a non-transgenic plant, where the transgenic plants display an altered leaf senescence phenotype relative to a non-transgenic plant, as well as mutant plants comprising an inactivated NAP gene, where mutant plants display a delayed leaf senescence phenotype compared to that of a non-mutant plant. The present invention also discloses methods for delaying leaf senescence in a plant, as well as methods of making a mutant plant having a decreased level of NAP protein compared to that of a non-mutant plant, where the mutant plant displays a delayed leaf senescence phenotype relative to a non-mutant plant. Methods for causing precocious leaf senescence or promoting leaf senescence in a plant are also disclosed. Also disclosed are methods of identifying a candidate plant suitable for breeding that displays a delayed leaf senescence and/or enhanced yield phenotype.

  20. Nonstructural leaf carbohydrates dynamics of Pinus edulis during drought-induced tree mortality reveal role for carbon metabolism in mortality mechanism

    USGS Publications Warehouse

    Adams, Henry D.; Germino, Matthew J.; Breshears, David D.; Barron-Gafford, Greg A.; Guardiola-Claramonte, Maite; Zou, Chris B.; Huxman, Travis E.

    2013-01-01

    * Reduced foliar NSC during lethal drought indicates a carbon metabolism role in mortality mechanism. Although carbohydrates were not completely exhausted at mortality, temperature differences in starch accumulation timing suggest that carbon metabolism changes are associated with time to death. Drought mortality appears to be related to temperature-dependent carbon dynamics concurrent with increasing hydraulic stress in P. edulis and potentially other similar species.

  1. Evidence That Drought-Induced Stomatal Closure Is Not an Important Constraint on White Spruce Performance Near the Arctic Treeline in Alaska

    NASA Astrophysics Data System (ADS)

    Sullivan, P.; Brownlee, A.; Ellison, S.; Sveinbjornsson, B.

    2014-12-01

    Tree cores collected from trees growing at high latitudes have long been used to reconstruct past climates, because of close positive correlations between temperature and tree growth. However, in recent decades and at many sites, these relationships have deteriorated and have even become negative in some instances. The observation of declining tree growth in response to rising temperature has prompted many investigators to suggest that high latitude trees may be increasingly exhibiting drought-induced stomatal closure. In the Brooks Range of northern Alaska, the observation of low and declining growth of white spruce is more prevalent in the central and eastern parts of the range, where precipitation is lower, providing superficial support for the drought stress hypothesis. In this study, we investigated the occurrence of white spruce drought-induced stomatal closure in four watersheds along a west to east gradient near the Arctic treeline in the Brooks Range. We obtained a historical perspective on tree growth and water relations by collecting increment cores for analysis of ring widths and carbon isotopes in tree-ring alpha-cellulose. Meanwhile, we made detailed assessments of contemporary water relations at the scales of the whole canopy and the needle. All of our data indicate that drought-induced stomatal closure is probably not responsible for low and declining growth in the central and eastern Brooks Range. Carbon isotope discrimination has generally increased over the past century and our calculations indicate that needle inter-cellular CO2 concentration is much greater now than it was in the early 1900's. Measurements of needle gas exchange are consistent with the tree core record, in the sense that instances of low photosynthesis at our sites are not coincident with similarly low stomatal conductance and low inter-cellular CO2 concentration. Finally, hourly measurements of xylem sap flow indicate that trees at our study sites are able to maintain near

  2. Drought induced changes of plant belowground carbon allocation affect soil microbial community function in a subalpine meadow

    NASA Astrophysics Data System (ADS)

    Fuchslueger, L.; Bahn, M.; Fritz, K.; Hasibeder, R.; Richter, A.

    2012-12-01

    There is growing evidence that climate extremes may affect ecosystem carbon dynamics more strongly than gradual changes in temperatures or precipitation. Climate projections suggest more frequent heat waves accompanied by extreme drought periods in many parts of Europe, including the Alps. Drought is considered to decrease plant C uptake and turnover, which may in turn decrease belowground C allocation and potentially has significant consequences for microbial community composition and functioning. However, information on effects of drought on C dynamics at the plant-soil interface in real ecosystems is still scarce. Our study aimed at understanding how summer drought affects soil microbial community composition and the uptake of recently assimilated plant C by different microbial groups in grassland. We hypothesized that under drought 1) the microbial community shifts, fungi being less affected than bacteria, 2) plants decrease belowground C allocation, which further reduces C transfer to soil microbes and 3) the combined effects of belowground C allocation, reduced soil C transport due to reduced soil moisture and shift in microbial communities cause an accumulation of extractable organic C in the soil. Our study was conducted as part of a rain-exclusion experiment in a subalpine meadow in the Austrian Central Alps. After eight weeks of rain exclusion we pulse labelled drought and control plots with 13CO2 and traced C in plant biomass, extractable organic C (EOC) and soil microbial communities using phospholipid fatty acids (PLFA). Drought induced a shift of the microbial community composition: gram-positive bacteria became more dominant, whereas gram-negative bacteria were not affected by drought. Also the relative abundance of fungal biomass was not affected by drought. While total microbial biomass (as estimated by total microbial PLFA content) increased during drought, less 13C was taken up. This reduction was pronounced for bacterial biomarkers. It reflects

  3. Wood anatomy and carbon-isotope discrimination support long-term hydraulic deterioration as a major cause of drought-induced dieback.

    PubMed

    Pellizzari, Elena; Camarero, J Julio; Gazol, Antonio; Sangüesa-Barreda, Gabriel; Carrer, Marco

    2016-06-01

    Hydraulic impairment due to xylem embolism and carbon starvation are the two proposed mechanisms explaining drought-induced forest dieback and tree death. Here, we evaluate the relative role played by these two mechanisms in the long-term by quantifying wood-anatomical traits (tracheid size and area of parenchyma rays) and estimating the intrinsic water-use efficiency (iWUE) from carbon isotopic discrimination. We selected silver fir and Scots pine stands in NE Spain with ongoing dieback processes and compared trees showing contrasting vigour (declining vs nondeclining trees). In both species earlywood tracheids in declining trees showed smaller lumen area with thicker cell wall, inducing a lower theoretical hydraulic conductivity. Parenchyma ray area was similar between the two vigour classes. Wet spring and summer conditions promoted the formation of larger lumen areas, particularly in the case of nondeclining trees. Declining silver firs presented a lower iWUE than conspecific nondeclining trees, but the reverse pattern was observed in Scots pine. The described patterns in wood anatomical traits and iWUE are coherent with a long-lasting deterioration of the hydraulic system in declining trees prior to their dieback. Retrospective quantifications of lumen area permit to forecast dieback in declining trees 2-5 decades before growth decline started. Wood anatomical traits provide a robust tool to reconstruct the long-term capacity of trees to withstand drought-induced dieback. PMID:26790660

  4. The limits of drought-induced rapid cold-hardening: extremely brief, mild desiccation triggers enhanced freeze-tolerance in Eurosta solidaginis larvae.

    PubMed

    Gantz, J D; Lee, Richard E

    2015-02-01

    Rapid cold-hardening (RCH) is a highly conserved response in insects that induces physiological changes within minutes to hours of exposure to low temperature and provides protection from chilling injury. Recently, a similar response, termed drought-induced RCH, was described following as little as 6h of desiccation, producing a loss of less than 10% of fresh mass. In this study, we investigated the limits and mechanisms of this response in larvae of the goldenrod gall fly Eurosta solidaginis (Diptera, Tephritidae). The cold-hardiness of larvae increased markedly after as few as 2h of desiccation and a loss of less than 1% fresh mass, as organismal survival increased from 8% to 41% following exposure to -18 °C. Tissue-level effects of desiccation were observed within 1h, as 87% of midgut cells from desiccated larvae remained viable following freezing compared to 57% of controls. We also demonstrated that drought-induced RCH occurs independently of neuroendocrine input, as midgut tissue desiccated ex vivo displayed improved freeze-tolerance relative to control tissue (78-11% survival, respectively). Finally, though there was an increase in hemolymph osmolality beyond the expected effects of the osmo-concentration of solutes during dehydration, we determined that this increase was not due to the synthesis of glycerol, glucose, sorbitol, or trehalose. Our results indicate that E. solidaginis larvae are extremely sensitive to desiccation, which is a triggering mechanism for one or more physiological pathways that confer enhanced freeze-tolerance. PMID:25545423

  5. Recent drought-induced mortality of aspen forests along a water-balance tipping point for ecosystems in western Canada

    NASA Astrophysics Data System (ADS)

    Hogg, E.

    2009-05-01

    stand-level productivity, dieback and mortality were governed primarily by moisture variation. Furthermore, during and following this drought there was increasing damage by wood-boring insects and elevated, regional-scale mortality of aspen over at least 6 years (2002-2008). Although it is premature to attribute these impacts to anthropogenic climate change, they provide an excellent analog for what may be expected in future, even under a modest trend toward drying over the next few decades. Furthermore, the recent aspen mortality in western Canada shares many features common to other recent episodes of drought-induced forest mortality that have been documented on all of the earth's forested continents. This suggests the need for an integrated, global research and monitoring system that would enable early detection and attribution of large-scale ecosystem changes, especially in climatically-sensitive regions along forest-grassland boundaries around the world.

  6. ABA receptor PYL9 promotes drought resistance and leaf senescence

    PubMed Central

    Zhao, Yang; Chan, Zhulong; Gao, Jinghui; Xing, Lu; Cao, Minjie; Yu, Chunmei; Hu, Yuanlei; You, Jun; Shi, Haitao; Zhu, Yingfang; Gong, Yuehua; Mu, Zixin; Wang, Haiqing; Deng, Xin; Wang, Pengcheng; Bressan, Ray A.; Zhu, Jian-Kang

    2016-01-01

    Drought stress is an important environmental factor limiting plant productivity. In this study, we screened drought-resistant transgenic plants from 65 promoter-pyrabactin resistance 1-like (PYL) abscisic acid (ABA) receptor gene combinations and discovered that pRD29A::PYL9 transgenic lines showed dramatically increased drought resistance and drought-induced leaf senescence in both Arabidopsis and rice. Previous studies suggested that ABA promotes senescence by causing ethylene production. However, we found that ABA promotes leaf senescence in an ethylene-independent manner by activating sucrose nonfermenting 1-related protein kinase 2s (SnRK2s), which subsequently phosphorylate ABA-responsive element-binding factors (ABFs) and Related to ABA-Insensitive 3/VP1 (RAV1) transcription factors. The phosphorylated ABFs and RAV1 up-regulate the expression of senescence-associated genes, partly by up-regulating the expression of Oresara 1. The pyl9 and ABA-insensitive 1-1 single mutants, pyl8-1pyl9 double mutant, and snrk2.2/3/6 triple mutant showed reduced ABA-induced leaf senescence relative to the WT, whereas pRD29A::PYL9 transgenic plants showed enhanced ABA-induced leaf senescence. We found that leaf senescence may benefit drought resistance by helping to generate an osmotic potential gradient, which is increased in pRD29A::PYL9 transgenic plants and causes water to preferentially flow to developing tissues. Our results uncover the molecular mechanism of ABA-induced leaf senescence and suggest an important role of PYL9 and leaf senescence in promoting resistance to extreme drought stress. PMID:26831097

  7. Delayed ejaculation

    MedlinePlus

    Ejaculatory incompetence; Sex - delayed ejaculation; Retarded ejaculation; Anejaculation; Infertility - delayed ejaculation ... include: Religious background that makes the person view sex as sinful Lack of attraction for a partner ...

  8. Does leaf manipulation affect leaf appearance in italian ryegrass (Lolium multiflorum Lam.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mechanical stimuli such as rubbing, shaking, or flexing plants can alter their growth rates and morphologies. Plant response to mechanical stress can result in delayed plant growth, reduced leaf size, shorten and thicken stems, and reduced yields. Repeated measurements, such as leaf counting or me...

  9. Hormonal regulation of leaf senescence in Lilium.

    PubMed

    Arrom, Laia; Munné-Bosch, Sergi

    2012-10-15

    In addition to floral senescence and longevity, the control of leaf senescence is a major factor determining the quality of several cut flowers, including Lilium, in the commercial market. To better understand the physiological process underlying leaf senescence in this species, we evaluated: (i) endogenous variation in the levels of phytohormones during leaf senescence, (ii) the effects of leaf darkening in senescence and associated changes in phytohormones, and (iii) the effects of spray applications of abscisic acid (ABA) and pyrabactin on leaf senescence. Results showed that while gibberellin 4 (GA(4)) and salicylic acid (SA) contents decreased, that of ABA increased during the progression of leaf senescence. However, dark-induced senescence increased ABA levels, but did not affect GA(4) and SA levels, which appeared to correlate more with changes in air temperature and/or photoperiod than with the induction of leaf senescence. Furthermore, spray applications of pyrabactin delayed the progression of leaf senescence in cut flowers. Thus, we conclude that (i) ABA plays a major role in the regulation of leaf senescence in Lilium, (ii) darkness promotes leaf senescence and increases ABA levels, and (iii) exogenous applications of pyrabactin inhibit leaf senescence in Lilium, therefore suggesting that it acts as an antagonist of ABA in senescing leaves of cut lily flowers. PMID:22854182

  10. 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

  11. Novel drought-inducible genes in the highly drought-tolerant cowpea: cloning of cDNAs and analysis of the expression of the corresponding genes.

    PubMed

    Iuchi, S; Yamaguchi-Shinozaki, K; Urao, T; Terao, T; Shinozaki, K

    1996-12-01

    Ten cDNAs of genes that were induced by dehydration stress were cloned by differential screening from the highly drought-tolerant legume, cowpea (Vigna unguiculata), a major crop in West Africa. The clones were collectively named CPRD (cowpea clones responsive to dehydration). Northern blot analysis revealed that nine of the CPRD genes were induced by dehydration stress, but the timing of induction of mRNA synthesis varied among the CPRD genes. We analyzed the effects of other environmental stresses on the expression of the CPRD8, CPRD14 and CPRD22 genes, and we found that these genes were strongly induced by high-salinity stress but not by cold or heat stress. Drought-stressed cowpea plants accumulated abscisic acid (ABA) to a level that was 160 times higher than that in unstressed plants. The CPRD8 and CPRD22 genes were induced to a significant extent by the application of exogenous ABA but the CPRD14 gene was not. These results indicate the existence of at least two signal-transduction pathways between the detection of water stress and the expression of CPRD genes in cowpea. Sequence analysis of CPRD8 and CPRD22 cDNAs revealed that they encoded putative proteins that were related to old yellow enzyme and group 2 LEA proteins, respectively. The protein encoded by CPRD14 exhibited sequence homology to dihydroflavonol-4-reductase (DFR) and vestitone reductase (VR). Old yellow enzyme, DFR and VR have not been identified as drought-inducible proteins in other plants, whereas LEA genes have been well characterized as drought-inducible genes. The various gene products might function to protect cells from environmental stress. PMID:9032963

  12. Combined effects of girdling and leaf removal on fluorescence characteristic of Alhagi sparsifolia leaf senescence.

    PubMed

    Tang, G; Li, X; Lin, L; Guo, H; Li, L

    2015-09-01

    Plant senescence is largely influenced by carbohydrate content. In order to investigate the impact of carbohydrate content on leaf senescence and photosystem II (PSII) during the senescence process, phloem girdling (PG), leaf removal (LR) and a combination of phloem girdling and leaf removal (GR) were performed on Alhagi sparsifolia (Fabaceae) at the end of the growing season. The results showed that during senescence, leaf soluble sugar content, starch content, the energy absorbed by the unit reaction centre (ABS/RC) increased; whereas, leaf photosynthetic rate, photosynthetic pigment content, maximum photochemical efficiency (φPo ) and energy used by the acceptor site in electron transfer (ETo/RC) decreased. The degree of change was PG > GR > CK (control) > LR. The results of the present work implied that phloem girdling (PG) significantly accelerated leaf senescence, and that single leaf removal (LR) slightly delayed leaf senescence; although leaf removal significantly delayed the senescence process on the girdled leaf (GR). Natural or delayed senescence only slightly inhibited the acceptor site of PSII and did not damage the donor site of PSII. On the other hand, induced senescence not only damaged the donor site of PSII (e.g. oxygen-evolving complex), but also significantly inhibited the acceptor site of PSII. In addition, leaf senescence led to an increase in the energy absorbed by the unit reaction centre (ABS/RC), which subsequently resulted in increasing excitation pressure in the reaction centre (DIo/RC), as well as additional saved Car for absorbing residual light energy and quenching reactive oxygen species during senescence. PMID:25662611

  13. Delayed ejaculation

    MedlinePlus

    Ejaculatory incompetence; Sex - delayed ejaculation; Retarded ejaculation; Anejaculation ... include: Religious background that makes the person view sex as sinful Lack of attraction for a partner ...

  14. Meta-analysis reveals that hydraulic traits explain cross-species patterns of drought-induced tree mortality across the globe.

    PubMed

    Anderegg, William R L; Klein, Tamir; Bartlett, Megan; Sack, Lawren; Pellegrini, Adam F A; Choat, Brendan; Jansen, Steven

    2016-05-01

    Drought-induced tree mortality has been observed globally and is expected to increase under climate change scenarios, with large potential consequences for the terrestrial carbon sink. Predicting mortality across species is crucial for assessing the effects of climate extremes on forest community biodiversity, composition, and carbon sequestration. However, the physiological traits associated with elevated risk of mortality in diverse ecosystems remain unknown, although these traits could greatly improve understanding and prediction of tree mortality in forests. We performed a meta-analysis on species' mortality rates across 475 species from 33 studies around the globe to assess which traits determine a species' mortality risk. We found that species-specific mortality anomalies from community mortality rate in a given drought were associated with plant hydraulic traits. Across all species, mortality was best predicted by a low hydraulic safety margin-the difference between typical minimum xylem water potential and that causing xylem dysfunction-and xylem vulnerability to embolism. Angiosperms and gymnosperms experienced roughly equal mortality risks. Our results provide broad support for the hypothesis that hydraulic traits capture key mechanisms determining tree death and highlight that physiological traits can improve vegetation model prediction of tree mortality during climate extremes. PMID:27091965

  15. Precipitation thresholds and drought-induced tree die-off: insights from patterns of Pinus edulis mortality along an environmental stress gradient.

    PubMed

    Clifford, Michael J; Royer, Patrick D; Cobb, Neil S; Breshears, David D; Ford, Paulette L

    2013-10-01

    Recent regional tree die-off events appear to have been triggered by a combination of drought and heat - referred to as 'global-change-type drought'. To complement experiments focused on resolving mechanisms of drought-induced tree mortality, an evaluation of how patterns of tree die-off relate to highly spatially variable precipitation is needed. Here, we explore precipitation relationships with a die-off event of pinyon pine (Pinus edulis Engelm.) in southwestern North America during the 2002-2003 global-change-type drought. Pinyon die-off and its relationship with precipitation was quantified spatially along a precipitation gradient in north-central New Mexico with standard field plot measurements of die-off combined with canopy cover derived from normalized burn ratio (NBR) from Landsat imagery. Pinyon die-off patterns revealed threshold responses to precipitation (cumulative 2002-2003) and vapor pressure deficit (VPD), with little to no mortality (< 10%) above 600 mm and below warm season VPD of c. 1.7 kPa. [Correction added after online publication 17 June 2013; in the preceding sentence, the word 'below' has been inserted.] Our results refine how precipitation patterns within a region influence pinyon die-off, revealing a precipitation and VPD threshold for tree mortality and its uncertainty band where other factors probably come into play - a response type that influences stand demography and landscape heterogeneity and is of general interest, yet has not been documented. PMID:23772860

  16. Delayed Senescence

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Researcher Dr. Yi Li developed a technique to manipulate certain characteristics of plant growth such as anit-senescence. For example, the tobacco leaf was clipped from a transgenic plant (right), and a wildtype plant (left). During ground-based laboratory studies, both leaves were left in a darkened area for 4 months. When retrieved, the wildtype plant leaf was dried-out and the transgenic leaf remained fresh and green. A variation of this technology that involves manipulating plant hormones has been conducted in space-based studies on tomato plants through BioServe Space Technologies. The transport and distribution of auxin, an important plant hormone has shown to be influenced by microgravity, which could lead to improving the quality of fruits and vegetables grown on Earth.

  17. Leaf gas exchange performance and the lethal water potential of five European species during drought.

    PubMed

    Li, Shan; Feifel, Marion; Karimi, Zohreh; Schuldt, Bernhard; Choat, Brendan; Jansen, Steven

    2016-02-01

    Establishing physiological thresholds to drought-induced mortality in a range of plant species is crucial in understanding how plants respond to severe drought. Here, five common European tree species were selected (Acer campestre L., Acer pseudoplatanus L., Carpinus betulus L., Corylus avellana L. and Fraxinus excelsior L.) to study their hydraulic thresholds to mortality. Photosynthetic parameters during desiccation and the recovery of leaf gas exchange after rewatering were measured. Stem vulnerability curves and leaf pressure-volume curves were investigated to understand the hydraulic coordination of stem and leaf tissue traits. Stem and root samples from well-watered and severely drought-stressed plants of two species were observed using transmission electron microscopy to visualize mortality of cambial cells. The lethal water potential (ψlethal) correlated with stem P99 (i.e., the xylem water potential at 99% loss of hydraulic conductivity, PLC). However, several plants that were stressed beyond the water potential at 100% PLC showed complete recovery during the next spring, which suggests that the ψlethal values were underestimated. Moreover, we observed a 1 : 1 relationship between the xylem water potential at the onset of embolism and stomatal closure, confirming hydraulic coordination between leaf and stem tissues. Finally, ultrastructural changes in the cytoplasm of cambium tissue and mortality of cambial cells are proposed to provide an alternative approach to investigate the point of no return associated with plant death. PMID:26614785

  18. Drought-induced increase in water-use efficiency reduces secondary tree growth and tracheid wall thickness in a Mediterranean conifer.

    PubMed

    Olano, José Miguel; Linares, Juan Carlos; García-Cervigón, Ana I; Arzac, Alberto; Delgado, Antonio; Rozas, Vicente

    2014-09-01

    In order to understand the impact of drought and intrinsic water-use efficiency (iWUE) on tree growth, we evaluated the relative importance of direct and indirect effects of water availability on secondary growth and xylem anatomy of Juniperus thurifera, a Mediterranean anisohydric conifer. Dendrochronological techniques, quantitative xylem anatomy, and (13)C/(12)C isotopic ratio were combined to develop standardized chronologies for iWUE, BAI (basal area increment), and anatomical variables on a 40-year-long annually resolved series for 20 trees. We tested the relationship between iWUE and secondary growth at short-term (annual) and long-term (decadal) temporal scales to evaluate whether gains in iWUE may lead to increases in secondary growth. We obtained a positive long-term correlation between iWUE and BAI, simultaneously with a negative short-term correlation between them. Furthermore, BAI and iWUE were correlated with anatomical traits related to carbon sink or storage (tracheid wall thickness and ray parenchyma amount), but no significant correlation with conductive traits (tracheid lumen) was found. Water availability during the growing season significantly modulated tree growth at the xylem level, where growth rates and wood anatomical traits were affected by June precipitation. Our results are consistent with a drought-induced limitation of tree growth response to rising CO2, despite the trend of rising iWUE being maintained. We also remark the usefulness of exploring this relationship at different temporal scales to fully understand the actual links between iWUE and secondary growth dynamics. PMID:24958369

  19. Delayed discharge.

    PubMed

    Allen, Daniel

    2016-07-01

    Essential facts Delays in discharging older peo ple from hospital cost the NHS £820 million a year, according to a report from the National Audit Office (NAO). Last year in acute hospitals, 1.15 million bed days were lost to delayed transfers of care, an increase of 31% since 2013. The NAO says rising demand for NHS services is compounded by reduced local authority spending on adult social care - down by 10% since 2009-10. PMID:27380673

  20. Developmental delay

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nutrition support is essential for the care of the child with developmental delay. After a thorough evaluation, an individualized intervention plan that accounts for the child’s nutrition status, feeding ability, and medical condition may be determined. Nutrition assessments may be performed at leas...

  1. Assessing soybean leaf area and leaf biomass by spectral measurements

    NASA Technical Reports Server (NTRS)

    Holben, B. N.; Tucker, C. J.; Fan, C. J.

    1979-01-01

    Red and photographic infrared spectral radiances were correlated with soybean total leaf area index, green leaf area index, chlorotic leaf area index, green leaf biomass, chlorotic leaf biomass, and total biomass. The most significant correlations were found to exist between the IR/red radiance ratio data and green leaf area index and/or green leaf biomass (r squared equals 0.85 and 0.86, respectively). These findings demonstrate that remote sensing data can supply information basic to soybean canopy growth, development, and status by nondestructive determination of the green leaf area or green leaf biomass.

  2. Leaf Phenological Characters of Main Tree Species in Urban Forest of Shenyang

    PubMed Central

    Xu, Sheng; Xu, Wenduo; Chen, Wei; He, Xingyuan; Huang, Yanqing; Wen, Hua

    2014-01-01

    Background Plant leaves, as the main photosynthetic organs and the high energy converters among primary producers in terrestrial ecosystems, have attracted significant research attention. Leaf lifespan is an adaptive characteristic formed by plants to obtain the maximum carbon in the long-term adaption process. It determines important functional and structural characteristics exhibited in the environmental adaptation of plants. However, the leaf lifespan and leaf characteristics of urban forests were not studied up to now. Methods By using statistic, linear regression methods and correlation analysis, leaf phenological characters of main tree species in urban forest of Shenyang were observed for five years to obtain the leafing phenology (including leafing start time, end time, and duration), defoliating phenology (including defoliation start time, end time, and duration), and the leaf lifespan of the main tree species. Moreover, the relationships between temperature and leafing phenology, defoliating phenology, and leaf lifespan were analyzed. Findings The timing of leafing differed greatly among species. The early leafing species would have relatively early end of leafing; the longer it took to the end of leafing would have a later time of completed leafing. The timing of defoliation among different species varied significantly, the early defoliation species would have relatively longer duration of defoliation. If the mean temperature rise for 1°C in spring, the time of leafing would experience 5 days earlier in spring. If the mean temperature decline for 1°C, the time of defoliation would experience 3 days delay in autumn. Interpretation There is significant correlation between leaf longevity and the time of leafing and defoliation. According to correlation analysis and regression analysis, there is significant correlation between temperature and leafing and defoliation phenology. Early leafing species would have a longer life span and consequently have

  3. Delaying obsolescence.

    PubMed

    Lawlor, Rob

    2015-04-01

    This paper argues that those who emphasise that designers and engineers need to plan for obsolescence are too conservative. Rather, in addition to planning for obsolescence, designers and engineers should also think carefully about what they could do in order delay obsolescence. They should so this by thinking about the design itself, thinking of ways in which products could be useful and appealing for longer before becoming obsolete, as well thinking about the wider context in terms of the marketing of products, and also the social and legal. The paper also considers objections that these suggestions are unrealistically idealistic, failing to recognise the economic realities. I respond to these objections appealing to research in advertising, psychology, cognitive linguistics, philosophy, history, and economics, as well as drawing on the Statement of Ethical Principles developed by the Royal Academy of Engineering and the Engineering Council. PMID:24792878

  4. Changes in leaf water relations, gas exchange, growth and flowering quality in potted geranium plants irrigated with different water regimes.

    PubMed

    Sánchez-Blanco, Ma Jesús; Alvarez, Sara; Navarro, Alejandra; Bañón, Sebastián

    2009-03-15

    Geranium plants are an important part of urban green areas but suffer from drought, especially when grown in containers with a limited volume of medium. In this experiment, we examined the response of potted geraniums to different irrigation levels. Geranium (Pelargoniumxhortorum L.) seedlings were grown in a growth chamber and exposed to three irrigation treatments, whereby the plants were irrigated to container capacity (control), 60% of the control (moderate deficit irrigation, MDI), or 40% of the control (severe deficit irrigation, SDI). Deficit irrigation was maintained for 2 months, and then all the plants were exposed to a recovery period of 112 month. Exposure to drought induced a decrease in shoot dry weight and leaf area and an increase in the root/shoot ratio. Height and plant width were significantly inhibited by the SDI, while flower color parameters were not affected by deficit treatment. The number of wilting and yellow leaves increased, coinciding with the increase in the number of inflorescences and open flowers. Deficit irrigation led to a leaf water potential of about -0.8MPa at midday, which could have caused an important decrease in stomatal conductance, affecting the photosynthetic rate (Pn). Chlorophyll fluorescence (Fvm) values of 0.80 in all treatments throughout the experiment demonstrate the lack of drought-induced damage to PSII photochemistry. Pressure-volume analysis revealed low osmotic adjustment values of 0.2MPa in the SDI treatment, accompanied by increases in the bulk tissue elastic modulus (epsilon, wall rigidity) and resulting in turgor loss at lower leaf water potential values (-1.38MPa compared with -1.0MPa for the control). Leaf water potential values throughout the experiment below those for Psitlp were not found at any sampling time. By the end of the recovery period, the leaf water potential, stomatal conductance and net photosynthesis had recovered. We infer from these results that moderate deficit irrigation in geranium

  5. Yellow leaf blotch

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Yellow leaf blotch occurs worldwide in temperate climates. The disease is reported from countries in Asia, Australasia, Oceania, Europe, North America, Central America, the West Indies, and South America. In the northern Great Plains of North America, it is often the major leaf disease on alfalfa....

  6. Drought-Induced Effects on Nitrate Reductase Activity and mRNA and on the Coordination of Nitrogen and Carbon Metabolism in Maize Leaves1

    PubMed Central

    Foyer, Christine H.; Valadier, Marie-Hélène; Migge, Andrea; Becker, Thomas W.

    1998-01-01

    Maize (Zea mays L.) plants were grown to the nine-leaf stage. Despite a saturating N supply, the youngest mature leaves (seventh position on the stem) contained little NO3− reserve. Droughted plants (deprived of nutrient solution) showed changes in foliar enzyme activities, mRNA accumulation, photosynthesis, and carbohydrate and amino acid contents. Total leaf water potential and CO2 assimilation rates, measured 3 h into the photoperiod, decreased 3 d after the onset of drought. Starch, glucose, fructose, and amino acids, but not sucrose (Suc), accumulated in the leaves of droughted plants. Maximal extractable phosphoenolpyruvate carboxylase activities increased slightly during water deficit, whereas the sensitivity of this enzyme to the inhibitor malate decreased. Maximal extractable Suc phosphate synthase activities decreased as a result of water stress, and there was an increase in the sensitivity to the inhibitor orthophosphate. A correlation between maximal extractable foliar nitrate reductase (NR) activity and the rate of CO2 assimilation was observed. The NR activation state and maximal extractable NR activity declined rapidly in response to drought. Photosynthesis and NR activity recovered rapidly when nutrient solution was restored at this point. The decrease in maximal extractable NR activity was accompanied by a decrease in NR transcripts, whereas Suc phosphate synthase and phosphoenolpyruvate carboxylase mRNAs were much less affected. The coordination of N and C metabolism is retained during drought conditions via modulation of the activities of Suc phosphate synthase and NR commensurate with the prevailing rate of photosynthesis. PMID:9576798

  7. Estimating Leaf Water Potential of Giant Sequoia Trees from Airborne Hyperspectral Imagery

    NASA Astrophysics Data System (ADS)

    Francis, E. J.; Asner, G. P.

    2015-12-01

    Recent drought-induced forest dieback events have motivated research on the mechanisms of tree survival and mortality during drought. Leaf water potential, a measure of the force exerted by the evaporation of water from the leaf surface, is an indicator of plant water stress and can help predict tree mortality in response to drought. Scientists have traditionally measured water potentials on a tree-by-tree basis, but have not been able to produce maps of tree water potential at the scale of a whole forest, leaving forest managers unaware of forest drought stress patterns and their ecosystem-level consequences. Imaging spectroscopy, a technique for remote measurement of chemical properties, has been used to successfully estimate leaf water potentials in wheat and maize crops and pinyon-pine and juniper trees, but these estimates have never been scaled to the canopy level. We used hyperspectral reflectance data collected by the Carnegie Airborne Observatory (CAO) to map leaf water potentials of giant sequoia trees (Sequoiadendron giganteum) in an 800-hectare grove in Sequoia National Park. During the current severe drought in California, we measured predawn and midday leaf water potentials of 48 giant sequoia trees, using the pressure bomb method on treetop foliage samples collected with tree-climbing techniques. The CAO collected hyperspectral reflectance data at 1-meter resolution from the same grove within 1-2 weeks of the tree-level measurements. A partial least squares regression was used to correlate reflectance data extracted from the 48 focal trees with their water potentials, producing a model that predicts water potential of giant sequoia trees. Results show that giant sequoia trees can be mapped in the imagery with a classification accuracy of 0.94, and we predicted the water potential of the mapped trees to assess 1) similarities and differences between a leaf water potential map and a canopy water content map produced from airborne hyperspectral data, 2

  8. Leaf growth is conformal.

    PubMed

    Alim, Karen; Armon, Shahaf; Shraiman, Boris I; Boudaoud, Arezki

    2016-01-01

    Growth pattern dynamics lie at the heart of morphogenesis. Here, we investigate the growth of plant leaves. We compute the conformal transformation that maps the contour of a leaf at a given stage onto the contour of the same leaf at a later stage. Based on the mapping we predict the local displacement field in the leaf blade and find it to agree with the experimentally measured displacement field to 92%. This approach is applicable to any two-dimensional system with locally isotropic growth, enabling the deduction of the whole growth field just from observation of the tissue contour. PMID:27597439

  9. GhDRIN1, a novel drought-induced gene of upland cotton (Gossypium hirsutum L.) confers abiotic and biotic stress tolerance in transgenic tobacco.

    PubMed

    Dhandapani, Gurusamy; Lakshmi Prabha, Azhagiyamanavalan; Kanakachari, Mogilicherla; Phanindra, Mullapudi Lakshmi Venkata; Prabhakaran, Narayanasamy; Gothandapani, Sellamuthu; Padmalatha, Kethireddy Venkata; Solanke, Amolkumar U; Kumar, Polumetla Ananda

    2015-04-01

    A novel stress tolerance cDNA fragment encoding GhDRIN1 protein was identified and its regulation was studied in cotton boll tissues and seedlings subjected to various biotic and abiotic stresses. Phylogenetic and conserved domain prediction indicated that GhDRIN1 was annotated with a hypothetical protein of unknown function. Subcellular localization showed that GhDRIN1 is localized in the chloroplasts. The promoter sequence was isolated and subjected to in silico study. Various cis-acting elements responsive to biotic and abiotic stresses and hormones were found. Transgenic tobacco seedlings exhibited better growth on amended MS medium and showed minimal leaf damage in insect bioassays carried out with Helicoverpa armigera larvae. Transgenic tobacco showed better tolerance to water-deficit and fast recovered upon rewatering. Present work demonstrated that GhDRIN1, a novel stress tolerance gene of cotton, positively regulates the response to biotic and abiotic stresses in transgenic tobacco. PMID:25413882

  10. Development of an Assimilation Scheme for the Estimation of Drought-Induced Yield Losses Based on Multi-Source Remote Sensing and the AcquaCrop Model

    NASA Astrophysics Data System (ADS)

    Silvestro, Paolo Cosmo; Casa, Raffaele; Pignatti, Stefano; Castaldi, Fabio; Yang, Hao; Yang, Guijun

    2014-11-01

    In the context of the Dragon-3 Farmland Drought project, our research deals with the development of methods for the assimilation of biophysical variables, estimated from multi-source remote sensing, into the AquaCrop model, in order to estimate the yield losses due to drought both at the farm and at the regional scale. The first part of this project was employed to refine a methodology to obtain maps of leaf area index (LAI), canopy cover (CC), fraction of adsorbed photosynthetically active radiation (FAPAR) and chlorophyll (Cab) from satellite optical data, using algorithms based on the training of artificial neural networks (ANN) on PROSAIL model simulations. In the second part, retrieved values of CC were assimilated into the AquaCrop model using the assimilation method of the Ensemble Kalman Filter to estimate grain wheat yield at the field scale.

  11. 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

  12. Deer predation on leaf miners via leaf abscission

    NASA Astrophysics Data System (ADS)

    Yamazaki, Kazuo; Sugiura, Shinji

    2008-03-01

    The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer ( Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

  13. Strigolactone Regulates Leaf Senescence in Concert with Ethylene in Arabidopsis.

    PubMed

    Ueda, Hiroaki; Kusaba, Makoto

    2015-09-01

    Leaf senescence is not a passive degenerative process; it represents a process of nutrient relocation, in which materials are salvaged for growth at a later stage or to produce the next generation. Leaf senescence is regulated by various factors, such as darkness, stress, aging, and phytohormones. Strigolactone is a recently identified phytohormone, and it has multiple functions in plant development, including repression of branching. Although strigolactone is implicated in the regulation of leaf senescence, little is known about its molecular mechanism of action. In this study, strigolactone biosynthesis mutant strains of Arabidopsis (Arabidopsis thaliana) showed a delayed senescence phenotype during dark incubation. The strigolactone biosynthesis genes MORE AXIALLY GROWTH3 (MAX3) and MAX4 were drastically induced during dark incubation and treatment with the senescence-promoting phytohormone ethylene, suggesting that strigolactone is synthesized in the leaf during leaf senescence. This hypothesis was confirmed by a grafting experiment using max4 as the stock and Columbia-0 as the scion, in which the leaves from the Columbia-0 scion senesced earlier than max4 stock leaves. Dark incubation induced the synthesis of ethylene independent of strigolactone. Strigolactone biosynthesis mutants showed a delayed senescence phenotype during ethylene treatment in the light. Furthermore, leaf senescence was strongly accelerated by the application of strigolactone in the presence of ethylene and not by strigolactone alone. These observations suggest that strigolactone promotes leaf senescence by enhancing the action of ethylene. Thus, dark-induced senescence is regulated by a two-step mechanism: induction of ethylene synthesis and consequent induction of strigolactone synthesis in the leaf. PMID:25979917

  14. 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.

  15. 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

  16. Drought tolerance of clonal Malus determined from measurements of stomatal conductance and leaf water potential.

    PubMed

    Atkinson, C. J.; Policarpo, M.; Webster, A. D.; Kingswell, G.

    2000-04-01

    We examined tolerance to soil drying in clonally propagated apple (Malus domestica Borkh.) rootstocks used to control shoot growth of grafted scions. We measured leaf conductance to water vapor (g(L)) and leaf water potential (Psi(L)) in a range of potted, greenhouse-grown rootstocks (M9, M26, M27, MM111, AR69-7, AR295-6, AR360-19, AR486-1 and AR628-2) as the water supply was gradually reduced. Irrespective of the amount of available water, rootstocks that promoted scion shoot growth (M26 and MM111) generally had higher g(L) and more negative Psi(L) than rootstocks that restricted scion shoot growth (M27 and M9). After about 37 days of reduced water supply, there were significant decreases in g(L) and Psi(L) in all rootstocks compared with well-watered controls. In all treatments, the slope of the relationship between log (g(L)) and Psi(L) was positive, except for rootstocks AR295-6, AR628-2 and AR486-1 in the severe-drought treatment, where the drought-induced change in the relationship suggests that rapid stomatal closure occurred when leaf water potentials fell below -2.0 MPa. This drought response was associated with increased root biomass production. Rootstock M26 showed little stomatal closure even when its water potential fell below -2.0 MPa, and there was no effect of drought on root biomass production. We conclude that differences among rootstocks in the way that g(L) and Psi(L) respond to drought reflect differences in the mechanisms whereby they tolerate soil drying. We suggest that these differences are related to differences among the rootstocks in their ability to control shoot growth. PMID:12651437

  17. Analysis of Drought-Induced Proteomic and Metabolomic Changes in Barley (Hordeum vulgare L.) Leaves and Roots Unravels Some Aspects of Biochemical Mechanisms Involved in Drought Tolerance

    PubMed Central

    Chmielewska, Klaudia; Rodziewicz, Paweł; Swarcewicz, Barbara; Sawikowska, Aneta; Krajewski, Paweł; Marczak, Łukasz; Ciesiołka, Danuta; Kuczyńska, Anetta; Mikołajczak, Krzysztof; Ogrodowicz, Piotr; Krystkowiak, Karolina; Surma, Maria; Adamski, Tadeusz; Bednarek, Paweł; Stobiecki, Maciej

    2016-01-01

    In this study, proteomic and metabolomic changes in leaves and roots of two barley (Hordeum vulgare L.) genotypes, with contrasting drought tolerance, subjected to water deficit were investigated. Our two-dimensional electrophoresis (2D-PAGE) combined with matrix-assisted laser desorption time of flight mass spectrometry (MALDI-TOF and MALDI-TOF/TOF) analyses revealed 121 drought-responsive proteins in leaves and 182 in roots of both genotypes. Many of the identified drought-responsive proteins were associated with processes that are typically severely affected during water deficit, including photosynthesis and carbon metabolism. However, the highest number of identified leaf and root proteins represented general defense mechanisms. In addition, changes in the accumulation of proteins that represent processes formerly unassociated with drought response, e.g., phenylpropanoid metabolism, were also identified. Our tandem gas chromatography – time of flight mass spectrometry (GC/MS TOF) analyses revealed approximately 100 drought-affected low molecular weight compounds representing various metabolite types with amino acids being the most affected metabolite class. We compared the results from proteomic and metabolomic analyses to search for existing relationship between these two levels of molecular organization. We also uncovered organ specificity of the observed changes and revealed differences in the response to water deficit of drought susceptible and tolerant barley lines. Particularly, our results indicated that several of identified proteins and metabolites whose accumulation levels were increased with drought in the analyzed susceptible barley variety revealed elevated constitutive accumulation levels in the drought-resistant line. This may suggest that constitutive biochemical predisposition represents a better drought tolerance mechanism than inducible responses. PMID:27512399

  18. An enhanced plant lipidomics method based on multiplexed liquid chromatography-mass spectrometry reveals additional insights into cold- and drought-induced membrane remodeling.

    PubMed

    Tarazona, Pablo; Feussner, Kirstin; Feussner, Ivo

    2015-11-01

    Within the lipidome of plants a few bulk molecular species hamper the detection of the rest, which are present at relatively low levels. In addition, low-abundance species are often masked by numerous isobaric interferences, such as those caused by isoelemental species and isotopologues. This scenario not only means that minor species are underrepresented, but also leads to potential misidentifications and limits the structural information gathered by lipidomics approaches. In order to overcome these limitations we have developed a multiplexed liquid chromatography-mass spectrometry lipidomics platform able to achieve an enhanced coverage of plant lipidomes. The platform is based on a single extraction step followed by a series of ultra-performance liquid chromatography separations. Post-column flow is then directed to both a triple quadrupole analyzer for targeted profiling and a time-of-flight analyzer for accurate mass analysis. As a proof of concept, plants were subjected to cold or drought, which are known to trigger widespread remodeling events in plant cell membranes. Analysis of the leaf lipidome yielded 393 molecular species within 23 different lipid classes. This enhanced coverage allowed us to identify lipid molecular species and even classes that are altered upon stress, allowing hypotheses on role of glycosylinositolphosphoceramides (GIPC), steryl glycosides (SG) and acylated steryl glycosides (ASG) in drought stress to be addressed and confirming the findings from numerous previous studies with a single, wide-ranging lipidomics approach. This extended our knowledge on membrane remodeling during the drought response, integrating sphingolipids and sterol lipids into the current glycerolipid-based model. PMID:26340975

  19. Analysis of Drought-Induced Proteomic and Metabolomic Changes in Barley (Hordeum vulgare L.) Leaves and Roots Unravels Some Aspects of Biochemical Mechanisms Involved in Drought Tolerance.

    PubMed

    Chmielewska, Klaudia; Rodziewicz, Paweł; Swarcewicz, Barbara; Sawikowska, Aneta; Krajewski, Paweł; Marczak, Łukasz; Ciesiołka, Danuta; Kuczyńska, Anetta; Mikołajczak, Krzysztof; Ogrodowicz, Piotr; Krystkowiak, Karolina; Surma, Maria; Adamski, Tadeusz; Bednarek, Paweł; Stobiecki, Maciej

    2016-01-01

    In this study, proteomic and metabolomic changes in leaves and roots of two barley (Hordeum vulgare L.) genotypes, with contrasting drought tolerance, subjected to water deficit were investigated. Our two-dimensional electrophoresis (2D-PAGE) combined with matrix-assisted laser desorption time of flight mass spectrometry (MALDI-TOF and MALDI-TOF/TOF) analyses revealed 121 drought-responsive proteins in leaves and 182 in roots of both genotypes. Many of the identified drought-responsive proteins were associated with processes that are typically severely affected during water deficit, including photosynthesis and carbon metabolism. However, the highest number of identified leaf and root proteins represented general defense mechanisms. In addition, changes in the accumulation of proteins that represent processes formerly unassociated with drought response, e.g., phenylpropanoid metabolism, were also identified. Our tandem gas chromatography - time of flight mass spectrometry (GC/MS TOF) analyses revealed approximately 100 drought-affected low molecular weight compounds representing various metabolite types with amino acids being the most affected metabolite class. We compared the results from proteomic and metabolomic analyses to search for existing relationship between these two levels of molecular organization. We also uncovered organ specificity of the observed changes and revealed differences in the response to water deficit of drought susceptible and tolerant barley lines. Particularly, our results indicated that several of identified proteins and metabolites whose accumulation levels were increased with drought in the analyzed susceptible barley variety revealed elevated constitutive accumulation levels in the drought-resistant line. This may suggest that constitutive biochemical predisposition represents a better drought tolerance mechanism than inducible responses. PMID:27512399

  20. Maple Leaf Outdoor Centre.

    ERIC Educational Resources Information Center

    Maguire, Molly; Gunton, Ric

    2000-01-01

    Maple Leaf Outdoor Centre (Ontario) has added year-round outdoor education facilities and programs to help support its summer camp for disadvantaged children. Schools, youth centers, religious groups, and athletic teams conduct their own programs, collaborate with staff, or use staff-developed programs emphasizing adventure education and personal…

  1. Raspberry leaf curl virus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Raspberry leaf curl virus (RLCV) is limited to hosts in the genus Rubus and is transmitted persistently by the small raspberry aphid, Aphis rubicola Oestlund. It is found only in North America, principally in the northeastern United States and southeastern Canada and in the Rocky Mountain regions of...

  2. 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...

  3. After more than a decade of soil moisture deficit, tropical rainforest trees maintain photosynthetic capacity, despite increased leaf respiration.

    PubMed

    Rowland, Lucy; Lobo-do-Vale, Raquel L; Christoffersen, Bradley O; Melém, Eliane A; Kruijt, Bart; Vasconcelos, Steel S; Domingues, Tomas; Binks, Oliver J; Oliveira, Alex A R; Metcalfe, Daniel; da Costa, Antonio C L; Mencuccini, Maurizio; Meir, Patrick

    2015-12-01

    Determining climate change feedbacks from tropical rainforests requires an understanding of how carbon gain through photosynthesis and loss through respiration will be altered. One of the key changes that tropical rainforests may experience under future climate change scenarios is reduced soil moisture availability. In this study we examine if and how both leaf photosynthesis and leaf dark respiration acclimate following more than 12 years of experimental soil moisture deficit, via a through-fall exclusion experiment (TFE) in an eastern Amazonian rainforest. We find that experimentally drought-stressed trees and taxa maintain the same maximum leaf photosynthetic capacity as trees in corresponding control forest, independent of their susceptibility to drought-induced mortality. We hypothesize that photosynthetic capacity is maintained across all treatments and taxa to take advantage of short-lived periods of high moisture availability, when stomatal conductance (gs ) and photosynthesis can increase rapidly, potentially compensating for reduced assimilate supply at other times. Average leaf dark respiration (Rd ) was elevated in the TFE-treated forest trees relative to the control by 28.2 ± 2.8% (mean ± one standard error). This mean Rd value was dominated by a 48.5 ± 3.6% increase in the Rd of drought-sensitive taxa, and likely reflects the need for additional metabolic support required for stress-related repair, and hydraulic or osmotic maintenance processes. Following soil moisture deficit that is maintained for several years, our data suggest that changes in respiration drive greater shifts in the canopy carbon balance, than changes in photosynthetic capacity. PMID:26179437

  4. Delayed orgasm and anorgasmia.

    PubMed

    Jenkins, Lawrence C; Mulhall, John P

    2015-11-01

    Delayed orgasm/anorgasmia defined as the persistent or recurrent difficulty, delay in, or absence of attaining orgasm after sufficient sexual stimulation, which causes personal distress. Delayed orgasm and anorgasmia are associated with significant sexual dissatisfaction. A focused medical history can shed light on the potential etiologies, which include medications, penile sensation loss, endocrinopathies, penile hyperstimulation, and psychological etiologies. Unfortunately, there are no excellent pharmacotherapies for delayed orgasm/anorgasmia, and treatment revolves largely around addressing potential causative factors and psychotherapy. PMID:26439762

  5. Speech and Language Delay

    MedlinePlus

    MENU Return to Web version Speech and Language Delay Overview How do I know if my child has speech delay? Every child develops at his or her ... of the same age, the problem may be speech delay. Your doctor may think your child has ...

  6. Delay Discounting and Gambling

    PubMed Central

    Madden, Gregory J.; Francisco, Monica T.; Brewer, Adam T.; Stein, Jeffrey S.

    2011-01-01

    Delay discounting describes the decline in the value of a reinforcer as the delay to that reinforcer increases. A review of the available studies revealed that steep delay discounting is positively correlated with problem or pathological gambling. One hypothesis regarding this correlation derives from the discounting equation proposed by Mazur (1989). According to the equation, steeper discounting renders the difference between fixed-delayed rewards and gambling-like variable-delayed rewards larger; with the latter being more valuable. The present study was designed to test this prediction by first assessing rats’ impulsive choices across four delays to a larger-later reinforcer. A second condition quantified strength of preference for mixed- over fixed-delays, with the duration of the latter adjusted between sessions to achieve indifference. Strength of preference for the mixed-delay alternative is given by the fixed delay at indifference (lower fixed-delay values reflect stronger preferences). Percent impulsive choice was not correlated with the value of the fixed delay at indifference and, therefore, the prediction of the hyperbolic model of gambling was not supported. A follow-up assessment revealed a significant decrease in impulsive choice after the second condition. This shift in impulsive choice could underlie the failure to observe the predicted correlation between impulsive choice and degree of preference for mixed- over fixed delays. PMID:21352902

  7. Reflectance measurements of cotton leaf senescence altered by mepiquat chloride

    NASA Technical Reports Server (NTRS)

    Gausman, H. W.; Escobar, D. E.; Rodriguez, R. R. (Principal Investigator)

    1982-01-01

    Spectrophotometric reflectance measurements were made on plant-attached leaves to evaluate growth chamber-grown cotton leaf (Gossypium hirsutum L.) senescence (chlorophyll degradation as criterion) that was delayed by mepiquat chloride (1,1-dimethylpiperidinium chloride) rates of 0, 10, 40, 70, and 100 g a.i./ha. Mepiquat chloride (MC increased both chlorophyll and leaf water contents as compared with that of untreated leaves. Reflectance was inversely and linearly correlated (r = -0.873**) with eater content at the 1.65 micrometer wavelength and was inversely correlated (r = -0.812**) with chlorophyll concentration at the 0.55 micrometer wavelength but best fit a quadratic equation. Either wavelength measurement might be useful to remotely detect cotton leaf senescence or fields of MC-treated cotton plants.

  8. 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.

  9. A novel NAP member GhNAP is involved in leaf senescence in Gossypium hirsutum

    PubMed Central

    Fan, Kai; Bibi, Noreen; Gan, Susheng; Li, Feng; Yuan, Shuna; Ni, Mi; Wang, Ming; Shen, Hao; Wang, Xuede

    2015-01-01

    Premature leaf senescence has a negative influence on the yield and quality of cotton, and several genes have been found to regulate leaf senescence. Howeer, many underlying transcription factors are yet to be identified. In this study, a NAP-like transcription factor (GhNAP) was isolated from Gossypium hirsutum. GhNAP has the typical NAC structure and a conserved novel subdomain in its divergent transcription activation region (TAR). GhNAP was demonstrated to be a nuclear protein, and it showed transcriptional activation activity in yeast. Furthermore, the expression of GhNAP was closely associated with leaf senescence. GhNAP could rescue the delayed-senescence phenotype of the atnap null mutant. Overexpression of GhNAP could cause precocious senescence in Arabidopsis. However, down-regulation of GhNAP delayed leaf senescence in cotton, and affected cotton yield and its fibre quality. Moreover, the expression of GhNAP can be induced by abscisic acid (ABA), and the delayed leaf senescence phenotype in GhNAPi plants might be caused by the decreased ABA level and reduced expression level of ABA-responsive genes. All of the results suggested that GhNAP could regulate the leaf senescence via the ABA-mediated pathways and was further related to the yield and quality in cotton. PMID:25991739

  10. Overwintering evergreen oaks reverse typical relationships between leaf traits in a species spectrum

    PubMed Central

    Harayama, Hisanori; Ishida, Atsushi

    2016-01-01

    The leaf economics spectrum has given us a fundamental understanding of the species variations in leaf variables. Across plant species, tight correlations among leaf mass per area (LMA), mass-based nitrogen (Nm) and photosynthetic rate (Am) and leaf lifespan have been well known as trade-offs in leaf carbon economy. However, the regional or biome-level correlations may not be necessary to correspond with the global-scale analysis. Here, we show that almost all leaf variables in overwintering evergreen oaks in Japan were relatively well included within the evergreen-broadleaved trees in worldwide temperate forests, but Nm was more consistent with that in deciduous broadleaved trees. Contrary to the universal correlations, the correlation between Am and Nm among the evergreen oaks was negative and the correlation between Am and LMA disappeared. The unique performance was due to specific nitrogen allocation within leaves, i.e. the evergreen oaks with later leaf maturation had lower Nm but higher nitrogen allocation to photosynthetic enzymes within leaves, to enhance carbon gain against the delayed leaf maturation and the shortened photosynthetic period due to cold winters. Our data demonstrate that correlations between leaf variables in a local scale are occasionally different from averaged global-scale datasets, because of the constraints in each biome. PMID:27493781

  11. Overwintering evergreen oaks reverse typical relationships between leaf traits in a species spectrum.

    PubMed

    Harayama, Hisanori; Ishida, Atsushi; Yoshimura, Jin

    2016-07-01

    The leaf economics spectrum has given us a fundamental understanding of the species variations in leaf variables. Across plant species, tight correlations among leaf mass per area (LMA), mass-based nitrogen (N m) and photosynthetic rate (A m) and leaf lifespan have been well known as trade-offs in leaf carbon economy. However, the regional or biome-level correlations may not be necessary to correspond with the global-scale analysis. Here, we show that almost all leaf variables in overwintering evergreen oaks in Japan were relatively well included within the evergreen-broadleaved trees in worldwide temperate forests, but N m was more consistent with that in deciduous broadleaved trees. Contrary to the universal correlations, the correlation between A m and N m among the evergreen oaks was negative and the correlation between A m and LMA disappeared. The unique performance was due to specific nitrogen allocation within leaves, i.e. the evergreen oaks with later leaf maturation had lower N m but higher nitrogen allocation to photosynthetic enzymes within leaves, to enhance carbon gain against the delayed leaf maturation and the shortened photosynthetic period due to cold winters. Our data demonstrate that correlations between leaf variables in a local scale are occasionally different from averaged global-scale datasets, because of the constraints in each biome. PMID:27493781

  12. CGI delay compensation

    NASA Technical Reports Server (NTRS)

    Mcfarland, Richard E.

    1986-01-01

    Computer-generated graphics in real-time helicopter simulation produces objectionable scene-presentation time delays. In the flight simulation laboratory at Ames Research Center, it has been determined that these delays have an adverse influence on pilot performance during aggressive tasks such as nap-of-the-earth (NOE) maneuvers. Using contemporary equipment, computer-generated image (CGI) time delays are an unavoidable consequence of the operations required for scene generation. However, providing that magnitide distortions at higher frequencies are tolerable, delay compensation is possible over a restricted frequency range. This range, assumed to have an upper limit of perhaps 10 or 15 rad/sec, conforms approximately to the bandwidth associated with helicopter handling qualities research. A compensation algorithm is introduced here and evaluated in terms of tradeoffs in frequency responses. The algorithm has a discrete basis and accommodates both a large, constant transport delay interval and a periodic delay interval, as associated with asynchronous operations.

  13. 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

  14. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...

  15. VARIABLE TIME DELAY MEANS

    DOEpatents

    Clemensen, R.E.

    1959-11-01

    An electrically variable time delay line is described which may be readily controlled simuitaneously with variable impedance matching means coupied thereto such that reflections are prevented. Broadly, the delay line includes a signal winding about a magnetic core whose permeability is electrically variable. Inasmuch as the inductance of the line varies directly with the permeability, the time delay and characteristic impedance of the line both vary as the square root of the permeability. Consequently, impedance matching means may be varied similariy and simultaneously w:th the electrically variable permeability to match the line impedance over the entire range of time delay whereby reflections are prevented.

  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

  17. Digital time delay

    DOEpatents

    Martin, A.D.

    1986-05-09

    Method and apparatus are provided for generating an output pulse following a trigger pulse at a time delay interval preset with a resolution which is high relative to a low resolution available from supplied clock pulses. A first lumped constant delay provides a first output signal at predetermined interpolation intervals corresponding to the desired high resolution time interval. Latching circuits latch the high resolution data to form a first synchronizing data set. A selected time interval has been preset to internal counters and corrected for circuit propagation delay times having the same order of magnitude as the desired high resolution. Internal system clock pulses count down the counters to generate an internal pulse delayed by an internal which is functionally related to the preset time interval. A second LCD corrects the internal signal with the high resolution time delay. A second internal pulse is then applied to a third LCD to generate a second set of synchronizing data which is complementary with the first set of synchronizing data for presentation to logic circuits. The logic circuits further delay the internal output signal with the internal pulses. The final delayed output signal thereafter enables the output pulse generator to produce the desired output pulse at the preset time delay interval following input of the trigger pulse.

  18. Exserohilum Leaf Spot on Tigergrass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tigergrass (Thysanolaena maxima (Roxb.) Kuntze ) is a popular ornamental grass grown throughout landscapes in South Florida. In the summer of 2006, a leaf spot was observed on tigergrass in the landscape and a commercial nursery in Homestead, FL. The causal agent of the leaf spot was isolated, cha...

  19. How to pattern a leaf

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leaf development presents a tremendous resource for tackling the question of patterning in biology. Leaves can be simple or highly dissected. They may have elaborated parts such as the tendrils of a pea leaf or the rolled blade of a carnivorous pitcher plant. Despite the variation in size, shape, an...

  20. Identification of Drought Induced Genes in Peanut

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plants are challenged with environmental stresses such as drought, high-salinity, and high and low temperature which can adversely affect growth and development and ultimate reduce yield and quality. In order to cope with the dynamic adverse environmental changes, plants have evolved a complex netw...

  1. Early Autumn Senescence in Red Maple (Acer rubrum L.) Is Associated with High Leaf Anthocyanin Content

    PubMed Central

    Anderson, Rachel; Ryser, Peter

    2015-01-01

    Several theories exist about the role of anthocyanins in senescing leaves. To elucidate factors contributing to variation in autumn leaf anthocyanin contents among individual trees, we analysed anthocyanins and other leaf traits in 27 individuals of red maple (Acer rubrum L.) over two growing seasons in the context of timing of leaf senescence. Red maple usually turns bright red in the autumn, but there is considerable variation among the trees. Leaf autumn anthocyanin contents were consistent between the two years of investigation. Autumn anthocyanin content strongly correlated with degree of chlorophyll degradation mid to late September, early senescing leaves having the highest concentrations of anthocyanins. It also correlated positively with leaf summer chlorophyll content and dry matter content, and negatively with specific leaf area. Time of leaf senescence and anthocyanin contents correlated with soil pH and with canopy openness. We conclude that the importance of anthocyanins in protection of leaf processes during senescence depends on the time of senescence. Rather than prolonging the growing season by enabling a delayed senescence, autumn anthocyanins in red maple in Ontario are important when senescence happens early, possibly due to the higher irradiance and greater danger of oxidative damage early in the season. PMID:27135339

  2. Differentially phased leaf growth and movements in Arabidopsis depend on coordinated circadian and light regulation.

    PubMed

    Dornbusch, Tino; Michaud, Olivier; Xenarios, Ioannis; Fankhauser, Christian

    2014-10-01

    In contrast to vastly studied hypocotyl growth, little is known about diel regulation of leaf growth and its coordination with movements such as changes in leaf elevation angle (hyponasty). We developed a 3D live-leaf growth analysis system enabling simultaneous monitoring of growth and movements. Leaf growth is maximal several hours after dawn, requires light, and is regulated by daylength, suggesting coupling between growth and metabolism. We identify both blade and petiole positioning as important components of leaf movements in Arabidopsis thaliana and reveal a temporal delay between growth and movements. In hypocotyls, the combination of circadian expression of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 and their light-regulated protein stability drives rhythmic hypocotyl elongation with peak growth at dawn. We find that PIF4 and PIF5 are not essential to sustain rhythmic leaf growth but influence their amplitude. Furthermore, EARLY FLOWERING3, a member of the evening complex (EC), is required to maintain the correct phase between growth and movement. Our study shows that the mechanisms underlying rhythmic hypocotyl and leaf growth differ. Moreover, we reveal the temporal relationship between leaf elongation and movements and demonstrate the importance of the EC for the coordination of these phenotypic traits. PMID:25281688

  3. A Role for APETALA1/FRUITFULL Transcription Factors in Tomato Leaf Development[C][W

    PubMed Central

    Burko, Yogev; Shleizer-Burko, Sharona; Yanai, Osnat; Shwartz, Ido; Zelnik, Iris Daphne; Jacob-Hirsch, Jasmine; Kela, Itai; Eshed-Williams, Leor; Ori, Naomi

    2013-01-01

    Flexible maturation rates underlie part of the diversity of leaf shape, and tomato (Solanum lycopersicum) leaves are compound due to prolonged organogenic activity of the leaf margin. The CINCINNATA -TEOSINTE BRANCHED1, CYCLOIDEA, PCF (CIN-TCP) transcription factor LANCEOLATE (LA) restricts this organogenic activity and promotes maturation. Here, we show that tomato APETALA1/FRUITFULL (AP1/FUL) MADS box genes are involved in tomato leaf development and are repressed by LA. AP1/FUL expression is correlated negatively with LA activity and positively with the organogenic activity of the leaf margin. LA binds to the promoters of the AP1/FUL genes MBP20 and TM4. Overexpression of MBP20 suppressed the simple-leaf phenotype resulting from upregulation of LA activity or from downregulation of class I knotted like homeobox (KNOXI) activity. Overexpression of a dominant-negative form of MBP20 led to leaf simplification and partly suppressed the increased leaf complexity of plants with reduced LA activity or increased KNOXI activity. Tomato plants overexpressing miR319, a negative regulator of several CIN-TCP genes including LA, flower with fewer leaves via an SFT-dependent pathway, suggesting that miR319-sensitive CIN-TCPs delay flowering in tomato. These results identify a role for AP1/FUL genes in vegetative development and show that leaf and plant maturation are regulated via partially independent mechanisms. PMID:23771895

  4. 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

  5. Leaf Relative Water Content Estimated from Leaf Reflectance and Transmittance

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

    2016-01-01

    Remotely sensing the water status of plants and the water content of canopies remain long term goals of remote sensing research. In the research we report here, we used optical polarization techniques to monitor the light reflected from the leaf interior, R, as well as the leaf transmittance, T, as the relative water content (RWC) of corn (Zea mays) leaves decreased. Our results show that R and T both change nonlinearly. The result show that the nonlinearities cancel in the ratio R/T, which appears linearly related to RWC for RWC less than 90%. The results suggest that potentially leaf water status and perhaps even canopy water status could be monitored starting from leaf and canopy optical measurements.

  6. Regulation of Compound Leaf Development

    PubMed Central

    Wang, Yuan; Chen, Rujin

    2013-01-01

    Leaf morphology is one of the most variable, yet inheritable, traits in the plant kingdom. How plants develop a variety of forms and shapes is a major biological question. Here, we discuss some recent progress in understanding the development of compound or dissected leaves in model species, such as tomato (Solanum lycopersicum), Cardamine hirsuta and Medicago truncatula, with an emphasis on recent discoveries in legumes. We also discuss progress in gene regulations and hormonal actions in compound leaf development. These studies facilitate our understanding of the underlying regulatory mechanisms and put forward a prospective in compound leaf studies. PMID:27135488

  7. Delayed emergence after anesthesia.

    PubMed

    Tzabazis, Alexander; Miller, Christopher; Dobrow, Marc F; Zheng, Karl; Brock-Utne, John G

    2015-06-01

    In most instances, delayed emergence from anesthesia is attributed to residual anesthetic or analgesic medications. However, delayed emergence can be secondary to unusual causes and present diagnostic dilemmas. Data from clinical studies is scarce and most available published material is comprised of case reports. In this review, we summarize and discuss less common and difficult to diagnose reasons for delayed emergence and present cases from our own experience or reference published case reports/case series. The goal is to draw attention to less common reasons for delayed emergence, identify patient populations that are potentially at risk and to help anesthesiologists identifying a possible cause why their patient is slow to wake up. PMID:25912729

  8. Time delay spectrum conditioner

    DOEpatents

    Greiner, Norman R.

    1980-01-01

    A device for delaying specified frequencies of a multiple frequency laser beam. The device separates the multiple frequency beam into a series of spatially separated single frequency beams. The propagation distance of the single frequency beam is subsequently altered to provide the desired delay for each specific frequency. Focusing reflectors can be utilized to provide a simple but nonadjustable system or, flat reflectors with collimating and focusing optics can be utilized to provide an adjustable system.

  9. Delayed voice communication

    NASA Astrophysics Data System (ADS)

    Love, Stanley G.; Reagan, Marcum L.

    2013-10-01

    We present results from simulated deep-space exploration missions that investigated voice communication with significant time delays. The simulations identified many challenges: confusion of sequence, blocked calls, wasted crew time, impaired ability to provide relevant information to the other party, losing track of which messages have reached the other party, weakened rapport between crew and ground, slow response to rapidly changing situations, and reduced situational awareness. These challenges were met in part with additional training; greater attention and foresight; longer, less frequent transmissions; meticulous recordkeeping and timekeeping; and specific alerting and acknowledging calls. Several simulations used both delayed voice and text messaging. Text messaging provided a valuable record of transmissions and allowed messages to be targeted to subsets of the flight and ground crew, but it was a poor choice for high-workload operators such as vehicle drivers and spacewalkers. Even with the foregoing countermeasures, delayed voice communication is difficult. Additional aids such as automatic delay timers and voice-to-text transcription would help. Tests comparing delays of 50 and 300 s unexpectedly revealed that communicating with the shorter delay was just as challenging as with the longer one.

  10. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface...

  11. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface...

  12. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS...

  13. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS...

  14. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS...

  15. Near infrared leaf reflectance modeling

    NASA Technical Reports Server (NTRS)

    Parrish, J. B.

    1985-01-01

    Near infrared leaf reflectance modeling using Fresnel's equation (Kumar and Silva, 1973) and Snell's Law successfully approximated the spectral curve for a 0.25-mm turgid oak leaf lying on a Halon background. Calculations were made for ten interfaces, air-wax, wax-cellulose, cellulose-water, cellulose-air, air-water, and their inverses. A water path of 0.5 mm yielded acceptable results, and it was found that assignment of more weight to those interfaces involving air versus water or cellulose, and less to those involving wax, decreased the standard deviation of the error for all wavelengths. Data suggest that the air-cell interface is not the only important contributor to the overall reflectance of a leaf. Results also argue against the assertion that the near infrared plateau is a function of cell structure within the leaf.

  16. 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 (ΔΨstem-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 ΔΨstem-leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO₂ assimilation rate over the diurnal course of evaporative demand. PMID:25547915

  17. 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 (ΔΨstem–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 ΔΨstem–leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO2 assimilation rate over the diurnal course of evaporative demand. PMID:25547915

  18. Temporal disparity in leaf chlorophyll content and leaf area index across a growing season in a temperate deciduous forest

    NASA Astrophysics Data System (ADS)

    Croft, H.; Chen, J. M.; Zhang, Y.

    2014-12-01

    Spatial and temporal variations in canopy structure and leaf biochemistry have considerable influence on fluxes of CO2, water and energy and nutrient cycling in vegetation. Two vegetation indices (VI), NDVI and Macc01, were used to model the spatio-temporal variability of broadleaf chlorophyll content and leaf area index (LAI) across a growing season. Ground data including LAI, hyperspectral leaf reflectance factors (400-2500 nm) and leaf chlorophyll content were measured across the growing season and satellite-derived canopy reflectance data was acquired for 33 dates at 1200 m spatial resolution. Key phenological information was extracted using the TIMESAT software. Results showed that LAI and chlorophyll start of season (SOS) dates were at day of year (DOY) 130 and 157 respectively, and total season duration varied by 57 days. The spatial variability of chlorophyll and LAI phenology was also analyzed at the landscape scale to investigate phenological patterns over a larger spatial extent. Whilst a degree of spatial variability existed, results showed that chlorophyll SOS lagged approximately 20-35 days behind LAI SOS, and the end of season (EOS) LAI dates were predominantly between 20 and 30 days later than chlorophyll EOS. The large temporal differences between VI-derived chlorophyll content and LAI has important implications for biogeochemical models using NDVI or LAI to represent the fraction of photosynthetically active radiation absorbed by a canopy, in neglecting to account for delays in chlorophyll production and thus photosynthetic capacity.

  19. Leaf development and phloem transport in Cucurbita pepo: Transition from import to export.

    PubMed

    Turgeon, R; Webb, J A

    1973-06-01

    The capacity of a growing leaf blade of Cucurbita pepo L. to import (14)C-labelled photoassimilate is lost in a basipetal direction. Import into the lamina tip stops when the blade is 10% expanded. Development of the leaf progresses linearly with time and the lamina base stops importing when the blade is 45% expanded. Export capacity also develops basipetally and follows immediately the loss of import capacity, at least in the lamina base. The small amount of material initially exported from the leaf tip is redistributed to the still-importing leaf base, delaying export from the lamina until the blade is 35% expanded. Loss of import capacity by the petiole is both basipetal and dorsoventral. The proximal, adaxial portion of the petiole is the last region to cease importing (14)C. Leaves of Beta vulgaris L. and Nicotiana tabacum L. also lose import capacity in a basipetal direction. PMID:24468909

  20. Downhole delay assembly for blasting with series delay

    DOEpatents

    Ricketts, Thomas E.

    1982-01-01

    A downhole delay assembly is provided which can be placed into a blasthole for initiation of explosive in the blasthole. The downhole delay assembly includes at least two detonating time delay devices in series in order to effect a time delay of longer than about 200 milliseconds in a round of explosions. The downhole delay assembly provides a protective housing to prevent detonation of explosive in the blasthole in response to the detonation of the first detonating time delay device. There is further provided a connection between the first and second time delay devices. The connection is responsive to the detonation of the first detonating time delay device and initiates the second detonating time delay device. A plurality of such downhole delay assemblies are placed downhole in unfragmented formation and are initiated simultaneously for providing a round of explosive expansions. The explosive expansions can be used to form an in situ oil shale retort containing a fragmented permeable mass of formation particles.

  1. The Vernier delay unit

    SciTech Connect

    Pierce, W.B.

    1985-02-01

    One of the most critical timing specifications for the SLC machine occurs at the injector and ejector magnets for the Damping Ring. It has been determined that the trigger pulses to the magnets must be controlled to 0.1 ns. The primary source for all trigger pulses for the SLC machine is the Programmable Delay Unit (PDU). The PDU generates a 67.2 ns wide pulse with delay increments of 8.7 ns. The gap between the required accuracy and that available from the PDU requires the design of a new module that is called the Vernier Delay Unit (VDU). This module accepts the 67.2 ns pulse from the PDU and is capable of increasing the delay in steps of 0.1 ns from 0 to 10.7 ns plus the minimum 9 ns delay. The module has two totally independent channels. The pulse input to the module is software selectable from either the auxiliary backplane or a front panel Lemo connector. The auxiliary backplane pulses are to be the 67 ns differential ECL pulses from the PDU. The front panel input is to be a NIM level (-0.7 V 50 termination).

  2. Functional relationships of leafing intensity to plant height, growth form and leaf habit

    NASA Astrophysics Data System (ADS)

    Yan, En-Rong; Milla, Rubén; Aarssen, Lonnie W.; Wang, Xi-Hua

    2012-05-01

    Leafing intensity, i.e. the number of leaves per unit of stem volume or mass, is a common developmental correlate of leaf size. However, the ecological significance and the functional implications of variation in leafing intensity, other than its relation to leaf size, are unknown. Here, we explore its relationships with plant height, growth form, leaf size, and leaf habit to test a series of corollaries derived from the leafing intensity premium hypothesis. Volume-based leafing intensities and plant heights were recorded for 109 woody species from the subtropical evergreen broadleaf forests of eastern China. In addition, we compiled leafing intensity data from published literature, and combined it with our data to form a 398 species dataset, to test for differences of leafing intensity between plant growth forms (i.e. herbaceous and woody) and leaf habits (i.e. deciduous and evergreens). Leafing intensity was negatively correlated with plant height and individual leaf mass. Volume-based leafing intensities were significantly higher in herbaceous species than in woody species, and also higher in deciduous than in evergreen woody species. In conclusion, leafing intensity relates strongly to plant height, growth form, leaf size, and leaf habit in directions generally in accordance to the leafing intensity premium hypothesis. These results can be interpreted in terms of the evolution of adaptive strategies involving response to herbivory, competitive ability for light and reproductive economy.

  3. How to pattern a leaf.

    PubMed

    Bolduc, N; O'Connor, D; Moon, J; Lewis, M; Hake, S

    2012-01-01

    Leaf development presents a tremendous resource for tackling the question of patterning in biology. Leaves can be simple or highly dissected. They may have elaborated parts such as the tendrils of a pea leaf or the rolled blade of a carnivorous pitcher plant. Despite the variation in size, shape, and function, all leaves initiate in the same manner: from the flanks of a meristem. The maize leaf is useful for analysis of patterning due to the wealth of mutants and the distinct tissues along the proximal distal axis. The blade is distal, the sheath is proximal, and the ligule forms at the blade/sheath boundary. Establishment of this boundary involves the transcription factors LIGULELESS1 and LIGULELESS2 and the kinase LIGULELESS NARROW. The meristem-specific protein KNOTTED1 (KN1) binds and modulates the lg2 gene. Given the localization of KN1 at the proximal end of the leaf from the time of inception, we hypothesize that KN1 has a role in establishing the very proximal end of the leaf, whereas an auxin maximum guides the growing distal tip. PMID:23174765

  4. Estimating Delays In ASIC's

    NASA Technical Reports Server (NTRS)

    Burke, Gary; Nesheiwat, Jeffrey; Su, Ling

    1994-01-01

    Verification is important aspect of process of designing application-specific integrated circuit (ASIC). Design must not only be functionally accurate, but must also maintain correct timing. IFA, Intelligent Front Annotation program, assists in verifying timing of ASIC early in design process. This program speeds design-and-verification cycle by estimating delays before layouts completed. Written in C language.

  5. Contingencies promote delay tolerance.

    PubMed

    Ghaemmaghami, Mahshid; Hanley, Gregory P; Jessel, Joshua

    2016-09-01

    The effectiveness of functional communication training as treatment for problem behavior depends on the extent to which treatment can be extended to typical environments that include unavoidable and unpredictable reinforcement delays. Time-based progressive delay (TBPD) often results in the loss of acquired communication responses and the resurgence of problem behavior, whereas contingency-based progressive delay (CBPD) appears to be effective for increasing tolerance for delayed reinforcement. No direct comparison of TBPD and CBPD has, however, been conducted. We used single-subject designs to compare the relative efficacy of TBPD and CBPD. Four individuals who engaged in problem behavior (e.g., aggression, vocal and motor disruptions, self-injury) participated. Results were consistent across all participants, and showed lower rates of problem behavior and collateral responses during CBPD than during TBPD. The generality of CBPD treatment effects, including optimal rates of communication and compliance with demands, was demonstrated across a small but heterogeneous group of participants, reinforcement contingencies, and contexts. PMID:27449401

  6. Delayed traumatic diaphragmatic hernia

    PubMed Central

    Lu, Jing; Wang, Bo; Che, Xiangming; Li, Xuqi; Qiu, Guanglin; He, Shicai; Fan, Lin

    2016-01-01

    Abstract Background: Traumatic diaphragmatic hernias (TDHs) are sometimes difficult to identify at an early stage and can consequently result in diagnostic delays with life-threatening outcomes. It is the aim of this case study to highlight the difficulties encountered with the earlier detection of traumatic diaphragmatic hernias. Methods: Clinical data of patients who received treatment for delayed traumatic diaphragmatic hernias in registers of the First Affiliated Hospital of Xi’an Jiaotong University from 1998 to 2014 were analyzed retrospectively. Results: Six patients were included in this study. Left hemidiaphragm was affected in all of them. Most of the patients had a history of traffic accident and 1 a stab-penetrating injury. The interval from injury to developing symptoms ranged from 2 to 11 years (median 5 years). The hernial contents included the stomach, omentum, small intestine, and colon. Diaphragmatic injury was missed in all of them during the initial managements. All patients received operations once the diagnosis of delayed TDH was confirmed, and no postoperative mortality was detected. Conclusions: Delayed TDHs are not common, but can lead to serious consequences once occurred. Early detection of diaphragmatic injuries is crucial. Surgeons should maintain a high suspicion for injuries of the diaphragm in cases with abdominal or lower chest traumas, especially in the initial surgical explorations. We emphasize the need for radiographical follow-up to detect diaphragmatic injuries at an earlier stage. PMID:27512848

  7. Interferometric Propagation Delay

    NASA Technical Reports Server (NTRS)

    Goldstein, Richard

    1999-01-01

    Radar interferometry based on (near) exact repeat passes has lately been used by many groups of scientists, worldwide, to achieve state of the art measurements of topography, glacier and ice stream motion, earthquake displacements, oil field subsidence, lava flows, crop-induced surface decorrelation, and other effects. Variations of tropospheric and ionospheric propagation delays limit the accuracy of all such measurements. We are investigating the extent of this limitation, using data from the Shuttle radar flight, SIR-C, which is sensitive to the troposphere, and the Earth Resources Satellites, ERS-1/2, which are sensitive to both the troposphere and the ionosphere. We are presently gathering statistics of the delay variations over selected, diverse areas to determine the best accuracy possible for repeat track interferometry. The phases of an interferogram depend on both the topography of the scene and variations in propagation delay. The delay variations can be caused by movement of elements in the scene, by changes in tropospheric water vapor and by changes of the charge concentrations in the ionosphere. We plan to separate these causes by using the data from a third satellite visit (three-pass interferometry). The figure gives the geometry of the three-pass observations. The page of the figure is taken to be perpendicular to the spacecraft orbits. The three observational locations are marked on the figure, giving baselines B-12 and B-13, separated by the angle alpha. These parameters are almost constant over the whole scene. However, each pixel has an individual look angle, theta, which is related to the topography, rho is the slant range. A possible spurious time delay is shown. Additional information is contained in the original.

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

    SciTech Connect

    Potter, J.R. )

    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.

  9. GROWTH REGULATING FACTOR5 Stimulates Arabidopsis Chloroplast Division, Photosynthesis, and Leaf Longevity1[OPEN

    PubMed Central

    Vercruyssen, Liesbeth; Tognetti, Vanesa B.; Gonzalez, Nathalie; Van Dingenen, Judith; De Milde, Liesbeth; Bielach, Agnieszka; De Rycke, Riet; Van Breusegem, Frank; Inzé, Dirk

    2015-01-01

    Arabidopsis (Arabidopsis thaliana) leaf development relies on subsequent phases of cell proliferation and cell expansion. During the proliferation phase, chloroplasts need to divide extensively, and during the transition from cell proliferation to expansion, they differentiate into photosynthetically active chloroplasts, providing the plant with energy. The transcription factor GROWTH REGULATING FACTOR5 (GRF5) promotes the duration of the cell proliferation period during leaf development. Here, it is shown that GRF5 also stimulates chloroplast division, resulting in a higher chloroplast number per cell with a concomitant increase in chlorophyll levels in 35S:GRF5 leaves, which can sustain higher rates of photosynthesis. Moreover, 35S:GRF5 plants show delayed leaf senescence and are more tolerant for growth on nitrogen-depleted medium. Cytokinins also stimulate leaf growth in part by extending the cell proliferation phase, simultaneously delaying the onset of the cell expansion phase. In addition, cytokinins are known to be involved in chloroplast development, nitrogen signaling, and senescence. Evidence is provided that GRF5 and cytokinins synergistically enhance cell division and chlorophyll retention after dark-induced senescence, which suggests that they also cooperate to stimulate chloroplast division and nitrogen assimilation. Taken together with the increased leaf size, ectopic expression of GRF5 has great potential to improve plant productivity. PMID:25604530

  10. 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 (ΔT), the latter to the transpiration rate. We present field measurements of ΔT 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 (ω) 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 ΔT) 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

  11. Leaf litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests

    PubMed Central

    Bothwell, Lori D.; Giardina, Christian P.; Litton, Creighton M.

    2014-01-01

    Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivity of leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical montane wet forests where the warming trend may be amplified compared to tropical wet forests at lower elevations. We quantified leaf litter decomposition rates along a highly constrained 5.2 °C mean annual temperature (MAT) gradient in tropical montane wet forests on the Island of Hawaii. Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release. Leaf litter decomposition rates were a positive linear function of MAT, causing the residence time of leaf litter on the forest floor to decline by ∼31 days for each 1 °C increase in MAT. Our estimate of the Q10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5–2.5) across a broad range of ecosystems. The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site. The lack of net N immobilization during all three litter collection periods at all MAT plots indicates that N was not limiting to leaf litter decomposition, regardless of temperature. These results suggest that leaf litter decay in tropical montane wet forests may be more sensitive to rising MAT than in tropical lowland wet forests, and that increased rates of N release from decomposing litter could delay or prevent progressive N limitation to net primary productivity with climate warming. PMID:25493213

  12. Behavior of Leaf Meristems and Their Modification

    PubMed Central

    Ichihashi, Yasunori; Tsukaya, Hirokazu

    2015-01-01

    A major source of diversity in flowering plant form is the extensive variability of leaf shape and size. Leaf formation is initiated by recruitment of a handful of cells flanking the shoot apical meristem (SAM) to develop into a complex three-dimensional structure. Leaf organogenesis depends on activities of several distinct meristems that are established and spatiotemporally differentiated after the initiation of leaf primordia. Here, we review recent findings in the gene regulatory networks that orchestrate leaf meristem activities in a model plant Arabidopsis thaliana. We then discuss recent key studies investigating the natural variation in leaf morphology to understand how the gene regulatory networks modulate leaf meristems to yield a substantial diversity of leaf forms during the course of evolution. PMID:26648955

  13. [Acromegaly: reducing diagnostic delay].

    PubMed

    Giustina, Andrea

    2016-08-01

    Diagnostic delay of acromegaly is still very relevant (6-8 years on average) without substantial changes in last twenty years. Clinical impact of this diagnostic delay is significant: tumor growth (2/3 of the patients at diagnosis bear a pituitary macroadenoma), development of irreversible complications (arthropathy, sleep apnea) and in all increased mortality. Reasons for this delay are related to the disease itself (facial and acral changes are very slow and subtle) but also to medical unawareness. Simple tools based on a few sufficiently sensitive and specific signs and symptoms which can trigger the diagnostic suspect would be useful in clinical practice. Global evaluation during follow-up (tumor volume, signs and symptoms, complications, circulating levels of growth hormone and its peripheral mediator IGF-I) has become crucial for the therapeutic decision making. In this regard, tools like SAGIT are now under validation and are expected to improve management of acromegaly. In fact, in the last 30 years there has been a relevant growth of the medical options to treat acromegaly and in the near future there will be an expansion of the medical options. This will greatly help the needed personalization of treatment which necessarily should consider patient convenience and preference and control of complications such as diabetes mellitus. PMID:27571562

  14. Time-Delay Interferometry

    NASA Astrophysics Data System (ADS)

    Dhurandhar, Sanjeev V.; Tinto, Massimo

    2005-07-01

    Equal-arm interferometric detectors of gravitational radiation allow phase measurements many orders of magnitude below the intrinsic phase stability of the laser injecting light into their arms. This is because the noise in the laser light is common to both arms, experiencing exactly the same delay, and thus cancels when it is differenced at the photo detector. In this situation, much lower level secondary noises then set the overall performance. If, however, the two arms have different lengths (as will necessarily be the case with space-borne interferometers), the laser noise experiences different delays in the two arms and will hence not directly cancel at the detector. In order to solve this problem, a technique involving heterodyne interferometry with unequal arm lengths and independent phase-difference readouts has been proposed. It relies on properly time-shifting and linearly combining independent Doppler measurements, and for this reason it has been called Time-Delay Interferometry (TDI). This article provides an overview of the theory and mathematical foundations of TDI as it will be implemented by the forthcoming space-based interferometers such as the Laser Interferometer Space Antenna (LISA) mission. We have purposely left out from this first version of our "Living Review" article on TDI all the results of more practical and experimental nature, as well as all the aspects of TDI that the data analysts will need to account for when analyzing the LISA TDI data combinations. Our forthcoming "second edition" of this review paper will include these topics.

  15. 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...

  16. Analysis of Circadian Leaf Movements.

    PubMed

    Müller, Niels A; Jiménez-Gómez, José M

    2016-01-01

    The circadian clock is a molecular timekeeper that controls a wide variety of biological processes. In plants, clock outputs range from the molecular level, with rhythmic gene expression and metabolite content, to physiological processes such as stomatal conductance or leaf movements. Any of these outputs can be used as markers to monitor the state of the circadian clock. In the model plant Arabidopsis thaliana, much of the current knowledge about the clock has been gained from time course experiments profiling expression of endogenous genes or reporter constructs regulated by the circadian clock. Since these methods require labor-intensive sample preparation or transformation, monitoring leaf movements is an interesting alternative, especially in non-model species and for natural variation studies. Technological improvements both in digital photography and image analysis allow cheap and easy monitoring of circadian leaf movements. In this chapter we present a protocol that uses an autonomous point and shoot camera and free software to monitor circadian leaf movements in tomato. PMID:26867616

  17. 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 ...

  18. Contact rate modulates foraging efficiency in leaf cutting ants

    PubMed Central

    Bouchebti, S.; Ferrere, S.; Vittori, K.; Latil, G.; Dussutour, A.; Fourcassié, V.

    2015-01-01

    Lane segregation is rarely observed in animals that move in bidirectional flows. Consequently, these animals generally experience a high rate of head-on collisions during their journeys. Although these collisions have a cost (each collision induces a delay resulting in a decrease of individual speed), they could also have a benefit by promoting information transfer between individuals. Here we explore the impact of head-on collisions in leaf-cutting ants moving on foraging trails by artificially decreasing the rate of head-on collisions between individuals. We show that head-on collisions do not influence the rate of recruitment in these ants but do influence foraging efficiency, i.e. the proportion of ants returning to the nest with a leaf fragment. Surprisingly, both unladen and laden ants returning to the nest participate in the modulation of foraging efficiency: foraging efficiency decreases when the rate of contacts with both nestbound laden or unladen ants decreases. These results suggest that outgoing ants are able to collect information from inbound ants even when these latter do not carry any leaf fragment and that this information can influence their foraging decisions when reaching the end of the trail. PMID:26686557

  19. Contact rate modulates foraging efficiency in leaf cutting ants.

    PubMed

    Bouchebti, S; Ferrere, S; Vittori, K; Latil, G; Dussutour, A; Fourcassié, V

    2015-01-01

    Lane segregation is rarely observed in animals that move in bidirectional flows. Consequently, these animals generally experience a high rate of head-on collisions during their journeys. Although these collisions have a cost (each collision induces a delay resulting in a decrease of individual speed), they could also have a benefit by promoting information transfer between individuals. Here we explore the impact of head-on collisions in leaf-cutting ants moving on foraging trails by artificially decreasing the rate of head-on collisions between individuals. We show that head-on collisions do not influence the rate of recruitment in these ants but do influence foraging efficiency, i.e. the proportion of ants returning to the nest with a leaf fragment. Surprisingly, both unladen and laden ants returning to the nest participate in the modulation of foraging efficiency: foraging efficiency decreases when the rate of contacts with both nestbound laden or unladen ants decreases. These results suggest that outgoing ants are able to collect information from inbound ants even when these latter do not carry any leaf fragment and that this information can influence their foraging decisions when reaching the end of the trail. PMID:26686557

  20. Cytokinin control of sequential leaf senescence in tobacco

    SciTech Connect

    Singh, S. ); Letham, D.S.; Parker, C.W. )

    1990-05-01

    Exogenously applied cytokinins (especially dihydrozeatin) retarded senescence of leaf disks, detached and intact leaves of tobacco. The cytokinin complex in tobacco leaves of various maturities was characterized by radioimmunoassay. Zeatin was the major base whereas zeatin riboside was identified as the main riboside in both young (green) and senescing leaves. The basal, senescing leaves had lower levels of both cytokinin bases and ribosides. Exogenous applications of dihydrozeatin and zeatin to detached tobacco leaves delayed leaf senescence and elevated cytokinin base levels. These differences in endogenous levels of active cytokins in senescent and non-senescent leaves may be involved in the regulation of sequential leaf senescence in tobacco. There was no appreciable difference in either translocation or metabolism of xylem supplied tritium-labelled dihydrozeatin riboside between upper green and lower senescing leaves. The apical, green leaves (and not the basal, yellowing leaves) exhibited incorporation of ({sup 14}C)adenine into zeatin. The differing cytokinin levels in leaves of various maturity levels may be due to difference in cytokinin biosynthetic capacity.

  1. Assessing delay discounting in mice

    PubMed Central

    Mitchell, Suzanne H.

    2014-01-01

    Delay discounting (also intertemporal choice or impulsive choice) is the process by which delayed outcomes, such as delayed food delivery, are valued less than the same outcomes delivered immediately or with a shorter delay. This process is of interest because many psychopathologies, including substance dependence, pathological gambling, attention deficit hyperactivity disorder and conduct disorder, are characterized by heightened levels of delay discounting. Some of these disorders are heritable, and data indicate that delay discounting also has a genetic component. To identify the genes underlying the delay discounting decision-making process and genetic correlates of heightened discounting, researchers have used mouse models. This unit describes a protocol for generating delay discounting behavior in mice and discusses analysis techniques for such behavior. PMID:24510779

  2. Tooth formation - delayed or absent

    MedlinePlus

    Delayed or absent tooth formation; Teeth - delayed or absent formation ... The age at which the tooth comes in varies. Most infants get their first tooth between 6 and 9 months, but it may be earlier or later. ...

  3. Delayed Speech or Language Development

    MedlinePlus

    ... to Know About Zika & Pregnancy Delayed Speech or Language Development KidsHealth > For Parents > Delayed Speech or Language ... your child is right on schedule. Normal Speech & Language Development It's important to discuss early speech and ...

  4. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by...

  5. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  6. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  7. 7 CFR 29.1030 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  8. 7 CFR 29.1030 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  9. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  10. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  11. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  12. 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... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  13. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  14. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  15. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  16. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  17. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  18. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  19. Tree branch angle: maximizing effective leaf area.

    PubMed

    Honda, H; Fisher, J B

    1978-02-24

    In a computer simulation of branching pattern and leaf cluster in Terminalia catappa, right and left branch angles were varied, and the effective leaf surface areas were calculated. Theoretical branch angles that result in maximum effective leaf area are close to the values observed in nature. PMID:17757590

  20. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture... Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS...

  1. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.3526 Section 29.3526...

  2. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.2529 Section 29.2529...

  3. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.6022 Section 29.6022...

  4. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.2277 Section 29.2277...

  5. Differentially Phased Leaf Growth and Movements in Arabidopsis Depend on Coordinated Circadian and Light Regulation[W

    PubMed Central

    Dornbusch, Tino; Michaud, Olivier; Xenarios, Ioannis; Fankhauser, Christian

    2014-01-01

    In contrast to vastly studied hypocotyl growth, little is known about diel regulation of leaf growth and its coordination with movements such as changes in leaf elevation angle (hyponasty). We developed a 3D live-leaf growth analysis system enabling simultaneous monitoring of growth and movements. Leaf growth is maximal several hours after dawn, requires light, and is regulated by daylength, suggesting coupling between growth and metabolism. We identify both blade and petiole positioning as important components of leaf movements in Arabidopsis thaliana and reveal a temporal delay between growth and movements. In hypocotyls, the combination of circadian expression of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 and their light-regulated protein stability drives rhythmic hypocotyl elongation with peak growth at dawn. We find that PIF4 and PIF5 are not essential to sustain rhythmic leaf growth but influence their amplitude. Furthermore, EARLY FLOWERING3, a member of the evening complex (EC), is required to maintain the correct phase between growth and movement. Our study shows that the mechanisms underlying rhythmic hypocotyl and leaf growth differ. Moreover, we reveal the temporal relationship between leaf elongation and movements and demonstrate the importance of the EC for the coordination of these phenotypic traits. PMID:25281688

  6. Comparison of half and full-leaf shape feature extraction for leaf classification

    NASA Astrophysics Data System (ADS)

    Sainin, Mohd Shamrie; Ahmad, Faudziah; Alfred, Rayner

    2016-08-01

    Shape is the main information for leaf feature that most of the current literatures in leaf identification utilize the whole leaf for feature extraction and to be used in the leaf identification process. In this paper, study of half-leaf features extraction for leaf identification is carried out and the results are compared with the results obtained from the leaf identification based on a full-leaf features extraction. Identification and classification is based on shape features that are represented as cosines and sinus angles. Six single classifiers obtained from WEKA and seven ensemble methods are used to compare their performance accuracies over this data. The classifiers were trained using 65 leaves in order to classify 5 different species of preliminary collection of Malaysian medicinal plants. The result shows that half-leaf features extraction can be used for leaf identification without decreasing the predictive accuracy.

  7. Inter-annual variation in the response of leaf-out onset to soil moisture increase in a teak plantation in northern Thailand.

    PubMed

    Yoshifuji, Natsuko; Igarashi, Yasunori; Tanaka, Nobuaki; Tanaka, Katsunori; Sato, Takanori; Tantasirin, Chatchai; Suzuki, Masakazu

    2014-11-01

    To understand the impact of inter-annual climate change on vegetation-atmosphere mass and energy exchanges, it has become necessary to explore changes in leaf-out onset in response to climatic fluctuations. We examined the response of leaf-out and transpiration onset dates to soil moisture in a teak plantation in northern Thailand based on a 12-year leaf area index and sap flow measurements. The date of leaf-out and transpiration onset varied between years by up to 40 days, and depended on the initial date when the relative extractable water in a soil layer of 0-0.6 m (Θ) was greater than 0.2 being consistent with our previous results. Our new finding is that the delay in leaf-out and transpiration onset relative to the initial date when Θ > 0.2 increases linearly as the initial date on which Θ > 0.2 becomes earlier. The delay spans about 20 days in years when Θ > 0.2 occurs in March (the late dry season)-much earlier than usual because of heavy pre-monsoon rainfalls-while there is little delay in years when Θ > 0.2 occurs in May. This delay indicates the influence of additional factors on leaf-out onset, which controls the delay in the response of leaf-out to soil moisture increase. The results increased our knowledge about the pattern and extent of the changes in leaf phenology that occur in response to the inter-annual climate variation in tropical regions, where, in particular, such research is needed. PMID:24469544

  8. Inter-annual variation in the response of leaf-out onset to soil moisture increase in a teak plantation in northern Thailand

    NASA Astrophysics Data System (ADS)

    Yoshifuji, Natsuko; Igarashi, Yasunori; Tanaka, Nobuaki; Tanaka, Katsunori; Sato, Takanori; Tantasirin, Chatchai; Suzuki, Masakazu

    2014-01-01

    To understand the impact of inter-annual climate change on vegetation-atmosphere mass and energy exchanges, it has become necessary to explore changes in leaf-out onset in response to climatic fluctuations. We examined the response of leaf-out and transpiration onset dates to soil moisture in a teak plantation in northern Thailand based on a 12-year leaf area index and sap flow measurements. The date of leaf-out and transpiration onset varied between years by up to 40 days, and depended on the initial date when the relative extractable water in a soil layer of 0-0.6 m (Θ) was greater than 0.2 being consistent with our previous results. Our new finding is that the delay in leaf-out and transpiration onset relative to the initial date when Θ > 0.2 increases linearly as the initial date on which Θ > 0.2 becomes earlier. The delay spans about 20 days in years when Θ > 0.2 occurs in March (the late dry season)—much earlier than usual because of heavy pre-monsoon rainfalls—while there is little delay in years when Θ > 0.2 occurs in May. This delay indicates the influence of additional factors on leaf-out onset, which controls the delay in the response of leaf-out to soil moisture increase. The results increased our knowledge about the pattern and extent of the changes in leaf phenology that occur in response to the inter-annual climate variation in tropical regions, where, in particular, such research is needed.

  9. Responses of leafing phenology and photosynthesis to soil warming in forest-floor plants

    NASA Astrophysics Data System (ADS)

    Ishioka, Ryo; Muller, Onno; Hiura, Tsutom; Kudo, Gaku

    2013-08-01

    Phenological and physiological responses of plants to climate change are key issues to understand the global change impact on ecosystems. To evaluate the species-specific responses, a soil-warming experiment was conducted for seven understory species having various leaf habits in a deciduous forest, northern Japan; one evergreen shrub, one semi-evergreen fern, one summer-deciduous shrub, and four summer-green herbs. Soil temperature in the warming plots was electrically maintained 5 °C higher than control plots. Responses of leafing phenology highly varied among species: new leaf emergence of the evergreen shrub was delayed; senescence of overwintering leaves of the semi-evergreen fern was accelerated resulting in the shift to deciduousness; leaf shedding of the summer-deciduous shrub was accelerated. Among four summer-green species, only an earliest leaf-out species advanced growth initiation, but the period of growth season was not changed. Physiological responses to soil warming were also highly species-specific: the warming treatment increased the photosynthetic activity of the summer-deciduous shrub and one summer-green species, decreased that of the semi-evergreen fern, while other species did not show any changes in photosynthetic traits. Totally, the soil warming impacts on understory plants was apparent in spring. It was suggested that modification of snow conditions is important issue especially for plants with overwintering leaves. Responses of understory vegetation to climate change may highly vary depending on the composition of leaf habits in the cool-temperate forests.

  10. Altered Growth of Transgenic Tobacco Lacking Leaf Cytosolic Pyruvate Kinase1

    PubMed Central

    Knowles, Vicki L.; McHugh, Sylvia G.; Hu, Zhiyuan; Dennis, David T.; Miki, Brian L.; Plaxton, William C.

    1998-01-01

    Previously, we reported that transformation of tobacco (Nicotiana tabacum L.) with a vector containing a potato cytosolic pyruvate kinase (PKc) cDNA generated two plant lines specifically lacking leaf PKc (PKc−) as a result of co-suppression. PKc deficiency in these primary transformants did not appear to alter plant development, although root growth was not examined. Here we report a striking reduction in root growth of homozygous progeny of both PKc− lines throughout development under moderate (600 μE m−2 s−1) or low (100 μE m−2 s−1) light intensities. When both PKc− lines were cultivated under low light, shoot and flower development were also delayed and leaf indentations were apparent. Leaf PK activity in the transformants was significantly decreased at all time points examined, whereas root activities were unaffected. Polypeptides corresponding to PKc were undetectable on immunoblots of PKc− leaf extracts, except in 6-week-old low-light-grown PKc− plants, in which leaf PKc expression appeared to be greatly reduced. The metabolic implications of the kinetic characteristics of partially purified PKc from wild-type tobacco leaves are discussed. Overall, the results suggest that leaf PKc deficiency leads to a perturbation in source-sink relationships. PMID:9449835

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

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color...

  12. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color...

  13. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color...

  14. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color...

  15. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color...

  16. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... specifications, and tolerances C1L Choice Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth... injury tolerance. C2L Fine Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, oily... tolerance. C4L Fair Quality Light-brown Thin Leaf. Mature, thin, close leaf structure, rough, lean in...

  17. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... specifications, and tolerances C1L Choice Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth... injury tolerance. C2L Fine Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, oily... tolerance. C4L Fair Quality Light-brown Thin Leaf. Mature, thin, close leaf structure, rough, lean in...

  18. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... specifications, and tolerances C1L Choice Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth... injury tolerance. C2L Fine Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, oily... tolerance. C4L Fair Quality Light-brown Thin Leaf. Mature, thin, close leaf structure, rough, lean in...

  19. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... specifications, and tolerances C1L Choice Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth... injury tolerance. C2L Fine Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, oily... tolerance. C4L Fair Quality Light-brown Thin Leaf. Mature, thin, close leaf structure, rough, lean in...

  20. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... tolerance. C4L Fair Quality Light-brown Thin Leaf. Mature, thin, close leaf structure, rough, lean in oil... tolerance. C5L Low Quality Light-brown Thin Leaf Underripe, thin, close leaf structure, rough, lean in oil... tolerance. C4F Fair Quality Medium-brown Thin Leaf. Mature, thin, close leaf structure, rough, lean in...

  1. Programmable Differential Delay Circuit With Fine Delay Adjustment

    DOEpatents

    DeRyckere, John F.; Jenkins, Philip Nord; Cornett, Frank Nolan

    2002-07-09

    Circuitry that provides additional delay to early arriving signals such that all data signals arrive at a receiving latch with same path delay. The delay of a forwarded clock reference is also controlled such that the capturing clock edge will be optimally positioned near quadrature (depending on latch setup/hold requirements). The circuitry continuously adapts to data and clock path delay changes and digital filtering of phase measurements reduce errors brought on by jittering data edges. The circuitry utilizes only the minimum amount of delay necessary to achieve objective thereby limiting any unintended jitter. Particularly, this programmable differential delay circuit with fine delay adjustment is designed to allow the skew between ASICS to be minimized. This includes skew between data bits, between data bits and clocks as well as minimizing the overall skew in a channel between ASICS.

  2. The LEA protein, ABR, is regulated by ABI5 and involved in dark-induced leaf senescence in Arabidopsis thaliana.

    PubMed

    Su, Mengying; Huang, Gan; Zhang, Qing; Wang, Xiao; Li, Chunxin; Tao, Yujin; Zhang, Shengchun; Lai, Jianbin; Yang, Chengwei; Wang, Yaqin

    2016-06-01

    The phytohormone abscisic acid (ABA) modulates plant growth and developmental processes such as leaf senescence. In this study, we investigated the role of the Arabidopsis late embryogenesis abundant (LEA) protein ABR (ABA-response protein) in delaying dark-induced leaf senescence. The ABR gene was up-regulated by treatment with ABA, NaCl and mannitol, as well as by light deprivation. In the dark, abr mutant plants displayed a premature leaf senescence phenotype, and various senescence-associated indicators, such as an increase in chlorophyll degradation and membrane leakiness, were enhanced, whereas 35S:ABR/abr transgenic lines showed a marked delay in dark-induced leaf senescence phenotypes. In vitro and in vivo assays showed that ABI5 bind to the ABR promoter, indicating that ABI5 directly regulates the expression of ABR. The disruption of ABI5 function in abr abi5-1 plants abolished the senescence-accelerating phenotype of the abr mutant, demonstrating that ABI5 is epistatic to ABR. In summary, these results highlight the important role that ABR, which is negatively regulated by ABI5, plays in delaying dark-induced leaf senescence. PMID:27095403

  3. SPAD-based leaf nitrogen estimation is impacted by environmental factors and crop leaf characteristics

    PubMed Central

    Xiong, Dongliang; Chen, Jia; Yu, Tingting; Gao, Wanlin; Ling, Xiaoxia; Li, Yong; Peng, Shaobing; Huang, Jianliang

    2015-01-01

    Chlorophyll meters are widely used to guide nitrogen (N) management by monitoring leaf N status in agricultural systems, but the effects of environmental factors and leaf characteristics on leaf N estimations are still unclear. In the present study, we estimated the relationships among SPAD readings, chlorophyll content and leaf N content per leaf area for seven species grown in multiple environments. There were similar relationships between SPAD readings and chlorophyll content per leaf area for the species groups, but the relationship between chlorophyll content and leaf N content per leaf area, and the relationship between SPAD readings and leaf N content per leaf area varied widely among the species groups. A significant impact of light-dependent chloroplast movement on SPAD readings was observed under low leaf N supplementation in both rice and soybean but not under high N supplementation. Furthermore, the allocation of leaf N to chlorophyll was strongly influenced by short-term changes in growth light. We demonstrate that the relationship between SPAD readings and leaf N content per leaf area is profoundly affected by environmental factors and leaf features of crop species, which should be accounted for when using a chlorophyll meter to guide N management in agricultural systems. PMID:26303807

  4. Leaf physiognomy and climate: A multivariate analysis

    NASA Astrophysics Data System (ADS)

    Davis, J. M.; Taylor, S. E.

    1980-11-01

    Research has demonstrated that leaf physiognomy is representative of the local or microclimate conditions under which plants grow. The physiognomy of leaf samples from Oregon, Michigan, Missouri, Tennessee, and the Panama Canal Zone has been related to the microclimate using Walter diagrams and Thornthwaite water-budget data. A technique to aid paleoclimatologists in identifying the nature of the microclimate from leaf physiognomy utilizes statistical procedures to classify leaf samples into one of six microclimate regimes based on leaf physiognomy information available from fossilized samples.

  5. Adaptive Phase Delay Generator

    NASA Technical Reports Server (NTRS)

    Greer, Lawrence

    2013-01-01

    There are several experimental setups involving rotating machinery that require some form of synchronization. The adaptive phase delay generator (APDG) the Bencic-1000 is a flexible instrument that allows the user to generate pulses synchronized to the rising edge of a tachometer signal from any piece of rotating machinery. These synchronized pulses can vary by the delay angle, pulse width, number of pulses per period, number of skipped pulses, and total number of pulses. Due to the design of the pulse generator, any and all of these parameters can be changed independently, yielding an unparalleled level of versatility. There are two user interfaces to the APDG. The first is a LabVIEW program that has the advantage of displaying all of the pulse parameters and input signal data within one neatly organized window on the PC monitor. Furthermore, the LabVIEW interface plots the rpm of the two input signal channels in real time. The second user interface is a handheld portable device that goes anywhere a computer is not accessible. It consists of a liquid-crystal display and keypad, which enable the user to control the unit by scrolling through a host of command menus and parameter listings. The APDG combines all of the desired synchronization control into one unit. The experimenter can adjust the delay, pulse width, pulse count, number of skipped pulses, and produce a specified number of pulses per revolution. Each of these parameters can be changed independently, providing an unparalleled level of versatility when synchronizing hardware to a host of rotating machinery. The APDG allows experimenters to set up quickly and generate a host of synchronizing configurations using a simple user interface, which hopefully leads to faster results.

  6. Vehicle barrier with access delay

    DOEpatents

    Swahlan, David J; Wilke, Jason

    2013-09-03

    An access delay vehicle barrier for stopping unauthorized entry into secure areas by a vehicle ramming attack includes access delay features for preventing and/or delaying an adversary from defeating or compromising the barrier. A horizontally deployed barrier member can include an exterior steel casing, an interior steel reinforcing member and access delay members disposed within the casing and between the casing and the interior reinforcing member. Access delay members can include wooden structural lumber, concrete and/or polymeric members that in combination with the exterior casing and interior reinforcing member act cooperatively to impair an adversarial attach by thermal, mechanical and/or explosive tools.

  7. Leaf herbivory and nutrients increase nectar alkaloids.

    PubMed

    Adler, Lynn S; Wink, Michael; Distl, Melanie; Lentz, Amanda J

    2006-08-01

    Correlations between traits may constrain ecological and evolutionary responses to multispecies interactions. Many plants produce defensive compounds in nectar and leaves that could influence interactions with pollinators and herbivores, but the relationship between nectar and leaf defences is entirely unexplored. Correlations between leaf and nectar traits may be mediated by resources and prior damage. We determined the effect of nutrients and leaf herbivory by Manduca sexta on Nicotiana tabacum nectar and leaf alkaloids, floral traits and moth oviposition. We found a positive phenotypic correlation between nectar and leaf alkaloids. Herbivory induced alkaloids in nectar but not in leaves, while nutrients increased alkaloids in both tissues. Moths laid the most eggs on damaged, fertilized plants, suggesting a preference for high alkaloids. Induced nectar alkaloids via leaf herbivory indicate that species interactions involving leaf and floral tissues are linked and should not be treated as independent phenomena in plant ecology or evolution. PMID:16913940

  8. Plant development controls leaf area expansion in alfalfa plants competing for light

    PubMed Central

    Baldissera, Tiago Celso; Frak, Ela; Carvalho, Paulo Cesar de Faccio; Louarn, Gaëtan

    2014-01-01

    Background and Aims The growth of crops in a mixture is more variable and difficult to predict than that in pure stands. Light partitioning and crop leaf area expansion play prominent roles in explaining this variability. However, in many crops commonly grown in mixtures, including the forage species alfalfa, the sensitivity and relative importance of the physiological responses involved in the light modulation of leaf area expansion are still to be established. This study was designed to assess the relative sensitivity of primary shoot development, branching and individual leaf expansion in alfalfa in response to light availability. Methods Two experiments were carried out. The first studied isolated plants to assess the potential development of different shoot types and growth periods. The second consisted of manipulating the intensity of competition for light using a range of canopies in pure and mixed stands at two densities so as to evaluate the relative effects on shoot development, leaf growth, and plant and shoot demography. Key Results Shoot development in the absence of light competition was deterministic (constant phyllochrons of 32·5 °Cd and 48·2 °Cd for primary axes and branches, branching probability of 1, constant delay of 1·75 phyllochron before axillary bud burst) and identical irrespective of shoot type and growth/regrowth periods. During light competition experiments, changes in plant development explained most of the plant leaf area variations, with average leaf size contributing to a lesser extent. Branch development and the number of shoots per plant were the leaf area components most affected by light availability. Primary axis development and plant demography were only affected in situations of severe light competition. Conclusions Plant leaf area components differed with regard to their sensitivity to light competition. The potential shoot development model presented in this study could serve as a framework to integrate light responses

  9. 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

  10. 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

  11. Delayed rule following

    PubMed Central

    Schmitt, David R.

    2001-01-01

    Although the elements of a fully stated rule (discriminative stimulus [SD], some behavior, and a consequence) can occur nearly contemporaneously with the statement of the rule, there is often a delay between the rule statement and the SD. The effects of this delay on rule following have not been studied in behavior analysis, but they have been investigated in rule-like settings in the areas of prospective memory (remembering to do something in the future) and goal pursuit. Discriminative events for some behavior can be event based (a specific setting stimulus) or time based. The latter are more demanding with respect to intention following and show age-related deficits. Studies suggest that the specificity with which the components of a rule (termed intention) are stated has a substantial effect on intention following, with more detailed specifications increasing following. Reminders of an intention, too, are most effective when they refer specifically to both the behavior and its occasion. Covert review and written notes are two effective strategies for remembering everyday intentions, but people who use notes appear not to be able to switch quickly to covert review. By focusing on aspects of the setting and rule structure, research on prospective memory and goal pursuit expands the agenda for a more complete explanation of rule effects. PMID:22478363

  12. Leaf Senescence by Magnesium Deficiency

    PubMed Central

    Tanoi, Keitaro; Kobayashi, Natsuko I.

    2015-01-01

    Magnesium ions (Mg2+) are the second most abundant cations in living plant cells, and they are involved in various functions, including photosynthesis, enzyme catalysis, and nucleic acid synthesis. Low availability of Mg2+ in an agricultural field leads to a decrease in yield, which follows the appearance of Mg-deficient symptoms such as chlorosis, necrotic spots on the leaves, and droop. During the last decade, a variety of physiological and molecular responses to Mg2+ deficiency that potentially link to leaf senescence have been recognized, allowing us to reconsider the mechanisms of Mg2+ deficiency. This review focuses on the current knowledge about the physiological responses to Mg2+ deficiency including a decline in transpiration, accumulation of sugars and starch in source leaves, change in redox states, increased oxidative stress, metabolite alterations, and a decline in photosynthetic activity. In addition, we refer to the molecular responses that are thought to be related to leaf senescence. With these current data, we give an overview of leaf senescence induced by Mg deficiency. PMID:27135350

  13. Stability and delay sensitivity of neutral fractional-delay systems

    NASA Astrophysics Data System (ADS)

    Xu, Qi; Shi, Min; Wang, Zaihua

    2016-08-01

    This paper generalizes the stability test method via integral estimation for integer-order neutral time-delay systems to neutral fractional-delay systems. The key step in stability test is the calculation of the number of unstable characteristic roots that is described by a definite integral over an interval from zero to a sufficient large upper limit. Algorithms for correctly estimating the upper limits of the integral are given in two concise ways, parameter dependent or independent. A special feature of the proposed method is that it judges the stability of fractional-delay systems simply by using rough integral estimation. Meanwhile, the paper shows that for some neutral fractional-delay systems, the stability is extremely sensitive to the change of time delays. Examples are given for demonstrating the proposed method as well as the delay sensitivity.

  14. Stability and delay sensitivity of neutral fractional-delay systems.

    PubMed

    Xu, Qi; Shi, Min; Wang, Zaihua

    2016-08-01

    This paper generalizes the stability test method via integral estimation for integer-order neutral time-delay systems to neutral fractional-delay systems. The key step in stability test is the calculation of the number of unstable characteristic roots that is described by a definite integral over an interval from zero to a sufficient large upper limit. Algorithms for correctly estimating the upper limits of the integral are given in two concise ways, parameter dependent or independent. A special feature of the proposed method is that it judges the stability of fractional-delay systems simply by using rough integral estimation. Meanwhile, the paper shows that for some neutral fractional-delay systems, the stability is extremely sensitive to the change of time delays. Examples are given for demonstrating the proposed method as well as the delay sensitivity. PMID:27586618

  15. LeafJ: an ImageJ plugin for semi-automated leaf shape measurement.

    PubMed

    Maloof, Julin N; Nozue, Kazunari; Mumbach, Maxwell R; Palmer, Christine M

    2013-01-01

    High throughput phenotyping (phenomics) is a powerful tool for linking genes to their functions (see review and recent examples). 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 tools. 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). Among SAS responses, shade induced leaf petiole elongation and changes in blade area are particularly useful as indices. To date, leaf shape programs (e.g. SHAPE, LAMINA, LeafAnalyzer, LEAFPROCESSOR) 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 size. 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

  16. Soviet delays raise prices

    SciTech Connect

    Young, I.

    1992-01-15

    The breakup of the Soviet Union is causing massive disruptions to methanol exports. The changeover to a Commonwealth of independent States has created logistical problems which have led some shipments of Russian methanol to be cancelled and delayed other deliveries by up to two weeks. In recent years the Soviet Union has exported 700,000 m.t./year-900,000 m.t./year of methanol, mainly to Western Europe. The product is made at 750,000-m.t./year plants at Tomsk and Gubakha in Russia and transported by rail for shipment from the ports of Ventspils, Latvia, on the Baltic Sea and Yuzhnyy in Ukraine, on the Black Sea. The exports were handled by state export agency Soyuzagrochim, mainly under contract to West European traders and consumers in areas like Scandinavia and France.

  17. Delayed cure bismaleimide resins

    DOEpatents

    Adams, Johnnie E.; Jamieson, Donald R.

    1984-08-07

    Polybismaleimides prepared by delayed curing of bis-imides having the formula ##STR1## wherein R.sub.1 and R.sub.2 each independently is H, C.sub.1-4 -alkyl, C.sub.1-4 -alkoxy, Cl or Br, or R.sub.1 and R.sub.2 together form a fused 6-membered hydrocarbon aromatic ring, with the proviso that R.sub.1 and R.sub.2 are not t-butyl or t-butoxy; X is O, S or Se; n is 1-3; and the --(CH.sub.2).sub.n -- group, optionally, is substituted by 1-3 methyl groups or by fluorine.

  18. Do pH changes in the leaf apoplast contribute to rapid inhibition of leaf elongation rate by water stress? Comparison of stress responses induced by polyethylene glycol and down-regulation of root hydraulic conductivity.

    PubMed

    Ehlert, Christina; Plassard, Claude; Cookson, Sarah Jane; Tardieu, François; Simonneau, Thierry

    2011-08-01

    We have dissected the influences of apoplastic pH and cell turgor on short-term responses of leaf growth to plant water status, by using a combination of a double-barrelled pH-selective microelectrodes and a cell pressure probe. These techniques were used, together with continuous measurements of leaf elongation rate (LER), in the (hidden) elongating zone of the leaves of intact maize plants while exposing roots to various treatments. Polyethylene glycol (PEG) reduced water availability to roots, while acid load and anoxia decreased root hydraulic conductivity. During the first 30 min, acid load and anoxia induced moderate reductions in leaf growth and turgor, with no effect on leaf apoplastic pH. PEG stopped leaf growth, while turgor was only partially reduced. Rapid alkalinization of the apoplast, from pH 4.9 ± 0.3 to pH 5.8 ± 0.2 within 30 min, may have participated to this rapid growth reduction. After 60 min, leaf growth inhibition correlated well with turgor reduction across all treatments, supporting a growth limitation by hydraulics. We conclude that apoplastic alkalinization may transiently impair the control of leaf growth by cell turgor upon abrupt water stress, whereas direct hydraulic control of growth predominates under moderate conditions and after a 30-60 min delay following imposition of water stress. PMID:21477119

  19. Wheat Grain Filling Is Limited by Grain Filling Capacity rather than the Duration of Flag Leaf Photosynthesis: A Case Study Using NAM RNAi Plants

    PubMed Central

    Borrill, Philippa; Fahy, Brendan; Smith, Alison M.; Uauy, Cristobal

    2015-01-01

    It has been proposed that delayed leaf senescence can extend grain filling duration and thus increase yields in cereal crops. We found that wheat (Triticum aestivum) NAM RNAi plants with delayed senescence carried out 40% more flag leaf photosynthesis after anthesis than control plants, but had the same rate and duration of starch accumulation during grain filling and the same final grain weight. The additional photosynthate available in NAM RNAi plants was in part stored as fructans in the stems, whereas stem fructans were remobilised during grain filling in control plants. In both genotypes, activity of starch synthase was limiting for starch synthesis in the later stages of grain filling. We suggest that in order to realise the potential yield gains offered by delayed leaf senescence, this trait should be combined with increased grain filling capacity. PMID:26241955

  20. Leaf P increase outpaces leaf N in an Inner Mongolia grassland over 27 years.

    PubMed

    Mi, Zhaorong; Huang, Yuanyuan; Gan, Huijie; Zhou, Wenjia; Flynn, Dan F B; He, Jin-Sheng

    2015-01-01

    The dynamics of leaf nitrogen (N) and phosphorus (P) have been intensively explored in short-term experiments, but rarely at longer timescales. Here, we investigated leaf N : P stoichiometry over a 27-year interval in an Inner Mongolia grassland by comparing leaf N : P concentration of 2006 with that of 1979. Across 80 species, both leaf N and P increased, but the increase in leaf N lagged behind that of leaf P, leading to a significant decrease in the N : P ratio. These changes in leaf N : P stoichiometry varied among functional groups. For leaf N, grasses increased, woody species tended to increase, whereas forbs showed no change. Unlike leaf N, leaf P of grasses and forbs increased, whereas woody species showed no change. Such changes may reflect N deposition and P release induced by soil acidification over the past decades. The interannual effect of precipitation may somewhat have reduced the soil available N, leading to the more modest increase of leaf N than of leaf P. Thus, leaf N : P stoichiometry significantly responded to long-term environmental changes in this temperate steppe, but different functional groups responded differently. Our results indicate that conclusions of plant stoichiometry under short-term N fertilization should be treated with caution when extrapolating to longer timescales. PMID:25589490

  1. Modeling delay in genetic networks: From delay birth-death processes to delay stochastic differential equations

    PubMed Central

    Gupta, Chinmaya; López, José Manuel; Azencott, Robert; Bennett, Matthew R.; Josić, Krešimir; Ott, William

    2014-01-01

    Delay is an important and ubiquitous aspect of many biochemical processes. For example, delay plays a central role in the dynamics of genetic regulatory networks as it stems from the sequential assembly of first mRNA and then protein. Genetic regulatory networks are therefore frequently modeled as stochastic birth-death processes with delay. Here, we examine the relationship between delay birth-death processes and their appropriate approximating delay chemical Langevin equations. We prove a quantitative bound on the error between the pathwise realizations of these two processes. Our results hold for both fixed delay and distributed delay. Simulations demonstrate that the delay chemical Langevin approximation is accurate even at moderate system sizes. It captures dynamical features such as the oscillatory behavior in negative feedback circuits, cross-correlations between nodes in a network, and spatial and temporal information in two commonly studied motifs of metastability in biochemical systems. Overall, these results provide a foundation for using delay stochastic differential equations to approximate the dynamics of birth-death processes with delay. PMID:24880267

  2. Modeling delay in genetic networks: From delay birth-death processes to delay stochastic differential equations

    SciTech Connect

    Gupta, Chinmaya; López, José Manuel; Azencott, Robert; Ott, William; Bennett, Matthew R.; Josić, Krešimir

    2014-05-28

    Delay is an important and ubiquitous aspect of many biochemical processes. For example, delay plays a central role in the dynamics of genetic regulatory networks as it stems from the sequential assembly of first mRNA and then protein. Genetic regulatory networks are therefore frequently modeled as stochastic birth-death processes with delay. Here, we examine the relationship between delay birth-death processes and their appropriate approximating delay chemical Langevin equations. We prove a quantitative bound on the error between the pathwise realizations of these two processes. Our results hold for both fixed delay and distributed delay. Simulations demonstrate that the delay chemical Langevin approximation is accurate even at moderate system sizes. It captures dynamical features such as the oscillatory behavior in negative feedback circuits, cross-correlations between nodes in a network, and spatial and temporal information in two commonly studied motifs of metastability in biochemical systems. Overall, these results provide a foundation for using delay stochastic differential equations to approximate the dynamics of birth-death processes with delay.

  3. PRECISION TIME-DELAY CIRCUIT

    DOEpatents

    Creveling, R.

    1959-03-17

    A tine-delay circuit which produces a delay time in d. The circuit a capacitor, an te back resistance, connected serially with the anode of the diode going to ground. At the start of the time delay a negative stepfunction is applied to the series circuit and initiates a half-cycle transient oscillatory voltage terminated by a transient oscillatory voltage of substantially higher frequency. The output of the delay circuit is taken at the junction of the inductor and diode where a sudden voltage rise appears after the initiation of the higher frequency transient oscillations.

  4. Time Delay of CGM Sensors

    PubMed Central

    Schmelzeisen-Redeker, Günther; Schoemaker, Michael; Kirchsteiger, Harald; Freckmann, Guido; Heinemann, Lutz; del Re, Luigi

    2015-01-01

    Background: Continuous glucose monitoring (CGM) is a powerful tool to support the optimization of glucose control of patients with diabetes. However, CGM systems measure glucose in interstitial fluid but not in blood. Rapid changes in one compartment are not accompanied by similar changes in the other, but follow with some delay. Such time delays hamper detection of, for example, hypoglycemic events. Our aim is to discuss the causes and extent of time delays and approaches to compensate for these. Methods: CGM data were obtained in a clinical study with 37 patients with a prototype glucose sensor. The study was divided into 5 phases over 2 years. In all, 8 patients participated in 2 phases separated by 8 months. A total number of 108 CGM data sets including raw signals were used for data analysis and were processed by statistical methods to obtain estimates of the time delay. Results: Overall mean (SD) time delay of the raw signals with respect to blood glucose was 9.5 (3.7) min, median was 9 min (interquartile range 4 min). Analysis of time delays observed in the same patients separated by 8 months suggests a patient dependent delay. No significant correlation was observed between delay and anamnestic or anthropometric data. The use of a prediction algorithm reduced the delay by 4 minutes on average. Conclusions: Prediction algorithms should be used to provide real-time CGM readings more consistent with simultaneous measurements by SMBG. Patient specificity may play an important role in improving prediction quality. PMID:26243773

  5. Integration and scaling of UV-B radiation effects on plants: from DNA to leaf

    PubMed Central

    Suchar, Vasile Alexandru; Robberecht, Ronald

    2015-01-01

    A process-based model integrating the effects of UV-B radiation through epidermis, cellular DNA, and its consequences to the leaf expansion was developed from key parameters in the published literature. Enhanced UV-B radiation-induced DNA damage significantly delayed cell division, resulting in significant reductions in leaf growth and development. Ambient UV-B radiation-induced DNA damage significantly reduced the leaf growth of species with high relative epidermal absorbance at longer wavelengths and average/low pyrimidine cyclobutane dimers (CPD) photorepair rates. Leaf expansion was highly dependent on the number of CPD present in the DNA, as a result of UV-B radiation dose, quantitative and qualitative absorptive properties of epidermal pigments, and repair mechanisms. Formation of pyrimidine-pyrimidone (6-4) photoproducts (6-4PP) has no effect on the leaf expansion. Repair mechanisms could not solely prevent the UV-B radiation interference with the cell division. Avoidance or effective shielding by increased or modified qualitative epidermal absorptance was required. Sustained increased UV-B radiation levels are more detrimental than short, high doses of UV-B radiation. The combination of low temperature and increased UV-B radiation was more significant in the level of UV-B radiation-induced damage than UV-B radiation alone. Slow-growing leaves were more affected by increased UV-B radiation than fast-growing leaves. PMID:26257869

  6. Anticonvulsant effect of Persea americana Mill (Lauraceae) (Avocado) leaf aqueous extract in mice.

    PubMed

    Ojewole, John A O; Amabeoku, George J

    2006-08-01

    Various morphological parts of Persea americana Mill (Lauraceae) (avocado) are widely used in African traditional medicines for the treatment, management and/or control of a variety of human ailments, including childhood convulsions and epilepsy. This study examined the anticonvulsant effect of the plant's leaf aqueous extract (PAE, 50-800 mg/kg i.p.) against pentylenetetrazole (PTZ)-, picrotoxin (PCT)- and bicuculline (BCL)-induced seizures in mice. Phenobarbitone and diazepam were used as reference anticonvulsant drugs for comparison. Like the reference anticonvulsant agents used, Persea americana leaf aqueous extract (PAE, 100-800 mg/kg i.p.) significantly (p < 0.05-0.001) delayed the onset of, and antagonized, pentylenetetrazole (PTZ)-induced seizures. The plant's leaf extract (PAE, 100-800 mg/kg i.p.) also profoundly antagonized picrotoxin (PCT)-induced seizures, but only weakly antagonized bicuculline (BCL)-induced seizures. Although the data obtained in the present study do not provide conclusive evidence, it would appear that 'avocado' leaf aqueous extract (PAE) produces its anticonvulsant effect by enhancing GABAergic neurotransmission and/or action in the brain. The findings of this study indicate that Persea americana leaf aqueous extract possesses an anticonvulsant property, and thus lends pharmacological credence to the suggested ethnomedical uses of the plant in the management of childhood convulsions and epilepsy. PMID:16775810

  7. Integration and scaling of UV-B radiation effects on plants: from DNA to leaf.

    PubMed

    Suchar, Vasile Alexandru; Robberecht, Ronald

    2015-07-01

    A process-based model integrating the effects of UV-B radiation through epidermis, cellular DNA, and its consequences to the leaf expansion was developed from key parameters in the published literature. Enhanced UV-B radiation-induced DNA damage significantly delayed cell division, resulting in significant reductions in leaf growth and development. Ambient UV-B radiation-induced DNA damage significantly reduced the leaf growth of species with high relative epidermal absorbance at longer wavelengths and average/low pyrimidine cyclobutane dimers (CPD) photorepair rates. Leaf expansion was highly dependent on the number of CPD present in the DNA, as a result of UV-B radiation dose, quantitative and qualitative absorptive properties of epidermal pigments, and repair mechanisms. Formation of pyrimidine-pyrimidone (6-4) photoproducts (6-4PP) has no effect on the leaf expansion. Repair mechanisms could not solely prevent the UV-B radiation interference with the cell division. Avoidance or effective shielding by increased or modified qualitative epidermal absorptance was required. Sustained increased UV-B radiation levels are more detrimental than short, high doses of UV-B radiation. The combination of low temperature and increased UV-B radiation was more significant in the level of UV-B radiation-induced damage than UV-B radiation alone. Slow-growing leaves were more affected by increased UV-B radiation than fast-growing leaves. PMID:26257869

  8. Leaf Shape Recognition using Centroid Contour Distance

    NASA Astrophysics Data System (ADS)

    Hasim, Abdurrasyid; Herdiyeni, Yeni; Douady, Stephane

    2016-01-01

    This research recognizes the leaf shape using Centroid Contour Distance (CCD) as shape descriptor. CCD is an algorithm of shape representation contour-based approach which only exploits boundary information. CCD calculates the distance between the midpoint and the points on the edge corresponding to interval angle. Leaf shapes that included in this study are ellips, cordate, ovate, and lanceolate. We analyzed 200 leaf images of tropical plant. Each class consists of 50 images. The best accuracy is obtained by 96.67%. We used Probabilistic Neural Network to classify the leaf shape. Experimental results demonstrated the effectiveness of the proposed approach for shape recognition with high accuracy.

  9. 7 CFR 30.2 - Leaf tobacco.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... stemming, sweating or fermenting, and conditioning are not regarded as manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed...

  10. Classification and quantification of leaf curvature

    PubMed Central

    Liu, Zhongyuan; Jia, Liguo; Mao, Yanfei; He, Yuke

    2010-01-01

    Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields. PMID:20400533