Expression of Arabidopsis Hexokinase in Citrus Guard Cells Controls Stomatal Aperture and Reduces Transpiration.

PubMed

Lugassi, Nitsan; Kelly, Gilor; Fidel, Lena; Yaniv, Yossi; Attia, Ziv; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Raveh, Eran; Carmi, Nir; Granot, David

2015-01-01

Hexokinase (HXK) is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1) under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species.

Expression of Arabidopsis Hexokinase in Citrus Guard Cells Controls Stomatal Aperture and Reduces Transpiration

PubMed Central

Lugassi, Nitsan; Kelly, Gilor; Fidel, Lena; Yaniv, Yossi; Attia, Ziv; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Raveh, Eran; Carmi, Nir; Granot, David

2015-01-01

Hexokinase (HXK) is a sugar-phosphorylating enzyme involved in sugar-sensing. It has recently been shown that HXK in guard cells mediates stomatal closure and coordinates photosynthesis with transpiration in the annual species tomato and Arabidopsis. To examine the role of HXK in the control of the stomatal movement of perennial plants, we generated citrus plants that express Arabidopsis HXK1 (AtHXK1) under KST1, a guard cell-specific promoter. The expression of KST1 in the guard cells of citrus plants has been verified using GFP as a reporter gene. The expression of AtHXK1 in the guard cells of citrus reduced stomatal conductance and transpiration with no negative effect on the rate of photosynthesis, leading to increased water-use efficiency. The effects of light intensity and humidity on stomatal behavior were examined in rooted leaves of the citrus plants. The optimal intensity of photosynthetically active radiation and lower humidity enhanced stomatal closure of AtHXK1-expressing leaves, supporting the role of sugar in the regulation of citrus stomata. These results suggest that HXK coordinates photosynthesis and transpiration and stimulates stomatal closure not only in annual species, but also in perennial species. PMID:26734024

Phytomelatonin receptor PMTR1-mediated signaling regulates stomatal closure in Arabidopsis thaliana.

PubMed

Wei, Jian; Li, Dong-Xu; Zhang, Jia-Rong; Shan, Chi; Rengel, Zed; Song, Zhong-Bang; Chen, Qi

2018-04-27

Melatonin has been detected in plants in 1995; however, the function and signaling pathway of this putative phytohormone are largely undetermined due to a lack of knowledge about its receptor. Here, we discovered the first phytomelatonin receptor (CAND2/PMTR1) in Arabidopsis thaliana and found that melatonin governs the receptor-dependent stomatal closure. The application of melatonin induced stomatal closure through the heterotrimeric G protein α subunit-regulated H 2 O 2 and Ca 2+ signals. The Arabidopsis mutant lines lacking AtCand2 that encodes a candidate G protein-coupled receptor were insensitive to melatonin-induced stomatal closure. Accordingly, the melatonin-induced H 2 O 2 production and Ca 2+ influx were completely abolished in cand2. CAND2 is a membrane protein that interacts with GPA1 and the expression of AtCand2 was tightly regulated by melatonin in various organs and guard cells. CAND2 showed saturable and specific 125 I-melatonin binding, with apparent K d (dissociation constant) of 0.73 ± 0.10 nmol/L (r 2  = .99), demonstrating this protein is a phytomelatonin receptor (PMTR1). Our results suggest that the phytomelatonin regulation of stomatal closure is dependent on its receptor CAND2/PMTR1-mediated H 2 O 2 and Ca 2+ signaling transduction cascade. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Regulation of Stomatal Immunity by Interdependent Functions of a Pathogen-Responsive MPK3/MPK6 Cascade and Abscisic Acid

PubMed Central

Zhang, Lawrence; Sun, Tiefeng

2017-01-01

Activation of mitogen-activated protein kinases (MAPKs) is one of the earliest responses after plants sense an invading pathogen. Here, we show that MPK3 and MPK6, two Arabidopsis thaliana pathogen-responsive MAPKs, and their upstream MAPK kinases, MKK4 and MKK5, are essential to both stomatal and apoplastic immunity. Loss of function of MPK3 and MPK6, or their upstream MKK4 and MKK5, abolishes pathogen/microbe-associated molecular pattern- and pathogen-induced stomatal closure. Gain-of-function activation of MPK3/MPK6 induces stomatal closure independently of abscisic acid (ABA) biosynthesis and signaling. In contrast, exogenously applied organic acids such as malate or citrate are able to reverse the stomatal closure induced by MPK3/MPK6 activation. Gene expression analysis and in situ enzyme activity staining revealed that malate metabolism increases in guard cells after activation of MPK3/MPK6 or inoculation of pathogen. In addition, pathogen-induced malate metabolism requires functional MKK4/MKK5 and MPK3/MPK6. We propose that the pathogen-responsive MPK3/MPK6 cascade and ABA are two essential signaling pathways that control, respectively, the organic acid metabolism and ion channels, two main branches of osmotic regulation in guard cells that function interdependently to control stomatal opening/closure. PMID:28254778

Does Size Matter? Atmospheric CO2 May Be a Stronger Driver of Stomatal Closing Rate Than Stomatal Size in Taxa That Diversified under Low CO2.

PubMed

Elliott-Kingston, Caroline; Haworth, Matthew; Yearsley, Jon M; Batke, Sven P; Lawson, Tracy; McElwain, Jennifer C

2016-01-01

One strategy for plants to optimize stomatal function is to open and close their stomata quickly in response to environmental signals. It is generally assumed that small stomata can alter aperture faster than large stomata. We tested the hypothesis that species with small stomata close faster than species with larger stomata in response to darkness by comparing rate of stomatal closure across an evolutionary range of species including ferns, cycads, conifers, and angiosperms under controlled ambient conditions (380 ppm CO2; 20.9% O2). The two species with fastest half-closure time and the two species with slowest half-closure time had large stomata while the remaining three species had small stomata, implying that closing rate was not correlated with stomatal size in these species. Neither was response time correlated with stomatal density, phylogeny, functional group, or life strategy. Our results suggest that past atmospheric CO2 concentration during time of taxa diversification may influence stomatal response time. We show that species which last diversified under low or declining atmospheric CO2 concentration close stomata faster than species that last diversified in a high CO2 world. Low atmospheric [CO2] during taxa diversification may have placed a selection pressure on plants to accelerate stomatal closing to maintain adequate internal CO2 and optimize water use efficiency.

Does Size Matter? Atmospheric CO2 May Be a Stronger Driver of Stomatal Closing Rate Than Stomatal Size in Taxa That Diversified under Low CO2

PubMed Central

Elliott-Kingston, Caroline; Haworth, Matthew; Yearsley, Jon M.; Batke, Sven P.; Lawson, Tracy; McElwain, Jennifer C.

2016-01-01

One strategy for plants to optimize stomatal function is to open and close their stomata quickly in response to environmental signals. It is generally assumed that small stomata can alter aperture faster than large stomata. We tested the hypothesis that species with small stomata close faster than species with larger stomata in response to darkness by comparing rate of stomatal closure across an evolutionary range of species including ferns, cycads, conifers, and angiosperms under controlled ambient conditions (380 ppm CO2; 20.9% O2). The two species with fastest half-closure time and the two species with slowest half-closure time had large stomata while the remaining three species had small stomata, implying that closing rate was not correlated with stomatal size in these species. Neither was response time correlated with stomatal density, phylogeny, functional group, or life strategy. Our results suggest that past atmospheric CO2 concentration during time of taxa diversification may influence stomatal response time. We show that species which last diversified under low or declining atmospheric CO2 concentration close stomata faster than species that last diversified in a high CO2 world. Low atmospheric [CO2] during taxa diversification may have placed a selection pressure on plants to accelerate stomatal closing to maintain adequate internal CO2 and optimize water use efficiency. PMID:27605929

Drought tolerance, xylem sap abscisic acid and stomatal conductance during soil drying: a comparison of young plants of four temperate deciduous angiosperms.

PubMed

Loewenstein, Nancy J.; Pallardy, Stephen G.

1998-07-01

Patterns of water relations, xylem sap abscisic acid (ABA) concentration ([ABA]) and stomatal aperture were compared in drought-sensitive black walnut (Juglans nigra L.) and black willow (Salix nigra Marsh.), less drought-sensitive sugar maple (Acer saccharum Marsh.) and drought-tolerant white oak (Quercus alba L.). Strong correlations among reduction in predawn water potential, increase in xylem sap [ABA] and stomatal closure were observed in all species. Stomatal response was more highly correlated with xylem [ABA] than with ABA flux. Xylem sap pH and ion concentrations appeared not to play a major role in the stomatal response of these species. Stomata were more sensitive to relative changes in [ABA] in drought-sensitive black walnut and black willow than in sugar maple and white oak. In the early stages of drought, increased [ABA] in the xylem sap of black walnut and black willow was probably of root origin and provided a signal to the shoot of the water status of the roots. In sugar maple and white oak, leaf water potential declined with the onset of stomatal closure, so that stomatal closure also may have occurred in response to the change in leaf water potential.

Functional analysis of cellulose and xyloglucan in the walls of stomatal guard cells of Arabidopsis thaliana

DOE PAGES

Rui, Yue; Anderson, Charles T.

2016-01-04

Here, stomatal guard cells are pairs of specialized epidermal cells that control water and CO 2 exchange between the plant and the environment. To fulfill the functions of stomatal opening and closure that are driven by changes in turgor pressure, guard cell walls must be both strong and flexible, but how the structure and dynamics of guard cell walls enable stomatal function remains poorly understood. To address this question, we applied cell biological and genetic analyses to investigate guard cell walls and their relationship to stomatal function in Arabidopsis ( Arabidopsis thaliana). Using live-cell spinning disk confocal microscopy, we measuredmore » the motility of cellulose synthase (CESA)-containing complexes labeled by green fluorescent protein (GFP)-CESA3 and observed a reduced proportion of GFP-CESA3 particles colocalizing with microtubules upon stomatal closure. Imaging cellulose organization in guard cells revealed a relatively uniform distribution of cellulose in the open state and a more fibrillar pattern in the closed state, indicating that cellulose microfibrils undergo dynamic reorganization during stomatal movements. In cesa3 je5 mutants defective in cellulose synthesis and xxt1 xxt2 mutants lacking the hemicellulose xyloglucan, stomatal apertures, changes in guard cell length, and cellulose reorganization were aberrant during fusicoccin-induced stomatal opening or abscisic acid-induced stomatal closure, indicating that sufficient cellulose and xyloglucan are required for normal guard cell dynamics. Together, these results provide new insights into how guard cell walls allow stomata to function as responsive mediators of gas exchange at the plant surface.« less

Functional Analysis of Cellulose and Xyloglucan in the Walls of Stomatal Guard Cells of Arabidopsis1[OPEN

PubMed Central

Rui, Yue; Anderson, Charles T.

2016-01-01

Stomatal guard cells are pairs of specialized epidermal cells that control water and CO2 exchange between the plant and the environment. To fulfill the functions of stomatal opening and closure that are driven by changes in turgor pressure, guard cell walls must be both strong and flexible, but how the structure and dynamics of guard cell walls enable stomatal function remains poorly understood. To address this question, we applied cell biological and genetic analyses to investigate guard cell walls and their relationship to stomatal function in Arabidopsis (Arabidopsis thaliana). Using live-cell spinning disk confocal microscopy, we measured the motility of cellulose synthase (CESA)-containing complexes labeled by green fluorescent protein (GFP)-CESA3 and observed a reduced proportion of GFP-CESA3 particles colocalizing with microtubules upon stomatal closure. Imaging cellulose organization in guard cells revealed a relatively uniform distribution of cellulose in the open state and a more fibrillar pattern in the closed state, indicating that cellulose microfibrils undergo dynamic reorganization during stomatal movements. In cesa3je5 mutants defective in cellulose synthesis and xxt1 xxt2 mutants lacking the hemicellulose xyloglucan, stomatal apertures, changes in guard cell length, and cellulose reorganization were aberrant during fusicoccin-induced stomatal opening or abscisic acid-induced stomatal closure, indicating that sufficient cellulose and xyloglucan are required for normal guard cell dynamics. Together, these results provide new insights into how guard cell walls allow stomata to function as responsive mediators of gas exchange at the plant surface. PMID:26729799

Closing Plant Stomata Requires a Homolog of an Aluminum-Activated Malate Transporter

PubMed Central

Sasaki, Takayuki; Mori, Izumi C.; Furuichi, Takuya; Munemasa, Shintaro; Toyooka, Kiminori; Matsuoka, Ken; Murata, Yoshiyuki; Yamamoto, Yoko

2010-01-01

Plant stomata limit both carbon dioxide uptake and water loss; hence, stomatal aperture is carefully set as the environment fluctuates. Aperture area is known to be regulated in part by ion transport, but few of the transporters have been characterized. Here we report that AtALMT12 (At4g17970), a homolog of the aluminum-activated malate transporter (ALMT) of wheat, is expressed in guard cells of Arabidopsis thaliana. Loss-of-function mutations in AtALMT12 impair stomatal closure induced by ABA, calcium and darkness, but do not abolish either the rapidly activated or the slowly activated anion currents previously identified as being important for stomatal closure. Expressed in Xenopus oocytes, AtALMT12 facilitates chloride and nitrate currents, but not those of organic solutes. Therefore, we conclude that AtALMT12 is a novel class of anion transporter involved in stomatal closure. PMID:20154005

Closing plant stomata requires a homolog of an aluminum-activated malate transporter.

PubMed

Sasaki, Takayuki; Mori, Izumi C; Furuichi, Takuya; Munemasa, Shintaro; Toyooka, Kiminori; Matsuoka, Ken; Murata, Yoshiyuki; Yamamoto, Yoko

2010-03-01

Plant stomata limit both carbon dioxide uptake and water loss; hence, stomatal aperture is carefully set as the environment fluctuates. Aperture area is known to be regulated in part by ion transport, but few of the transporters have been characterized. Here we report that AtALMT12 (At4g17970), a homolog of the aluminum-activated malate transporter (ALMT) of wheat, is expressed in guard cells of Arabidopsis thaliana. Loss-of-function mutations in AtALMT12 impair stomatal closure induced by ABA, calcium and darkness, but do not abolish either the rapidly activated or the slowly activated anion currents previously identified as being important for stomatal closure. Expressed in Xenopus oocytes, AtALMT12 facilitates chloride and nitrate currents, but not those of organic solutes. Therefore, we conclude that AtALMT12 is a novel class of anion transporter involved in stomatal closure.

Drought tolerance, xylem sap abscisic acid and stomatal conductance during soil drying: a comparison of canopy trees of three temperate deciduous angiosperms.

PubMed

Loewenstein, Nancy J.; Pallardy, Stephen G.

1998-07-01

Patterns of water relations, xylem sap abscisic acid concentration ([ABA]) and stomatal aperture were characterized and compared in drought-sensitive black walnut (Juglans nigra L.), less drought-sensitive sugar maple (Acer saccharum Marsh.) and drought-tolerant white oak (Quercus alba L.) trees co-occurring in a second-growth forest in Missouri, USA. There were strong correlations among reduction in predawn leaf water potential, increased xylem sap [ABA] and stomatal closure in all species. Stomatal conductance was more closely correlated with xylem sap ABA concentration than with ABA flux or xylem sap pH and cation concentrations. In isohydric black walnut, increased concentrations of ABA in the xylem sap appeared to be primarily of root origin, causing stomatal closure in response to soil drying. In anisohydric sugar maple and white oak, however, there were reductions in midday leaf water potential associated with stomatal closure, making it uncertain whether drought-induced xylem sap ABA was of leaf or root origin. The role of root-originated xylem sap ABA in these species as a signal to the shoot of the water status of the roots is, therefore, less certain.

Constitutive activation of a plasma membrane H(+)-ATPase prevents abscisic acid-mediated stomatal closure.

PubMed

Merlot, Sylvain; Leonhardt, Nathalie; Fenzi, Francesca; Valon, Christiane; Costa, Miguel; Piette, Laurie; Vavasseur, Alain; Genty, Bernard; Boivin, Karine; Müller, Axel; Giraudat, Jérôme; Leung, Jeffrey

2007-07-11

Light activates proton (H(+))-ATPases in guard cells, to drive hyperpolarization of the plasma membrane to initiate stomatal opening, allowing diffusion of ambient CO(2) to photosynthetic tissues. Light to darkness transition, high CO(2) levels and the stress hormone abscisic acid (ABA) promote stomatal closing. The overall H(+)-ATPase activity is diminished by ABA treatments, but the significance of this phenomenon in relationship to stomatal closure is still debated. We report two dominant mutations in the OPEN STOMATA2 (OST2) locus of Arabidopsis that completely abolish stomatal response to ABA, but importantly, to a much lesser extent the responses to CO(2) and darkness. The OST2 gene encodes the major plasma membrane H(+)-ATPase AHA1, and both mutations cause constitutive activity of this pump, leading to necrotic lesions. H(+)-ATPases have been traditionally assumed to be general endpoints of all signaling pathways affecting membrane polarization and transport. Our results provide evidence that AHA1 is a distinct component of an ABA-directed signaling pathway, and that dynamic downregulation of this pump during drought is an essential step in membrane depolarization to initiate stomatal closure.

A banana NAC transcription factor (MusaSNAC1) impart drought tolerance by modulating stomatal closure and H2O2 content.

PubMed

Negi, Sanjana; Tak, Himanshu; Ganapathi, T R

2018-03-01

MusaSNAC1 function in H 2 O 2 mediated stomatal closure and promote drought tolerance by directly binding to CGT[A/G] motif in regulatory region of multiple stress-related genes. Drought is a abiotic stress-condition, causing reduced plant growth and diminished crop yield. Guard cells of the stomata control photosynthesis and transpiration by regulating CO 2 exchange and water loss, thus affecting growth and crop yield. Roles of NAC (NAM, ATAF1/2 and CUC2) protein in regulation of stress-conditions has been well documented however, their control over stomatal aperture is largely unknown. In this study we report a banana NAC protein, MusaSNAC1 which induced stomatal closure by elevating H 2 O 2 content in guard cells during drought stress. Overexpression of MusaSNAC1 in banana resulted in higher number of stomata closure causing reduced water loss and thus elevated drought-tolerance. During drought, expression of GUS (β-glucuronidase) under P MusaSNAC1 was remarkably elevated in guard cells of stomata which correlated with its function as a transcription factor regulating stomatal aperture closing. MusaSNAC1 is a transcriptional activator belonging to SNAC subgroup and its 5'-upstream region contain multiple Dof1 elements as well as stress-associated cis-elements. Moreover, MusaSNAC1 also regulate multiple stress-related genes by binding to core site of NAC-proteins CGT[A/G] in their 5'-upstream region. Results indicated an interesting mechanism of drought tolerance through stomatal closure by H 2 O 2 generation in guard cells, regulated by a NAC-protein in banana.

The Physiology and Proteomics of Drought Tolerance in Maize: Early Stomatal Closure as a Cause of Lower Tolerance to Short-Term Dehydration?

PubMed Central

Benešová, Monika; Holá, Dana; Fischer, Lukáš; Jedelský, Petr L.; Hnilička, František; Wilhelmová, Naďa; Rothová, Olga; Kočová, Marie; Procházková, Dagmar; Honnerová, Jana; Fridrichová, Lenka; Hniličková, Helena

2012-01-01

Understanding the response of a crop to drought is the first step in the breeding of tolerant genotypes. In our study, two maize (Zea mays L.) genotypes with contrasting sensitivity to dehydration were subjected to moderate drought conditions. The subsequent analysis of their physiological parameters revealed a decreased stomatal conductance accompanied by a slighter decrease in the relative water content in the sensitive genotype. In contrast, the tolerant genotype maintained open stomata and active photosynthesis, even under dehydration conditions. Drought-induced changes in the leaf proteome were analyzed by two independent approaches, 2D gel electrophoresis and iTRAQ analysis, which provided compatible but only partially overlapping results. Drought caused the up-regulation of protective and stress-related proteins (mainly chaperones and dehydrins) in both genotypes. The differences in the levels of various detoxification proteins corresponded well with the observed changes in the activities of antioxidant enzymes. The number and levels of up-regulated protective proteins were generally lower in the sensitive genotype, implying a reduced level of proteosynthesis, which was also indicated by specific changes in the components of the translation machinery. Based on these results, we propose that the hypersensitive early stomatal closure in the sensitive genotype leads to the inhibition of photosynthesis and, subsequently, to a less efficient synthesis of the protective/detoxification proteins that are associated with drought tolerance. PMID:22719860

The physiology and proteomics of drought tolerance in maize: early stomatal closure as a cause of lower tolerance to short-term dehydration?

PubMed

Benešová, Monika; Holá, Dana; Fischer, Lukáš; Jedelský, Petr L; Hnilička, František; Wilhelmová, Naďa; Rothová, Olga; Kočová, Marie; Procházková, Dagmar; Honnerová, Jana; Fridrichová, Lenka; Hniličková, Helena

2012-01-01

Understanding the response of a crop to drought is the first step in the breeding of tolerant genotypes. In our study, two maize (Zea mays L.) genotypes with contrasting sensitivity to dehydration were subjected to moderate drought conditions. The subsequent analysis of their physiological parameters revealed a decreased stomatal conductance accompanied by a slighter decrease in the relative water content in the sensitive genotype. In contrast, the tolerant genotype maintained open stomata and active photosynthesis, even under dehydration conditions. Drought-induced changes in the leaf proteome were analyzed by two independent approaches, 2D gel electrophoresis and iTRAQ analysis, which provided compatible but only partially overlapping results. Drought caused the up-regulation of protective and stress-related proteins (mainly chaperones and dehydrins) in both genotypes. The differences in the levels of various detoxification proteins corresponded well with the observed changes in the activities of antioxidant enzymes. The number and levels of up-regulated protective proteins were generally lower in the sensitive genotype, implying a reduced level of proteosynthesis, which was also indicated by specific changes in the components of the translation machinery. Based on these results, we propose that the hypersensitive early stomatal closure in the sensitive genotype leads to the inhibition of photosynthesis and, subsequently, to a less efficient synthesis of the protective/detoxification proteins that are associated with drought tolerance.

Hydraulic patterns and safety margins, from stem to stomata, in three eastern US tree species

Treesearch

D.M. Johnson; K.A. McCulloh; F.C. Meinzer; D.R. Woodruff; D.M. Eissenstat

2011-01-01

Adequate water transport is necessary to prevent stomatal closure and allow for photosynthesis. Dysfunction in the water transport pathway can result in stomatal closure, and can be deleterious to overall plant health and survival. Although much is known about small branch hydraulics, little is known about the coordination of leaf and stem hydraulic function....

Cyclic monoterpene mediated modulations of Arabidopsis thaliana phenotype

PubMed Central

Kriegs, Bettina; Jansen, Marcus; Hahn, Katrin; Peisker, Helga; Šamajová, Olga; Beck, Martina; Braun, Silvia; Ulbrich, Andreas; Baluška, František

2010-01-01

Monoterpenes at high atmospheric concentrations are strong growth inhibitors in allelopathic interactions. Effects depend on dose, molecular structure of the monoterpene and on the species of the receiver plant. Stomata are among the first targets affected by camphor and menthol. Previously, it could be demonstrated that the compounds induce swelling of the protoplasts, prevent stomatal closure and enhance transpiration. In this study, we show that the block of stomatal closure is accompanied by changes to the cytoskeleton, which has a direct role in stomatal movements. Although MPK3 (MAP3 kinase) and ABF4 gene expressions are induced within six hours, stomatal closure is prevented. In contrast to ABF4, ABF2 (both transcription factors) is not induced. MPK3 and ABF4 both encode for proteins involved in the process of stomatal closure. The expression of PEPCase, an enzyme important for stomatal opening, is downregulated. The leaves develop stress symptoms, mirrored by transient changes in the expression profile of additional genes: lipoxygenase 2 (LOX2), CER5, CER6 (both important for wax production) and RD29B (an ABA inducible stress protein). Non-invasive methods showed a fast response of the plant to camphor fumigations both in a rapid decrease of the quantum yield and in the relative growth rate. Repeated exposures to the monoterpenes resulted finally in growth reduction and a stress related change in the phenotype. It is proposed that high concentrations or repeated exposure to monoterpenes led to irreversible damages, whereas low concentrations or short-term fumigations may have the potential to strengthen the plant fitness. PMID:20484979

Stomatal VPD Response: There Is More to the Story Than ABA.

PubMed

Merilo, Ebe; Yarmolinsky, Dmitry; Jalakas, Pirko; Parik, Helen; Tulva, Ingmar; Rasulov, Bakhtier; Kilk, Kalle; Kollist, Hannes

2018-01-01

Guard cells shrink and close stomatal pores when air humidity decreases (i.e. when the difference between the vapor pressures of leaf and atmosphere [VPD] increases). The role of abscisic acid (ABA) in VPD-induced stomatal closure has been studied using ABA-related mutants that respond to VPD in some studies and not in others. The importance of ABA biosynthesis in guard cells versus vasculature for whole-plant stomatal regulation is unclear as well. Here, we show that Arabidopsis ( Arabidopsis thaliana ) lines carrying mutations in different steps of ABA biosynthesis as well as pea ( Pisum sativum ) wilty and tomato ( Solanum lycopersicum ) flacca ABA-deficient mutants had higher stomatal conductance compared with wild-type plants. To characterize the role of ABA production in different cells, we generated transgenic plants where ABA biosynthesis was rescued in guard cells or phloem companion cells of an ABA-deficient mutant. In both cases, the whole-plant stomatal conductance, stunted growth phenotype, and leaf ABA level were restored to wild-type values, pointing to the redundancy of ABA sources and to the effectiveness of leaf ABA transport. All ABA-deficient lines closed their stomata rapidly and extensively in response to high VPD, whereas plants with mutated protein kinase OST1 showed stunted VPD-induced responses. Another strongly ABA-insensitive mutant, defective in the six ABA PYR/RCAR receptors, responded to changes in VPD in both directions strongly and symmetrically, indicating that its VPD-induced closure could be passive hydraulic. We discuss that both the VPD-induced passive hydraulic stomatal closure and the stomatal VPD regulation of ABA-deficient mutants may be conditional on the initial pretreatment stomatal conductance. © 2018 American Society of Plant Biologists. All Rights Reserved.

Stomatal Density and Responsiveness of Banana Fruit Stomates

PubMed Central

Johnson, Barbara E.; Brun, W. A.

1966-01-01

Determination of stomatal densities of the banana peel (Musa acuminata L. var Hort. Valery) by microscopic observations showed 30 times fewer stomates on fruit epidermis than found on the banana leaf. Observations also showed that peel stomates were not laid down in a linear pattern as on the leaf. It was demonstrated that stomatal responses occurred in banana fruit. Specific conditions of high humidity and light were necessary for stomatal opening: low humidity and darkness were necessary for closure. Responsiveness of the stomates continued for a considerable length of time after the fruit had been severed from the host. Images PMID:16656239

Stomatal control in tomato with ABA-deficient roots: response of grafted plants to soil drying.

PubMed

Holbrook, N Michele; Shashidhar, V R; James, Richard A; Munns, Rana

2002-06-01

The hypothesis that ABA produced by roots in drying soil is responsible for stomatal closure was tested with grafted plants constructed from the ABA-deficient tomato mutants, sitiens and flacca and their near-isogenic wild-type parent. Three types of experiments were conducted. In the first type, reciprocal grafts were made between the wild type and sitiens or flacca. Stomatal conductance accorded with the genotype of the shoot, not the root. Stomates closed in all of the grafted plants in response to soil drying, regardless of the root genotype, i.e. regardless of the ability of the roots to produce ABA. In the second type of experiment, wild-type shoots were grafted onto a split-root system consisting of one wild-type root grafted to one mutant (flacca or sitiens) root. Water was withheld from one root system, while the other was watered well so that the shoots did not experience any decline in water potential or loss of turgor. Stomates closed to a similar extent when water was withheld from the mutant roots or the wild-type roots. In the third type of experiment, grafted plants with wild-type shoots and either wild-type or sitiens roots were established in pots that could be placed inside a pressure chamber, and the pressure increased as the soil dried so that the shoots remained fully turgid throughout. Stomates closed as the soil dried, regardless of whether the roots were wild type or sitiens. These experiments demonstrate that stomatal closure in response to soil drying can occur in the absence of leaf water deficit, and does not require ABA production by roots. A chemical signal from roots leading to a change in apoplastic ABA levels in leaves may be responsible for the stomatal closure.

Contrasting physiological effects of partial root zone drying in field-grown grapevine (Vitis vinifera L. cv. Monastrell) according to total soil water availability

PubMed Central

Romero, Pascual; Dodd, Ian C.; Martinez-Cutillas, Adrian

2012-01-01

Different spatial distributions of soil moisture were imposed on field-grown grapevines by applying the same irrigation volumes to the entire (DI; deficit irrigation) or part of the (PRD; partial root zone drying) root zone. Five treatments were applied: controls irrigated at 60% ETc (crop evapotranspiration) for the whole season (308 mm year−1); DI-1 and PRD-1 that received the same irrigation as controls before fruit set, 30% ETc from fruit set to harvest and 45% ETc post-harvest (192 mm year−1); and DI-2 and PRD-2 that were the same, except that 15% ETc was applied from fruit set to harvest (142 mm year−1). Compared with DI-1, PRD-1 maintained higher leaf area post-veraison and increased root water uptake, whole-plant hydraulic conductance, leaf transpiration, stomatal conductance, and photosynthesis, but decreased intrinsic gas exchange efficiency without causing differences in leaf xylem abscisic acid (ABA) concentration. Compared with DI-2, PRD-2 increased leaf xylem ABA concentration and decreased root water uptake, whole-plant hydraulic conductance, leaf transpiration, stomatal conductance, and photosynthesis, mainly at the beginning of PRD cycles. Distinctive PRD effects (e.g. greater stomatal closure) depended on the volumetric soil water content of the wet root zone, as predicted from a model of root-to-shoot ABA signalling. PMID:22451721

Metabolomics and Proteomics of Brassica napus Guard Cells in Response to Low CO2

PubMed Central

Geng, Sisi; Yu, Bing; Zhu, Ning; Dufresne, Craig; Chen, Sixue

2017-01-01

Stomatal guard cell response to various stimuli is an important process that balances plant carbon dioxide (CO2) uptake and water transpiration. Elevated CO2 induces stomatal closure, while low CO2 promotes stomatal opening. The signaling process of elevated CO2 induced stomatal closure has been extensively studied in recent years. However, the mechanism of low CO2 induced stomatal opening is not fully understood. Here we report metabolomic and proteomic responses of Brassica napus guard cells to low CO2 using hyphenated mass spectrometry technologies. A total of 411 metabolites and 1397 proteins were quantified in a time-course study of low CO2 effects. Metabolites and proteins that exhibited significant changes are overrepresented in fatty acid metabolism, starch and sucrose metabolism, glycolysis and redox regulation. Concomitantly, multiple hormones that promote stomatal opening increased in response to low CO2. Interestingly, jasmonic acid precursors were diverted to a branch pathway of traumatic acid biosynthesis. These results indicate that the low CO2 response is mediated by a complex crosstalk between different phytohormones. PMID:28791296

Metabolomics and Proteomics of Brassica napus Guard Cells in Response to Low CO2.

PubMed

Geng, Sisi; Yu, Bing; Zhu, Ning; Dufresne, Craig; Chen, Sixue

2017-01-01

Stomatal guard cell response to various stimuli is an important process that balances plant carbon dioxide (CO 2 ) uptake and water transpiration. Elevated CO 2 induces stomatal closure, while low CO 2 promotes stomatal opening. The signaling process of elevated CO 2 induced stomatal closure has been extensively studied in recent years. However, the mechanism of low CO 2 induced stomatal opening is not fully understood. Here we report metabolomic and proteomic responses of Brassica napus guard cells to low CO 2 using hyphenated mass spectrometry technologies. A total of 411 metabolites and 1397 proteins were quantified in a time-course study of low CO 2 effects. Metabolites and proteins that exhibited significant changes are overrepresented in fatty acid metabolism, starch and sucrose metabolism, glycolysis and redox regulation. Concomitantly, multiple hormones that promote stomatal opening increased in response to low CO 2 . Interestingly, jasmonic acid precursors were diverted to a branch pathway of traumatic acid biosynthesis. These results indicate that the low CO 2 response is mediated by a complex crosstalk between different phytohormones.

Overexpression of StNF-YB3.1 reduces photosynthetic capacity and tuber production, and promotes ABA-mediated stomatal closure in potato (Solanum tuberosum L.).

PubMed

Xuanyuan, Guochao; Lu, Congming; Zhang, Ruofang; Jiang, Jiming

2017-08-01

Nuclear factor Y (NF-Y) is one of the most ubiquitous transcription factors (TFs), comprising NF-YA, NF-YB and NF-YC subunits, and has been identified and reported in various aspects of development for plants and animals. In this work, StNF-YB3.1, a putative potato NF-YB subunit encoding gene, was isolated from Solanum tuberosum by rapid amplification of cDNA ends (RACE). Overexpression of StNF-YB3.1 in potato (cv. Atlantic) resulted in accelerated onset of flowering, and significant increase in leaf chlorophyll content in field trials. However, transgenic potato plants overexpressing StNF-YB3.1 (OEYB3.1) showed significant decreases in photosynthetic rate and stomatal conductance both at tuber initiation and bulking stages. OEYB3.1 lines were associated with significantly fewer tuber numbers and yield reduction. Guard cell size and stomatal density were not changed in OEYB3.1 plants, whereas ABA-mediated stomatal closure was accelerated compared to that of wild type plants because of the up-regulation of genes for ABA signaling, such as StCPK10-like, StSnRK2.6/OST1-like, StSnRK2.7-like and StSLAC1-like. We speculate that the acceleration of stomatal closure was a possible reason for the significantly decreased stomatal conductance and photosynthetic rate. Copyright © 2017 Elsevier B.V. All rights reserved.

Evolutionary Conservation of ABA Signaling for Stomatal Closure1[OPEN

PubMed Central

Huang, Yuqing; Dai, Fei; Franks, Peter J.; Nevo, Eviatar; Soltis, Douglas E.; Soltis, Pamela S.; Xue, Dawei; Zhang, Guoping; Pogson, Barry J.

2017-01-01

Abscisic acid (ABA)-driven stomatal regulation reportedly evolved after the divergence of ferns, during the early evolution of seed plants approximately 360 million years ago. This hypothesis is based on the observation that the stomata of certain fern species are unresponsive to ABA, but exhibit passive hydraulic control. However, ABA-induced stomatal closure was detected in some mosses and lycophytes. Here, we observed that a number of ABA signaling and membrane transporter protein families diversified over the evolutionary history of land plants. The aquatic ferns Azolla filiculoides and Salvinia cucullata have representatives of 23 families of proteins orthologous to those of Arabidopsis (Arabidopsis thaliana) and all other land plant species studied. Phylogenetic analysis of the key ABA signaling proteins indicates an evolutionarily conserved stomatal response to ABA. Moreover, comparative transcriptomic analysis has identified a suite of ABA-responsive genes that differentially expressed in a terrestrial fern species, Polystichum proliferum. These genes encode proteins associated with ABA biosynthesis, transport, reception, transcription, signaling, and ion and sugar transport, which fit the general ABA signaling pathway constructed from Arabidopsis and Hordeum vulgare. The retention of these key ABA-responsive genes could have had a profound effect on the adaptation of ferns to dry conditions. Furthermore, stomatal assays have shown the primary evidence for ABA-induced closure of stomata in two terrestrial fern species P. proliferum and Nephrolepis exaltata. In summary, we report, to our knowledge, new molecular and physiological evidence for the presence of active stomatal control in ferns. PMID:28232585

Effects of Changing Stomatal Width in A Red Pine Forest on Soil Water Content, Leaf Water Potential, Bole Diameter, and Growth

PubMed Central

Turner, Neil C.; Waggoner, Paul E.

1968-01-01

Spraying a 16 meter tall stand of red pine (Pinus resinosa Ait.) with 10−3 m phenylmercuric acetate in early June and again in mid-July resulted in the water use between June 1 and October 25 being reduced by almost 10%. It was demonstrated that this was caused by an increase in the leaf resistance with partial stomatal closure, which reduced absolute water potential in the needles by 1 to 3 bars in the middle of the day. Smaller demands were made upon the reserves of water in the bole of the tree as shown by the smaller bole contraction in the treated trees. Although needle length and dry weight were unaffected by the spray, radial growth was reduced by approximately 32%. The dependence of leaf resistance on light intensity is shown, and its independence from leaf water potential discussed. PMID:16656870

Predicting Essential Components of Signal Transduction Networks: A Dynamic Model of Guard Cell Abscisic Acid Signaling

PubMed Central

Li, Song; Assmann, Sarah M; Albert, Réka

2006-01-01

Plants both lose water and take in carbon dioxide through microscopic stomatal pores, each of which is regulated by a surrounding pair of guard cells. During drought, the plant hormone abscisic acid (ABA) inhibits stomatal opening and promotes stomatal closure, thereby promoting water conservation. Dozens of cellular components have been identified to function in ABA regulation of guard cell volume and thus of stomatal aperture, but a dynamic description is still not available for this complex process. Here we synthesize experimental results into a consistent guard cell signal transduction network for ABA-induced stomatal closure, and develop a dynamic model of this process. Our model captures the regulation of more than 40 identified network components, and accords well with previous experimental results at both the pathway and whole-cell physiological level. By simulating gene disruptions and pharmacological interventions we find that the network is robust against a significant fraction of possible perturbations. Our analysis reveals the novel predictions that the disruption of membrane depolarizability, anion efflux, actin cytoskeleton reorganization, cytosolic pH increase, the phosphatidic acid pathway, or K+ efflux through slowly activating K+ channels at the plasma membrane lead to the strongest reduction in ABA responsiveness. Initial experimental analysis assessing ABA-induced stomatal closure in the presence of cytosolic pH clamp imposed by the weak acid butyrate is consistent with model prediction. Simulations of stomatal response as derived from our model provide an efficient tool for the identification of candidate manipulations that have the best chance of conferring increased drought stress tolerance and for the prioritization of future wet bench analyses. Our method can be readily applied to other biological signaling networks to identify key regulatory components in systems where quantitative information is limited. PMID:16968132

Functional convergence of oxylipin and abscisic acid pathways controls stomatal closure in response to drought.

PubMed

Savchenko, Tatyana; Kolla, Venkat A; Wang, Chang-Quan; Nasafi, Zainab; Hicks, Derrick R; Phadungchob, Bpantamars; Chehab, Wassim E; Brandizzi, Federica; Froehlich, John; Dehesh, Katayoon

2014-03-01

Membranes are primary sites of perception of environmental stimuli. Polyunsaturated fatty acids are major structural constituents of membranes that also function as modulators of a multitude of signal transduction pathways evoked by environmental stimuli. Different stresses induce production of a distinct blend of oxygenated polyunsaturated fatty acids, "oxylipins." We employed three Arabidopsis (Arabidopsis thaliana) ecotypes to examine the oxylipin signature in response to specific stresses and determined that wounding and drought differentially alter oxylipin profiles, particularly the allene oxide synthase branch of the oxylipin pathway, responsible for production of jasmonic acid (JA) and its precursor 12-oxo-phytodienoic acid (12-OPDA). Specifically, wounding induced both 12-OPDA and JA levels, whereas drought induced only the precursor 12-OPDA. Levels of the classical stress phytohormone abscisic acid (ABA) were also mainly enhanced by drought and little by wounding. To explore the role of 12-OPDA in plant drought responses, we generated a range of transgenic lines and exploited the existing mutant plants that differ in their levels of stress-inducible 12-OPDA but display similar ABA levels. The plants producing higher 12-OPDA levels exhibited enhanced drought tolerance and reduced stomatal aperture. Furthermore, exogenously applied ABA and 12-OPDA, individually or combined, promote stomatal closure of ABA and allene oxide synthase biosynthetic mutants, albeit most effectively when combined. Using tomato (Solanum lycopersicum) and Brassica napus verified the potency of this combination in inducing stomatal closure in plants other than Arabidopsis. These data have identified drought as a stress signal that uncouples the conversion of 12-OPDA to JA and have revealed 12-OPDA as a drought-responsive regulator of stomatal closure functioning most effectively together with ABA.

OsASR5 enhances drought tolerance through a stomatal closure pathway associated with ABA and H2 O2 signalling in rice.

PubMed

Li, Jinjie; Li, Yang; Yin, Zhigang; Jiang, Jihong; Zhang, Minghui; Guo, Xiao; Ye, Zhujia; Zhao, Yan; Xiong, Haiyan; Zhang, Zhanying; Shao, Yujie; Jiang, Conghui; Zhang, Hongliang; An, Gynheung; Paek, Nam-Chon; Ali, Jauhar; Li, Zichao

2017-02-01

Drought is one of the major abiotic stresses that directly implicate plant growth and crop productivity. Although many genes in response to drought stress have been identified, genetic improvement to drought resistance especially in food crops is showing relatively slow progress worldwide. Here, we reported the isolation of abscisic acid, stress and ripening (ASR) genes from upland rice variety, IRAT109 (Oryza sativa L. ssp. japonica), and demonstrated that overexpression of OsASR5 enhanced osmotic tolerance in Escherichia coli and drought tolerance in Arabidopsis and rice by regulating leaf water status under drought stress conditions. Moreover, overexpression of OsASR5 in rice increased endogenous ABA level and showed hypersensitive to exogenous ABA treatment at both germination and postgermination stages. The production of H 2 O 2 , a second messenger for the induction of stomatal closure in response to ABA, was activated in overexpression plants under drought stress conditions, consequently, increased stomatal closure and decreased stomatal conductance. In contrast, the loss-of-function mutant, osasr5, showed sensitivity to drought stress with lower relative water content under drought stress conditions. Further studies demonstrated that OsASR5 functioned as chaperone-like protein and interacted with stress-related HSP40 and 2OG-Fe (II) oxygenase domain containing proteins in yeast and plants. Taken together, we suggest that OsASR5 plays multiple roles in response to drought stress by regulating ABA biosynthesis, promoting stomatal closure, as well as acting as chaperone-like protein that possibly prevents drought stress-related proteins from inactivation. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Transcriptome analysis of Pinus halepensis under drought stress and during recovery

PubMed Central

Fox, Hagar; Doron-Faigenboim, Adi; Kelly, Gilor; Bourstein, Ronny; Attia, Ziv; Zhou, Jing; Moshe, Yosef; Moshelion, Menachem; David-Schwartz, Rakefet

2018-01-01

Abstract Forest trees use various strategies to cope with drought stress and these strategies involve complex molecular mechanisms. Pinus halepensis Miller (Aleppo pine) is found throughout the Mediterranean basin and is one of the most drought-tolerant pine species. In order to decipher the molecular mechanisms that P. halepensis uses to withstand drought, we performed large-scale physiological and transcriptome analyses. We selected a mature tree from a semi-arid area with suboptimal growth conditions for clonal propagation through cuttings. We then used a high-throughput experimental system to continuously monitor whole-plant transpiration rates, stomatal conductance and the vapor pressure deficit. The transcriptomes of plants were examined at six physiological stages: pre-stomatal response, partial stomatal closure, minimum transpiration, post-irrigation, partial recovery and full recovery. At each stage, data from plants exposed to the drought treatment were compared with data collected from well-irrigated control plants. A drought-stressed P. halepensis transcriptome was created using paired-end RNA-seq. In total, ~6000 differentially expressed, non-redundant transcripts were identified between drought-treated and control trees. Cluster analysis has revealed stress-induced down-regulation of transcripts related to photosynthesis, reactive oxygen species (ROS)-scavenging through the ascorbic acid (AsA)-glutathione cycle, fatty acid and cell wall biosynthesis, stomatal activity, and the biosynthesis of flavonoids and terpenoids. Up-regulated processes included chlorophyll degradation, ROS-scavenging through AsA-independent thiol-mediated pathways, abscisic acid response and accumulation of heat shock proteins, thaumatin and exordium. Recovery from drought induced strong transcription of retrotransposons, especially the retrovirus-related transposon Tnt1-94. The drought-related transcriptome illustrates this species’ dynamic response to drought and recovery and unravels novel mechanisms. PMID:29177514

Transcriptome analysis of Pinus halepensis under drought stress and during recovery.

PubMed

Fox, Hagar; Doron-Faigenboim, Adi; Kelly, Gilor; Bourstein, Ronny; Attia, Ziv; Zhou, Jing; Moshe, Yosef; Moshelion, Menachem; David-Schwartz, Rakefet

2018-03-01

Forest trees use various strategies to cope with drought stress and these strategies involve complex molecular mechanisms. Pinus halepensis Miller (Aleppo pine) is found throughout the Mediterranean basin and is one of the most drought-tolerant pine species. In order to decipher the molecular mechanisms that P. halepensis uses to withstand drought, we performed large-scale physiological and transcriptome analyses. We selected a mature tree from a semi-arid area with suboptimal growth conditions for clonal propagation through cuttings. We then used a high-throughput experimental system to continuously monitor whole-plant transpiration rates, stomatal conductance and the vapor pressure deficit. The transcriptomes of plants were examined at six physiological stages: pre-stomatal response, partial stomatal closure, minimum transpiration, post-irrigation, partial recovery and full recovery. At each stage, data from plants exposed to the drought treatment were compared with data collected from well-irrigated control plants. A drought-stressed P. halepensis transcriptome was created using paired-end RNA-seq. In total, ~6000 differentially expressed, non-redundant transcripts were identified between drought-treated and control trees. Cluster analysis has revealed stress-induced down-regulation of transcripts related to photosynthesis, reactive oxygen species (ROS)-scavenging through the ascorbic acid (AsA)-glutathione cycle, fatty acid and cell wall biosynthesis, stomatal activity, and the biosynthesis of flavonoids and terpenoids. Up-regulated processes included chlorophyll degradation, ROS-scavenging through AsA-independent thiol-mediated pathways, abscisic acid response and accumulation of heat shock proteins, thaumatin and exordium. Recovery from drought induced strong transcription of retrotransposons, especially the retrovirus-related transposon Tnt1-94. The drought-related transcriptome illustrates this species' dynamic response to drought and recovery and unravels novel mechanisms.

Diel trends in stomatal response to ozone and water deficit: a unique relationship of midday values to growth and allometry in Pima cotton?

Treesearch

D. A. Grantz; R. Paudel; H.-B. Vu; A. Shrestha; Nancy Grulke; L. J. De Kok

2015-01-01

Plant responses to ozone (O3) and water deficit (WD) are commonly observed, although less is known about their interaction. Stomatal conductance (gs) is both an impact of these stressors and a protective response to them. Stomatal closure reduces inward flux of O3 and outward flux...

Rice Stomatal Closure Requires Guard Cell Plasma Membrane ATP-Binding Cassette Transporter RCN1/OsABCG5.

PubMed

Matsuda, Shuichi; Takano, Sho; Sato, Moeko; Furukawa, Kaoru; Nagasawa, Hidetaka; Yoshikawa, Shoko; Kasuga, Jun; Tokuji, Yoshihiko; Yazaki, Kazufumi; Nakazono, Mikio; Takamure, Itsuro; Kato, Kiyoaki

2016-03-07

Water stress is one of the major environmental stresses that affect agricultural production worldwide. Water loss from plants occurs primarily through stomatal pores. Here, we report that an Oryza sativa half-size ATP-binding cassette (ABC) subfamily G protein, RCN1/OsABCG5, is involved in stomatal closure mediated by phytohormone abscisic acid (ABA) accumulation in guard cells. We found that the GFP-RCN1/OsABCG5-fusion protein was localized at the plasma membrane in guard cells. The percentage of guard cell pairs containing both ABA and GFP-RCN1/OsABCG5 increased after exogenous ABA treatment, whereas they were co-localized in guard cell pairs regardless of whether exogenous ABA was applied. ABA application resulted in a smaller increase in the percentage of guard cell pairs containing ABA in rcn1 mutant (A684P) and RCN1-RNAi than in wild-type plants. Furthermore, polyethylene glycol (drought stress)-inducible ABA accumulation in guard cells did not occur in rcn1 mutants. Stomata closure mediated by exogenous ABA application was strongly reduced in rcn1 mutants. Finally, rcn1 mutant plants had more rapid water loss from detached leaves than the wild-type plants. These results indicate that in response to drought stress, RCN1/OsABCG5 is involved in accumulation of ABA in guard cells, which is indispensable for stomatal closure. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

WATER STRESS REDUCES OZONE INJURY VIA A STOMATAL MECHANISM

EPA Science Inventory

Various studies have shown that water-stressed plants are more tolerant of ozone exposures than are unstressed plants. Two probable explanations for this tolerance are (a) stomatal closure which reduces ozone uptake and (b) biochemical or anatomical changes within the leaves. Pha...

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 peak canopy transpiration under the highest atmospheric vapor pressure deficits observed (>3.0 kPa). Thus, our tree-ring data provide further evidence of what has become known as the "divergence problem" in northern forests, but our physiological measurements suggest that drought-induced stomatal closure may not be the cause.

Fern Stomatal Responses to ABA and CO2 Depend on Species and Growth Conditions.

PubMed

Hõrak, Hanna; Kollist, Hannes; Merilo, Ebe

2017-06-01

Changing atmospheric CO 2 levels, climate, and air humidity affect plant gas exchange that is controlled by stomata, small pores on plant leaves and stems formed by guard cells. Evolution has shaped the morphology and regulatory mechanisms governing stomatal movements to correspond to the needs of various land plant groups over the past 400 million years. Stomata close in response to the plant hormone abscisic acid (ABA), elevated CO 2 concentration, and reduced air humidity. Whether the active regulatory mechanisms that control stomatal closure in response to these stimuli are present already in mosses, the oldest plant group with stomata, or were acquired more recently in angiosperms remains controversial. It has been suggested that the stomata of the basal vascular plants, such as ferns and lycophytes, close solely hydropassively. On the other hand, active stomatal closure in response to ABA and CO 2 was found in several moss, lycophyte, and fern species. Here, we show that the stomata of two temperate fern species respond to ABA and CO 2 and that an active mechanism of stomatal regulation in response to reduced air humidity is present in some ferns. Importantly, fern stomatal responses depend on growth conditions. The data indicate that the stomatal behavior of ferns is more complex than anticipated before, and active stomatal regulation is present in some ferns and has possibly been lost in others. Further analysis that takes into account fern species, life history, evolutionary age, and growth conditions is required to gain insight into the evolution of land plant stomatal responses. © 2017 American Society of Plant Biologists. All Rights Reserved.

Fern Stomatal Responses to ABA and CO2 Depend on Species and Growth Conditions1[OPEN

PubMed Central

2017-01-01

Changing atmospheric CO2 levels, climate, and air humidity affect plant gas exchange that is controlled by stomata, small pores on plant leaves and stems formed by guard cells. Evolution has shaped the morphology and regulatory mechanisms governing stomatal movements to correspond to the needs of various land plant groups over the past 400 million years. Stomata close in response to the plant hormone abscisic acid (ABA), elevated CO2 concentration, and reduced air humidity. Whether the active regulatory mechanisms that control stomatal closure in response to these stimuli are present already in mosses, the oldest plant group with stomata, or were acquired more recently in angiosperms remains controversial. It has been suggested that the stomata of the basal vascular plants, such as ferns and lycophytes, close solely hydropassively. On the other hand, active stomatal closure in response to ABA and CO2 was found in several moss, lycophyte, and fern species. Here, we show that the stomata of two temperate fern species respond to ABA and CO2 and that an active mechanism of stomatal regulation in response to reduced air humidity is present in some ferns. Importantly, fern stomatal responses depend on growth conditions. The data indicate that the stomatal behavior of ferns is more complex than anticipated before, and active stomatal regulation is present in some ferns and has possibly been lost in others. Further analysis that takes into account fern species, life history, evolutionary age, and growth conditions is required to gain insight into the evolution of land plant stomatal responses. PMID:28351911

Stomatal control of leaf fluxes of carbonyl sulfide and CO2 in a Typha freshwater marsh

NASA Astrophysics Data System (ADS)

Sun, Wu; Maseyk, Kadmiel; Lett, Céline; Seibt, Ulli

2018-06-01

Carbonyl sulfide (COS) is an emerging tracer to constrain land photosynthesis at canopy to global scales, because leaf COS and CO2 uptake processes are linked through stomatal diffusion. The COS tracer approach requires knowledge of the concentration normalized ratio of COS uptake to photosynthesis, commonly known as the leaf relative uptake (LRU). LRU is known to increase under low light, but the environmental controls over LRU variability in the field are poorly understood due to scant leaf scale observations. Here we present the first direct observations of LRU responses to environmental variables in the field. We measured leaf COS and CO2 fluxes at a freshwater marsh in summer 2013. Daytime leaf COS and CO2 uptake showed similar peaks in the mid-morning and late afternoon separated by a prolonged midday depression, highlighting the common stomatal control on diffusion. At night, in contrast to CO2, COS uptake continued, indicating partially open stomata. LRU ratios showed a clear relationship with photosynthetically active radiation (PAR), converging to 1.0 at high PAR, while increasing sharply at low PAR. Daytime integrated LRU (calculated from daytime mean COS and CO2 uptake) ranged from 1 to 1.5, with a mean of 1.2 across the campaign, significantly lower than the previously reported laboratory mean value (˜ 1.6). Our results indicate two major determinants of LRU - light and vapor deficit. Light is the primary driver of LRU because CO2 assimilation capacity increases with light, while COS consumption capacity does not. Superimposed upon the light response is a secondary effect that high vapor deficit further reduces LRU, causing LRU minima to occur in the afternoon, not at noon. The partial stomatal closure induced by high vapor deficit suppresses COS uptake more strongly than CO2 uptake because stomatal resistance is a more dominant component in the total resistance of COS. Using stomatal conductance estimates, we show that LRU variability can be explained in terms of different patterns of stomatal vs. internal limitations on COS and CO2 uptake. Our findings illustrate the stomata-driven coupling of COS and CO2 uptake during the most photosynthetically active period in the field and provide an in situ characterization of LRU - a key parameter required for the use of COS as a photosynthetic tracer.

Stomata Prioritize Their Responses to Multiple Biotic and Abiotic Signal Inputs

PubMed Central

Chen, Peilei; Qiu, Muqing; Jiang, Kun; Wang, Genxuan

2014-01-01

Stomata are microscopic pores in leaf epidermis that regulate gas exchange between plants and the environment. Being natural openings on the leaf surface, stomata also serve as ports for the invasion of foliar pathogenic bacteria. Each stomatal pore is enclosed by a pair of guard cells that are able to sense a wide spectrum of biotic and abiotic stresses and respond by precisely adjusting the pore width. However, it is not clear whether stomatal responses to simultaneously imposed biotic and abiotic signals are mutually dependent on each other. Here we show that a genetically engineered Escherichia coli strain DH5α could trigger stomatal closure in Vicia faba, an innate immune response that might depend on NADPH oxidase-mediated ROS burst. DH5α-induced stomatal closure could be abolished or disguised under certain environmental conditions like low [CO2], darkness, and drought, etc. Foliar spraying of high concentrations of ABA could reduce stomatal aperture in high humidity-treated faba bean plants. Consistently, the aggressive multiplication of DH5α bacteria in Vicia faba leaves under high humidity could be alleviated by exogenous application of ABA. Our data suggest that a successful colonization of bacteria on the leaf surface is correlated with stomatal aperture regulation by a specific set of environmental factors. PMID:25003527

The effect of competition from neighbours on stomatal conductance in lettuce and tomato plants.

PubMed

Vysotskaya, Lidiya; Wilkinson, Sally; Davies, William J; Arkhipova, Tatyana; Kudoyarova, Guzel

2011-05-01

Competition decreased transpiration from young lettuce plants after 2 days, before any reductions in leaf area became apparent, and stomatal conductance (g(s) ) of lettuce and tomato plants was also reduced. Stomatal closure was not due to hydraulic signals or competition for nutrients, as soil water content, leaf water status and leaf nitrate concentrations were unaffected by neighbours. Competition-induced stomatal closure was absent in an abscisic acid (ABA)-deficient tomato mutant, flacca, indicating a fundamental involvement of ABA. Although tomato xylem sap ABA concentrations were unaffected by the presence of neighbours, ABA/pH-based stomatal modulation is still likely to underlie the response to competition, as soil and xylem sap alkalization was observed in competing plants. Competition also modulated leaf ethylene production, and treatment of lettuce plants with an ethylene perception inhibitor (1-methylcyclopropene) diminished the difference in g(s) between single and competing plants grown in a controlled environment room, but increased it in plants grown in the greenhouse: ethylene altered the extent of the stomatal response to competition. Effects of competition on g(s) are discussed in terms of the detection of the absence of neighbours: increases in g(s) and carbon fixation may allow faster initial space occupancy within an emerging community/crop. © 2011 Blackwell Publishing Ltd.

A chloroplast retrograde signal, 3'-phosphoadenosine 5'-phosphate, acts as a secondary messenger in abscisic acid signaling in stomatal closure and germination.

PubMed

Pornsiriwong, Wannarat; Estavillo, Gonzalo M; Chan, Kai Xun; Tee, Estee E; Ganguly, Diep; Crisp, Peter A; Phua, Su Yin; Zhao, Chenchen; Qiu, Jiaen; Park, Jiyoung; Yong, Miing Tiem; Nisar, Nazia; Yadav, Arun Kumar; Schwessinger, Benjamin; Rathjen, John; Cazzonelli, Christopher I; Wilson, Philippa B; Gilliham, Matthew; Chen, Zhong-Hua; Pogson, Barry J

2017-03-21

Organelle-nuclear retrograde signaling regulates gene expression, but its roles in specialized cells and integration with hormonal signaling remain enigmatic. Here we show that the SAL1-PAP (3'-phosphoadenosine 5'- phosphate) retrograde pathway interacts with abscisic acid (ABA) signaling to regulate stomatal closure and seed germination in Arabidopsis . Genetically or exogenously manipulating PAP bypasses the canonical signaling components ABA Insensitive 1 (ABI1) and Open Stomata 1 (OST1); priming an alternative pathway that restores ABA-responsive gene expression, ROS bursts, ion channel function, stomatal closure and drought tolerance in ost1 -2. PAP also inhibits wild type and abi1 -1 seed germination by enhancing ABA sensitivity. PAP-XRN signaling interacts with ABA, ROS and Ca 2+ ; up-regulating multiple ABA signaling components, including lowly-expressed Calcium Dependent Protein Kinases (CDPKs) capable of activating the anion channel SLAC1. Thus, PAP exhibits many secondary messenger attributes and exemplifies how retrograde signals can have broader roles in hormone signaling, allowing chloroplasts to fine-tune physiological responses.

Midday depression of leaf CO2 exchange within the crown of Dipterocarpus sublamellatus in a lowland dipterocarp forest in Peninsular Malaysia.

PubMed

Kosugi, Yoshiko; Takanashi, Satoru; Matsuo, Naoko; Nik, Abdul Rahim

2009-04-01

We observed diurnal and seasonal patterns of leaf-scale gas exchange within the crown of a Dipterocarpus sublamellatus Foxw. tree growing in a lowland dipterocarp forest at Pasoh, Peninsular Malaysia. Observations were carried out nine times over 6 years, from September 2002 to December 2007. Observation periods included both wet and mild-dry periods, and natural and saturated photosynthetic photon flux density (PPFD) light conditions. In situ measurements of the diurnal change in net photosynthetic rate and in stomatal conductance were carried out on canopy leaves of a 40-m-tall D. sublamellatus tree, which was accessed from a canopy corridor. A diurnal change in electron transport rate was observed under saturated PPFD conditions. The maximum net assimilation rate was approximately 10 micromol m(-2) s(-1). There was a clear inhibition of the net assimilation rate coupled with stomatal closure after late morning and this inhibition occurred year-round. Although the electron transport rate decreased alongside this inhibition, it sometimes followed on. Numerical analysis showed that the main factor in the inhibition of the net assimilation rate was patchy bimodal stomatal closure, which occurred in both mild-dry and wet periods. The midday depression occurred year-round, though there are fluctuations in soil moisture during the mild-dry and wet periods. The magnitude of the inhibition was not related to soil water content but was related to vapor pressure deficit (VPD): that is, whether the days were sunny and hot or cloudy and cool. On cloudy, cool days in the wet period, the net photosynthesis was only moderately inhibited, but it still decreased in the afternoon and was coupled with patchy stomatal closure, even in quite moderate VPD, leaf temperature and PPFD conditions. Our results suggest that patchy stomatal closure signaled by the increase in VPD, in transpiration and by circadian rhythms, was the key factor in constraining midday leaf gas exchange of the D. sublamellatus canopy leaves.

F-box protein DOR functions as a novel inhibitory factor for abscisic acid-induced stomatal closure under drought stress in Arabidopsis,.

PubMed

Zhang, Yu'e; Xu, Wenying; Li, Zhonghui; Deng, Xing Wang; Wu, Weihua; Xue, Yongbiao

2008-12-01

Guard cells, which form stoma in leaf epidermis, sense and integrate environmental signals to modulate stomatal aperture in response to diverse conditions. Under drought stress, plants synthesize abscisic acid (ABA), which in turn induces a rapid closing of stoma, to prevent water loss by transpiration. However, many aspects of the molecular mechanism for ABA-mediated stomatal closure are still not understood. Here, we report a novel negative regulator of guard cell ABA signaling, DOR, in Arabidopsis (Arabidopsis thaliana). The DOR gene encodes a putative F-box protein, a member of the S-locus F-box-like family related to AhSLF-S(2) and specifically interacting with ASK14 and CUL1. A null mutation in DOR resulted in a hypersensitive ABA response of stomatal closing and a substantial increase of drought tolerance; in contrast, the transgenic plants overexpressing DOR were more susceptible to the drought stress. DOR is strongly expressed in guard cells and suppressed by ABA treatment, suggesting a negative feedback loop of DOR in ABA responses. Double-mutant analyses of dor with ABA-insensitive mutant abi1-1 showed that abi1-1 is epistatic to dor, but no apparent change of phospholipase Dalpha1 was detected between the wild type and dor. Affymetrix GeneChip analysis showed that DOR likely regulates ABA biosynthesis under drought stress. Taken together, our results demonstrate that DOR acts independent of phospholipase Dalpha1 in an ABA signaling pathway to inhibit the ABA-induced stomatal closure under drought stress.

Calcium Pumps and Interacting BON1 Protein Modulate Calcium Signature, Stomatal Closure, and Plant Immunity1[OPEN

PubMed Central

Bao, Yongmei; Yang, Ziyuan; Yu, Huiyun; Li, Yun; Wang, Shu; Zou, Baohong; Xu, Dachao; Ma, Zhiqi

2017-01-01

Calcium signaling is essential for environmental responses including immune responses. Here, we provide evidence that the evolutionarily conserved protein BONZAI1 (BON1) functions together with autoinhibited calcium ATPase10 (ACA10) and ACA8 to regulate calcium signals in Arabidopsis. BON1 is a plasma membrane localized protein that negatively regulates the expression of immune receptor genes and positively regulates stomatal closure. We found that BON1 interacts with the autoinhibitory domains of ACA10 and ACA8, and the aca10 loss-of-function (LOF) mutants have an autoimmune phenotype similar to that of the bon1 LOF mutants. Genetic evidences indicate that BON1 positively regulates the activities of ACA10 and ACA8. Consistent with this idea, the steady level of calcium concentration is increased in both aca10 and bon1 mutants. Most strikingly, cytosolic calcium oscillation imposed by external calcium treatment was altered in aca10, aca8, and bon1 mutants in guard cells. In addition, calcium- and pathogen-induced stomatal closure was compromised in the aca10 and bon1 mutants. Taken together, this study indicates that ACA10/8 and BON1 physically interact on plasma membrane and function in the generation of cytosol calcium signatures that are critical for stomatal movement and impact plant immunity. PMID:28701352

The desert plant Phoenix dactylifera closes stomata via nitrate-regulated SLAC1 anion channel.

PubMed

Müller, Heike M; Schäfer, Nadine; Bauer, Hubert; Geiger, Dietmar; Lautner, Silke; Fromm, Jörg; Riederer, Markus; Bueno, Amauri; Nussbaumer, Thomas; Mayer, Klaus; Alquraishi, Saleh A; Alfarhan, Ahmed H; Neher, Erwin; Al-Rasheid, Khaled A S; Ache, Peter; Hedrich, Rainer

2017-10-01

Date palm Phoenix dactylifera is a desert crop well adapted to survive and produce fruits under extreme drought and heat. How are palms under such harsh environmental conditions able to limit transpirational water loss? Here, we analysed the cuticular waxes, stomata structure and function, and molecular biology of guard cells from P. dactylifera. To understand the stomatal response to the water stress phytohormone of the desert plant, we cloned the major elements necessary for guard cell fast abscisic acid (ABA) signalling and reconstituted this ABA signalosome in Xenopus oocytes. The PhoenixSLAC1-type anion channel is regulated by ABA kinase PdOST1. Energy-dispersive X-ray analysis (EDXA) demonstrated that date palm guard cells release chloride during stomatal closure. However, in Cl - medium, PdOST1 did not activate the desert plant anion channel PdSLAC1 per se. Only when nitrate was present at the extracellular face of the anion channel did the OST1-gated PdSLAC1 open, thus enabling chloride release. In the presence of nitrate, ABA enhanced and accelerated stomatal closure. Our findings indicate that, in date palm, the guard cell osmotic motor driving stomatal closure uses nitrate as the signal to open the major anion channel SLAC1. This initiates guard cell depolarization and the release of anions together with potassium. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Rapid hydraulic recovery in Eucalyptus pauciflora after drought: linkages between stem hydraulics and leaf gas exchange.

PubMed

Martorell, Sebastià; Diaz-Espejo, Antonio; Medrano, Hipólito; Ball, Marilyn C; Choat, Brendan

2014-03-01

In woody plants, photosynthetic capacity is closely linked to rates at which the plant hydraulic system can supply water to the leaf surface. Drought-induced embolism can cause sharp declines in xylem hydraulic conductivity that coincide with stomatal closure and reduced photosynthesis. Recovery of photosynthetic capacity after drought is dependent on restored xylem function, although few data exist to elucidate this coordination. We examined the dynamics of leaf gas exchange and xylem function in Eucalyptus pauciflora seedlings exposed to a cycle of severe water stress and recovery after re-watering. Stomatal closure and leaf turgor loss occurred at water potentials that delayed the extensive spread of embolism through the stem xylem. Stem hydraulic conductance recovered to control levels within 6 h after re-watering despite a severe drought treatment, suggesting an active mechanism embolism repair. However, stomatal conductance did not recover after 10 d of re-watering, effecting tighter control of transpiration post drought. The dynamics of recovery suggest that a combination of hydraulic and non-hydraulic factors influenced stomatal behaviour post drought. © 2013 John Wiley & Sons Ltd.

Movement of Abscisic Acid into the Apoplast in Response to Water Stress in Xanthium strumarium L.

PubMed

Cornish, K; Zeevaart, J A

1985-07-01

The effect of water stress on the redistribution of abcisic acid (ABA) in mature leaves of Xanthium strumarium L. was investigated using a pressure dehydration technique. In both turgid and stressed leaves, the ABA in the xylem exudate, the ;apoplastic' ABA, increased before ;bulk leaf' stress-induced ABA accumulation began. In the initially turgid leaves, the ABA level remained constant in both the apoplast and the leaf as a whole until wilting symptoms appeared. Following turgor loss, sufficient quantities of ABA moved into the apoplast to stimulate stomatal closure. Thus, the initial increase of apoplastic ABA may be relevant to the rapid stomatal closure seen in stressed leaves before their bulk leaf ABA levels rise.Following recovery from water stress, elevated levels of ABA remained in the apoplast after the bulk leaf contents had returned to their prestress values. This apoplastic ABA may retard stomatal reopening during the initial recovery period.

Stomatal Function Requires Pectin De-methyl-esterification of the Guard Cell Wall

DOE PAGES

Amsbury, Sam; Hunt, Lee; Elhaddad, Nagat; ...

2016-10-06

Stomatal opening and closure depends on changes in turgor pressure acting within guard cells to alter cell shape. The extent of these shape changes is limited by the mechanical properties of the cells, which will be largely dependent on the structure of the cell walls. Although it has long been observed that guard cells are anisotropic due to differential thickening and the orientation of cellulose microfibrils, our understanding of the composition of the cell wall that allows them to undergo repeated swelling and deflation remains surprisingly poor. Here, we show that the walls of guard cells are rich in un-esterified pectins.more » We identify a pectin methylesterase gene, PME6, which is highly expressed in guard cells and required for stomatal function. pme6-1 mutant guard cells have walls enriched in methyl-esterified pectin and show a decreased dynamic range in response to triggers of stomatal opening/closure, including elevated osmoticum, suggesting that abrogation of stomatal function reflects a mechanical change in the guard cell wall. Altered stomatal function leads to increased conductance and evaporative cooling, as well as decreased plant growth. The growth defect of the  pme6-1 mutant is rescued by maintaining the plants in elevated CO 2, substantiating gas exchange analyses, indicating that the mutant stomata can bestow an improved assimilation rate. Restoration of PME6 rescues guard cell wall pectin methyl-esterification status, stomatal function, and plant growth. Our results establish a link between gene expression in guard cells and their cell wall properties, with a corresponding effect on stomatal function and plant physiology.« less

Stomatal Function Requires Pectin De-methyl-esterification of the Guard Cell Wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amsbury, Sam; Hunt, Lee; Elhaddad, Nagat

Stomatal opening and closure depends on changes in turgor pressure acting within guard cells to alter cell shape. The extent of these shape changes is limited by the mechanical properties of the cells, which will be largely dependent on the structure of the cell walls. Although it has long been observed that guard cells are anisotropic due to differential thickening and the orientation of cellulose microfibrils, our understanding of the composition of the cell wall that allows them to undergo repeated swelling and deflation remains surprisingly poor. Here, we show that the walls of guard cells are rich in un-esterified pectins.more » We identify a pectin methylesterase gene, PME6, which is highly expressed in guard cells and required for stomatal function. pme6-1 mutant guard cells have walls enriched in methyl-esterified pectin and show a decreased dynamic range in response to triggers of stomatal opening/closure, including elevated osmoticum, suggesting that abrogation of stomatal function reflects a mechanical change in the guard cell wall. Altered stomatal function leads to increased conductance and evaporative cooling, as well as decreased plant growth. The growth defect of the  pme6-1 mutant is rescued by maintaining the plants in elevated CO 2, substantiating gas exchange analyses, indicating that the mutant stomata can bestow an improved assimilation rate. Restoration of PME6 rescues guard cell wall pectin methyl-esterification status, stomatal function, and plant growth. Our results establish a link between gene expression in guard cells and their cell wall properties, with a corresponding effect on stomatal function and plant physiology.« less

Stomatal Function Requires Pectin De-methyl-esterification of the Guard Cell Wall.

PubMed

Amsbury, Sam; Hunt, Lee; Elhaddad, Nagat; Baillie, Alice; Lundgren, Marjorie; Verhertbruggen, Yves; Scheller, Henrik V; Knox, J Paul; Fleming, Andrew J; Gray, Julie E

2016-11-07

Stomatal opening and closure depends on changes in turgor pressure acting within guard cells to alter cell shape [1]. The extent of these shape changes is limited by the mechanical properties of the cells, which will be largely dependent on the structure of the cell walls. Although it has long been observed that guard cells are anisotropic due to differential thickening and the orientation of cellulose microfibrils [2], our understanding of the composition of the cell wall that allows them to undergo repeated swelling and deflation remains surprisingly poor. Here, we show that the walls of guard cells are rich in un-esterified pectins. We identify a pectin methylesterase gene, PME6, which is highly expressed in guard cells and required for stomatal function. pme6-1 mutant guard cells have walls enriched in methyl-esterified pectin and show a decreased dynamic range in response to triggers of stomatal opening/closure, including elevated osmoticum, suggesting that abrogation of stomatal function reflects a mechanical change in the guard cell wall. Altered stomatal function leads to increased conductance and evaporative cooling, as well as decreased plant growth. The growth defect of the pme6-1 mutant is rescued by maintaining the plants in elevated CO 2 , substantiating gas exchange analyses, indicating that the mutant stomata can bestow an improved assimilation rate. Restoration of PME6 rescues guard cell wall pectin methyl-esterification status, stomatal function, and plant growth. Our results establish a link between gene expression in guard cells and their cell wall properties, with a corresponding effect on stomatal function and plant physiology. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Function of ABA in Stomatal Defense against Biotic and Drought Stresses

PubMed Central

Lim, Chae Woo; Baek, Woonhee; Jung, Jangho; Kim, Jung-Hyun; Lee, Sung Chul

2015-01-01

The plant hormone abscisic acid (ABA) regulates many key processes involved in plant development and adaptation to biotic and abiotic stresses. Under stress conditions, plants synthesize ABA in various organs and initiate defense mechanisms, such as the regulation of stomatal aperture and expression of defense-related genes conferring resistance to environmental stresses. The regulation of stomatal opening and closure is important to pathogen defense and control of transpirational water loss. Recent studies using a combination of approaches, including genetics, physiology, and molecular biology, have contributed considerably to our understanding of ABA signal transduction. A number of proteins associated with ABA signaling and responses—especially ABA receptors—have been identified. ABA signal transduction initiates signal perception by ABA receptors and transfer via downstream proteins, including protein kinases and phosphatases. In the present review, we focus on the function of ABA in stomatal defense against biotic and abiotic stresses, through analysis of each ABA signal component and the relationships of these components in the complex network of interactions. In particular, two ABA signal pathway models in response to biotic and abiotic stress were proposed, from stress signaling to stomatal closure, involving the pyrabactin resistance (PYR)/PYR-like (PYL) or regulatory component of ABA receptor (RCAR) family proteins, 2C-type protein phosphatases, and SnRK2-type protein kinases. PMID:26154766

The site of water stress governs the pattern of ABA synthesis and transport in peanut

PubMed Central

Hu, Bo; Cao, Jiajia; Ge, Kui; Li, Ling

2016-01-01

Abscisic acid (ABA) is one of the most important phytohormones involved in stress responses in plants. However, knowledge of the effect on ABA distribution and transport of water stress at different sites on the plant is limited. In this study, water stress imposed on peanut leaves or roots by treatment with PEG 6000 is termed “leaf stress” or “root stress”, respectively. Immunoenzyme localization technolony was first used to detect ABA distribution in peanut. Under root stress, ABA biosynthesis and distribution level were all more pronounced in root than in leaf. However, ABA transport and the ability to induce stomatal closure were still better in leaf than in root during root stress; However, ABA biosynthesis initially increased in leaf, then rapidly accumulated in the vascular cambium of leaves and induced stomatal closure under leaf stress; ABA produced in root tissues was also transported to leaf tissues to maintain stomatal closure. The vascular system was involved in the coordination and integration of this complex regulatory mechanism for ABA signal accumulation. Water stress subject to root or leaf results in different of ABA biosynthesis and transport ability that trigger stoma close in peanut. PMID:27694957

A chloroplast retrograde signal, 3’-phosphoadenosine 5’-phosphate, acts as a secondary messenger in abscisic acid signaling in stomatal closure and germination

PubMed Central

Pornsiriwong, Wannarat; Estavillo, Gonzalo M; Chan, Kai Xun; Tee, Estee E; Ganguly, Diep; Crisp, Peter A; Phua, Su Yin; Zhao, Chenchen; Qiu, Jiaen; Park, Jiyoung; Yong, Miing Tiem; Nisar, Nazia; Yadav, Arun Kumar; Schwessinger, Benjamin; Rathjen, John; Cazzonelli, Christopher I; Wilson, Philippa B; Gilliham, Matthew; Chen, Zhong-Hua; Pogson, Barry J

2017-01-01

Organelle-nuclear retrograde signaling regulates gene expression, but its roles in specialized cells and integration with hormonal signaling remain enigmatic. Here we show that the SAL1-PAP (3′-phosphoadenosine 5′- phosphate) retrograde pathway interacts with abscisic acid (ABA) signaling to regulate stomatal closure and seed germination in Arabidopsis. Genetically or exogenously manipulating PAP bypasses the canonical signaling components ABA Insensitive 1 (ABI1) and Open Stomata 1 (OST1); priming an alternative pathway that restores ABA-responsive gene expression, ROS bursts, ion channel function, stomatal closure and drought tolerance in ost1-2. PAP also inhibits wild type and abi1-1 seed germination by enhancing ABA sensitivity. PAP-XRN signaling interacts with ABA, ROS and Ca2+; up-regulating multiple ABA signaling components, including lowly-expressed Calcium Dependent Protein Kinases (CDPKs) capable of activating the anion channel SLAC1. Thus, PAP exhibits many secondary messenger attributes and exemplifies how retrograde signals can have broader roles in hormone signaling, allowing chloroplasts to fine-tune physiological responses. DOI: http://dx.doi.org/10.7554/eLife.23361.001 PMID:28323614

Observations on the Stomatal Control of NO2 Exchange.

NASA Astrophysics Data System (ADS)

Kesselmeier, J.; Chaparro-Suarez, I. G.; Meixner, F. X.

2005-12-01

Nitrogen oxides play a central role in tropospheric chemistry especially in the formation of tropospheric ozone, acid rain and hydroxyl radical as well as in CH4 and CO oxidation processes. NO2 can be assimilated and emitted by the plant leaves as well. We investigated the impact of the stomatal regulation with four tree species (Betula pendula, Fagus sylvatica, Quercus ilex und Pinus sylvestris) by exposure of leaves to the hormone abscisic acid inducing stomatal closure. The results showed that the NO2 uptake was strongly dependent on stomatal aperture. The uptake correlated linearly with stomatal (leaf) conductance in case of all four tree species investigated. In contrast an NO2 emission was observed with beech in the dark when stomata were basically closed.

Regulation of Stomatal Defense by Air Relative Humidity.

PubMed

Panchal, Shweta; Chitrakar, Reejana; Thompson, Blaine K; Obulareddy, Nisita; Roy, Debanjana; Hambright, W Sealy; Melotto, Maeli

2016-11-01

It has long been observed that environmental conditions play crucial roles in modulating immunity and disease in plants and animals. For instance, many bacterial plant disease outbreaks occur after periods of high humidity and rain. A critical step in bacterial infection is entry into the plant interior through wounds and natural openings, such as stomata, which are adjustable microscopic pores in the epidermal tissue. Several studies have shown that stomatal closure is an integral part of the plant immune response to reduce pathogen invasion. In this study, we found that high humidity can effectively compromise Pseudomonas syringae-triggered stomatal closure in both Phaseolus vulgaris and Arabidopsis (Arabidopsis thaliana), which is accompanied by early up-regulation of the jasmonic acid (JA) pathway and simultaneous down-regulation of salicylic acid (SA) pathway in guard cells. Furthermore, SA-dependent response, but not JA-dependent response, is faster in guard cells than in whole leaves, suggesting that the SA signaling in guard cells may be independent from other cell types. Thus, we conclude that high humidity, a well-known disease-promoting environmental condition, acts in part by suppressing stomatal defense and is linked to hormone signaling in guard cells. © 2016 American Society of Plant Biologists. All Rights Reserved.

Physiological Regulation of Stomatal Conductance in Boreal Forest Species: Do Species Differ and Does it Matter?

NASA Astrophysics Data System (ADS)

Berry, J. A.; Wolf, A.; Vygodskaya, N. N.

2004-12-01

Measurements of energy and water balance over Boreal forest ecosystems have generally shown very large ratios of sensible heat flux to latent heat flux (Bowen ratio) - especially on fine summer days. This strong control on evaporation at the plant scale can restrict precipitation and effect hydrometeorlogy at the regional scale. The large Bowen ratio is, in part, explained by the low maximum stomatal conductance of Boreal forest tree species and is probably related to their very low photosynthetic capacity. However, mid-day conductance can be much lower than expected on this basis and reflects the additional effect of a dynamic feedback system between stomatal conductance and the properties of the atmospheric boundary layer. Low stomatal conductance leads to a large sensible heat flux which, in turn, leads to a deeper, warmer and dryer atmospheric boundary layer and to a greater evaporative demand on the plant, causing the stomata close still more. Predicting the response of this non-linear system presents a major challenge. Physiological studies conducted in the Canadian Boreal forest show very large differences in the tendency of species to experience mid day stomatal closure. Jack pine was found to be quite susceptible while black spruce the most resistant to mid day stomatal closure. These species had very similar photosynthetic capacity (Vmax) and Ball-Berry stomatal sensitivity coefficients. Jack pine was, however, more sensitive to inhibition of photosynthesis by elevated temperatures and, as a consequence, stomata closed as temperature and the vapor pressure deficit increased during mid day. In contrast, black spruce was much less effected. These differences could have profound implications for simulating regional scale hydrometeorology over large areas dominated by monospecific stands in the NEESPI domain.

Movement of Abscisic Acid into the Apoplast in Response to Water Stress in Xanthium strumarium L. 1

PubMed Central

Cornish, Katrina; Zeevaart, Jan A. D.

1985-01-01

The effect of water stress on the redistribution of abcisic acid (ABA) in mature leaves of Xanthium strumarium L. was investigated using a pressure dehydration technique. In both turgid and stressed leaves, the ABA in the xylem exudate, the `apoplastic' ABA, increased before `bulk leaf' stress-induced ABA accumulation began. In the initially turgid leaves, the ABA level remained constant in both the apoplast and the leaf as a whole until wilting symptoms appeared. Following turgor loss, sufficient quantities of ABA moved into the apoplast to stimulate stomatal closure. Thus, the initial increase of apoplastic ABA may be relevant to the rapid stomatal closure seen in stressed leaves before their bulk leaf ABA levels rise. Following recovery from water stress, elevated levels of ABA remained in the apoplast after the bulk leaf contents had returned to their prestress values. This apoplastic ABA may retard stomatal reopening during the initial recovery period. PMID:16664294

Intracellular ca2+ stores could participate to abscisic acid-induced depolarization and stomatal closure in Arabidopsis thaliana

PubMed Central

Meimoun, Patrice; Vidal, Guillaume; Bohrer, Anne-Sophie; Lehner, Arnaud; Tran, Daniel; Briand, Joël; Bouteau, François

2009-01-01

In Arabidopsis thaliana cell suspension,abscisic acid (aBa) induces changes in cytosolic calcium concentration ([Ca2+]cyt) which are the trigger for aBa-induced plasma membrane anion current activation, H+-aTPase inhibition, and subsequent plasma membrane depolarization. In the present study, we took advantage of this model to analyze the implication of intracellular Ca2+ stores in aBa signal transduction through electrophysiological current measurements, cytosolic Ca2+ activity measurements with the apoaequorin Ca2+ reporter protein and external pH measurement. Intracellular Ca2+ stores involvement was determined by using specific inhibitors of CICR channels: the cADP-ribose/ryanodine receptor (Br-cADPR and dantrolene) and of the inositol trisphosphate receptor (U73122). In addition experiments were performed on epidermal strips of A. thaliana leaves to monitor stomatal closure in response to ABA in presence of the same pharmacology. Our data provide evidence that ryanodine receptor and inositol trisphosphate receptor could be involved in ABA-induced (1) Ca2+ release in the cytosol, (2) anion channel activation and H+-ATPase inhibition leading to plasma membrane depolarization and (3) stomatal closure. Intracellular Ca2+ release could thus contribute to the control of early events in the ABA signal transduction pathway in A. thaliana. PMID:19847112

Ozone-induced stomatal sluggishness changes carbon and water balance of temperate deciduous forests.

PubMed

Hoshika, Yasutomo; Katata, Genki; Deushi, Makoto; Watanabe, Makoto; Koike, Takayoshi; Paoletti, Elena

2015-05-06

Tropospheric ozone concentrations have increased by 60-100% in the Northern Hemisphere since the 19(th) century. The phytotoxic nature of ozone can impair forest productivity. In addition, ozone affects stomatal functions, by both favoring stomatal closure and impairing stomatal control. Ozone-induced stomatal sluggishness, i.e., a delay in stomatal responses to fluctuating stimuli, has the potential to change the carbon and water balance of forests. This effect has to be included in models for ozone risk assessment. Here we examine the effects of ozone-induced stomatal sluggishness on carbon assimilation and transpiration of temperate deciduous forests in the Northern Hemisphere in 2006-2009 by combining a detailed multi-layer land surface model and a global atmospheric chemistry model. An analysis of results by ozone FACE (Free-Air Controlled Exposure) experiments suggested that ozone-induced stomatal sluggishness can be incorporated into modelling based on a simple parameter (gmin, minimum stomatal conductance) which is used in the coupled photosynthesis-stomatal model. Our simulation showed that ozone can decrease water use efficiency, i.e., the ratio of net CO2 assimilation to transpiration, of temperate deciduous forests up to 20% when ozone-induced stomatal sluggishness is considered, and up to only 5% when the stomatal sluggishness is neglected.

Nitrogen dioxide (NO2) uptake by vegetation controlled by atmospheric concentrations and plant stomatal aperture

NASA Astrophysics Data System (ADS)

Chaparro-Suarez, I. G.; Meixner, F. X.; Kesselmeier, J.

2011-10-01

Nitrogen dioxide (NO2) exchange between the atmosphere and five European tree species was investigated in the laboratory using a dynamic branch enclosure system (consisting of two cuvettes) and a highly specific NO2 analyzer. NO2 measurements were performed with a sensitive gas phase chemiluminescence NO detector combined with a NO2 specific (photolytic) converter, both from Eco-Physics (Switzerland). This highly specific detection system excluded bias from other nitrogen compounds. Investigations were performed at two light intensities (Photosynthetic Active Radiation, PAR, 450 and 900 μmol m-2 s-1) and NO2 concentrations between 0 and 5 ppb. Ambient parameters (air temperature and relative humidity) were held constant. The data showed dominant NO2 uptake by the respective tree species under all conditions. The results did not confirm the existence of a compensation point within a 95% confidence level, though we cannot completely exclude emission of NO2 under very low atmospheric concentrations. Induced stomatal stricture, or total closure, by changing light conditions, as well as by application of the plant hormone ABA (Abscisic Acid) caused a corresponding decrease of NO2 uptake. No loss of NO2 to plant surfaces was observed under stomatal closure and species dependent differences in uptake rates could be clearly related to stomatal behavior.

Contrasting dynamics of leaf potential and gas exchange during progressive drought cycles and recovery in Amorpha fruticosa and Robinia pseudoacacia.

PubMed

Yan, Weiming; Zheng, Shuxia; Zhong, Yangquanwei; Shangguan, Zhouping

2017-06-30

Leaf gas exchange is closely associated with water relations; however, less attention has been given to this relationship over successive drought events. Dynamic changes in gas exchange and water potential in the seedlings of two woody species, Amorpha fruticosa and Robinia pseudoacacia, were monitored during recurrent drought. The pre-dawn leaf water potential declined in parallel with gas exchange in both species, and sharp declines in gas exchange occurred with decreasing water potential. A significant correlation between pre-dawn water potential and gas exchange was observed in both species and showed a right shift in R. pseudoacacia in the second drought. The results suggested that stomatal closure in early drought was mediated mainly by elevated foliar abscisic acid (ABA) in R. pseudoacacia, while a shift from ABA-regulated to leaf-water-potential-driven stomatal closure was observed in A. fruticosa. After re-watering, the pre-dawn water potential recovered quickly, whereas stomatal conductance did not fully recover from drought in R. pseudoacacia, which affected the ability to tightly control transpiration post-drought. The dynamics of recovery from drought suggest that stomatal behavior post-drought may be restricted mainly by hydraulic factors, but non-hydraulic factors may also be involved in R. pseudoacacia.

Effects of genetic manipulation of the activity of photorespiration on the redox state of photosystem I and its robustness against excess light stress under CO2-limited conditions in rice.

PubMed

Wada, Shinya; Suzuki, Yuji; Takagi, Daisuke; Miyake, Chikahiro; Makino, Amane

2018-05-14

Under CO 2 -limited conditions such as during stomatal closure, photorespiration is suggested to act as a sink for excess light energy and protect photosystem I (PSI) by oxidizing its reaction center chlorophyll P700. In this study, this issue was directly examined with rice (Oryza sativa L.) plants via genetic manipulation of the amount of Rubisco, which can be a limiting factor for photorespiration. At low [CO 2 ] of 5 Pa that mimicked stomatal closure condition, the activity of photorespiration in transgenic plants with decreased Rubisco content (RBCS-antisense plants) markedly decreased, whereas the activity in transgenic plants with overproduction of Rubisco (RBCS-sense plants) was similar to that in wild-type plants. Oxidation of P700 was enhanced at [CO 2 ] of 5 Pa in wild-type and RBCS-sense plants. PSI was not damaged by excess light stress induced by repetitive saturated pulse-light (rSP) in the presence of strong steady-state light. On the other hand, P700 was strongly reduced in RBCS-antisense plants at [CO 2 ] of 5 Pa. PSI was also damaged by rSP illumination. These results indicate that oxidation of P700 and the robustness of PSI against excess light stress are hampered by the decreased activity of photorespiration as a result of genetic manipulation of Rubisco content. It is also suggested that overproduction of Rubisco does not enhance photorespiration as well as CO 2 assimilation probably due to partial deactivation of Rubisco.

A novel-type phosphatidylinositol phosphate-interactive, Ca-binding protein PCaP1 in Arabidopsis thaliana: stable association with plasma membrane and partial involvement in stomata closure.

PubMed

Nagata, Chisako; Miwa, Chika; Tanaka, Natsuki; Kato, Mariko; Suito, Momoe; Tsuchihira, Ayako; Sato, Yori; Segami, Shoji; Maeshima, Masayoshi

2016-05-01

The Ca(2+)-binding protein-1 (PCaP1) of Arabidopsis thaliana is a new type protein that binds to phosphatidylinositol phosphates and Ca(2+)-calmodulin complex as well as free Ca(2+). Although biochemical properties, such as binding to ligands and N-myristoylation, have been revealed, the intracellular localization, tissue and cell specificity, integrity of membrane association and physiological roles of PCaP1 are unknown. We investigated the tissue and intracellular distribution of PCaP1 by using transgenic lines expressing PCaP1 linked with a green fluorescence protein (GFP) at the carboxyl terminus of PCaP1. GFP fluorescence was obviously detected in most tissues including root, stem, leaf and flower. In these tissues, PCaP1-GFP signal was observed predominantly in the plasma membrane even under physiological stress conditions but not in other organelles. The fluorescence was detected in the cytosol when the 25-residue N-terminal sequence was deleted from PCaP1 indicating essential contribution of N-myristoylation to the plasma membrane anchoring. Fluorescence intensity of PCaP1-GFP in roots was slightly decreased in seedlings grown in medium supplemented with high concentrations of iron for 1 week and increased in those grown with copper. In stomatal guard cells, PCaP1-GFP was strictly, specifically localized to the plasma membrane at the epidermal-cell side but not at the pore side. A T-DNA insertion mutant line of PCaP1 did not show marked phenotype in a life cycle except for well growth under high CO2 conditions. However, stomata of the mutant line did not close entirely even in high osmolarity, which usually induces stomata closure. These results suggest that PCaP1 is involved in the stomatal movement, especially closure process, in leaves and response to excessive copper in root and leaf as a mineral nutrient as a physiological role.

Overexpression of Grain Amaranth (Amaranthus hypochondriacus) AhERF or AhDOF Transcription Factors in Arabidopsis thaliana Increases Water Deficit- and Salt-Stress Tolerance, Respectively, via Contrasting Stress-Amelioration Mechanisms

PubMed Central

Massange-Sánchez, Julio A.; Palmeros-Suárez, Paola A.; Espitia-Rangel, Eduardo; Rodríguez-Arévalo, Isaac; Sánchez-Segura, Lino; Martínez-Gallardo, Norma A.; Alatorre-Cobos, Fulgencio; Tiessen, Axel; Délano-Frier, John P.

2016-01-01

Two grain amaranth transcription factor (TF) genes were overexpressed in Arabidopsis plants. The first, coding for a group VII ethylene response factor TF (i.e., AhERF-VII) conferred tolerance to water-deficit stress (WS) in transgenic Arabidopsis without affecting vegetative or reproductive growth. A significantly lower water-loss rate in detached leaves coupled to a reduced stomatal opening in leaves of plants subjected to WS was associated with this trait. WS tolerance was also associated with an increased antioxidant enzyme activity and the accumulation of putative stress-related secondary metabolites. However, microarray and GO data did not indicate an obvious correlation between WS tolerance, stomatal closure, and abscisic acid (ABA)-related signaling. This scenario suggested that stomatal closure during WS in these plants involved ABA-independent mechanisms, possibly involving reactive oxygen species (ROS). WS tolerance may have also involved other protective processes, such as those employed for methyl glyoxal detoxification. The second, coding for a class A and cluster I DNA binding with one finger TF (i.e., AhDof-AI) provided salt-stress (SS) tolerance with no evident fitness penalties. The lack of an obvious development-related phenotype contrasted with microarray and GO data showing an enrichment of categories and genes related to developmental processes, particularly flowering. SS tolerance also correlated with increased superoxide dismutase activity but not with augmented stomatal closure. Additionally, microarray and GO data indicated that, contrary to AhERF-VII, SS tolerance conferred by AhDof-AI in Arabidopsis involved ABA-dependent and ABA-independent stress amelioration mechanisms. PMID:27749893

Overexpression of OsTF1L, a rice HD-Zip transcription factor, promotes lignin biosynthesis and stomatal closure that improves drought tolerance.

PubMed

Bang, Seung Woon; Lee, Dong-Keun; Jung, Harin; Chung, Pil Joong; Kim, Youn Shic; Choi, Yang Do; Suh, Joo-Won; Kim, Ju-Kon

2018-05-21

Drought stress seriously impacts on plant development and productivity. Improvement of drought tolerance without yield penalty is a great challenge in crop biotechnology. Here, we report that the rice (Oryza sativa) homeodomain-leucine zipper transcription factor gene, OsTF1L (Oryza sativa transcription factor 1-like), is a key regulator of drought tolerance mechanisms. Overexpression of the OsTF1L in rice significantly increased drought tolerance at the vegetative stages of growth and promoted both effective photosynthesis and a reduction in the water loss rate under drought conditions. Importantly, the OsTF1L overexpressing plants showed a higher drought tolerance at the reproductive stage of growth with a higher grain yield than non-transgenic controls under field-drought conditions. Genome-wide analysis of OsTF1L overexpression plants revealed up-regulation of drought-inducible, stomatal movement and lignin biosynthetic genes. Overexpression of OsTF1L promoted accumulation of lignin in shoots, whereas the RNAi lines showed opposite patterns of lignin accumulation. OsTF1L is mainly expressed in outer cell layers including the epidermis, and the vasculature of the shoots, which coincides with areas of lignification. In addition, OsTF1L overexpression enhances stomatal closure under drought conditions resulted in drought tolerance. More importantly, OsTF1L directly bound to the promoters of lignin biosynthesis and drought-related genes involving poxN/PRX38, Nodulin protein, DHHC4, CASPL5B1 and AAA-type ATPase. Collectively, our results provide a new insight into the role of OsTF1L in enhancing drought tolerance through lignin biosynthesis and stomatal closure in rice. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Arabidopsis Histone Methylase CAU1/PRMT5/SKB1 Acts as an Epigenetic Suppressor of the Calcium Signaling Gene CAS to Mediate Stomatal Closure in Response to Extracellular Calcium[W

PubMed Central

Fu, Yan-Lei; Zhang, Guo-Bin; Lv, Xin-Fang; Guan, Yuan; Yi, Hong-Ying; Gong, Ji-Ming

2013-01-01

Elevations in extracellular calcium ([Ca2+]o) are known to stimulate cytosolic calcium ([Ca2+]cyt) oscillations to close stomata. However, the underlying mechanisms regulating this process remain largely to be determined. Here, through the functional characterization of the calcium underaccumulation mutant cau1, we report that the epigenetic regulation of CAS, a putative Ca2+ binding protein proposed to be an external Ca2+ sensor, is involved in this process. cau1 mutant plants display increased drought tolerance and stomatal closure. A mutation in CAU1 significantly increased the expression level of the calcium signaling gene CAS, and functional disruption of CAS abolished the enhanced drought tolerance and stomatal [Ca2+]o signaling in cau1. Map-based cloning revealed that CAU1 encodes the H4R3sme2 (for histone H4 Arg 3 with symmetric dimethylation)-type histone methylase protein arginine methytransferase5/Shk1 binding protein1. Chromatin immunoprecipitation assays showed that CAU1 binds to the CAS promoter and modulates the H4R3sme2-type histone methylation of the CAS chromatin. When exposed to elevated [Ca2+]o, the protein levels of CAU1 decreased and less CAU1 bound to the CAS promoter. In addition, the methylation level of H4R3sme2 decreased in the CAS chromatin. Together, these data suggest that in response to increases in [Ca2+]o, fewer CAU1 protein molecules bind to the CAS promoter, leading to decreased H4R3sme2 methylation and consequent derepression of the expression of CAS to mediate stomatal closure and drought tolerance. PMID:23943859

Greater efficiency of water use in poplar clones having a delayed response of mesophyll conductance to drought.

PubMed

Théroux Rancourt, Guillaume; Éthier, Gilbert; Pepin, Steeve

2015-02-01

Improvement of water use efficiency is a key objective to improve the sustainability of cultivated plants, especially fast growing species with high water consumption like poplar. It is well known that water use efficiency (WUE) varies considerably among poplar genotypes, and it was recently suggested that the use of the mesophyll-to-stomatal conductance ratio (gm/gs) would be an appropriate trait to improve WUE. The responses of 7-week-old cuttings of four hybrid poplar clones and one native Balsam poplar (Populus balsamifera L.) to a water stress-recovery cycle were examined to evaluate the relation between the gm/gs ratio and transpiration efficiency (TE), a leaf-level component of WUE. A contrasting gs response to water stress was observed among the five clones, from stomatal closure early on during soil drying up to limited closure in Balsam poplar. However in the hybrids, the decline in gm was consistently delayed by a few days compared with gs. Moreover, in the most water use-efficient hybrids, the recovery following rehydration occurred faster for gm than for gs. Thus, the delay in the response of gm to drought and its faster recovery upon rewatering increased the gm/gs of the hybrids and this ratio scaled positively with TE. Our results support the use of the gm/gs ratio to select genotypes with improved WUE, and the notion that breeding strategies focusing mainly on stomatal responses to soil drying should also look for a strong curvilinearity between net carbon assimilation rate and gs, the indication of a significant increase in gm/gs in the earlier stages of stomatal closure. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Tomato–Pseudomonas syringae interactions under elevated CO2 concentration: the role of stomata

PubMed Central

Li, Xin; Sun, Zenghui; Shao, Shujun; Zhang, Shuai; Ahammed, Golam Jalal; Zhang, Guanqun; Jiang, Yuping; Zhou, Jie; Xia, Xiaojian; Zhou, Yanhong; Yu, Jingquan; Shi, Kai

2015-01-01

Increasing atmospheric CO2 concentrations ([CO2]) in agricultural and natural ecosystems is known to reduce plant stomatal opening, but it is unclear whether these CO2-induced stomatal alterations are associated with foliar pathogen infections. In this study, tomato plants were grown under ambient and elevated [CO2] and inoculated with Pseudomonas syringae pv. tomato strain DC3000, a strain that is virulent on tomato plants. We found that elevated [CO2] enhanced tomato defence against P. syringae. Scanning electron microscopy analysis revealed that stomatal aperture of elevated [CO2] plants was considerably smaller than their ambient counterparts, which affected the behaviour of P. syringae bacteria on the upper surface of epidermal peels. Pharmacological experiments revealed that nitric oxide (NO) played a role in elevated [CO2]-induced stomatal closure. Silencing key genes involved in NO generation and stomatal closing, nitrate reductase (NR) and guard cell slow-type anion channel 1 (SLAC1), blocked elevated [CO2]-induced stomatal closure and resulted in significant increases in P. syringae infection. However, the SLAC1-silenced plants, but not the NR-silenced plants, still had significantly higher defence under elevated [CO2] compared with plants treated with ambient [CO2]. Similar results were obtained when the stomata-limiting factor for P. syringae entry was excluded by syringe infiltration inoculation. These results indicate that elevated [CO2] induces defence against P. syringae in tomato plants, not only by reducing the stomata-mediated entry of P. syringae but also by invoking a stomata-independent pathway to counteract P. syringae. This information is valuable for designing proper strategies against bacterial pathogens under changing agricultural and natural ecosystems. PMID:25336683

Chickpea transcription factor CaTLP1 interacts with protein kinases, modulates ROS accumulation and promotes ABA-mediated stomatal closure

PubMed Central

Wardhan, Vijay; Pandey, Aarti; Chakraborty, Subhra; Chakraborty, Niranjan

2016-01-01

Tubby and Tubby-like proteins (TLPs), in mammals, play critical roles in neural development, while its function in plants is largely unknown. We previously demonstrated that the chickpea TLP, CaTLP1, participates in osmotic stress response and might be associated with ABA-dependent network. However, how CaTLP1 is connected to ABA signaling remains unclear. The CaTLP1 was found to be engaged in ABA-mediated gene expression and stomatal closure. Complementation of the yeast yap1 mutant with CaTLP1 revealed its role in ROS scavenging. Furthermore, complementation of Arabidopsis attlp2 mutant displayed enhanced stress tolerance, indicating the functional conservation of TLPs across the species. The presence of ABA-responsive element along with other motifs in the proximal promoter regions of TLPs firmly established their involvement in stress signalling pathways. The CaTLP1 promoter driven GUS expression was restricted to the vegetative organs, especially stem and rosette leaves. Global protein expression profiling of wild-type, attlp2 and complemented Arabidopsis plants revealed 95 differentially expressed proteins, presumably involved in maintaining physiological and biological processes under dehydration. Immunoprecipitation assay revealed that protein kinases are most likely to interact with CaTLP1. This study provides the first demonstration that the TLPs act as module for ABA-mediated stomatal closure possibly via interaction with protein kinase. PMID:27934866

Regulation of the calcium-sensing receptor in both stomatal movement and photosynthetic electron transport is crucial for water use efficiency and drought tolerance in Arabidopsis.

PubMed

Wang, Wen-Hua; Chen, Juan; Liu, Ting-Wu; Chen, Juan; Han, Ai-Dong; Simon, Martin; Dong, Xue-Jun; He, Jun-Xian; Zheng, Hai-Lei

2014-01-01

Production per amount of water used (water use efficiency, WUE) is closely correlated with drought tolerance. Although stomatal aperture can regulate WUE, the underlying molecular mechanisms are still unclear. Previous reports revealed that stomatal closure was inhibited in the calcium-sensing receptor (CAS) antisense line of Arabidopsis (CASas). Here it is shown that decreased drought tolerance and WUE of CASas was associated with higher stomatal conductance due to improper regulation of stomatal aperture, rather than any change of stomatal density. CASas plants also had a lower CO2 assimilation rate that was attributed to a lower photosynthetic electron transport rate, leading to higher chlorophyll fluorescence. Gene co-expression combined with analyses of chlorophyll content and transcription levels of photosynthesis-related genes indicate that CAS is involved in the formation of the photosynthetic electron transport system. These data suggest that CAS regulates transpiration and optimizes photosynthesis by playing important roles in stomatal movement and formation of photosynthetic electron transport, thereby regulating WUE and drought tolerance.

Nuclear-localized AtHSPR links abscisic acid-dependent salt tolerance and antioxidant defense in Arabidopsis.

PubMed

Yang, Tao; Zhang, Liang; Hao, Hongyan; Zhang, Peng; Zhu, Haowei; Cheng, Wei; Wang, Yongli; Wang, Xinyu; Wang, Chongying

2015-12-01

Salt stress from soil or irrigation water limits plant growth. A T-DNA insertion mutant in C24, named athspr (Arabidopsis thaliana heat shock protein-related), showed several phenotypes, including reduced organ size and enhanced sensitivity to environmental cues. The athspr mutant is severely impaired under salinity levels at which wild-type (WT) plants grow normally. AtHSPR encodes a nuclear-localized protein with ATPase activity, and its expression was enhanced by high salinity and abscisic acid (ABA). Overexpression (OE) of AtHSPR significantly enhanced tolerance to salt stress by increasing the activities of the antioxidant system and by maintaining K(+) /Na(+) homeostasis. Quantitative RT-PCR analyses showed that OE of AtHSPR increased the expression of ABA/stress-responsive, salt overly sensitive (SOS)-related and antioxidant-related genes. In addition, ABA content was reduced in athspr plants with or without salt stress, and exogenous ABA restored WT-like salt tolerance to athspr plants. athspr exhibited increased leaf stomatal density and stomatal index, slower ABA-induced stomatal closure and reduced drought tolerance relative to the WT. AtHSPR OE enhanced drought tolerance by reducing leaf water loss and stomatal aperture. Transcript profiling in athspr showed a differential salt-stress response for genes involved in accumulation of reactive oxygen species (ROS), ABA signaling, cell death, stress response and photosynthesis. Taken together, our results suggested that AtHSPR is involved in salt tolerance in Arabidopsis through modulation of ROS levels, ABA-dependent stomatal closure, photosynthesis and K(+) /Na(+) homeostasis. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Unraveling the Effects of Plant Hydraulics on Stomatal Closure during Water Stress in Walnut

PubMed Central

Cochard, Hervé; Coll, Lluis; Le Roux, Xavier; Améglio, Thierry

2002-01-01

The objectives of the study were to identify the relevant hydraulic parameters associated with stomatal regulation during water stress and to test the hypothesis of a stomatal control of xylem embolism in walnut (Juglans regia × nigra) trees. The hydraulic characteristics of the sap pathway were experimentally altered with different methods to alter plant transpiration (Eplant) and stomatal conductance (gs). Potted trees were exposed to a soil water depletion to alter soil water potential (Ψsoil), soil resistance (Rsoil), and root hydraulic resistances (Rroot). Soil temperature was changed to alter Rroot alone. Embolism was created in the trunk to increase shoot resistance (Rshoot). Stomata closed in response to these stresses with the effect of maintaining the water pressure in the leaf rachis xylem (Prachis) above −1.4 MPa and the leaf water potential (Ψleaf) above −1.6 MPa. The same dependence of Eplant and gs on Prachis or Ψleaf was always observed. This suggested that stomata were not responding to changes in Ψsoil, Rsoil, Rroot, or Rshoot per se but rather to their impact on Prachis and/or Ψleaf. Leaf rachis was the most vulnerable organ, with a threshold Prachis for embolism induction of −1.4 MPa. The minimum Ψleaf values corresponded to leaf turgor loss point. This suggested that stomata are responding to leaf water status as determined by transpiration rate and plant hydraulics and that Prachis might be the physiological parameter regulated by stomatal closure during water stress, which would have the effect of preventing extensive developments of cavitation during water stress. PMID:11788773

Species climate range influences hydraulic and stomatal traits in Eucalyptus species.

PubMed

Bourne, Aimee E; Creek, Danielle; Peters, Jennifer M R; Ellsworth, David S; Choat, Brendan

2017-07-01

Plant hydraulic traits influence the capacity of species to grow and survive in water-limited environments, but their comparative study at a common site has been limited. The primary aim of this study was to determine whether selective pressures on species originating in drought-prone environments constrain hydraulic traits among related species grown under common conditions. Leaf tissue water relations, xylem anatomy, stomatal behaviour and vulnerability to drought-induced embolism were measured on six Eucalyptus species growing in a common garden to determine whether these traits were related to current species climate range and to understand linkages between the traits. Hydraulically weighted xylem vessel diameter, leaf turgor loss point, the water potential at stomatal closure and vulnerability to drought-induced embolism were significantly ( P < 0·05) correlated with climate parameters from the species range. There was a co-ordination between stem and leaf parameters with the water potential at turgor loss, 12 % loss of conductivity and the point of stomatal closure significantly correlated. The correlation of hydraulic, stomatal and anatomical traits with climate variables from the species' original ranges suggests that these traits are genetically constrained. The conservative nature of xylem traits in Eucalyptus trees has important implications for the limits of species responses to changing environmental conditions and thus for species survival and distribution into the future, and yields new information for physiological models. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Root respiratory burst oxidase homologue-dependent H2O2 production confers salt tolerance on a grafted cucumber by controlling Na+ exclusion and stomatal closure

PubMed Central

Niu, Mengliang; Huang, Yuan; Sun, Shitao; Sun, Jingyu; Cao, Haishun; Shabala, Sergey

2018-01-01

Abstract Plant salt tolerance can be improved by grafting onto salt-tolerant rootstocks. However, the underlying signaling mechanisms behind this phenomenon remain largely unknown. To address this issue, we used a range of physiological and molecular techniques to study responses of self-grafted and pumpkin-grafted cucumber plants exposed to 75 mM NaCl stress. Pumpkin grafting significantly increased the salt tolerance of cucumber plants, as revealed by higher plant dry weight, chlorophyll content and photochemical efficiency (Fv/Fm), and lower leaf Na+ content. Salinity stress resulted in a sharp increase in H2O2 production, reaching a peak 3 h after salt treatment in the pumpkin-grafted cucumber. This enhancement was accompanied by elevated relative expression of respiratory burst oxidase homologue (RBOH) genes RbohD and RbohF and a higher NADPH oxidase activity. However, this increase was much delayed in the self-grafted plants, and the difference between the two grafting combinations disappeared after 24 h. The decreased leaf Na+ content of pumpkin-grafted plants was achieved by higher Na+ exclusion in roots, which was driven by the Na+/H+ antiporter energized by the plasma membrane H+-ATPase, as evidenced by the higher plasma membrane H+-ATPase activity and higher transcript levels for PMA and SOS1. In addition, early stomatal closure was also observed in the pumpkin-grafted cucumber plants, reducing water loss and maintaining the plant’s hydration status. When pumpkin-grafted plants were pretreated with an NADPH oxidase inhibitor, diphenylene iodonium (DPI), the H2O2 level decreased significantly, to the level found in self-grafted plants, resulting in the loss of the salt tolerance. Inhibition of the NADPH oxidase-mediated H2O2 signaling in the root also abolished a rapid stomatal closure in the pumpkin-grafted plants. We concluded that the pumpkin-grafted cucumber plants increase their salt tolerance via a mechanism involving the root-sourced respiratory burst oxidase homologue-dependent H2O2 production, which enhances Na+ exclusion from the root and promotes an early stomatal closure. PMID:29145593

Surviving a Dry Future: Abscisic Acid (ABA)-Mediated Plant Mechanisms for Conserving Water under Low Humidity

PubMed Central

McAdam, Scott A. M.

2017-01-01

Angiosperms are able to respond rapidly to the first sign of dry conditions, a decrease in air humidity, more accurately described as an increase in the vapor pressure deficit between the leaf and the atmosphere (VPD), by abscisic acid (ABA)-mediated stomatal closure. The genes underlying this response offer valuable candidates for targeted selection of crop varieties with improved drought tolerance, a critical goal for current plant breeding programs, to maximize crop production in drier and increasingly marginalized environments, and meet the demands of a growing population in the face of a changing climate. Here, we review current understanding of the genetic mechanisms underpinning ABA-mediated stomatal closure, a key means for conserving water under dry conditions, examine how these mechanisms evolved, and discuss what remains to be investigated. PMID:29113039

On the interactions among tropospheric ozone levels and typical environmental stresses challenging Mediterranean crops.

PubMed

Fagnano, Massimo; Maggio, Albino

2018-03-01

The main environmental stresses of Italian croplands are discussed in relation to their interactions with ozone effects on crops. Water deficit and salinization are frequent in Mediterranean environments during spring-summer causing a decrease of soil water potential and water uptake by roots and consequently stomatal closure. These stresses also stimulate secondary metabolism and antioxidant accumulation, which also serves as a stress protection mechanism. High concentrations of tropospheric ozone are common all over Italy during the spring-summer season. Ozone injuries to vegetation are related to its penetration into plant tissues, mostly via stomatal uptake, rather than to tropospheric concentrations per se. In several crops, closure of stomata due to drought/salinization reduces ozone entering into leaf tissues and counteracts possible ozone damages. Furthermore, the stimulation of antioxidant synthesis as a response to environmental stresses can represent a further protection factor from ozone injuries for Mediterranean crops.The co-existence of stress-induced stomatal closure and high ozone levels during spring-summer in Mediterranean environments implies that models that do not take into account physiological responses of crops to drought and salinity stress may overestimate ozone damages when stress responses overlap with seasonal ozone peaks. The shift from concentration-based to flux-based approaches has improved the accuracy of models to assess ozone effects on agricultural crops. It is, however, necessary to further refine the flux concept with respect to the plant abiotic stress defense capacity that can differ among genotypes, climatic conditions, and physiological states.

ABA signaling in guard cells entails a dynamic protein-protein interaction relay from the PYL-RCAR family receptors to ion channels.

PubMed

Lee, Sung Chul; Lim, Chae Woo; Lan, Wenzhi; He, Kai; Luan, Sheng

2013-03-01

Plant hormone abscisic acid (ABA) serves as an integrator of environmental stresses such as drought to trigger stomatal closure by regulating specific ion channels in guard cells. We previously reported that SLAC1, an outward anion channel required for stomatal closure, was regulated via reversible protein phosphorylation events involving ABA signaling components, including protein phosphatase 2C members and a SnRK2-type kinase (OST1). In this study, we reconstituted the ABA signaling pathway as a protein-protein interaction relay from the PYL/RCAR-type receptors, to the PP2C-SnRK2 phosphatase-kinase pairs, to the ion channel SLAC1. The ABA receptors interacted with and inhibited PP2C phosphatase activity against the SnRK2-type kinase, releasing active SnRK2 kinase to phosphorylate, and activate the SLAC1 channel, leading to reduced guard cell turgor and stomatal closure. Both yeast two-hybrid and bimolecular fluorescence complementation assays were used to verify the interactions among the components in the pathway. These biochemical assays demonstrated activity modifications of phosphatases and kinases by their interaction partners. The SLAC1 channel activity was used as an endpoint readout for the strength of the signaling pathway, depending on the presence of different combinations of signaling components. Further study using transgenic plants overexpressing one of the ABA receptors demonstrated that changing the relative level of interacting partners would change ABA sensitivity.

A Xanthomonas oryzae pv. oryzae effector, XopR, associates with receptor-like cytoplasmic kinases and suppresses PAMP-triggered stomatal closure.

PubMed

Wang, Shuangfeng; Sun, Jianhang; Fan, Fenggui; Tan, Zhaoyun; Zou, Yanmin; Lu, Dongping

2016-09-01

Receptor-like kinases (RLKs) play important roles in plant immunity signaling; thus, many are hijacked by pathogen effectors to promote successful pathogenesis. Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice leaf blight disease. The strain PXO99A has 18 non-TAL (transcription activation-like) effectors; however, their mechanisms of action and host target proteins remain largely unknown. Although the effector XopR from the Xoo strain MAFF311018 was shown to suppress PAMP-triggered immune responses in Arabidopsis, its target has not yet been identified. Here, we show that PXO99A XopR interacts with BIK1 at the plasma membrane. BIK1 is a receptor-like cytoplasmic kinase (RLCK) belonging to the RLK family of proteins and mediates PAMP-triggered stomatal immunity. In turn, BIK1 phosphorylates XopR. Furthermore, XopR suppresses PAMP-triggered stomatal closure in transgenic Arabidopsis expressing XopR. In addition, XopR is able to associate with RLCKs other than BIK1. These results suggest that XopR likely suppresses plant immunity by targeting BIK1 and other RLCKs.

Roles of a maize phytochrome-interacting factors protein ZmPIF3 in regulation of drought stress responses by controlling stomatal closure in transgenic rice without yield penalty.

PubMed

Gao, Yong; Wu, Meiqin; Zhang, Menjiao; Jiang, Wei; Liang, Enxing; Zhang, Dongping; Zhang, Changquan; Xiao, Ning; Chen, Jianmin

2018-06-05

ZmPIF3 plays an important role in ABA-mediated regulation of stomatal closure in the control of water loss, and can improve both drought tolerance and did not affect the grain yield in the transgenic rice. Phytochrome-interacting factors (PIFs) are a subfamily of basic helix-loop-helix (bHLH) transcription factors and play important roles in regulating plant growth and development. In our previous study, overexpression of a maize PIFs family gene, ZmPIF3, improved drought tolerance in transgenic rice. In this study, measurement of water loss rate, transpiration rate, stomatal conductance, guard cell aperture, density and length of ZmPIF3 transgenic plants showed that ZmPIF3 can enhance water-saving and drought-resistance by decreasing stomatal aperture and reducing transpiration in both transgenic rice and transgenic Arabidopsis. Scrutiny of sensitivity to ABA showed that ZmPIF3 transgenic rice was hypersensitive to ABA, while the endogenous ABA level was not significantly changed. These results indicate that ZmPIF3 plays a major role in the ABA signaling pathway. In addition, DGE results further suggest that ZmPIF3 participates in the ABA signaling pathway and regulates stomatal aperture in rice. Comparison analysis of the phenotype, physiology, and transcriptome of ZmPIF3 transgenic rice compared to control plants further suggests that ZmPIF3 is a positive regulator of ABA signaling and enhances water-saving and drought-resistance traits by reducing stomatal openings to control water loss. Moreover, investigation of the agronomic traits of ZmPIF3 transgenic rice from four cultivating seasons showed that ZmPIF3 expression increased the tiller and panicle number and did not affect the grain yield in the transgenic rice. These results demonstrate that ZmPIF3 is a promising candidate gene in the transgenic breeding of water-saving and drought-resistant rice plants and crop improvement.

Optimal plant water use across temporal scales: bridging eco-hydrological theories and plant eco-physiological responses

NASA Astrophysics Data System (ADS)

Manzoni, S.; Vico, G.; Palmroth, S.; Katul, G. G.; Porporato, A. M.

2013-12-01

In terrestrial ecosystems, plant photosynthesis occurs at the expense of water losses through stomata, thus creating an inherent hydrologic constrain to carbon (C) gains and productivity. While such a constraint cannot be overcome, evolution has led to a number of adaptations that allow plants to thrive under highly variable and often limiting water availability. It may be hypothesized that these adaptations are optimal and allow maximum C gain for a given water availability. A corollary hypothesis is that these adaptations manifest themselves as coordination between the leaf photosynthetic machinery and the plant hydraulic system. This coordination leads to functional relations between the mean hydrologic state, plant hydraulic traits, and photosynthetic parameters that can be used as bridge across temporal scales. Here, optimality theories describing the behavior of stomata and plant morphological features in a fluctuating soil moisture environment are proposed. The overarching goal is to explain observed global patterns of plant water use and their ecological and biogeochemical consequences. The problem is initially framed as an optimal control problem of stomatal closure during drought of a given duration, where maximizing the total photosynthesis under limited and diminishing water availability is the objective function. Analytical solutions show that commonly used transpiration models (in which stomatal conductance is assumed to depend on soil moisture) are particular solutions emerging from the optimal control problem. Relations between stomatal conductance, vapor pressure deficit, and atmospheric CO2 are also obtained without any a priori assumptions under this framework. Second, the temporal scales of the model are expanded by explicitly considering the stochasticity of rainfall. In this context, the optimal control problem becomes a maximization problem for the mean photosynthetic rate. Results show that to achieve maximum C gains under these unpredictable rainfall conditions, plant hydraulic traits (xylem and stomatal response to water availability) and morphological features (leaf and sapwood areas) must be coordinated - thus providing an ecohydrological interpretation of observed coordination (or homeostasis) among hydraulic traits. Moreover, the combinations of hydraulic traits and responses to drought that are optimal are found to depend on both total rainfall and its distribution during the growing season. Both drier conditions and more intense rainfall events interspaced by longer dry periods favor plants with high resistance to cavitation and delayed stomatal closure as soils dry. In contrast, plants in mesic conditions benefit from cavitation prevention through earlier stomatal closure. The proposed ecohydrological optimality criteria can be used as analytical tools to interpret variability in plant water use and predict trends in plant productivity and species composition under future climates.

Daily changes in VPD during leaf development in high air humidity increase the stomatal responsiveness to darkness and dry air.

PubMed

Arve, Louise E; Kruse, Ole Mathis Opstad; Tanino, Karen K; Olsen, Jorunn E; Futsæther, Cecilia; Torre, Sissel

2017-04-01

Previous studies have shown that plants developed under high relative air humidity (RH>85%) develop malfunctioning stomata and therefor have increased transpiration and reduced desiccation tolerance when transferred to lower RH conditions and darkness. In this study, plants developed at high RH were exposed to daily VPD fluctuations created by changes in temperature and/or RH to evaluate the potential improvements in stomatal functioning. Daily periods with an 11°C temperature increase and consequently a VPD increase (vpd: 0.36-2.37KPa) reduced the stomatal apertures and improved the stomatal functionality and desiccation tolerance of the rosette plant Arabidopsis thaliana. A similar experiment was performed with only a 4°C temperature increase and/or a RH decrease on tomato. The results showed that a daily change in VPD (vpd: 0.36-1.43KPa) also resulted in improved stomatal responsiveness and decreased water usage during growth. In tomato, the most effective treatment to increase the stomatal responsiveness to darkness as a signal for closure was daily changes in RH without a temperature increase. Copyright © 2017 Elsevier GmbH. All rights reserved.

Combined Effects of Ozone and Drought on the Physiology and Membrane Lipids of Two Cowpea (Vigna unguiculata (L.) Walp) Cultivars.

PubMed

Rebouças, Deborah Moura; De Sousa, Yuri Maia; Bagard, Matthieu; Costa, Jose Helio; Jolivet, Yves; De Melo, Dirce Fernandes; Repellin, Anne

2017-03-03

The interactive effects of drought and ozone on the physiology and leaf membrane lipid content, composition and metabolism of cowpea (Vigna unguiculata (L.) Walp.) were investigated in two cultivars (EPACE-1 and IT83-D) grown under controlled conditions. The drought treatment (three-week water deprivation) did not cause leaf injury but restricted growth through stomatal closure. In contrast, the short-term ozone treatment (130 ppb 12 h daily during 14 day) had a limited impact at the whole-plant level but caused leaf injury, hydrogen peroxide accumulation and galactolipid degradation. These effects were stronger in the IT83-D cultivar, which also showed specific ozone responses such as a higher digalactosyl-diacylglycerol (DGDG):monogalactosyldiacylglycerol (MGDG) ratio and the coordinated up-regulation of DGDG synthase (VuDGD2) and ω-3 fatty acid desaturase 8 (VuFAD8) genes, suggesting that membrane remodeling occurred under ozone stress in the sensitive cultivar. When stresses were combined, ozone did not modify the stomatal response to drought and the observed effects on whole-plant physiology were essentially the same as when drought was applied alone. Conversely, the drought-induced stomatal closure appeared to alleviate ozone effects through the reduction of ozone uptake.

Combined Effects of Ozone and Drought on the Physiology and Membrane Lipids of Two Cowpea (Vigna unguiculata (L.) Walp) Cultivars

PubMed Central

Moura Rebouças, Deborah; Maia De Sousa, Yuri; Bagard, Matthieu; Costa, Jose Helio; Jolivet, Yves; Fernandes De Melo, Dirce; Repellin, Anne

2017-01-01

The interactive effects of drought and ozone on the physiology and leaf membrane lipid content, composition and metabolism of cowpea (Vigna unguiculata (L.) Walp.) were investigated in two cultivars (EPACE-1 and IT83-D) grown under controlled conditions. The drought treatment (three-week water deprivation) did not cause leaf injury but restricted growth through stomatal closure. In contrast, the short-term ozone treatment (130 ppb 12 h daily during 14 day) had a limited impact at the whole-plant level but caused leaf injury, hydrogen peroxide accumulation and galactolipid degradation. These effects were stronger in the IT83-D cultivar, which also showed specific ozone responses such as a higher digalactosyl-diacylglycerol (DGDG):monogalactosyl-diacylglycerol (MGDG) ratio and the coordinated up-regulation of DGDG synthase (VuDGD2) and ω-3 fatty acid desaturase 8 (VuFAD8) genes, suggesting that membrane remodeling occurred under ozone stress in the sensitive cultivar. When stresses were combined, ozone did not modify the stomatal response to drought and the observed effects on whole-plant physiology were essentially the same as when drought was applied alone. Conversely, the drought-induced stomatal closure appeared to alleviate ozone effects through the reduction of ozone uptake. PMID:28273829

High temperature causes negative whole-plant carbon balance under mild drought.

PubMed

Zhao, Junbin; Hartmann, Henrik; Trumbore, Susan; Ziegler, Waldemar; Zhang, Yiping

2013-10-01

Theoretically, progressive drought can force trees into negative carbon (C) balance by reducing stomatal conductance to prevent water loss, which also decreases C assimilation. At higher temperatures, negative C balance should be initiated at higher soil moisture because of increased respiratory demand and earlier stomatal closure. Few data are available on how these theoretical relationships integrate over the whole plant. We exposed Thuja occidentalis to progressive drought under three temperature conditions (15, 25, and 35°C), and measured C and water fluxes using a whole-tree chamber design. High transpiration rates at higher temperatures led to a rapid decline in soil moisture. During the progressive drought, soil moisture-driven changes in photosynthesis had a greater impact on the whole-plant C balance than respiration. The soil moisture content at which whole-plant C balance became negative increased with temperature, mainly as a result of higher respiration rates and an earlier onset of stomatal closure under a warmer condition. Our results suggest that the effect of drought on whole-plant C balance is highly temperature-dependent. High temperature causes a negative C balance even under mild drought and may increase the risk of C starvation. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

The tomato mutant ars1 (altered response to salt stress 1) identifies an R1-type MYB transcription factor involved in stomatal closure under salt acclimation.

PubMed

Campos, Juan F; Cara, Beatriz; Pérez-Martín, Fernando; Pineda, Benito; Egea, Isabel; Flores, Francisco B; Fernandez-Garcia, Nieves; Capel, Juan; Moreno, Vicente; Angosto, Trinidad; Lozano, Rafael; Bolarin, Maria C

2016-06-01

A screening under salt stress conditions of a T-DNA mutant collection of tomato (Solanum lycopersicum L.) led to the identification of the altered response to salt stress 1 (ars1) mutant, which showed a salt-sensitive phenotype. Genetic analysis of the ars1 mutation revealed that a single T-DNA insertion in the ARS1 gene was responsible of the mutant phenotype. ARS1 coded for an R1-MYB type transcription factor and its expression was induced by salinity in leaves. The mutant reduced fruit yield under salt acclimation while in the absence of stress the disruption of ARS1 did not affect this agronomic trait. The stomatal behaviour of ars1 mutant leaves induced higher Na(+) accumulation via the transpiration stream, as the decreases of stomatal conductance and transpiration rate induced by salt stress were markedly lower in the mutant plants. Moreover, the mutation affected stomatal closure in a response mediated by abscisic acid (ABA). The characterization of tomato transgenic lines silencing and overexpressing ARS1 corroborates the role of the gene in regulating the water loss via transpiration under salinity. Together, our results show that ARS1 tomato gene contributes to reduce transpirational water loss under salt stress. Finally, this gene could be interesting for tomato molecular breeding, because its manipulation could lead to improved stress tolerance without yield penalty under optimal culture conditions. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

A new discrete dynamic model of ABA-induced stomatal closure predicts key feedback loops

PubMed Central

Acharya, Biswa R.; Jeon, Byeong Wook; Zañudo, Jorge G. T.; Zhu, Mengmeng; Osman, Karim; Assmann, Sarah M.

2017-01-01

Stomata, microscopic pores in leaf surfaces through which water loss and carbon dioxide uptake occur, are closed in response to drought by the phytohormone abscisic acid (ABA). This process is vital for drought tolerance and has been the topic of extensive experimental investigation in the last decades. Although a core signaling chain has been elucidated consisting of ABA binding to receptors, which alleviates negative regulation by protein phosphatases 2C (PP2Cs) of the protein kinase OPEN STOMATA 1 (OST1) and ultimately results in activation of anion channels, osmotic water loss, and stomatal closure, over 70 additional components have been identified, yet their relationships with each other and the core components are poorly elucidated. We integrated and processed hundreds of disparate observations regarding ABA signal transduction responses underlying stomatal closure into a network of 84 nodes and 156 edges and, as a result, established those relationships, including identification of a 36-node, strongly connected (feedback-rich) component as well as its in- and out-components. The network’s domination by a feedback-rich component may reflect a general feature of rapid signaling events. We developed a discrete dynamic model of this network and elucidated the effects of ABA plus knockout or constitutive activity of 79 nodes on both the outcome of the system (closure) and the status of all internal nodes. The model, with more than 1024 system states, is far from fully determined by the available data, yet model results agree with existing experiments in 82 cases and disagree in only 17 cases, a validation rate of 75%. Our results reveal nodes that could be engineered to impact stomatal closure in a controlled fashion and also provide over 140 novel predictions for which experimental data are currently lacking. Noting the paucity of wet-bench data regarding combinatorial effects of ABA and internal node activation, we experimentally confirmed several predictions of the model with regard to reactive oxygen species, cytosolic Ca2+ (Ca2+c), and heterotrimeric G-protein signaling. We analyzed dynamics-determining positive and negative feedback loops, thereby elucidating the attractor (dynamic behavior) repertoire of the system and the groups of nodes that determine each attractor. Based on this analysis, we predict the likely presence of a previously unrecognized feedback mechanism dependent on Ca2+c. This mechanism would provide model agreement with 10 additional experimental observations, for a validation rate of 85%. Our research underscores the importance of feedback regulation in generating robust and adaptable biological responses. The high validation rate of our model illustrates the advantages of discrete dynamic modeling for complex, nonlinear systems common in biology. PMID:28937978

NbCZF1, a Novel C2H2-Type Zinc Finger Protein, as a New Regulator of SsCut-Induced Plant Immunity in Nicotiana benthamiana.

PubMed

Zhang, Huajian; Zhao, Tongyao; Zhuang, Peitong; Song, Zhiqiang; Du, Hui; Tang, Zhaozhao; Gao, Zhimou

2016-12-01

SsCut, which functions as an elicitor, can induce plant immunity. In this study, we utilized Nicotiana benthamiana and virus-induced gene silencing to decrease the expression of > 2,500 genes individually. Using this forward genetics approach, several genes were identified that, when silenced, compromised SsCut-triggered cell death based on a cell death assay. A C 2 H 2 -type zinc finger gene was isolated from N. benthamiana Sequence analysis indicated that the gene encodes a 27 kDa protein with 253 amino acids containing two typical C 2 H 2 -type zinc finger domains; this gene was named NbCZF1 We found that SsCut-induced cell death could be inhibited by virus-induced gene silencing of NbCZF1 in N. benthamiana In addition, SsCut induces stomatal closure, accompanied by reactive oxygen species (ROS) production by NADPH oxidases and nitric oxide (NO) production. NbCZF1-silenced plants showed impaired SsCut-induced stomatal closure, decreased SsCut-induced production of ROS and NO in guard cells and reduced SsCut-induced resistance against Phytophthora nicotianae Taken together, these results demonstrate that the NbCZF1-ROS-NO pathway mediates multiple SsCut-triggered responses, including stomatal closure, hypersensitive responses and defense-related gene expression. This is the first report describing the function of a C 2 H 2 -type zinc finger protein in N. benthamiana. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Genome-wide analysis of aquaporin gene family and their responses to water-deficit stress conditions in cassava.

PubMed

Putpeerawit, Pattaranit; Sojikul, Punchapat; Thitamadee, Siripong; Narangajavana, Jarunya

2017-12-01

Cassava (Manihot esculenta Crantz) is an important economic crop in tropical countries. Although cassava is considered a drought-tolerant crop that can grow in arid areas, the impact of drought can significantly reduce the growth and yield of cassava storage roots. The discovery of aquaporin molecules (AQPs) in plants has resulted in a paradigm shift in the understanding of plant-water relationships, whereas the relationship between aquaporin and drought resistance in cassava still remains elusive. To investigate the potential role of aquaporin in cassava under water-deficit conditions, 45 putative MeAQPs were identified in the cassava genome. Six members of MeAQPs, containing high numbers of water stress-responsive motifs in their promoter regions, were selected for a gene expression study. Two cassava cultivars, which showed different degrees of responses to water-deficit stress, were used to test in in vitro and potted plant systems. The differential expression of all candidate MeAQPs were found in only leaves from the potted plant system were consistent with the relative water content and with the stomatal closure profile of the two cultivars. MePIP2-1 and MePIP2-10 were up-regulated and this change in their expression might regulate a special signal for water efflux out of guard cells, thus inducing stomatal closure under water-deficit conditions. In addition, the expression profiles of genes in the ABA-dependent pathway revealed an essential correlation with stomatal closure. The potential functions of MeAQPs and candidate ABA-dependent pathway genes in response to water deficit in the more tolerant cassava cultivar were discussed. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Dissecting molecular and physiological response mechanisms to high solar radiation in cyanic and acyanic leaves: a case study on red and green basil.

PubMed

Tattini, Massimiliano; Sebastiani, Federico; Brunetti, Cecilia; Fini, Alessio; Torre, Sara; Gori, Antonella; Centritto, Mauro; Ferrini, Francesco; Landi, Marco; Guidi, Lucia

2017-04-01

Photosynthetic performance and the expression of genes involved in light signaling and the biosynthesis of isoprenoids and phenylpropanoids were analysed in green ('Tigullio', TIG) and red ('Red Rubin', RR) basil. The aim was to detect the physiological and molecular response mechanisms to high sunlight. The attenuation of blue-green light by epidermal anthocyanins was shown to evoke shade-avoidance responses with consequential effects on leaf morpho-anatomical traits and gas exchange performance. Red basil had a lower mesophyll conductance, partially compensated by the less effective control of stomatal movements, in comparison with TIG. Photosynthesis decreased more in TIG than in RR in high sunlight, because of larger stomatal limitations and the transient impairment of PSII photochemistry. The methylerythritol 4-phosphate pathway promoted above all the synthesis and de-epoxidation of violaxanthin-cycle pigments in TIG and of neoxanthin and lutein in RR. This enabled the green leaves to process the excess radiant energy effectively, and the red leaves to optimize light harvesting and photoprotection. The greater stomatal closure observed in TIG than in RR was due to enhanced abscisic acid (ABA) glucose ester deglucosylation and reduced ABA oxidation, rather than to superior de novo ABA synthesis. This study shows a strong competition between anthocyanin and flavonol biosynthesis, which occurs at the level of genes regulating the oxidation of the C2-C3 bond in the dihydro-flavonoid skeleton. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Hydraulic patterns and safety margins, from stem to stomata, in three eastern U.S. tree species.

PubMed

Johnson, D M; McCulloh, K A; Meinzer, F C; Woodruff, D R; Eissenstat, D M

2011-06-01

Adequate water transport is necessary to prevent stomatal closure and allow for photosynthesis. Dysfunction in the water transport pathway can result in stomatal closure, and can be deleterious to overall plant health and survival. Although much is known about small branch hydraulics, little is known about the coordination of leaf and stem hydraulic function. Additionally, the daily variations in leaf hydraulic conductance (K(leaf)), stomatal conductance and water potential (Ψ(L)) have only been measured for a few species. The objective of the current study was to characterize stem and leaf vulnerability to hydraulic dysfunction for three eastern U.S. tree species (Acer rubrum, Liriodendron tulipifera and Pinus virginiana) and to measure in situ daily patterns of K(leaf), leaf and stem Ψ, and stomatal conductance in the field. Sap flow measurements were made on two of the three species to compare patterns of whole-plant water use with changes in K(leaf) and stomatal conductance. Overall, stems were more resistant to hydraulic dysfunction than leaves. Stem P50 (Ψ resulting in 50% loss in conductivity) ranged from -3.0 to -4.2 MPa, whereas leaf P50 ranged from -0.8 to -1.7 MPa. Field Ψ(L) declined over the course of the day, but only P. virginiana experienced reductions in K(leaf) (nearly 100% loss). Stomatal conductance was greatest overall in P. virginiana, but peaked midmorning and then declined in all three species. Midday stem Ψ in all three species remained well above the threshold for embolism formation. The daily course of sap flux in P. virginiana was bell-shaped, whereas in A. rubrum sap flux peaked early in the morning and then declined over the remainder of the day. An analysis of our data and data for 39 other species suggest that there may be at least three distinct trajectories of relationships between maximum K(leaf) and the % K(leaf) at Ψ(min). In one group of species, a trade-off between maximum K(leaf) and % K(leaf) at Ψ(min) appeared to exist, but no trade-off was evident in the other two trajectories.

The maize OST1 kinase homolog phosphorylates and regulates the maize SNAC1-type transcription factor.

PubMed

Vilela, Belmiro; Moreno-Cortés, Alicia; Rabissi, Agnese; Leung, Jeffrey; Pagès, Montserrat; Lumbreras, Victoria

2013-01-01

The Arabidopsis kinase OPEN STOMATA 1 (OST1) plays a key role in regulating drought stress signalling, particularly stomatal closure. We have identified and investigated the functions of the OST1 ortholog in Z. mays (ZmOST1). Ectopic expression of ZmOST1 in the Arabidopsis ost1 mutant restores the stomatal closure phenotype in response to drought. Furthermore, we have identified the transcription factor, ZmSNAC1, which is directly phosphorylated by ZmOST1 with implications on its localization and protein stability. Interestingly, ZmSNAC1 binds to the ABA-box of ZmOST1, which is conserved in SnRK2s activated by ABA and is part of the contact site for the negative-regulating clade A PP2C phosphatases. Taken together, our results indicate that ZmSNAC1 is a substrate of ZmOST1 and delineate a novel osmotic stress transcriptional pathway in maize.

The Maize OST1 Kinase Homolog Phosphorylates and Regulates the Maize SNAC1-Type Transcription Factor

PubMed Central

Rabissi, Agnese; Leung, Jeffrey; Pagès, Montserrat; Lumbreras, Victoria

2013-01-01

The Arabidopsis kinase OPEN STOMATA 1 (OST1) plays a key role in regulating drought stress signalling, particularly stomatal closure. We have identified and investigated the functions of the OST1 ortholog in Z. mays (ZmOST1). Ectopic expression of ZmOST1 in the Arabidopsis ost1 mutant restores the stomatal closure phenotype in response to drought. Furthermore, we have identified the transcription factor, ZmSNAC1, which is directly phosphorylated by ZmOST1 with implications on its localization and protein stability. Interestingly, ZmSNAC1 binds to the ABA-box of ZmOST1, which is conserved in SnRK2s activated by ABA and is part of the contact site for the negative-regulating clade A PP2C phosphatases. Taken together, our results indicate that ZmSNAC1 is a substrate of ZmOST1 and delineate a novel osmotic stress transcriptional pathway in maize. PMID:23469147

Stomatal dynamics are limited by leaf hydraulics in ferns and conifers: results from simultaneous measurements of liquid and vapour fluxes in leaves.

PubMed

Martins, Samuel C V; McAdam, Scott A M; Deans, Ross M; DaMatta, Fábio M; Brodribb, Tim J

2016-03-01

Stomatal responsiveness to vapour pressure deficit (VPD) results in continuous regulation of daytime gas-exchange directly influencing leaf water status and carbon gain. Current models can reasonably predict steady-state stomatal conductance (gs ) to changes in VPD but the gs dynamics between steady-states are poorly known. Here, we used a diverse sample of conifers and ferns to show that leaf hydraulic architecture, in particular leaf capacitance, has a major role in determining the gs response time to perturbations in VPD. By using simultaneous measurements of liquid and vapour fluxes into and out of leaves, the in situ fluctuations in leaf water balance were calculated and appeared to be closely tracked by changes in gs thus supporting a passive model of stomatal control. Indeed, good agreement was found between observed and predicted gs when using a hydropassive model based on hydraulic traits. We contend that a simple passive hydraulic control of stomata in response to changes in leaf water status provides for efficient stomatal responses to VPD in ferns and conifers, leading to closure rates as fast or faster than those seen in most angiosperms. © 2015 John Wiley & Sons Ltd.

Forest canopy hydraulics

Treesearch

David R. Woodruff; Frederick C. Meinzer; Katherine A. McCulloh

2016-01-01

Water and carbon cycles are strongly coordinated and water availability is a primary limiting factor in many terrestrial ecosystems. Photosynthesis requires sufficient water supply to leaves and constraints on delivery at any point in the hydraulic continuum can lead to stomatal closure and reduced photosynthesis. Thus, maximizing water transport enhances assimilation...

Hydraulic adjustments underlying drought resistance of Pinus halepensis.

PubMed

Klein, Tamir; Cohen, Shabtai; Yakir, Dan

2011-06-01

Drought-induced tree mortality has increased over the last decades in forests around the globe. Our objective was to investigate under controlled conditions the hydraulic adjustments underlying the observed ability of Pinus halepensis to survive seasonal drought under semi-arid conditions. One hundred 18-month saplings were exposed in the greenhouse to 10 different drought treatments, simulating combinations of intensities (fraction of water supply relative to control) and durations (period with no water supply) for 30 weeks. Stomata closed at a leaf water potential (Ψ(l)) of -2.8 MPa, suggesting isohydric stomatal regulation. In trees under extreme drought treatments, stomatal closure reduced CO(2) uptake to -1 µmol m(-2) s(-1), indicating the development of carbon starvation. A narrow hydraulic safety margin of 0.3 MPa (from stomatal closure to 50% loss of hydraulic conductivity) was observed, indicating a strategy of maximization of CO2 uptake in trees otherwise adapted to water stress. A differential effect of drought intensity and duration was observed, and was explained by a strong dependence of the water stress effect on the ratio of transpiration to evapotranspiration T/ET and the larger partitioning to transpiration associated with larger irrigation doses. Under intense or prolonged drought, the root system became the main target for biomass accumulation, taking up to 100% of the added biomass, while the stem tissue biomass decreased, associated with up to 60% reduction in xylem volume.

Intraspecific differences in drought tolerance and acclimation in hydraulics of Ligustrum vulgare and Viburnum lantana.

PubMed

Beikircher, Barbara; Mayr, Stefan

2009-06-01

An adequate general drought tolerance and the ability to acclimate to changing hydraulic conditions are important features for long-lived woody plants. In this study, we compared hydraulic safety (water potential at 50% loss of conductivity, Psi(50)), hydraulic efficiency (specific conductivity, k(s)), xylem anatomy (mean tracheid diameter, d(mean), mean hydraulic diameter, d(h), conduit wall thickness, t, conduit wall reinforcement, (t/b)(h)(2)) and stomatal conductance, g(s), of forest plants as well as irrigated and drought-treated garden plants of Ligustrum vulgare L. and Viburnum lantana L. Forest plants of L. vulgare and V. lantana were significantly less resistant to drought-induced cavitation (Psi(50) at -2.82 +/- 0.13 MPa and -2.79 +/- 0.17 MPa) than drought-treated garden plants (- 4.58 +/- 0.26 MPa and -3.57 +/- 0.15 MPa). When previously irrigated garden plants were subjected to drought, a significant decrease in d(mean) and d(h) and an increase in t and (t/b)(h)(2) were observed in L. vulgare. In contrast, in V. lantana conduit diameters increased significantly but no change in t and (t/b)(h)(2) was found. Stomatal closure occurred at similar water potentials (Psi(sc)) in forest plants and drought-treated garden plants, leading to higher safety margins (Psi(sc) - Psi(50)) of the latter (L. vulgare 1.63 MPa and V. lantana 0.43 MPa). These plants also showed higher g(s) at moderate Psi, more abrupt stomatal closure and lower cuticular conductivity. Data indicate that the development of drought-tolerant xylem as well as stomatal regulation play an important role in drought acclimation, whereby structural and physiological responses to drought are species-specific and depend on the plant's hydraulic strategy.

Drought effect on growth, gas exchange and yield, in two strains of local barley Ardhaoui, under water deficit conditions in southern Tunisia.

PubMed

Thameur, Afwa; Lachiheb, Belgacem; Ferchichi, Ali

2012-12-30

Two local barley strains cv. Ardhaoui originated from Tlalit and Switir, sourthern Tunisia were grown in pots in a glasshouse assay, under well-watered conditions for a month. Plants were then either subjected to water deficit (treatment) or continually well-watered (control). Control pots were irrigated several times each week to maintain soil moisture near field capacity (FC), while stress pots experienced soil drying by withholding irrigation until they reached 50% of FC. Variation in relative water content, leaf area, leaf appearance rate and leaf gas exchange (i.e. net CO(2) assimilation rate (A), transpiration (E), and stomatal conductance (gs)) in response to water deficit was investigated. High leaf relative water content (RWC) was maintained in Tlalit by stomatal closure and a reduction of leaf area. Reduction in leaf area was due to decline in leaf gas exchange during water deficit. Tlalit was found to be drought tolerant and able to maintain higher leaf RWC under drought conditions. Water deficit treatment reduced stomatal conductance by 43% at anthesis. High net CO(2) assimilation rate under water deficit was associated with high RWC (r = 0.998; P < 0.01). Decline in net CO(2) assimilation rate was due mainly to stomatal closure. Significant differences between studied strains in leaf gas exchange parameters were found, which can give some indications on the degree of drought tolerance. Thus, the ability of the low leaf area plants to maintain higher RWC could explain the differences in drought tolerance in studied barley strains. Results showed that Tlalit showed to be more efficient and more productive than Switir. Copyright © 2012 Elsevier Ltd. All rights reserved.

Avoiding high relative air humidity during critical stages of leaf ontogeny is decisive for stomatal functioning.

PubMed

Fanourakis, Dimitrios; Carvalho, Susana M P; Almeida, Domingos P F; Heuvelink, Ep

2011-07-01

Plants of several species, if grown at high relative air humidity (RH ≥85%), develop stomata that fail to close fully in case of low leaf water potential. We studied the effect of a reciprocal change in RH, at different stages of leaf expansion of Rosa hybrida grown at moderate (60%) or high (95%) RH, on the stomatal closing ability. This was assessed by measuring the leaf transpiration rate in response to desiccation once the leaves had fully expanded. For leaves that started expanding at high RH but completed their expansion after transfer to moderate RH, the earlier this switch took place the better the stomatal functioning. Leaves initially expanding at moderate RH and transferred to high RH exhibited poor stomatal functioning, even when this transfer occurred very late during leaf expansion. Applying a daily abscisic acid (ABA) solution to the leaves of plants grown at continuous high RH was effective in inducing stomatal closure at low water potential, if done before full leaf expansion (FLE). After FLE, stomatal functioning was no longer affected either by the RH or ABA level. The results indicate that the degree of stomatal adaptation depends on both the timing and duration of exposure to high RH. It is concluded that stomatal functionality is strongly dependent on the humidity at which the leaf completed its expansion. The data also show that the effect of ambient RH and the alleviating role of ABA are restricted to the period of leaf expansion. Copyright © Physiologia Plantarum 2011.

Stomatal action directly feeds back on leaf turgor: new insights into the regulation of the plant water status from non-invasive pressure probe measurements.

PubMed

Ache, Peter; Bauer, Hubert; Kollist, Hannes; Al-Rasheid, Khaled A S; Lautner, Silke; Hartung, Wolfram; Hedrich, Rainer

2010-06-01

Uptake of CO(2) by the leaf is associated with loss of water. Control of stomatal aperture by volume changes of guard cell pairs optimizes the efficiency of water use. Under water stress, the protein kinase OPEN STOMATA 1 (OST1) activates the guard-cell anion release channel SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1), and thereby triggers stomatal closure. Plants with mutated OST1 and SLAC1 are defective in guard-cell turgor regulation. To study the effect of stomatal movement on leaf turgor using intact leaves of Arabidopsis, we used a new pressure probe to monitor transpiration and turgor pressure simultaneously and non-invasively. This probe permits routine easy access to parameters related to water status and stomatal conductance under physiological conditions using the model plant Arabidopsis thaliana. Long-term leaf turgor pressure recordings over several weeks showed a drop in turgor during the day and recovery at night. Thus pressure changes directly correlated with the degree of plant transpiration. Leaf turgor of wild-type plants responded to CO(2), light, humidity, ozone and abscisic acid (ABA) in a guard cell-specific manner. Pressure probe measurements of mutants lacking OST1 and SLAC1 function indicated impairment in stomatal responses to light and humidity. In contrast to wild-type plants, leaves from well-watered ost1 plants exposed to a dry atmosphere wilted after light-induced stomatal opening. Experiments with open stomata mutants indicated that the hydraulic conductance of leaf stomata is higher than that of the root-shoot continuum. Thus leaf turgor appears to rely to a large extent on the anion channel activity of autonomously regulated stomatal guard cells.

Coordination and transport of water and carbohydrates in the coupled soil-root-xylem-phloem leaf system

NASA Astrophysics Data System (ADS)

Katul, Gabriel; Huang, Cheng-Wei

2017-04-01

In response to varying environmental conditions, stomatal pores act as biological valves that dynamically adjust their size thereby determining the rate of CO2 assimilation and water loss (i.e., transpiration) to the atmosphere. Although the significance of this biotic control on gas exchange is rarely disputed, representing parsimoniously all the underlying mechanisms responsible for stomatal kinetics remain a subject of some debate. It has been conjectured that stomatal control in seed plants (i.e., angiosperm and gymnosperm) represents a compromise between biochemical demand for CO2 and prevention of excessive water loss. This view has been amended at the whole-plant level, where xylem hydraulics and sucrose transport efficiency in phloem appear to impose additional constraints on gas exchange. If such additional constraints impact stomatal opening and closure, then seed plants may have evolved coordinated photosynthetic-hydraulic-sugar transporting machinery that confers some competitive advantages in fluctuating environmental conditions. Thus, a stomatal optimization model that explicitly considers xylem hydraulics and maximum sucrose transport is developed to explore this coordination in the leaf-xylem-phloem system. The model is then applied to progressive drought conditions. The main findings from the model calculations are that (1) the predicted stomatal conductance from the conventional stomatal optimization theory at the leaf and the newly proposed models converge, suggesting a tight coordination in the leaf-xylem-phloem system; (2) stomatal control is mainly limited by the water supply function of the soil-xylem hydraulic system especially when the water flux through the transpiration stream is significantly larger than water exchange between xylem and phloem; (3) thus, xylem limitation imposed on the supply function can be used to differentiate species with different water use strategy across the spectrum of isohydric to anisohydric behavior.

Atmospheric CO2 Alters Resistance of Arabidopsis to Pseudomonas syringae by Affecting Abscisic Acid Accumulation and Stomatal Responsiveness to Coronatine

PubMed Central

Zhou, Yeling; Vroegop-Vos, Irene; Schuurink, Robert C.; Pieterse, Corné M. J.; Van Wees, Saskia C. M.

2017-01-01

Atmospheric CO2 influences plant growth and stomatal aperture. Effects of high or low CO2 levels on plant disease resistance are less well understood. Here, resistance of Arabidopsis thaliana against the foliar pathogen Pseudomonas syringae pv. tomato DC3000 (Pst) was investigated at three different CO2 levels: high (800 ppm), ambient (450 ppm), and low (150 ppm). Under all conditions tested, infection by Pst resulted in stomatal closure within 1 h after inoculation. However, subsequent stomatal reopening at 4 h, triggered by the virulence factor coronatine (COR), occurred only at ambient and high CO2, but not at low CO2. Moreover, infection by Pst was reduced at low CO2 to the same extent as infection by mutant Pst cor-. Under all CO2 conditions, the ABA mutants aba2-1 and abi1-1 were as resistant to Pst as wild-type plants under low CO2, which contained less ABA. Moreover, stomatal reopening mediated by COR was dependent on ABA. Our results suggest that reduced ABA levels at low CO2 contribute to the observed enhanced resistance to Pst by deregulation of virulence responses. This implies that enhanced ABA levels at increasing CO2 levels may have a role in weakening plant defense. PMID:28559899

Common and unique elements of the ABA-regulated transcriptome of Arabidopsis guard cells

PubMed Central

2011-01-01

Background In the presence of drought and other desiccating stresses, plants synthesize and redistribute the phytohormone abscisic acid (ABA). ABA promotes plant water conservation by acting on specialized cells in the leaf epidermis, guard cells, which border and regulate the apertures of stomatal pores through which transpirational water loss occurs. Following ABA exposure, solute uptake into guard cells is rapidly inhibited and solute loss is promoted, resulting in inhibition of stomatal opening and promotion of stomatal closure, with consequent plant water conservation. There is a wealth of information on the guard cell signaling mechanisms underlying these rapid ABA responses. To investigate ABA regulation of gene expression in guard cells in a systematic genome-wide manner, we analyzed data from global transcriptomes of guard cells generated with Affymetrix ATH1 microarrays, and compared these results to ABA regulation of gene expression in leaves and other tissues. Results The 1173 ABA-regulated genes of guard cells identified by our study share significant overlap with ABA-regulated genes of other tissues, and are associated with well-defined ABA-related promoter motifs such as ABREs and DREs. However, we also computationally identified a unique cis-acting motif, GTCGG, associated with ABA-induction of gene expression specifically in guard cells. In addition, approximately 300 genes showing ABA-regulation unique to this cell type were newly uncovered by our study. Within the ABA-regulated gene set of guard cells, we found that many of the genes known to encode ion transporters associated with stomatal opening are down-regulated by ABA, providing one mechanism for long-term maintenance of stomatal closure during drought. We also found examples of both negative and positive feedback in the transcriptional regulation by ABA of known ABA-signaling genes, particularly with regard to the PYR/PYL/RCAR class of soluble ABA receptors and their downstream targets, the type 2C protein phosphatases. Our data also provide evidence for cross-talk at the transcriptional level between ABA and another hormonal inhibitor of stomatal opening, methyl jasmonate. Conclusions Our results engender new insights into the basic cell biology of guard cells, reveal common and unique elements of ABA-regulation of gene expression in guard cells, and set the stage for targeted biotechnological manipulations to improve plant water use efficiency. PMID:21554708

Overexpression of an ABA biosynthesis gene using a stress inducible promoter enhances drought resistance in petunia

USDA-ARS?s Scientific Manuscript database

Plants respond to drought stress by closing their stomata and reducing transpirational water loss. The plant hormone abscisic acid (ABA) regulates growth and stomatal closure particularly when the plant is under environmental stresses. One of the key enzymes in the ABA biosynthesis of higher plants ...

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Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-20

... Valley Fever Virus, Ebola Virus, Andes Virus and Vesicular Stomatitis Virus Infectivity, Compositions and...,966, entitled ``Therapeutic Peptides that Inhibit Rift Valley Fever Virus, Ebola Virus, Andes Virus and Vesicular Stomatitis Virus Infectivity, Compositions and Methods,'' filed on December 6, 2012. The...

Phosphatidylinositol 3-Kinase Promotes V-ATPase Activation and Vacuolar Acidification and Delays Methyl Jasmonate-Induced Leaf Senescence1

PubMed Central

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

2016-01-01

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

Hydraulics of high-yield orchard trees: a case study of three Malus domestica cultivars.

PubMed

Beikircher, Barbara; De Cesare, Chiara; Mayr, Stefan

2013-12-01

The drought tolerance of three economically important apple cultivars, Golden Delicious, Braeburn and Red Delicious, was analysed. The work offers insights into the hydraulics of these high-yield trees and indicates a possible hydraulic limitation of carbon gain. The hydraulic safety and efficiency of branch xylem and leaves were quantified, drought tolerance of living tissues was measured and stomatal regulation, turgor-loss point and osmotic potential at full turgor were analysed. Physiological measurements were correlated with anatomical parameters, such as conduit diameter, cell-wall reinforcement, stomatal density and stomatal pore length. Hydraulic safety differed considerably between the three cultivars with Golden Delicious being significantly less vulnerable to drought-induced embolism than Braeburn and Red Delicious. In Golden Delicious, leaves were less resistant than branch xylem, while in the other cultivars leaves were more resistant than branch xylem. Hydraulic efficiency and xylem anatomical measurements indicate differences in pit properties, which may also be responsible for variations in hydraulic safety. In all three cultivars, full stomatal closure occurred at water potentials where turgor had already been lost and severe loss of hydraulic conductivity as well as damage to living cells had been induced. The consequential negative safety margins pose a risk for hydraulic failure but facilitate carbon gain, which is further improved by the observed high stomatal conductance. Maximal stomatal conductance was clearly seen to be related to stomatal density and size. Based on our results, these three high-yield Malus domestica Borkh. cultivars span a wide range of drought tolerances, appear optimized for maximal carbon gain and, thus, all perform best under well-managed growing conditions.

ABA is required for the accumulation of APX1 and MBF1c during a combination of water deficit and heat stress

PubMed Central

Zandalinas, Sara I.; Balfagón, Damián; Arbona, Vicent; Gómez-Cadenas, Aurelio; Inupakutika, Madhuri A.; Mittler, Ron

2016-01-01

Abscisic acid (ABA) plays a key role in plant acclimation to abiotic stress. Although recent studies suggested that ABA could also be important for plant acclimation to a combination of abiotic stresses, its role in this response is currently unknown. Here we studied the response of mutants impaired in ABA signalling (abi1-1) and biosynthesis (aba1-1) to a combination of water deficit and heat stress. Both mutants displayed reduced growth, biomass, and survival when subjected to stress combination. Focusing on abi1-1, we found that although its stomata had an impaired response to water deficit, remaining significantly more open than wild type, its stomatal aperture was surprisingly reduced when subjected to the stress combination. Stomatal closure during stress combination in abi1-1 was accompanied by higher levels of H2O2 in leaves, suggesting that H2O2 might play a role in this response. In contrast to the almost wild-type stomatal closure phenotype of abi1-1 during stress combination, the accumulation of ascorbate peroxidase 1 and multiprotein bridging factor 1c proteins, required for acclimation to a combination of water deficit and heat stress, was significantly reduced in abi1-1. Our findings reveal a key function for ABA in regulating the accumulation of essential proteins during a combination of water deficit and heat stress. PMID:27497287

Adaptive mechanisms and genomic plasticity for drought tolerance identified in European black poplar (Populus nigra L.)

PubMed Central

Viger, Maud; Smith, Hazel K.; Cohen, David; Dewoody, Jennifer; Trewin, Harriet; Steenackers, Marijke; Bastien, Catherine; Taylor, Gail

2016-01-01

Summer droughts are likely to increase in frequency and intensity across Europe, yet long-lived trees may have a limited ability to tolerate drought. It is therefore critical that we improve our understanding of phenotypic plasticity to drought in natural populations for ecologically and economically important trees such as Populus nigra L. A common garden experiment was conducted using ∼500 wild P. nigra trees, collected from 11 river populations across Europe. Phenotypic variation was found across the collection, with southern genotypes from Spain and France characterized by small leaves and limited biomass production. To examine the relationship between phenotypic variation and drought tolerance, six genotypes with contrasting leaf morphologies were subjected to a water deficit experiment. ‘North eastern’ genotypes were collected at wet sites and responded to water deficit with reduced biomass growth, slow stomatal closure and reduced water use efficiency (WUE) assessed by Δ13C. In contrast, ‘southern’ genotypes originating from arid sites showed rapid stomatal closure, improved WUE and limited leaf loss. Transcriptome analyses of a genotype from Spain (Sp2, originating from an arid site) and another from northern Italy (Ita, originating from a wet site) revealed dramatic differences in gene expression response to water deficit. Transcripts controlling leaf development and stomatal patterning, including SPCH, ANT, ER, AS1, AS2, PHB, CLV1, ERL1–3 and TMM, were down-regulated in Ita but not in Sp2 in response to drought. PMID:27174702

Leaf hydraulic conductance, measured in situ, declines and recovers daily: leaf hydraulics, water potential and stomatal conductance in four temperate and three tropical tree species.

PubMed

Johnson, D M; Woodruff, D R; McCulloh, K A; Meinzer, F C

2009-07-01

Adequate leaf hydraulic conductance (Kleaf) is critical for preventing transpiration-induced desiccation and subsequent stomatal closure that would restrict carbon gain. A few studies have reported midday depression of Kleaf (or petiole conductivity) and its subsequent recovery in situ, but the extent to which this phenomenon is universal is not known. The objectives of this study were to measure Kleaf, using a rehydration kinetics method, (1) in the laboratory (under controlled conditions) across a range of water potentials to construct vulnerability curves (VC) and (2) over the course of the day in the field along with leaf water potential and stomatal conductance (gs). Two broadleaf (one evergreen, Arbutus menziesii Pursh., and one deciduous, Quercus garryana Dougl.) and two coniferous species (Pinus ponderosa Dougl. and Pseudotsuga menziesii [Mirbel]) were chosen as representative of different plant types. In addition, Kleaf in the laboratory and leaf water potential in the field were measured for three tropical evergreen species (Protium panamense (Rose), Tachigalia versicolor Standley and L.O. Williams and Vochysia ferruginea Mart) to predict their daily changes in field Kleaf in situ. It was hypothesized that in the field, leaves would close their stomata at water potential thresholds at which Kleaf begins to decline sharply in laboratory-generated VC, thus preventing substantial losses of Kleaf. The temperate species showed a 15-66% decline in Kleaf by midday, before stomatal closure. Although there were substantial midday declines in Kleaf, recovery was nearly complete by late afternoon. Stomatal conductance began to decrease in Pseudotsuga, Pinus and Quercus once Kleaf began to decline; however, there was no detectable reduction in gs in Arbutus. Predicted Kleaf in the tropical species, based on laboratory-generated VC, decreased by 74% of maximum Kleaf in Tachigalia, but only 22-32% in Vochysia and Protium. The results presented here, from the previous work of the authors and from other published studies, were consistent with two different strategies regarding daily maintenance of Kleaf: (1) substantial loss and subsequent recovery or (2) a more conservative strategy of loss avoidance.

Transport and coordination in the coupled soil-root-xylem-phloem leaf system

NASA Astrophysics Data System (ADS)

Huang, C. W.; Katul, G. G.; Pockman, W.; Litvak, M. E.; Domec, J. C.; Palmroth, S.

2016-12-01

In response to varying environmental conditions, stomatal pores act as biological valves that dynamically adjust their size thereby determining the rate of CO2 assimilation and water loss (i.e., transpiration) to the dry atmosphere. Although the significance of this biotic control on gas exchange is rarely disputed, representing parsimoniously all the underlying mechanisms responsible for stomatal kinetics remain a subject of some debate. It has been conjectured that stomatal control in seed plants (i.e., angiosperm and gymnosperm) represents a compromise between biochemical demand for CO2 and prevention of excessive water loss. This view has been amended at the whole-plant level, where xylem hydraulics and sucrose transport efficiency in phloem appear to impose additional constraints on gas exchange. If such additional constraints impact stomatal opening and closure, then seed plants may have evolved coordinated photosynthetic-hydraulic-sugar transporting machinery that confers some competitive advantages in fluctuating environmental conditions. Thus, a stomatal optimization model that explicitly considers xylem hydraulics and maximum sucrose transport is developed to explore this coordination in the leaf-xylem-phloem system. The model is then applied to progressive drought conditions. The main findings from the model calculations are that (1) the predicted stomatal conductance from the conventional stomatal optimization theory at the leaf and the newly proposed models converge, suggesting a tight coordination in the leaf-xylem-phloem system; (2) stomatal control is mainly limited by the water supply function of the soil-xylem hydraulic system especially when the water flux through the transpiration stream is significantly larger than water exchange between xylem and phloem; (3) thus, xylem limitation imposed on the supply function can be used to differentiate species with different water use strategy across the spectrum of isohydric to anisohydric behavior. Keywords: leaf-level gas exchange, stomatal control, sucrose transport in phloem, xylem hydraulics

Isolation of ABA-responsive mutants in allohexaploid bread wheat (Triticum aestivum L.): Drawing connections to grain dormancy, preharvest sprouting, and drought tolerance

USDA-ARS?s Scientific Manuscript database

This paper describes the isolation of Wheat ABA-responsive mutants (Warm) in Chinese spring background of allohexaploid Triticum aestivum. The plant hormone abscisic acid (ABA) is required for the induction of seed dormancy, the induction of stomatal closure and drought tolerance, and is associated...

NATIVE ROOT XYLEM EMBOLISM AND STOMATAL CLOSURE IN STANDS OF DOUGLAS-FIR AND PONDEROSA PINE: MITIGATION BY HYDRAULIC REDISTRIBUTION

EPA Science Inventory

Hydraulic redistribution (HR), the passive movement of water via roots from moist to drier portions of the soil, occurs in many ecosystems, influencing both plant and ecosystem-water use. We examined the effects of HR on root hydraulic functioning during drought in young and old-...

Influence of Cadmium on Water Relations, Stomatal Resistance, and Abscisic Acid Content in Expanding Bean Leaves 1

PubMed Central

Poschenrieder, Charlotte; Gunsé, Benet; Barceló, Juan

1989-01-01

Ten day old bush bean plants (Phaseolus vulgaris L. cv Contender) were used to analyze the effects of 3 micromolar Cd on the time courses of expansion growth, dry weight, leaf water relations, stomatal resistance, and abscisic acid (ABA) levels in roots and leaves. Control and Cd-treated plants were grown for 144 hours in nutrient solution. Samples were taken at 24 hour intervals. At the 96 and 144 hour harvests, additional measurements were made on excised leaves which were allowed to dry for 2 hours. From the 48 hour harvest, Cd-treated plants showed lower leaf relative water contents and higher stomatal resistances than controls. At the same time, root and leaf expansion growth, but not dry weight, was significantly reduced. The turgor potentials of leaves from Cd-treated plants were nonsignificantly higher than those of control leaves. A significant increase (almost 400%) of the leaf ABA concentration was detected after 120 hours exposure to Cd. But Cd was found to inhibit ABA accumulation during drying of excised leaves. It is concluded that Cd-induced decrease of expansion growth is not due to turgor decrease. The possible mechanisms of Cd-induced stomatal closure are discussed. PMID:16666937

Leaf Hydraulic Vulnerability Triggers the Decline in Stomatal and Mesophyll Conductance during drought in Rice (Oryza sativa).

PubMed

Wang, Xiaoxiao; Du, Tingting; Huang, Jianliang; Peng, Shaobing; Xiong, Dongliang

2018-05-18

Understanding the physiological responses of crops to drought is important for ensuring sustained crop productivity under climate change, which is expected to exacerbate drought frequencies and intensities. Drought responses involve multiple traits, but the correlations between these traits are poorly understood. Using a variety of techniques, we estimated the changes in gas exchange, leaf hydraulic conductance (Kleaf), and leaf turgor in rice (Oryza sativa) in response to both short- and long-term soil drought and performed a photosynthetic limitation analysis to quantify the contributions of each limiting factor to the resultant overall decrease in photosynthesis during drought. Biomass, leaf area and leaf width significantly decreased during the two-week drought treatment, but leaf mass per area and leaf vein density increased. Light-saturated photosynthetic rate (A) declined dramatically during soil drought, mainly due to the decrease in stomatal conductance (gs) and mesophyll conductance (gm). Stomatal modeling suggested that the decline in Kleaf explained most of the decrease in stomatal closure during the drought treatment, and may also trigger the drought-related decrease of gs and gm. The results of this study provide insight into the regulation of carbon assimilation under drought conditions.

Differential role of ethylene and hydrogen peroxide in dark-induced stomatal closure.

PubMed

Kar, R K; Parvin, N; Laha, D

2013-12-15

Regulation of stomatal aperture is crucial in terrestrial plants for controlling water loss and gaseous exchange with environment. While much is known of signaling for stomatal opening induced by blue light and the role of hormones, little is known about the regulation of stomatal closing in darkness. The present study was aimed to verify their role in stomatal regulation in darkness. Epidermal peelings from the leaves of Commelina benghalensis were incubated in a defined medium in darkness for 1 h followed by a 1 h incubation in different test solutions [H2O2, propyl gallate, ethrel (ethylene), AgNO3, sodium orthovanadate, tetraethyl ammonium chloride, CaCl2, LaCl3, separately and in combination] before stomatal apertures were measured under the microscope. In the dark stomata remained closed under treatments with ethylene and propyl gallate but opened widely in the presence of H2O2 and AgNO3. The opening effect was largely unaffected by supplementing the treatment with Na-vanadate (PM H+ ATPase inhibitor) and tetraethyl ammonium chloride (K(+)-channel inhibitor) except that opening was significantly inhibited by the latter in presence of H2O2. On the other hand, H2O2 could not override the closing effect of ethylene at any concentrations while a marginal opening of stomata was found when Ag NO3 treatment was given together with propyl gallate. CaCl2 treatment opened stomata in the darkness while LaCl3 maintained stomata closed. A combination of LaCl3 and propyl gallate strongly promoted stomatal opening. A probable action of ethylene in closing stomata of Commelina benghalensis in dark has been proposed.

How do leaf hydraulics limit stomatal conductance at high water vapour pressure deficits?

PubMed

Bunce, James A

2006-08-01

A reduction in leaf stomatal conductance (g) with increasing leaf-to-air difference in water vapour pressure (D) is nearly ubiquitous. Ecological comparisons of sensitivity have led to the hypothesis that the reduction in g with increasing D serves to maintain leaf water potentials above those that would cause loss of hydraulic conductance. A reduction in leaf water potential is commonly hypothesized to cause stomatal closure at high D. The importance of these particular hydraulic factors was tested by exposing Abutilon theophrasti, Glycine max, Gossypium hirsutum and Xanthium strumarium to D high enough to reduce g and then decreasing ambient carbon dioxide concentration ([CO2]), and observing the resulting changes in g, transpiration rate and leaf water potential, and their reversibility. Reducing the [CO2] at high D increased g and transpiration rate and lowered leaf water potential. The abnormally high transpiration rates did not result in reductions in hydraulic conductance. Results indicate that low water potential effects on g at high D could be overcome by low [CO2], and that even lower leaf water potentials did not cause a reduction in hydraulic conductance in these well-watered plants. Reduced g at high D in these species resulted primarily from increased stomatal sensitivity to [CO2] at high D, and this increased sensitivity may mediate stomatal responses to leaf hydraulics at high D.

Anion channel sensitivity to cytosolic organic acids implicates a central role for oxaloacetate in integrating ion flux with metabolism in stomatal guard cells.

PubMed

Wang, Yizhou; Blatt, Michael R

2011-10-01

Stomatal guard cells play a key role in gas exchange for photosynthesis and in minimizing transpirational water loss from plants by opening and closing the stomatal pore. The bulk of the osmotic content driving stomatal movements depends on ionic fluxes across both the plasma membrane and tonoplast, the metabolism of organic acids, primarily Mal (malate), and its accumulation and loss. Anion channels at the plasma membrane are thought to comprise a major pathway for Mal efflux during stomatal closure, implicating their key role in linking solute flux with metabolism. Nonetheless, little is known of the regulation of anion channel current (I(Cl)) by cytosolic Mal or its immediate metabolite OAA (oxaloacetate). In the present study, we have examined the impact of Mal, OAA and of the monocarboxylic acid anion acetate in guard cells of Vicia faba L. and report that all three organic acids affect I(Cl), but with markedly different characteristics and sidedness to their activities. Most prominent was a suppression of ICl by OAA within the physiological range of concentrations found in vivo. These findings indicate a capacity for OAA to co-ordinate organic acid metabolism with I(Cl) through the direct effect of organic acid pool size. The findings of the present study also add perspective to in vivo recordings using acetate-based electrolytes.

Genotypically Identifying Wheat Mesophyll Conductance Regulation under Progressive Drought Stress

PubMed Central

Olsovska, Katarina; Kovar, Marek; Brestic, Marian; Zivcak, Marek; Slamka, Pavol; Shao, Hong Bo

2016-01-01

Photosynthesis limitation by CO2 flow constraints from sub-stomatal cavities to carboxylation sites in chloroplasts under drought stress conditions is, at least in some plant species or crops not fully understood, yet. Leaf mesophyll conductance for CO2 (gm) may considerably affect both photosynthesis and water use efficiency (WUE) in plants under drought conditions. The aim of our study was to detect the responses of gm in leaves of four winter wheat (Triticum aestivum L.) genotypes from different origins under long-term progressive drought. Based on the measurement of gas-exchange parameters the variability of genotypic responses was analyzed at stomatal (stomata closure) and non-stomatal (diffusional and biochemical) limits of net CO2 assimilation rate (AN). In general, progressive drought caused an increasing leaf diffusion resistance against CO2 flow leading to the decrease of AN, gm and stomatal conductance (gs), respectively. Reduction of gm also led to inhibition of carboxylation efficiency (Vcmax). On the basis of achieved results a strong positive relationship between gm and gs was found out indicating a co-regulation and mutual independence of the relationship under the drought conditions. In severely stressed plants, the stomatal limitation of the CO2 assimilation rate was progressively increased, but to a less extent in comparison to gm, while a non-stomatal limitation became more dominant due to the prolonged drought. Mesophyll conductance (gm) seems to be a suitable mechanism and parameter for selection of improved diffusional properties and photosynthetic carbon assimilation in C3 plants, thus explaining their better photosynthetic performance at a whole plant level during periods of drought. PMID:27551283

Silencing of OsGRX17 in rice improves drought stress tolerance by modulating ROS accumulation and stomatal closure

USDA-ARS?s Scientific Manuscript database

Glutaredoxins (GRXs) have emerged as key mediators in plant responses to environmental stimuli by modulating redox-dependent signaling pathways. Here, we report that RNAi-mediated suppression of the rice gene OsGRXS17, encoding a monothiol GRX with a CGFS-type active site motif, elevates H2O2 produc...

Plant water relations and the effects of elevated CO2: a review and suggestions for future research

Treesearch

Melvin T. Tyree; John D. Alexander

1993-01-01

Increased ambient carbon dioxide (CO2) has been found to ameliorate water stress in the majority of species studied. The results of many studies indicate that lower evaporative flux density is associated with high CO2-induced stomatal closure. As a result of decreases in evaporative flux density and increases in net...

Stomata of the CAM plant Tillandsia recurvata respond directly to humidity.

PubMed

Lange, O L; Medina, E

1979-01-01

Under controlled conditions, CO 2 exchange of Tillandsia recurvata showed all characteristics of CAM. During the phase of nocturnal CO 2 fixation stomata of the plant responded sensitively to changes in ambient air humidity. Dry air resulted in an increase, moist air in a decrease of diffusion resistance. The evaporative demand of the air affected the level of stomatal resistance during the entire night period. Due to stomatal closure, the total nocturnal water loss of T. recurvata was less at low than at high humidity. It is concluded that stomata respond directly to humidity and not via bulk tissue water conditions of the leaves. Such control of transpiration may optimize water use efficiency for this almost rootless, extreme epiphyte.

Simultaneous requirement of carbon dioxide and abscisic acid for stomatal closing in Xanthium strumarium L.

PubMed

Raschke, K

1975-01-01

Open stomata of detached leaves of Xanthium strumarium L. closed only when carbon dioxide and abscisic acid (ABA) were presented simultaneously. Three parameters of stomatal closing were determined after additions of ABA to the irrigation water of detached leaves, while the leaves were exposed to various CO2 concentrations ([CO2]s) in the air; a) the delay between addition of ABA and a reduction of stomatal conductance by 5%, b) the velocity of stomatal closing, and c) the new conductance. Changes in all three parameters showed that stomatal responses to ABA were enhanced by CO2; this effect followed saturation kinetics. Half saturation occurred at an estimated [CO2] in the stomatal pore of 200 μl l(-1). With respect to ABA, stomata responded in normal air with half their maximal amplitude at [ABA]s between 10(-6) and 10(-5) M(+-)-ABA. The amounts of ABA taken up by the leaves during the delay increased with a power <1 (on the average, 0.67) of the [ABA] in the transpiration stream. The minimal amount of ABA found to produce a stomatal response was about 1 pmol of (+-)-ABA per cm(2) leaf area, almost two orders of magnitude smaller than the original content of the leaves in ABA indicating that most of the endogenous ABA was in a compartment isolated from the guard cells.An interaction between stomatal responses to CO2 and ABA was also found in Gossypium hirsutum L. and Commelina communis L.; it was however much weaker than in X. strumarium.Based on earlier findings and on the results of this investigation it is suggested that stomata close if the cytoplasm of the guard cells contains much malate and H(+). The acid content in turn is determined by the relative rates of production of malic acid (from endogenous as well as exogenous CO2) and its removal (by transport of the anion into the vacuole and exchange of the H(+) for K(+) with the environment of the guard cells). The simultaneous requirement of CO2 and ABA for stomatal closure leads to the inference that ABA inhibits the expulsion of H(+) from guard cells.

Remote sensing of vegetation canopy photosynthetic and stomatal conductance efficiencies

NASA Technical Reports Server (NTRS)

Myneni, R. B.; Ganapol, B. D.; Asrar, G.

1992-01-01

The problem of remote sensing the canopy photosynthetic and stomatal conductance efficiencies is investigated with the aid of one- and three-dimensional radiative transfer methods coupled to a semi-empirical mechanistic model of leaf photosynthesis and stomatal conductance. Desertlike vegetation is modeled as clumps of leaves randomly distributed on a bright dry soil with partial ground cover. Normalized difference vegetation index (NDVI), canopy photosynthetic (Ep), and stomatal efficiencies (Es) are calculated for various geometrical, optical, and illumination conditions. The contribution of various radiative fluxes to estimates of Ep is evaluated and the magnitude of errors in bulk canopy formulation of problem parameters are quantified. The nature and sensitivity of the relationship between Ep and Es to NDVI is investigated, and an algorithm is proposed for use in operational remote sensing.

Inhibition of tomato shoot growth by over-irrigation is linked to nitrogen deficiency and ethylene.

PubMed

Fiebig, Antje; Dodd, Ian C

2016-01-01

Although physiological effects of acute flooding have been well studied, chronic effects of suboptimal soil aeration caused by over-irrigation of containerized plants have not, despite its likely commercial significance. By automatically scheduling irrigation according to soil moisture thresholds, effects of over-irrigation on soil properties (oxygen concentration, temperature and moisture), leaf growth, gas exchange, phytohormone [abscisic acid (ABA) and ethylene] relations and nutrient status of tomato (Solanum lycopersicum Mill. cv. Ailsa Craig) were studied. Over-irrigation slowly increased soil moisture and decreased soil oxygen concentration by 4%. Soil temperature was approximately 1°C lower in the over-irrigated substrate. Over-irrigating tomato plants for 2 weeks significantly reduced shoot height (by 25%) and fresh weight and total leaf area (by 60-70%) compared with well-drained plants. Over-irrigation did not alter stomatal conductance, leaf water potential or foliar ABA concentrations, suggesting that growth inhibition was not hydraulically regulated or dependent on stomatal closure or changes in ABA. However, over-irrigation significantly increased foliar ethylene emission. Ethylene seemed to inhibit growth, as the partially ethylene-insensitive genotype Never ripe (Nr) was much less sensitive to over-irrigation than the wild type. Over-irrigation induced significant foliar nitrogen deficiency and daily supplementation of small volumes of 10 mM Ca(NO3 )2 to over-irrigated soil restored foliar nitrogen concentrations, ethylene emission and shoot fresh weight of over-irrigated plants to control levels. Thus reduced nitrogen uptake plays an important role in inhibiting growth of over-irrigated plants, in part by stimulating foliar ethylene emission. © 2015 Scandinavian Plant Physiology Society.

Ascophyllum nodosum Seaweed Extract Alleviates Drought Stress in Arabidopsis by Affecting Photosynthetic Performance and Related Gene Expression.

PubMed

Santaniello, Antonietta; Scartazza, Andrea; Gresta, Francesco; Loreti, Elena; Biasone, Alessandro; Di Tommaso, Donatella; Piaggesi, Alberto; Perata, Pierdomenico

2017-01-01

Drought represents one of the most relevant abiotic stress affecting growth and yield of crop plants. In order to improve the agricultural productivity within the limited water and land resources, it is mandatory to increase crop yields in presence of unfavorable environmental stresses. The use of biostimulants, often containing seaweed extracts, represents one of the options for farmers willing to alleviate abiotic stress consequences on crops. In this work, we investigated the responses of Arabidopsis plants treated with an extract from the brown alga Ascophyllum nodosum (ANE), under drought stress conditions, demonstrating that ANE positively influences Arabidopsis survival. Pre-treatment with ANE induced a partial stomatal closure, associated with changes in the expression levels of genes involved in ABA-responsive and antioxidant system pathways. The pre-activation of these pathways results in a stronger ability of ANE-treated plants to maintain a better photosynthetic performance compared to untreated plants throughout the dehydration period, combined with a higher capacity to dissipate the excess of energy as heat in the reaction centers of photosystem II. Our results suggest that drought stressed plants treated with ANE are able to maintain a strong stomatal control and relatively higher values of both water use efficiency (WUE) and mesophyll conductance during the last phase of dehydration. Simultaneously, the activation of a pre-induced antioxidant defense system, in combination with a more efficient energy dissipation mechanism, prevents irreversible damages to the photosynthetic apparatus. In conclusion, pre-treatment with ANE is effective to acclimate plants to the incoming stress, promoting an increased WUE and dehydration tolerance.

Ascophyllum nodosum Seaweed Extract Alleviates Drought Stress in Arabidopsis by Affecting Photosynthetic Performance and Related Gene Expression

PubMed Central

Santaniello, Antonietta; Scartazza, Andrea; Gresta, Francesco; Loreti, Elena; Biasone, Alessandro; Di Tommaso, Donatella; Piaggesi, Alberto; Perata, Pierdomenico

2017-01-01

Drought represents one of the most relevant abiotic stress affecting growth and yield of crop plants. In order to improve the agricultural productivity within the limited water and land resources, it is mandatory to increase crop yields in presence of unfavorable environmental stresses. The use of biostimulants, often containing seaweed extracts, represents one of the options for farmers willing to alleviate abiotic stress consequences on crops. In this work, we investigated the responses of Arabidopsis plants treated with an extract from the brown alga Ascophyllum nodosum (ANE), under drought stress conditions, demonstrating that ANE positively influences Arabidopsis survival. Pre-treatment with ANE induced a partial stomatal closure, associated with changes in the expression levels of genes involved in ABA-responsive and antioxidant system pathways. The pre-activation of these pathways results in a stronger ability of ANE-treated plants to maintain a better photosynthetic performance compared to untreated plants throughout the dehydration period, combined with a higher capacity to dissipate the excess of energy as heat in the reaction centers of photosystem II. Our results suggest that drought stressed plants treated with ANE are able to maintain a strong stomatal control and relatively higher values of both water use efficiency (WUE) and mesophyll conductance during the last phase of dehydration. Simultaneously, the activation of a pre-induced antioxidant defense system, in combination with a more efficient energy dissipation mechanism, prevents irreversible damages to the photosynthetic apparatus. In conclusion, pre-treatment with ANE is effective to acclimate plants to the incoming stress, promoting an increased WUE and dehydration tolerance. PMID:28824691

Vanadate inhibition of stomatal opening in epidermal peels of Commelina communis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwartz, A.; Illan, N.; Assmann, S.M.

There are conflicting reports on the effectiveness of the plasmamembrane H{sup +} ATPase inhibitor, vanadate, in inhibiting stomatal opening. We have observed that vanadate inhibited light-stimulated stomatal opening in epidermal peels of Commelina communis only at KCl concentrations lower than 50 mM. When KCl was replaced with n-methylglucamine chloride, vanadate was still ineffective at high salt concentrations. However, in the absence of Cl{sup {minus}}, when KOH was buffered with V{sub 2}O{sub 5}, vanadate inhibition of stomatal opening occurred even at high salt concentrations (K{sup +} = 70 mM). An inhibitor of anion uptake, anthracene-9-carboxylic acid (200 {mu}M), partially prevented vanadatemore » inhibition of stomatal opening; other inhibitors (DIDS, SITS, Zn{sup 2+}) were ineffective. These results suggest that inhibition of stomatal opening by vanadate requires its entry into guard cells through an anion uptake system. Decreasing vanadate inhibition at high Cl{sup {minus}}/vanadate ratios may result from competition between vanadate and Cl{sup {minus}} for a common uptake mechanism.« less

CYCLIN H;1 regulates drought stress responses and blue light-induced stomatal opening by inhibiting reactive oxygen species accumulation in Arabidopsis.

PubMed

Zhou, Xiao Feng; Jin, Yin Hua; Yoo, Chan Yul; Lin, Xiao-Li; Kim, Woe-Yeon; Yun, Dae-Jin; Bressan, Ray A; Hasegawa, Paul M; Jin, Jing Bo

2013-06-01

Arabidopsis (Arabidopsis thaliana) CYCLIN-DEPENDENT KINASE Ds (CDKDs) phosphorylate the C-terminal domain of the largest subunit of RNA polymerase II. Arabidopsis CYCLIN H;1 (CYCH;1) interacts with and activates CDKDs; however, the physiological function of CYCH;1 has not been determined. Here, we report that CYCH;1, which is localized to the nucleus, positively regulates blue light-induced stomatal opening. Reduced-function cych;1 RNA interference (cych;1 RNAi) plants exhibited a drought tolerance phenotype. CYCH;1 is predominantly expressed in guard cells, and its expression was substantially down-regulated by dehydration. Transpiration of intact leaves was reduced in cych;1 RNAi plants compared with the wild-type control in light but not in darkness. CYCH;1 down-regulation impaired blue light-induced stomatal opening but did not affect guard cell development or abscisic acid-mediated stomatal closure. Microarray and real-time polymerase chain reaction analyses indicated that CYCH;1 did not regulate the expression of abscisic acid-responsive genes or light-induced stomatal opening signaling determinants, such as MYB60, MYB61, Hypersensitive to red and blue1, and Protein phosphatase7. CYCH;1 down-regulation induced the expression of redox homeostasis genes, such as LIPOXYGENASE3 (LOX3), LOX4, ARABIDOPSIS GLUTATHIONE PEROXIDASE 7 (ATGPX7), EARLY LIGHT-INDUCIBLE PROTEIN1 (ELIP1), and ELIP2, and increased hydrogen peroxide production in guard cells. Furthermore, loss-of-function mutations in CDKD;2 or CDKD;3 did not affect responsiveness to drought stress, suggesting that CYCH;1 regulates the drought stress response in a CDKD-independent manner. We propose that CYCH;1 regulates blue light-mediated stomatal opening by controlling reactive oxygen species homeostasis.

Stomatal lock-open, a consequence of epidermal cell death, follows transient suppression of stomatal opening in barley attacked by Blumeria graminis.

PubMed

Prats, Elena; Gay, Alan P; Mur, Luis A J; Thomas, Barry J; Carver, Timothy L W

2006-01-01

Blumeria graminis f.sp. hordei (Bgh) attack disrupted stomatal behaviour, and hence leaf water conductance (g(l)), in barley genotypes Pallas and Risø-S (susceptible), P01 (with Mla1 conditioning a hypersensitive response; HR), and P22 and Risø-R (with mlo5 conditioning papilla-based penetration resistance). Inoculation caused some stomatal closure well before the fungus attempted infection. Coinciding with epidermal cell penetration, stomatal opening in light was also impeded, although stomata of susceptible and mlo5 lines remained largely able to close in darkness. Following infection, in susceptible lines stomata closed in darkness but opening in light was persistently impeded. In Risø-R, stomata recovered nearly complete function by approximately 30 h after inoculation, i.e. after penetration resistance was accomplished. In P01, stomata became locked open and unable to close in darkness shortly after epidermal cells died due to HR. In the P22 background, mlo5 penetration resistance was often followed by consequential death of attacked cells, and here too stomata became locked open, but not until approximately 24 h after pathogen attack had ceased. The influence of epidermal cell death was localized, and only affected stomata within one or two cells distance. These stomata were unable to close not only in darkness but also after application of abscisic acid and in wilted leaves suffering drought. Thus, resistance to Bgh based on HR or associated with cell death may have previously unsuspected negative consequences for the physiological health of apparently 'disease-free' plants. The results are discussed in relation to the control of stomatal aperture in barley by epidermal cells.

Anion channels: master switches of stress responses.

PubMed

Roelfsema, M Rob G; Hedrich, Rainer; Geiger, Dietmar

2012-04-01

During stress, plant cells activate anion channels and trigger the release of anions across the plasma membrane. Recently, two new gene families have been identified that encode major groups of anion channels. The SLAC/SLAH channels are characterized by slow voltage-dependent activation (S-type), whereas ALMT genes encode rapid-activating channels (R-type). Both S- and R-type channels are stimulated in guard cells by the stress hormone ABA, which leads to stomatal closure. Besides their role in ABA-dependent stomatal movement, anion channels are also activated by biotic stress factors such as microbe-associated molecular patterns (MAMPs). Given that anion channels occur throughout the plant kingdom, they are likely to serve a general function as master switches of stress responses. Copyright © 2012 Elsevier Ltd. All rights reserved.

Plant responsiveness to root–root communication of stress cues

PubMed Central

Falik, Omer; Mordoch, Yonat; Ben-Natan, Daniel; Vanunu, Miriam; Goldstein, Oron; Novoplansky, Ariel

2012-01-01

Background and Aims Phenotypic plasticity is based on the organism's ability to perceive, integrate and respond to multiple signals and cues informative of environmental opportunities and perils. A growing body of evidence demonstrates that plants are able to adapt to imminent threats by perceiving cues emitted from their damaged neighbours. Here, the hypothesis was tested that unstressed plants are able to perceive and respond to stress cues emitted from their drought- and osmotically stressed neighbours and to induce stress responses in additional unstressed plants. Methods Split-root Pisum sativum, Cynodon dactylon, Digitaria sanguinalis and Stenotaphrum secundatum plants were subjected to osmotic stress or drought while sharing one of their rooting volumes with an unstressed neighbour, which in turn shared its other rooting volume with additional unstressed neighbours. Following the kinetics of stomatal aperture allowed testing for stress responses in both the stressed plants and their unstressed neighbours. Key Results In both P. sativum plants and the three wild clonal grasses, infliction of osmotic stress or drought caused stomatal closure in both the stressed plants and in their unstressed neighbours. While both continuous osmotic stress and drought induced prolonged stomatal closure and limited acclimation in stressed plants, their unstressed neighbours habituated to the stress cues and opened their stomata 3–24 h after the beginning of stress induction. Conclusions The results demonstrate a novel type of plant communication, by which plants might be able to increase their readiness to probable future osmotic and drought stresses. Further work is underway to decipher the identity and mode of operation of the involved communication vectors and to assess the potential ecological costs and benefits of emitting and perceiving drought and osmotic stress cues under various ecological scenarios. PMID:22408186

Plant responsiveness to root-root communication of stress cues.

PubMed

Falik, Omer; Mordoch, Yonat; Ben-Natan, Daniel; Vanunu, Miriam; Goldstein, Oron; Novoplansky, Ariel

2012-07-01

Phenotypic plasticity is based on the organism's ability to perceive, integrate and respond to multiple signals and cues informative of environmental opportunities and perils. A growing body of evidence demonstrates that plants are able to adapt to imminent threats by perceiving cues emitted from their damaged neighbours. Here, the hypothesis was tested that unstressed plants are able to perceive and respond to stress cues emitted from their drought- and osmotically stressed neighbours and to induce stress responses in additional unstressed plants. Split-root Pisum sativum, Cynodon dactylon, Digitaria sanguinalis and Stenotaphrum secundatum plants were subjected to osmotic stress or drought while sharing one of their rooting volumes with an unstressed neighbour, which in turn shared its other rooting volume with additional unstressed neighbours. Following the kinetics of stomatal aperture allowed testing for stress responses in both the stressed plants and their unstressed neighbours. In both P. sativum plants and the three wild clonal grasses, infliction of osmotic stress or drought caused stomatal closure in both the stressed plants and in their unstressed neighbours. While both continuous osmotic stress and drought induced prolonged stomatal closure and limited acclimation in stressed plants, their unstressed neighbours habituated to the stress cues and opened their stomata 3-24 h after the beginning of stress induction. The results demonstrate a novel type of plant communication, by which plants might be able to increase their readiness to probable future osmotic and drought stresses. Further work is underway to decipher the identity and mode of operation of the involved communication vectors and to assess the potential ecological costs and benefits of emitting and perceiving drought and osmotic stress cues under various ecological scenarios.

Functional roles of the pepper RING finger protein gene, CaRING1, in abscisic acid signaling and dehydration tolerance.

PubMed

Lim, Chae Woo; Hwang, Byung Kook; Lee, Sung Chul

2015-09-01

Plants are constantly exposed to a variety of biotic and abiotic stresses, which include pathogens and conditions of high salinity, low temperature, and drought. Abscisic acid (ABA) is a major plant hormone involved in signal transduction pathways that mediate the defense response of plants to abiotic stress. Previously, we isolated Ring finger protein gene (CaRING1) from pepper (Capsicum annuum), which is associated with resistance to bacterial pathogens, accompanied by hypersensitive cell death. Here, we report a new function of the CaRING1 gene product in the ABA-mediated defense responses of plants to dehydration stress. The expression of the CaRING1 gene was induced in pepper leaves treated with ABA or exposed to dehydration or NaCl. Virus-induced gene silencing of CaRING1 in pepper plants exhibited low degree of ABA-induced stomatal closure and high levels of transpirational water loss in dehydrated leaves. These led to be more vulnerable to dehydration stress in CaRING1-silenced pepper than in the control pepper, accompanied by reduction of ABA-regulated gene expression and low accumulation of ABA and H2O2. In contrast, CaRING1-overexpressing transgenic plants showed enhanced sensitivity to ABA during the seedling growth and establishment. These plants were also more tolerant to dehydration stress than the wild-type plants because of high ABA accumulation, enhanced stomatal closure and increased expression of stress-responsive genes. Together, these results suggest that the CaRING1 acts as positive factor for dehydration tolerance in Arabidopsis by modulating ABA biosynthesis and ABA-mediated stomatal closing and gene expression.

Stomatal closure of Pelargonium × hortorum in response to soil water deficit is associated with decreased leaf water potential only under rapid soil drying.

PubMed

Boyle, Richard K A; McAinsh, Martin; Dodd, Ian C

2016-01-01

Soil water deficits applied at different rates and for different durations can decrease both stomatal conductance (gs ) and leaf water potential (Ψleaf ). Understanding the physiological mechanisms regulating these responses is important in sustainable irrigation scheduling. Glasshouse-grown, containerized Pelargonium × hortorum BullsEye plants were irrigated either daily at various fractions of plant evapotranspiration (100, 75 and 50% ET) for 20 days or irrigation was withheld for 4 days. Xylem sap was collected and gs and Ψleaf were measured on days 15 and 20, and on days 16-19 for the respective treatments. Xylem sap pH and NO3 (-) and Ca(2+) concentrations did not differ between irrigation treatments. Xylem abscisic acid (ABA) concentrations ([ABA]xyl ) increased within 24 h of irrigation being withheld whilst gs and Ψleaf decreased. Supplying irrigation at a fraction of daily ET produced a similar relationship between [ABA]xyl and gs , but did not change Ψleaf . Treatment differences occurred independently of whether Ψleaf was measured in whole leaves with a pressure chamber, or in the lamina with a thermocouple psychrometer. Plants that were irrigated daily showed lower [ABA]xyl than plants from which irrigation was withheld, even at comparable soil moisture content. This implies that regular re-watering attenuates ABA signaling due to maintenance of soil moisture in the upper soil levels. Crucially, detached leaves supplied with synthetic ABA showed a similar relationship between [ABA]xyl and gs as intact plants, suggesting that stomatal closure of P. hortorum in response to soil water deficit is primarily an ABA-induced response, independent of changes in Ψleaf . © 2015 Scandinavian Plant Physiology Society.

Soil Moisture (SMAP) and Vapor Pressure Deficit Controls on Evaporative Fraction over the Continental U.S.

NASA Astrophysics Data System (ADS)

Salvucci, G.; Rigden, A. J.; Gianotti, D.; Entekhabi, D.

2017-12-01

We analyze the control over evapotranspiration (ET) imposed by soil moisture limitations and stomatal closure due to vapor pressure deficit (VPD) across the United States using estimates of satellite-derived soil moisture from SMAP and a meteorological, data-driven ET estimate over a two year period at over 1000 locations. The ET data are developed independent of soil moisture using the emergent relationship between the diurnal cycle of the relative humidity profile and ET based on ETRHEQ (Salvucci and Gentine (2013), PNAS, 110(16): 6287-6291, Rigden and Salvucci, 2015, WRR, 51(4): 2951-2973; Rigden and Salvucci, 2017, GCB, 23(3) 1140-1151). The key advantage of using this approach to estimate ET is that no measurements of surface limiting factors (soil moisture, leaf area, canopy conductance) are required; instead, ET is estimated from only meteorological data. The combination of these two independent datasets allows for a unique spatial analysis of the control on ET imposed by the availability of soil moisture vs. VPD. Spatial patterns of limitations are inferred by fitting the ETRHEQ-inferred surface conductance to a weighted sum of a Jarvis type stomatal conductance model and bare soil evaporation conductance model, with separate moisture-dependent evaporation efficiency relations for bare soil and vegetation. Spatial patterns are visualized by mapping the optimal curve fitting coefficients and by conducting sensitivity analyses of the resulting fitted model across the Unites States. Results indicate regional variations in rate-limiting factors, and suggest that in some areas the VPD effect on stomatal closure is strong enough to induce a decrease in ET under projected climate change, despite an increase in atmospheric drying (and thus evaporative demand).

Calcium specificity signaling mechanisms in abscisic acid signal transduction in Arabidopsis guard cells

PubMed Central

Brandt, Benjamin; Munemasa, Shintaro; Wang, Cun; Nguyen, Desiree; Yong, Taiming; Yang, Paul G; Poretsky, Elly; Belknap, Thomas F; Waadt, Rainer; Alemán, Fernando; Schroeder, Julian I

2015-01-01

A central question is how specificity in cellular responses to the eukaryotic second messenger Ca2+ is achieved. Plant guard cells, that form stomatal pores for gas exchange, provide a powerful system for in depth investigation of Ca2+-signaling specificity in plants. In intact guard cells, abscisic acid (ABA) enhances (primes) the Ca2+-sensitivity of downstream signaling events that result in activation of S-type anion channels during stomatal closure, providing a specificity mechanism in Ca2+-signaling. However, the underlying genetic and biochemical mechanisms remain unknown. Here we show impairment of ABA signal transduction in stomata of calcium-dependent protein kinase quadruple mutant plants. Interestingly, protein phosphatase 2Cs prevent non-specific Ca2+-signaling. Moreover, we demonstrate an unexpected interdependence of the Ca2+-dependent and Ca2+-independent ABA-signaling branches and the in planta requirement of simultaneous phosphorylation at two key phosphorylation sites in SLAC1. We identify novel mechanisms ensuring specificity and robustness within stomatal Ca2+-signaling on a cellular, genetic, and biochemical level. DOI: http://dx.doi.org/10.7554/eLife.03599.001 PMID:26192964

Correction: Calcium specificity signaling mechanisms in abscisic acid signal transduction in Arabidopsis guard cells

DOE PAGES

Brandt, Benjamin; Munemasa, Shintaro; Wang, Cun; ...

2015-07-20

One central question is how specificity in cellular responses to the eukaryotic second messenger Ca 2+ is achieved. Plant guard cells, that form stomatal pores for gas exchange, provide a powerful system for in depth investigation of Ca 2+-signaling specificity in plants. In intact guard cells, abscisic acid (ABA) enhances (primes) the Ca 2+-sensitivity of downstream signaling events that result in activation of S-type anion channels during stomatal closure, providing a specificity mechanism in Ca 2+-signaling. However, the underlying genetic and biochemical mechanisms remain unknown. Here we show impairment of ABA signal transduction in stomata of calcium-dependent protein kinase quadruplemore » mutant plants. Interestingly, protein phosphatase 2Cs prevent non-specific Ca 2+-signaling. Moreover, we demonstrate an unexpected interdependence of the Ca 2+-dependent and Ca 2+-independent ABA-signaling branches and the in planta requirement of simultaneous phosphorylation at two key phosphorylation sites in SLAC1. We identify novel mechanisms ensuring specificity and robustness within stomatal Ca 2+-signaling on a cellular, genetic, and biochemical level.« less

Correction: Calcium specificity signaling mechanisms in abscisic acid signal transduction in Arabidopsis guard cells

DOE PAGES

Brandt, Benjamin; Munemasa, Shintaro; Wang, Cun; ...

2015-07-29

A central question is how specificity in cellular responses to the eukaryotic second messenger Ca 2+ is achieved. Plant guard cells, that form stomatal pores for gas exchange, provide a powerful system for in depth investigation of Ca 2+-signaling specificity in plants. In intact guard cells, abscisic acid (ABA) enhances (primes) the Ca 2+-sensitivity of downstream signaling events that result in activation of S-type anion channels during stomatal closure, providing a specificity mechanism in Ca 2+-signaling. However, the underlying genetic and biochemical mechanisms remain unknown. Here we show impairment of ABA signal transduction in stomata of calcium-dependent protein kinase quadruplemore » mutant plants. Interestingly, protein phosphatase 2Cs prevent non-specific Ca 2+-signaling. Moreover, we demonstrate an unexpected interdependence of the Ca 2+-dependent and Ca 2+-independent ABA-signaling branches and the in planta requirement of simultaneous phosphorylation at two key phosphorylation sites in SLAC1. We identify novel mechanisms ensuring specificity and robustness within stomatal Ca 2+-signaling on a cellular, genetic, and biochemical level.« less

Photosynthetic Traits of Plants and the Biochemical Profile of Tomato Fruits Are Influenced by Grafting, Salinity Stress, and Growing Season.

PubMed

Marsic, Nina Kacjan; Vodnik, Dominik; Mikulic-Petkovsek, Maja; Veberic, Robert; Sircelj, Helena

2018-06-06

Changes in the photosynthetic traits of plants and metabolic composition of fruits of two tomato cultivars, grafted onto two rootstocks, grown in three salinity levels were studied in two growing periods during the season. Increased salinity stress conditions lowered water potential, stomatal conductance, and transpiration rate of grafted tomato plants, in both growing periods. Water deficit induced stomatal closure, which resulted in stomatal limitation of photosynthesis. The proline content in tomato leaves increased and was closely correlated with salinity. Some of the quality parameters of tomato fruits were affected by rootstock. The sugar/acid ratio was the highest in fruits of 'Belle'/'Maxifort' grafts. With increasing salt stress conditions from 40 to 60 mM NaCl, the lycopene content increased and ascorbic acid content decreased in fruits of 'Gardel'/'Maxifort' grafts, indicating the ability of this scion/rootstock combination to mitigate the toxicity effect of salinity stress. A higher phenolics concentration in fruits from the first growing period may be an additional indicator of stress, caused by higher temperatures and solar radiation, compared with the later period.

Partially Testing a Process Model for Understanding Victim Responses to an Anticipated Worksite Closure

ERIC Educational Resources Information Center

Blau, Gary

2007-01-01

This study partially tested a recent process model for understanding victim responses to worksite/function closure (W/FC) proposed by Blau [Blau, G. (2006). A process model for understanding victim responses to worksite/function closure. "Human Resource Management Review," 16, 12-28], in a pharmaceutical manufacturing site. Central to the model…

Acclimation of Photosynthesis to Low Leaf Water Potentials 1

PubMed Central

Matthews, Mark A.; Boyer, John S.

1984-01-01

Photosynthesis is reduced at low leaf water potentials (Ψl) but repeated water deficits can decrease this reduction, resulting in photosynthetic acclimation. The contribution of the stomata and the chloroplasts to this acclimation is unknown. We evaluated stomatal and chloroplast contributions when soil-grown sunflower (Helianthus annuus L.) plants were subjected to water deficit pretreatments for 2 weeks. The relationship between photosynthesis and Ψl, determined from gas-exchange and isopiestic thermocouple psychometry, was shifted 3 to 4 bars towards lower Ψl, in pretreated plants. Leaf diffusive resistance was similarly affected. Chloroplast activity, demonstrated in situ with measurements of quantum yield and the capacity to fix CO2 at all partial pressures of CO2, and in vitro by photosystem II activity of isolated organelles, was inhibited at low Ψl but less in pretreated plants than in control plants. The magnitude of this inhibition indicated that decreases in chloroplast activity contributed more than closure of stomata both to losses in photosynthesis and to the acclimation of photosynthesis to low Ψl. PMID:16663372

Acclimation of photosynthesis to low leaf water potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, M.A.; Boyer, J.S.

1984-01-01

Photosynthesis is reduced at low leaf water potentials (PSI/sub l/) but repeated water deficits can decrease this reduction, resulting in photosynthetic acclimation. The contribution of the stomata and the chloroplasts to this acclimation is unknown. The authors evaluated stomatal and chloroplast contributions when soil-grown sunflower (Helianthus annuus L.) plants were subjected to water deficit pretreatments for 2 weeks. The relationship between photosynthesis and PSI/sub l/, determined from gas-exchange and isopiestic thermocouple psychometry, was shifted 3 to 4 bars towards lower PSI/sub l/ in pretreated plants. Leaf diffusive resistance was similarly affected. Chloroplast activity, demonstrated in situ with measurements of quantummore » yield and the capacity to fix CO/sub 2/ at all partial pressures of CO/sub 2/, and in vitro by photosystem II activity of isolated organelles, was inhibited at low PSI/sub l/ but less in pretreated plants than in control plants. The magnitude of this inhibition indicated that decreases in chloroplast activity contributed more than closure of stomata both to losses in photosynthesis and to the acclimation of photosynthesis to low PSI/sub l/. 32 references, 8 figures.« less

Stomata open at night in pole-sized and mature ponderosa pine: implications for O3 exposure metrics

Treesearch

Nancy Grulke; R. Alonso; T. Nguyen; C. Cascio; W. Dobrowolski

2004-01-01

Ponderosa pine (Pinus ponderosa Dougl. exLaws.) is widely distributed in the western USA.We report the lack of stomatal closure at night in early summer for ponderosa pine at two of three sites investigated. Trees at a third site with lower nitrogen dioxide and nitric acid exposure, but greater drought stress, had slightly open stomata at night in...

Identification and functional characterization of the pepper CaDRT1 gene involved in the ABA-mediated drought stress response.

PubMed

Baek, Woonhee; Lim, Sohee; Lee, Sung Chul

2016-05-01

Plants are constantly challenged by various environmental stresses, including high salinity and drought, and they have evolved defense mechanisms to counteract the deleterious effects of these stresses. The plant hormone abscisic acid (ABA) regulates plant growth and developmental processes and mediates abiotic stress responses. Here, we identified the Capsicum annuum DRought Tolerance 1 (CaDRT1) gene from pepper leaves treated with ABA. CaDRT1 was strongly expressed in pepper leaves in response to environmental stresses and after ABA treatment, suggesting that the CaDRT1 protein functions in the abiotic stress response. Knockdown expression of CaDRT1 via virus-induced gene silencing resulted in a high level of drought susceptibility, and this was characterized by increased transpirational water loss via decreased stomatal closure. CaDRT1-overexpressing (OX) Arabidopsis plants exhibited an ABA-hypersensitive phenotype during the germinative, seedling, and adult stages. Additionally, these CaDRT1-OX plants exhibited a drought-tolerant phenotype characterized by low levels of transpirational water loss, high leaf temperatures, increased stomatal closure, and enhanced expression levels of drought-responsive genes. Taken together, our results suggest that CaDRT1 is a positive regulator of the ABA-mediated drought stress response.

Central Metabolic Responses to Ozone and Herbivory Affect Photosynthesis and Stomatal Closure1[OPEN

PubMed Central

Khaling, Eliezer; Lassueur, Steve

2016-01-01

Plants have evolved adaptive mechanisms that allow them to tolerate a continuous range of abiotic and biotic stressors. Tropospheric ozone (O3), a global anthropogenic pollutant, directly affects living organisms and ecosystems, including plant-herbivore interactions. In this study, we investigate the stress responses of Brassica nigra (wild black mustard) exposed consecutively to O3 and the specialist herbivore Pieris brassicae. Transcriptomics and metabolomics data were evaluated using multivariate, correlation, and network analyses for the O3 and herbivory responses. O3 stress symptoms resembled those of senescence and phosphate starvation, while a sequential shift from O3 to herbivory induced characteristic plant defense responses, including a decrease in central metabolism, induction of the jasmonic acid/ethylene pathways, and emission of volatiles. Omics network and pathway analyses predicted a link between glycerol and central energy metabolism that influences the osmotic stress response and stomatal closure. Further physiological measurements confirmed that while O3 stress inhibited photosynthesis and carbon assimilation, sequential herbivory counteracted the initial responses induced by O3, resulting in a phenotype similar to that observed after herbivory alone. This study clarifies the consequences of multiple stress interactions on a plant metabolic system and also illustrates how omics data can be integrated to generate new hypotheses in ecology and plant physiology. PMID:27758847

Importance of Biotic vs Abiotic Controls on VOC Emissions from Ponderosa Pine

NASA Astrophysics Data System (ADS)

Eller, A. S.; Harley, P. C.; Monson, R. K.

2011-12-01

The emissions of VOCs, including monoterpenes (MTs) and 2-methyl-3-buten-2-ol (MBO), from ponderosa pine can be important contributors to the regional production of ozone and secondary organic aerosols in the Western United States. The goal of this study was to better characterize the influences of biotic and abiotic factors on the emissions of these compounds. Using PTR-MS coupled with measurements of photosynthesis and stomatal conductance (gs) we generated light and temperature curves from intact needles of mature ponderosa pine trees and used abscisic acid (ABA) to reduce gs and photosynthesis under constant light and temperature conditions. Stomatal conductance and photosynthesis were almost perfectly correlated during all our measurements, so we were unable to separate their influences. We found that increasing temperature by 10 oC increased emissions of both MTs and MBO by 80-120% even though gs and photosynthesis were reduced by ~50%. Light curves performed at 30 oC showed that gs and photosynthesis exhibited a strong control over MT and MBO emissions although the effect was more pronounced for MBO than MT emissions. In most cases a 60% reduction in gs and photosynthesis caused a ~50% reduction in MBO emissions and a 5-20% reduction in MT emissions. Using ABA we were able to induce stomatal closure while maintaining a constant light and temperature environment and we found that stomatal closure due to ABA caused declines in MT and MBO emissions that were similar in magnitude to those seen in the light curves. When compared at the same light and temperature conditions, individuals with lower gs and photosynthesis did not necessarily have lower emissions than those with higher gs and photosynthesis, indicating that gs and photosynthesis may not be good predictors of emissions between individuals, but within each individual the instantaneous changes in gs and photosynthesis did appear to exert control over the emissions of VOCs. These data show that plant physiology is an important constraint in regulating the instantaneous emissions of VOCs, but also that the relationships are modified by external temperature, probably through the increased volatility of the VOCs.

Role of leaf hydraulic conductance in the regulation of stomatal conductance in almond and olive in response to water stress.

PubMed

Hernandez-Santana, Virginia; Rodriguez-Dominguez, Celia M; Fernández, J Enrique; Diaz-Espejo, Antonio

2016-06-01

The decrease of stomatal conductance (gs) is one of the prime responses to water shortage and the main determinant of yield limitation in fruit trees. Understanding the mechanisms related to stomatal closure in response to imposed water stress is crucial for correct irrigation management. The loss of leaf hydraulic functioning is considered as one of the major factors triggering stomatal closure. Thus, we conducted an experiment to quantify the dehydration response of leaf hydraulic conductance (Kleaf) and its impact on gs in two Mediterranean fruit tree species, one deciduous (almond) and one evergreen (olive). Our hypothesis was that a higher Kleaf would be associated with a higher gs and that the reduction in Kleaf would predict the reduction in gs in both species. We measured Kleaf in olive and almond during a cycle of irrigation withholding. We also compared the results of two methods to measure Kleaf: dynamic rehydration kinetics and evaporative flux methods. In addition, determined gs, leaf water potential (Ψleaf), vein density, photosynthetic capacity and turgor loss point. Results showed that gs was higher in almond than in olive and so was Kleaf (Kmax = 4.70 and 3.42 mmol s(-1) MPa(-1) m(-2), in almond and olive, respectively) for Ψleaf > -1.2 MPa. At greater water stress levels than -1.2 MPa, however, Kleaf decreased exponentially, being similar for both species, while gs was still higher in almond than in olive. We conclude that although the Kleaf decrease with increasing water stress does not drive unequivocally the gs response to water stress, Kleaf is the variable most strongly related to the gs response to water stress, especially in olive. Other variables such as the increase in abscisic acid (ABA) may be playing an important role in gs regulation, although in our study the gs-ABA relationship did not show a clear pattern. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Predicting plant vulnerability to drought in biodiverse regions using functional traits.

PubMed

Skelton, Robert Paul; West, Adam G; Dawson, Todd E

2015-05-05

Attempts to understand mechanisms underlying plant mortality during drought have led to the emergence of a hydraulic framework describing distinct hydraulic strategies among coexisting species. This framework distinguishes species that rapidly decrease stomatal conductance (gs), thereby maintaining high water potential (Px; isohydric), from those species that maintain relatively high gs at low Px, thereby maintaining carbon assimilation, albeit at the cost of loss of hydraulic conductivity (anisohydric). This framework is yet to be tested in biodiverse communities, potentially due to a lack of standardized reference values upon which hydraulic strategies can be defined. We developed a system of quantifying hydraulic strategy using indices from vulnerability curves and stomatal dehydration response curves and tested it in a speciose community from South Africa's Cape Floristic Region. Degree of stomatal regulation over cavitation was defined as the margin between Px at stomatal closure (Pg12) and Px at 50% loss of conductivity. To assess relationships between hydraulic strategy and mortality mechanisms, we developed proxies for carbon limitation and hydraulic failure using time since Pg12 and loss of conductivity at minimum seasonal Px, respectively. Our approach captured continuous variation along an isohydry/anisohydry axis and showed that this variation was linearly related to xylem safety margin. Degree of isohydry/anisohydry was associated with contrasting predictions for mortality during drought. Merging stomatal regulation strategies that represent an index of water use behavior with xylem vulnerability facilitates a more comprehensive framework with which to characterize plant response to drought, thus opening up an avenue for predicting the response of diverse communities to future droughts.

Different blocking effects of HgCl2 and NaCl on aquaporins of pepper plants.

PubMed

Martínez-Ballesta, M Carmen; Diaz, Rafael; Martínez, Vicente; Carvajal, Micaela

2003-12-01

In this study we have compared the short-term effects of both NaCl and HgCl2 on aquaporins of Capsicum annuum L. plants, in order to determine whether or not they are similar. Stomatal conductance, turgor, root hydraulic conductance and water status were measured after 0.5, 2, 4 and 6 h of NaCl (60 mmol/L) or HgCl2 (50 micromol/L) treatment. When 60 mmol/L NaCl was added to the nutrient solution, a large decrease in stomatal conductance was observed after 2 h. However, when HgCl2 (50 micromol/L) was added, the decrease occurred after 4 h. The number of open stomata closed was always lower in plants treated with HgCl2 than in plants treated with NaCl. The water content of the Hg(2+)-treated plants was decreased, compared with controls and NaCl-treated. The root hydraulic conductance decreased after HgCl2 and NaCl treatment plants. Turgor of leaf epidermal cells was greatly reduced in plants treated with HgCl2, but remained constant in the NaCl treatment, compared with control plants. The fact that the stomatal conductance was reduced more rapidly after NaCl addition, followed by the stomatal closure, and that both water content and turgor did not differ from the control suggests that in NaCl-treated plants there must be a signal moving from root to shoot. Therefore, the control of plant homeostasis through a combined regulation of root and stomatal exchanges may be dependent on aquaporin regulation.

Tubulin perturbation leads to unexpected cell wall modifications and affects stomatal behaviour in Populus

DOE PAGES

Swamy, Prashant S.; Hu, Hao; Pattathil, Sivakumar; ...

2015-08-05

Cortical microtubules are integral to plant morphogenesis, cell wall synthesis, and stomatal behaviour, presumably by governing cellulose microfibril orientation. Genetic manipulation of tubulins often leads to abnormal plant development, making it difficult to probe additional roles of cortical microtubules in cell wall biogenesis. Here, it is shown that expressing post-translational C-terminal modification mimics of α-tubulin altered cell wall characteristics and guard cell dynamics in transgenic Populus tremula x alba that otherwise appear normal. 35S promoter-driven transgene expression was high in leaves but unusually low in xylem, suggesting high levels of tubulin transgene expression were not tolerated in wood-forming tissues duringmore » regeneration of transformants. Cellulose, hemicellulose, and lignin contents were unaffected in transgenic wood, but expression of cell wall-modifying enzymes, and extractability of lignin-bound pectin and xylan polysaccharides were increased in developing xylem. The results suggest that pectin and xylan polysaccharides deposited early during cell wall biogenesis are more sensitive to subtle tubulin perturbation than cellulose and matrix polysaccharides deposited later. Tubulin perturbation also affected guard cell behaviour, delaying drought-induced stomatal closure as well as light-induced stomatal opening in leaves. Pectins have been shown to confer cell wall flexibility critical for reversible stomatal movement, and results presented here are consistent with microtubule involvement in this process. In conclusion, taken together, the data show the value of growth-compatible tubulin perturbations for discerning microtubule functions, and add to the growing body of evidence for microtubule involvement in non-cellulosic polysaccharide assembly during cell wall biogenesis.« less

Modelling water use efficiency in a dynamic environment: An example using Arabidopsis thaliana.

PubMed

Vialet-Chabrand, S; Matthews, J S A; Brendel, O; Blatt, M R; Wang, Y; Hills, A; Griffiths, H; Rogers, S; Lawson, T

2016-10-01

Intrinsic water use efficiency (Wi), the ratio of net CO2 assimilation (A) over stomatal conductance to water vapour (gs), is a complex trait used to assess plant performance. Improving Wi could lead in theory to higher productivity or reduced water usage by the plant, but the physiological traits for improvement and their combined effects on Wi have not been clearly identified. Under fluctuating light intensity, the temporal response of gs is an order of magnitude slower than A, which results in rapid variations in Wi. Compared to traditional approaches, our new model scales stoma behaviour at the leaf level to predict gs and A during a diurnal period, reproducing natural fluctuations of light intensity, in order to dissect Wi into traits of interest. The results confirmed the importance of stomatal density and photosynthetic capacity on Wi but also revealed the importance of incomplete stomatal closure under dark conditions as well as stomatal sensitivity to light intensity. The observed continuous decrease of A and gs over the diurnal period was successfully described by negative feedback of the accumulation of photosynthetic products. Investigation into the impact of leaf anatomy on temporal responses of A, gs and Wi revealed that a high density of stomata produces the most rapid response of gs but may result in lower Wi. Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Within-catchment variation in regulation of water use by eucalypts, and the roles of stomatal anatomy and physiology

NASA Astrophysics Data System (ADS)

Gharun, Mana; Turnbull, Tarryn; Adams, Mark

2014-05-01

Understanding how environmental cues impact water use of forested catchments is crucial for accurate calculation of water balance and effective catchment management in terrestrial ecosystems. We characterised structural and physiological properties of leaves and canopies of Eucalyptus delegatensis, E. pauciflora and E. radiata, the most common species in high-country catchments in temperate Australia. These properties were related to whole-tree water transport to assess differences in water use strategies among the three species. Stomatal conductance, instantaneous transpiration efficiency, stomatal occlusion (through cuticular ledges) and leaf area index differed significantly among species. Whole-tree water use of all species was strongly coupled to changes in vapour pressure deficit (VPD) and photosynthetically active radiation (Q), yet stomatal closure reduced water transport at VPD > 1 kPa in all species, even when soil water was not limiting. The observed differences in leaf traits and related water use strategies reflect species-specific adaptations to dominant environmental conditions within the landscape matrix of catchments. The generalist E. radiata seems to follow an opportunistic, while the two more spatially restricted species have adopted a pessimistic water use strategy. Catchment-scale models of carbon and water fluxes will need to reflect such variation in structure and function, if they are to fully capture species effects on water balance and yield.

OsPRX2 contributes to stomatal closure and improves potassium deficiency tolerance in rice.

PubMed

Mao, Xiaohui; Zheng, Yanmei; Xiao, Kaizhuan; Wei, Yidong; Zhu, Yongsheng; Cai, Qiuhua; Chen, Liping; Xie, Huaan; Zhang, Jianfu

2018-01-01

Peroxiredoxins (Prxs) which are thiol-based peroxidases have been implicated in the toxic reduction and intracellular concentration regulation of hydrogen peroxide. In Arabidopsis thaliana At2-CysPrxB (At5g06290) has been demonstrated to be essential in maintaining the water-water cycle for proper H 2 O 2 scavenging. Although the mechanisms of 2-Cys Prxs have been extensively studied in Arabidopsis thaliana, the function of 2-Cys Prxs in rice is unclear. In this study, a rice homologue gene of At2-CysPrxB, OsPRX2 was investigated aiming to characterize the effect of 2-Cys Prxs on the K + -deficiency tolerance in rice. We found that OsPRX2 was localized in the chloroplast. Overexpressed OsPRX2 causes the stomatal closing and K + -deficiency tolerance increasing, while knockout of OsPRX2 lead to serious defects in leaves phenotype and the stomatal opening under the K + -deficiency tolerance. Detection of K + accumulation, antioxidant activity of transgenic plants under the starvation of potassium, further confirmed that OsPRX2 is a potential target for engineering plants with improved potassium deficiency tolerance. Copyright © 2017 Elsevier Inc. All rights reserved.

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 results, which are corroborated by measurements of xylem sap flux density, needle gas exchange, and measurements of growth and δ13C along moisture gradients within each watershed, suggest that drought-induced stomatal closure is probably not the cause of 20th century divergence in the Brooks Range.

Transpiration and stomatal conductance in a young secondary tropical montane forest: contrasts between native trees and invasive understorey shrubs.

PubMed

Ghimire, Chandra Prasad; Bruijnzeel, L Adrian; Lubczynski, Maciek W; Zwartendijk, Bob W; Odongo, Vincent Omondi; Ravelona, Maafaka; van Meerveld, H J Ilja

2018-04-21

It has been suggested that vigorous secondary tropical forests can have very high transpiration rates, but sap flow and stomatal conductance dynamics of trees and shrubs in these forests are understudied. In an effort to address this knowledge gap, sap flow (thermal dissipation method, 12 trees) and stomatal conductance (porometry, six trees) were measured for young (5-7 years) Psiadia altissima (DC.) Drake trees, a widely occurring species dominating young regrowth following abandonment of swidden agriculture in upland eastern Madagascar. In addition, stomatal conductance (gs) was determined for three individuals of two locally common invasive shrubs (Lantana camara L. and Rubus moluccanus L.) during three periods with contrasting soil moisture conditions. Values of gs for the three investigated species were significantly higher and more sensitive to climatic conditions during the wet period compared with the dry period. Further, gs of the understorey shrubs was much more sensitive to soil moisture content than that of the trees. Tree transpiration rates (Ec) were relatively stable during the dry season and were only affected somewhat by soil water content at the end of the dry season, suggesting the trees had continued access to soil water despite drying out of the topsoil. The Ec exhibited a plateau-shaped relation with vapour pressure deficit (VPD), which was attributed to stomatal closure at high VPD. Vapour pressure deficit was the major driver of variation in Ec, during both the wet and the dry season. Overall water use of the trees was modest, possibly reflecting low site fertility after three swidden cultivation cycles. The observed contrast in gs response to soil water and climatic conditions for the trees and shrubs underscores the need to take root distributions into account when modelling transpiration from regenerating tropical forests.

Polychromatic Supplemental Lighting from underneath Canopy Is More Effective to Enhance Tomato Plant Development by Improving Leaf Photosynthesis and Stomatal Regulation

PubMed Central

Song, Yu; Jiang, Chengyao; Gao, Lihong

2016-01-01

Light insufficient stress caused by canopy interception and mutual shading is a major factor limiting plant growth and development in intensive crop cultivation. Supplemental lighting can be used to give light to the lower canopy leaves and is considered to be an effective method to cope with low irradiation stress. Leaf photosynthesis, stomatal regulation, and plant growth and development of young tomato plants were examined to estimate the effects of supplemental lighting with various composite spectra and different light orientations. Light-emitting diodes (LEDs) of polychromatic light quality, red + blue (R/B), white + red + blue (W/R/B), white + red + far-red (W/R/FR), and white + blue (W/B) were assembled from the underneath canopy or from the inner canopy as supplemental lighting resources. The results showed that the use of supplemental lighting significantly increased the photosynthetic efficiency, and reduced stomatal closure while promoting plant growth. Among all supplemental lighting treatments, the W/R/B and W/B from the underneath canopy had best performance. The different photosynthetic performances among the supplemental lighting treatments are resulted from variations in CO2 utilization. The enhanced blue light fraction in the W/R/B and W/B could better stimulate stomatal opening and promote photosynthetic electron transport activity, thus better improving photosynthetic rate. Compared with the inner canopy treatment, the supplemental lighting from the underneath canopy could better enhance the carbon dioxide assimilation efficiency and excessive energy dissipation, leading to an improved photosynthetic performance. Stomatal morphology was highly correlated to leaf photosynthesis and plant development, and should thus be an important determinant for the photosynthesis and the growth of greenhouse tomatoes. PMID:28018376

Electrical signaling, stomatal conductance, ABA and Ethylene content in avocado trees in response to root hypoxia

PubMed Central

Gurovich, Luis; Schaffer, Bruce; García, Nicolás; Iturriaga, Rodrigo

2009-01-01

Avocado (Persea americana Mill.) trees are among the most sensitive of fruit tree species to root hypoxia as a result of flooded or poorly drained soil. Similar to drought stress, an early physiological response to root hypoxia in avocado is a reduction of stomatal conductance. It has been previously determined in avocado trees that an extracellular electrical signal between the base of stem and leaves is produced and related to reductions in stomatal conductance in response to drought stress. The current study was designed to determine if changes in the extracellular electrical potential between the base of the stem and leaves in avocado trees could also be detected in response to short-term (min) or long-term (days) root hypoxia, and if these signals could be related to stomatal conductance (gs), root and leaf ABA and ACC concentrations, ethylene emission from leaves and leaf abscission. In contrast to previous observations for drought-stressed trees, short-term or long-term root hypoxia did not stimulate an electrical potential difference between the base of the stem and leaves. Short-term hypoxia did not result in a significant decrease in gs compared with plants in the control treatment, and no differences in ABA concentration were found between plants subjected to hypoxia and control plants. Long-term hypoxia in the root zone resulted in a significant decrease in gs, increased leaf ethylene and increased leaf abscission. The results indicate that for avocado trees exposed to root hypoxia, electrical signals do not appear to be the primary root-to-shoot communication mechanism involved in signaling for stomatal closure as a result of hypoxia in the root zone. PMID:19649181

ABI-like transcription factor gene TaABL1 from wheat improves multiple abiotic stress tolerances in transgenic plants.

PubMed

Xu, Dong-Bei; Gao, Shi-Qing; Ma, You-Zhi; Xu, Zhao-Shi; Zhao, Chang-Ping; Tang, Yi-Miao; Li, Xue-Yin; Li, Lian-Cheng; Chen, Yao-Feng; Chen, Ming

2014-12-01

The phytohormone abscisic acid (ABA) plays crucial roles in adaptive responses of plants to abiotic stresses. ABA-responsive element binding proteins (AREBs) are basic leucine zipper transcription factors that regulate the expression of downstream genes containing ABA-responsive elements (ABREs) in promoter regions. A novel ABI-like (ABA-insensitive) transcription factor gene, named TaABL1, containing a conserved basic leucine zipper (bZIP) domain was cloned from wheat. Southern blotting showed that three copies were present in the wheat genome. Phylogenetic analyses indicated that TaABL1 belonged to the AREB subfamily of the bZIP transcription factor family and was most closely related to ZmABI5 in maize and OsAREB2 in rice. Expression of TaABL1 was highly induced in wheat roots, stems, and leaves by ABA, drought, high salt, and low temperature stresses. TaABL1 was localized inside the nuclei of transformed wheat mesophyll protoplast. Overexpression of TaABL1 enhanced responses of transgenic plants to ABA and hastened stomatal closure under stress, thereby improving tolerance to multiple abiotic stresses. Furthermore, overexpression of TaABL1 upregulated or downregulated the expression of some stress-related genes controlling stomatal closure in transgenic plants under ABA and drought stress conditions, suggesting that TaABL1 might be a valuable genetic resource for transgenic molecular breeding.

Is desiccation tolerance and avoidance reflected in xylem and phloem anatomy of two co-existing arid-zone coniferous trees?: Xylem and Phloem Anatomy

DOE PAGES

Sevanto, Sanna Annika; Ryan, Max; Turin Dickman, L.; ...

2018-03-22

Plants close their stomata during drought to avoid excessive water loss, but species differ in respect to the drought severity at which stomata close. The stomatal closure point is related to xylem anatomy and vulnerability to embolism, but it also has implications for phloem transport, and possibly phloem anatomy to allow sugar transport at low water potentials. Desiccation tolerant plants that close their stomata at severe drought should have smaller xylem conduits and/or fewer and smaller inter-conduit pits to reduce vulnerability to embolism, but more phloem tissue and larger phloem conduits compared to plants that avoid desiccation. These anatomical differencesmore » could be expected to increase in response to long-term reduction in precipitation. To test these hypotheses we used tridimensional synchroton X-ray microtomograph and light microscope imaging of combined xylem and phloem tissues of two coniferous species: one-seed juniper (Juniperus monosperma) and piñon pine (Pinus edulis) subjected to precipitation manipulation treatments. These species show different xylem vulnerability to embolism, contrasting desiccation tolerance, and stomatal closure points. Our results support the hypothesis that desiccation tolerant plants require higher phloem transport capacity than desiccation avoiding plants, but this can be gained through various anatomical adaptations in addition to changing conduit or tissue size.« less

Is desiccation tolerance and avoidance reflected in xylem and phloem anatomy of two co-existing arid-zone coniferous trees?: Xylem and Phloem Anatomy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sevanto, Sanna Annika; Ryan, Max; Turin Dickman, L.

Plants close their stomata during drought to avoid excessive water loss, but species differ in respect to the drought severity at which stomata close. The stomatal closure point is related to xylem anatomy and vulnerability to embolism, but it also has implications for phloem transport, and possibly phloem anatomy to allow sugar transport at low water potentials. Desiccation tolerant plants that close their stomata at severe drought should have smaller xylem conduits and/or fewer and smaller inter-conduit pits to reduce vulnerability to embolism, but more phloem tissue and larger phloem conduits compared to plants that avoid desiccation. These anatomical differencesmore » could be expected to increase in response to long-term reduction in precipitation. To test these hypotheses we used tridimensional synchroton X-ray microtomograph and light microscope imaging of combined xylem and phloem tissues of two coniferous species: one-seed juniper (Juniperus monosperma) and piñon pine (Pinus edulis) subjected to precipitation manipulation treatments. These species show different xylem vulnerability to embolism, contrasting desiccation tolerance, and stomatal closure points. Our results support the hypothesis that desiccation tolerant plants require higher phloem transport capacity than desiccation avoiding plants, but this can be gained through various anatomical adaptations in addition to changing conduit or tissue size.« less

Gamma-aminobutyric acid depletion affects stomata closure and drought tolerance of Arabidopsis thaliana.

PubMed

Mekonnen, Dereje Worku; Flügge, Ulf-Ingo; Ludewig, Frank

2016-04-01

A rapid accumulation of γ-aminobutyric acid (GABA) during biotic and abiotic stresses is well documented. However, the specificity of the response and the primary role of GABA under such stress conditions are hardly understood. To address these questions, we investigated the response of the GABA-depleted gad1/2 mutant to drought stress. GABA is primarily synthesized from the decarboxylation of glutamate by glutamate decarboxylase (GAD) which exists in five copies in the genome of Arabidopsis thaliana. However, only GAD1 and GAD2 are abundantly expressed, and knockout of these two copies dramatically reduced the GABA content. Phenotypic analysis revealed a reduced shoot growth of the gad1/2 mutant. Furthermore, the gad1/2 mutant was wilted earlier than the wild type following a prolonged drought stress treatment. The early-wilting phenotype was due to an increase in stomata aperture and a defect in stomata closure. The increase in stomata aperture contributed to higher stomatal conductance. The drought oversensitive phenotype of the gad1/2 mutant was reversed by functional complementation that increases GABA level in leaves. The functionally complemented gad1/2 x pop2 triple mutant contained more GABA than the wild type. Our findings suggest that GABA accumulation during drought is a stress-specific response and its accumulation induces the regulation of stomatal opening thereby prevents loss of water. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

The effect of vapour pressure deficit on stomatal conductance, sap pH and leaf-specific hydraulic conductance in Eucalyptus globulus clones grown under two watering regimes

PubMed Central

Hernandez, Maria Jose; Montes, Fernando; Ruiz, Federico; Lopez, Gustavo; Pita, Pilar

2016-01-01

Background and Aims Stomatal conductance has long been considered of key interest in the study of plant adaptation to water stress. The expected increase in extreme meteorological events under a climate change scenario may compromise survival in Eucalyptus globulus plantations established in south-western Spain. We investigated to what extent changes in stomatal conductance in response to high vapour pressure deficits and water shortage are mediated by hydraulic and chemical signals in greenhouse-grown E. globulus clones. Methods Rooted cuttings were grown in pots and submitted to two watering regimes. Stomatal conductance, shoot water potential, sap pH and hydraulic conductance were measured consecutively in each plant over 4 weeks under vapour pressure deficits ranging 0·42 to 2·25 kPa. Evapotranspiration, growth in leaf area and shoot biomass were also determined. Key Results There was a significant effect of both clone and watering regime in stomatal conductance and leaf-specific hydraulic conductance, but not in sap pH. Sap pH decreased as water potential and stomatal conductance decreased under increasing vapour pressure deficit. There was no significant relationship between stomatal conductance and leaf-specific hydraulic conductance. Stomata closure precluded shoot water potential from falling below −1·8 MPa. The percentage loss of hydraulic conductance ranged from 40 to 85 %. The highest and lowest leaf-specific hydraulic conductances were measured in clones from the same half-sib families. Water shortage reduced growth and evapotranspiration, decreases in evapotranspiration ranging from 14 to 32 % in the five clones tested. Conclusions Changes in sap pH seemed to be a response to changes in atmospheric conditions rather than soil water in the species. Stomata closed after a considerable amount of hydraulic conductance was lost, although intraspecific differences in leaf-specific hydraulic conductance suggest the possibility of selection for improved productivity under water-limiting conditions combined with high temperatures in the early stages of growth. PMID:27052343

The effect of vapour pressure deficit on stomatal conductance, sap pH and leaf-specific hydraulic conductance in Eucalyptus globulus clones grown under two watering regimes.

PubMed

Hernandez, Maria Jose; Montes, Fernando; Ruiz, Federico; Lopez, Gustavo; Pita, Pilar

2016-05-01

Stomatal conductance has long been considered of key interest in the study of plant adaptation to water stress. The expected increase in extreme meteorological events under a climate change scenario may compromise survival in Eucalyptus globulus plantations established in south-western Spain. We investigated to what extent changes in stomatal conductance in response to high vapour pressure deficits and water shortage are mediated by hydraulic and chemical signals in greenhouse-grown E. globulus clones. Rooted cuttings were grown in pots and submitted to two watering regimes. Stomatal conductance, shoot water potential, sap pH and hydraulic conductance were measured consecutively in each plant over 4 weeks under vapour pressure deficits ranging 0·42 to 2·25 kPa. Evapotranspiration, growth in leaf area and shoot biomass were also determined. There was a significant effect of both clone and watering regime in stomatal conductance and leaf-specific hydraulic conductance, but not in sap pH. Sap pH decreased as water potential and stomatal conductance decreased under increasing vapour pressure deficit. There was no significant relationship between stomatal conductance and leaf-specific hydraulic conductance. Stomata closure precluded shoot water potential from falling below -1·8 MPa. The percentage loss of hydraulic conductance ranged from 40 to 85 %. The highest and lowest leaf-specific hydraulic conductances were measured in clones from the same half-sib families. Water shortage reduced growth and evapotranspiration, decreases in evapotranspiration ranging from 14 to 32 % in the five clones tested. Changes in sap pH seemed to be a response to changes in atmospheric conditions rather than soil water in the species. Stomata closed after a considerable amount of hydraulic conductance was lost, although intraspecific differences in leaf-specific hydraulic conductance suggest the possibility of selection for improved productivity under water-limiting conditions combined with high temperatures in the early stages of growth. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The grapevine guard cell-related VvMYB60 transcription factor is involved in the regulation of stomatal activity and is differentially expressed in response to ABA and osmotic stress

PubMed Central

2011-01-01

Background Under drought, plants accumulate the signaling hormone abscisic acid (ABA), which induces the rapid closure of stomatal pores to prevent water loss. This event is trigged by a series of signals produced inside guard cells which finally reduce their turgor. Many of these events are tightly regulated at the transcriptional level, including the control exerted by MYB proteins. In a previous study, while identifying the grapevine R2R3 MYB family, two closely related genes, VvMYB30 and VvMYB60 were found with high similarity to AtMYB60, an Arabidopsis guard cell-related drought responsive gene. Results Promoter-GUS transcriptional fusion assays showed that expression of VvMYB60 was restricted to stomatal guard cells and was attenuated in response to ABA. Unlike VvMYB30, VvMYB60 was able to complement the loss-of-function atmyb60-1 mutant, indicating that VvMYB60 is the only true ortholog of AtMYB60 in the grape genome. In addition, VvMYB60 was differentially regulated during development of grape organs and in response to ABA and drought-related stress conditions. Conclusions These results show that VvMYB60 modulates physiological responses in guard cells, leading to the possibility of engineering stomatal conductance in grapevine, reducing water loss and helping this species to tolerate drought under extreme climatic conditions. PMID:22018045

Native root xylem embolism and stomatal closure in stands of Douglas-fir and ponderosa pine: mitigation by hydraulic redistribution.

PubMed

Domec, J-C; Warren, J M; Meinzer, F C; Brooks, J R; Coulombe, R

2004-09-01

Hydraulic redistribution (HR), the passive movement of water via roots from moist to drier portions of the soil, occurs in many ecosystems, influencing both plant and ecosystem-water use. We examined the effects of HR on root hydraulic functioning during drought in young and old-growth Douglas-fir [ Pseudotsuga menziesii (Mirb.) Franco] and ponderosa pine ( Pinus ponderosa Dougl. Ex Laws) trees growing in four sites. During the 2002 growing season, in situ xylem embolism, water deficit and xylem vulnerability to embolism were measured on medium roots (2-4-mm diameter) collected at 20-30 cm depth. Soil water content and water potentials were monitored concurrently to determine the extent of HR. Additionally, the water potential and stomatal conductance ( g(s)) of upper canopy leaves were measured throughout the growing season. In the site with young Douglas-fir trees, root embolism increased from 20 to 55 percent loss of conductivity (PLC) as the dry season progressed. In young ponderosa pine, root embolism increased from 45 to 75 PLC. In contrast, roots of old-growth Douglas-fir and ponderosa pine trees never experienced more than 30 and 40 PLC, respectively. HR kept soil water potential at 20-30 cm depth above -0.5 MPa in the old-growth Douglas-fir site and -1.8 MPa in the old-growth ponderosa pine site, which significantly reduced loss of shallow root function. In the young ponderosa pine stand, where little HR occurred, the water potential in the upper soil layers fell to about -2.8 MPa, which severely impaired root functioning and limited recovery when the fall rains returned. In both species, daily maximum g(s) decreased linearly with increasing root PLC, suggesting that root xylem embolism acted in concert with stomata to limit water loss, thereby maintaining minimum leaf water potential above critical values. HR appears to be an important mechanism for maintaining shallow root function during drought and preventing total stomatal closure.

Water-Deficit Tolerance in Sweet Potato [Ipomoea batatas (L.) Lam.] by Foliar Application of Paclobutrazol: Role of Soluble Sugar and Free Proline.

PubMed

Yooyongwech, Suravoot; Samphumphuang, Thapanee; Tisarum, Rujira; Theerawitaya, Cattarin; Cha-Um, Suriyan

2017-01-01

The objective of this study was to elevate water deficit tolerance by improving soluble sugar and free proline accumulation, photosynthetic pigment stabilization, photosynthetic abilities, growth performance and storage root yield in sweet potato cv. 'Tainung 57' using a foliar application of paclobutrazol (PBZ). The experiment followed a Completely Randomized Block Design with four concentrations of PBZ: 0 (control), 17, 34, and 51 μM before exposure to 47.5% (well irrigation), 32.3% (mild water deficit) or 17.5% (severe water deficit) soil water content. A sweet potato cultivar, 'Japanese Yellow', with water deficit tolerance attributes was the positive check in this study. Total soluble sugar content (sucrose, glucose, and fructose) increased by 3.96-folds in 'Tainung 57' plants treated with 34 μM PBZ grown under 32.3% soil water content (SWC) compared to the untreated plants, adjusting osmotic potential in the leaves and controlling stomatal closure (represented by stomatal conductance and transpiration rate). In addition, under the same treatment, free proline content (2.15 μmol g -1 FW) increased by 3.84-folds when exposed to 17.5% SWC. PBZ had an improved effect on leaf size, vine length, photosynthetic pigment stability, chlorophyll fluorescence, and net photosynthetic rate; hence, delaying wilting symptoms and maintaining storage root yield (26.93 g plant -1 ) at the harvesting stage. A positive relationship between photon yield of PSII (Φ PSII ) and net photosynthetic rate was demonstrated ( r 2 = 0.73). The study concludes that soluble sugar and free proline enrichment in PBZ-pretreated plants may play a critical role as major osmoprotectant to control leaf osmotic potential and stomatal closure when plants were subjected to low soil water content, therefore, maintaining the physiological and morphological characters as well as storage root yield.

Water-Deficit Tolerance in Sweet Potato [Ipomoea batatas (L.) Lam.] by Foliar Application of Paclobutrazol: Role of Soluble Sugar and Free Proline

PubMed Central

Yooyongwech, Suravoot; Samphumphuang, Thapanee; Tisarum, Rujira; Theerawitaya, Cattarin; Cha-um, Suriyan

2017-01-01

The objective of this study was to elevate water deficit tolerance by improving soluble sugar and free proline accumulation, photosynthetic pigment stabilization, photosynthetic abilities, growth performance and storage root yield in sweet potato cv. ‘Tainung 57’ using a foliar application of paclobutrazol (PBZ). The experiment followed a Completely Randomized Block Design with four concentrations of PBZ: 0 (control), 17, 34, and 51 μM before exposure to 47.5% (well irrigation), 32.3% (mild water deficit) or 17.5% (severe water deficit) soil water content. A sweet potato cultivar, ‘Japanese Yellow’, with water deficit tolerance attributes was the positive check in this study. Total soluble sugar content (sucrose, glucose, and fructose) increased by 3.96-folds in ‘Tainung 57’ plants treated with 34 μM PBZ grown under 32.3% soil water content (SWC) compared to the untreated plants, adjusting osmotic potential in the leaves and controlling stomatal closure (represented by stomatal conductance and transpiration rate). In addition, under the same treatment, free proline content (2.15 μmol g-1 FW) increased by 3.84-folds when exposed to 17.5% SWC. PBZ had an improved effect on leaf size, vine length, photosynthetic pigment stability, chlorophyll fluorescence, and net photosynthetic rate; hence, delaying wilting symptoms and maintaining storage root yield (26.93 g plant-1) at the harvesting stage. A positive relationship between photon yield of PSII (ΦPSII) and net photosynthetic rate was demonstrated (r2 = 0.73). The study concludes that soluble sugar and free proline enrichment in PBZ-pretreated plants may play a critical role as major osmoprotectant to control leaf osmotic potential and stomatal closure when plants were subjected to low soil water content, therefore, maintaining the physiological and morphological characters as well as storage root yield. PMID:28848596

Metalloproteinase Expression is Associated with Traumatic Wound Failure

DTIC Science & Technology

2010-04-01

Traumatic amputation- no.(%) 15 Size of wound (cm3 )* Associated vascular injury- no.(%) 7 Wound closure method no.(%) Suture 29 Skin graft 9 Number...definitive closure or coverage with skin graft . Im- paired wound healing included delayed wound closure or wound dehiscence after closure or coverage...closure time period of 10 d. Dehiscence was defined as spontaneous partial or com- plete wound disruption after primary closure or > 90% skin graft loss

Pre-dawn stomatal opening does not substantially enhance early-morning photosynthesis in Helianthus annuus.

PubMed

Auchincloss, Lisa; Easlon, Hsien M; Levine, Diedre; Donovan, Lisa; Richards, James H

2014-06-01

Most C3 plant species have partially open stomata during the night especially in the 3-5 h before dawn. This pre-dawn stomatal opening has been hypothesized to enhance early-morning photosynthesis (A) by reducing diffusion limitations to CO2 at dawn. We tested this hypothesis in cultivated Helianthus annuus using whole-shoot gas exchange, leaf level gas exchange and modelling approaches. One hour pre-dawn low-humidity treatments were used to reduce pre-dawn stomatal conductance (g). At the whole-shoot level, a difference of pre-dawn g (0.40 versus 0.17 mol m(-2) s(-1)) did not significantly affect A during the first hour after dawn. Shorter term effects were investigated with leaf level gas exchange measurements and a difference of pre-dawn g (0.10 versus 0.04 mol m(-2) s(-1)) affected g and A for only 5 min after dawn. The potential effects of a wider range of stomatal apertures were explored with an empirical model of the relationship between A and intercellular CO2 concentration during the half-hour after dawn. Modelling results demonstrated that even extremely low pre-dawn stomatal conductance values have only a minimal effect on early-morning A for a few minutes after dawn. Thus, we found no evidence that pre-dawn stomatal opening enhances A.

Fenestrated Transcatheter ASD Closure in Adults with Diastolic Dysfunction and/or Pulmonary Hypertension: Case Series and Review of the Literature.

PubMed

Abdelkarim, Ayman; Levi, Daniel S; Tran, Bao; Ghobrial, Joanna; Aboulhosn, Jamil

2016-12-01

This study aims to evaluate the safety and efficacy of transcatheter fenestrated ASD closure and to summarize the literature regarding the published techniques and outcomes of transcatheter partial ASD closure. Patients with left ventricular diastolic dysfunction (LVDD) or right ventricular (RV) dysfunction and/or pulmonary hypertension (PHT) may suffer untoward consequences of complete closure of an ostium secundum atrial septal defect (ASD). Therefore, for patients that fall under these categories we suggest partial occlusion of the defect, which may be better tolerated than complete defect closure. After obtaining IRB approval, a search for patients that have undergone percutaneous ASD closure was performed in the Ahmanson/UCLA Adult Congenital Heart Disease Center database to identify which patients received a fenestrated ASD closure device. Eight consecutive patients ranging between 22 and 83 years of age (mean 48 years) with PHT and/or LVDD or RV dysfunction who underwent fenestrated transcatheter ASD closure at UCLA were identified. None of the subjects experienced complications related to the procedure. Postprocedure clinical evaluation showed improvement in symptoms and exercise capacity. Available follow-up transthoracic echocardiography data (mean 4 months, range 0-20 months) demonstrated patent fenestrations in four of eight patients. None of the patients had thromboembolic or infectious complications and there were no device migrations, erosions or embolizations. Partial ASD occlusion in patients with diastolic dysfunction or RV dysfunction and/or PHT is safe and may be better tolerated than complete ASD closure in selected patients. © 2016 Wiley Periodicals, Inc.

78 FR 11097 - Artificial Island Anchorage No. 2 Partial Closure, Delaware River; Salem, NJ

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-15

... 1625-AA00 Artificial Island Anchorage No. 2 Partial Closure, Delaware River; Salem, NJ AGENCY: Coast... safety zone around the southern portion of Anchorage 2 (Artificial Island Anchorage) below position 39... will cross the closed portion of the anchorage. This regulation is necessary to provide for the safety...

Partial growth plate closure: apex view on bone scan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howman-Giles, R.; Trochei, M.; Yeates, K.

1985-01-01

A new technique of using /sup 99m/Tc bone scan to assess partial closure of the growth plate is described. The site and degree of osseous fusion can be obtained by using the apex view. The technique has the potential of assessing serially the growth of a plate before and after surgery.

Escherichia coli O157:H7 induces stronger plant immunity than Salmonella enterica Typhimurium SL1344.

PubMed

Roy, Debanjana; Panchal, Shweta; Rosa, Bruce A; Melotto, Maeli

2013-04-01

Consumption of fresh produce contaminated with bacterial human pathogens has resulted in various, sometimes deadly, disease outbreaks. In this study, we assessed plant defense responses induced by the fully pathogenic bacteria Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium SL1344 in both Arabidopsis thaliana and lettuce (Lactuca sativa). Unlike SL1344, O157:H7 induced strong plant immunity at both pre-invasion and post-invasion steps of infection. For instance, O157:H7 triggered stomatal closure even under high relative humidity, an environmental condition that generally weakens plant defenses against bacteria in the field and laboratory conditions. SL1344 instead induced a transient stomatal immunity. We also observed that PR1 gene expression was significantly higher in Arabidopsis leaves infected with O157:H7 compared with SL1344. These results suggest that plants may recognize and respond to some human pathogens more effectively than others. Furthermore, stomatal immunity can diminish the penetration of human pathogens through the leaf epidermis, resulting in low bacterial titers in the plant apoplast and suggesting that additional control measures can be employed to prevent food contamination. The understanding of how plant responses can diminish bacterial contamination is paramount in preventing outbreaks and improving the safety of food supplies.

Rumor has it...: relay communication of stress cues in plants.

PubMed

Falik, Omer; Mordoch, Yonat; Quansah, Lydia; Fait, Aaron; Novoplansky, Ariel

2011-01-01

Recent evidence demonstrates that plants are able not only to perceive and adaptively respond to external information but also to anticipate forthcoming hazards and stresses. Here, we tested the hypothesis that unstressed plants are able to respond to stress cues emitted from their abiotically-stressed neighbors and in turn induce stress responses in additional unstressed plants located further away from the stressed plants. Pisum sativum plants were subjected to drought while neighboring rows of five unstressed plants on both sides, with which they could exchange different cue combinations. On one side, the stressed plant and its unstressed neighbors did not share their rooting volumes (UNSHARED) and thus were limited to shoot communication. On its other side, the stressed plant shared one of its rooting volumes with its nearest unstressed neighbor and all plants shared their rooting volumes with their immediate neighbors (SHARED), allowing both root and shoot communication. Fifteen minutes following drought induction, significant stomatal closure was observed in both the stressed plants and their nearest unstressed SHARED neighbors, and within one hour, all SHARED neighbors closed their stomata. Stomatal closure was not observed in the UNSHARED neighbors. The results demonstrate that unstressed plants are able to perceive and respond to stress cues emitted by the roots of their drought-stressed neighbors and, via 'relay cuing', elicit stress responses in further unstressed plants. Further work is underway to study the underlying mechanisms of this new mode of plant communication and its possible adaptive implications for the anticipation of forthcoming abiotic stresses by plants.

Conifer species adapt to low-rainfall climates by following one of two divergent pathways.

PubMed

Brodribb, Timothy J; McAdam, Scott A M; Jordan, Gregory J; Martins, Samuel C V

2014-10-07

Water stress is one of the primary selective forces in plant evolution. There are characters often cited as adaptations to water stress, but links between the function of these traits and adaptation to drying climates are tenuous. Here we combine distributional, climatic, and physiological evidence from 42 species of conifers to show that the evolution of drought resistance follows two distinct pathways, both involving the coordinated evolution of tissues regulating water supply (xylem) and water loss (stomatal pores) in leaves. Only species with very efficient stomatal closure, and hence low minimum rates of water loss, inhabit dry habitats, but species diverged in their apparent mechanism for maintaining closed stomata during drought. An ancestral mechanism found in Pinaceae and Araucariaceae species relies on high levels of the hormone abscisic acid (ABA) to close stomata during water stress. A second mechanism, found in the majority of Cupressaceae species, uses leaf desiccation rather than high ABA levels to close stomata during sustained water stress. Species in the latter group were characterized by xylem tissues with extreme resistance to embolism but low levels of foliar ABA after 30 d without water. The combination of low levels of ABA under stress with cavitation-resistant xylem enables these species to prolong stomatal opening during drought, potentially extending their photosynthetic activity between rainfall events. Our data demonstrate a surprising simplicity in the way conifers evolved to cope with water shortage, indicating a critical interaction between xylem and stomatal tissues during the process of evolution to dry climates.

Responses of sap flow, leaf gas exchange and growth of hybrid aspen to elevated atmospheric humidity under field conditions

PubMed Central

Niglas, Aigar; Kupper, Priit; Tullus, Arvo; Sellin, Arne

2014-01-01

An increase in average air temperature and frequency of rain events is predicted for higher latitudes by the end of the 21st century, accompanied by a probable rise in air humidity. We currently lack knowledge on how forest trees acclimate to rising air humidity in temperate climates. We analysed the leaf gas exchange, sap flow and growth characteristics of hybrid aspen (Populus tremula × P. tremuloides) trees growing at ambient and artificially elevated air humidity in an experimental forest plantation situated in the hemiboreal vegetation zone. Humidification manipulation did not affect the photosynthetic capacity of plants, but did affect stomatal responses: trees growing at elevated air humidity had higher stomatal conductance at saturating photosynthetically active radiation (gs sat) and lower intrinsic water-use efficiency (IWUE). Reduced stomatal limitation of photosynthesis in trees grown at elevated air humidity allowed slightly higher net photosynthesis and relative current-year height increments than in trees at ambient air humidity. Tree responses suggest a mitigating effect of higher air humidity on trees under mild water stress. At the same time, trees at higher air humidity demonstrated a reduced sensitivity of IWUE to factors inducing stomatal closure and a steeper decline in canopy conductance in response to water deficit, implying higher dehydration risk. Despite the mitigating impact of increased air humidity under moderate drought, a future rise in atmospheric humidity at high latitudes may be disadvantageous for trees during weather extremes and represents a potential threat in hemiboreal forest ecosystems. PMID:24887000

Responses to flooding of plant water relations and leaf gas exchange in tropical tolerant trees of a black-water wetland.

PubMed

Herrera, A

2013-01-01

This review summarizes the research on physiological responses to flooding of trees in the seasonal black-water wetland of the Mapire River in Venezuela. Inter-annual variability was found during 8 years of sampling, in spite of which a general picture emerged of increased stomatal conductance (gs) and photosynthetic rate (PN) during the flooded period to values as high as or higher than in plants in drained wet soil. Models explaining the initial inhibitory responses and the acclimation to flooding are proposed. In the inhibitory phase of flooding, hypoxia generated by flooding causes a decrease in root water absorption and stomatal closure. An increase with flooding in xylem water potential (ψ) suggests that flooding does not cause water deficit. The PN decreases due to changes in relative stomatal and non-stomatal limitations to photosynthesis; an increase in the latter is due to reduced chlorophyll and total soluble protein content. Total non-structural carbohydrates (TNC) accumulate in leaves but their content begins to decrease during the acclimatized phase at full flooding, coinciding with the resumption of high gs and PN. The reversal of the diminution in gs is associated, in some but not all species, to the growth of adventitious roots. The occurrence of morpho-anatomical and biochemical adaptations which improve oxygen supply would cause the acclimation, including increased water absorption by the roots, increased rubisco and chlorophyll contents and ultimately increased PN. Therefore, trees would perform as if flooding did not signify a stress to their physiology.

40 CFR 265.142 - Cost estimate for closure.

Code of Federal Regulations, 2010 CFR

2010-07-01

... must equal the cost of final closure at the point in the facility's active life when the extent and... at all times over the life of the facility. (3) The closure cost estimate may not incorporate any... facility at the time of partial or final closure. (4) The owner or operator may not incorporate a zero cost...

40 CFR 265.142 - Cost estimate for closure.

Code of Federal Regulations, 2011 CFR

2011-07-01

... must equal the cost of final closure at the point in the facility's active life when the extent and... at all times over the life of the facility. (3) The closure cost estimate may not incorporate any... facility at the time of partial or final closure. (4) The owner or operator may not incorporate a zero cost...

Partial Cavity Flows at High Reynolds Numbers

NASA Astrophysics Data System (ADS)

Makiharju, Simo; Elbing, Brian; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven

2009-11-01

Partial cavity flows created for friction drag reduction were examined on a large-scale. Partial cavities were investigated at Reynolds numbers up to 120 million, and stable cavities with frictional drag reduction of more than 95% were attained at optimal conditions. The model used was a 3 m wide and 12 m long flat plate with a plenum on the bottom. To create the partial cavity, air was injected at the base of an 18 cm backwards-facing step 2.1 m from the leading edge. The geometry at the cavity closure was varied for different flow speeds to optimize the closure of the cavity. Cavity gas flux, thickness, frictional loads, and cavity pressures were measured over a range of flow speeds and air injection fluxes. High-speed video was used extensively to investigate the unsteady three dimensional cavity closure, the overall cavity shape and oscillations.

Proposed Hydrodynamic Model Increases the Ability of Land-Surface Models to Capture Intra-Daily Dynamics of Transpiration and Canopy Structure Effects

NASA Astrophysics Data System (ADS)

Matheny, A. M.; Bohrer, G.; Mirfenderesgi, G.; Schafer, K. V.; Ivanov, V. Y.

2014-12-01

Hydraulic limitations are known to control transpiration in forest ecosystems when the soil is drying or when the vapor pressure deficit between the air and stomata is very large, but they can also impact stomatal apertures under conditions of adequate soil moisture and lower evaporative demand. We use the NACP dataset of latent heat flux measurements and model observations for multiple sites and models to demonstrate models' difficulties in capturing intra-daily hysteresis. We hypothesize that this is a result of un-resolved afternoon stomata closure due to hydrodynamic stresses. The current formulations for stomatal conductance and the empirical coupling between stomatal conductance and soil moisture used by these models does not resolve the hydrodynamic process of water movement from the soil to the leaves. This approach does not take advantage of advances in our understanding of water flow and storage in the trees, or of tree and canopy structure. A more thorough representation of the tree-hydrodynamic processes could potentially remedy this significant source of model error. In a forest plot at the University of Michigan Biological Station, we use measurements of sap flux and leaf water potential to demonstrate that trees of similar type - late successional deciduous trees - have very different hydrodynamic strategies that lead to differences in their temporal patterns of stomatal conductance and thus hysteretic cycles of transpiration. These differences will lead to large differences in conductance and water use based on the species composition of the forest. We also demonstrate that the size and shape of the tree branching system leads to differences in extent of hydrodynamic stress, which may change the forest respiration patterns as the forest grows and ages. We propose a framework to resolve tree hydrodynamics in global and regional models based on the Finite-Elements Tree-Crown Hydrodynamics model (FETCH) -a hydrodynamic model that can resolve the fast dynamics of stomatal conductance. FETCH simulates water flow through a tree as a system of porous media conduits and calculates the amount of hydraulic limitation to stomatal conductance, given the atmospheric and biological variables from the global model, and could replace the current empirical formulation for stomatal adjustment based on soil moisture.

Making C4 crops more water efficient under current and future climate: Tradeoffs between carbon gain and water loss

NASA Astrophysics Data System (ADS)

Srinivasan, V.; Pignon, C.

2017-12-01

C4 plants have a carbon concentrating mechanism that has evolved under historically low CO2 concentrations of around 200 ppm. However, increases in global CO2 concentrations in recent times (current CO2 concentrations are at 400 ppm and it is projected to be 550 ppm by mid-century) have diminished the relative advantage of C4 plants over C3 plants, which lack the expensive carbon concentrating machinery. Here we show by employing model simulations that under pre-historic CO2 concentrations, C4 plants are near optimal in their stomatal behavior and nitrogen partitioning between carbon concentrating machinery and carboxylation machinery, and they are significantly supra-optimal under current and future elevated CO2 concentrations. Model simulations performed at current CO2 concentrations of 400 ppm show that, under high light conditions, decreasing stomatal conductance by 20% results in a 15% increase in water use efficiency with negligible loss in photosynthesis. Under future elevated CO2 concentrations of 550 ppm, a 40% decrease in stomatal conductance produces a 35% increase in water use efficiency. Furthermore, stomatal closure is shown to be more effective in decreasing whole canopy transpiration compared to canopy top leaf transpiration, since shaded leaves are more supra-optimal than sunlit leaves. Model simulations for optimizing nitrogen distribution in C4 leaves show that under high light conditions, C4 plants over invest in carbon concentrating machinery and under invest in carboxylation machinery. A 20% redistribution in leaf nitrogen results in a 10% increase in leaf carbon assimilation without significant increases in transpiration under current CO2 concentrations of 400 ppm. Similarly, a 40% redistribution in leaf nitrogen results in a 15% increase in leaf carbon assimilation without significant increases in transpiration under future elevated CO2 concentrations of 550 ppm. Our model optimality simulations show that C4 leaves a supra optimal in their stomatal behavior and leaf nitrogen distribution and by decreasing stomatal conductance and redistributing nitrogen away from carbon concentrating mechanism and towards carboxylation machinery, we can significantly decrease transpiration and increase carbon assimilation thereby increasing water use efficiency.

Stomatal sensitivity to vapour pressure deficit relates to climate of origin in Eucalyptus species.

PubMed

Bourne, Aimee E; Haigh, Anthony M; Ellsworth, David S

2015-03-01

Selecting plantation species to balance water use and production requires accurate models for predicting how species will tolerate and respond to environmental conditions. Although interspecific variation in water use occurs, species-specific parameters are rarely incorporated into physiologically based models because often the appropriate species parameters are lacking. To determine the physiological control over water use in Eucalyptus, five stands of Eucalyptus species growing in a common garden were measured for sap flux rates and their stomatal response to vapour pressure deficit (D) was assessed. Maximal canopy conductance and whole-canopy stomatal sensitivity to D and reduced water availability were lower in species originating from more arid climates of origin than those from humid climates. Species from humid climates showed a larger decline in maximal sap flux density (JSmax) with reduced water availability, and a lower D at which stomatal closure occurred than species from more arid climates, implying larger sensitivity to water availability and D in these species. We observed significant (P < 0.05) correlations of species climate of origin with mean vessel diameter (R(2) = 0.90), stomatal sensitivity to D (R(2) = 0.83) and the size of the decline in JSmax to restricted water availability (R(2) = 0.94). Thus aridity of climate of origin appears to have a selective role in constraining water-use response among the five Eucalyptus plantation species. These relationships emphasize that within this congeneric group of species, climate aridity constrains water use. These relationships have implications for species choices for tree plantation success against drought-induced losses and the ability to manage Eucalyptus plantations against projected changes in water availability and evaporation in the future. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

RCRA, superfund and EPCRA hotline training module. Introduction to: Closure/post-closure (40 cfr parts 264/265, subpart g) updated July 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-07-01

The module explains the difference between closure and post-closure. It lists the types of facilities that are subject to closure/post-closures and defines the difference between partial and final closure. It specifies who submits a closure plan and when a closure plan must be submitted, lists the steps in the process, and states the time frame for submittal. It identifies when and how a closure must be amended. It explains the time frame for notification of closure and the deadlines for beginning and completing closure. It specifies which facilities need contingent post-closure plans and lists and the elements of post-closure andmore » cites the requirements. It specifies the conditions and timing for amending a post-closure plan and states who must certify closure/post-closure.« less

40 CFR 264.117 - Post-closure care and use of property.

Code of Federal Regulations, 2010 CFR

2010-07-01

.... 264.117 Section 264.117 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID... for each hazardous waste management unit subject to the requirements of §§ 264.117 through 264.120... preceding partial closure of a hazardous waste management unit subject to post-closure care requirements or...

40 CFR 265.143 - Financial assurance for closure.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., except as provided in § 265.143(f), divided by the number of years in the pay-in period. (ii) Subsequent... bills for partial or final closure activities, the Regional Administrator will instruct the trustee to... facility over its remaining operating life. Within 60 days after receiving bills for closure activities...

40 CFR 264.143 - Financial assurance for closure.

Code of Federal Regulations, 2010 CFR

2010-07-01

... in § 264.143(g), divided by the number of years in the pay-in period. Subsequent payments must be... for partial or final closure activities, the Regional Administrator will instruct the trustee to make... operating life. Within 60 days after receiving bills for closure activities, the Regional Administrator will...

Alterations in Rubisco activity and in stomatal behavior induce a daily rhythm in photosynthesis of aerial leaves in the amphibious-plant Nuphar lutea.

PubMed

Snir, Ainit; Gurevitz, Michael; Marcus, Yehouda

2006-12-01

Nuphar lutea is an amphibious plant with submerged and aerial foliage, which raises the question how do both leaf types perform photosynthetically in two different environments. We found that the aerial leaves function like terrestrial sun-leaves in that their photosynthetic capability was high and saturated under high irradiance (ca. 1,500 mumol photons m(-2) s(-1)). We show that stomatal opening and Rubisco activity in these leaves co-limited photosynthesis at saturating irradiance fluctuating in a daily rhythm. In the morning, sunlight stimulated stomatal opening, Rubisco synthesis, and the neutralization of a night-accumulated Rubisco inhibitor. Consequently, the light-saturated quantum efficiency and rate of photosynthesis increased 10-fold by midday. During the afternoon, gradual closure of the stomata and a decrease in Rubisco content reduced the light-saturated photosynthetic rate. However, at limited irradiance, stomatal behavior and Rubisco content had only a marginal effect on the photosynthetic rate, which did not change during the day. In contrast to the aerial leaves, the photosynthesis rate of the submerged leaves, adapted to a shaded environment, was saturated under lower irradiance. The light-saturated quantum efficiency of these leaves was much lower and did not change during the day. Due to their low photosynthetic affinity for CO(2) (35 muM) and inability to utilize other inorganic carbon species, their photosynthetic rate at air-equilibrated water was CO(2)-limited. These results reveal differences in the photosynthetic performance of the two types of Nuphar leaves and unravel how photosynthetic daily rhythm in the aerial leaves is controlled.

Lower leaf gas-exchange and higher photorespiration of treated wastewater irrigated Citrus trees is modulated by soil type and climate.

PubMed

Paudel, Indira; Shaviv, Avi; Bernstein, Nirit; Heuer, Bruria; Shapira, Or; Lukyanov, Victor; Bar-Tal, Asher; Rotbart, Nativ; Ephrath, Jhonathan; Cohen, Shabtai

2016-04-01

Water quality, soil and climate can interact to limit photosynthesis and to increase photooxidative damage in sensitive plants. This research compared diffusive and non-diffusive limitations to photosynthesis as well as photorespiration of leaves of grapefruit trees in heavy clay and sandy soils having a previous history of treated wastewater (TWW) irrigation for >10 years, with different water qualities [fresh water (FW) vs TWW and sodium amended treated wastewater (TWW + Na)] in two arid climates (summer vs winter) and in orchard and lysimeter experiments. TWW irrigation increased salts (Na(+) and Cl(-) ), membrane leakage, proline and soluble sugar content, and decreased osmotic potentials in leaves of all experiments. Reduced leaf growth and higher stomatal and non-stomatal (i.e. mesophyll) limitations were found in summer and on clay soil for TWW and TWW + Na treatments in comparison to winter, sandy soil and FW irrigation, respectively. Stomatal closure, lower chlorophyll content and altered Rubisco activity are probable causes of higher limitations. On the other hand, non-photochemical quenching, an alternative energy dissipation pathway, was only influenced by water quality, independent of soil type and season. Furthermore, light and CO2 response curves were investigated for other possible causes of higher non-stomatal limitation. A higher proportion of non-cyclic electrons were directed to the O2 dependent pathway, and a higher proportion of electrons were diverted to photorespiration in summer than in winter. In conclusion, both diffusive and non-diffusive limitations contribute to the lower photosynthetic performance of leaves following TWW irrigation, and the response depends on soil type and environmental factors. © 2015 Scandinavian Plant Physiology Society.

Modeling analysis of the benefits of Crassulacean acid metabolism (CAM) for sustainable agriculture in arid regions

NASA Astrophysics Data System (ADS)

Bartlett, M. S.; Vico, G.; Porporato, A. M.

2012-12-01

In view of the pressing needs to sustainably manage water and soil resources, especially in arid and semi-arid regions, here we propose a new carbon assimilation model that couples a simple yet mechanistic description of Crassulacean acid metabolism (CAM) photosynthesis to the soil-plant-atmosphere continuum. The model captures the full coupling of the CAM photosynthetic pathway with fluctuations in environmental conditions (cycles of light availability and air humidity, changes in soil moisture as driven by plant transpiration and rainfall occurrence). As such, the model is capable of reproducing the different phases of CAM, including daytime stomatal closure and photosynthesis from malic acid, afternoon stomatal opening for direct carbon assimilation, and nighttime stomatal opening for CO2 uptake and malic acid synthesis. Thanks to its versatility, our model allows us to relate CAM productivity, for both obligate and facultative CAM plants, to various soil moisture conditions including hydroclimatic scenarios of rainfall frequency and intensity as well as different night-time conditions of temperature, wind speed, and humidity. Our analyses show the potential productive benefits of CAM cultivation in dryland environments as feedstock and possible biofuel source, in terms of sustainable water use and economic benefits. In particular, the model is used to explore conditions where CAM plant resiliency to water stress makes these plants a more sustainable alternative to C3 and C4 species for potential deficit irrigation.

The role of ecosystem-atmosphere interactions in simulated Amazonian precipitation decrease and forest dieback under global climate warming

NASA Astrophysics Data System (ADS)

Betts, R. A.; Cox, P. M.; Collins, M.; Harris, P. P.; Huntingford, C.; Jones, C. D.

A suite of simulations with the HadCM3LC coupled climate-carbon cycle model is used to examine the various forcings and feedbacks involved in the simulated precipitation decrease and forest dieback. Rising atmospheric CO2 is found to contribute 20% to the precipitation reduction through the physiological forcing of stomatal closure, with 80% of the reduction being seen when stomatal closure was excluded and only radiative forcing by CO2 was included. The forest dieback exerts two positive feedbacks on the precipitation reduction; a biogeophysical feedback through reduced forest cover suppressing local evaporative water recycling, and a biogeochemical feedback through the release of CO2 contributing to an accelerated global warming. The precipitation reduction is enhanced by 20% by the biogeophysical feedback, and 5% by the carbon cycle feedback from the forest dieback. This analysis helps to explain why the Amazonian precipitation reduction simulated by HadCM3LC is more extreme than that simulated in other GCMs; in the fully-coupled, climate-carbon cycle simulation, approximately half of the precipitation reduction in Amazonia is attributable to a combination of physiological forcing and biogeophysical and global carbon cycle feedbacks, which are generally not included in other GCM simulations of future climate change. The analysis also demonstrates the potential contribution of regional-scale climate and ecosystem change to uncertainties in global CO2 and climate change projections. Moreover, the importance of feedbacks suggests that a human-induced increase in forest vulnerability to climate change may have implications for regional and global scale climate sensitivity.

Improved simulation of poorly drained forests using Biome-BGC.

PubMed

Bond-Lamberty, Ben; Gower, Stith T; Ahl, Douglas E

2007-05-01

Forested wetlands and peatlands are important in boreal and terrestrial biogeochemical cycling, but most general-purpose forest process models are designed and parameterized for upland systems. We describe changes made to Biome-BGC, an ecophysiological process model, that improve its ability to simulate poorly drained forests. Model changes allowed for: (1) lateral water inflow from a surrounding watershed, and variable surface and subsurface drainage; (2) adverse effects of anoxic soil on decomposition and nutrient mineralization; (3) closure of leaf stomata in flooded soils; and (4) growth of nonvascular plants (i.e., bryophytes). Bryophytes were treated as ectohydric broadleaf evergreen plants with zero stomatal conductance, whose cuticular conductance to CO(2) was dependent on plant water content. Individual model changes were parameterized with published data, and ecosystem-level model performance was assessed by comparing simulated output to field data from the northern BOREAS site in Manitoba, Canada. The simulation of the poorly drained forest model exhibited reduced decomposition and vascular plant growth (-90%) compared with that of the well-drained forest model; the integrated bryophyte photosynthetic response accorded well with published data. Simulated net primary production, biomass and soil carbon accumulation broadly agreed with field measurements, although simulated net primary production was higher than observed data in well-drained stands. Simulated net primary production in the poorly drained forest was most sensitive to oxygen restriction on soil processes, and secondarily to stomatal closure in flooded conditions. The modified Biome-BGC remains unable to simulate true wetlands that are subject to prolonged flooding, because it does not track organic soil formation, water table changes, soil redox potential or anaerobic processes.

Elevated atmospheric CO2 negatively impacts photosynthesis through radiative forcing and physiology-mediated climate feedback

NASA Astrophysics Data System (ADS)

Zhu, Peng; Zhuang, Qianlai; Ciais, Philippe; Welp, Lisa; Li, Wenyu; Xin, Qinchuan

2017-02-01

Increasing atmospheric CO2 affects photosynthesis involving directly increasing leaf carboxylation rates, stomatal closure, and climatic effects. The direct effects are generally thought to be positive leading to increased photosynthesis, while its climatic effects can be regionally positive or negative. These effects are usually considered to be independent from each other, but they are in fact coupled through interactions between land surface exchanges of gases and heat and the physical climate system. In particular, stomatal closure reduces evapotranspiration and increases sensible heat emissions from ecosystems, leading to decreased atmospheric moisture and precipitation and local warming. We use a coupled earth system model to attribute the influence of the increase in CO2 on gross primary productivity (GPP) during the period of 1930-2011. In our model, CO2 radiative effects cause climate change that has only a negligible effect on global GPP (a reduction of 0.9 ± 2% during the last 80 years) because of opposite responses between tropical and northern biomes. On the other hand, CO2 physiological effects on GPP are both positive, by increased carboxylation rates and water use efficiency (7.1 ± 0.48% increase), and negative, by vegetation-climate feedback reducing precipitation, as a consequence of decreased transpiration and increased sensible heat in areas without water limitation (2.7 ± 1.76% reduction).When considering the coupled atmosphere-vegetation system, negative climate feedback on photosynthesis and plant growth due to the current level of CO2 opposes 29-38% of the gains from direct fertilization effects.

A Crack Closure Model and Its Application to Vibrothermography Nondestructive Evaluation

NASA Astrophysics Data System (ADS)

Schiefelbein, Bryan Edward

Vibrothermography nondestructive evaluation (NDE) is in the early stages of research and development, and there exists uncertainty in the fundamental mechanisms and processes by which heat generation occurs. Holland et al. have developed a set of tools which simulate and predict the outcome of a vibrothermography inspection by breaking the inspection into three distinct processes: vibrational excitation, heat generation, and thermal imaging. The stage of vibrothermography which is not well understood is the process by which vibrations are converted to heat at the crack surface. It has been shown that crack closure and closure state impact the resulting heat generation. Despite this, research into the link between partial crack closure and vibrothermography is limited. This work seeks to rectify this gap in knowledge by modeling the behavior of a partially closed crack in response to static external loading and a dynamic vibration. The residual strains left by the plastic wake during fatigue crack growth manifest themselves as contact stresses acting at the crack surface interface. In response to an applied load below the crack opening stress, the crack closure state will evolve, but the crack will remain partially closed. The crack closure model developed in this work is based in linear elastic fracture mechanics (LEFM) and describes the behavior of a partially closed crack in response to a tensile external load and non-uniform closure stress distribution. The model builds on work by Fleck to describe the effective length, crack opening displacement, and crack tip stress field for a partially closed crack. These quantities are solved for by first establishing an equilibrium condition which governs the effective or apparent length of the partially closed crack. The equilibrium condition states that, under any external or crack surface loading, the effective crack tip will be located where the effective stress intensity factor is zero. In LEFM, this is equivalent to saying that the effective crack tip is located where the stress singularity vanishes. If the closure stresses are unknown, the model provides an algorithm with which to solve for the distribution, given measurements of the effective crack length as a function of external load. Within literature, a number of heating mechanisms have been proposed as being dominant in vibrothermography. These include strain hysteresis, adhesion hysteresis, plastic flow, thermoelasticity, and sliding friction. Based on experimental observation and theory, this work eliminates strain hysteresis, thermoelasticity, and plastic flow as plausible heating mechanisms. This leaves friction and adhesion hysteresis as the only plausible mechanisms. Frictional heating is based on the classical Coulomb friction model, while adhesion hysteresis heating comes from irreversibility in surface adhesion. Adhesion hysteresis only satisfies the experimental observation that heating vanishes for high compressive loading if surface roughness and the instability of surface adhesion is considered. By understanding the fundamental behavior of a partially closed crack in response to non-uniform loading, and the link between crack surface motion and heat generation, we are one step closer to a fully predictive vibrothermography heat generation model. Future work is needed to extend the crack closure model to a two-dimensional semi-elliptical surface crack and better understand the distinction between frictional and adhesion heating.

Cleft closure and undersizing annuloplasty improve mitral repair in atrioventricular canal defects

PubMed Central

Padala, Muralidhar; Vasilyev, Nikolay V.; Owen, James W.; Jimenez, Jorge H.; Dasi, Lakshmi P.; del Nido, Pedro J.; Yoganathan, Ajit P.

2009-01-01

Objective Reoperation rates to correct left atrioventricular valve regurgitation after primary repair of atrioventricular canal defects remain relatively high. The causes of valvular regurgitation are likely multifactorial, and simple cleft closure is often insufficient to prevent recurrence. Methods To elucidate the mechanisms leading to regurgitation, we conducted hemodynamic studies using isolated native mitral valves. Anatomy of these valves was altered to mimic atrioventricular canal type valves and studied under pediatric hemodynamic conditions. The impact of subvalvular geometry, cleft closure, annular dilatation, and annular undersizing on regurgitation were investigated. Results Papillary muscle position did not have a significant effect on regurgitation. Cleft closure had a significant impact on valvular competence, with reduction in regurgitation volume with increased cleft closure. Regurgitation volume decreased from 12.5 ± 2.4 mL/beat for an open cleft to 4.9 ± 1.9 mL/beat for a partially closed cleft and to 1.4 ± 1.6 mL/beat when the cleft was completely closed. Annular dilatation had a significant impact on regurgitation even after cleft closure. A 40% increase in annular size increased regurgitation by 59% for a partially closed cleft and by 84% for a fully closed cleft. Reducing the annular size by 20% from the physiologic level decreased the regurgitation volume by 12% for a fully open cleft and by 58% for the partially closed cleft case. Conclusions Annular dilatation after primary repair has a potentially significant role in the recurrence of atrioventricular valve regurgitation. Reducing the annular size and restricting dilatation as an adjunct to cleft closure is a promising surgical approach in such valve anatomies. PMID:19026810

Oral mucosal lesions in denture wearers.

PubMed

Jainkittivong, Aree; Aneksuk, Vilaiwan; Langlais, Robert P

2010-03-01

To determine the prevalence of oral mucosal lesions (OMLs) and denture-related mucosal lesions (DMLs) in denture wearers and to co-relate the prevalence with age, gender, type of denture and any systemic conditions. Dental records of 380 denture wearers were retrospectively reviewed for OMLs and DMLs. We found 45% of the denture wearers had DMLs and 60.8% had OMLs not related to denture wearing. Although the prevalence of DMLs was higher in complete denture wearers than in partial denture wearers (49% vs. 42.2%), this difference was not significant. The most common DMLs were traumatic ulcer (19.5%) and denture-induced stomatitis (18.1%). When analysed by type, traumatic ulcer, denture hyperplasia, frictional keratosis and candidiasis were more common in complete denture wearers, whereas denture-induced stomatitis was more common in partial denture wearers. Frictional keratosis was more common in men than in women. The prevalence of OMLs not related to denture wearing was higher in complete denture wearers than in partial denture wearers, and the most common OML was fissured tongue (27.6%). No association between DMLs and systemic conditions or xerostomic drugs was noted. No differences in the prevalence of DMLs in association with denture type were found. The prevalence of OMLs not related to denture wearing was higher in complete denture wearers than in partial denture wearers. This difference was affected by age, and the data were similar to the findings observed in the elderly.

Comparison of infrared canopy temperature in a rubber plantation and tropical rain forest

NASA Astrophysics Data System (ADS)

Song, Qing-Hai; Deng, Yun; Zhang, Yi-Ping; Deng, Xiao-Bao; Lin, You-Xing; Zhou, Li-Guo; Fei, Xue-Hai; Sha, Li-Qing; Liu, Yun-Tong; Zhou, Wen-Jun; Gao, Jin-Bo

2017-10-01

Canopy temperature is a result of the canopy energy balance and is driven by climate conditions, plant architecture, and plant-controlled transpiration. Here, we evaluated canopy temperature in a rubber plantation (RP) and tropical rainforest (TR) in Xishuangbanna, southwestern China. An infrared temperature sensor was installed at each site to measure canopy temperature. In the dry season, the maximum differences (Tc - Ta) between canopy temperature (Tc) and air temperature (Ta) in the RP and TR were 2.6 and 0.1 K, respectively. In the rainy season, the maximum (Tc - Ta) values in the RP and TR were 1.0 and -1.1 K, respectively. There were consistent differences between the two forests, with the RP having higher (Tc - Ta) than the TR throughout the entire year. Infrared measurements of Tc can be used to calculate canopy stomatal conductance in both forests. The difference in (Tc - Ta) at three gc levels with increasing direct radiation in the RP was larger than in the TR, indicating that change in (Tc - Ta) in the RP was relatively sensitive to the degree of stomatal closure.

The Effect of Increased CO2 Mixing Ratio on Water Use Efficiency, Evapo-transpiration, Soil Moisture Content and Stem Flow in two Long-term Field Experiments

NASA Astrophysics Data System (ADS)

Drake, B.; Powell, T.; Li, J.; Hinkle, R.; Rasse, D.

2007-12-01

Stomatal opening in plant leaves control carbon and water exchange between vegetation and the atmosphere. Closure of these water-gates in response to increased atmospheric CO2 mixing ratio's, reduces transpiration under most laboratory and short term experimental conditions. Does this imply however, as atmospheric CO2 rises, and plant canopies expand, that evapo-transpiration (ETR), soil moisture content (SMC), and ecosystem water use efficiency (WUE) will increase? To test this question, field experiments have been and still are conducted using open top chambers. We have exposed native species in Florida Scrub to a carbon dioxide mixing ratio of nearly 700 ppmv CO2 for the past ten years and in Chesapeake Bay wetlands for 21 years. As a result of this treatment, in both ecosystems there was an increase in net ecosystem CO2 exchange and leaf area but a reduction of stomatal conductance, stem flow, transpiration, and ETR. For Florida scrub oak, these changes were also accompanied by an increase in soil moisture content as well.

A new positive relationship between pCO2 and stomatal frequency in Quercus guyavifolia (Fagaceae): a potential proxy for palaeo-CO2 levels

PubMed Central

Hu, Jin-Jin; Xing, Yao-Wu; Turkington, Roy; Jacques, Frédéric M. B.; Su, Tao; Huang, Yong-Jiang; Zhou, Zhe-Kun

2015-01-01

Background and Aims The inverse relationship between atmospheric CO2 partial pressure (pCO2) and stomatal frequency in many species of plants has been widely used to estimate palaeoatmospheric CO2 (palaeo-CO2) levels; however, the results obtained have been quite variable. This study attempts to find a potential new proxy for palaeo-CO2 levels by analysing stomatal frequency in Quercus guyavifolia (Q. guajavifolia, Fagaceae), an extant dominant species of sclerophyllous forests in the Himalayas with abundant fossil relatives. Methods Stomatal frequency was analysed for extant samples of Q. guyavifolia collected from17 field sites at altitudes ranging between 2493 and 4497 m. Herbarium specimens collected between 1926 and 2011 were also examined. Correlations of pCO2–stomatal frequency were determined using samples from both sources, and these were then applied to Q. preguyavaefolia fossils in order to estimate palaeo-CO2 concentrations for two late-Pliocene floras in south-western China. Key Results In contrast to the negative correlations detected for most other species that have been studied, a positive correlation between pCO2 and stomatal frequency was determined in Q. guyavifolia sampled from both extant field collections and historical herbarium specimens. Palaeo-CO2 concentrations were estimated to be approx. 180–240 ppm in the late Pliocene, which is consistent with most other previous estimates. Conclusions A new positive relationship between pCO2 and stomatal frequency in Q. guyavifolia is presented, which can be applied to the fossils closely related to this species that are widely distributed in the late-Cenozoic strata in order to estimate palaeo-CO2 concentrations. The results show that it is valid to use a positive relationship to estimate palaeo-CO2 concentrations, and the study adds to the variety of stomatal density/index relationships that available for estimating pCO2. The physiological mechanisms underlying this positive response are unclear, however, and require further research. PMID:25681824

Nitric Oxide (NO) Measurements in Stomatal Guard Cells.

PubMed

Agurla, Srinivas; Gayatri, Gunja; Raghavendra, Agepati S

2016-01-01

The quantitative measurement of nitric oxide (NO) in plant cells acquired great importance, in view of the multifaceted function and involvement of NO as a signal in various plant processes. Monitoring of NO in guard cells is quite simple because of the large size of guard cells and ease of observing the detached epidermis under microscope. Stomatal guard cells therefore provide an excellent model system to study the components of signal transduction. The levels and functions of NO in relation to stomatal closure can be monitored, with the help of an inverted fluorescence or confocal microscope. We can measure the NO in guard cells by using flouroprobes like 4,5-diamino fluorescein diacetate (DAF-2DA). This fluorescent dye, DAF-2DA, is cell permeable and after entry into the cell, the diacetate group is removed by the cellular esterases. The resulting DAF-2 form is membrane impermeable and reacts with NO to generate the highly fluorescent triazole (DAF-2T), with excitation and emission wavelengths of 488 and 530 nm, respectively. If time-course measurements are needed, the epidermis can be adhered to a cover-glass or glass slide and left in a small petri dishes. Fluorescence can then be monitored at required time intervals; with a precaution that excitation is done minimally, only when a fluorescent image is acquired. The present method description is for the epidermis of Arabidopsis thaliana and Pisum sativum and should work with most of the other dicotyledonous plants.

Numerical Study on the Stomatal Responses to Dry-Hot Wind Episodes and Its Effects on Land-Atmosphere Interactions.

PubMed

Wang, Shu; Zheng, Hui; Liu, Shuhua; Miao, Yucong; Li, Jing

2016-01-01

The wheat production in midland China is under serious threat by frequent Dry-Hot Wind (DHW) episodes with high temperature, low moisture and specific wind as well as intensive heat transfer and evapotranspiration. The numerical simulations of these episodes are important for monitoring grain yield and estimating agricultural water demand. However, uncertainties still remain despite that enormous experiments and modeling studies have been conducted concerning this issue, due to either inaccurate synoptic situation derived from mesoscale weather models or unrealistic parameterizations of stomatal physiology in land surface models. Hereby, we investigated the synoptic characteristics of DHW with widely-used mesoscale model Weather Research and Forecasting (WRF) and the effects of leaf physiology on surface evapotranspiration by comparing two land surface models: The Noah land surface model, and Peking University Land Model (PKULM) with stomata processes included. Results show that the WRF model could well replicate the synoptic situations of DHW. Two types of DHW were identified: (1) prevailing heated dry wind stream forces the formation of DHW along with intense sensible heating and (2) dry adiabatic processes overflowing mountains. Under both situations, the PKULM can reasonably model the stomatal closure phenomena, which significantly decreases both evapotranspiration and net ecosystem exchange of canopy, while these phenomena cannot be resolved in the Noah simulations. Therefore, our findings suggest that the WRF-PKULM coupled method may be a more reliable tool to investigate and forecast DHW as well as be instructive to crop models.

Numerical Study on the Stomatal Responses to Dry-Hot Wind Episodes and Its Effects on Land-Atmosphere Interactions

PubMed Central

Zheng, Hui; Liu, Shuhua; Miao, Yucong; Li, Jing

2016-01-01

The wheat production in midland China is under serious threat by frequent Dry-Hot Wind (DHW) episodes with high temperature, low moisture and specific wind as well as intensive heat transfer and evapotranspiration. The numerical simulations of these episodes are important for monitoring grain yield and estimating agricultural water demand. However, uncertainties still remain despite that enormous experiments and modeling studies have been conducted concerning this issue, due to either inaccurate synoptic situation derived from mesoscale weather models or unrealistic parameterizations of stomatal physiology in land surface models. Hereby, we investigated the synoptic characteristics of DHW with widely-used mesoscale model Weather Research and Forecasting (WRF) and the effects of leaf physiology on surface evapotranspiration by comparing two land surface models: The Noah land surface model, and Peking University Land Model (PKULM) with stomata processes included. Results show that the WRF model could well replicate the synoptic situations of DHW. Two types of DHW were identified: (1) prevailing heated dry wind stream forces the formation of DHW along with intense sensible heating and (2) dry adiabatic processes overflowing mountains. Under both situations, the PKULM can reasonably model the stomatal closure phenomena, which significantly decreases both evapotranspiration and net ecosystem exchange of canopy, while these phenomena cannot be resolved in the Noah simulations. Therefore, our findings suggest that the WRF-PKULM coupled method may be a more reliable tool to investigate and forecast DHW as well as be instructive to crop models. PMID:27648943

An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

NASA Astrophysics Data System (ADS)

Raczka, Brett; Duarte, Henrique F.; Koven, Charles D.; Ricciuto, Daniel; Thornton, Peter E.; Lin, John C.; Bowling, David R.

2016-09-01

Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. We distinguished between isotopic behavior in response to a decrease of δ13C within atmospheric CO2 (Suess effect) vs. photosynthetic discrimination (Δcanopy), by creating a site-customized atmospheric CO2 and δ13C of CO2 time series. We implemented a seasonally varying Vcmax model calibration that best matched site observations of net CO2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ13C of needle and stem tissue, but underestimated the δ13C of bulk soil carbon by 1-2 ‰. The model overestimated the multiyear (2006-2012) average Δcanopy relative to prior data-based estimates by 2-4 ‰. The amplitude of the average seasonal cycle of Δcanopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled An - gs (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled An - gs version used in the default model. The model attributed most of the seasonal variation in discrimination to An, whereas interannual variation in simulated Δcanopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.

Ecophysiological response to seasonal variations in water availability in the arborescent, endemic plant Vellozia gigantea.

PubMed

Morales, Melanie; Garcia, Queila S; Munné-Bosch, Sergi

2015-03-01

The physiological response of plants growing in their natural habitat is strongly determined by seasonal variations in environmental conditions and the interaction of abiotic and biotic stresses. Here, leaf water and nutrient contents, changes in cellular redox state and endogenous levels of stress-related phytohormones (abscisic acid (ABA), salicylic acid and jasmonates) were examined during the rainy and dry season in Vellozia gigantea, an endemic species growing at high elevations in the rupestrian fields of the Espinhaço Range in Brazil. Enhanced stomatal closure and increased ABA levels during the dry season were associated with an efficient control of leaf water content. Moreover, reductions in 12-oxo-phytodienoic acid (OPDA) levels during the dry season were observed, while levels of other jasmonates, such as jasmonic acid and jasmonoyl-isoleucine, were not affected. Changes in ABA and OPDA levels correlated with endogenous concentrations of iron and silicon, hydrogen peroxide, and vitamin E, thus indicating complex interactions between water and nutrient contents, changes in cellular redox state and endogenous hormone concentrations. Results also suggested crosstalk between activation of mechanisms for drought stress tolerance (as mediated by ABA) and biotic stress resistance (mediated by jasmonates), in which vitamin E levels may serve as a control point. It is concluded that, aside from a tight ABA-associated regulation of stomatal closure during the dry season, crosstalk between activation of abiotic and biotic defences, and nutrient accumulation in leaves may be important modulators of plant stress responses in plants growing in their natural habitat. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Short- and Long-Term Feedbacks on Vegetation Water Use: Unifying Evidence from Observations and Modeling

NASA Astrophysics Data System (ADS)

Mackay, D. S.

2001-05-01

Recent efforts to measure and model the interacting influences of climate, soil, and vegetation on soil water and nutrient dynamics have identified numerous important feedbacks that produce nonlinear responses. In particular, plant physiological factors that control rates of transpiration respond to soil water deficits and vapor pressure deficits (VPD) in the short-term, and to climate, nutrient cycling and disturbance in the long-term. The starting point of this presentation is the observation that in many systems, in particular forest ecosystems, conservative water use emerges as a result of short-term closure of stomata in response to high evaporative demand, and long-term vegetative canopy development under nutrient limiting conditions. Evidence for important short-term controls is presented from sap flux measurements of stand transpiration, remote sensing, and modeling of transpiration through a combination of physically-based modeling and Monte Carlo analysis. A common result is a strong association between stomatal conductance (gs) and the negative evaporative gain (∂ gs/∂ VPD) associated with the sensitivity of stomatal closure to rates of water loss. The importance of this association from the standpoint of modeling transpiration depends on the degree of canopy-atmosphere coupling. This suggests possible simplifications to future canopy component models for use in watershed and larger-scale hydrologic models for short-term processes. However, further results are presented from theoretical modeling, which suggest that feedbacks between hydrology and vegetation in current long-term (inter-annual to century) models may be too simple, as they do not capture the spatially variable nature of slow nutrient cycling in response to soil water dynamics and site history. Memory effects in the soil nutrient pools can leave lasting effects on more rapid processes associated with soil, vegetation, atmosphere coupling.

Synergistic Effect of Light and Fusicoccin on Stomatal Opening 1

PubMed Central

Assmann, Sarah M.; Schwartz, Amnon

1992-01-01

Upon incubation of epidermal peels of Commelina communis in 1 millimolar KCl, a synergistic effect of light and low fusicoccin (FC) concentrations on stomatal opening is observed. In 1 millimolar KCl, stomata remain closed even in the light. However, addition of 0.1 micromolar FC results in opening up to 12 micrometers. The same FC concentration stimulates less than 5 micrometers of opening in darkness. The synergistic effect (a) decreases with increasing FC or KCl concentrations; (b) is dark-reversible; (c) like stomatal opening in high KCl concentrations (120 millimolar) is partially inhibited by the K+ channel blocker, tetraethyl-ammonium+ (20 millimolar). In whole-cell patch-clamp experiments with guard cell protoplasts of Vicia faba, FC (1 or 10 micromolar) stimulates an increase in outward current that is essentially voltage independent between - 100 and +60 millivolts, and occurs even when the membrane potential is held at a voltage (−60 millivolts) at which K+ channels are inactivated. These results are indicative of FC activation of a H+ pump. FC effects on the magnitude of inward and outward K+ currents are not observed. Epidermal peel and patch clamp data are both consistent with the hypothesis that the plasma membrane H+ ATPase of guard cells is a primary locus for the FC effect on stomatal apertures. PMID:16668799

Pragmatic hydraulic theory predicts stomatal responses to climatic water deficits.

PubMed

Sperry, John S; Wang, Yujie; Wolfe, Brett T; Mackay, D Scott; Anderegg, William R L; McDowell, Nate G; Pockman, William T

2016-11-01

Ecosystem models have difficulty predicting plant drought responses, partially from uncertainty in the stomatal response to water deficits in soil and atmosphere. We evaluate a 'supply-demand' theory for water-limited stomatal behavior that avoids the typical scaffold of empirical response functions. The premise is that canopy water demand is regulated in proportion to threat to supply posed by xylem cavitation and soil drying. The theory was implemented in a trait-based soil-plant-atmosphere model. The model predicted canopy transpiration (E), canopy diffusive conductance (G), and canopy xylem pressure (P canopy ) from soil water potential (P soil ) and vapor pressure deficit (D). Modeled responses to D and P soil were consistent with empirical response functions, but controlling parameters were hydraulic traits rather than coefficients. Maximum hydraulic and diffusive conductances and vulnerability to loss in hydraulic conductance dictated stomatal sensitivity and hence the iso- to anisohydric spectrum of regulation. The model matched wide fluctuations in G and P canopy across nine data sets from seasonally dry tropical forest and piñon-juniper woodland with < 26% mean error. Promising initial performance suggests the theory could be useful in improving ecosystem models. Better understanding of the variation in hydraulic properties along the root-stem-leaf continuum will simplify parameterization. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Incorporating Conservation Zone Effectiveness for Protecting Biodiversity in Marine Planning

PubMed Central

Makino, Azusa; Klein, Carissa J.; Beger, Maria; Jupiter, Stacy D.; Possingham, Hugh P.

2013-01-01

Establishing different types of conservation zones is becoming commonplace. However, spatial prioritization methods that can accommodate multiple zones are poorly understood in theory and application. It is typically assumed that management regulations across zones have differential levels of effectiveness (“zone effectiveness”) for biodiversity protection, but the influence of zone effectiveness on achieving conservation targets has not yet been explored. Here, we consider the zone effectiveness of three zones: permanent closure, partial protection, and open, for planning for the protection of five different marine habitats in the Vatu-i-Ra Seascape, Fiji. We explore the impact of differential zone effectiveness on the location and costs of conservation priorities. We assume that permanent closure zones are fully effective at protecting all habitats, open zones do not contribute towards the conservation targets and partial protection zones lie between these two extremes. We use four different estimates for zone effectiveness and three different estimates for zone cost of the partial protection zone. To enhance the practical utility of the approach, we also explore how much of each traditional fishing ground can remain open for fishing while still achieving conservation targets. Our results show that all of the high priority areas for permanent closure zones would not be a high priority when the zone effectiveness of the partial protection zone is equal to that of permanent closure zones. When differential zone effectiveness and costs are considered, the resulting marine protected area network consequently increases in size, with more area allocated to permanent closure zones to meet conservation targets. By distributing the loss of fishing opportunity equitably among local communities, we find that 84–88% of each traditional fishing ground can be left open while still meeting conservation targets. Finally, we summarize the steps for developing marine zoning that accounts for zone effectiveness. PMID:24223870

Combined low temperature-high light effects on gas exchange properties of jojoba leaves.

PubMed

Loreto, F; Bongi, G

1989-12-01

Jojoba (Simmondsia chinensis [Link] Schneider) is an important crop in desert climates. A relatively high frequency of periods of chilling and high photon flux density (PFD) in this environment makes photoinhibition likely, resulting in a reduction of assimilation capacity in overwintering leaves. This could explain the low net photosynthesis found in shoots from the field (4-6 micromoles per square meter per second) when compared to greenhouse grown plants (12-15 micromoles per square meter per second). The responses of photosynthesis and stomatal conductance to changes in absorbed PFD and in substomatal partial pressure of CO(2) were measured on jojoba leaves recovering from chilling temperature (4 degrees C) in high or low PFD. No measurable gas exchange was found immediately after chilling in either high or low PFD. For leaves chilled in low PFD, the original quantum yield was restored after 24 hours. The time course of recovery from chilling in high PFD was much longer. Quantum yield recovered to 60% of its original value in 72 hours but failed to recover fully after 1 week. Measurements of PSII chlorophyll fluorescence at 77 K showed that the reduced quantum yield was caused by photoinhibition. The ratio of variable to maximal fluorescence fell from a control level of 0.82 to 0.41 after the photoinhibitory treatment and recovery was slow. We also found a large increase in net assimilation rate and little closure of stomata as CO(2) was increased from ambient partial pressure of 35 to 85 pascals. For plants grown in full light, the increase in net assimilation rate was 100%. The photosynthetic response at high CO(2) concentration may constitute an ecological advantage of jojoba as a crop in the future.

Combined Low Temperature-High Light Effects on Gas Exchange Properties of Jojoba Leaves 1

PubMed Central

Loreto, Francesco; Bongi, Guido

1989-01-01

Jojoba (Simmondsia chinensis [Link] Schneider) is an important crop in desert climates. A relatively high frequency of periods of chilling and high photon flux density (PFD) in this environment makes photoinhibition likely, resulting in a reduction of assimilation capacity in overwintering leaves. This could explain the low net photosynthesis found in shoots from the field (4-6 micromoles per square meter per second) when compared to greenhouse grown plants (12-15 micromoles per square meter per second). The responses of photosynthesis and stomatal conductance to changes in absorbed PFD and in substomatal partial pressure of CO2 were measured on jojoba leaves recovering from chilling temperature (4°C) in high or low PFD. No measurable gas exchange was found immediately after chilling in either high or low PFD. For leaves chilled in low PFD, the original quantum yield was restored after 24 hours. The time course of recovery from chilling in high PFD was much longer. Quantum yield recovered to 60% of its original value in 72 hours but failed to recover fully after 1 week. Measurements of PSII chlorophyll fluorescence at 77 K showed that the reduced quantum yield was caused by photoinhibition. The ratio of variable to maximal fluorescence fell from a control level of 0.82 to 0.41 after the photoinhibitory treatment and recovery was slow. We also found a large increase in net assimilation rate and little closure of stomata as CO2 was increased from ambient partial pressure of 35 to 85 pascals. For plants grown in full light, the increase in net assimilation rate was 100%. The photosynthetic response at high CO2 concentration may constitute an ecological advantage of jojoba as a crop in the future. PMID:16667220

40 CFR 265.112 - Closure plan; amendment of plan.

Code of Federal Regulations, 2010 CFR

2010-07-01

... residues and contaminated containment system components, equipment, structures, and soils during partial... contaminated soils, methods for sampling and testing surrounding soils, and criteria for determining the extent of decontamination necessary to satisfy the closure performance standard; and (5) A detailed...

40 CFR 264.112 - Closure plan; amendment of plan.

Code of Federal Regulations, 2010 CFR

2010-07-01

... residues and contaminated containment system components, equipment, structures, and soils during partial... contaminated soils, methods for sampling and testing surrounding soils, and criteria for determining the extent of decontamination required to satisfy the closure performance standard; and (5) A detailed...

Modeling the interaction between plant canopies and the planetary boundary layer using a new 1D multi-layer soil- vegetation-atmosphere transfer (SVAT) scheme combined with a non-local turbulence closure model

NASA Astrophysics Data System (ADS)

Yetzer, Kenneth H.

A new one-dimensional (1D) soil-vegetation-atmospheric transport (SVAT) scheme is coupled to a nonlocal turbulence closure model in order to simulate the interactions between a forested canopy and the planetary boundary layer. The SVAT consists of mechanistic models for both physiological (photosynthesis, stomatal conductance and soil/root and bole respiration) and micrometeorological (radiative transfer and surface energy exchanges) processes. The turbulence closure model is a first-order, nonlocal turbulence closure called transilient turbulence theory (Stull, 1993; Inclan et al., 1995) which includes the effects of form drag, wake turbulence, and interference to vertical mixing by the plant elements. The submodel that accounts for radiative transfer inside the forest has been taken from Norman (1979) and Baldocchi (1989). It includes the effect of varying mean leaf inclination angle with height and it also accounts for leaf clumping The photosynthesis submodel is taken from Nikolov and others (1995). It accounts for both differences between shaded and sunlit leaves and the variation of photosynthetic capacity with height. The model was tested with data obtained from a deciduous forest in Pennsylvania. The results show reasonable agreement with the observations. They also demonstrate the model's ability to simulate phenomena that is characteristic of tall canopies like forests, including counter gradient-fluxes and local wind speed maxima in the trunk space.

Effects of elevated root zone CO2 and air temperature on photosynthetic gas exchange, nitrate uptake, and total reduced nitrogen content in aeroponically grown lettuce plants.

PubMed

He, Jie; Austin, Paul T; Lee, Sing Kong

2010-09-01

Effects of elevated root zone (RZ) CO(2) and air temperature on photosynthesis, productivity, nitrate (NO(3)(-)), and total reduced nitrogen (N) content in aeroponically grown lettuce plants were studied. Three weeks after transplanting, four different RZ [CO(2)] concentrations [ambient (360 ppm) and elevated concentrations of 2000, 10,000, and 50,000 ppm] were imposed on plants grown at two air temperature regimes of 28 degrees C/22 degrees C (day/night) and 36 degrees C/30 degrees C. Photosynthetic CO(2) assimilation (A) and stomatal conductance (g(s)) increased with increasing photosynthetically active radiation (PAR). When grown at 28 degrees C/22 degrees C, all plants accumulated more biomass than at 36 degrees C/30 degrees C. When measured under a PAR >or=600 micromol m(-2) s(-1), elevated RZ [CO(2)] resulted in significantly higher A, lower g(s), and higher midday leaf relative water content in all plants. Under elevated RZ [CO(2)], the increase of biomass was greater in roots than in shoots, causing a lower shoot/root ratio. The percentage increase in growth under elevated RZ [CO(2)] was greater at 36 degrees C/30 degrees C although the total biomass was higher at 28 degrees C/22 degrees C. NO(3)(-) and total reduced N concentrations of shoot and root were significantly higher in all plants under elevated RZ [CO(2)] than under ambient RZ [CO(2)] of 360 ppm at both temperature regimes. At each RZ [CO(2)], NO(3)(-) and total reduced N concentration of shoots were greater at 28 degrees C/22 degrees C than at 36 degrees C/30 degrees C. At all RZ [CO(2)], roots of plants at 36 degrees C/30 degrees C had significantly higher NO(3)(-) and total reduced N concentrations than at 28 degrees C/22 degrees C. Since increased RZ [CO(2)] caused partial stomatal closure, maximal A and maximal g(s) were negatively correlated, with a unique relationship for each air temperature. However, across all RZ [CO(2)] and temperature treatments, there was a close correlation between maximal A and total shoot reduced N concentration of plants under different RZ [CO(2)], indicating that increased A under elevated RZ [CO(2)] could partially be due to the higher shoot total reduced N.

Genetic Analysis of Ca 2+ Priming in Arabidopsis Guard Cell Stomatal Closure in Response to the Drought Hormone Abscisic Acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stephan, Aaron B.

2014-11-01

A primary objective of modern agriculture and biofuel production is to utilize arable land to its fullest potential. However, sub-optimal growing conditions—arising from abiotic stresses such as drought, soil salinity, low humidity, cold, and heat—reduce crop yield and quality. Optimal yield under both stressed and non-stressed conditions requires the plant to activate coping mechanisms at a level commensurate with the severity of the drought stress. The osmotic sensors and associated regulatory mechanisms that initiate drought- and salt-tolerance responses in plants are largely unknown. This research aimed to identify and characterize these initial sensory components.

Use of the rhomboid flap after partial vulvectomy.

PubMed

Barnhill, D R; Hoskins, W J; Metz, P

1983-10-01

Primary closure of vulvar excisions is usually satisfactory in the anterior vulva, where the skin is mobile. In the posterior and posterolateral areas, however, closure often must be accomplished under tension with resulting wound breakdown and scar formation that can be disfiguring and cause dyspareunia. The rhomboid skin flap was described as early as 1946. Initially described for closure of facial defects, the technique has found application in the closure of a variety of traumatic and surgical defects. The authors present eight patients who underwent closure of vulvar defects using single or multiple rhomboid flaps. The applicability of the procedure to vulvar surgery is discussed and the technique is described.

Maturation of Atriplex halimus L. leaves involves changes in the molecular regulation of stomatal conductance under high evaporative demand and high but not low soil water content.

PubMed

Nada, Reham M; Khedr, Abdel Hamid A; Serag, Mamdouh S; El-Qashlan, Nesma R; Abogadallah, Gaber M

2018-06-19

Under high water availability, the maximum gas exchange was observed at noon in the expanding and expanded leaves. The expanded leaves showed lower gas exchange capacity due to the regulation of stomatal-movement genes. Under well-watered condition, stomatal conductance (g s ) and photosynthetic rate (A) of expanding and expanded leaves of Atriplex halimus peaked at noon despite the midday decline in the leaf relative water content, suggesting deviation from typical isohydric behaviour. However, the expanding leaves had higher g s and A than the expanded ones. When light intensity was temporarily increased, A and g s were enhanced in both types of leaves though to a higher level in the expanding leaves. In well-watered expanded leaves: (1) A was mainly dependent on g s rather than photosynthetic capacity; g s was controlled by internal factors, thereby limiting water loss via transpiration (E); (2) the accumulation of total soluble sugars (TSS) along with increased Rubisco protein could be a subsidiary factor limiting A; (3) TSS and ABA seem to act in co-ordination to up-regulate ABA-dependent genes controlling g s and (4) the significant induction of DREBs suggests a role in maintaining high relative water content in these leaves compared to the expanding ones. In expanding leaves of well-watered plants, high A along with Rubisco down-regulation and elevated TSS suggests that A was regulated by signals coordinating carbon and nitrogen balance and the elevated ABA could be involved in regulating the hydraulic activity to enhance cell expansion and facilitate leaf growth. Both expanded and expanding leaves behaved in typical isohydric manner under water stress, which did not involve the accumulation of ABA suggesting that stomatal closure was primarily stimulated by hydraulic rather than chemical signals.

Evidence from Amazonian forests is consistent with isohydric control of leaf water potential.

PubMed

Fisher, Rosie A; Williams, Mathew; Do Vale, Raquel Lobo; Da Costa, Antonio Lola; Meir, Patrick

2006-02-01

Climate modelling studies predict that the rain forests of the Eastern Amazon basin are likely to experience reductions in rainfall of up to 50% over the next 50-100 years. Efforts to predict the effects of changing climate, especially drought stress, on forest gas exchange are currently limited by uncertainty about the mechanism that controls stomatal closure in response to low soil moisture. At a through-fall exclusion experiment in Eastern Amazonia where water was experimentally excluded from the soil, we tested the hypothesis that plants are isohydric, that is, when water is scarce, the stomata act to prevent leaf water potential from dropping below a critical threshold level. We made diurnal measurements of leaf water potential (psi 1), stomatal conductance (g(s)), sap flow and stem water potential (psi stem) in the wet and dry seasons. We compared the data with the predictions of the soil-plant-atmosphere (SPA) model, which embeds the isohydric hypothesis within its stomatal conductance algorithm. The model inputs for meteorology, leaf area index (LAI), soil water potential and soil-to-leaf hydraulic resistance (R) were altered between seasons in accordance with measured values. No optimization parameters were used to adjust the model. This 'mechanistic' model of stomatal function was able to explain the individual tree-level seasonal changes in water relations (r2 = 0.85, 0.90 and 0.58 for psi 1, sap flow and g(s), respectively). The model indicated that the measured increase in R was the dominant cause of restricted water use during the dry season, resulting in a modelled restriction of sap flow four times greater than that caused by reduced soil water potential. Higher resistance during the dry season resulted from an increase in below-ground resistance (including root and soil-to-root resistance) to water flow.

Multiple Targets of Salicylic Acid and Its Derivatives in Plants and Animals

PubMed Central

Klessig, Daniel F.; Tian, Miaoying; Choi, Hyong Woo

2016-01-01

Salicylic acid (SA) is a critical plant hormone that is involved in many processes, including seed germination, root initiation, stomatal closure, floral induction, thermogenesis, and response to abiotic and biotic stresses. Its central role in plant immunity, although extensively studied, is still only partially understood. Classical biochemical approaches and, more recently, genome-wide high-throughput screens have identified more than two dozen plant SA-binding proteins (SABPs), as well as multiple candidates that have yet to be characterized. Some of these proteins bind SA with high affinity, while the affinity of others exhibit is low. Given that SA levels vary greatly even within a particular plant species depending on subcellular location, tissue type, developmental stage, and with respect to both time and location after an environmental stimulus such as infection, the presence of SABPs exhibiting a wide range of affinities for SA may provide great flexibility and multiple mechanisms through which SA can act. SA and its derivatives, both natural and synthetic, also have multiple targets in animals/humans. Interestingly, many of these proteins, like their plant counterparts, are associated with immunity or disease development. Two recently identified SABPs, high mobility group box protein and glyceraldehyde 3-phosphate dehydrogenase, are critical proteins that not only serve key structural or metabolic functions but also play prominent roles in disease responses in both kingdoms. PMID:27303403

Separation and Measurement of Direct and Indirect Effects of Light on Stomata 1

PubMed Central

Sharkey, Thomas D.; Raschke, Klaus

1981-01-01

Conductance for water vapor, assimilation of CO2, and intercellular CO2 concentration of leaves of five species were determined at various irradiances and ambient CO2 concentrations. Conductance and assimilation were then plotted as functions of irradiance and intercellular CO2 concentration. The slopes of these curves allowed us to estimate infinitesimal changes in conductance (and assimilation) that occurred when irradiance changed and intercellular CO2 concentration was constant, and when CO2 concentration changed and irradiance was constant. On leaves of Xanthium strumarium L., Gossypium hirsutum L., Phaseolus vulgaris L., and Perilla frutescens (L.), Britt., the stomatal response to light was determined to be mainly a direct response to light and to a small extent only a response to changes in intercellular CO2 concentration. This was also true for stomata of Zea mays L., except at irradiances < 150 watts per square meter, when stomata responded primarily to the depletion of the intercellular spaces of CO2 which in turn was caused by changes in the assimilation of CO2. Stomata responded to light even in leaves whose net exchange of CO2 was reduced to zero through application of the inhibitor of photosynthetic electron transport, cyanazine (2-chloro-4[1-cyano-1-methylethylamino]-6-ethylamino-S-triazine). When leaves were inverted and irradiated on the abaxial surface, conductance decreased in the shaded and increased in the illuminated epidermis, indicating that the photoreceptor pigment(s) involved are located in the epidermis (presumably in the guard cells). In leaves of X. strumarium, the direct effect of light on conductance is primarily a response to blue light. Stomatal responses to CO2 and to light opposed each other. In X. strumarium, stomatal opening in response to light was strongest in CO2 free air and saturated at lower irradiances than in CO2 containing air. Conversely, stomatal closure in response to CO2 was strongest in darkness and it decreased as irradiance increased. In X. strumarium, P. vulgaris, and P. frutescens, an irradiance of 300 watts per square meter was sufficient to eliminate the stomatal response to CO2 altogether. Application of abscisic acid, or an increase in vapor pressure deficit, or a decrease in leaf temperature reduced the stomatal conductance at light saturation, but when the data were normalized with respect to the conductance at the highest irradiance, the various curves were congruent. PMID:16661884

Oryza sativa H+-ATPase (OSA) is Involved in the Regulation of Dumbbell-Shaped Guard Cells of Rice.

PubMed

Toda, Yosuke; Wang, Yin; Takahashi, Akira; Kawai, Yuya; Tada, Yasuomi; Yamaji, Naoki; Feng Ma, Jian; Ashikari, Motoyuki; Kinoshita, Toshinori

2016-06-01

The stomatal apparatus consists of a pair of guard cells and regulates gas exchange between the leaf and atmosphere. In guard cells, blue light (BL) activates H(+)-ATPase in the plasma membrane through the phosphorylation of its penultimate threonine, mediating stomatal opening. Although this regulation is thought to be widely adopted among kidney-shaped guard cells in dicots, the molecular basis underlying that of dumbbell-shaped guard cells in monocots remains unclear. Here, we show that H(+)-ATPases are involved in the regulation of dumbbell-shaped guard cells. Stomatal opening of rice was promoted by the H(+)-ATPase activator fusicoccin and by BL, and the latter was suppressed by the H(+)-ATPase inhibitor vanadate. Using H(+)-ATPase antibodies, we showed the presence of phosphoregulation of the penultimate threonine in Oryza sativa H(+)-ATPases (OSAs) and localization of OSAs in the plasma membrane of guard cells. Interestingly, we identified one H(+)-ATPase isoform, OSA7, that is preferentially expressed among the OSA genes in guard cells, and found that loss of function of OSA7 resulted in partial insensitivity to BL. We conclude that H(+)-ATPase is involved in BL-induced stomatal opening of dumbbell-shaped guard cells in monocotyledon species. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists.

GID1 modulates stomatal response and submergence tolerance involving abscisic acid and gibberellic acid signaling in rice.

PubMed

Du, Hao; Chang, Yu; Huang, Fei; Xiong, Lizhong

2015-11-01

Plant responses to abiotic stresses are coordinated by arrays of growth and developmental programs. Gibberellic acid (GA) and abscisic acid (ABA) play critical roles in the developmental programs and environmental responses, respectively, through complex signaling and metabolism networks. However, crosstalk between the two phytohormones in stress responses remains largely unknown. In this study, we report that GIBBERELLIN-INSENSITIVE DWARF 1 (GID1), a soluble receptor for GA, regulates stomatal development and patterning in rice (Oryza sativa L.). The gid1 mutant showed impaired biosynthesis of endogenous ABA under drought stress conditions, but it exhibited enhanced sensitivity to exogenous ABA. Scanning electron microscope and infrared thermal image analysis indicated an increase in the stomatal conductance in the gid1 mutant under drought conditions. Interestingly, the gid1 mutant had increased levels of chlorophyll and carbohydrates under submergence conditions, and showed enhanced reactive oxygen species (ROS)-scavenging ability and submergence tolerance compared with the wild-type. Further analyses suggested that the function of GID1 in submergence responses is partially dependent on ABA, and GA signaling by GID1 is involved in submergence tolerance by modulating carbohydrate consumption. Taken together, these findings suggest GID1 plays distinct roles in stomatal response and submergence tolerance through both the ABA and GA signaling pathways in rice. © 2014 Institute of Botany, Chinese Academy of Sciences.

A CBL-Interacting Protein Kinase TaCIPK2 Confers Drought Tolerance in Transgenic Tobacco Plants through Regulating the Stomatal Movement.

PubMed

Wang, Yan; Sun, Tao; Li, Tingting; Wang, Meng; Yang, Guangxiao; He, Guangyuan

2016-01-01

In plants, the CBL-CIPK signaling pathways play key roles in the response to abiotic stresses. However, functional studies of CIPKs in the important staple crop wheat are very rare. In this study, we identified a CIPK gene from wheat, designated TaCIPK2. Expression analysis results showed that TaCIPK2 could be up-regulated in wheat leaves by polyethylene glycol, abscisic acid and H2O2 treatments. Subcellular localization analyses revealed that TaCIPK2 was present in whole wheat epidermal cells. A yeast two-hybrid assay indicated that TaCIPK2 interacted with TaCBL1, 2, 3 and 4 in vitro. Transgenic tobacco plants over-expressing TaCIPK2 exhibited increased drought tolerance, indicated by a larger proportion of green cotyledons and higher survival rates under the osmotic and drought stress conditions compared with control plants. Additionally, physiological index analyses revealed that the transgenic tobacco plants had lower water loss rates and ion leakage, accumulated less malondialdehyde and H2O2, and had higher catalase and superoxide dismutase activities than the control plants. The transgenic plants also exhibited faster stomatal closure following exposure to osmotic stress conditions. The seed germination rates and stomatal aperture of TaCIPK2-overexpressing tobacco plants decreased after exogenous abscisic acid treatment was applied, implying that the transgenic tobacco plants were more sensitive to exogenous abscisic acid than the control plants. Our results indicate that TaCIPK2 plays a positive regulatory role in drought stress responses in transgenic tobacco plants.

A Major Facilitator Superfamily Transporter Plays a Dual Role in Polar Auxin Transport and Drought Stress Tolerance in Arabidopsis[W

PubMed Central

Remy, Estelle; Cabrito, Tânia R.; Baster, Pawel; Batista, Rita A.; Teixeira, Miguel C.; Friml, Jiri; Sá-Correia, Isabel; Duque, Paula

2013-01-01

Many key aspects of plant development are regulated by the polarized transport of the phytohormone auxin. Cellular auxin efflux, the rate-limiting step in this process, has been shown to rely on the coordinated action of PIN-formed (PIN) and B-type ATP binding cassette (ABCB) carriers. Here, we report that polar auxin transport in the Arabidopsis thaliana root also requires the action of a Major Facilitator Superfamily (MFS) transporter, Zinc-Induced Facilitator-Like 1 (ZIFL1). Sequencing, promoter-reporter, and fluorescent protein fusion experiments indicate that the full-length ZIFL1.1 protein and a truncated splice isoform, ZIFL1.3, localize to the tonoplast of root cells and the plasma membrane of leaf stomatal guard cells, respectively. Using reverse genetics, we show that the ZIFL1.1 transporter regulates various root auxin-related processes, while the ZIFL1.3 isoform mediates drought tolerance by regulating stomatal closure. Auxin transport and immunolocalization assays demonstrate that ZIFL1.1 indirectly modulates cellular auxin efflux during shootward auxin transport at the root tip, likely by regulating plasma membrane PIN2 abundance. Finally, heterologous expression in yeast revealed that ZIFL1.1 and ZIFL1.3 share H+-coupled K+ transport activity. Thus, by determining the subcellular and tissue distribution of two isoforms, alternative splicing dictates a dual function for the ZIFL1 transporter. We propose that this MFS carrier regulates stomatal movements and polar auxin transport by modulating potassium and proton fluxes in Arabidopsis cells. PMID:23524662

Thermography to explore plant-environment interactions.

PubMed

Costa, J Miguel; Grant, Olga M; Chaves, M Manuela

2013-10-01

Stomatal regulation is a key determinant of plant photosynthesis and water relations, influencing plant survival, adaptation, and growth. Stomata sense the surrounding environment and respond rapidly to abiotic and biotic stresses. Stomatal conductance to water vapour (g s) and/or transpiration (E) are therefore valuable physiological parameters to be monitored in plant and agricultural sciences. However, leaf gas exchange measurements involve contact with leaves and often interfere with leaf functioning. Besides, they are time consuming and are limited by the sampling characteristics (e.g. sample size and/or the high number of samples required). Remote and rapid means to assess g s or E are thus particularly valuable for physiologists, agronomists, and ecologists. Transpiration influences the leaf energy balance and, consequently, leaf temperature (T leaf). As a result, thermal imaging makes it possible to estimate or quantify g s and E. Thermal imaging has been successfully used in a wide range of conditions and with diverse plant species. The technique can be applied at different scales (e.g. from single seedlings/leaves through whole trees or field crops to regions), providing great potential to study plant-environment interactions and specific phenomena such as abnormal stomatal closure, genotypic variation in stress tolerance, and the impact of different management strategies on crop water status. Nevertheless, environmental variability (e.g. in light intensity, temperature, relative humidity, wind speed) affects the accuracy of thermal imaging measurements. This review presents and discusses the advantages of thermal imaging applications to plant science, agriculture, and ecology, as well as its limitations and possible approaches to minimize them, by highlighting examples from previous and ongoing research.

Zn2+-induced changes at the root level account for the increased tolerance of acclimated tobacco plants

PubMed Central

Bazihizina, Nadia; Taiti, Cosimo; Marti, Lucia; Rodrigo-Moreno, Ana; Spinelli, Francesco; Giordano, Cristiana; Caparrotta, Stefania; Gori, Massimo; Azzarello, Elisa; Mancuso, Stefano

2014-01-01

Evidence suggests that heavy-metal tolerance can be induced in plants following pre-treatment with non-toxic metal concentrations, but the results are still controversial. In the present study, tobacco plants were exposed to increasing Zn2+ concentrations (up to 250 and/or 500 μM ZnSO4) with or without a 1-week acclimation period with 30 μM ZnSO4. Elevated Zn2+ was highly toxic for plants, and after 3 weeks of treatments there was a marked (≥50%) decline in plant growth in non-acclimated plants. Plant acclimation, on the other hand, increased plant dry mass and leaf area up to 1.6-fold compared with non-acclimated ones. In non-acclimated plants, the addition of 250 μM ZnSO4 led to transient membrane depolarization and stomatal closure within 24h from the addition of the stress; by contrast, the acclimation process was associated with an improved stomatal regulation and a superior ability to maintain a negative root membrane potential, with values on average 37% more negative compared with non-acclimated plants. The different response at the plasma-membrane level between acclimated and non-acclimated plants was associated with an enhanced vacuolar Zn2+ sequestration and up to 2-fold higher expression of the tobacco orthologue of the Arabidopsis thaliana MTP1 gene. Thus, the acclimation process elicited specific detoxification mechanisms in roots that enhanced Zn2+ compartmentalization in vacuoles, thereby improving root membrane functionality and stomatal regulation in leaves following elevated Zn2+ stress. PMID:24928985

Photosynthetic induction and its diffusional, carboxylation and electron transport processes as affected by CO2 partial pressure, temperature, air humidity and blue irradiance.

PubMed

Kaiser, Elias; Kromdijk, Johannes; Harbinson, Jeremy; Heuvelink, Ep; Marcelis, Leo F M

2017-01-01

Plants depend on photosynthesis for growth. In nature, factors such as temperature, humidity, CO 2 partial pressure, and spectrum and intensity of irradiance often fluctuate. Whereas irradiance intensity is most influential and has been studied in detail, understanding of interactions with other factors is lacking. We tested how photosynthetic induction after dark-light transitions was affected by CO 2 partial pressure (20, 40, 80 Pa), leaf temperatures (15·5, 22·8, 30·5 °C), leaf-to-air vapour pressure deficits (VPD leaf-air ; 0·5, 0·8, 1·6, 2·3 kPa) and blue irradiance (0-20 %) in tomato leaves (Solanum lycopersicum). Rates of photosynthetic induction strongly increased with CO 2 partial pressure, due to increased apparent Rubisco activation rates and reduced diffusional limitations. High leaf temperature produced slightly higher induction rates, and increased intrinsic water use efficiency and diffusional limitation. High VPD leaf-air slowed down induction rates and apparent Rubisco activation and (at 2·3 kPa) induced damped stomatal oscillations. Blue irradiance had no effect. Slower apparent Rubisco activation in elevated VPD leaf-air may be explained by low leaf internal CO 2 partial pressure at the beginning of induction. The environmental factors CO 2 partial pressure, temperature and VPD leaf-air had significant impacts on rates of photosynthetic induction, as well as on underlying diffusional, carboxylation and electron transport processes. Furthermore, maximizing Rubisco activation rates would increase photosynthesis by at most 6-8 % in ambient CO 2 partial pressure (across temperatures and humidities), while maximizing rates of stomatal opening would increase photosynthesis by at most 1-3 %. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

40 CFR 265.112 - Closure plan; amendment of plan.

Code of Federal Regulations, 2013 CFR

2013-07-01

... (CONTINUED) INTERIM STATUS STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE TREATMENT, STORAGE, AND.... By May 19, 1981, or by six months after the effective date of the rule that first subjects a facility... description of other activities necessary during the partial and final closure periods to ensure that all...

An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raczka, Brett; Duarte, Henrique F.; Koven, Charles D.

Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO 2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. Wemore » distinguished between isotopic behavior in response to a decrease of δ 13C within atmospheric CO 2 (Suess effect) vs. photosynthetic discrimination (Δ canopy), by creating a site-customized atmospheric CO 2 and δ 13C of CO 2 time series. We implemented a seasonally varying V cmax model calibration that best matched site observations of net CO 2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ 13C of needle and stem tissue, but underestimated the δ 13C of bulk soil carbon by 1–2 ‰. The model overestimated the multiyear (2006–2012) average Δ canopy relative to prior data-based estimates by 2–4 ‰. The amplitude of the average seasonal cycle of Δ canopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled A n- g s (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled A n- g s version used in the default model. The model attributed most of the seasonal variation in discrimination to A n, whereas interannual variation in simulated Δ canopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.« less

An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

DOE PAGES

Raczka, Brett; Duarte, Henrique F.; Koven, Charles D.; ...

2016-09-19

Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO 2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. Wemore » distinguished between isotopic behavior in response to a decrease of δ 13C within atmospheric CO 2 (Suess effect) vs. photosynthetic discrimination (Δ canopy), by creating a site-customized atmospheric CO 2 and δ 13C of CO 2 time series. We implemented a seasonally varying V cmax model calibration that best matched site observations of net CO 2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ 13C of needle and stem tissue, but underestimated the δ 13C of bulk soil carbon by 1–2 ‰. The model overestimated the multiyear (2006–2012) average Δ canopy relative to prior data-based estimates by 2–4 ‰. The amplitude of the average seasonal cycle of Δ canopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled A n- g s (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled A n- g s version used in the default model. The model attributed most of the seasonal variation in discrimination to A n, whereas interannual variation in simulated Δ canopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.« less

Use of cartilage grafts for closure of cleft palate fistulae.

PubMed

Jeffery, S L; Boorman, J G; Dive, D C

2000-10-01

We describe the results of using a free cartilage graft in the closure of cleft palate fistulae in 14 patients with a mean follow-up of 8.6 months. Complete closure of the fistula was achieved in 11 patients (79%), with partial closure in the remaining three patients. This technique is simple, causes relatively little discomfort, involves little tissue dissection and can be performed as a day-case procedure. The success rate is comparable with or better than other methods, and we consider it the treatment of choice for small cleft palate fistulae. Copyright 2000 The British Association of Plastic Surgeons.

Kinetin Reversal of NaCl Effects

PubMed Central

Katz, Adriana; Dehan, Klara; Itai, Chanan

1978-01-01

Leaf discs of Nicotiana rustica L. were floated on NaCl in the presence of kinetin or abscisic acid. On the 5th day 14CO2 fixation, [3H]leucine incorporation, stomatal conductance, and chlorophyll content were determined. Kinetin either partially or completely reversed the inhibitory effects of NaCl while ABA had no effect. PMID:16660618

[Eco-physiological investigations on wild and cultivated plants in the Negev Desert : II. The influence of climatic factors on carbon dioxide exchange and transpiration at the end of the dry period].

PubMed

Schulze, E -D; Lange, O L; Koch, W

1972-12-01

The influence of climatic factors on net photosynthesis, dark respiration and transpiration was investigated in the Negev Desert at the end of the dry summer period when plant water stress was at a maximum. Species studied included: dominant species of the natural vegetation (Artemisia herba-alba, Hammada scoparia, Noaea mucronata, Reaumuria negevensis, Salsola inermis, Zygophyllum dumosum), cultivated plants receiving rainfall and run-off water during the winter season in the run-off farm Avdat (Prunus armeniaca, Vitis vinifera), and irrigated cultivated plants receiving additional water during the summer season (Citrullus colocynthis, Datura metel). 1. Light saturation of net photosynthesis was reached at 60-90 klx conforming to the high solar radiation intensities of the desert. 2. Maximum rates of CO 2 uptake per unit of dry weight for the irrigated mesomorphic plants was ten times that of the wild plants. However, in comparison to the other species, maximal rates of CO 2 uptake for wild plants were higher when calculated on a leaf area basis than when represented on a dry weight basis. Maximum rates of net photosynthesis per unit chlorophyll content for some of the wild plants (Salsola and Noaea) were comparable to those of the cultivated Vitis and irrigated Citrullus and Datura, Hammada exhibited even higher rates than Prunus. This demonstrates the great photosynthetic capacity of the wild plants even at the end of the dry season. 3. The upper temperature compensation point for net photosynthesis of the wild plants was unusually high as an adaptation to the temperatures of the habitat. Compensation points higher than 49°C exceed the maxima known so far for other flowering species. Maximum rates of net photosynthesis of Hammada were measured when the temperature of the photosynthetic organs was 37°C; at 49°C photosynthesis was only reduced by 50%. 4. Leaf temperature affects plant gas exchange by influencing stomatal aperture. Diffusion resistance of leaves to water vapour was reduced at low temperatures and increased at high temperatures. Reduction of net photosynthesis and transpiration of desert plants at midday may, therefore, be the result of temperature-induced stomatal closure. The possible influence of peristomatal transpiration on stomatal aperture is also discussed. Peristomatal transpiration is directly related to the vapour pressure gradient between the leaf mesophyll and the ambient air which increases with increasing temperatures. 5. Diffusion resistance to water vapour was reduced at high temperatures approaching the limits of heat resistance, due to increased stomatal aperture. This resulted in greater transpirational cooling. 6. Under conditions of increased leaf water stress, diffusion resistance increased, either by sudden stomatal closure at specific threshold values of water stress or through a continuous increase in resistance. This increased resistance is coupled with decreases in transpiration and photosynthesis. 7. In several plant species increased diffusion resistance during the course of the day caused decreased transpiration without a corresponding decrease in photosynthesis. Under these conditions, the ratio of CO 2 uptake to transpiration became more favourable as the day progressed. The possibility that this favourable gas exchange response is the result of an increased mesophyll resistance to water vapour loss is discussed.

LES-Modeling of a Partially Premixed Flame using a Deconvolution Turbulence Closure

NASA Astrophysics Data System (ADS)

Wang, Qing; Wu, Hao; Ihme, Matthias

2015-11-01

The modeling of the turbulence/chemistry interaction in partially premixed and multi-stream combustion remains an outstanding issue. By extending a recently developed constrained minimum mean-square error deconvolution (CMMSED) method, to objective of this work is to develop a source-term closure for turbulent multi-stream combustion. In this method, the chemical source term is obtained from a three-stream flamelet model, and CMMSED is used as closure model, thereby eliminating the need for presumed PDF-modeling. The model is applied to LES of a piloted turbulent jet flame with inhomogeneous inlets, and simulation results are compared with experiments. Comparisons with presumed PDF-methods are performed, and issues regarding resolution and conservation of the CMMSED method are examined. The author would like to acknowledge the support of funding from Stanford Graduate Fellowship.

Diurnal Reflectance Changes in Vegetation Observed with AVIRIS

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C.; Ambrosia, V. G.; Ustin, S. L.

1998-01-01

Among the most important short-term dynamic biological processes are diurnal changes in canopy water relations. Plant regulation of water transport through stomatal openings affects other gaseous transport processes, often dramatically decreasing photosynthetic fixation of carbon dioxide during periods of water stress. Water stress reduces stomatal conductance of water vapor through the leaf surface and alters the diurnal timing of stomatal opening. Under non-water stressed conditions, stomates typically open soon after dawn and transpire water vapor throughout the daylight period. During stress periods, stomates may close for part of the day, generally near mid-day. Under prolonged stress conditions, stomatal closure shifts to earlier times during the day; stomates may close by mid-morning and remain closed until the following morning - or remain closed entirely. Under these conditions the relationship between canopy greenness (e.g., measured with a vegetation index or by spectral mixture analysis) and photosynthetic fixation of carbon is lost and the remotely sensed vegetation metric is a poor predictor of gas exchange. Prediction of stomatal regulation and exchange of water and trace gases is critical for ecosystem and climate models to correctly estimate budgets of these gases and understand or predict other processes like gross and net ecosystem primary production. Plant gas exchange has been extensively studied by physiologists at the leaf and whole plant level and by biometeorologists at somewhat larger scales. While these energy driven processes follow a predictable if somewhat asymmetric diurnal cycle dependent on soil water availability and the constraints imposed by the solar energy budget, they are nonetheless difficult to measure at the tree and stand levels using conventional methods. Ecologists have long been interested in the potential of remote sensing for monitoring physiological changes using multi-temporal images. Much of this research has focused on day-to-day changes in water use, especially for agricultural applications. Ustin et al. showed seasonal changes in canopy water content in chaparral shrub could be estimated using optical methods. Vanderbilt et al. followed asymmetric diurnal changes in the reflectance of a walnut orchard, but could not attribute specific reflectance changes to specific changes in canopy architecture or physiology. Forests and shrub lands in California experience prolonged periods of drought, sometimes extending six months without precipitation. The conifer and evergreen chaparral communities common to the foothill region around the central valley of California retain their foliage throughout the summer and have low transpiration rates despite high net radiation and temperature conditions. In contrast, grasslands and drought resistant deciduous species in the same habitat are seasonally dormant in summer. Because of differences in the mechanisms of drought tolerance, rooting depth and physiology between different plant communities in the region, it is likely that they display differences in diurnal water relations. The presence of diverse plant communities provides an opportunity to investigate possible diurnal landscape patterns in water relations that could be observed by an airborne hyperspectral scanner. This investigation of AVIRIS data collected over forest and shrub land represents the continuation of a prior investigation involving spectral mixture analysis of diurnal effects in the same AVIRIS data set.

Mechanistic Basis for Plant Responses to Drought Stress : Regulatory Mechanism of Abscisic Acid Signaling

NASA Astrophysics Data System (ADS)

Miyakawa, Takuya; Tanokura, Masaru

The phytohormone abscisic acid (ABA) plays a key role in the rapid adaptation of plants to environmental stresses such as drought and high salinity. Accumulated ABA in plant cells promotes stomatal closure in guard cells and transcription of stress-tolerant genes. Our understanding of ABA responses dramatically improved by the discovery of both PYR/PYL/RCAR as a soluble ABA receptor and inhibitory complex of a protein phospatase PP2C and a protein kinase SnRK2. Moreover, several structural analyses of PYR/PYL/RCAR revealed the mechanistic basis for the regulatory mechanism of ABA signaling, which provides a rational framework for the design of alternative agonists in future.

Water relations and microclimate around the upper limit of a cloud forest in Maui, Hawai'i.

PubMed

Gotsch, Sybil G; Crausbay, Shelley D; Giambelluca, Thomas W; Weintraub, Alexis E; Longman, Ryan J; Asbjornsen, Heidi; Hotchkiss, Sara C; Dawson, Todd E

2014-07-01

The goal of this study was to determine the effects of atmospheric demand on both plant water relations and daily whole-tree water balance across the upper limit of a cloud forest at the mean base height of the trade wind inversion in the tropical trade wind belt. We measured the microclimate and water relations (sap flow, water potential, stomatal conductance, pressure-volume relations) of Metrosideros polymorpha Gaudich. var. polymorpha in three habitats bracketing the cloud forest's upper limit in Hawai'i to understand the role of water relations in determining ecotone position. The subalpine shrubland site, located 100 m above the cloud forest boundary, had the highest vapor pressure deficit, the least amount of rainfall and the highest levels of nighttime transpiration (EN) of all three sites. In the shrubland site, on average, 29% of daily whole-tree transpiration occurred at night, while on the driest day of the study 50% of total daily transpiration occurred at night. While EN occurred in the cloud forest habitat, the proportion of total daily transpiration that occurred at night was much lower (4%). The average leaf water potential (Ψleaf) was above the water potential at the turgor loss point (ΨTLP) on both sides of the ecotone due to strong stomatal regulation. While stomatal closure maintained a high Ψleaf, the minimum leaf water potential (Ψleafmin) was close to ΨTLP, indicating that drier conditions may cause drought stress in these habitats and may be an important driver of current landscape patterns in stand density. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Changes in Air CO₂ Concentration Differentially Alter Transcript Levels of NtAQP1 and NtPIP2;1 Aquaporin Genes in Tobacco Leaves.

PubMed

Secchi, Francesca; Schubert, Andrea; Lovisolo, Claudio

2016-04-14

The aquaporin specific control on water versus carbon pathways in leaves is pivotal in controlling gas exchange and leaf hydraulics. We investigated whether Nicotiana tabacum aquaporin 1 (NtAQP1) and Nicotiana tabacum plasma membrane intrinsic protein 2;1 (NtPIP2;1) gene expression varies in tobacco leaves subjected to treatments with different CO₂ concentrations (ranging from 0 to 800 ppm), inducing changes in photosynthesis, stomatal regulation and water evaporation from the leaf. Changes in air CO₂ concentration ([CO₂]) affected net photosynthesis (Pn) and leaf substomatal [CO₂] (Ci). Pn was slightly negative at 0 ppm air CO₂; it was one-third that of ambient controls at 200 ppm, and not different from controls at 800 ppm. Leaves fed with 800 ppm [CO₂] showed one-third reduced stomatal conductance (gs) and transpiration (E), and their gs was in turn slightly lower than in 200 ppm- and in 0 ppm-treated leaves. The 800 ppm air [CO₂] strongly impaired both NtAQP1 and NtPIP2;1 gene expression, whereas 0 ppm air [CO₂], a concentration below any in vivo possible conditions and specifically chosen to maximize the gene expression alteration, increased only the NtAQP1 transcript level. We propose that NtAQP1 expression, an aquaporin devoted to CO₂ transport, positively responds to CO₂ scarcity in the air in the whole range 0-800 ppm. On the contrary, expression of NtPIP2;1, an aquaporin not devoted to CO₂ transport, is related to water balance in the leaf, and changes in parallel with gs. These observations fit in a model where upregulation of leaf aquaporins is activated at low Ci, while downregulation occurs when high Ci saturates photosynthesis and causes stomatal closure.

Water transport dynamics in trees and stands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pallardy, S.G.; Cermak, J.; Ewers, F.W.

1995-07-01

Water transport dynamics in trees and stands of conifers have certain features that are characteristic of this group and are at least rare among angiosperms. Among these features is the xylem transport system that is dependent on tracheids for long-distance water transport. Tracheid-containing xylem is relatively inefficient, a property that can reduce submaximum allowable rates of gas exchange, but tracheids also offer substantial capacity for water storage and high resistance to freezing-induced dysfunction. Thus, they are quite compatible with the typical evergreen habit and long transpiration season of conifers. At the stand level, canopy transpiration in conifers is primarily controlledmore » by stomatal conductance. In contrast, in dense canopies of angio-sperms, particularly those of tropical forests with limited air mixing, stand transpiration is limited by radiation input rather than by stomatal control. Because of their evergreen habit a greater proportion of evapotranspiration in conifer forests is associated with evaporation of water intercepted by the tree crowns. Other features of transport dynamics are characteristic of most conifers, but are not unique to this group. Among these features are typically shallow root systems that often must supply water in winter to replace transpiration needs of evergreen species, common occurrence of mycorrhizae that enhance mineral and water uptake, and drought tolerance adaptations that include elements of both dehydration avoidance (e.g., stomatal closure under water stress, shifts in allocation of dry matter to below-ground sinks) and dehydration tolerance (e.g., capacity for acclimation of photosynthetic apparatus to drought, osmotic adjustment). Transpiration rates from conifer foliage often are lower than those of deciduous angiosperms, probably because of the lower maximum capacity of tracheid-bearing xylem to transport water.« less

Environmental controls on sap flow in a northern hardwood forest.

PubMed

Bovard, B D; Curtis, P S; Vogel, C S; Su, H-B; Schmid, H P

2005-01-01

Our objective was to gain a detailed understanding of how photosynthetically active radiation (PAR), vapor pressure deficit (D) and soil water interact to control transpiration in the dominant canopy species of a mixed hardwood forest in northern Lower Michigan. An improved understanding of how these environmental factors affect whole-tree water use in unmanaged ecosystems is necessary in assessing the consequences of climate change on the terrestrial water cycle. We used continuously heated sap flow sensors to measure transpiration in mature trees of four species during two successive drought events. The measurements were scaled to the stand level for comparison with eddy covariance estimates of ecosystem water flux (Fw). Photosynthetically active radiation and D together explained 82% of the daytime hourly variation in plot-level transpiration, and low soil water content generally resulted in increased stomatal sensitivity to increasing D. There were also species-specific responses to drought. Quercus rubra L. showed low water use during both dry and wet conditions, and during periods of high D. Among the study species, Acer rubrum L. showed the greatest degree of stomatal closure in response to low soil water availability. Moderate increases in stomatal sensitivity to D during dry periods were observed in Populus grandidentata Michx. and Betula papyrifera Marsh. Sap flow scaled to the plot level and Fw demonstrated similar temporal patterns of water loss suggesting that the mechanisms controlling sap flow of an individual tree also control ecosystem evapotranspiration. However, the absolute magnitude of scaled sap flow estimates was consistently lower than Fw. We conclude that species-specific responses to PAR, D and soil water content are key elements to understanding current and future water fluxes in this ecosystem.

Carbon dioxide gas exchange and the energy status of leaves of Primula palinuri under water stress.

PubMed

Dietz, K J; Heber, U

1983-08-01

The photosynthetic rate of water stressed leaves of Primula palinuri was reduced drastically by stomatal closure, not by limitations imposed on the capacity of the photosynthetic apparatus, when water loss exceeded 20% of the water content of turgid leaves. The sudden decrease in phtosynthesis was not observed when the lower epidermis of the leaves had been removed. In these 'stripped' leaves, inhibition of photosynthesis increased only gradually during the wilting caused by increasing water stress and was complete when the relative water content was as low as 20% compared with the initial value. This corresponded to a water potential of about-40 bar. The light intensity at which half-maximum rates of photosynthesis were observed decreased as stress increased. In intact leaves photosynthesizing in the presence of CO2, light scattering, which is a measure of thylakoid energization, increased steeply during stomatal closure. The observed increase corresponded to the light scattering level measured in the absence of CO2. When the lower epidermis was removed, no sudden increase in thylakoid energization could be observed during dehydration. Thylakoid energization remained high even at low water potentials. It decreased drastically only below a relative water content of 20%. Irrespective, of the extent of water stress, CO2 fixation of stripped leaves increased when the oxygen content of air was reduced from 21% to 2%. Usually the transition from 21 to 2% O2 was accompanied by increased thylakoid energization. The increase in energization was more pronounced below than above a relative water content of 50%. The data show that energy-dissipating photorespiratory CO2 turnover in the in tercellular space of water-stressed leaves whose stomata are closed decreases only slowly as water stress increases. Respiratory CO2 production by leaves in the dark was even more resistant to water stress than photosynthesis. It was still significant at water potentials as low as-80 bar.

Control of Photosynthesis and Stomatal Conductance in Ricinus communis L. (Castor Bean) by Leaf to Air Vapor Pressure Deficit 1

PubMed Central

Dai, Ziyu; Edwards, Gerald E.; Ku, Maurice S. B.

1992-01-01

Castor bean (Ricinus communis L.) has a high photosynthetic capacity under high humidity and a pronounced sensitivity of photosynthesis to high water vapor pressure deficit (VPD). The sensitivity of photosynthesis to varying VPD was analyzed by measuring CO2 assimilation, stomatal conductance (gs), quantum yield of photosystem II (φII), and nonphotochemical quenching of chlorophyll fluorescence (qN) under different VPD. Under both medium (1000) and high (1800 micromoles quanta per square meter per second) light intensities, CO2 assimilation decreased as the VPD between the leaf and the air around the leaf increased. The gs initially dropped rapidly with increasing VPD and then showed a slower decrease above a VPD of 10 to 20 millibars. Over a temperature range from 20 to 40°C, CO2 assimilation and gs were inhibited by high VPD (20 millibars). However, the rate of transpiration increased with increasing temperature at either low or high VPD due to an increase in gs. The relative inhibition of photosynthesis under photorespiring (atmospheric levels of CO2 and O2) versus nonphotorespiring (700 microbars CO2 and 2% O2) conditions was greater under high VPD (30 millibars) than under low VPD (3 millibars). Also, with increasing light intensity the relative inhibition of photosynthesis by O2 increased under high VPD, but decreased under low VPD. The effect of high VPD on photosynthesis under various conditions could not be totally accounted for by the decrease in the intercellular CO2 in the leaf (Ci) where Ci was estimated from gas exchange measurements. However, estimates of Ci from measurements of φII and qN suggest that the decrease in photosynthesis and increase in photorespiration under high VPD can be totally accounted for by stomatal closure and a decrease in Ci. The results also suggest that nonuniform closure of stomata may occur in well-watered plants under high VPD, causing overestimates in the calculation of Ci from gas exchange measurements. Under low VPD, 30°C, high light, and saturating CO2, castor bean (C3 tropical shrub) has a rate of photosynthesis (61 micromoles CO2 per square meter per second) that is about 50% higher than that of tobacco (C3) or maize (C4) under the same conditions. The chlorophyll content, total soluble protein, and ribulose-1,5-bisphosphate carboxylase/oxygenase level on a leaf area basis were much higher in castor bean than in maize or tobacco, which accounts for its high rates of photosynthesis under low VPD. PMID:16669054

Fish allergy causing angioedema and secondary angle-closure glaucoma.

PubMed

Calder, Donovan; Calder, Jennifer

2013-03-06

A 56-year-old woman with a history of primary angle-closure glaucoma presented with acute generalised swelling, and facial angioedema following a fish meal. She complained of nausea, vomiting, headache, pain in both eyes and acute loss of vision. Her visual acuity was reduced and intraocular pressures (IOP) were elevated. Gonioscopy revealed complete angle closure in the left eye and complete to partial closure in the right eye. Through existing peripheral iridotomies the anterior capsules were seen pressed up against the iris of both eyes. A diagnosis of angle-closure glaucoma was made, medications were started to reduce the elevated intraocular pressure and systemic antihistamine to counter the allergic reaction. She was hospitalised for further management. A follow-up at 2 years revealed her visual acuities and IOP had remained normal.

Arabidopsis plants deficient in plastidial glyceraldehyde-3-phosphate dehydrogenase show alterations in abscisic acid (ABA) signal transduction: interaction between ABA and primary metabolism

PubMed Central

Muñoz-Bertomeu, Jesús; Bermúdez, María Angeles; Segura, Juan; Ros, Roc

2011-01-01

Abscisic acid (ABA) controls plant development and regulates plant responses to environmental stresses. A role for ABA in sugar regulation of plant development has also been well documented although the molecular mechanisms connecting the hormone with sugar signal transduction pathways are not well understood. In this work it is shown that Arabidopsis thaliana mutants deficient in plastidial glycolytic glyceraldehyde-3-phosphate dehydrogenase (gapcp1gapcp2) are ABA insensitive in growth, stomatal closure, and germination assays. The ABA levels of gapcp1gapcp2 were normal, suggesting that the ABA signal transduction pathway is impaired in the mutants. ABA modified gapcp1gapcp2 gene expression, but the mutant response to the hormone differed from that observed in wild-type plants. The gene expression of the transcription factor ABI4, involved in both sugar and ABA signalling, was altered in gapcp1gapcp2, suggesting that their ABA insensitivity is mediated, at least partially, through this transcriptional regulator. Serine supplementation was able partly to restore the ABA sensitivity of gapcp1gapcp2, indicating that amino acid homeostasis and/or serine metabolism may also be important determinants in the connections of ABA with primary metabolism. Overall, these studies provide new insights into the links between plant primary metabolism and ABA signalling, and demonstrate the importance of plastidial glycolytic glyceraldehyde-3-phosphate dehydrogenase in these interactions. PMID:21068209

Increase in forest water-use efficiency as atmospheric carbon dioxide concentrations rise.

PubMed

Keenan, Trevor F; Hollinger, David Y; Bohrer, Gil; Dragoni, Danilo; Munger, J William; Schmid, Hans Peter; Richardson, Andrew D

2013-07-18

Terrestrial plants remove CO2 from the atmosphere through photosynthesis, a process that is accompanied by the loss of water vapour from leaves. The ratio of water loss to carbon gain, or water-use efficiency, is a key characteristic of ecosystem function that is central to the global cycles of water, energy and carbon. Here we analyse direct, long-term measurements of whole-ecosystem carbon and water exchange. We find a substantial increase in water-use efficiency in temperate and boreal forests of the Northern Hemisphere over the past two decades. We systematically assess various competing hypotheses to explain this trend, and find that the observed increase is most consistent with a strong CO2 fertilization effect. The results suggest a partial closure of stomata-small pores on the leaf surface that regulate gas exchange-to maintain a near-constant concentration of CO2 inside the leaf even under continually increasing atmospheric CO2 levels. The observed increase in forest water-use efficiency is larger than that predicted by existing theory and 13 terrestrial biosphere models. The increase is associated with trends of increasing ecosystem-level photosynthesis and net carbon uptake, and decreasing evapotranspiration. Our findings suggest a shift in the carbon- and water-based economics of terrestrial vegetation, which may require a reassessment of the role of stomatal control in regulating interactions between forests and climate change, and a re-evaluation of coupled vegetation-climate models.

Mechanistic modelling of Middle Eocene atmospheric carbon dioxide using fossil plant material

NASA Astrophysics Data System (ADS)

Grein, Michaela; Roth-Nebelsick, Anita; Wilde, Volker; Konrad, Wilfried; Utescher, Torsten

2010-05-01

Various proxies (such as pedogenic carbonates, boron isotopes or phytoplankton) and geochemical models were applied in order to reconstruct palaeoatmospheric carbon dioxide, partially providing conflicting results. Another promising proxy is the frequency of stomata (pores on the leaf surface used for gaseous exchange). In this project, fossil plant material from the Messel Pit (Hesse, Germany) is used to reconstruct atmospheric carbon dioxide concentration in the Middle Eocene by analyzing stomatal density. We applied the novel mechanistic-theoretical approach of Konrad et al. (2008) which provides a quantitative derivation of the stomatal density response (number of stomata per leaf area) to varying atmospheric carbon dioxide concentration. The model couples 1) C3-photosynthesis, 2) the process of diffusion and 3) an optimisation principle providing maximum photosynthesis (via carbon dioxide uptake) and minimum water loss (via stomatal transpiration). These three sub-models also include data of the palaeoenvironment (temperature, water availability, wind velocity, atmospheric humidity, precipitation) and anatomy of leaf and stoma (depth, length and width of stomatal porus, thickness of assimilation tissue, leaf length). In order to calculate curves of stomatal density as a function of atmospheric carbon dioxide concentration, various biochemical parameters have to be borrowed from extant representatives. The necessary palaeoclimate data are reconstructed from the whole Messel flora using Leaf Margin Analysis (LMA) and the Coexistence Approach (CA). In order to obtain a significant result, we selected three species from which a large number of well-preserved leaves is available (at least 20 leaves per species). Palaeoclimate calculations for the Middle Eocene Messel Pit indicate a warm and humid climate with mean annual temperature of approximately 22°C, up to 2540 mm mean annual precipitation and the absence of extended periods of drought. Mean relative air humidity was probably rather high, up to 77%. The combined results of the three selected plant taxa indicate values for atmospheric carbon dioxide concentration between 700 and 1100 ppm (probably about 900 ppm). Reference: Konrad, W., Roth-Nebelsick, A., Grein, M. (2008). Modelling of stomatal density response to atmospheric CO2. Journal of Theoretical Biology 253(4): 638-658.

Cleft Palate Fistula Closure Utilizing Acellular Dermal Matrix.

PubMed

Emodi, Omri; Ginini, Jiriys George; van Aalst, John A; Shilo, Dekel; Naddaf, Raja; Aizenbud, Dror; Rachmiel, Adi

2018-03-01

Fistulas represent failure of cleft palate repair. Secondary and tertiary fistula repair is challenging, with high recurrence rates. In the present retrospective study, we review the efficacy of using acellular dermal matrix as an interposition layer for cleft palate fistula closure in 20 consecutive patients between 2013 and 2016. Complete fistula closure was obtained in 16 patients; 1 patient had asymptomatic recurrent fistula; 2 patients had partial closure with reduction of fistula size and minimal nasal regurgitation; 1 patient developed a recurrent fistula without changes in symptoms (success rate of 85%). We conclude that utilizing acellular dermal matrix for cleft palate fistula repair is safe and simple with a high success rate.

Cleft Palate Fistula Closure Utilizing Acellular Dermal Matrix

PubMed Central

Emodi, Omri; van Aalst, John A.; Shilo, Dekel; Naddaf, Raja; Aizenbud, Dror; Rachmiel, Adi

2018-01-01

Summary: Fistulas represent failure of cleft palate repair. Secondary and tertiary fistula repair is challenging, with high recurrence rates. In the present retrospective study, we review the efficacy of using acellular dermal matrix as an interposition layer for cleft palate fistula closure in 20 consecutive patients between 2013 and 2016. Complete fistula closure was obtained in 16 patients; 1 patient had asymptomatic recurrent fistula; 2 patients had partial closure with reduction of fistula size and minimal nasal regurgitation; 1 patient developed a recurrent fistula without changes in symptoms (success rate of 85%). We conclude that utilizing acellular dermal matrix for cleft palate fistula repair is safe and simple with a high success rate. PMID:29707449

Increasing atmospheric humidity and CO 2 concentration alleviate forest mortality risk

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yanlan; Parolari, Anthony J.; Kumar, Mukesh

Climate-induced forest mortality is being increasingly observed throughout the globe. Alarmingly, it is expected to exacerbate under climate change due to shifting precipitation patterns and rising air temperature. However, the impact of concomitant changes in atmospheric humidity and CO 2 concentration through their influence on stomatal kinetics remains a subject of debate and inquiry. By using a dynamic soil–plant–atmosphere model, mortality risks associated with hydraulic failure and stomatal closure for 13 temperate and tropical forest biomes across the globe are analyzed. The mortality risk is evaluated in response to both individual and combined changes in precipitation amounts and their seasonalmore » distribution, mean air temperature, specific humidity, and atmospheric CO 2 concentration. Model results show that the risk is predicted to significantly increase due to changes in precipitation and air temperature regime for the period 2050–2069. However, this increase may largely get alleviated by concurrent increases in atmospheric specific humidity and CO 2 concentration. The increase in mortality risk is expected to be higher for needleleaf forests than for broadleaf forests, as a result of disparity in hydraulic traits. These findings will further facilitate decisions about intervention and management of different forest types under changing climate.« less

Comparison of infrared canopy temperature in a rubber plantation and tropical rain forest.

PubMed

Song, Qing-Hai; Deng, Yun; Zhang, Yi -Ping; Deng, Xiao-Bao; Lin, You-Xing; Zhou, Li-Guo; Fei, Xue-Hai; Sha, Li-Qing; Liu, Yun-Tong; Zhou, Wen-Jun; Gao, Jin-Bo

2017-10-01

Canopy temperature is a result of the canopy energy balance and is driven by climate conditions, plant architecture, and plant-controlled transpiration. Here, we evaluated canopy temperature in a rubber plantation (RP) and tropical rainforest (TR) in Xishuangbanna, southwestern China. An infrared temperature sensor was installed at each site to measure canopy temperature. In the dry season, the maximum differences (T c  - T a ) between canopy temperature (T c ) and air temperature (T a ) in the RP and TR were 2.6 and 0.1 K, respectively. In the rainy season, the maximum (T c  - T a ) values in the RP and TR were 1.0 and -1.1 K, respectively. There were consistent differences between the two forests, with the RP having higher (T c  - T a ) than the TR throughout the entire year. Infrared measurements of T c can be used to calculate canopy stomatal conductance in both forests. The difference in (T c  - T a ) at three g c levels with increasing direct radiation in the RP was larger than in the TR, indicating that change in (T c  - T a ) in the RP was relatively sensitive to the degree of stomatal closure.

Increasing atmospheric humidity and CO 2 concentration alleviate forest mortality risk

DOE PAGES

Liu, Yanlan; Parolari, Anthony J.; Kumar, Mukesh; ...

2017-08-28

Climate-induced forest mortality is being increasingly observed throughout the globe. Alarmingly, it is expected to exacerbate under climate change due to shifting precipitation patterns and rising air temperature. However, the impact of concomitant changes in atmospheric humidity and CO 2 concentration through their influence on stomatal kinetics remains a subject of debate and inquiry. By using a dynamic soil–plant–atmosphere model, mortality risks associated with hydraulic failure and stomatal closure for 13 temperate and tropical forest biomes across the globe are analyzed. The mortality risk is evaluated in response to both individual and combined changes in precipitation amounts and their seasonalmore » distribution, mean air temperature, specific humidity, and atmospheric CO 2 concentration. Model results show that the risk is predicted to significantly increase due to changes in precipitation and air temperature regime for the period 2050–2069. However, this increase may largely get alleviated by concurrent increases in atmospheric specific humidity and CO 2 concentration. The increase in mortality risk is expected to be higher for needleleaf forests than for broadleaf forests, as a result of disparity in hydraulic traits. These findings will further facilitate decisions about intervention and management of different forest types under changing climate.« less

Large-Scale Phenomics Identifies Primary and Fine-Tuning Roles for CRKs in Responses Related to Oxidative Stress

PubMed Central

Rayapuram, Channabasavangowda; Idänheimo, Niina; Hunter, Kerri; Kimura, Sachie; Merilo, Ebe; Vaattovaara, Aleksia; Oracz, Krystyna; Kaufholdt, David; Pallon, Andres; Anggoro, Damar Tri; Glów, Dawid; Lowe, Jennifer; Zhou, Ji; Mohammadi, Omid; Puukko, Tuomas; Albert, Andreas; Lang, Hans; Ernst, Dieter; Kollist, Hannes; Brosché, Mikael; Durner, Jörg; Borst, Jan Willem; Collinge, David B.; Karpiński, Stanisław; Lyngkjær, Michael F.; Robatzek, Silke; Wrzaczek, Michael; Kangasjärvi, Jaakko

2015-01-01

Cysteine-rich receptor-like kinases (CRKs) are transmembrane proteins characterized by the presence of two domains of unknown function 26 (DUF26) in their ectodomain. The CRKs form one of the largest groups of receptor-like protein kinases in plants, but their biological functions have so far remained largely uncharacterized. We conducted a large-scale phenotyping approach of a nearly complete crk T-DNA insertion line collection showing that CRKs control important aspects of plant development and stress adaptation in response to biotic and abiotic stimuli in a non-redundant fashion. In particular, the analysis of reactive oxygen species (ROS)-related stress responses, such as regulation of the stomatal aperture, suggests that CRKs participate in ROS/redox signalling and sensing. CRKs play general and fine-tuning roles in the regulation of stomatal closure induced by microbial and abiotic cues. Despite their great number and high similarity, large-scale phenotyping identified specific functions in diverse processes for many CRKs and indicated that CRK2 and CRK5 play predominant roles in growth regulation and stress adaptation, respectively. As a whole, the CRKs contribute to specificity in ROS signalling. Individual CRKs control distinct responses in an antagonistic fashion suggesting future potential for using CRKs in genetic approaches to improve plant performance and stress tolerance. PMID:26197346

Turning over a new 'leaf': multiple functional significances of leaves versus phyllodes in Hawaiian Acacia koa.

PubMed

Pasquet-Kok, Jessica; Creese, Christine; Sack, Lawren

2010-12-01

Hawaiian endemic tree Acacia koa is a model for heteroblasty with bipinnately compound leaves and phyllodes. Previous studies suggested three hypotheses for their functional differentiation: an advantage of leaves for early growth or shade tolerance, and an advantage of phyllodes for drought tolerance. We tested the ability of these hypotheses to explain differences between leaf types for potted plants in 104 physiological and morphological traits, including gas exchange, structure and composition, hydraulic conductance, and responses to varying light, intercellular CO(2) , vapour pressure deficit (VPD) and drought. Leaf types were similar in numerous traits including stomatal pore area per leaf area, leaf area-based gas exchange rates and cuticular conductance. Each hypothesis was directly supported by key differences in function. Leaves had higher mass-based gas exchange rates, while the water storage tissue in phyllodes contributed to greater capacitance per area; phyllodes also showed stronger stomatal closure at high VPD, and higher maximum hydraulic conductance per area, with stronger decline during desiccation and recovery with rehydration. While no single hypothesis completely explained the differences between leaf types, together the three hypotheses explained 91% of differences. These findings indicate that the heteroblasty confers multiple benefits, realized across different developmental stages and environmental contexts. © 2010 Blackwell Publishing Ltd.

Fine Mapping of Carbon Assimilation Rate 8, a Quantitative Trait Locus for Flag Leaf Nitrogen Content, Stomatal Conductance and Photosynthesis in Rice

PubMed Central

Adachi, Shunsuke; Yoshikawa, Kazuaki; Yamanouchi, Utako; Tanabata, Takanari; Sun, Jian; Ookawa, Taiichiro; Yamamoto, Toshio; Sage, Rowan F.; Hirasawa, Tadashi; Yonemaru, Junichi

2017-01-01

Increasing the rate of leaf photosynthesis is one important approach for increasing grain yield in rice (Oryza sativa). Exploiting the natural variation in CO2 assimilation rate (A) between rice cultivars using quantitative genetics is one promising means to identify genes contributing to higher photosynthesis. In this study, we determined precise location of Carbon Assimilation Rate 8 (CAR8) by crossing a high-yielding indica cultivar with a Japanese commercial cultivar. Fine mapping suggested that CAR8 encodes a putative Heme Activator Protein 3 (OsHAP3) subunit of a CCAAT-box-binding transcription factor called OsHAP3H. Sequencing analysis revealed that the indica allele of CAR8 has a 1-bp deletion at 322 bp from the start codon, resulting in a truncated protein of 125 amino acids. In addition, CAR8 is identical to DTH8/Ghd8/LHD1, which was reported to control rice flowering date. The increase of A is largely due to an increase of RuBP regeneration rate via increased leaf nitrogen content, and partially explained by reduced stomatal limitation via increased stomatal conductance relative to A. This allele also increases hydraulic conductivity, which would promote higher stomatal conductance. This indicates that CAR8 affects multiple physiological aspects relating to photosynthesis. The detailed analysis of molecular functions of CAR8 would help to understand the association between photosynthesis and flowering and demonstrate specific genetic mechanisms that can be exploited to improve photosynthesis in rice and potentially other crops. PMID:28197156

Two-Point Turbulence Closure Applied to Variable Resolution Modeling

NASA Technical Reports Server (NTRS)

Girimaji, Sharath S.; Rubinstein, Robert

2011-01-01

Variable resolution methods have become frontline CFD tools, but in order to take full advantage of this promising new technology, more formal theoretical development is desirable. Two general classes of variable resolution methods can be identified: hybrid or zonal methods in which RANS and LES models are solved in different flow regions, and bridging or seamless models which interpolate smoothly between RANS and LES. This paper considers the formulation of bridging methods using methods of two-point closure theory. The fundamental problem is to derive a subgrid two-equation model. We compare and reconcile two different approaches to this goal: the Partially Integrated Transport Model, and the Partially Averaged Navier-Stokes method.

Sensitivity of Breast Tumors to Oncolytic Viruses

DTIC Science & Technology

2005-08-01

reproductions will be in black and white. 14. ABSTRACT The goal of this project is to develop novel therapies for breast cancer based on the oncolytic...effect than breast cancer cells. However, in syngeneic breast cancer system in vivo, rM51R-M virus is only partially effective at killing breast tumors...aggressive tumors that are resistant to more conventional therapies. 15. SUBJECT TERMS Vesicular stomatitis virus, interleukin 12, breast cancer

Seasonal changes in Cyclobalanopsis glauca transpiration and canopy stomatal conductance and their dependence on subterranean water and climatic factors in rocky karst terrain

NASA Astrophysics Data System (ADS)

Huang, Yuqing; Li, Xiankun; Zhang, Zhongfeng; He, Chengxin; Zhao, Ping; You, Yeming; Mo, Ling

2011-05-01

SummaryThe presence of forest on south China karst is presumed to increase perennial epikarst spring flow, partly because there is adequate storage in bedrock fractures underlying the shallow soil in the forest. If true, transpiration of the ecosystem would not be strongly reduced by temperate drought if trees develop deep roots to reach the perched epikarst water. Therefore, in karst ecosystem the epikarst-soil-plant-atmosphere continuum (ESPAC) would be different from the SPAC in non-karst system. We measured transpiration and canopy conductance from a Cyclobalanopsis glauca (syn. Quercus glauca) stand on a rocky hill slope in South China during 2006-2007 by using the Granier's sap-flow method. Annual stand transpiration (836 mm y -1) accounted for 48.7% of the rainfall during the experimental year. Per month, daily stand transpiration ( E c) maximums varied between 2.1 mm d -1 in January (cool season) to 5.1 mm d -1 in July (hot season). In the driest months, September and October, E c of C. glauca was still high with maximum E c 3.82 mm d -1 and 2.96 mm d -1 respectively. Solar radiation ( PAR), vapor pressure deficiency ( VPD), and air temperature were simple influences on transpiration of C. glauca, which contributed to a quadratic power model, while soil water content ( SWC) moisture influence on transpiration was complicated, which SWC influenced E c greatly under higher VPD, but did not influence E c under low VPD. High stomatal openness occurred in C. glauca in the early morning and declined throughout the day. The relation coefficient between canopy stomatal conductance ( G c) and E c was high when VPD was more than 1.0 kPa, moderate when 0.5 kPa < VPD < 1.0 kPa, and low with VPD of less than 0.5 kPa. Under high VPD, stomatal control of transpiration is high. The pattern of seasonal change of transpiration and canopy stomatal conductance of the plant in karst regions is different from that in non-karst regions, with the stand transpiration and canopy stomatal conductance being high even during the dry season in the karst region because karst plants obtain water partially from the epikarst. With high stand transpiration and canopy stomatal conductance, karst vegetation is presumed to be the most important "pathway" for ESPAC.

Finders keepers, losers weepers - drought as a modifier of competition between European beech and Norway spruce -

NASA Astrophysics Data System (ADS)

Goisser, Michael; Blanck, Christian; Geppert, Uwe; Häberle, Karl-Heinz; Matyssek, Rainer; Grams, Thorsten E. E.

2016-04-01

Mixed stands of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) frequently reflect over-yielding, when compared to respective monospecific stands. Over-yielding is attributed to enhanced resource uptake efficiency through niche complementarity alleviating species competition. Under climate change, however, with severe and frequent summer drought, water limitation may become crucial in modifying the competitive interaction between neighboring beech and spruce trees. In view of the demands by silvicultural practice, basic knowledge from experimental field work about competitive versus facilitative interaction in maturing mixed beech-spruce forests is scarce. To this end, we investigate species-specific drought response including underlying mechanisms of species interaction in a maturing group-wise mixed beech-spruce forest, amongst 60 and 53 adult trees of beech and spruce, respectively (spruce 65 ± 2, beech 85 ± 4 years old). Severe and repeated experimental drought is being induced over several years through a stand-scale approach of rain throughfall exclusion (Kranzberg Forest Roof Experiment, KROOF). The experimental design comprises 6 roofed (E, automated, closing only during rain) and 6 control (C) plots with a total area of almost 1800 square meters. In 2015 minimum predawn potentials of -2.16 MPa and -2.26 MPa were reached in E for beech and spruce respectively. At the leaf level, spruce displayed high drought susceptibility reflected by a distinct decrease in both stomatal conductance and net CO2 uptake rate by more than 80% each, suggesting isohydric response. Beech rather displayed anisohydry indicated by less pronounced yet significant reduction of stomatal conductance and net CO2 uptake rate by more than 55% and 45%, respectively. Under the C regime, a negative species interaction effect on stomatal conductance was found in beech, contrasting with a positive effect in spruce. However, drought reversed the effect of species interaction on stomatal conductance, suggesting competition release in beech and by contrast, a shift from facilitation to competition in spruce, if both species grew in mixture. Based on fine root distribution and soil moisture assessments, we interpret this reversed interaction effect as a consequence of different spatio-temporal patterns of soil water use in combination with enhanced root stratification between neighboring beech and spruce trees. Under humid climate conditions (i.e. with only short drought) the rather conservative strategy of spruce (isohydric response, root dominance in upper soil) appears to be advantageous, facilitating pre-emption of nutrients from litter mineralization and water from precipitation. During extended periods of drought, however, shallow rooting and early stomatal closure limits the accessibility to deep soil water and, hence, photosynthetic carbon assimilation, eventually constraining competitiveness of spruce. Beech rather benefits from reduced water consumption of its drought stressed competitor spruce. Regarding stomatal conductance, positive effects of beech-spruce interaction are overridden under extended periods of drought.

Physiological and morphological response patterns of Populus deltoides to alluvial groundwater

USGS Publications Warehouse

Cooper, D.J.; D'Amico, D.R.; Scott, M.L.

2003-01-01

We examined the physiological and morphological response patterns of plains cottonwood [Populus deltoides subsp. monilifera (Aiton) Eck.] to acute water stress imposed by groundwater pumping. Between 3 and 27 July 1996, four large pumps were used to withdraw alluvial groundwater from a cottonwood forest along the South Platte River, near Denver, Colorado, USA. The study was designed as a stand-level, split-plot experiment with factorial treatments including two soil types (a gravel soil and a loam topsoil over gravel), two water table drawdown depths (∼0.5 m and >1.0 m), and one water table control (no drawdown) per soil type. Measurements of water table depth, soil water potential (Ψs), predawn and midday shoot water potential (Ψpd and Ψmd), and D/H (deuterium/hydrogen) ratios of different water sources were made in each of six 600-m2 plots prior to, during, and immediately following pumping. Two additional plots were established and measured to examine the extent to which surface irrigation could be used to mitigate the effects of deep drawdown on P. deltoides for each soil type. Recovery of tree water status following pumping was evaluated by measuring stomatal conductance (gs) and xylem water potential (Ψxp) on approximately hourly time steps from before dawn to mid-afternoon on 11 August 1996 in watered and unwatered, deep-drawdown plots on gravel soils. P. deltoides responded to abrupt alluvial water table decline with decreased shoot water potential followed by leaf mortality. Ψpd and percent leaf loss were significantly related to the magnitude of water table declines. The onset and course of these responses were influenced by short-term variability in surface and ground water levels, acting in concert with physiological and morphological adjustments. Decreases in Ψpd corresponded with increases in Ψmd, suggesting shoot water status improved in response to stomatal closure and crown dieback. Crown dieback caused by xylem cavitation likely occurred when Ψpd reached −0.4 to −0.8 MPa. The application of surface irrigation allowed trees to maintain favorable water status with little or no apparent cavitation, even in deep-drawdown plots. Two weeks after the partial canopy dieback and cessation of pumping, gs and Ψxp measurements indicated that water stress persisted in unwatered P. deltoides in deep-drawdown plots.

Partial Root-Zone Drying of Olive (Olea europaea var. 'Chetoui') Induces Reduced Yield under Field Conditions.

PubMed

Dbara, Soumaya; Haworth, Matthew; Emiliani, Giovani; Ben Mimoun, Mehdi; Gómez-Cadenas, Aurelio; Centritto, Mauro

2016-01-01

The productivity of olive trees in arid and semi-arid environments is closely linked to irrigation. It is necessary to improve the efficiency of irrigation techniques to optimise the amount of olive fruit produced in relation to the volume of water used. Partial root-zone drying (PRD) is a water saving irrigation technique that theoretically allows the production of a root-to-shoot signal that modifies the physiology of the above-ground parts of the plant; specifically reducing stomatal conductance (gs) and improving water use efficiency (WUE). Partial root-zone drying has been successfully applied under field conditions to woody and non-woody crops; yet the few previous trials with olive trees have produced contrasting results. Thirty year-old olive trees (Olea europaea 'var. Chetoui') in a Tunisian grove were exposed to four treatments from May to October for three-years: 'control' plants received 100% of the potential evapotranspirative demand (ETc) applied to the whole root-zone; 'PRD100' were supplied with an identical volume of water to the control plants alternated between halves of the root-zone every ten-days; 'PRD50' were given 50% of ETc to half of the root-system, and; 'rain-fed' plants received no supplementary irrigation. Allowing part of the root-zone to dry resulted in reduced vegetative growth and lower yield: PRD100 decreased yield by ~47% during productive years. During the less productive years of the alternate bearing cycle, irrigation had no effect on yield; this suggests that withholding of water during 'off-years' may enhance the effectiveness of irrigation over a two-year cycle. The amount and quality of oil within the olive fruit was unaffected by the irrigation treatment. Photosynthesis declined in the PRD50 and rain-fed trees due to greater diffusive limitations and reduced biochemical uptake of CO2. Stomatal conductance and the foliar concentration of abscisic acid (ABA) were not altered by PRD100 irrigation, which may indicate the absence of a hormonal root-to-shoot signal. Rain-fed and PRD50 treatments induced increased stem water potential and increased foliar concentrations of ABA, proline and soluble sugars. The stomata of the olive trees were relatively insensitive to super-ambient increases in [CO2] and higher [ABA]. These characteristics of 'hydro-passive' stomatal behaviour indicate that the 'Chetoui' variety of olive tree used in this study lacks the physiological responses required for the successful exploitation of PRD techniques to increase yield and water productivity. Alternative irrigation techniques such as partial deficit irrigation may be more suitable for 'Chetoui' olive production.

Implicit memory for novel figure-ground displays includes a history of cross-border competition.

PubMed

Peterson, Mary A; Lampignano, Daniel W

2003-08-01

When configural cues specify that a figure lies on opposite sides of a repeated border in prime andprobe shapes, probe latencies are longer than when prime and probe borders are unrelated. Do such results reflect negative priming for the shape of the prime ground or cross-border competition from figure memory? The present study tested these alternatives by adding partial closure as a competing cue and reducing the similarity between the prime ground and the shape of the probe. Results supported the cross-border competition interpretation. Additional findings were that partial closure is a configural cue and that response effects can emerge from the potential shape on the ground side of a border. One prior experience was sufficient for these effects.

Effects of stomatal development on stomatal conductance and on stomatal limitation of photosynthesis in Syringa oblata and Euonymus japonicus Thunb.

PubMed

Wu, Bing-Jie; Chow, Wah Soon; Liu, Yu-Jun; Shi, Lei; Jiang, Chuang-Dao

2014-12-01

During leaf development, the increase in stomatal conductance cannot meet photosynthetic demand for CO2, thus leading to stomatal limitation of photosynthesis (Ls). Considering the crucial influences of stomatal development on stomatal conductance, we speculated whether stomatal development limits photosynthesis to some extent. To test this hypothesis, stomatal development, stomatal conductance and photosynthesis were carefully studied in both Syringa oblata (normal greening species) and Euonymus japonicus Thunb (delayed greening species). Our results show that the size of stomata increased gradually with leaf expansion, resulting in increased stomatal conductance up to the time of full leaf expansion. During this process, photosynthesis also increased steadily. Compared to that in S. oblata, the development of chloroplasts in E. japonicus Thunb was obviously delayed, leading to a delay in the improvement of photosynthetic capacity. Further analysis revealed that before full leaf expansion, stomatal limitation increased rapidly in both S. oblata and E. japonicus Thunb; after full leaf expansion, stomatal limitation continually increased in E. japonicus Thunb. Accordingly, we suggested that the enhancement of photosynthetic capacity is the main factor leading to stomatal limitation during leaf development but that stomatal development can alleviate stomatal limitation with the increase of photosynthesis by controlling gas exchange. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Development of tolerance of egg plant (Solanum melangena L.) to field application of dimethoate.

PubMed

Khillar, R; Acharya, S; Mohapatra, P K

2010-07-01

Dimethoate, at field concentration (1.419 mg g(-1) fr wt), caused inhibition of photosynthesis, transpiration and stomatal conductance of Solanum melangena L. on first treatment but subsequent treatments caused adaptation and recovery of these parameters. The variable fluorescence (F(v)), dissipation (DI(0)/RC), 2 ms relative variable fluorescence (V(j)), net rate of PS II closure (M(0)), and maximum trapping rate of active PS II (TR(0)/RC) increased initially but reduced to the control value with repetition of treatment. However, fluorescence yield (TR(0)/Abs), electron transport probability (ET(0)/TR(0)) and activity of RC (ET(0)/RC) increased with each treatment. With each subsequent treatment there was enhancement of activities of esterases and decrease of insecticide content of leaves.

A limited role for carbonic anhydrase in C 4 photosynthesis as revealed by a ca1ca2 double mutant in maize.

DOE PAGES

Studer, Anthony J.; Gandin, Anthony; Kolbe, Allison R.; ...

2014-04-04

Carbonic anhydrase (CA) catalyzes the first biochemical step of the carbon concentrating mechanism of C 4 plants, and in C 4 monocots, it has been suggested that CA activity is near limiting for photosynthesis. Here, we test this hypothesis through the characterization of transposon induced mutant alleles of Ca1 and Ca2 in Zea mays. In addition, these two isoforms account for more than 85% of the CA transcript pool. A significant change in isotopic discrimination is observed in mutant plants, which have as little as 3% of wild-type CA activity, but surprisingly, photosynthesis is not reduced under current or elevatedmore » pCO 2. However, growth and rates of photosynthesis under sub-ambient pCO 2 are significantly impaired in the mutants. These findings suggest, that while CA is not limiting for C 4 photosynthesis in Z. mays at current pCO 2, it likely maintains high rates of photosynthesis when CO 2 availability is reduced. Current atmospheric CO 2 levels now exceed 400 ppm (~40.53 Pa) and contrast the low CO 2 partial pressure (pCO 2) conditions under which C 4 plants expanded their range ~10 million years ago when the global atmospheric CO 2 was below 300 ppm (~30.40 Pa). Thus, as CO 2 levels continue to rise, selective pressures for high levels of CA may be limited to arid climates where stomatal closure reduces CO 2 availability to the leaf.« less

Stomata open at night in pole-sized and mature ponderosa pine: implications for O3 exposure metrics.

PubMed

Grulke, N E; Alonso, R; Nguyen, T; Cascio, C; Dobrowolski, W

2004-09-01

Ponderosa pine (Pinus ponderosa Dougl. ex Laws.) is widely distributed in the western USA. We report the lack of stomatal closure at night in early summer for ponderosa pine at two of three sites investigated. Trees at a third site with lower nitrogen dioxide and nitric acid exposure, but greater drought stress, had slightly open stomata at night in early summer but closed stomata at night for the rest of the summer. The three sites had similar background ozone exposure during the summer of measurement (2001). Nighttime stomatal conductance (gs) ranged from one tenth to one fifth that of maximum daytime values. In general, pole-sized trees (< 40 years old) had greater nighttime gs than mature trees (> 250 years old). In late summer, nighttime gs was low (< 3.0 mmol H2O m(-2) s(-1)) for both tree size classes at all sites. Measurable nighttime gs has also been reported in other conifers, but the values we observed were higher. In June, nighttime ozone (O3) uptake accounted for 9, 5 and 3% of the total daily O3 uptake of pole-sized trees from west to east across the San Bernardino Mountains. In late summer, O3 uptake at night was < 2% of diel uptake at all sites. Nocturnal O3 uptake may contribute to greater oxidant injury development, especially in pole-sized trees in early summer.

Intensified Vegetation Water Use due to Soil Calcium Leaching under Acid Deposition

NASA Astrophysics Data System (ADS)

Lanning, M.; Wang, L.; Scanlon, T. M.; Vadeboncoeur, M. A.; Adams, M. B.; Epstein, H. E.; Druckenbrod, D.

2017-12-01

Despite the important role vegetation plays in the global water cycle, the exact controls of vegetation water use, especially the role of soil biogeochemistry, remain elusive. Nitrate and sulfate deposition from fossil fuel burning has caused significant soil acidification, leading to the leaching of soil base cations. From a physiological perspective, plants require various soil cations as signaling and regulatory ions as well as integral parts of structural molecules; a depletion of soil cations can cause reduced productivity and abnormal responses to environmental change. A deficiency in calcium could also potentially prolong stomatal opening, leading to increased transpiration until enough calcium had been acquired to stimulate stomatal closure. Based on the plant physiology and the nature of acidic deposition, we hypothesize that depletion of the soil calcium supply, induced by acid deposition, would intensify vegetation water use at the watershed scale. We tested this hypothesis by analyzing a long-term and unique data set (1989-2012) of soil lysimeter data along with stream flow and evapotranspiration data at the Fernow Experimental Forest. We show that depletion of soil calcium by acid deposition can intensify vegetation water use ( 10% increase in evapotranspiration and depletion in soil water) for the first time. These results are critical to understanding future water availability, biogeochemical cycles, and surficial energy flux and may help reduce uncertainties in terrestrial biosphere models.

Paraheliotropism can protect water-stressed bean (Phaseolus vulgaris L.) plants against photoinhibition.

PubMed

Pastenes, Claudio; Porter, Victor; Baginsky, Cecilia; Horton, Peter; González, Javiera

2004-12-01

In order to estimate the importance of leaf movements on photosynthesis in well-watered and water-stressed field grown bean cultivars (Arroz Tuscola (AT), Orfeo INIA (OI), Bayos Titan (BT), and Hallados Dorado (HD)), CO2 assimilation, leaf temperature, and capacity for the maximum quantum yield recovery, measured as Fv/Fm, were assessed. Leaf water potential was lower in water-stressed compared to control plants throughout the day. Water status determined a decrease in the CO2 assimilation and stomatal conductance as light intensity and temperature increased up to maximal intensities at midday. Both parameters were lower in stressed compared to control plants. Even though high light intensity and water-stress induced stomatal closure is regarded as a photoinhibitory condition, the recovery of variable to maximal fluorescence (Fv/Fm) after 30min of darkness was nearly constant in both water regimes. In fact, higher values were observed in OI and AT when under stress. Photochemical and non-photochemical fluorescence quenching resulted in minor changes during the day and were similar between watered and stressed plants. It is concluded that paraheliotropism, present in the four bean cultivars, efficiently protects stressed plants from photoinhibition in the field and helps maintain leaf temperatures far below the ambient temperatures, however, it may also be responsible for low CO2 assimilation rates in watered plants.

Transcript, protein and metabolite temporal dynamics in the CAM plant Agave

DOE PAGES

Abraham, Paul E.; Yin, Hengfu; Borland, Anne M.; ...

2016-11-21

Already a proven mechanism for drought resilience, crassulacean acid metabolism (CAM) is a specialized type of photosynthesis that maximizes water-use efficiency (WUE) via an inverse (compared to C 3 and C 4 photosynthesis-performing species) day/night pattern of stomatal closure/opening to shift CO 2 uptake to the night, when evapotranspiration rates are low. A systems-level understanding of temporal molecular and metabolic controls is needed to define the cellular behavior that underpins CAM. Here, we report high-resolution temporal behaviors of transcript, protein and metabolite abundances across a CAM diel cycle and, where applicable, compare those observations to the well-established C 3 modelmore » plant, Arabidopsis thaliana. A mechanistic finding that emerged is that CAM operates with a diel redox poise that is shifted relative to that in Arabidopsis thaliana. Moreover, we identified widespread rescheduled expression of genes associated with signal transduction mechanisms that regulate stomatal opening/closing. Controlled production and degradation of transcripts and proteins represents a timing mechanism by which to regulate cellular function, yet how this molecular timekeeping regulates CAM physiology remains unclear. In this paper, we provide new insights into complex post-transcriptional and -translational hierarchies that govern CAM in Agave. These data sets together provide a resource to inform efforts to engineer more water-use efficient CAM pathway traits into economically valuable C 3 crops.« less

Transcript, protein and metabolite temporal dynamics in the CAM plant Agave

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abraham, Paul E.; Yin, Hengfu; Borland, Anne M.

Already a proven mechanism for drought resilience, crassulacean acid metabolism (CAM) is a specialized type of photosynthesis that maximizes water-use efficiency (WUE) via an inverse (compared to C 3 and C 4 photosynthesis-performing species) day/night pattern of stomatal closure/opening to shift CO 2 uptake to the night, when evapotranspiration rates are low. A systems-level understanding of temporal molecular and metabolic controls is needed to define the cellular behavior that underpins CAM. Here, we report high-resolution temporal behaviors of transcript, protein and metabolite abundances across a CAM diel cycle and, where applicable, compare those observations to the well-established C 3 modelmore » plant, Arabidopsis thaliana. A mechanistic finding that emerged is that CAM operates with a diel redox poise that is shifted relative to that in Arabidopsis thaliana. Moreover, we identified widespread rescheduled expression of genes associated with signal transduction mechanisms that regulate stomatal opening/closing. Controlled production and degradation of transcripts and proteins represents a timing mechanism by which to regulate cellular function, yet how this molecular timekeeping regulates CAM physiology remains unclear. In this paper, we provide new insights into complex post-transcriptional and -translational hierarchies that govern CAM in Agave. These data sets together provide a resource to inform efforts to engineer more water-use efficient CAM pathway traits into economically valuable C 3 crops.« less

Photosynthetic capacity and water use efficiency in Ricinus communis (L.) under drought stress in semi-humid and semi-arid areas.

PubMed

Santos, Claudiana M Dos; Endres, Laurício; Ferreira, Vilma M; Silva, José V; Rolim, Eduardo V; Wanderley, Humberto C L

2017-01-01

Castor bean is one of the crops with potential to provide raw material for production of oils for biodiesel. This species possess adaptive mechanisms for maintaining the water status when subjected to drought stress. A better understanding these mechanisms under field conditions can unravel the survival strategies used by this species. This study aimed to compare the physiological adaptations of Ricinus communis (L.) in two regions with different climates, the semi-arid and semi-humid subject to water stress. The plants showed greater vapor pressure deficit during the driest hours of the day, which contributed to higher values of the leaf temperature and leaf transpiration, however, the VPD(leaf-air) had the greatest effect on plants in the semi-arid region. In both regions, between 12:00 p.m. and 2:00 p.m., the plants presented reduction in the rates of photosynthesis and intracellular CO2 concentration in response to stomatal closure. During the dry season in the semi-arid region, photoinhibition occurred in the leaves of castor bean between 12:00 p.m. and 2:00 p.m. These results suggest that castor bean plants possess compensatory mechanisms for drought tolerance, such as: higher stomatal control and maintenance of photosynthetic capacity, allowing the plant to survive well in soil with low water availability.

Nerium oleander indirect leaf photosynthesis and light harvesting reductions after clipping injury or Spodoptera eridania herbivory: high sensitivity to injury.

PubMed

Delaney, Kevin J

2012-04-01

Variable indirect photosynthetic rate (P(n)) responses occur on injured leaves after insect herbivory. It is important to understand factors that influence indirect P(n) reductions after injury. The current study examines the relationship between gas exchange and chlorophyll a fluorescence parameters with injury intensity (% single leaf tissue removal) from clipping or Spodoptera eridania Stoll (Noctuidae) herbivory on Nerium oleander L. (Apocynaceae). Two experiments showed intercellular [CO(2)] increases but P(n) and stomatal conductance reductions with increasing injury intensity, suggesting non-stomatal P(n) limitation. Also, P(n) recovery was incomplete at 3d post-injury. This is the first report of a negative exponential P(n) impairment function with leaf injury intensity to suggest high N. oleander leaf sensitivity to indirect P(n) impairment. Negative linear functions occurred between most other gas exchange and chlorophyll a fluorescence parameters with injury intensity. The degree of light harvesting impairment increased with injury intensity via lower (1) photochemical efficiency indicated lower energy transfer efficiency from reaction centers to PSII, (2) photochemical quenching indicated reaction center closure, and (3) electron transport rates indicated less energy traveling through PSII. Future studies can examine additional mechanisms (mesophyll conductance, carbon fixation, and cardenolide induction) to cause N. oleander indirect leaf P(n) reductions after injury. Published by Elsevier Ireland Ltd.

Blumeria graminis interactions with barley conditioned by different single R genes demonstrate a temporal and spatial relationship between stomatal dysfunction and cell death.

PubMed

Prats, Elena; Gay, Alan P; Roberts, Peter C; Thomas, Barry J; Sanderson, Ruth; Paveley, Neil; Lyngkjaer, Michael F; Carver, Tim L W; Mur, Luis A J

2010-01-01

Hypersensitive response (HR) against Blumeria graminis f. sp. hordei infection in barley (Hordeum vulgare) was associated with stomata "lock-up" leading to increased leaf water conductance (g(l)). Unique spatio-temporal patterns of HR formation occurred in barley with Mla1, Mla3, or MlLa R genes challenged with B. graminis f. sp. hordei. With Mla1, a rapid HR, limited to epidermal cells, arrested fungal growth before colonies initiated secondary attacks. With Mla3, mesophyll HR preceded that in epidermal cells whose initial survival supported secondary infections. With MlLa, mesophyll survived and not all attacked epidermal cells died immediately, allowing colony growth and secondary infection until arrested. Isolines with Mla1, Mla3, or MlLa genes inoculated with B. graminis f. sp. hordei ranging from 1 to 100 conidia mm(2) showed abnormally high g(l) during dark periods whose timing and extent correlated with those of each HR. Each isoline showed increased dark g(l) with the nonpathogen B. graminis f. sp. avenae which caused a single epidermal cell HR. Guard cell autofluorescence was seen only after drying of epidermal strips and closure of stomata suggesting that locked open stomata were viable. The data link stomatal lock-up to HR associated cell death and has implications for strategies for selecting disease resistant genotypes.

Uptake, Distribution, and Transformation of CuO NPs in a Floating Plant Eichhornia crassipes and Related Stomatal Responses.

PubMed

Zhao, Jian; Ren, Wenting; Dai, Yanhui; Liu, Lijiao; Wang, Zhenyu; Yu, Xiaoyu; Zhang, Junzhe; Wang, Xiangke; Xing, Baoshan

2017-07-05

Engineered nanoparticles (NPs) are being released into aquatic environments with their increasing applications. In this work, we investigated the interaction of CuO NPs with a floating plant, water hyacinth (Eichhornia crassipes). CuO NPs (50 mg/L) showed significant growth inhibition on both roots and shoots of E. crassipes after 8-day exposure, much higher than that of the bulk CuO particles (50 mg/L) and their corresponding dissolved Cu 2+ ions (0.30 mg/L). Scanning electron and light microscopic observations showed that the root caps and meristematic zone of E. Crassipes were severely damaged after CuO NP exposure, with disordered cell arrangement and a destroyed elongation zone of root tips. It is confirmed that CuO NPs could be translocated to shoot from both roots and submerged leaves. As detected by X-ray absorption near-edge spectroscopy analysis (XANES), CuO NPs were observed in roots, submerged leaves, and emerged leaves. Cu 2 S and other Cu species were also detected in these tissues, providing solid evidence of the transformation of CuO NPs. In addition, stomatal closure was observed during CuO NPs-leaf contact, which was induced by the production of H 2 O 2 and increased Ca level in leaf guard cells. These findings are helpful for better understanding the fate of NPs in aquatic plants and related biological responses.

Analysis of Cytokinin Mutants and Regulation of Cytokinin Metabolic Genes Reveals Important Regulatory Roles of Cytokinins in Drought, Salt and Abscisic Acid Responses, and Abscisic Acid Biosynthesis[C][W

PubMed Central

Nishiyama, Rie; Watanabe, Yasuko; Fujita, Yasunari; Le, Dung Tien; Kojima, Mikiko; Werner, Tomás; Vankova, Radomira; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo; Kakimoto, Tatsuo; Sakakibara, Hitoshi; Schmülling, Thomas; Tran, Lam-Son Phan

2011-01-01

Cytokinins (CKs) regulate plant growth and development via a complex network of CK signaling. Here, we perform functional analyses with CK-deficient plants to provide direct evidence that CKs negatively regulate salt and drought stress signaling. All CK-deficient plants with reduced levels of various CKs exhibited a strong stress-tolerant phenotype that was associated with increased cell membrane integrity and abscisic acid (ABA) hypersensitivity rather than stomatal density and ABA-mediated stomatal closure. Expression of the Arabidopsis thaliana ISOPENTENYL-TRANSFERASE genes involved in the biosynthesis of bioactive CKs and the majority of the Arabidopsis CYTOKININ OXIDASES/DEHYDROGENASES genes was repressed by stress and ABA treatments, leading to a decrease in biologically active CK contents. These results demonstrate a novel mechanism for survival under abiotic stress conditions via the homeostatic regulation of steady state CK levels. Additionally, under normal conditions, although CK deficiency increased the sensitivity of plants to exogenous ABA, it caused a downregulation of key ABA biosynthetic genes, leading to a significant reduction in endogenous ABA levels in CK-deficient plants relative to the wild type. Taken together, this study provides direct evidence that mutual regulation mechanisms exist between the CK and ABA metabolism and signals underlying different processes regulating plant adaptation to stressors as well as plant growth and development. PMID:21719693

Comparison Of Intake Gate Closure Methods At Lower Granite, Little Goose, Lower Monumental, And Mcnary Dams Using Risk-Based Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gore, Bryan F.; Blackburn, Tyrone R.; Heasler, Patrick G.

2001-01-19

The objective of this report is to compare the benefits and costs of modifications proposed for intake gate closure systems at four hydroelectric stations on the Lower Snake and Upper Columbia Rivers in the Walla Walla District that are unable to meet the COE 10-minute closure rule due to the installation of fish screens. The primary benefit of the proposed modifications is to reduce the risk of damage to the station and environs when emergency intake gate closure is required. Consequently, this report presents the results and methodology of an extensive risk analysis performed to assess the reliability of powerhousemore » systems and the costs and timing of potential damages resulting from events requiring emergency intake gate closure. As part of this analysis, the level of protection provided by the nitrogen emergency closure system was also evaluated. The nitrogen system was the basis for the original recommendation to partially disable the intake gate systems. The risk analysis quantifies this protection level.« less

The birthweight toll of mining pollution: evidence from the most contaminated mine site in the Andean region.

PubMed

Arrieta, A; Guillen, J

2018-04-26

To assess the effect of mining pollution on birthweight. A retrospective before-and-after study with an untreated comparison group. La Oroya, a mining town in the Peruvian Andes, considered the most contaminated town in the Andean region. All pregnant women who delivered in the social security healthcare system in years 2005, 2006, 2008 and 2009. A total of 214 983 births records were used, 957 from La Oroya and 214 026 from the rest of the country. A difference-in-difference estimation is used to assess the effect of mining pollution on birthweight before and after two business policy changes: a partial environmental improvement and a subsequent closure of smelter operations in La Oroya. Birthweight was compared with a group not affected by the environmental changes in La Oroya. Birthweight in grams. A steep reduction in mining pollution due to the closure of smelter operations in La Oroya showed an increased birthweight of 71.6 g after controlling for socio-economic and medical characteristics. None of the environmental improvements prior to the closure had a statistically significant effect on birthweight. Mining pollution in La Oroya had a negative impact on birthweight. Partial environmental improvements were not enough to improve birthweight. Only after the closure of all mining and smelter operations in La Oroya was a significant gain in birthweight shown. The closure of the most contaminated mine site in the Andean region increased birthweight by 72 g. © 2018 Royal College of Obstetricians and Gynaecologists.

Sizing of patent ductus arteriosus in adults for transcatheter closure using the balloon pull-through technique.

PubMed

Shafi, Nabil A; Singh, Gagan D; Smith, Thomas W; Rogers, Jason H

2018-05-01

To describe a novel balloon sizing technique used during adult transcatheter patent ductus arteriosus (PDA) closure. In addition, to determine the clinical and procedural outcomes in six patients who underwent PDA balloon sizing with subsequent deployment of a PDA occluder device. Transcatheter PDA closure in adults has excellent safety and procedural outcomes. However, PDA sizing in adults can be challenging due to variable defect size, high flow state, or anatomical complexity. We describe a series of six cases where the balloon- pull through technique was successfully performed for PDA sizing prior to transcatheter closure. Consecutive adult patients undergoing adult PDA closure at our institution were studied retrospectively. A partially inflated sizing balloon was pulled through the defect from the aorta into the pulmonary artery and the balloon waist diameter was measured. Procedural success and clinical outcomes were obtained. Six adult patients underwent successful balloon pull-through technique for PDA sizing during transcatheter PDA closure, since conventional angiography often gave suboptimal opacification of the defect. All PDAs were treated with closure devices based on balloon PDA sizing with complete closure and no complications. In three patients that underwent preprocedure computed tomography, the balloon size matched the CT derived measurements. The balloon pull-through technique for PDA sizing is a safe and accurate sizing modality in adults undergoing transcatheter PDA closure. © 2017 Wiley Periodicals, Inc.

How will climate change influence grapevine cv. Tempranillo photosynthesis under different soil textures?

PubMed

Leibar, Urtzi; Aizpurua, Ana; Unamunzaga, Olatz; Pascual, Inmaculada; Morales, Fermín

2015-05-01

While photosynthetic responses to elevated CO2, elevated temperature, or water availability have previously been reported for grapevine as responses to single stress factors, reports on the combined effect of multiple stress factors are scarce. In the present work, we evaluated effects of simulated climate change [CC; 700 ppm CO2, 28/18 °C, and 33/53% relative humidity (RH), day/night] versus current conditions (375 ppm CO2, 24/14 °C, and 45/65% RH), water availability (well-irrigated vs. water deficit), and different types of soil textures (41, 19, and 8% of soil clay contents) on grapevine (Vitis vinifera L. cv. Tempranillo) photosynthesis. Plants were grown using the fruit-bearing cutting model. CC increased the photosynthetic activity of grapevine plants grown under well-watered conditions, but such beneficial effects of elevated CO2, elevated temperature, and low RH were abolished by water deficit. Under water-deficit conditions, plants subjected to CC conditions had similar photosynthetic rates as those grown under current conditions, despite their higher sub-stomatal CO2 concentrations. As expected, water deficit reduced photosynthetic activity in association with inducing stomatal closure that prevents water loss. Evidence for photosynthetic downregulation under elevated CO2 was observed, with decreases in photosynthetic capacity and leaf N content and increases in the C/N ratio in plants subjected to CC conditions. Soil texture had no marked effects on photosynthesis and did not modify the photosynthetic response to CC and water-deficit conditions. However, in mature well-irrigated plants grown in the soils with the highest sand content, an important decrease in stomatal conductance was observed as well as a slight decrease in the utilization of absorbed light in photosynthetic electron transport (measured as photochemical quenching), possibly related to a low water-retention capacity of these soils even under well-watered conditions.

Changes in Air CO2 Concentration Differentially Alter Transcript Levels of NtAQP1 and NtPIP2;1 Aquaporin Genes in Tobacco Leaves

PubMed Central

Secchi, Francesca; Schubert, Andrea; Lovisolo, Claudio

2016-01-01

The aquaporin specific control on water versus carbon pathways in leaves is pivotal in controlling gas exchange and leaf hydraulics. We investigated whether Nicotiana tabacum aquaporin 1 (NtAQP1) and Nicotiana tabacum plasma membrane intrinsic protein 2;1 (NtPIP2;1) gene expression varies in tobacco leaves subjected to treatments with different CO2 concentrations (ranging from 0 to 800 ppm), inducing changes in photosynthesis, stomatal regulation and water evaporation from the leaf. Changes in air CO2 concentration ([CO2]) affected net photosynthesis (Pn) and leaf substomatal [CO2] (Ci). Pn was slightly negative at 0 ppm air CO2; it was one-third that of ambient controls at 200 ppm, and not different from controls at 800 ppm. Leaves fed with 800 ppm [CO2] showed one-third reduced stomatal conductance (gs) and transpiration (E), and their gs was in turn slightly lower than in 200 ppm– and in 0 ppm–treated leaves. The 800 ppm air [CO2] strongly impaired both NtAQP1 and NtPIP2;1 gene expression, whereas 0 ppm air [CO2], a concentration below any in vivo possible conditions and specifically chosen to maximize the gene expression alteration, increased only the NtAQP1 transcript level. We propose that NtAQP1 expression, an aquaporin devoted to CO2 transport, positively responds to CO2 scarcity in the air in the whole range 0–800 ppm. On the contrary, expression of NtPIP2;1, an aquaporin not devoted to CO2 transport, is related to water balance in the leaf, and changes in parallel with gs. These observations fit in a model where upregulation of leaf aquaporins is activated at low Ci, while downregulation occurs when high Ci saturates photosynthesis and causes stomatal closure. PMID:27089333

Interaction of Water Supply and N in Wheat 1

PubMed Central

Morgan, Jack A.

1984-01-01

The purpose of this study was to investigate effects of N nutrition and water stress on stomatal behavior and CO2 exchange rate in wheat (Triticum aestivum L. cv Olaf). Wheat plants were grown hydroponically with high (100 milligrams per liter) and low (10 milligrams per liter) N. When plants were 38 days old, a 24-day water stress cycle was begun. A gradual increase in nutrient solution osmotic pressure from 0.03 to 1.95 mega Pascals was achieved by incremental additions of PEG-6,000. Plants in both N treatments adjusted osmotically, although leaf water potential was consistently lower and relative water content greater for low N plants in the first half of the stress cycle. Leaf conductance of high N plants appeared greater than that of low N plants at high water potentials, but showed greater sensitivity to reductions in water potential as indicated by earlier stomatal closure during the stress cycle. The apparent greater stomatal sensitivity of high N plants was associated with a curvilinear relationship between leaf conductance and leaf water potential; low N plants exhibited more of a threshold response. Trends in [CO2]INT throughout the stress cycle indicated nonstomatal effects of water stress on CO2 exchange rate were greater in high N plants. Although estimates of [CO2]INT were generally lower in high N plants, they were relatively insensitive to leaf water potential-induced changes in leaf conductance. In contrast, [CO2]INT of low N plants dropped concomitantly with leaf conductance at low leaf water potentials. Oxygen response of CO2 exchange rate for both treatments was affected less by reductions in water potential than was CO2 exchange rate at 2.5% O2, suggesting that CO2 assimilation capacity of the leaves was affected more by reductions in leaf water potential than were processes related to photorespiration. PMID:16663780

Delayed closure of the palatal defect using buccal inversion and palatal rotation flaps after maxillectomy.

PubMed

Jung, Seunggon; Kook, Min-Suk; Park, Hong-Ju; Oh, Hee-Kyun

2013-03-01

Maxillectomy leaves oronasal and oroantral defects that result in functional impairment of mastication, deglutition, and speech. Many treatment options are suggested and tried including the palatal flap as local flap. Although palatal flaps have been used to repair various oral cavity defects, they have certain limitations due to the dimensions. The amount and location of the palatal tissues available are important for palatal repair. Secondary intentional healing after maxillectomy will allow the epithelialization of the defect margin adjacent to remained palate, and there will be more mucosa that is available for closure of the defect. We delayed the closure of the palatal defect, while the patient underwent prosthetic treatment for functional recovery in 5 maxillectomy patients. Delayed closure of palatal defect with local flap was done at 10.8 ± 7.9 months after the maxillectomy. While delayed closure in hemimaxillectomy patients left postoperative fistula, it provided separation of the oral cavity and nasal/sinus cavity and adequate surface for prosthesis in partial maxillectomy patients.

Drought stress and carbon assimilation in a warming climate: Reversible and irreversible impacts.

PubMed

Feller, Urs

2016-09-20

Global change is characterized by increased CO 2 concentration in the atmosphere, increasing average temperature and more frequent extreme events including drought periods, heat waves and flooding. Especially the impacts of drought and of elevated temperature on carbon assimilation are considered in this review. Effects of extreme events on the subcellular level as well as on the whole plant level may be reversible, partially reversible or irreversible. The photosynthetically active biomass depends on the number and the size of mature leaves and the photosynthetic activity in this biomass during stress and subsequent recovery phases. The total area of active leaves is determined by leaf expansion and senescence, while net photosynthesis per leaf area is primarily influenced by stomatal opening (stomatal conductance), mesophyll conductance, activity of the photosynthetic apparatus (light absorption and electron transport, activity of the Calvin cycle) and CO 2 release by decarboxylation reactions (photorespiration, dark respiration). Water status, stomatal opening and leaf temperature represent a "magic triangle" of three strongly interacting parameters. The response of stomata to altered environmental conditions is important for stomatal limitations. Rubisco protein is quite thermotolerant, but the enzyme becomes at elevated temperature more rapidly inactivated (decarbamylation, reversible effect) and must be reactivated by Rubisco activase (carbamylation of a lysine residue). Rubisco activase is present under two forms (encoded by separate genes or products of alternative splicing of the pre-mRNA from one gene) and is very thermosensitive. Rubisco activase was identified as a key protein for photosynthesis at elevated temperature (non-stomatal limitation). During a moderate heat stress Rubisco activase is reversibly inactivated, but during a more severe stress (higher temperature and/or longer exposure) the protein is irreversibly inactivated, insolubilized and finally degraded. On the level of the leaf, this loss of photosynthetic activity may still be reversible when new Rubisco activase is produced by protein synthesis. Rubisco activase as well as enzymes involved in the detoxification of reactive oxygen species or in osmoregulation are considered as important targets for breeding crop plants which are still productive under drought and/or at elevated leaf temperature in a changing climate. Copyright © 2016 Elsevier GmbH. All rights reserved.

Plasticity in stomatal size and density of potato leaves under different irrigation and phosphorus regimes.

PubMed

Sun, Yanqi; Yan, Fei; Cui, Xiaoyong; Liu, Fulai

2014-09-01

The morphological features of stomata including their size and density could be modulated by environmental cues; however, the underlying mechanisms remain largely elusive. Here, the effect of different irrigation and phosphorus (P) regimes on stomatal size (SS) and stomatal density (SD) of potato leaves was investigated. The plants were grown in split-root pots under two P fertilization rates (viz., 0 and 100mgkg(-1) soil, denoted as P0 and P1, respectively) and subjected to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation regimes. Results showed that SS and SD were unresponsive to P but significantly affected by the irrigation treatment. FI plants had the largest SS, followed by DI, and PRD the smallest; and the reverse was the case for SD. Compared to FI and DI, PRD plants had significantly lower values of specific leaf area (SLA) and leaf carbon isotope discrimination (Δ(13)C) under P0. Midday leaf water potential (Ψleaf) and stomatal conductance (gs) was similar for DI and PRD, which was significantly lower than that of FI. Leaf contents of C, N, K, Ca and Mg were higher in PRD than in DI plants, particularly under P0. When analyzed across the three irrigation regimes, it was found that the P1 plants had significantly higher leaf contents of P and Mg, but significantly lower leaf K content compared to the P0 plants. Linear correlation analyses revealed that SS was positively correlated with Ψleaf and Δ(13)C; whereas SD was negatively correlated with Ψleaf, Δ(13)C and SLA, and positively correlated with leaf C, N and Ca contents. And gs was positively correlated with SS but negatively correlated with SD. Collectively, under low P level, the smaller and denser stomata in PRD plants may bring about a more efficient stomatal control over gas exchange, hereby potentially enhance water-use efficiency as exemplified by the lowered leaf Δ(13)C under fluctuating soil moisture conditions. Copyright © 2014 Elsevier GmbH. All rights reserved.

Stomatal and non-stomatal factors regulated the photosynthesis of soybean seedlings in the present of exogenous bisphenol A.

PubMed

Jiao, Liya; Wang, Lihong; Zhou, Qing; Huang, Xiaohua

2017-11-01

Bisphenol A (BPA) is an emerging environmental endocrine disruptor that has toxic effects on plants growth. Photosynthesis supplies the substances and energy required for plant growth, and regulated by stomatal and non-stomatal factors. Therefore, in this study, to reveal how BPA affects photosynthesis in soybean seedlings (Glycine max L.) from the perspective of stomatal and non-stomatal factors, the stomatal factors (stomatal conductance and behaviours) and non-stomatal factors (Hill reaction, apparent quantum efficiency, Rubisco activity, carboxylation efficiency, the maximum Rubisco carboxylation velocity, ribulose-1,5-bisphospate regeneration capacities mediated by maximum electron transport rates, and triose phosphate utilization rate) were investigated using a portable photosynthesis system. Moreover, the pollution of BPA in the environment was simulated. The results indicate that low-dose BPA enhanced net photosynthetic rate (P n ) primarily by promoting stomatal factors, resulting in increased relative growth rates and accelerated soybean seedling growth. High-dose BPA decreases the P n by simultaneously inhibiting stomatal and non-stomatal factors, and this inhibition decreases the relative growth rates further reducing soybean seedling growth. Following the withdrawal of BPA, all of the indices were restored to varying degrees. In conclusion, low-dose BPA increased the P n by promoting stomatal factors while high-dose BPA decreased the P n by simultaneously inhibiting stomatal and non-stomatal factors. These findings provide a model (or, hypothesis) for the effects of BPA on plant photosynthesis. Copyright © 2017 Elsevier Inc. All rights reserved.

Analysis of the entry mechanism of Crimean-Congo hemorrhagic fever virus, using a vesicular stomatitis virus pseudotyping system.

PubMed

Suda, Yuto; Fukushi, Shuetsu; Tani, Hideki; Murakami, Shin; Saijo, Masayuki; Horimoto, Taisuke; Shimojima, Masayuki

2016-06-01

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease causing severe hemorrhagic symptoms with a nearly 30 % case-fatality rate in humans. The experimental use of CCHF virus (CCHFV), which causes CCHF, requires high-biosafety-level (BSL) containment. In contrast, pseudotyping of various viral glycoproteins (GPs) onto vesicular stomatitis virus (VSV) can be used in facilities with lower BSL containment, and this has facilitated studies on the viral entry mechanism and the measurement of neutralizing activity, especially for highly pathogenic viruses. In the present study, we generated high titers of pseudotyped VSV bearing the CCHFV envelope GP and analyzed the mechanisms involved in CCHFV infection. A partial deletion of the CCHFV GP cytoplasmic domain increased the titer of the pseudotyped VSV, the entry mechanism of which was dependent on the CCHFV envelope GP. Using the pseudotype virus, DC-SIGN (a calcium-dependent [C-type] lectin cell-surface molecule) was revealed to enhance viral infection and act as an entry factor for CCHFV.

Partial Root-Zone Drying of Olive (Olea europaea var. 'Chetoui') Induces Reduced Yield under Field Conditions

PubMed Central

Dbara, Soumaya; Haworth, Matthew; Emiliani, Giovani; Ben Mimoun, Mehdi; Gómez-Cadenas, Aurelio; Centritto, Mauro

2016-01-01

The productivity of olive trees in arid and semi-arid environments is closely linked to irrigation. It is necessary to improve the efficiency of irrigation techniques to optimise the amount of olive fruit produced in relation to the volume of water used. Partial root-zone drying (PRD) is a water saving irrigation technique that theoretically allows the production of a root-to-shoot signal that modifies the physiology of the above-ground parts of the plant; specifically reducing stomatal conductance (gs) and improving water use efficiency (WUE). Partial root-zone drying has been successfully applied under field conditions to woody and non-woody crops; yet the few previous trials with olive trees have produced contrasting results. Thirty year-old olive trees (Olea europaea ‘var. Chetoui’) in a Tunisian grove were exposed to four treatments from May to October for three-years: ‘control’ plants received 100% of the potential evapotranspirative demand (ETc) applied to the whole root-zone; ‘PRD100’ were supplied with an identical volume of water to the control plants alternated between halves of the root-zone every ten-days; ‘PRD50’ were given 50% of ETc to half of the root-system, and; ‘rain-fed’ plants received no supplementary irrigation. Allowing part of the root-zone to dry resulted in reduced vegetative growth and lower yield: PRD100 decreased yield by ~47% during productive years. During the less productive years of the alternate bearing cycle, irrigation had no effect on yield; this suggests that withholding of water during ‘off-years’ may enhance the effectiveness of irrigation over a two-year cycle. The amount and quality of oil within the olive fruit was unaffected by the irrigation treatment. Photosynthesis declined in the PRD50 and rain-fed trees due to greater diffusive limitations and reduced biochemical uptake of CO2. Stomatal conductance and the foliar concentration of abscisic acid (ABA) were not altered by PRD100 irrigation, which may indicate the absence of a hormonal root-to-shoot signal. Rain-fed and PRD50 treatments induced increased stem water potential and increased foliar concentrations of ABA, proline and soluble sugars. The stomata of the olive trees were relatively insensitive to super-ambient increases in [CO2] and higher [ABA]. These characteristics of ‘hydro-passive’ stomatal behaviour indicate that the ‘Chetoui’ variety of olive tree used in this study lacks the physiological responses required for the successful exploitation of PRD techniques to increase yield and water productivity. Alternative irrigation techniques such as partial deficit irrigation may be more suitable for ‘Chetoui’ olive production. PMID:27315081

Perforated gastric ulcer--reappraisal of surgical options.

PubMed

Madiba, T E; Nair, R; Mulaudzi, T V; Thomson, S R

2005-08-01

The available operative procedures for perforated gastric ulcer are gastrectomy, ulcer excision and omental patch closure. This study analysed the outcome of these operative options in a single institution. Seventy-two patients (mean age 43 years, 62 males) with perforated gastric ulcers were managed by laparotomy. There were 34 lesser curve (incisural) and 38 antral ulcers. Partial gastrectomy was performed in 27 patients, ulcer excision in 27 and simple patch closure in 18. Two ulcers were malignant. The mortality rate was 18% (26% for gastrectomy, 19% for ulcer excision and 5% for patch closure). Shock on admission (p = 0.006) and Candida (p = 0.020) in the histological specimen were predictive of poor outcome. Hospital stay was similar in the 3 groups. Omental patch closure and ulcer excision are as effective as gastrectomy in the management of perforated gastric ulcer and merit consideration as first-line therapy in technically applicable cases.

Rubber closures for freeze-dried products.

PubMed

Hopkins, G H

1976-10-01

Once a biological product has been developed to perform its required medical or pharmaceutical function, it is essential that a container-closure system by chosen which will preserve the efficacy of the product up to the point of administration. The general requirements applicable to proper closure function will be reviewed and the suitability of natural and synthetic elastomers to perform these functions will be discussed. The specialized application of elastomeric materials as closures for freeze-dried products presents additional requirements which are superimposed upon those previously discussed. The first of these unique considerations relates to the proper physical design which will permit the outgassing of water vapor during the sublimation step in the lyophilizing chamber. During this outgassing the design must also permit the closure to remain affixed in the neck while only partially inserted. Since these preparations are lyophilized because they are unstable in aqueous solutions, the elastomer used must constitute an effective barrier to the transmission of moisture vapor through the closure. The MVT and gas transmission properties of elastomers will be discussed. Special consideration will be given to the extremely low temperatures used in the sublimation, stoppering, and storage before use of lyophilized products. The phenomenon of glass transition points with different elastomers will be explained as its relation to satisfactory performance of the closure function at low temperatures.

Natural variation in stomatal abundance of Arabidopsis thaliana includes cryptic diversity for different developmental processes

PubMed Central

Delgado, Dolores; Alonso-Blanco, Carlos; Fenoll, Carmen; Mena, Montaña

2011-01-01

Background and Aims Current understanding of stomatal development in Arabidopsis thaliana is based on mutations producing aberrant, often lethal phenotypes. The aim was to discover if naturally occurring viable phenotypes would be useful for studying stomatal development in a species that enables further molecular analysis. Methods Natural variation in stomatal abundance of A. thaliana was explored in two collections comprising 62 wild accessions by surveying adaxial epidermal cell-type proportion (stomatal index) and density (stomatal and pavement cell density) traits in cotyledons and first leaves. Organ size variation was studied in a subset of accessions. For all traits, maternal effects derived from different laboratory environments were evaluated. In four selected accessions, distinct stomatal initiation processes were quantitatively analysed. Key Results and Conclusions Substantial genetic variation was found for all six stomatal abundance-related traits, which were weakly or not affected by laboratory maternal environments. Correlation analyses revealed overall relationships among all traits. Within each organ, stomatal density highly correlated with the other traits, suggesting common genetic bases. Each trait correlated between organs, supporting supra-organ control of stomatal abundance. Clustering analyses identified accessions with uncommon phenotypic patterns, suggesting differences among genetic programmes controlling the various traits. Variation was also found in organ size, which negatively correlated with cell densities in both organs and with stomatal index in the cotyledon. Relative proportions of primary and satellite lineages varied among the accessions analysed, indicating that distinct developmental components contribute to natural diversity in stomatal abundance. Accessions with similar stomatal indices showed different lineage class ratios, revealing hidden developmental phenotypes and showing that genetic determinants of primary and satellite lineage initiation combine in several ways. This first systematic, comprehensive natural variation survey for stomatal abundance in A. thaliana reveals cryptic developmental genetic variation, and provides relevant relationships amongst stomatal traits and extreme or uncommon accessions as resources for the genetic dissection of stomatal development. PMID:21447490

The correlations and sequence of plant stomatal, hydraulic, and wilting responses to drought

PubMed Central

Bartlett, Megan K.; Klein, Tamir; Jansen, Steven; Choat, Brendan; Sack, Lawren

2016-01-01

Climate change is expected to exacerbate drought for many plants, making drought tolerance a key driver of species and ecosystem responses. Plant drought tolerance is determined by multiple traits, but the relationships among traits, either within individual plants or across species, have not been evaluated for general patterns across plant diversity. We synthesized the published data for stomatal closure, wilting, declines in hydraulic conductivity in the leaves, stems, and roots, and plant mortality for 262 woody angiosperm and 48 gymnosperm species. We evaluated the correlations among the drought tolerance traits across species, and the general sequence of water potential thresholds for these traits within individual plants. The trait correlations across species provide a framework for predicting plant responses to a wide range of water stress from one or two sampled traits, increasing the ability to rapidly characterize drought tolerance across diverse species. Analyzing these correlations also identified correlations among the leaf and stem hydraulic traits and the wilting point, or turgor loss point, beyond those expected from shared ancestry or independent associations with water stress alone. Further, on average, the angiosperm species generally exhibited a sequence of drought tolerance traits that is expected to limit severe tissue damage during drought, such as wilting and substantial stem embolism. This synthesis of the relationships among the drought tolerance traits provides crucial, empirically supported insight into representing variation in multiple traits in models of plant and ecosystem responses to drought. PMID:27807136

The karrikin receptor KAI2 promotes drought resistance in Arabidopsis thaliana

PubMed Central

Li, Weiqiang; Nguyen, Kien Huu; Ha, Chien Van; Watanabe, Yasuko; Osakabe, Yuriko; Leyva-González, Marco Antonio; Sato, Mayuko; Tanaka, Maho; Mostofa, Mohammad Golam; Seki, Motoaki; Seo, Mitsunori; Yamaguchi, Shinjiro; Nelson, David C.; Herrera-Estrella, Luis

2017-01-01

Drought causes substantial reductions in crop yields worldwide. Therefore, we set out to identify new chemical and genetic factors that regulate drought resistance in Arabidopsis thaliana. Karrikins (KARs) are a class of butenolide compounds found in smoke that promote seed germination, and have been reported to improve seedling vigor under stressful growth conditions. Here, we discovered that mutations in KARRIKIN INSENSITIVE2 (KAI2), encoding the proposed karrikin receptor, result in hypersensitivity to water deprivation. We performed transcriptomic, physiological and biochemical analyses of kai2 plants to understand the basis for KAI2-regulated drought resistance. We found that kai2 mutants have increased rates of water loss and drought-induced cell membrane damage, enlarged stomatal apertures, and higher cuticular permeability. In addition, kai2 plants have reduced anthocyanin biosynthesis during drought, and are hyposensitive to abscisic acid (ABA) in stomatal closure and cotyledon opening assays. We identified genes that are likely associated with the observed physiological and biochemical changes through a genome-wide transcriptome analysis of kai2 under both well-watered and dehydration conditions. These data provide evidence for crosstalk between ABA- and KAI2-dependent signaling pathways in regulating plant responses to drought. A comparison of the strigolactone receptor mutant d14 (DWARF14) to kai2 indicated that strigolactones also contributes to plant drought adaptation, although not by affecting cuticle development. Our findings suggest that chemical or genetic manipulation of KAI2 and D14 signaling may provide novel ways to improve drought resistance. PMID:29131815

The karrikin receptor KAI2 promotes drought resistance in Arabidopsis thaliana.

PubMed

Li, Weiqiang; Nguyen, Kien Huu; Chu, Ha Duc; Ha, Chien Van; Watanabe, Yasuko; Osakabe, Yuriko; Leyva-González, Marco Antonio; Sato, Mayuko; Toyooka, Kiminori; Voges, Laura; Tanaka, Maho; Mostofa, Mohammad Golam; Seki, Motoaki; Seo, Mitsunori; Yamaguchi, Shinjiro; Nelson, David C; Tian, Chunjie; Herrera-Estrella, Luis; Tran, Lam-Son Phan

2017-11-01

Drought causes substantial reductions in crop yields worldwide. Therefore, we set out to identify new chemical and genetic factors that regulate drought resistance in Arabidopsis thaliana. Karrikins (KARs) are a class of butenolide compounds found in smoke that promote seed germination, and have been reported to improve seedling vigor under stressful growth conditions. Here, we discovered that mutations in KARRIKIN INSENSITIVE2 (KAI2), encoding the proposed karrikin receptor, result in hypersensitivity to water deprivation. We performed transcriptomic, physiological and biochemical analyses of kai2 plants to understand the basis for KAI2-regulated drought resistance. We found that kai2 mutants have increased rates of water loss and drought-induced cell membrane damage, enlarged stomatal apertures, and higher cuticular permeability. In addition, kai2 plants have reduced anthocyanin biosynthesis during drought, and are hyposensitive to abscisic acid (ABA) in stomatal closure and cotyledon opening assays. We identified genes that are likely associated with the observed physiological and biochemical changes through a genome-wide transcriptome analysis of kai2 under both well-watered and dehydration conditions. These data provide evidence for crosstalk between ABA- and KAI2-dependent signaling pathways in regulating plant responses to drought. A comparison of the strigolactone receptor mutant d14 (DWARF14) to kai2 indicated that strigolactones also contributes to plant drought adaptation, although not by affecting cuticle development. Our findings suggest that chemical or genetic manipulation of KAI2 and D14 signaling may provide novel ways to improve drought resistance.

Reduced nighttime transpiration is a relevant breeding target for high water-use efficiency in grapevine

PubMed Central

Coupel-Ledru, Aude; Lebon, Eric; Christophe, Angélique; Gallo, Agustina; Gago, Pilar; Pantin, Florent; Doligez, Agnès; Simonneau, Thierry

2016-01-01

Increasing water scarcity challenges crop sustainability in many regions. As a consequence, the enhancement of transpiration efficiency (TE)—that is, the biomass produced per unit of water transpired—has become crucial in breeding programs. This could be achieved by reducing plant transpiration through a better closure of the stomatal pores at the leaf surface. However, this strategy generally also lowers growth, as stomatal opening is necessary for the capture of atmospheric CO2 that feeds daytime photosynthesis. Here, we considered the reduction in transpiration rate at night (En) as a possible strategy to limit water use without altering growth. For this purpose, we carried out a genetic analysis for En and TE in grapevine, a major crop in drought-prone areas. Using recently developed phenotyping facilities, potted plants of a cross between Syrah and Grenache cultivars were screened for 2 y under well-watered and moderate soil water deficit scenarios. High genetic variability was found for En under both scenarios and was primarily associated with residual diffusion through the stomata. Five quantitative trait loci (QTLs) were detected that underlay genetic variability in En. Interestingly, four of them colocalized with QTLs for TE. Moreover, genotypes with favorable alleles on these common QTLs exhibited reduced En without altered growth. These results demonstrate the interest of breeding grapevine for lower water loss at night and pave the way to breeding other crops with this underexploited trait for higher TE. PMID:27457942

The correlations and sequence of plant stomatal, hydraulic, and wilting responses to drought.

PubMed

Bartlett, Megan K; Klein, Tamir; Jansen, Steven; Choat, Brendan; Sack, Lawren

2016-11-15

Climate change is expected to exacerbate drought for many plants, making drought tolerance a key driver of species and ecosystem responses. Plant drought tolerance is determined by multiple traits, but the relationships among traits, either within individual plants or across species, have not been evaluated for general patterns across plant diversity. We synthesized the published data for stomatal closure, wilting, declines in hydraulic conductivity in the leaves, stems, and roots, and plant mortality for 262 woody angiosperm and 48 gymnosperm species. We evaluated the correlations among the drought tolerance traits across species, and the general sequence of water potential thresholds for these traits within individual plants. The trait correlations across species provide a framework for predicting plant responses to a wide range of water stress from one or two sampled traits, increasing the ability to rapidly characterize drought tolerance across diverse species. Analyzing these correlations also identified correlations among the leaf and stem hydraulic traits and the wilting point, or turgor loss point, beyond those expected from shared ancestry or independent associations with water stress alone. Further, on average, the angiosperm species generally exhibited a sequence of drought tolerance traits that is expected to limit severe tissue damage during drought, such as wilting and substantial stem embolism. This synthesis of the relationships among the drought tolerance traits provides crucial, empirically supported insight into representing variation in multiple traits in models of plant and ecosystem responses to drought.

Reduced nighttime transpiration is a relevant breeding target for high water-use efficiency in grapevine.

PubMed

Coupel-Ledru, Aude; Lebon, Eric; Christophe, Angélique; Gallo, Agustina; Gago, Pilar; Pantin, Florent; Doligez, Agnès; Simonneau, Thierry

2016-08-09

Increasing water scarcity challenges crop sustainability in many regions. As a consequence, the enhancement of transpiration efficiency (TE)-that is, the biomass produced per unit of water transpired-has become crucial in breeding programs. This could be achieved by reducing plant transpiration through a better closure of the stomatal pores at the leaf surface. However, this strategy generally also lowers growth, as stomatal opening is necessary for the capture of atmospheric CO2 that feeds daytime photosynthesis. Here, we considered the reduction in transpiration rate at night (En) as a possible strategy to limit water use without altering growth. For this purpose, we carried out a genetic analysis for En and TE in grapevine, a major crop in drought-prone areas. Using recently developed phenotyping facilities, potted plants of a cross between Syrah and Grenache cultivars were screened for 2 y under well-watered and moderate soil water deficit scenarios. High genetic variability was found for En under both scenarios and was primarily associated with residual diffusion through the stomata. Five quantitative trait loci (QTLs) were detected that underlay genetic variability in En Interestingly, four of them colocalized with QTLs for TE. Moreover, genotypes with favorable alleles on these common QTLs exhibited reduced En without altered growth. These results demonstrate the interest of breeding grapevine for lower water loss at night and pave the way to breeding other crops with this underexploited trait for higher TE.

Frizzled 1 and frizzled 2 genes function in palate, ventricular septum and neural tube closure: general implications for tissue fusion processes

PubMed Central

Yu, Huimin; Smallwood, Philip M.; Wang, Yanshu; Vidaltamayo, Roman; Reed, Randall; Nathans, Jeremy

2010-01-01

The closure of an open anatomical structure by the directed growth and fusion of two tissue masses is a recurrent theme in mammalian embryology, and this process plays an integral role in the development of the palate, ventricular septum, neural tube, urethra, diaphragm and eye. In mice, targeted mutations of the genes encoding frizzled 1 (Fz1) and frizzled 2 (Fz2) show that these highly homologous integral membrane receptors play an essential and partially redundant role in closure of the palate and ventricular septum, and in the correct positioning of the cardiac outflow tract. When combined with a mutant allele of the planar cell polarity gene Vangl2 (Vangl2Lp), Fz1 and/or Fz2 mutations also cause defects in neural tube closure and misorientation of inner ear sensory hair cells. These observations indicate that frizzled signaling is involved in diverse tissue closure processes, defects in which account for some of the most common congenital anomalies in humans. PMID:20940229

Overexpression of a phospholipase (OsPLDα1) for drought tolerance in upland rice (Oryza sativa L.).

PubMed

Abreu, Fernanda Raquel Martins; Dedicova, Beata; Vianello, Rosana Pereira; Lanna, Anna Cristina; de Oliveira, João Augusto Vieira; Vieira, Ariadna Faria; Morais, Odilon Peixoto; Mendonça, João Antônio; Brondani, Claudio

2018-05-30

This work aimed to evaluate the drought tolerance of transformed plants of the cultivar BRSMG Curinga that overexpress the rice phospholipase D α1 (OsPLDα1) gene. The productivity of independent transformation event plants of the OsPLDα1 gene was evaluated in an experiment where 19 days of water deficit were applied at the reproductive stage, a very strict growing condition for upland rice. The non-genetically modified cultivar (NGM) under drought treatment reduced productivity by 89% compared with that under irrigated treatment, whereas transformed plants (PLDα1_E2) reduced productivity by only 41%. After the drought treatment, the PLDα1_E2 plants productivity was five times greater than that of the NGM plant. Moreover, no adverse effects on growth and development of the transgenic plants were observed. Seven days after the resumption of irrigation, PLDα1_E2 plants had higher stomatal conductance, greater photosynthetic rate, and transpiration rate than did NGM plants, as well as a higher expression level of the OsPLDα1 gene. A delay in the senescence process was observed in these PLDα1_E2 plants, and this was determined for the recovery of photosynthesis, with greater expression of the Rubisco and lower expression of the SOD. This finding was suggestive of decreased oxidative stress, probably due to gas exchange by the partial closure of the stomata of these transformed plants, which prevented the formation of reactive oxygen species. OsPLDα1 gene overexpression resulted in a reduction in production loss under severe water deficit and revealed a possibility for the development of upland rice cultivars that are more tolerant to extreme drought conditions.

Physiological and molecular characterization of drought responses and identification of candidate tolerance genes in cassava

PubMed Central

Turyagyenda, Laban F.; Kizito, Elizabeth B.; Ferguson, Morag; Baguma, Yona; Agaba, Morris; Harvey, Jagger J. W.; Osiru, David S. O.

2013-01-01

Cassava is an important root crop to resource-poor farmers in marginal areas, where its production faces drought stress constraints. Given the difficulties associated with cassava breeding, a molecular understanding of drought tolerance in cassava will help in the identification of markers for use in marker-assisted selection and genes for transgenic improvement of drought tolerance. This study was carried out to identify candidate drought-tolerance genes and expression-based markers of drought stress in cassava. One drought-tolerant (improved variety) and one drought-susceptible (farmer-preferred) cassava landrace were grown in the glasshouse under well-watered and water-stressed conditions. Their morphological, physiological and molecular responses to drought were characterized. Morphological and physiological measurements indicate that the tolerance of the improved variety is based on drought avoidance, through reduction of water loss via partial stomatal closure. Ten genes that have previously been biologically validated as conferring or being associated with drought tolerance in other plant species were confirmed as being drought responsive in cassava. Four genes (MeALDH, MeZFP, MeMSD and MeRD28) were identified as candidate cassava drought-tolerance genes, as they were exclusively up-regulated in the drought-tolerant genotype to comparable levels known to confer drought tolerance in other species. Based on these genes, we hypothesize that the basis of the tolerance at the cellular level is probably through mitigation of the oxidative burst and osmotic adjustment. This study provides an initial characterization of the molecular response of cassava to drought stress resembling field conditions. The drought-responsive genes can now be used as expression-based markers of drought stress tolerance in cassava, and the candidate tolerance genes tested in the context of breeding (as possible quantitative trait loci) and engineering drought tolerance in transgenics. PMID:23519782

Evaluation of Morpho-Physiological Traits Adjustment of Prosopis tamarugo Under Long-Term Groundwater Depletion in the Hyper-Arid Atacama Desert

PubMed Central

Garrido, Marco; Silva, Herman; Franck, Nicolás; Arenas, Jorge; Acevedo, Edmundo

2018-01-01

Water extraction from the underground aquifers of the Pampa del Tamarugal (Atacama Desert, Chile) reduced the growing area of Prosopis tamarugo, a strict phreatic species endemic to northern Chile. The objective of this work was to evaluate the effect of various architectural and morpho-physiological traits adjustment of P. tamarugo subjected to three groundwater depletion intervals (GWDr): <1 m (control), 1–4 m and 6–9 m. The traits were evaluated at three levels, plant [height, trunk cross-section area, leaf fraction (fGCC), and crown size], organ [length of internodes, leaf mass per unit area (LMA), leaflet mass and area], and tissue level [wood density (WD), leaf 13C, 18O isotope composition (δ), and intrinsic water use efficiency (iWUE)]. In addition, soil water content (VWC) to 1.3 m soil depth, pre-dawn and midday water potential difference (ΔΨ), and stomatal conductance (gs) were evaluated. At the deeper GWDr, P. tamarugo experienced significant growth restriction and reduced fGCC, the remaining canopy had a significantly higher LMA associated with smaller leaflets. No differences in internode length and WD were observed. Values for δ13C and δ18O indicated that as GWDr increased, iWUE increased as a result of partial stomata closure with no significant effect on net assimilation over time. The morpho-physiological changes experienced by P. tamarugo allowed it to acclimate and survive in a condition of groundwater depletion, keeping a functional but diminished canopy. These adjustments allowed maintenance of a relatively high gs; ΔΨ was not different among GWDrs despite smaller VWC at greater GWDr. Although current conservation initiatives of this species are promising, forest deterioration is expected continue as groundwater depth increases. PMID:29686691

Evaluation of Morpho-Physiological Traits Adjustment of Prosopis tamarugo Under Long-Term Groundwater Depletion in the Hyper-Arid Atacama Desert.

PubMed

Garrido, Marco; Silva, Herman; Franck, Nicolás; Arenas, Jorge; Acevedo, Edmundo

2018-01-01

Water extraction from the underground aquifers of the Pampa del Tamarugal (Atacama Desert, Chile) reduced the growing area of Prosopis tamarugo , a strict phreatic species endemic to northern Chile. The objective of this work was to evaluate the effect of various architectural and morpho-physiological traits adjustment of P. tamarugo subjected to three groundwater depletion intervals (GWDr): <1 m (control), 1-4 m and 6-9 m. The traits were evaluated at three levels, plant [height, trunk cross-section area, leaf fraction ( f GCC), and crown size], organ [length of internodes, leaf mass per unit area (LMA), leaflet mass and area], and tissue level [wood density (WD), leaf 13 C, 18 O isotope composition (δ), and intrinsic water use efficiency (iWUE)]. In addition, soil water content (VWC) to 1.3 m soil depth, pre-dawn and midday water potential difference (ΔΨ), and stomatal conductance (g s ) were evaluated. At the deeper GWDr, P. tamarugo experienced significant growth restriction and reduced f GCC, the remaining canopy had a significantly higher LMA associated with smaller leaflets. No differences in internode length and WD were observed. Values for δ 13 C and δ 18 O indicated that as GWDr increased, iWUE increased as a result of partial stomata closure with no significant effect on net assimilation over time. The morpho-physiological changes experienced by P. tamarugo allowed it to acclimate and survive in a condition of groundwater depletion, keeping a functional but diminished canopy. These adjustments allowed maintenance of a relatively high g s ; ΔΨ was not different among GWDrs despite smaller VWC at greater GWDr. Although current conservation initiatives of this species are promising, forest deterioration is expected continue as groundwater depth increases.

Lead uptake increases drought tolerance of wild type and transgenic poplar (Populus tremula x P. alba) overexpressing gsh 1.

PubMed

Samuilov, Sladjana; Lang, Friedericke; Djukic, Matilda; Djunisijevic-Bojovic, Danijela; Rennenberg, Heinz

2016-09-01

Growth and development of plants largely depends on their adaptation ability in a changing climate. This is particularly true on heavy metal contaminated soils, but the interaction of heavy metal stress and climate on plant performance has not been intensively investigated. The aim of the present study was to elucidate if transgenic poplars (Populus tremula x P. alba) with enhanced glutathione content possess an enhanced tolerance to drought and lead (Pb) exposure (single and in combination) and if they are good candidates for phytoremediation of Pb contaminated soil. Lead exposure reduced growth and biomass accumulation only in above-ground tissue of wild type poplar, although most of lead accumulated in the roots. Drought caused a decline of the water content rather than reduced biomass production, while Pb counteracted this decline in the combined exposure. Apparently, metals such as Pb possess a protective function against drought, because they interact with abscisic acid dependent stomatal closure. Lead exposure decreased while drought increased glutathione content in leaves of both plant types. Lead accumulation was higher in the roots of transgenic plants, presumably as a result of chelation by glutathione. Water deprivation enhanced Pb accumulation in the roots, but Pb was subject to leakage out of the roots after re-watering. Transgenic plants showed better adaptation under mild drought plus Pb exposure partially due to improved glutathione synthesis. However, the transgenic plants cannot be considered as a good candidate for phytoremediation of Pb, due to its small translocation to the shoots and its leakage out of the roots upon re-watering. Copyright © 2016 Elsevier Ltd. All rights reserved.

Analysis of gas exchange, stomatal behaviour and micronutrients uncovers dynamic response and adaptation of tomato plants to monochromatic light treatments.

PubMed

O'Carrigan, Andrew; Babla, Mohammad; Wang, Feifei; Liu, Xiaohui; Mak, Michelle; Thomas, Richard; Bellotti, Bill; Chen, Zhong-Hua

2014-09-01

Light spectrum affects the yield and quality of greenhouse tomato, especially over a prolonged period of monochromatic light treatments. Physiological and chemical analysis was employed to investigate the influence of light spectral (blue, green and red) changes on growth, photosynthesis, stomatal behaviour, leaf pigment, and micronutrient levels. We found that plants are less affected under blue light treatment, which was evident by the maintenance of higher A, gs, Tr, and stomatal parameters and significantly lower VPD and Tleaf as compared to those plants grown in green and red light treatments. Green and red light treatments led to significantly larger increase in the accumulation of Fe, B, Zn, and Cu than blue light. Moreover, guard cell length, width, and volume all showed highly significant positive correlations to gs, Tr and negative links to VPD. There was negative impact of monochromatic lights-induced accumulation of Mn, Cu, and Zn on photosynthesis, leaf pigments and plant growth. Furthermore, most of the light-induced significant changes of the physiological traits were partially recovered at the end of experiment. A high degree of morphological and physiological plasticity to blue, green and red light treatments suggested that tomato plants may have developed mechanisms to adapt to the light treatments. Thus, understanding the optimization of light spectrum for photosynthesis and growth is one of the key components for greenhouse tomato production. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

The potential of biomonitoring of air quality using leaf characteristics of white willow (Salix alba L.).

PubMed

Wuytack, Tatiana; Verheyen, Kris; Wuyts, Karen; Kardel, Fatemeh; Adriaenssens, Sandy; Samson, Roeland

2010-12-01

In this study, we assess the potential of white willow (Salix alba L.) as bioindicator for monitoring of air quality. Therefore, shoot biomass, specific leaf area, stomatal density, stomatal pore surface, and stomatal resistance were assessed from leaves of stem cuttings. The stem cuttings were introduced in two regions in Belgium with a relatively high and a relatively low level of air pollution, i.e., Antwerp city and Zoersel, respectively. In each of these regions, nine sampling points were selected. At each sampling point, three stem cuttings of white willow were planted in potting soil. Shoot biomass and specific leaf area were not significantly different between Antwerp city and Zoersel. Microclimatic differences between the sampling points may have been more important to plant growth than differences in air quality. However, stomatal pore surface and stomatal resistance of white willow were significantly different between Zoersel and Antwerp city. Stomatal pore surface was 20% lower in Antwerp city due to a significant reduction in both stomatal length (-11%) and stomatal width (-14%). Stomatal resistance at the adaxial leaf surface was 17% higher in Antwerp city because of the reduction in stomatal pore surface. Based on these results, we conclude that stomatal characteristics of white willow are potentially useful indicators for air quality.

Magnetohydrodynamic motion of a two-fluid plasma

DOE PAGES

Burby, Joshua W.

2017-07-21

Here, the two-fluid Maxwell system couples frictionless electron and ion fluids via Maxwell’s equations. When the frequencies of light waves, Langmuir waves, and single-particle cyclotron motion are scaled to be asymptotically large, the two-fluid Maxwell system becomes a fast-slow dynamical system. This fast-slow system admits a formally-exact single-fluid closure that may be computed systematically with any desired order of accuracy through the use of a functional partial differential equation. In the leading order approximation, the closure reproduces magnetohydrodynamics (MHD). Higher order truncations of the closure give an infinite hierarchy of extended MHD models that allow for arbitrary mass ratio, asmore » well as perturbative deviations from charge neutrality. The closure is interpreted geometrically as an invariant slow manifold in the infinite-dimensional two-fluid phase space, on which two-fluid motions are free of high-frequency oscillations. This perspective shows that the full closure inherits a Hamiltonian structure from two-fluid theory. By employing infinite-dimensional Lie transforms, the Poisson bracket for the all-orders closure may be obtained in closed form. Thus, conservative truncations of the single-fluid closure may be obtained by simply truncating the single-fluid Hamiltonian. Moreover, the closed-form expression for the all-orders bracket gives explicit expressions for a number of the full closure’s conservation laws. Notably, the full closure, as well as any of its Hamiltonian truncations, admits a pair of independent circulation invariants.« less

Magnetohydrodynamic motion of a two-fluid plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burby, Joshua W.

Here, the two-fluid Maxwell system couples frictionless electron and ion fluids via Maxwell’s equations. When the frequencies of light waves, Langmuir waves, and single-particle cyclotron motion are scaled to be asymptotically large, the two-fluid Maxwell system becomes a fast-slow dynamical system. This fast-slow system admits a formally-exact single-fluid closure that may be computed systematically with any desired order of accuracy through the use of a functional partial differential equation. In the leading order approximation, the closure reproduces magnetohydrodynamics (MHD). Higher order truncations of the closure give an infinite hierarchy of extended MHD models that allow for arbitrary mass ratio, asmore » well as perturbative deviations from charge neutrality. The closure is interpreted geometrically as an invariant slow manifold in the infinite-dimensional two-fluid phase space, on which two-fluid motions are free of high-frequency oscillations. This perspective shows that the full closure inherits a Hamiltonian structure from two-fluid theory. By employing infinite-dimensional Lie transforms, the Poisson bracket for the all-orders closure may be obtained in closed form. Thus, conservative truncations of the single-fluid closure may be obtained by simply truncating the single-fluid Hamiltonian. Moreover, the closed-form expression for the all-orders bracket gives explicit expressions for a number of the full closure’s conservation laws. Notably, the full closure, as well as any of its Hamiltonian truncations, admits a pair of independent circulation invariants.« less

Plant water potential improves prediction of empirical stomatal models.

PubMed

Anderegg, William R L; Wolf, Adam; Arango-Velez, Adriana; Choat, Brendan; Chmura, Daniel J; Jansen, Steven; Kolb, Thomas; Li, Shan; Meinzer, Frederick; Pita, Pilar; Resco de Dios, Víctor; Sperry, John S; Wolfe, Brett T; Pacala, Stephen

2017-01-01

Climate change is expected to lead to increases in drought frequency and severity, with deleterious effects on many ecosystems. Stomatal responses to changing environmental conditions form the backbone of all ecosystem models, but are based on empirical relationships and are not well-tested during drought conditions. Here, we use a dataset of 34 woody plant species spanning global forest biomes to examine the effect of leaf water potential on stomatal conductance and test the predictive accuracy of three major stomatal models and a recently proposed model. We find that current leaf-level empirical models have consistent biases of over-prediction of stomatal conductance during dry conditions, particularly at low soil water potentials. Furthermore, the recently proposed stomatal conductance model yields increases in predictive capability compared to current models, and with particular improvement during drought conditions. Our results reveal that including stomatal sensitivity to declining water potential and consequent impairment of plant water transport will improve predictions during drought conditions and show that many biomes contain a diversity of plant stomatal strategies that range from risky to conservative stomatal regulation during water stress. Such improvements in stomatal simulation are greatly needed to help unravel and predict the response of ecosystems to future climate extremes.

Responses of leaf stomatal density to water status and its relationship with photosynthesis in a grass.

PubMed

Xu, Zhenzhu; Zhou, Guangsheng

2008-01-01

Responses of plant leaf stomatal conductance and photosynthesis to water deficit have been extensively reported; however, little is known concerning the relationships of stomatal density with regard to water status and gas exchange. The responses of stomatal density to leaf water status were determined, and correlation with specific leaf area (SLA) in a photosynthetic study of a perennial grass, Leymus chinensis, subjected to different soil moisture contents. Moderate water deficits had positive effects on stomatal number, but more severe deficits led to a reduction, described in a quadratic parabolic curve. The stomatal size obviously decreased with water deficit, and stomatal density was positively correlated with stomatal conductance (g(s)), net CO(2) assimilation rate (A(n)), and water use efficiency (WUE). A significantly negative correlation of SLA with stomatal density was also observed, suggesting that the balance between leaf area and its matter may be associated with the guard cell number. The present results indicate that high flexibilities in stomatal density and guard cell size will change in response to water status, and this process may be closely associated with photosynthesis and water use efficiency.

Interannual variations in needle and sapwood traits of Pinus edulis branches under an experimental drought

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guerin, Marceau; Martin-Benito, Dario; von Arx, Georg

In recent years, widespread forest mortality in response to drought has been documented worldwide (Allen, Breshears & McDowell 2015). An example of widespread and rapid increase in drought-induced mortality, or die-off, was observed for Pinus edulis Engelm. across the Southwestern USA in response to several years of reduced rainfall and high vapor pressure deficits (VPD) (Breshears et al. 2009; Allen et al. 2010; Williams et al. 2013). Although stomatal closure under drought has been hypothesized to increase mortality through carbon starvation (McDowell et al. 2008; Breshears et al. 2009), more evidences exist for mortality being caused by hydraulic failure (Plautmore » et al. 2012; McDowell et al. 2013; Sevanto et al. 2014; Garcia-Forner et al. 2016). Regardless of the mechanism of drought-induced decline, maintaining a positive supply of water to the foliage is critical for tree functioning and survival.« less

Interannual variations in needle and sapwood traits of Pinus edulis branches under an experimental drought

DOE PAGES

Guerin, Marceau; Martin-Benito, Dario; von Arx, Georg; ...

2018-01-05

In recent years, widespread forest mortality in response to drought has been documented worldwide (Allen, Breshears & McDowell 2015). An example of widespread and rapid increase in drought-induced mortality, or die-off, was observed for Pinus edulis Engelm. across the Southwestern USA in response to several years of reduced rainfall and high vapor pressure deficits (VPD) (Breshears et al. 2009; Allen et al. 2010; Williams et al. 2013). Although stomatal closure under drought has been hypothesized to increase mortality through carbon starvation (McDowell et al. 2008; Breshears et al. 2009), more evidences exist for mortality being caused by hydraulic failure (Plautmore » et al. 2012; McDowell et al. 2013; Sevanto et al. 2014; Garcia-Forner et al. 2016). Regardless of the mechanism of drought-induced decline, maintaining a positive supply of water to the foliage is critical for tree functioning and survival.« less

UV-C induces K sup + efflux from bean but not from oat leaves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huerta, A.J.; Gueltig, B.G.

Previous reports have shown that ultraviolet radiation (UV) induces a specific leakage of K{sup +} from cells in culture as well as from guard cells of bean leaves resulting in stomatal closure. In an effort to determine how general this response may be in photosynthetic leaf cells, we measured the UV-C-induced K{sup +} efflux from irradiated 10-14 day-old bean and oat leaf sections. Our results show that oat leaves do not respond to UV-C irradiation with K{sup +} efflux. However UV-C irradiated bean leaves leaked K{sup +} at a rate of approximately 47 nmoles cm{sup {minus}2} h{sup {minus}1} and themore » leakage was linear for at least 3.5 hours. The source cells for K{sup +} efflux and the possible mechanisms responsible for this difference in UV-sensitivity will be discussed.« less

Response of the Vegetation-Climate System to High Temperature (Invited)

NASA Astrophysics Data System (ADS)

Berry, J. A.

2009-12-01

High temperature extremes may lead to inhibition of photosynthesis and stomatal closure at the leaf scale. When these responses occur over regional scales, they can initiate a positive feedback loop in the coupled vegetation-climate system. The fraction of net radiation that is used by the land surface to evaporate water decreases leading to deeper, drier boundary layers, fewer clouds, increased solar radiation reaching the surface, and possibility reduced precipitation. These interactions within the vegetation-climate system may amplify natural (or greenhouse gas forced) variations in temperature and further stress the vegetation. Properly modeling of this system depends, among other things, on getting the plant responses to high temperature correct. I will review the current state of this problem and present some studies of rain forest trees to high temperature and drought conducted in the Biosphere 2 enclosure that illustrate how experiments in controlled systems can contribute to our understanding of complex systems to extreme events.

Ecophysiology and growth of advance red spruce and balsam fir regeneration after partial cutting in yellow birch-conifer stands.

PubMed

Dumais, Daniel; Prévost, Marcel

2008-08-01

We investigated ecophysiological and growth responses of short (0.4 to 1.3 m in height) advance regeneration of red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea L.) six years after removal of 0, 40, 50, 60 and 100% of the overstory basal area (BA) in two yellow birch-conifer stands. Partial cuts significantly increased stomatal conductance of red spruce only. Light-saturated photosynthesis (leaf-area basis) of both species increased with BA removal, but unlike red spruce, specific leaf area (SLA) of balsam fir decreased with increased cutting intensity. Partial cuts appreciably increased the concentration of N and Ca in red spruce and balsam fir foliage, respectively, and resulted in decreased foliar concentrations of K in red spruce and Mg in balsam fir. The height and lateral growth of both species increased with BA removal, although partial cuts were more beneficial to balsam fir. The data suggest that short advance regeneration of red spruce and balsam fir can coexist under partial overstory conditions, but balsam fir has physiological characteristics and a capacity for morphological adjustment (SLA) that places it at an advantage when in competition with red spruce.

Recent development of transcatheter closure of atrial septal defect and patent foramen ovale with occluders.

PubMed

Tang, Baiyu; Su, Feng; Sun, Xiangke; Wu, Qin; Xing, Quansheng; Li, Suming

2018-01-01

Atrial septal defect (ASD) and patent foramen ovale (PFO) are common clinical congenital heart defects. As an effective method for the treatment of ASD and PFO, transcatheter closure with occluders presents many advantages, including safety, ease of operation, minimal invasiveness, and reduced complications. This contribution reviews the various types of occluders currently used in clinical applications and under development, including non degradable occluders, partially degradable occluders, and totally degradable occluders. A number of case studies are described in detail. Comparison is made on the treatment outcomes using different occulders. Future development of transcatheter closure is discussed, in particular the use of totally degradable occluders. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 433-443, 2018. © 2016 Wiley Periodicals, Inc.

Workshop on Engineering Turbulence Modeling

NASA Technical Reports Server (NTRS)

Povinelli, Louis A. (Editor); Liou, W. W. (Editor); Shabbir, A. (Editor); Shih, T.-H. (Editor)

1992-01-01

Discussed here is the future direction of various levels of engineering turbulence modeling related to computational fluid dynamics (CFD) computations for propulsion. For each level of computation, there are a few turbulence models which represent the state-of-the-art for that level. However, it is important to know their capabilities as well as their deficiencies in order to help engineers select and implement the appropriate models in their real world engineering calculations. This will also help turbulence modelers perceive the future directions for improving turbulence models. The focus is on one-point closure models (i.e., from algebraic models to higher order moment closure schemes and partial differential equation methods) which can be applied to CFD computations. However, other schemes helpful in developing one-point closure models, are also discussed.

Peach leaf responses to soil and cement dust pollution.

PubMed

Maletsika, Persefoni A; Nanos, George D; Stavroulakis, George G

2015-10-01

Dust pollution can negatively affect plant productivity in hot, dry and with high irradiance areas during summer. Soil or cement dust were applied on peach trees growing in a Mediterranean area with the above climatic characteristics. Soil and cement dust accumulation onto the leaves decreased the photosynthetically active radiation (PAR) available to the leaves without causing any shade effect. Soil and mainly cement dust deposition onto the leaves decreased stomatal conductance, photosynthetic and transpiration rates, and water use efficiency due possibly to stomatal blockage and other leaf cellular effects. In early autumn, rain events removed soil dust and leaf functions partly recovered, while cement dust created a crust partially remaining onto the leaves and causing more permanent stress. Leaf characteristics were differentially affected by the two dusts studied due to their different hydraulic properties. Leaf total chlorophyll decreased and total phenol content increased with dust accumulation late in the summer compared to control leaves due to intense oxidative stress. The two dusts did not cause serious metal imbalances to the leaves, except of lower leaf K content.

Elevated ozone negatively affects photosynthesis of current-year leaves but not previous-year leaves in evergreen Cyclobalanopsis glauca seedlings.

PubMed

Zhang, Weiwei; Feng, Zhaozhong; Wang, Xiaoke; Niu, Junfeng

2014-01-01

To assess the effects of leaf age/layer on the response of photosynthesis to chronic ozone (O3), Cyclobalanopsis glauca seedlings, a dominant evergreen broadleaf tree species in sub-tropical regions, were exposed to either ambient air (AA) or elevated O3 (AA + 60 ppb O3, E-O3) for two growing seasons in open-top chambers. Chlorophyll content, gas exchange and chlorophyll a fluorescence were investigated three times throughout the 2nd year of O3 exposure. Results indicated that E-O3 decreased photosynthetic parameters, particularly light-saturated photosynthesis rate, stomatal conductance and effective quantum yield of PSII photochemistry of current-year leaves but not previous-year leaves. Stomatal conductance of plants grown under ambient conditions partially contributed to the different response to E-O3 between leaf layers. Light radiation or other physiological and biochemical processes closely related to photosynthesis might play important roles. All suggested that leaf ages or layers should be considered when assessing O3 risk on evergreen woody species. Copyright © 2013 Elsevier Ltd. All rights reserved.

Functional and esthetic outcome enhancement of periodontal surgery by application of plastic surgery principles.

PubMed

Hürzeler, M B; Weng, D

1999-02-01

The closure of surgical wounds in a layer-by-layer fashion, a common principle of plastic surgery, is applied in this article to the field of periodontal surgery with the introduction of a new flap design. The suggested technique is indicated with all periodontal procedures that aim for hard and soft tissue augmentation (guided bone regeneration, mucogingival surgery, or plastic periodontal surgery) where passive, tension-free wound closure is fundamental for wound healing and a successful functional and esthetic outcome. By means of a series of incisions, buccal and lingual flaps are split several times; this results in a double-partial thickness flap and a coronally positioned palatal sliding flap, respectively. Thus, several tissue layers are obtained and the passive advancement of flaps becomes possible for the coverage of augmented areas. Wound closure with microsurgical suture material is accomplished in a multilayer approach, which ensures adaptation and closure of the outer tissue layers without any tension. Two case reports demonstrate the new plastic periodontal approach.

Divided and Sliding Superficial Temporal Artery Flap for Primary Donor-site Closure

PubMed Central

Sugio, Yuta; Seike, Shien; Hosokawa, Ko

2016-01-01

Summary: Superficial temporal artery (STA) flaps are often used for reconstruction of hair-bearing areas. However, primary closure of the donor site is not easy when the size of the necessary skin island is relatively large. In such cases, skin grafts are needed at the donor site, resulting in baldness. We have solved this issue by applying the divided and sliding flap technique, which was first reported for primary donor-site closure of a latissimus dorsi musculocutaneous flap. We applied this technique to the hair-bearing STA flap, where primary donor-site closure is extremely beneficial for preventing baldness consequent to skin grafting. The STA flap was divided into 3, and creation of large flap was possible. Therefore, we concluded that the divided and sliding STA flap could at least partially solve the donor-site problem. Although further investigation is necessary to validate the maximum possible flap size, this technique may be applicable to at least small defects that are common after skin cancer ablation or trauma. PMID:27975020

The hydraulic limitation hypothesis revisited.

PubMed

Ryan, Michael G; Phillips, Nathan; Bond, Barbara J

2006-03-01

We proposed the hydraulic limitation hypothesis (HLH) as a mechanism to explain universal patterns in tree height, and tree and stand biomass growth: height growth slows down as trees grow taller, maximum height is lower for trees of the same species on resource-poor sites and annual wood production declines after canopy closure for even-aged forests. Our review of 51 studies that measured one or more of the components necessary for testing the hypothesis showed that taller trees differ physiologically from shorter, younger trees. Stomatal conductance to water vapour (g(s)), photosynthesis (A) and leaf-specific hydraulic conductance (K L) are often, but not always, lower in taller trees. Additionally, leaf mass per area is often greater in taller trees, and leaf area:sapwood area ratio changes with tree height. We conclude that hydraulic limitation of gas exchange with increasing tree size is common, but not universal. Where hydraulic limitations to A do occur, no evidence supports the original expectation that hydraulic limitation of carbon assimilation is sufficient to explain observed declines in wood production. Any limit to height or height growth does not appear to be related to the so-called age-related decline in wood production of forests after canopy closure. Future work on this problem should explicitly link leaf or canopy gas exchange with tree and stand growth, and consider a more fundamental assumption: whether tree biomass growth is limited by carbon availability.

75 FR 4528 - Certain Magnesia Carbon Bricks From the People's Republic of China: Alignment of Final...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-28

... determination. See Certain Magnesia Carbon Bricks From the People's Republic of China: Preliminary Negative... circumstances included the Department's partial or full closure during the five-day period after the CVD...

Evolutionary Association of Stomatal Traits with Leaf Vein Density in Paphiopedilum, Orchidaceae

PubMed Central

Sun, Mei; Zhang, Juan-Juan; Cao, Kun-Fang; Hu, Hong

2012-01-01

Background Both leaf attributes and stomatal traits are linked to water economy in land plants. However, it is unclear whether these two components are associated evolutionarily. Methodology/Principal Findings In characterizing the possible effect of phylogeny on leaf attributes and stomatal traits, we hypothesized that a correlated evolution exists between the two. Using a phylogenetic comparative method, we analyzed 14 leaf attributes and stomatal traits for 17 species in Paphiopedilum. Stomatal length (SL), stomatal area (SA), upper cuticular thickness (UCT), and total cuticular thickness (TCT) showed strong phylogenetic conservatism whereas stomatal density (SD) and stomatal index (SI) were significantly convergent. Leaf vein density was correlated with SL and SD whether or not phylogeny was considered. The lower epidermal thickness (LET) was correlated positively with SL, SA, and stomatal width but negatively with SD when phylogeny was not considered. When this phylogenetic influence was factored in, only the significant correlation between SL and LET remained. Conclusion/Significance Our results support the hypothesis for correlated evolution between stomatal traits and vein density in Paphiopedilum. However, they do not provide evidence for an evolutionary association between stomata and leaf thickness. These findings lend insight into the evolution of traits related to water economy for orchids under natural selection. PMID:22768224

Seasonal trend of photosynthetic parameters and stomatal conductance of blue oak (Quercus douglasii) under prolonged summer drought and high temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, L; Baldocchi, DD

2003-09-01

OAK-B135 Understanding seasonal changes in photosynthetic parameters and stomatal conductance is crucial for modeling long-term carbon uptake and energy fluxes of ecosystems. Gas exchange measurements of CO{sub 2} and light response curves on blue oak leaves (Quercus douglasii H. & A.) were conducted weekly throughout the growing season to study the seasonality of photosynthetic capacity (V{sub cmax}) and Ball-Berry slope (m) under prolonged summer drought and high temperature. A leaf photosynthetic model was used to determine V{sub cmax}. There was a pronounced seasonal pattern in V{sub cmax}. The maximum value of V{sub cmax}, 127 {micro}molm{sup -2} s{sup -1},was reached shortlymore » after leaf expansion in early summer, when air temperature was moderate and soil water availability was high. Thereafter, V{sub cmax} declined as the soil water profile became depleted and the trees experienced extreme air temperatures, exceeding 40 C. The decline in V{sub cmax} was gradual in midsummer, however, despite extremely low predawn leaf water potentials ({Psi}{sub pd}, {approx} -4.0 MPa). Overall, temporal changes in V{sub cmax} were well correlated with changes in leaf nitrogen content. During spring leaf development, high rates of leaf dark respiration (R{sub d}, 5-6 {micro}mol m{sup -2} s{sup -1}) were observed. Once a leaf reached maturity, R{sub d} remained low, around 0.5 {micro}mol m{sup -2} s{sup -1}. In contrast to the strong seasonality of V{sub cmax}, m and marginal water cost per unit carbon gain ({partial_derivative}E/{partial_derivative}A) were relatively constant over the season, even when leaf {Psi}{sub pd} dropped to -6.8 MPa. The constancy of {partial_derivative}E/{partial_derivative}A suggests that stomata behaved optimally under severe water-stress conditions. We discuss the implications of our findings in the context of modeling carbon and water vapor exchange between ecosystems and the atmosphere.« less

CO2 sensing and CO2 regulation of stomatal conductance: advances and open questions

PubMed Central

Engineer, Cawas; Hashimoto-Sugimoto, Mimi; Negi, Juntaro; Israelsson-Nordstrom, Maria; Azoulay-Shemer, Tamar; Rappel, Wouter-Jan; Iba, Koh; Schroeder, Julian

2015-01-01

Guard cells form epidermal stomatal gas exchange valves in plants and regulate the aperture of stomatal pores in response to changes in the carbon dioxide (CO2) concentration in leaves. Moreover, the development of stomata is repressed by elevated CO2 in diverse plant species. Evidence suggests that plants can sense CO2 concentration changes via guard cells and via mesophyll tissues in mediating stomatal movements. We review new discoveries and open questions on mechanisms mediating CO2-regulated stomatal movements and CO2 modulation of stomatal development, which together function in CO2-regulation of stomatal conductance and gas exchange in plants. Research in this area is timely in light of the necessity of selecting and developing crop cultivars which perform better in a shifting climate. PMID:26482956

Responses of gas-exchange rates and water relations to annual fluctuations of weather in three species of urban street trees.

PubMed

Osone, Yoko; Kawarasaki, Satoko; Ishida, Atsushi; Kikuchi, Satoshi; Shimizu, Akari; Yazaki, Kenichi; Aikawa, Shin-Ichi; Yamaguchi, Masahiro; Izuta, Takeshi; Matsumoto, Genki I

2014-10-01

The frequency of extreme weather has been rising in recent years. A 3-year study of street trees was undertaken in Tokyo to determine whether: (i) street trees suffer from severe water stress in unusually hot summer; (ii) species respond differently to such climatic fluctuations; and (iii) street trees are also affected by nitrogen (N) deficiency, photoinhibition and aerosol pollution. During the study period (2010-12), midsummers of 2010 and 2012 were unusually hot (2.4-2.8 °C higher maximum temperature than the long-term mean) and dry (6-56% precipitation of the mean). In all species, street trees exhibited substantially decreased photosynthetic rate in the extremely hot summer in 2012 compared with the average summer in 2011. However, because of a more conservative stomatal regulation (stomatal closure at higher leaf water potential) in the hot summer, apparent symptoms of hydraulic failure were not observed in street trees even in 2012. Compared with Prunus × yedoensis and Zelkova serrata, Ginkgo biloba, a gymnosperm, was high in stomatal conductance and midday leaf water potential even under street conditions in the unusually hot summer, suggesting that the species had higher drought resistance than the other species and was less susceptible to urban street conditions. This lower susceptibility might be ascribed to the combination of higher soil-to-leaf hydraulic conductance and more conservative water use. Aside from meteorological conditions, N deficiency affected street trees significantly, whereas photoinhibition and aerosol pollution had little effect. The internal CO2 and δ(13)C suggested that both water and N limited the net photosynthetic rate of street trees simultaneously, but water was more limiting. From these results, we concluded that the potential risk of hydraulic failure caused by climatic extremes could be low in urban street trees in temperate regions. However, the size of the safety margin might be different between species. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Carbon assimilation in Eucalyptus urophylla grown under high atmospheric CO2 concentrations: A proteomics perspective.

PubMed

Santos, Bruna Marques Dos; Balbuena, Tiago Santana

2017-01-06

Photosynthetic organisms may be drastically affected by the future climate projections of a considerable increase in CO 2 concentrations. Growth under a high concentration of CO 2 could stimulate carbon assimilation-especially in C3-type plants. We used a proteomics approach to test the hypothesis of an increase in the abundance of the enzymes involved in carbon assimilation in Eucalyptus urophylla plants grown under conditions of high atmospheric CO 2 . Our strategy allowed the profiling of all Calvin-Benson cycle enzymes and associated protein species. Among the 816 isolated proteins, those involved in carbon fixation were found to be the most abundant ones. An increase in the abundance of six key enzymes out of the eleven core enzymes involved in carbon fixation was detected in plants grown at a high CO 2 concentration. Proteome changes were corroborated by the detection of a decrease in the stomatal aperture and in the vascular bundle area in Eucalyptus urophylla plantlets grown in an environment of high atmospheric CO 2 . Our proteomics approach indicates a positive metabolic response regarding carbon fixation in a CO 2 -enriched atmosphere. The slight but significant increase in the abundance of the Calvin enzymes suggests that stomatal closure did not prevent an increase in the carbon assimilation rates. The sample enrichment strategy and data analysis used here enabled the identification of all enzymes and most protein isoforms involved in the Calvin-Benson-Bessham cycle in Eucalyptus urophylla. Upon growth in CO 2 -enriched chambers, Eucalyptus urophylla plantlets responded by reducing the vascular bundle area and stomatal aperture size and by increasing the abundance of six of the eleven core enzymes involved in carbon fixation. Our proteome approach provides an estimate on how a commercially important C3-type plant would respond to an increase in CO 2 concentrations. Additionally, confirmation at the protein level of the predicted genes involved in carbon assimilation may be used in plant transformation strategies aiming to increase plant adaptability to climate changes or to increase plant productivity. Copyright © 2016 Elsevier B.V. All rights reserved.

Co-ordination of physiological and morphological responses of stomata to elevated [CO2] in vascular plants.

PubMed

Haworth, Matthew; Elliott-Kingston, Caroline; McElwain, Jennifer C

2013-01-01

Plant stomata display a wide range of short-term behavioural and long-term morphological responses to atmospheric carbon dioxide concentration ([CO(2)]). The diversity of responses suggests that plants may have different strategies for controlling gas exchange, yet it is not known whether these strategies are co-ordinated in some way. Here, we test the hypothesis that there is co-ordination of physiological (via aperture change) and morphological (via stomatal density change) control of gas exchange by plants. We examined the response of stomatal conductance (G(s)) to instantaneous changes in external [CO(2)] (C(a)) in an evolutionary cross-section of vascular plants grown in atmospheres of elevated [CO(2)] (1,500 ppm) and sub-ambient [O(2)] (13.0 %) compared to control conditions (380 ppm CO(2), 20.9 % O(2)). We found that active control of stomatal aperture to [CO(2)] above current ambient levels was not restricted to angiosperms, occurring in the gymnosperms Lepidozamia peroffskyana and Nageia nagi. The angiosperm species analysed appeared to possess a greater respiratory demand for stomatal movement than gymnosperm species displaying active stomatal control. Those species with little or no control of stomatal aperture (termed passive) to C(a) were more likely to exhibit a reduction in stomatal density than species with active stomatal control when grown in atmospheres of elevated [CO(2)]. The relationship between the degree of stomatal aperture control to C(a) above ambient and the extent of any reduction in stomatal density may suggest the co-ordination of physiological and morphological responses of stomata to [CO(2)] in the optimisation of water use efficiency. This trade-off between stomatal control strategies may have developed due to selective pressures exerted by the costs associated with passive and active stomatal control.

Data-driven non-Markovian closure models

NASA Astrophysics Data System (ADS)

Kondrashov, Dmitri; Chekroun, Mickaël D.; Ghil, Michael

2015-03-01

This paper has two interrelated foci: (i) obtaining stable and efficient data-driven closure models by using a multivariate time series of partial observations from a large-dimensional system; and (ii) comparing these closure models with the optimal closures predicted by the Mori-Zwanzig (MZ) formalism of statistical physics. Multilayer stochastic models (MSMs) are introduced as both a generalization and a time-continuous limit of existing multilevel, regression-based approaches to closure in a data-driven setting; these approaches include empirical model reduction (EMR), as well as more recent multi-layer modeling. It is shown that the multilayer structure of MSMs can provide a natural Markov approximation to the generalized Langevin equation (GLE) of the MZ formalism. A simple correlation-based stopping criterion for an EMR-MSM model is derived to assess how well it approximates the GLE solution. Sufficient conditions are derived on the structure of the nonlinear cross-interactions between the constitutive layers of a given MSM to guarantee the existence of a global random attractor. This existence ensures that no blow-up can occur for a broad class of MSM applications, a class that includes non-polynomial predictors and nonlinearities that do not necessarily preserve quadratic energy invariants. The EMR-MSM methodology is first applied to a conceptual, nonlinear, stochastic climate model of coupled slow and fast variables, in which only slow variables are observed. It is shown that the resulting closure model with energy-conserving nonlinearities efficiently captures the main statistical features of the slow variables, even when there is no formal scale separation and the fast variables are quite energetic. Second, an MSM is shown to successfully reproduce the statistics of a partially observed, generalized Lotka-Volterra model of population dynamics in its chaotic regime. The challenges here include the rarity of strange attractors in the model's parameter space and the existence of multiple attractor basins with fractal boundaries. The positivity constraint on the solutions' components replaces here the quadratic-energy-preserving constraint of fluid-flow problems and it successfully prevents blow-up.

Computational Modeling and Simulation of Genital Tubercle ...

EPA Pesticide Factsheets

Hypospadias is a developmental defect of urethral tube closure that has a complex etiology. Here, we describe a multicellular agent-based model of genital tubercle development that simulates urethrogenesis from the urethral plate stage to urethral tube closure in differentiating male embryos. The model, constructed in CompuCell3D, implemented spatially dynamic signals from SHH, FGF10, and androgen signaling pathways. These signals modulated stochastic cell behaviors, such as differential adhesion, cell motility, proliferation, and apoptosis. Urethral tube closure was an emergent property of the model that was quantitatively dependent on SHH and FGF10 induced effects on mesenchymal proliferation and endodermal apoptosis, ultimately linked to androgen signaling. In the absence of androgenization, simulated genital tubercle development defaulted to the female condition. Intermediate phenotypes associated with partial androgen deficiency resulted in incomplete closure. Using this computer model, complex relationships between urethral tube closure defects and disruption of underlying signaling pathways could be probed theoretically in multiplex disturbance scenarios and modeled into probabilistic predictions for individual risk for hypospadias and potentially other developmental defects of the male genital tubercle. We identify the minimal molecular network that determines the outcome of male genital tubercle development in mice.

Turbulence modeling of gas-solid suspension flows

NASA Technical Reports Server (NTRS)

Chen, C. P.

1988-01-01

The purpose here is to discuss and review advances in two-phase turbulent modeling techniques and their applications in various gas-solid suspension flow situations. In addition to the turbulence closures, heat transfer effect, particle dispersion and wall effects are partially covered.

Organ-specific effects of brassinosteroids on stomatal production coordinate with the action of Too Many Mouths.

PubMed

Wang, Ming; Yang, Kezhen; Le, Jie

2015-03-01

In Arabidopsis, stomatal development initiates after protodermal cells acquire stomatal lineage cell fate. Stomata or their precursors communicate with their neighbor epidermal cells to ensure the "one cell spacing" rule. The signals from EPF/EPFL peptide ligands received by Too Many Mouths (TMM) and ERECTA-family receptors are supposed to be transduced by YODA MAPK cascade. A basic helix-loop-helix transcription factor SPEECHLESS (SPCH) is another key regulator of stomatal cell fate determination and asymmetric entry divisions, and SPCH activity is regulated by YODA MAPK cascade. Brassinosteroid (BR) signaling, one of the most well characterized signal transduction pathways in plants, contributes to the control of stomatal production. But opposite organ-specific effects of BR on stomatal production were reported. Here we confirm that stomatal production in hypocotyls is controlled by BR levels. YODA and CYCD4 are not essential for BR stomata-promoting function. Furthermore, we found that BR could confer tmm hypocotyls clustered stomatal phenotype, indicating that the BR organ-specific effects on stomatal production might coordinate with the TMM organ-specific actions. © 2014 Institute of Botany, Chinese Academy of Sciences.

The mechanics of delamination in fiber-reinforced composite materials. Part 1: Stress singularities and solution structure

NASA Technical Reports Server (NTRS)

Wang, S. S.; Choi, I.

1983-01-01

The fundamental mechanics of delamination in fiber composite laminates is studied. Mathematical formulation of the problem is based on laminate anisotropic elasticity theory and interlaminar fracture mechanics concepts. Stress singularities and complete solution structures associated with general composite delaminations are determined. For a fully open delamination with traction-free surfaces, oscillatory stress singularities always appear, leading to physically inadmissible field solutions. A refined model is introduced by considering a partially closed delamination with crack surfaces in finite-length contact. Stress singularities associated with a partially closed delamination having frictional crack-surface contact are determined, and are found to be diferent from the inverse square-root one of the frictionless-contact case. In the case of a delamination with very small area of crack closure, a simplified model having a square-root stress singularity is employed by taking the limit of the partially closed delamination. The possible presence of logarithmic-type stress singularity is examined; no logarithmic singularity of any kind is found in the composite delamination problem. Numerical examples of dominant stress singularities are shown for delaminations having crack-tip closure with different frictional coefficients between general (1) and (2) graphite-epoxy composites.

Stomatal Blue Light Response Is Present in Early Vascular Plants.

PubMed

Doi, Michio; Kitagawa, Yuki; Shimazaki, Ken-ichiro

2015-10-01

Light is a major environmental factor required for stomatal opening. Blue light (BL) induces stomatal opening in higher plants as a signal under the photosynthetic active radiation. The stomatal BL response is not present in the fern species of Polypodiopsida. The acquisition of a stomatal BL response might provide competitive advantages in both the uptake of CO2 and prevention of water loss with the ability to rapidly open and close stomata. We surveyed the stomatal opening in response to strong red light (RL) and weak BL under the RL with gas exchange technique in a diverse selection of plant species from euphyllophytes, including spermatophytes and monilophytes, to lycophytes. We showed the presence of RL-induced stomatal opening in most of these species and found that the BL responses operated in all euphyllophytes except Polypodiopsida. We also confirmed that the stomatal opening in lycophytes, the early vascular plants, is driven by plasma membrane proton-translocating adenosine triphosphatase and K(+) accumulation in guard cells, which is the same mechanism operating in stomata of angiosperms. These results suggest that the early vascular plants respond to both RL and BL and actively regulate stomatal aperture. We also found three plant species that absolutely require BL for both stomatal opening and photosynthetic CO2 fixation, including a gymnosperm, C. revoluta, and the ferns Equisetum hyemale and Psilotum nudum. © 2015 American Society of Plant Biologists. All Rights Reserved.

Stomatal Spacing Safeguards Stomatal Dynamics by Facilitating Guard Cell Ion Transport Independent of the Epidermal Solute Reservoir12[CC-BY

PubMed Central

Papanatsiou, Maria; Amtmann, Anna

2016-01-01

Stomata enable gaseous exchange between the interior of the leaf and the atmosphere through the stomatal pore. Control of the pore aperture depends on osmotic solute accumulation by, and its loss from the guard cells surrounding the pore. Stomata in most plants are separated by at least one epidermal cell, and this spacing is thought to enhance stomatal function, although there are several genera that exhibit stomata in clusters. We made use of Arabidopsis (Arabidopsis thaliana) stomatal patterning mutants to explore the impact of clustering on guard cell dynamics, gas exchange, and ion transport of guard cells. These studies showed that stomatal clustering in the Arabidopsis too many mouths (tmm1) mutant suppressed stomatal movements and affected CO2 assimilation and transpiration differentially between dark and light conditions and were associated with alterations in K+ channel gating. These changes were consistent with the impaired dynamics of tmm1 stomata and were accompanied by a reduced accumulation of K+ ions in the guard cells. Our findings underline the significance of spacing for stomatal dynamics. While stomatal spacing may be important as a reservoir for K+ and other ions to facilitate stomatal movements, the effects on channel gating, and by inference on K+ accumulation, cannot be explained on the basis of a reduced number of epidermal cells facilitating ion supply to the guard cells. PMID:27406168

Contrasting responses of leaf stomatal characteristics to climate change: a considerable challenge to predict carbon and water cycles.

PubMed

Yan, Weiming; Zhong, Yangquanwei; Shangguan, Zhouping

2017-09-01

Stomata control the cycling of water and carbon between plants and the atmosphere; however, no consistent conclusions have been drawn regarding the response of stomatal frequency to climate change. Here, we conducted a meta-analysis of 1854 globally obtained data series to determine the response of stomatal frequency to climate change, which including four plant life forms (over 900 species), at altitudes ranging from 0 to 4500 m and over a time span of more than one hundred thousand years. Stomatal frequency decreased with increasing CO 2 concentration and increased with elevated temperature and drought stress; it was also dependent on the species and experimental conditions. The response of stomatal frequency to climate change showed a trade-off between stomatal control strategies and environmental factors, such as the CO 2 concentration, temperature, and soil water availability. Moreover, threshold effects of elevated CO 2 and temperature on stomatal frequency were detected, indicating that the response of stomatal density to increasing CO 2 concentration will decrease over the next few years. The results also suggested that the stomatal index may be more reliable than stomatal density for determination of the historic CO 2 concentration. Our findings indicate that the contrasting responses of stomata to climate change bring a considerable challenge in predicting future water and carbon cycles. © 2017 John Wiley & Sons Ltd.

Drought limitations to leaf-level gas exchange: results from a model linking stomatal optimization and cohesion-tension theory.

PubMed

Novick, Kimberly A; Miniat, Chelcy F; Vose, James M

2016-03-01

We merge concepts from stomatal optimization theory and cohesion-tension theory to examine the dynamics of three mechanisms that are potentially limiting to leaf-level gas exchange in trees during drought: (1) a 'demand limitation' driven by an assumption of optimal stomatal functioning; (2) 'hydraulic limitation' of water movement from the roots to the leaves; and (3) 'non-stomatal' limitations imposed by declining leaf water status within the leaf. Model results suggest that species-specific 'economics' of stomatal behaviour may play an important role in differentiating species along the continuum of isohydric to anisohydric behaviour; specifically, we show that non-stomatal and demand limitations may reduce stomatal conductance and increase leaf water potential, promoting wide safety margins characteristic of isohydric species. We used model results to develop a diagnostic framework to identify the most likely limiting mechanism to stomatal functioning during drought and showed that many of those features were commonly observed in field observations of tree water use dynamics. Direct comparisons of modelled and measured stomatal conductance further indicated that non-stomatal and demand limitations reproduced observed patterns of tree water use well for an isohydric species but that a hydraulic limitation likely applies in the case of an anisohydric species. Published 2015. This article is a US Government work and is in the public domain in the USA.

Stomatal Opening in Isolated Epidermal Strips of Vicia faba. I. Response to Light and to CO2-free Air 1

PubMed Central

Fischer, R. A.

1968-01-01

This paper reports a consistent and large opening response to light + CO2-free air in living stomata of isolated epidermal strips of Vicia faba. The response was compared to that of non-isolated stomata in leaf discs floating on water; stomatal apertures, guard cell solute potentials and starch contents were similar in the 2 situations. To obtain such stomatal behavior, it was necessary to float epidermal strips on dilute KCl solutions. This suggests that solute uptake is necessary for stomatal opening. The demonstration of normal stomatal behavior in isolated epidermal strips provides a very useful system in which to investigate the mechanism of stomatal opening. It was possible to show independent responses in stomatal aperture to light and to CO2-free air. PMID:16656995

Recovery of Physiological Traits in Saplings of Invasive Bischofia Tree Compared with Three Species Native to the Bonin Islands under Successive Drought and Irrigation Cycles

PubMed Central

Yazaki, Kenichi; Kuroda, Katsushi; Nakano, Takashi; Kitao, Mitsutoshi; Tobita, Hiroyuki; Ogasa, Mayumi Y.; Ishida, Atsushi

2015-01-01

Partial leaf shedding induced by hydraulic failure under prolonged drought can prevent excess water consumption, resulting in delayed recovery of carbon productivity following rainfall. To understand the manner of water use of invasive species in oceanic island forests under a fluctuating water regime, leaf shedding, multiple physiological traits, and the progress of embolism in the stem xylem under repeated drought-irrigation cycles were examined in the potted saplings of an invasive species, Bischofia javanica Blume, and three endemic native species, Schima mertensiana (Sieb. Et Zucc,) Koitz., Hibiscus glaber Matsum, and Distylium lepidotum Nakai, from the Bonin Islands, Japan. The progress of xylem embolism was observed by cryo-scanning electron microscopy. The samples exhibited different processes of water saving and drought tolerance based on the different combinations of partial leaf shedding involved in embolized conduits following repeated de-rehydration. Predawn leaf water potential largely decreased with each successive drought-irrigation cycle for all tree species, except for B. javanica. B. javanica shed leaves conspicuously under drought and showed responsive stomatal conductance to VPD, which contributed to recover leaf gas exchange in the remaining leaves, following a restored water supply. In contrast, native tree species did not completely recover photosynthetic rates during the repeated drought-irrigation cycles. H. glaber and D. lepidotum preserved water in vessels and adjusted leaf osmotic rates but did not actively shed leaves. S. mertensiana exhibited partial leaf shedding during the first cycle with an osmotic adjustment, but they showed less responsive stomatal conductance to VPD. Our data indicate that invasive B. javanica saplings can effectively use water supplied suddenly under drought conditions. We predict that fluctuating precipitation in the future may change tree distributions even in mesic or moist sites in the Bonin Islands. PMID:26291326

Recovery of Physiological Traits in Saplings of Invasive Bischofia Tree Compared with Three Species Native to the Bonin Islands under Successive Drought and Irrigation Cycles.

PubMed

Yazaki, Kenichi; Kuroda, Katsushi; Nakano, Takashi; Kitao, Mitsutoshi; Tobita, Hiroyuki; Ogasa, Mayumi Y; Ishida, Atsushi

2015-01-01

Partial leaf shedding induced by hydraulic failure under prolonged drought can prevent excess water consumption, resulting in delayed recovery of carbon productivity following rainfall. To understand the manner of water use of invasive species in oceanic island forests under a fluctuating water regime, leaf shedding, multiple physiological traits, and the progress of embolism in the stem xylem under repeated drought-irrigation cycles were examined in the potted saplings of an invasive species, Bischofia javanica Blume, and three endemic native species, Schima mertensiana (Sieb. Et Zucc,) Koitz., Hibiscus glaber Matsum, and Distylium lepidotum Nakai, from the Bonin Islands, Japan. The progress of xylem embolism was observed by cryo-scanning electron microscopy. The samples exhibited different processes of water saving and drought tolerance based on the different combinations of partial leaf shedding involved in embolized conduits following repeated de-rehydration. Predawn leaf water potential largely decreased with each successive drought-irrigation cycle for all tree species, except for B. javanica. B. javanica shed leaves conspicuously under drought and showed responsive stomatal conductance to VPD, which contributed to recover leaf gas exchange in the remaining leaves, following a restored water supply. In contrast, native tree species did not completely recover photosynthetic rates during the repeated drought-irrigation cycles. H. glaber and D. lepidotum preserved water in vessels and adjusted leaf osmotic rates but did not actively shed leaves. S. mertensiana exhibited partial leaf shedding during the first cycle with an osmotic adjustment, but they showed less responsive stomatal conductance to VPD. Our data indicate that invasive B. javanica saplings can effectively use water supplied suddenly under drought conditions. We predict that fluctuating precipitation in the future may change tree distributions even in mesic or moist sites in the Bonin Islands.

Functional characterization of blue-light-induced responses and PHOTOTROPIN 1 gene in Welwitschia mirabilis.

PubMed

Ishishita, Kazuhiro; Suetsugu, Noriyuki; Hirose, Yuki; Higa, Takeshi; Doi, Michio; Wada, Masamitsu; Matsushita, Tomonao; Gotoh, Eiji

2016-03-01

The blue light (BL) receptor phototropin (phot) is specifically found in green plants; it regulates various BL-induced responses such as phototropism, chloroplast movement, stomatal opening, and leaf flattening. In Arabidopsis thaliana, two phototropins--phot1 and phot2--respond to blue light in overlapping but distinct ways. These BL-receptor-mediated responses enhance the photosynthetic activity of plants under weak light and minimize photodamage under strong light conditions. Welwitschia mirabilis Hook.f. found in the Namib Desert, and it has adapted to severe environmental stresses such as limiting water and strong sunlight. Although the plant has physiologically and ecologically unique features, it is unknown whether phototropin is functional in this plant. In this study, we assessed the functioning of phot-mediated BL responses in W. mirabilis. BL-dependent phototropism and stomatal opening was observed but light-dependent chloroplast movement was not detected. We performed a functional analysis of the PHOT1 gene of W. mirabilis, WmPHOT1, in Arabidopsis thaliana. We generated transgenic A. thaliana lines expressing WmPHOT1 in a phot1 phot2 double mutant background. Several Wmphot1 transgenic plants showed normal growth, although phot1 phot2 double mutant plants showed stunted growth. Furthermore, Wmphot1 transgenic plants showed normal phot1-mediated responses including phototropism, chloroplast accumulation, stomatal opening, and leaf flattening, but lacked the chloroplast avoidance response that is specifically mediated by phot2. Thus, our findings indicate that W. mirabilis possesses typical phot-mediated BL responses that were at least partially mediated by functional phototropin 1, an ortholog of Atphot1.

Photosynthesis Decrease and Stomatal Control of Gas Exchange in Abies alba Mill. in Response to Vapor Pressure Difference.

PubMed

Guehl, J M; Aussenac, G

1987-02-01

The responses of steady state CO(2) assimilation rate (A), transpiration rate (E), and stomatal conductance (g(s)) to changes in leaf-to-air vapor pressure difference (DeltaW) were examined on different dates in shoots from Abies alba trees growing outside. In Ecouves, a provenance representative of wet oceanic conditions in Northern France, both A and g(s) decreased when DeltaW was increased from 4.6 to 14.5 Pa KPa(-1). In Nebias, which represented the dry end of the natural range of A. alba in southern France, A and g(s) decreased only after reaching peak levels at 9.0 and 7.0 Pa KPa(-1), respectively. The representation of the data in assimilation rate (A) versus intercellular CO(2) partial pressure (C(i)) graphs allowed us to determine how stomata and mesophyll photosynthesis interacted when DeltaW was increased. Changes in A were primarily due to alterations in mesophyll photosynthesis. At high DeltaW, and especially in Ecouves when soil water deficit prevailed, A declined, while C(i) remained approximately constant, which may be interpreted as an adjustment of g(s) to changes in mesophyll photosynthesis. Such a stomatal control of gas exchange appeared as an alternative to the classical feedforward interpretation of E versus DeltaW responses with a peak rate of E. The gas exchange response to DeltaW was also characterized by considerable deviations from the optimization theory of IR Cowan and GD Farquhar (1977 Symp Soc Exp Biol 31: 471-505).

Overexpression of an Arabidopsis cysteine-rich receptor-like protein kinase, CRK5, enhances abscisic acid sensitivity and confers drought tolerance.

PubMed

Lu, Kai; Liang, Shan; Wu, Zhen; Bi, Chao; Yu, Yong-Tao; Wang, Xiao-Fang; Zhang, Da-Peng

2016-09-01

Receptor-like kinases (RLKs) have been reported to regulate many developmental and defense process, but only a few members have been functionally characterized. In the present study, our observations suggest that one of the RLKs, a membrane-localized cysteine-rich receptor-like protein kinase, CRK5, is involved in abscisic acid (ABA) signaling in Arabidopsis thaliana Overexpression of CRK5 increases ABA sensitivity in ABA-induced early seedling growth arrest and promotion of stomatal closure and inhibition of stomatal opening. Interestingly, and importantly, overexpression of CRK5 enhances plant drought tolerance without affecting plant growth at the mature stages and plant productivity. Transgenic lines overexpressing a mutated form of CRK5, CRK5 (K372E) with the change of the 372nd conserved amino acid residue from lysine to glutamic acid in its kinase domain, result in wild-type ABA and drought responses, supporting the role of CRK5 in ABA signaling. The loss-of-function mutation of the CRK5 gene does not affect the ABA response, while overexpression of two homologs of CRK5, CRK4 and CRK19, confers ABA responses, suggesting that these CRK members function redundantly. We further showed that WRKY18, WRKY40 and WRKY60 transcription factors repress the expression of CRK5, and that CRK5 likely functions upstream of ABI2 in ABA signaling. These findings help in understanding the complex ABA signaling network. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Impacts of seasonal air and soil temperatures on photosynthesis in Scots pine trees.

PubMed

Strand, Martin; Lundmark, Tomas; Söderbergh, Ingrid; Mellander, Per-Erik

2002-08-01

Seasonal courses of light-saturated rate of net photosynthesis (A360) and stomatal conductance (gs) were examined in detached 1-year-old needles of Scots pine (Pinus sylvestris L.) from early April to mid-November. To evaluate the effects of soil frost and low soil temperatures on gas exchange, the extent and duration of soil frost, as well as the onset of soil warming, were manipulated in the field. During spring, early summer and autumn, the patterns of A360 and gs in needles from the control and warm-soil plots were generally strongly related to daily mean air temperatures and the frequency of severe frost. The warm-soil treatment had little effect on gas exchange, although mean soil temperature in the warm-soil plot was 3.8 degrees C higher than in the control plot during spring and summer, indicating that A360 and gs in needles from control trees were not limited by low soil temperature alone. In contrast, prolonged exposure to soil temperatures slightly above 0 degrees C severely restricted recovery of A360 and especially gs in needles from the cold-soil treatment during spring and early summer; however, full recovery of both A360 and gs occurred in late summer. We conclude that inhibition of A360 by low soil temperatures is related to both stomatal closure and effects on the biochemistry of photosynthesis, the relative importance of which appeared to vary during spring and early summer. During the autumn, soil temperatures as low as 8 degrees C did not affect either A360 or gs.

Over-expression of LeNCED1 in tomato (Solanum lycopersicum L.) with the rbcS3C promoter allows recovery of lines that accumulate very high levels of abscisic acid and exhibit severe phenotypes.

PubMed

Tung, Swee Ang; Smeeton, Rachel; White, Charlotte A; Black, Colin R; Taylor, Ian B; Hilton, Howard W; Thompson, Andrew J

2008-07-01

Previous work where 9-cis-epoxycarotenoid dioxygenase (NCED) was over-expressed using the constitutive Gelvin Superpromoter resulted in mild increases in abscisic acid (ABA) accumulation, accompanied by stomatal closure and increased water-use efficiency (WUE), but with apparently little impact on long-term biomass production. However, one of the negative effects of the over-expression of NCED using constitutive promoters in tomato was increased seed dormancy. Here we report the use of the rbcS3C promoter, from a gene encoding the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), to drive LeNCED1 transgene expression in tomato in a light-responsive and circadian manner. In comparison to the constitutive promoter, the rbcS3C promoter allowed the generation of transgenic plants with much higher levels of ABA accumulation in leaves and sap, but the effect on seed dormancy was diminished. These plants displayed the expected reductions in stomatal conductance and CO(2) assimilation, but they also exhibited a severe set of symptoms that included perturbed cotyledon release from the testa, increased photobleaching in young seedlings, substantially reduced chlorophyll and carotenoid content, interveinal leaf flooding, and greatly reduced growth. These symptoms illustrate adverse consequences of long-term, very high ABA accumulation. Only more moderate increases in ABA biosynthesis are likely to be useful in the context of agriculture. Implications are discussed for the design of transgenic 'high ABA' plants that exhibit increased WUE but have minimal negative phenotypic effects.

Herb Hydraulics: Inter- and Intraspecific Variation in Three Ranunculus Species.

PubMed

Nolf, Markus; Rosani, Andrea; Ganthaler, Andrea; Beikircher, Barbara; Mayr, Stefan

2016-04-01

The requirements of the water transport system of small herbaceous species differ considerably from those of woody species. Despite their ecological importance for many biomes, knowledge regarding herb hydraulics remains very limited. We compared key hydraulic features (vulnerability to drought-induced hydraulic decline, pressure-volume relations, onset of cellular damage, in situ variation of water potential, and stomatal conductance) of three Ranunculus species differing in their soil humidity preferences and ecological amplitude. All species were very vulnerable to water stress (50% reduction in whole-leaf hydraulic conductance [kleaf] at -0.2 to -0.8 MPa). In species with narrow ecological amplitude, the drought-exposed Ranunculus bulbosus was less vulnerable to desiccation (analyzed via loss of kleaf and turgor loss point) than the humid-habitat Ranunculus lanuginosus Accordingly, water stress-exposed plants from the broad-amplitude Ranunculus acris revealed tendencies toward lower vulnerability to water stress (e.g. osmotic potential at full turgor, cell damage, and stomatal closure) than conspecific plants from the humid site. We show that small herbs can adjust to their habitat conditions on interspecific and intraspecific levels in various hydraulic parameters. The coordination of hydraulic thresholds (50% and 88% loss of kleaf, turgor loss point, and minimum in situ water potential) enabled the study species to avoid hydraulic failure and damage to living cells. Reversible recovery of hydraulic conductance, desiccation-tolerant seeds, or rhizomes may allow them to prioritize toward a more efficient but vulnerable water transport system while avoiding the severe effects that water stress poses on woody species. © 2016 American Society of Plant Biologists. All Rights Reserved.

Herb Hydraulics: Inter- and Intraspecific Variation in Three Ranunculus Species1[OPEN

PubMed Central

Ganthaler, Andrea; Beikircher, Barbara

2016-01-01

The requirements of the water transport system of small herbaceous species differ considerably from those of woody species. Despite their ecological importance for many biomes, knowledge regarding herb hydraulics remains very limited. We compared key hydraulic features (vulnerability to drought-induced hydraulic decline, pressure-volume relations, onset of cellular damage, in situ variation of water potential, and stomatal conductance) of three Ranunculus species differing in their soil humidity preferences and ecological amplitude. All species were very vulnerable to water stress (50% reduction in whole-leaf hydraulic conductance [kleaf] at −0.2 to −0.8 MPa). In species with narrow ecological amplitude, the drought-exposed Ranunculus bulbosus was less vulnerable to desiccation (analyzed via loss of kleaf and turgor loss point) than the humid-habitat Ranunculus lanuginosus. Accordingly, water stress-exposed plants from the broad-amplitude Ranunculus acris revealed tendencies toward lower vulnerability to water stress (e.g. osmotic potential at full turgor, cell damage, and stomatal closure) than conspecific plants from the humid site. We show that small herbs can adjust to their habitat conditions on interspecific and intraspecific levels in various hydraulic parameters. The coordination of hydraulic thresholds (50% and 88% loss of kleaf, turgor loss point, and minimum in situ water potential) enabled the study species to avoid hydraulic failure and damage to living cells. Reversible recovery of hydraulic conductance, desiccation-tolerant seeds, or rhizomes may allow them to prioritize toward a more efficient but vulnerable water transport system while avoiding the severe effects that water stress poses on woody species. PMID:26896395

Gas exchange and hydraulics in seedlings of Hevea brasiliensis during water stress and recovery.

PubMed

Chen, Jun-Wen; Zhang, Qiang; Li, Xiao-Shuang; Cao, Kun-Fang

2010-07-01

The response of plants to drought has received significant attention, but far less attention has been given to the dynamic response of plants during recovery from drought. Photosynthetic performance and hydraulic capacity were monitored in seedlings of Hevea brasiliensis under water stress and during recovery following rewatering. Leaf water relation, gas exchange rate and hydraulic conductivity decreased gradually after water stress fell below a threshold, whereas instantaneous water use efficiency and osmolytes increased significantly. After 5 days of rewatering, leaf water relation, maximum stomatal conductance (g(s-max)) and plant hydraulic conductivity had recovered to the control levels except for sapwood area-specific hydraulic conductivity, photosynthetic assimilation rate and osmolytes. During the phase of water stress, stomata were almost completely closed before water transport efficiency decreased substantially, and moreover, the leaf hydraulic pathway was more vulnerable to water stress-induced embolism than the stem hydraulic pathway. Meanwhile, g(s-max) was linearly correlated with hydraulic capacity when water stress exceeded a threshold. In addition, a positive relationship was shown to occur between the recovery of g(s-max) and of hydraulic capacity during the phase of rewatering. Our results suggest (i) that stomatal closure effectively reduces the risk of xylem dysfunction in water-stressed plants at the cost of gas exchange, (ii) that the leaf functions as a safety valve to protect the hydraulic pathway from water stress-induced dysfunction to a larger extent than does the stem and (iii) that the full drought recovery of gas exchange is restricted by not only hydraulic factors but also non-hydraulic factors.

The barley anion channel, HvALMT1, has multiple roles in guard cell physiology and grain metabolism.

PubMed

Xu, Muyun; Gruber, Benjamin D; Delhaize, Emmanuel; White, Rosemary G; James, Richard A; You, Jiangfeng; Yang, Zhenming; Ryan, Peter R

2015-01-01

The barley (Hordeum vulgare) gene HvALMT1 encodes an anion channel in guard cells and in certain root tissues indicating that it may perform multiple roles. The protein localizes to the plasma membrane and facilitates malate efflux from cells when constitutively expressed in barley plants and Xenopus oocytes. This study investigated the function of HvALMT1 further by identifying its tissue-specific expression and by generating and characterizing RNAi lines with reduced HvALMT1 expression. We show that transgenic plants with 18-30% of wild-type HvALMT1 expression had impaired guard cell function. They maintained higher stomatal conductance in low light intensity and lost water more rapidly from excised leaves than the null segregant control plants. Tissue-specific expression of HvALMT1 was investigated in developing grain and during germination using transgenic barley lines expressing the green fluorescent protein (GFP) with the HvALMT1 promoter. We found that HvALMT1 is expressed in the nucellar projection, the aleurone layer and the scutellum of developing barley grain. Malate release measured from isolated aleurone layers prepared from imbibed grain was significantly lower in the RNAi barley plants compared with control plants. These data provide molecular and physiological evidence that HvALMT1 functions in guard cells, in grain development and during germination. We propose that HvALMT1 releases malate and perhaps other anions from guard cells to promote stomatal closure. The likely roles of HvALMT1 during seed development and grain germination are also discussed. © 2014 Scandinavian Plant Physiology Society.

Photosynthetic response to low sink demand after fruit removal in relation to photoinhibition and photoprotection in peach trees.

PubMed

Duan, Wei; Fan, Pei G; Wang, Li J; Li, Wei D; Yan, Shu T; Li, Shao H

2008-01-01

Diurnal variations in photosynthesis, chlorophyll fluorescence, xanthophyll cycle, antioxidant enzymes and antioxidant metabolism in leaves in response to low sink demand caused by fruit removal (-fruit) were studied in 'Zaojiubao' peach (Prunus persica (L.) Batch) trees during the final stage of rapid fruit growth. Compared with the retained fruit treatment (+fruit), the -fruit treatment resulted in a significantly lower photosynthetic rate, stomatal conductance and transpiration rate, but generally higher internal CO(2) concentration, leaf-to-air vapor pressure difference and leaf temperature. The low photosynthetic rate in the -fruit trees paralleled reductions in maximal efficiency of photosystem II (PSII) photochemistry and carboxylation efficiency. The midday depression in photosynthetic rate in response to low sink demand resulting from fruit removal was mainly caused by non-stomatal limitation. Fruit removal resulted in lower quantum efficiency of PSII as a result of both a decrease in the efficiency of excitation capture by open PSII reaction centers and an increase in closure of PSII reaction centers. Both xanthophyll-dependent thermal dissipation and the antioxidant system were up-regulated providing protection from photo-oxidative damage to leaves during low sink demand. Compared with the leaves of +fruit trees, leaves of -fruit trees had a larger xanthophyll cycle pool size and a higher de-epoxidation state, as well as significantly higher activities of antioxidant enzymes, including superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase and a higher reduction state of ascorbate and glutathione. However, the -fruit treatment resulted in higher hydrogen peroxide and malondialdehyde concentrations compared with the +fruit treatment, indicating photo-oxidative damage.

A case of residual inferior sinus venosus defect after ineffective surgical closure.

PubMed

Uga, Sayuri; Hidaka, Takayuki; Takasaki, Taiichi; Kihara, Yasuki

2014-10-03

A 38-year-old woman presented with cyanosis and heart failure 34 years after patch closure of an atrial septal defect and partial anomalous pulmonary venous connection. CT and cardiac catheterisation showed a residual defect that caused right-to-left shunting. The patch almost blocked the inferior vena cava from the right atrium, resulting in uncommon drainage of the inferior vena cava into the left atrium. Other anomalies included the coronary-to-pulmonary artery fistula and duplicate inferior vena cava with dilated azygos venous system. A second surgery was performed, and we confirmed an inferior sinus venosus defect, which is rare and can be misdiagnosed. The ineffective patch closure had caused a haemodynamic status that rarely occurs. We describe the diagnostic process and emphasise the importance of correctly understanding the entity. 2014 BMJ Publishing Group Ltd.

Stomatal Spacing Safeguards Stomatal Dynamics by Facilitating Guard Cell Ion Transport Independent of the Epidermal Solute Reservoir.

PubMed

Papanatsiou, Maria; Amtmann, Anna; Blatt, Michael R

2016-09-01

Stomata enable gaseous exchange between the interior of the leaf and the atmosphere through the stomatal pore. Control of the pore aperture depends on osmotic solute accumulation by, and its loss from the guard cells surrounding the pore. Stomata in most plants are separated by at least one epidermal cell, and this spacing is thought to enhance stomatal function, although there are several genera that exhibit stomata in clusters. We made use of Arabidopsis (Arabidopsis thaliana) stomatal patterning mutants to explore the impact of clustering on guard cell dynamics, gas exchange, and ion transport of guard cells. These studies showed that stomatal clustering in the Arabidopsis too many mouths (tmm1) mutant suppressed stomatal movements and affected CO2 assimilation and transpiration differentially between dark and light conditions and were associated with alterations in K(+) channel gating. These changes were consistent with the impaired dynamics of tmm1 stomata and were accompanied by a reduced accumulation of K(+) ions in the guard cells. Our findings underline the significance of spacing for stomatal dynamics. While stomatal spacing may be important as a reservoir for K(+) and other ions to facilitate stomatal movements, the effects on channel gating, and by inference on K(+) accumulation, cannot be explained on the basis of a reduced number of epidermal cells facilitating ion supply to the guard cells. © 2016 American Society of Plant Biologists. All rights reserved.

Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2- and ABA-induced stomatal closing

PubMed Central

Azoulay-Shemer, Tamar; Palomares, Axxell; Bagheri, Andish; Israelsson-Nordstrom, Maria; Engineer, Cawas B.; Bargmann, Bastiaan O.R.; Stephan, Aaron B.; Schroeder, Julian I.

2015-01-01

SUMMARY Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2]. [CO2] in leaves mediates stomatal movements. The role of guard-cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll-deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard-cell specific enhancer trap-line. Our data show that more than 90% of guard cells were chlorophyll-deficient. Interestingly, approximately ~ 45% of stomata had an unusual, previously not-described, morphology of thin-shaped chlorophyll-less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole-leaf photosynthetic parameters (PSII, qP, qN, FV′/FM′) were comparable to wild-type plants. Time-resolved intact leaf gas exchange analyses showed a reduction in stomatal conductance and carbon assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to [CO2] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO2] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO2] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard-cell CO2 and ABA signal transduction are not directly modulated by guard-cell photosynthesis/electron transport. Moreover, the finding that chlorophyll-less stomata cause a “deflated” thin-shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard-cell turgor production. PMID:26096271

The acclimation of Tilia cordata stomatal opening in response to light, and stomatal anatomy to vegetational shade and its components.

PubMed

Aasamaa, Krõõt; Aphalo, Pedro José

2017-02-01

Stomatal anatomical traits and rapid responses to several components of visible light were measured in Tilia cordata Mill. seedlings grown in an open, fully sunlit field (C-set), or under different kinds of shade. The main questions were: (i) stomatal responses to which visible light spectrum regions are modified by growth-environment shade and (ii) which separate component of vegetational shade is most effective in eliciting the acclimation effects of the full vegetational shade. We found that stomatal opening in response to red or green light did not differ between the plants grown in the different environments. Stomatal response to blue light was increased (in comparison with that of C-set) in the leaves grown in full vegetational shade (IABW-set), in attenuated UVAB irradiance (AB-set) or in decreased light intensity (neutral shade) plus attenuated UVAB irradiance (IAB-set). In all sets, the addition of green light-two or four times stronger-into induction light barely changed the rate of the blue-light-stimulated stomatal opening. In the AB-set, stomatal response to blue light equalled the strong IABW-set response. In attenuated UVB-grown leaves, stomatal response fell midway between IABW- and C-set results. Blue light response by neutral shade-grown leaves did not differ from that of the C-set, and the response by the IAB-set did not differ from that of the AB-set. Stomatal size was not modified by growth environments. Stomatal density and index were remarkably decreased only in the IABW- and IAB-sets. It was concluded that differences in white light responses between T. cordata leaves grown in different light environments are caused only by their different blue light response. Differences in stomatal sensitivity are not dependent on altered stomatal anatomy. Attenuated UVAB irradiance is the most efficient component of vegetational shade in stimulating acclimation of stomata, whereas decreased light intensity plays a minor role. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Modeling stomatal conductance in the earth system: linking leaf water-use efficiency and water transport along the soil-plant-atmosphere continuum

NASA Astrophysics Data System (ADS)

Bonan, G. B.; Williams, M.; Fisher, R. A.; Oleson, K. W.

2014-09-01

The Ball-Berry stomatal conductance model is commonly used in earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must be empirically parameterized. We evaluated the Ball-Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil-plant-atmosphere continuum (SPA). The SPA model simulates stomatal conductance numerically by (1) optimizing photosynthetic carbon gain per unit water loss while (2) constraining stomatal opening to prevent leaf water potential from dropping below a critical minimum. We evaluated two optimization algorithms: intrinsic water-use efficiency (ΔAn /Δgs, the marginal carbon gain of stomatal opening) and water-use efficiency (ΔAn /ΔEl, the marginal carbon gain of transpiration water loss). We implemented the stomatal models in a multi-layer plant canopy model to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using leaf analyses, eddy covariance fluxes at six forest sites, and parameter sensitivity analyses. The primary differences among stomatal models relate to soil moisture stress and vapor pressure deficit responses. Without soil moisture stress, the performance of the SPA stomatal model was comparable to or slightly better than the CLM Ball-Berry model in flux tower simulations, but was significantly better than the CLM Ball-Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from water flow along the soil-to-leaf pathway rather than being imposed a priori, as in the CLM Ball-Berry model. Similar functional dependence of gs on Ds emerged from the ΔAn/ΔEl optimization, but not the ΔAn /gs optimization. Two parameters (stomatal efficiency and root hydraulic conductivity) minimized errors with the SPA stomatal model. The critical stomatal efficiency for optimization (ι) gave results consistent with relationships between maximum An and gs seen in leaf trait data sets and is related to the slope (g1) of the Ball-Berry model. Root hydraulic conductivity (Rr*) was consistent with estimates from literature surveys. The two central concepts embodied in the SPA stomatal model, that plants account for both water-use efficiency and for hydraulic safety in regulating stomatal conductance, imply a notion of optimal plant strategies and provide testable model hypotheses, rather than empirical descriptions of plant behavior.

Prospective experimental study of transrectal viscerotomy closure using transanal endoscopic suture vs. circular stapler: a step toward NOTES.

PubMed

Diana, M; Leroy, J; Wall, J; De Ruijter, V; Lindner, V; Dhumane, P; Mutter, D; Marescaux, J

2012-06-01

Endoluminal full-thickness closure of the rectal wall is critical in emerging procedures including endoscopic submucosal dissection and transrectal natural orifice transluminal endoscopic surgery (NOTES). This study aimed to compare manual suture using the transanal endoscopic operation platform (TEO; Karl Storz, Tüttlingen, Germany) with the end-to-end anastomosis hemorrhoid circular stapler (EEA; Covidien, Dublin, Ireland) for closure of the rectal viscerotomy during transrectal NOTES segmental colectomy. A total of 12 swine underwent transrectal hybrid NOTES partial colectomies. Animals were divided into two groups according to the viscerotomy closure technique: 1) TEO manual suture; 2) EEA circular stapler closure. Mean (± SD) viscerotomy closure time was 67.5 ± 59.5 minutes and 31.5 ± 19.6 minutes for TEO and EEA, respectively. There was one conversion to laparoscopy in the TEO group and a misfiring in the EEA group that required a TEO salvage suture. There was one positive air-leak test in each group. Peritoneal fluid collected at the end of the procedure tested positive for bacterial contamination in all cases. A mild stenosis was present in 4 /6 viscerotomies (67 %) in the TEO group and in 1/6 (17 %) in the EEA group on endoscopic control. Inflammatory changes were mild in 3/5 (60 %) and 4/5 (80 %) viscerotomies in the TEO and EEA groups, respectively, whereas severe inflammation was found in 2/5 (TEO) and 1 /5 (EEA). Transrectal viscerotomy closure using the EEA circular stapler technique is feasible, easy to perform, and histologically comparable to suture closure through a TEO platform. It may offer an attractive alternative for NOTES segmental colectomies and endoscopic resections. © Georg Thieme Verlag KG Stuttgart · New York.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ito, Gen; Kobayashi, Takeshi; Takeda, Yoshie

Highlights: • Proteoglycan from salmon nasal cartridge (SNC-PG) promoted wound healing in fibroblast monolayers. • SNC-PG stimulated both cell proliferation and cell migration. • Interaction between chondroitin sulfate-units and CD44 is responsible for the effect. - Abstract: Proteoglycans (PGs) are involved in various cellular functions including cell growth, adhesion, and differentiation; however, their physiological roles are not fully understood. In this study, we examined the effect of PG purified from salmon nasal cartilage (SNC-PG) on wound closure using tissue-cultured cell monolayers, an in vitro wound-healing assay. The results indicated that SNC-PG significantly promoted wound closure in NIH/3T3 cell monolayers bymore » stimulating both cell proliferation and cell migration. SNC-PG was effective in concentrations from 0.1 to 10 μg/ml, but showed much less effect at higher concentrations (100–1000 μg/ml). The effect of SNC-PG was abolished by chondroitinase ABC, indicating that chondroitin sulfates (CSs), a major component of glycosaminoglycans (GAGs) in SNC-PG, are crucial for the SNC-PG effect. Furthermore, chondroitin 6-sulfate (C-6-S), a major CS of SNC-PG GAGs, could partially reproduce the SNC-PG effect and partially inhibit the binding of SNC-PG to cells, suggesting that SNC-PG exerts its effect through an interaction between the GAGs in SNC-PG and the cell surface. Neutralization by anti-CD44 antibodies or CD44 knockdown abolished SNC-PG binding to the cells and the SNC-PG effect on wound closure. These results suggest that interactions between CS-rich GAG-chains of SNC-PG and CD44 on the cell surface are responsible for the SNC-PG effect on wound closure.« less

Factors associated with the failure of obstetric fistula repair in Guinea: implications for practice.

PubMed

Delamou, Alexandre; Delvaux, Therese; Beavogui, Abdoul Habib; Toure, Abdoulaye; Kolié, Delphin; Sidibé, Sidikiba; Camara, Mandian; Diallo, Kindy; Barry, Thierno Hamidou; Diallo, Moustapha; Leveque, Alain; Zhang, Wei-Hong; De Brouwere, Vincent

2016-11-08

The prevention and treatment of obstetric fistula still remains a concern and a challenge in low income countries. The objective of this study was to estimate the overall proportions of failure of fistula closure and incontinence among women undergoing repair for obstetric fistula in Guinea and identify its associated factors. This was a retrospective cohort study using data extracted from medical records of fistula repairs between 1 January 2012 and 30 September 2013. The outcome was the failure of fistula closure and incontinence at hospital discharge evaluated by a dye test. A sub-sample of women with vesicovaginal fistula was used to identify the factors associated with these outcomes. Overall, 109 women out of 754 (14.5 %; 95 % CI:11.9-17.0) unsuccessful repaired fistula at discharge and 132 (17.5 %; 95 % CI:14.8-20.2) were not continent. Failure of fistula closure was associated with vaginal delivery (AOR: 1.9; 95 % CI: 1.0-3.6), partially (AOR: 2.0; 95 % CI: 1.1-5.6) or totally damaged urethra (AOR: 5.9; 95 % CI: 2.9-12.3) and surgical repair at Jean Paul II Hospital (AOR: 2.5; 95 % CI: 1.2-4.9). Women who had a partially damaged urethra (AOR: 2.5; 95 % CI: 1.5-4.4) or a totally damaged urethra (AOR: 6.3; 95 % CI: 3.0-13.0) were more likely to experience post-repair urinary incontinence than women who had their urethra intact. At programmatic level in Guinea, caution should be paid to the repair of women who present with a damaged urethra and those who delivered vaginally as they carry greater risks of experiencing a failure of fistula closure and incontinence.

Stomatal regulation, structural acclimation and metabolic shift towards defensive compounds reduce O3 load in birch under chronic O3 stress

NASA Astrophysics Data System (ADS)

Oksanen, E.; Riikonen, J.; Kontunen-Soppela, S.; Maenpaa, M.; Rousi, M.

2009-12-01

Northern forests are encountering new threats due to continuously increasing load of oxidative stress, e.g. due to rising tropospheric O3 levels, and simultaneous climate warming, which is more intense in northern latitudes as compared to global means. The proportion of silver birch (Betula pendula) in Finnish forests is expected to increase with climate warming. Unfortunately, we have growing evidence that the vitality and the carbon sink strength of birch trees are weakened under chronic O3 stress. In this study we investigated the effects of slightly elevated O3 concentration (1.3 x the ambient), temperature (T) and their combination on the antioxidant defense, gas exchange and leaf growth of Betula pendula saplings (clone 12) growing in open-field conditions over two growing seasons. The plants were measured for SLA (specific leaf area), total leaf area, net photosynthesis (Pn), stomatal conductance (gs), maximum rate of carboxylation (Vc,max), maximum rate of electron transport (Jmax), relative stomatal limitation to photosynthesis (ls), dark respiration (Rd), apoplastic concentrations of AA (ascorbic acid), DHA (dehydroascobate) and total ascorbate, the redox state of apoplastic ascorbate, and total antioxidant capacity. Elevated O3 enhanced the total antioxidant capacity in the apoplast in the first year of the experiment at the ambient T. However, during the second year of the experiment, the saplings responded to elevated O3 level by closing the stomata and by developing leaves with a lower leaf area per mass, rather than by accumulating ascorbate in the apoplast. O3 did not affect the total leaf area, whereas Pn was slightly and gs significantly reduced in the second year. Elevated T enhanced the total leaf area, Pn and Vc,max, redox state of ascorbate and total antioxidant capacity in the apoplast. The effects of T and O3 on total leaf area and net photosynthesis were counteractive. We were not able to detect significant differences in Rd between the treatments. Our results with birch suggest that (1) apoplastic AA plays only a minor and transient role in O3 defence whereas (2) stomatal regulation and structural plasticity of leaves are more important long-term mechanisms leading to O3 avoidance in chronic O3 stress with relatively low O3 concentrations. The role of antioxidant capacity was, however, modified by temperature in a complex manner. We should also remember that the clonal differences are wide in birch responses to O3 and therefore the role of AA in scavencing ROS in the apoplast maybe more important in other birch genotypes. Our previous studies with O3-stressed birches have indicated a considerable shift in leaf metabolome towards quercetin-phenolic compounds and chlorogenic acid, which have good radical-scavencing properties, and compounds related to leaf cuticular wax layer. Therefore we can conclude that the long-term protection of birch against chronic O3 stress in mainly composed of stomatal closure, secondary compounds and structural acclimation.

The Ecophysiology Of A Pinus Ponderosa Ecosystem Exposed To High Tropospheric Ozone: Implications For Stomatal And Non-Stomatal Ozone Fluxes

NASA Astrophysics Data System (ADS)

Fares, S.; McKay, M.; Goldstein, A.

2008-12-01

Ecosystems remove ozone from the troposphere through both stomatal and non-stomatal deposition. The portion of ozone taken up through stomata has an oxidative effect causing damage. We used a multi-year dataset to assess the physiological controls over ozone deposition. Environmental parameters, CO2 and ozone fluxes were measured continuously from January 2001 to December 2006 above a ponderosa pine plantation near Blodgett Forest, Georgetown, California. We studied the dynamic of NEE (Net Ecosystem Exchange, -838 g C m-2 yr-1) and water evapotranspiration on an annual and daily basis. These processes are tightly coupled to stomatal aperture which also controlled ozone fluxes. High levels of ozone concentrations (~ 100 ppb) were observed during the spring-summer period, with corresponding high levels of ozone fluxes (~ 30 μmol m-2 h-1). During the summer season, a large portion of the total ozone flux was due to non-stomatal processes, and we propose that a plant physiological control, releasing BVOC (Biogenic Volatile Organic Compounds), is mainly responsible. We analyzed the correlations of common ozone exposure metrics based on accumulation of concentrations (AOT40 and SUM0) with ozone fluxes (total, stomatal and non-stomatal). Stomatal flux showed poorer correlation with ozone concentrations than non-stomatal flux during summer and fall seasons, which largely corresponded to the growing period. We therefore suggest that AOT40 and SUM0 are poor predictors of ozone damage and that a physiologically based metric would be more effective.

A steady-state stomatal model of balanced leaf gas exchange, hydraulics and maximal source-sink flux.

PubMed

Hölttä, Teemu; Lintunen, Anna; Chan, Tommy; Mäkelä, Annikki; Nikinmaa, Eero

2017-07-01

Trees must simultaneously balance their CO2 uptake rate via stomata, photosynthesis, the transport rate of sugars and rate of sugar utilization in sinks while maintaining a favourable water and carbon balance. We demonstrate using a numerical model that it is possible to understand stomatal functioning from the viewpoint of maximizing the simultaneous photosynthetic production, phloem transport and sink sugar utilization rate under the limitation that the transpiration-driven hydrostatic pressure gradient sets for those processes. A key feature in our model is that non-stomatal limitations to photosynthesis increase with decreasing leaf water potential and/or increasing leaf sugar concentration and are thus coupled to stomatal conductance. Maximizing the photosynthetic production rate using a numerical steady-state model leads to stomatal behaviour that is able to reproduce the well-known trends of stomatal behaviour in response to, e.g., light, vapour concentration difference, ambient CO2 concentration, soil water status, sink strength and xylem and phloem hydraulic conductance. We show that our results for stomatal behaviour are very similar to the solutions given by the earlier models of stomatal conductance derived solely from gas exchange considerations. Our modelling results also demonstrate how the 'marginal cost of water' in the unified stomatal conductance model and the optimal stomatal model could be related to plant structural and physiological traits, most importantly, the soil-to-leaf hydraulic conductance and soil moisture. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Positive and negative peptide signals control stomatal density.

PubMed

Shimada, Tomoo; Sugano, Shigeo S; Hara-Nishimura, Ikuko

2011-06-01

The stoma is a micro valve found on aerial plant organs that promotes gas exchange between the atmosphere and the plant body. Each stoma is formed by a strict cell lineage during the early stages of leaf development. Molecular genetics research using the model plant Arabidopsis has revealed the genes involved in stomatal differentiation. Cysteine-rich secretory peptides of the EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) family play crucial roles as extracellular signaling factors. Stomatal development is orchestrated by the positive factor STOMAGEN/EPFL9 and the negative factors EPF1, EPF2, and CHALLAH/EPFL6 in combination with multiple receptors. EPF1 and EPF2 are produced in the stomatal lineage cells of the epidermis, whereas STOMAGEN and CHALLAH are derived from the inner tissues. These findings highlight the complex cell-to-cell and intertissue communications that regulate stomatal development. To optimize gas exchange, particularly the balance between the uptake of carbon dioxide (CO(2)) and loss of water, plants control stomatal activity in response to environmental conditions. The CO(2) level and light intensity influence stomatal density. Plants sense environmental cues in mature leaves and adjust the stomatal density of newly forming leaves, indicating the involvement of long-distance systemic signaling. This review summarizes recent research progress in the peptide signaling of stomatal development and discusses the evolutionary model of the signaling machinery.

A prospective randomized controlled trial to determine if cryotherapy can reduce the pain of patients with minor form of recurrent aphthous stomatitis.

PubMed

Arikan, Osman Kursat; Birol, Ahu; Tuncez, Fatma; Erkek, Emel; Koc, Can

2006-01-01

Tissue cooling has long been used in the management of both acute and chronic pain. To determine whether the application of cryotherapy can reduce the pain of patients with minor form of recurrent aphthous stomatitis. Twenty adult patients who had 2 discrete aphthous stomatitides in the labial mucosa at the same time were included in this prospective, randomized, and placebo-controlled study. One of the 2 aphthous stomatitides was treated with cryotherapy, the other serving as a control. The pain of aphthous stomatitis was scored by the patient on a 6-point scale (from 0 to 5). The size of the aphthous stomatitis was also measured. At any interval, no statistical difference was found between the cryotherapy-treated aphthous stomatitis and the control in the change in the value of pain severity, nor was any statistical difference found in the change in the size of the aphthous stomatitis. However, a trend toward less pain in the aphthous stomatitis receiving cryotherapy was noted. These results suggest that application of cryotherapy on minor form of recurrent oral aphthous stomatitis has no beneficial analgesic effect compared to placebo.

Oral Paracetamol for Patent Ductus Arteriosus Rescue Closure.

PubMed

Pharande, Pramod; Watson, Hadley; Tan, Kenneth; Sehgal, Arvind

2018-01-01

The objective of this study was to ascertain the efficacy of oral paracetamol in closing a symptomatic patent ductus arteriosus (PDA) when used as 'rescue' option. After obtaining ethics approval, a retrospective appraisal of the data from April 2014 to July 2015 was performed. Infants who were administered oral paracetamol either after unsuccessful therapy with ibuprofen or where it was considered contraindicated were included. A previously published echocardiographic scoring schema to stratify for ductal disease severity was used. Using univariate analysis, characteristics of infants with successful closure were compared with partial (a priori reduction in composite score by ≥ 50% of pretreatment) or no closure. Twenty infants with gestation age and birthweight of 25.7 ± 1.5 weeks and 724.1 ± 143 g, respectively, were studied. Complete closure was noted in 10 (50%) infants with additional four infants showing a significant reduction in haemodynamic shunting. Gestational age at birth and at therapy, chronological age at therapy, birthweight and total fluid intake were comparable between the two groups. The pre-therapy composite score had a significant association with successful closure (the higher the echocardiographic score, the lesser the closure). Concomitant furosemide therapy and late-onset sepsis had a high likelihood ratio of unsuccessful closure (11.01 [2-tailed, p = 0.005] and 5.3 [2-tailed, p = 0.07]), respectively. Oral paracetamol may be a possible therapeutic option in premature infants where therapy with first-line agents is unsuccessful or contraindicated. Concomitant sepsis and furosemide administration may affect successful therapy.

Reduced plant water status under sub-ambient pCO2 limits plant productivity in the wild progenitors of C3 and C4 cereals

PubMed Central

Cunniff, Jennifer; Charles, Michael; Jones, Glynis; Osborne, Colin P.

2016-01-01

Background and Aims The reduction of plant productivity by low atmospheric CO2 partial pressure (pCO2) during the last glacial period is proposed as a limiting factor for the establishment of agriculture. Supporting this hypothesis, previous work has shown that glacial pCO2 limits biomass in the wild progenitors of C3 and C4 founder crops, in part due to the direct effects of glacial pCO2 on photosynthesis. Here, we investigate the indirect role of pCO2 mediated via water status, hypothesizing that faster soil water depletion at glacial (18 Pa) compared to post-glacial (27 Pa) pCO2, due to greater stomatal conductance, feeds back to limit photosynthesis during drying cycles. Methods We grew four wild progenitors of C3 and C4 crops at glacial and post-glacial pCO2 and investigated physiological changes in gas exchange, canopy transpiration, soil water content and water potential between regular watering events. Growth parameters including leaf area were measured. Key Results Initial transpiration rates were higher at glacial pCO2 due to greater stomatal conductance. However, stomatal conductance declined more rapidly over the soil drying cycle in glacial pCO2 and was associated with decreased intercellular pCO2 and lower photosynthesis. Soil water content was similar between pCO2 levels as larger leaf areas at post-glacial pCO2 offset the slower depletion of water. Instead the feedback could be linked to reduced plant water status. Particularly in the C4 plants, soil–leaf water potential gradients were greater at 18 Pa compared with 27 Pa pCO2, suggesting an increased ratio of leaf evaporative demand to supply. Conclusions Reduced plant water status appeared to cause a negative feedback on stomatal aperture in plants at glacial pCO2, thereby reducing photosynthesis. The effects were stronger in C4 species, providing a mechanism for reduced biomass at 18 Pa. These results have added significance when set against the drier climate of the glacial period. PMID:27578764

Congenital portosystemic shunts: diagnosis and treatment.

PubMed

Franchi-Abella, Stéphanie; Gonzales, Emmanuel; Ackermann, Oanez; Branchereau, Sophie; Pariente, Danièle; Guérin, Florent

2018-05-05

Congenital portosystemic shunts (CPSS) are rare vascular malformations that create an abnormal connection between portal and systemic veins resulting in complete or partial diversion of the portal flow away from the liver to the systemic venous system. Different anatomic types exist and several classifications have been proposed. They can be associated with other malformations especially cardiac and heterotaxia. The main complications include hepatic encephalopathy, liver tumors, portopulmonary hypertension, and pulmonary arteriovenous shunts. Diagnosis relies on imaging, and prenatal diagnosis is possible. Spontaneous closure of the CPSS is possible in some anatomic forms during the first year of life. When the CPSS remains patent, radiologic or surgical closure of the CPSS may prevent, resolve, or stabilize complications. Interventional radiology plays a key role for both the preoperative evaluation with occlusion test to assess the exact anatomy and to measure portal pressure after occlusion of the CPSS. Endovascular closure is the first option for treatment when possible.

A new stomatal paradigm for earth system models? (Invited)

NASA Astrophysics Data System (ADS)

Bonan, G. B.; Williams, M. D.; Fisher, R. A.; Oleson, K. W.; Lombardozzi, D.

2013-12-01

The land component of climate, and now earth system, models has simulated stomatal conductance since the introduction in the mid-1980s of the so-called second generation models that explicitly represented plant canopies. These second generation models used the Jarvis-style stomatal conductance model, which empirically relates stomatal conductance to photosynthetically active radiation, temperature, vapor pressure deficit, CO2 concentration, and other factors. Subsequent models of stomatal conductance were developed from a more mechanistic understanding of stomatal physiology, particularly that stomata are regulated so as to maximize net CO2 assimilation (An) and minimize water loss during transpiration (E). This concept is embodied in the Ball-Berry stomatal conductance model, which relates stomatal conductance (gs) to net assimilation (An), scaled by the ratio of leaf surface relative humidity to leaf surface CO2 concentration, or the Leuning variant which replaces relative humidity with a vapor pressure deficit term. This coupled gs-An model has been widely used in climate and earth system models since the mid-1990s. An alternative approach models stomatal conductance by directly optimizing water use efficiency, defined as the ratio An/gs or An/E. Conceptual developments over the past several years have shown that the Ball-Berry style model can be derived from optimization theory. However, an explicit optimization model has not been tested in an earth system model. We compare the Ball-Berry model with an explicit optimization model, both implemented in a new plant canopy parameterization developed for the Community Land Model, the land component of the Community Earth System Model. The optimization model is from the Soil-Plant-Atmosphere (SPA) model, which integrates plant and soil hydraulics, carbon assimilation, and gas diffusion. The canopy parameterization is multi-layer and resolves profiles of radiation, temperature, vapor pressure, leaf water stress, stomatal conductance, and photosynthetic capacity within the canopy. Stomatal conductance for each layer is calculated so as to maximize carbon gain, within the limitations of plant water storage and soil-to-canopy water transport. An iterative procedure determines for every model timestep the maximum stomatal conductance for a canopy layer and the associated assimilation rate. We compare the Ball-Berry stomatal model and the SPA stomatal model within the multi-layer canopy parameterization. We use eddy covariance flux tower data for six sites (three deciduous broadleaf forest and three evergreen needleleaf forest) spanning a total of 51 site-years. The multi-layer canopy has improved simulation of gross primary production (GPP), evapotranspiration, and sensible heat flux compared with the most recent version of the Community Land Model (CLM4.5). The Ball-Berry and SPA stomatal models have prominent differences in simulated fluxes and compared with observations. This is most evident during drought.

40 CFR 264.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2014 CFR

2014-07-01

... equipment, structures and soils. 264.114 Section 264.114 Protection of Environment ENVIRONMENTAL PROTECTION... of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soils must be properly disposed of or decontaminated unless otherwise specified in...

40 CFR 264.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2012 CFR

2012-07-01

... equipment, structures and soils. 264.114 Section 264.114 Protection of Environment ENVIRONMENTAL PROTECTION... of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soils must be properly disposed of or decontaminated unless otherwise specified in...

40 CFR 264.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2011 CFR

2011-07-01

... equipment, structures and soils. 264.114 Section 264.114 Protection of Environment ENVIRONMENTAL PROTECTION... of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soils must be properly disposed of or decontaminated unless otherwise specified in...

40 CFR 264.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2010 CFR

2010-07-01

... equipment, structures and soils. 264.114 Section 264.114 Protection of Environment ENVIRONMENTAL PROTECTION... of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soils must be properly disposed of or decontaminated unless otherwise specified in...

40 CFR 264.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2013 CFR

2013-07-01

... equipment, structures and soils. 264.114 Section 264.114 Protection of Environment ENVIRONMENTAL PROTECTION... of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soils must be properly disposed of or decontaminated unless otherwise specified in...

Modified Eversion Carotid Endarterectomy: A 14-Year Experience in a Tertiary Teaching University Hospital in Brazil (South America).

PubMed

Menezes, Fábio Hüsemann; Pagliuso, Natália Ponzio; Molinari, Giovani José Dal Poggetto

2018-03-01

Carotid endarterectomy is one of the most performed vascular procedures. Since the first reports in the late 1950s, the conventional open and the eversion techniques are the popularized ones. A short extraction or partial eversion technique has been previously described and recently has been subjected to case series reports. The aim of the study was to present the experience of a teaching hospital with modified or partial eversion endarterectomy compared with the experience with conventional open procedure performed exclusively by training vascular surgeons. A retrospective review of a consecutive series of cases from January 2002 to June 2016 was performed. There were 355 operations. The mean age was 70 years (range, 41-90), 72.39% were males, and 53.5% were symptomatic. There were 7.3% of contralateral occlusions and 12.1% of contralateral stenosis greater than 70%. General anesthesia was employed in 56% of cases and regional blockage in the remaining cases. A selective shunt was used in 10 patients among those operated with regional blockage (6.9%; 3.1% of the total group of patients) and 1 patient (0.5%) operated with general anesthesia. There were 73 open procedures with primary closure, 23 patch closures, and 259 partial eversion procedures. The mean operation time for the primary closure, patch closure, and eversion techniques were 129.9 min (range, 75-220), 137.5 min (range, 120-160), and 109.7 min (range, 45-230), respectively, with a significant difference (P < 0.0001, Kruskal-Wallis test). The mean clamping time for the same techniques was 23.5 min (range, 13-50), 42 min (range, 20-60), and 17.1 min (range, 9-41), respectively, with a significant difference (P < 0.0001, Kruskal-Wallis test). There were 2.25% of transient ischemic events, 2.54% of cerebrovascular accidents, 1.97% of death, and a combined death/cerebrovascular accidents rate of 3.94%, with no statistical difference between the surgical techniques. The incidence of neck hematoma was 5.63% and that of cranial nerve injury was 2.54%. There were 3.66% of patients submitted to late reoperation for restenosis. When results were analyzed according to the academic period of the last year of training, there was no difference regarding time and complications. Modified or partial eversion endarterectomy seems to be safely performed and applicable for the teaching of new vascular surgeons. Copyright © 2018 Elsevier Inc. All rights reserved.

Carbon partitioning patterns of mycorrhizal versus non-mycorrhizal plants: real-time dynamic measurements using 11 CO2.

PubMed

Wang, G M; Coleman, D C; Freckman, D W; Dyer, M I; McNAUGHTON, S J; Agra, M A; Goeschl, J D

1989-08-01

Gas exchange and carbon allocation patterns were studied in two populations of Panicum coloratum, an Africa C-4 grass. The plants were grown in split-root pots, containing partially sterilized soil, with one side either inoculated (I) or not inoculated (NI) with a vesicular arbuscular (VA) mycorrhizal Fungus, Gigaspora margarita. Net carbon exchange rates (CER) and stomatal conductances were measured with conventional gas exchange apparatus, and carbon assimilation, translocation, and allocation were measured using photosynthetically-fixed 11 CO 2 . Mycorrhizal infection on one half of the split-root system caused a 20%, increase in CER. The effect on CER was less in tillers on the opposite side of the plants from the infected half of the roots. The rate at which photosynthates were stored in the leaves was 45% higher. Sink activity (concentration of labelled photosynthates in stem phloem tissue) more than doubled in 1 versus NI plants. CER and stomatal conductances, along with most of the carbon allocation patterns, were nearly identical between the NI (control) high grazing and low grazing ecotypes. However, VA mycorrhizal fungi caused a greater storage of photosynthates in the low grazing ecotype.

Peri-exposure protection against Nipah virus disease using a single-dose recombinant vesicular stomatitis virus-based vaccine

PubMed Central

DeBuysscher, Blair L; Scott, Dana; Thomas, Tina; Feldmann, Heinz; Prescott, Joseph

2016-01-01

Nipah virus is a zoonotic paramyxovirus that causes severe disease in humans and animals. Due to almost yearly outbreaks in Bangladesh, and a large outbreak in Malaysia that lead to the shutdown of swine export, Nipah virus is both a threat to public health and the economy. Infection is associated with respiratory distress, encephalitis and human-to-human transmission, resulting in high case fatality rates during outbreaks. This study aims to address the amount of time needed until protection from a recombinant vesicular stomatitis virus-based vaccine candidate expressing the Nipah virus glycoprotein (G), which we have previously shown to protect hamsters and non-human primates when administered 28 days before challenge. We found that a single-dose vaccination, when administered 1 day before challenge, reduced viral load, limited pathology and fully protected hamsters from Nipah virus infection. The vaccine was even partially protective when administered at early time points following challenge with Nipah virus. These data indicate that a single administration of this vaccine to high-risk individuals, such as family members and health-care workers of infected patients, could be protective and useful for reducing human-to-human transmission and curbing an outbreak. PMID:28706736

Peri-exposure protection against Nipah virus disease using a single-dose recombinant vesicular stomatitis virus-based vaccine.

PubMed

DeBuysscher, Blair L; Scott, Dana; Thomas, Tina; Feldmann, Heinz; Prescott, Joseph

2016-01-01

Nipah virus is a zoonotic paramyxovirus that causes severe disease in humans and animals. Due to almost yearly outbreaks in Bangladesh, and a large outbreak in Malaysia that lead to the shutdown of swine export, Nipah virus is both a threat to public health and the economy. Infection is associated with respiratory distress, encephalitis and human-to-human transmission, resulting in high case fatality rates during outbreaks. This study aims to address the amount of time needed until protection from a recombinant vesicular stomatitis virus-based vaccine candidate expressing the Nipah virus glycoprotein (G), which we have previously shown to protect hamsters and non-human primates when administered 28 days before challenge. We found that a single-dose vaccination, when administered 1 day before challenge, reduced viral load, limited pathology and fully protected hamsters from Nipah virus infection. The vaccine was even partially protective when administered at early time points following challenge with Nipah virus. These data indicate that a single administration of this vaccine to high-risk individuals, such as family members and health-care workers of infected patients, could be protective and useful for reducing human-to-human transmission and curbing an outbreak.

Fracture mechanics analyses of partial crack closure in shell structures

NASA Astrophysics Data System (ADS)

Zhao, Jun

2007-12-01

This thesis presents the theoretical and finite element analyses of crack-face closure behavior in shells and its effect on the stress intensity factor under a bending load condition. Various shell geometries, such as spherical shell, cylindrical shell containing an axial crack, cylindrical shell containing a circumferential crack and shell with double curvatures, are all studied. In addition, the influence of material orthotropy on the crack closure effect in shells is also considered. The theoretical formulation is developed based on the shallow shell theory of Delale and Erdogan, incorporating the effect of crack-face closure at the compressive edges. The line-contact assumption, simulating the crack-face closure at the compressive edges, is employed so that the contact force at the closure edges is introduced, which can be translated to the mid-plane of the shell, accompanied by an additional distributed bending moment. The unknown contact force is computed by solving a mixed-boundary value problem iteratively, that is, along the crack length, either the normal displacement of the crack face at the compressive edges is equal to zero or the contact pressure is equal to zero. It is found that due to the curvature effects crack closure may not always occur on the entire length of the crack, depending on the direction of the bending load and the geometry of the shell. The crack-face closure influences significantly the magnitude of the stress intensity factors; it increases the membrane component but decreases the bending component. The maximum stress intensity factor is reduced by the crack-face closure. The significant influence of geometry and material orthotropy on rack closure behavior in shells is also predicted based on the analytical solutions. Three-dimensional FEA is performed to validate the theoretical solutions. It demonstrates that the crack face closure occurs actually over an area, not on a line, but the theoretical solutions of the stress intensity factor and the FEA solutions are in good agreement, because the contact area is very small compared with the shell thickness.

Carbonic anhydrases, EPF2 and a novel protease mediate CO2 control of stomatal development.

PubMed

Engineer, Cawas B; Ghassemian, Majid; Anderson, Jeffrey C; Peck, Scott C; Hu, Honghong; Schroeder, Julian I

2014-09-11

Environmental stimuli, including elevated carbon dioxide levels, regulate stomatal development; however, the key mechanisms mediating the perception and relay of the CO2 signal to the stomatal development machinery remain elusive. To adapt CO2 intake to water loss, plants regulate the development of stomatal gas exchange pores in the aerial epidermis. A diverse range of plant species show a decrease in stomatal density in response to the continuing rise in atmospheric CO2 (ref. 4). To date, one mutant that exhibits deregulation of this CO2-controlled stomatal development response, hic (which is defective in cell-wall wax biosynthesis, ref. 5), has been identified. Here we show that recently isolated Arabidopsis thaliana β-carbonic anhydrase double mutants (ca1 ca4) exhibit an inversion in their response to elevated CO2, showing increased stomatal development at elevated CO2 levels. We characterized the mechanisms mediating this response and identified an extracellular signalling pathway involved in the regulation of CO2-controlled stomatal development by carbonic anhydrases. RNA-seq analyses of transcripts show that the extracellular pro-peptide-encoding gene EPIDERMAL PATTERNING FACTOR 2 (EPF2), but not EPF1 (ref. 9), is induced in wild-type leaves but not in ca1 ca4 mutant leaves at elevated CO2 levels. Moreover, EPF2 is essential for CO2 control of stomatal development. Using cell-wall proteomic analyses and CO2-dependent transcriptomic analyses, we identified a novel CO2-induced extracellular protease, CRSP (CO2 RESPONSE SECRETED PROTEASE), as a mediator of CO2-controlled stomatal development. Our results identify mechanisms and genes that function in the repression of stomatal development in leaves during atmospheric CO2 elevation, including the carbonic-anhydrase-encoding genes CA1 and CA4 and the secreted protease CRSP, which cleaves the pro-peptide EPF2, in turn repressing stomatal development. Elucidation of these mechanisms advances the understanding of how plants perceive and relay the elevated CO2 signal and provides a framework to guide future research into how environmental challenges can modulate gas exchange in plants.

Carbonic anhydrases, EPF2 and a novel protease mediate CO2 control of stomatal development

PubMed Central

Engineer, Cawas B.; Ghassemian, Majid; Anderson, Jeffrey C.; Peck, Scott C.; Hu, Honghong; Schroeder, Julian I.

2014-01-01

Environmental stimuli, including elevated carbon dioxide levels, regulate stomatal development1–3; however, the key mechanisms mediating the perception and relay of the CO2 signal to the stomatal development machinery remain elusive. To adapt CO2 intake to water loss, plants regulate the development of stomatal gas exchange pores in the aerial epidermis. A diverse range of plant species show a decrease in stomatal density in response to the continuing rise in atmospheric CO2 (ref. 4). To date, one mutant that exhibits deregulation of this CO2-controlled stomatal development response, hic (which is defective in cell-wall wax biosynthesis, ref. 5), has been identified. Here we show that recently isolated Arabidopsis thaliana β-carbonic anhydrase double mutants (ca1 ca4)6 exhibit aninversion in their response to elevated CO2, showing increased stomatal development at elevated CO2 levels. We characterized the mechanisms mediating this response and identified an extracellular signalling pathway involved in the regulation of CO2-controlled stomatal development by carbonic anhydrases. RNA-seq analyses of transcripts show that the extracellular pro-peptide-encoding gene EPIDERMAL PATTERNING FACTOR 2 (EPF2)7,8, but not EPF1 (ref. 9), is induced in wild-type leaves but not inca1 ca4 mutant leaves at elevated CO2 levels. Moreover, EPF2 is essential for CO2 control of stomatal development. Using cell-wall proteomic analyses and CO2-dependent transcriptomic analyses, we identified a novel CO2-induced extracellular protease, CRSP (CO2 RESPONSE SECRETED PROTEASE), as a mediator of CO2-controlled stomatal development. Our results identify mechanisms and genes that function in the repression of stomatal development in leaves during atmospheric CO2 elevation, including the carbonic-anhydrase-encoding genes CA1 and CA4 and the secreted protease CRSP, which cleaves the pro-peptide EPF2, in turn repressing stomatal development. Elucidation of these mechanisms advances the understanding of how plants perceive and relay the elevated CO2 signal and provides a framework to guide future research into how environmental challenges can modulate gas exchange in plants. PMID:25043023

Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2 - and ABA-induced stomatal closing.

PubMed

Azoulay-Shemer, Tamar; Palomares, Axxell; Bagheri, Andisheh; Israelsson-Nordstrom, Maria; Engineer, Cawas B; Bargmann, Bastiaan O R; Stephan, Aaron B; Schroeder, Julian I

2015-08-01

Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2 ]. [CO2 ] in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll-deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard cell specific enhancer trap line. Our data show that more than 90% of guard cells were chlorophyll-deficient. Interestingly, approximately 45% of stomata had an unusual, previously not-described, morphology of thin-shaped chlorophyll-less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole-leaf photosynthetic parameters (PSII, qP, qN, FV '/FM' ) were comparable with wild-type plants. Time-resolved intact leaf gas-exchange analyses showed a reduction in stomatal conductance and CO2 -assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to [CO2 ] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO2 ] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO2 ] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO2 and ABA signal transduction are not directly modulated by guard cell photosynthesis/electron transport. Moreover, the finding that chlorophyll-less stomata cause a 'deflated' thin-shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard cell turgor production. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Vapor Pressure Deficit and Sap Velocity Dynamic Coupling in Canopy Dominant Trees in the Amazon basin

NASA Astrophysics Data System (ADS)

Chambers, J. Q.; Gimenez, B.; Jardine, K.; Negron Juarez, R. I.; Cobello, L. O.; Fontes, C.; Dawson, T. E.; Higuchi, N.

2017-12-01

In order to improve our ability to predict terrestrial water fluxes, an understanding of the interactions between plant physiology and environmental conditions is necessary, especially in tropical forests which recycle large fluxes of water to the atmosphere. This need has become more relevant due to observed records in global temperature. In this study we show a strong temporal correlation between sap velocity and leaf-to-air vapor pressure deficit (VPD) in canopy dominant trees in two primary rainforest sites in the Amazon basin (Santarém and Manaus, Brazil). As VPDs in the upper canopy (20-30 m) varied throughout the day and night, basal sap velocity (1.5 m) responded rapidly without an observable delay (< 15 min). Sap velocity showed a sigmoidal dependence on VPDs including an exponential increase, an inflection point, and a plateau, in all observed trees. Moreover, a clear diurnal hysteresis in sap velocity, stomatal conductance, and leaf water potential was evident with morning periods showing higher sensitivities to VPD than afternoon and night periods. Diurnal leaf gas exchange observations revealed a morning to midday peak in stomatal conductance, but midday to afternoon peak in transpiration and VPD. Thus, our study confirms that the temporal lag between the Gs peak and VPD peak are the major regulators of the hysteresis phenomenon as previously described by other studies. Moreover, out study provide direct evidence for the role of decreased stomatal conductance in the warm afternoon periods to reduce transpiration and allow for the partial recovery of leaf water potential to less negative values. Our results suggests the possibility of predicting evapotranspiration fluxes from ecosystem to regional scales using remote sensing of vegetation temperature from, for example, thermal images of satellites and drones.

Threshold response of mesophyll CO2 conductance to leaf hydraulics in highly transpiring hybrid poplar clones exposed to soil drying.

PubMed

Théroux-Rancourt, Guillaume; Éthier, Gilbert; Pepin, Steeve

2014-02-01

Mesophyll conductance (gm) has been shown to impose significant limitations to net CO2 assimilation (A) in various species during water stress. Net CO2 assimilation is also limited by stomatal conductance to water (gsw), both having been shown to co-vary with leaf hydraulic conductance (Kleaf). Lately, several studies have suggested a close functional link between Kleaf, gsw, and gm. However, such relationships could only be circumstantial since a recent study has shown that the response of gm to drought could merely be an artefactual consequence of a reduced intercellular CO2 mole fraction (Ci). Experiments were conducted on 8-week-old hybrid poplar cuttings to determine the relationship between Kleaf, gsw, and g m in clones of contrasting drought tolerance. It was hypothesized that changes in gsw and Kleaf in response to drought would not impact on gm over most of its range. The results show that Kleaf decreased in concert with g sw as drought proceeded, whereas gm measured at a normalized Ci remained relatively constant up to a g sw threshold of ~0.15 mol m(-2) s(-1). This delayed gm response prevented a substantial decline in A at the early stage of the drought, thereby enhancing water use efficiency. Reducing the stomatal limitation of droughted plants by diminishing the ambient CO2 concentration of the air did not modify gm or Kleaf. The relationship between gas exchange and leaf hydraulics was similar in both drought-tolerant and drought-sensitive clones despite their contrasting vulnerability to stem cavitation and stomatal response to soil drying. The results support the hypothesis of a partial hydraulic isolation of the mesophyll from the main transpiration pathway.

Transpiration efficiency over an annual cycle, leaf gas exchange and wood carbon isotope ratio of three tropical tree species.

PubMed

Cernusak, Lucas A; Winter, Klaus; Aranda, Jorge; Virgo, Aurelio; Garcia, Milton

2009-09-01

Variation in transpiration efficiency (TE) and its relationship with the stable carbon isotope ratio of wood was investigated in the saplings of three tropical tree species. Five individuals each of Platymiscium pinnatum (Jacq.) Dugand, Swietenia macrophylla King and Tectona grandis Linn. f. were grown individually in large (760 l) pots over 16 months in the Republic of Panama. Cumulative transpiration was determined by repeatedly weighing the pots with a pallet truck scale. Dry matter production was determined by destructive harvest. The TE, expressed as experiment-long dry matter production divided by cumulative water use, averaged 4.1, 4.3 and 2.9 g dry matter kg(-1) water for P. pinnatum, S. macrophylla and T. grandis, respectively. The TE of T. grandis was significantly lower than that of the other two species. Instantaneous measurements of the ratio of intercellular to ambient CO(2) partial pressures (c(i)/c(a)), taken near the end of the experiment, explained 66% of variation in TE. Stomatal conductance was lower in S. macrophylla than in T. grandis, whereas P. pinnatum had similar stomatal conductance to T. grandis, but with a higher photosynthetic rate. Thus, c(i)/c(a) and TE appeared to vary in response to both stomatal conductance and photosynthetic capacity. Stem-wood delta(13)C varied over a relatively narrow range of just 2.2 per thousand, but still explained 28% of variation in TE. The results suggest that leaf-level processes largely determined variation among the three tropical tree species in whole-plant water-use efficiency integrated over a full annual cycle.

The mechanics of delamination in fiber-reinforced composite materials. I - Stress singularities and solution structure

NASA Technical Reports Server (NTRS)

Wang, S. S.; Choi, I.

1983-01-01

The fundamental mechanics of delamination in fiber composite laminates is studied. Mathematical formulation of the problem is based on laminate anisotropic elasticity theory and interlaminar fracture mechanics concepts. Stress singularities and complete solution structures associated with general composite delaminations are determined. For a fully open delamination with traction-free surfaces, oscillatory stress singularities always appear, leading to physically inadmissible field solutions. A refined model is introduced by considering a partially closed delamination with crack surfaces in finite-length contact. Stress singularities associated with a partially closed delamination having frictional crack-surface contact are determined, and are found to be different from the inverse square-root one of the frictionless-contact case. In the case of a delamination with very small area of crack closure, a simplified model having a square-root stress singularity is employed by taking the limit of the partially closed delamination. The possible presence of logarithmic-type stress singularity is examined; no logarithmic singularity of any kind is found in the composite delamination problem. Numerical examples of dominant stress singularities are shown for delaminations having crack-tip closure with different frictional coefficients between general (1) and (2) graphite-epoxy composites. Previously announced in STAR as N84-13221

Effects of a Rebamipide Mouthwash on Stomatitis Caused by Cancer Chemotherapy-Evaluation of the Efficacy by Patients Themselves.

PubMed

Ishii, Naoko; Kawano, Yayoi; Sakai, Hideki; Hayashi, Seitaku; Akizuki, Norikazu; Komoda, Masayo; Hanawa, Takehisa

2017-08-01

 Anticancer drug-induced stomatitis develops in 30% to 40% of cancer cases that undergo chemotherapy. However, medications for this condition are not commercially available in Japan. Upon obtaining approval of the ethics committee, a mouthwash containing rebamipide as the active ingredient (rebamipide mouthwash) was administered to one inpatient and four outpatients, who had developed stomatitis caused by cancer chemotherapy. Starting from 14 d after the administration of the rebamipide mouthwash, the patients scored a stomatitis survey on oral state, pain level, and diet and recorded the number of times they gargled, as well as any stomatitis observations, in a stomatitis diary. The total scores for the points for each of the three types of survey sections were classified into Grades 0 to 4 and evaluated as a stomatitis evaluation score (SES). The SES became "0" in three out of the five patients within 14 d of treatment. No change in SES was found in one patient. In the remaining patients, SES became "0" once but increased again later. Using image analysis software (ImageJ), the area at which the stomatitis was observed was measured. When comparing SES and change in the area in patients who agreed to participate, gradual reductions in the extent of stomatitis was observed even during the period when SES did not change. Having patients fill in an observation chart was effective for grasping changes in symptoms in outpatients.

The receptor tyrosine kinase Pvr promotes tissue closure by coordinating corpse removal and epidermal zippering

PubMed Central

Garlena, Rebecca A.; Lennox, Ashley L.; Baker, Lewis R.; Parsons, Trish E.; Weinberg, Seth M.; Stronach, Beth E.

2015-01-01

A leading cause of human birth defects is the incomplete fusion of tissues, often manifested in the palate, heart or neural tube. To investigate the molecular control of tissue fusion, embryonic dorsal closure and pupal thorax closure in Drosophila are useful experimental models. We find that Pvr mutants have defects in dorsal midline closure with incomplete amnioserosa internalization and epidermal zippering, as well as cardia bifida. These defects are relatively mild in comparison to those seen with other signaling mutants, such as in the JNK pathway, and we demonstrate that JNK signaling is not perturbed by altering Pvr receptor tyrosine kinase activity. Rather, modulation of Pvr levels in the ectoderm has an impact on PIP3 membrane accumulation, consistent with a link to PI3K signal transduction. Polarized PI3K activity influences protrusive activity from the epidermal leading edge and the protrusion area changes in accord with Pvr signaling intensity, providing a possible mechanism to explain Pvr mutant phenotypes. Tissue-specific rescue experiments indicate a partial requirement in epithelial tissue, but confirm the essential role of Pvr in hemocytes for embryonic survival. Taken together, we argue that inefficient removal of the internalizing amnioserosa tissue by mutant hemocytes coupled with impaired midline zippering of mutant epithelium creates a situation in some embryos whereby dorsal midline closure is incomplete. Based on these observations, we suggest that efferocytosis (corpse clearance) could contribute to proper tissue closure and thus might underlie some congenital birth defects. PMID:26293306

Origins and Evolution of Stomatal Development1[OPEN

PubMed Central

2017-01-01

The fossil record suggests stomata-like pores were present on the surfaces of land plants over 400 million years ago. Whether stomata arose once or whether they arose independently across newly evolving land plant lineages has long been a matter of debate. In Arabidopsis, a genetic toolbox has been identified that tightly controls stomatal development and patterning. This includes the basic helix-loop-helix (bHLH) transcription factors SPEECHLESS (SPCH), MUTE, FAMA, and ICE/SCREAMs (SCRMs), which promote stomatal formation. These factors are regulated via a signaling cascade, which includes mobile EPIDERMAL PATTERNING FACTOR (EPF) peptides to enforce stomatal spacing. Mosses and hornworts, the most ancient extant lineages to possess stomata, possess orthologs of these Arabidopsis (Arabidopsis thaliana) stomatal toolbox genes, and manipulation in the model bryophyte Physcomitrella patens has shown that the bHLH and EPF components are also required for moss stomatal development and patterning. This supports an ancient and tightly conserved genetic origin of stomata. Here, we review recent discoveries and, by interrogating newly available plant genomes, we advance the story of stomatal development and patterning across land plant evolution. Furthermore, we identify potential orthologs of the key toolbox genes in a hornwort, further supporting a single ancient genetic origin of stomata in the ancestor to all stomatous land plants. PMID:28356502

40 CFR 265.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2010 CFR

2010-07-01

... equipment, structures and soils. 265.114 Section 265.114 Protection of Environment ENVIRONMENTAL PROTECTION... decontamination of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soil must be properly disposed of, or decontaminated unless specified otherwise in...

40 CFR 267.116 - What must I do with contaminated equipment, structure, and soils?

Code of Federal Regulations, 2014 CFR

2014-07-01

... equipment, structure, and soils? 267.116 Section 267.116 Protection of Environment ENVIRONMENTAL PROTECTION..., structure, and soils? You must properly dispose of or decontaminate all contaminated equipment, structures, and soils during the partial and final closure periods. By removing any hazardous wastes or hazardous...

40 CFR 265.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2012 CFR

2012-07-01

... equipment, structures and soils. 265.114 Section 265.114 Protection of Environment ENVIRONMENTAL PROTECTION... decontamination of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soil must be properly disposed of, or decontaminated unless specified otherwise in...

40 CFR 267.116 - What must I do with contaminated equipment, structure, and soils?

Code of Federal Regulations, 2010 CFR

2010-07-01

... equipment, structure, and soils? 267.116 Section 267.116 Protection of Environment ENVIRONMENTAL PROTECTION..., structure, and soils? You must properly dispose of or decontaminate all contaminated equipment, structures, and soils during the partial and final closure periods. By removing any hazardous wastes or hazardous...

40 CFR 265.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2011 CFR

2011-07-01

... equipment, structures and soils. 265.114 Section 265.114 Protection of Environment ENVIRONMENTAL PROTECTION... decontamination of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soil must be properly disposed of, or decontaminated unless specified otherwise in...

40 CFR 265.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2013 CFR

2013-07-01

... equipment, structures and soils. 265.114 Section 265.114 Protection of Environment ENVIRONMENTAL PROTECTION... decontamination of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soil must be properly disposed of, or decontaminated unless specified otherwise in...

40 CFR 267.116 - What must I do with contaminated equipment, structure, and soils?

Code of Federal Regulations, 2012 CFR

2012-07-01

... equipment, structure, and soils? 267.116 Section 267.116 Protection of Environment ENVIRONMENTAL PROTECTION..., structure, and soils? You must properly dispose of or decontaminate all contaminated equipment, structures, and soils during the partial and final closure periods. By removing any hazardous wastes or hazardous...

40 CFR 267.116 - What must I do with contaminated equipment, structure, and soils?

Code of Federal Regulations, 2013 CFR

2013-07-01

... equipment, structure, and soils? 267.116 Section 267.116 Protection of Environment ENVIRONMENTAL PROTECTION..., structure, and soils? You must properly dispose of or decontaminate all contaminated equipment, structures, and soils during the partial and final closure periods. By removing any hazardous wastes or hazardous...

40 CFR 265.114 - Disposal or decontamination of equipment, structures and soils.

Code of Federal Regulations, 2014 CFR

2014-07-01

... equipment, structures and soils. 265.114 Section 265.114 Protection of Environment ENVIRONMENTAL PROTECTION... decontamination of equipment, structures and soils. During the partial and final closure periods, all contaminated equipment, structures and soil must be properly disposed of, or decontaminated unless specified otherwise in...

40 CFR 267.116 - What must I do with contaminated equipment, structure, and soils?

Code of Federal Regulations, 2011 CFR

2011-07-01

... equipment, structure, and soils? 267.116 Section 267.116 Protection of Environment ENVIRONMENTAL PROTECTION..., structure, and soils? You must properly dispose of or decontaminate all contaminated equipment, structures, and soils during the partial and final closure periods. By removing any hazardous wastes or hazardous...

Supraoptimal carbon dioxide effects on growth of soybean [Glycine max (L.) Merr.

NASA Technical Reports Server (NTRS)

Wheeler, R. M.; Mackowiak, C. L.; Siegriest, L. M.; Sager, J. C.; Knott, W. M. (Principal Investigator)

1993-01-01

In tightly closed environments used for human life support in space, carbon dioxide (CO2) partial pressures can reach 500 to 1000 Pa, which may be supraoptimal or toxic to plants used for life support. To study this, soybeans [Glycine max (L.) Merr. cvs. McCall and Pixie] were grown for 90 days at 50, 100, 200, and 500 Pa partial pressure CO2 (500, 1000, 2000, and 5000 ppm). Plants were grown using recirculating nutrient film technique with a 12-h photoperiod, a 26 degrees C/20 degrees C thermoperiod, and approximately 300 micromoles m-2 s-1 photosynthetic photon flux (PPF). Seed yield and total biomass were greatest at 100 Pa for cv. McCall, suggesting that higher CO2 levels were supraoptimal. Seed yield and total biomass for cv. Pixie showed little difference between CO2 treatments. Average stomatal conductance of upper canopy leaves at 50 Pa CO2 approximately 500 Pa > 200 Pa > 100 Pa. Total water use over 90 d for both cultivars (combined on one recirculating system) equalled 822 kg water for 100 Pa CO2, 845 kg for 50 Pa, 879 kg for 200 Pa, and 1194 kg for 500 Pa. Water use efficiences for both cultivars combined equalled 3.03 (g biomass kg-1 water) for 100 Pa CO2, 2.54 g kg-1 for 200 Pa, 2.42 g kg-1 for 50 Pa, and 1.91 g kg-1 for 500 Pa. The increased stomatal conductance and stand water use at the highest CO2 level (500 Pa) were unexpected and pose interesting considerations for managing plants in a tightly closed system where CO2 concentrations may reach high levels.

Reevaluation of the plant "gemstones": Calcium oxalate crystals sustain photosynthesis under drought conditions.

PubMed

Tooulakou, Georgia; Giannopoulos, Andreas; Nikolopoulos, Dimosthenis; Bresta, Panagiota; Dotsika, Elissavet; Orkoula, Malvina G; Kontoyannis, Christos G; Fasseas, Costas; Liakopoulos, Georgios; Klapa, Maria I; Karabourniotis, George

2016-09-01

Land plants face the perpetual dilemma of using atmospheric carbon dioxide for photosynthesis and losing water vapors, or saving water and reducing photosynthesis and thus growth. The reason behind this dilemma is that this simultaneous exchange of gases is accomplished through the same minute pores on leaf surfaces, called stomata. In a recent study we provided evidence that pigweed, an aggressive weed, attenuates this problem exploiting large crystals of calcium oxalate as dynamic carbon pools. This plant is able to photosynthesize even under drought conditions, when stomata are closed and water losses are limited, using carbon dioxide from crystal decomposition instead from the atmosphere. Abscisic acid, an alarm signal that causes stomatal closure seems to be implicated in this function and for this reason we named this path "alarm photosynthesis." The so-far "enigmatic," but highly conserved and widespread among plant species calcium oxalate crystals seem to play a crucial role in the survival of plants.

Reevaluation of the plant “gemstones”: Calcium oxalate crystals sustain photosynthesis under drought conditions

PubMed Central

Tooulakou, Georgia; Giannopoulos, Andreas; Nikolopoulos, Dimosthenis; Bresta, Panagiota; Dotsika, Elissavet; Orkoula, Malvina G.; Kontoyannis, Christos G.; Fasseas, Costas; Liakopoulos, Georgios; Klapa, Maria I.; Karabourniotis, George

2016-01-01

ABSTRACT Land plants face the perpetual dilemma of using atmospheric carbon dioxide for photosynthesis and losing water vapors, or saving water and reducing photosynthesis and thus growth. The reason behind this dilemma is that this simultaneous exchange of gases is accomplished through the same minute pores on leaf surfaces, called stomata. In a recent study we provided evidence that pigweed, an aggressive weed, attenuates this problem exploiting large crystals of calcium oxalate as dynamic carbon pools. This plant is able to photosynthesize even under drought conditions, when stomata are closed and water losses are limited, using carbon dioxide from crystal decomposition instead from the atmosphere. Abscisic acid, an alarm signal that causes stomatal closure seems to be implicated in this function and for this reason we named this path “alarm photosynthesis.” The so-far “enigmatic,” but highly conserved and widespread among plant species calcium oxalate crystals seem to play a crucial role in the survival of plants. PMID:27471886

The Arabidopsis transcription factor ABIG1 relays ABA signaled growth inhibition and drought induced senescence.

PubMed

Liu, Tie; Longhurst, Adam D; Talavera-Rauh, Franklin; Hokin, Samuel A; Barton, M Kathryn

2016-10-04

Drought inhibits plant growth and can also induce premature senescence. Here we identify a transcription factor, ABA INSENSITIVE GROWTH 1 (ABIG1) required for abscisic acid (ABA) mediated growth inhibition, but not for stomatal closure. ABIG1 mRNA levels are increased both in response to drought and in response to ABA treatment. When treated with ABA, abig1 mutants remain greener and produce more leaves than comparable wild-type plants. When challenged with drought, abig1 mutants have fewer yellow, senesced leaves than wild-type. Induction of ABIG1 transcription mimics ABA treatment and regulates a set of genes implicated in stress responses. We propose a model in which drought acts through ABA to increase ABIG1 transcription which in turn restricts new shoot growth and promotes leaf senescence. The results have implications for plant breeding: the existence of a mutant that is both ABA resistant and drought resistant points to new strategies for isolating drought resistant genetic varieties.

Regulation of water, salinity, and cold stress responses by salicylic acid

PubMed Central

Miura, Kenji; Tada, Yasuomi

2014-01-01

Salicylic acid (SA) is a naturally occurring phenolic compound. SA plays an important role in the regulation of plant growth, development, ripening, and defense responses. The role of SA in the plant–pathogen relationship has been extensively investigated. In addition to defense responses, SA plays an important role in the response to abiotic stresses, including drought, low temperature, and salinity stresses. It has been suggested that SA has great agronomic potential to improve the stress tolerance of agriculturally important crops. However, the utility of SA is dependent on the concentration of the applied SA, the mode of application, and the state of the plants (e.g., developmental stage and acclimation). Generally, low concentrations of applied SA alleviate the sensitivity to abiotic stresses, and high concentrations of applied induce high levels of oxidative stress, leading to a decreased tolerance to abiotic stresses. In this article, the effects of SA on the water stress responses and regulation of stomatal closure are reviewed. PMID:24478784

Investigation of the influence of liquid surface films on O3 and PAN deposition to plant leaves coated with organic/inorganic solution

NASA Astrophysics Data System (ADS)

Sun, Shang; Moravek, Alexander; Trebs, Ivonne; Kesselmeier, Jürgen; Sörgel, Matthias

2016-12-01

This study investigates the influence of leaf surface water films on the deposition of ozone (O3) and peroxyacetyl nitrate (PAN) under controlled laboratory conditions. A twin-cuvette system was used to simulate environmental variables. We observed a clear correlation between the O3 deposition on plants (Quercus ilex) and the relative humidity (RH) under both light and dark conditions. During the light period the observed increase of the O3 deposition was mainly attributed to the opening of leaf stomata, while during the absence of light the liquid surface films were the reason for O3 deposition. This finding was supported by experimentally induced stomatal closure by the infiltration of abscisic acid. In the case of PAN, no relationship with RH was found during the dark period, which indicates that the nonstomatal deposition of PAN is not affected by the liquid surface films. Consequently, the ratio of the O3 and PAN deposition velocities is not constant when relative humidity changes, which is in contrast to assumptions made in many models. The flux partitioning ratio between nonstomatal and stomatal depositions as well as between nonstomatal and total depositions was found to be Rnsto/sto = 0.21-0.40, Rnsto/tot = 0.18-0.30 for O3 and Rnsto/sto = 0.26-0.29, Rnsto/tot = 0.21-0.23 for PAN. Furthermore, we demonstrate that the formation of the liquid surface film on leaves and the nonstomatal O3 deposition are depending on the chemical composition of the particles deposited on the leaf cuticles as proposed previously.

Overexpression of AtEDT1/HDG11 in Chinese Kale (Brassica oleracea var. alboglabra) Enhances Drought and Osmotic Stress Tolerance

PubMed Central

Zhu, Zhangsheng; Sun, Binmei; Xu, Xiaoxia; Chen, Hao; Zou, Lifang; Chen, Guoju; Cao, Bihao; Chen, Changming; Lei, Jianjun

2016-01-01

Plants are constantly challenged by environmental stresses, including drought and high salinity. Improvement of drought and osmotic stress tolerance without yield decrease has been a great challenge in crop improvement. The Arabidopsis ENHANCED DROUGHT TOLERANCE1/HOMEODOMAIN GLABROUS11 (AtEDT1/HDG11), a protein of the class IV HD-Zip family, has been demonstrated to significantly improve drought tolerance in Arabidopsis, rice, and pepper. Here, we report that AtEDT1/HDG11 confers drought and osmotic stress tolerance in the Chinese kale. AtEDT1/HDG11-overexpression lines exhibit auxin-overproduction phenotypes, such as long hypocotyls, tall stems, more root hairs, and a larger root system architecture. Compared with the untransformed control, transgenic lines have significantly reduced stomatal density. In the leaves of transgenic Chinese kale plants, proline (Pro) content and reactive oxygen species-scavenging enzyme activity was significantly increased after drought and osmotic stress, particularly compared to wild kale. More importantly, AtEDT1/HDG11-overexpression leads to abscisic acid (ABA) hypersensitivity, resulting in ABA inhibitor germination and induced stomatal closure. Consistent with observed phenotypes, the expression levels of auxin, ABA, and stress-related genes were also altered under both normal and/or stress conditions. Further analysis showed that AtEDT1/HDG11, as a transcription factor, can target the auxin biosynthesis gene YUCC6 and ABA response genes ABI3 and ABI5. Collectively, our results provide a new insight into the role of AtEDT1/HDG11 in enhancing abiotic stress resistance through auxin- and ABA-mediated signaling response in Chinese kale. PMID:27625663

Overexpression of AtEDT1/HDG11 in Chinese Kale (Brassica oleracea var. alboglabra) Enhances Drought and Osmotic Stress Tolerance.

PubMed

Zhu, Zhangsheng; Sun, Binmei; Xu, Xiaoxia; Chen, Hao; Zou, Lifang; Chen, Guoju; Cao, Bihao; Chen, Changming; Lei, Jianjun

2016-01-01

Plants are constantly challenged by environmental stresses, including drought and high salinity. Improvement of drought and osmotic stress tolerance without yield decrease has been a great challenge in crop improvement. The Arabidopsis ENHANCED DROUGHT TOLERANCE1/HOMEODOMAIN GLABROUS11 (AtEDT1/HDG11), a protein of the class IV HD-Zip family, has been demonstrated to significantly improve drought tolerance in Arabidopsis, rice, and pepper. Here, we report that AtEDT1/HDG11 confers drought and osmotic stress tolerance in the Chinese kale. AtEDT1/HDG11-overexpression lines exhibit auxin-overproduction phenotypes, such as long hypocotyls, tall stems, more root hairs, and a larger root system architecture. Compared with the untransformed control, transgenic lines have significantly reduced stomatal density. In the leaves of transgenic Chinese kale plants, proline (Pro) content and reactive oxygen species-scavenging enzyme activity was significantly increased after drought and osmotic stress, particularly compared to wild kale. More importantly, AtEDT1/HDG11-overexpression leads to abscisic acid (ABA) hypersensitivity, resulting in ABA inhibitor germination and induced stomatal closure. Consistent with observed phenotypes, the expression levels of auxin, ABA, and stress-related genes were also altered under both normal and/or stress conditions. Further analysis showed that AtEDT1/HDG11, as a transcription factor, can target the auxin biosynthesis gene YUCC6 and ABA response genes ABI3 and ABI5. Collectively, our results provide a new insight into the role of AtEDT1/HDG11 in enhancing abiotic stress resistance through auxin- and ABA-mediated signaling response in Chinese kale.

The response of vegetation to rising CO2 concentrations plays an important role in future changes in the hydrological cycle

NASA Astrophysics Data System (ADS)

Hong, Tao; Dong, Wenjie; Ji, Dong; Dai, Tanlong; Yang, Shili; Wei, Ting

2018-04-01

The effects of increasing CO2 concentrations on plant and carbon cycle have been extensively investigated; however, the effects of changes in plants on the hydrological cycle are still not fully understood. Increases in CO2 modify the stomatal conductance and water use of plants, which may have a considerable effect on the hydrological cycle. Using the carbon-climate feedback experiments from CMIP5, we estimated the responses of plants and hydrological cycle to rising CO2 concentrations to double of pre-industrial levels without climate change forcing. The mode results show that rising CO2 concentrations had a significant influence on the hydrological cycle by changing the evaporation and transpiration of plants and soils. The increases in the area covered by plant leaves result in the increases in vegetation evaporation. Besides, the physiological effects of stomatal closure were stronger than the opposite effects of changes in plant structure caused by the increases in LAI (leaf area index), which results in the decrease of transpiration. These two processes lead to overall decreases in evaporation, and then contribute to increases in soil moisture and total runoff. In the dry areas, the stronger increase in LAI caused the stronger increases in vegetation evaporation and then lead to the overall decreases in P - E (precipitation minus evaporation) and soil moisture. However, the soil moisture in sub-arid and wet areas would increase, and this may lead to the soil moisture deficit worse in the future in the dry areas. This study highlights the need to consider the different responses of plants and the hydrological cycle to rising CO2 in dry and wet areas in future water resources management, especially in water-limited areas.

Effects of ozone-vegetation coupling on surface ozone air quality via biogeochemical and meteorological feedbacks

NASA Astrophysics Data System (ADS)

Sadiq, Mehliyar; Tai, Amos P. K.; Lombardozzi, Danica; Martin, Maria Val

2017-02-01

Tropospheric ozone is one of the most hazardous air pollutants as it harms both human health and plant productivity. Foliage uptake of ozone via dry deposition damages photosynthesis and causes stomatal closure. These foliage changes could lead to a cascade of biogeochemical and biogeophysical effects that not only modulate the carbon cycle, regional hydrometeorology and climate, but also cause feedbacks onto surface ozone concentration itself. In this study, we implement a semi-empirical parameterization of ozone damage on vegetation in the Community Earth System Model to enable online ozone-vegetation coupling, so that for the first time ecosystem structure and ozone concentration can coevolve in fully coupled land-atmosphere simulations. With ozone-vegetation coupling, present-day surface ozone is simulated to be higher by up to 4-6 ppbv over Europe, North America and China. Reduced dry deposition velocity following ozone damage contributes to ˜ 40-100 % of those increases, constituting a significant positive biogeochemical feedback on ozone air quality. Enhanced biogenic isoprene emission is found to contribute to most of the remaining increases, and is driven mainly by higher vegetation temperature that results from lower transpiration rate. This isoprene-driven pathway represents an indirect, positive meteorological feedback. The reduction in both dry deposition and transpiration is mostly associated with reduced stomatal conductance following ozone damage, whereas the modification of photosynthesis and further changes in ecosystem productivity are found to play a smaller role in contributing to the ozone-vegetation feedbacks. Our results highlight the need to consider two-way ozone-vegetation coupling in Earth system models to derive a more complete understanding and yield more reliable future predictions of ozone air quality.

Water stress mitigates the negative effects of ozone on photosynthesis and biomass in poplar plants.

PubMed

Gao, Feng; Catalayud, Vicent; Paoletti, Elena; Hoshika, Yasutomo; Feng, Zhaozhong

2017-11-01

Tropospheric ozone (O 3 ) pollution frequently overlaps with drought episodes but the combined effects are not yet understood. We investigated the physiological and biomass responses of an O 3 sensitive hybrid poplar clone ('546') under three O 3 levels (charcoal-filtered ambient air, non-filtered ambient air (NF), and NF plus 40 ppb) and two watering regimes (well-watered (WW) and reduced watering (RW), i.e. 40% irrigation) for one growing season. Water stress increased chlorophyll and carotenoid contents, protecting leaves from pigment degradation by O 3 . Impairment of photosynthesis by O 3 was also reduced by stomatal closure due to water stress, which preserved light-saturated CO 2 assimilation rate, and the maximum carboxylation efficiency. Water stress increased water use efficiency of the leaves while O 3 decreased it, showing significant interactions. Effects were more evident in older leaves than in younger leaves. Water stress reduced biomass production, but the negative effects of O 3 were less in RW than in WW for total biomass per plant. A stomatal O 3 flux-based dose-response relationship was parameterized considering water stress effects, which explained biomass losses much better than a concentration-based approach. The O 3 critical level of Phytotoxic Ozone Dose over a threshold of 7 nmol O 3 .m -2 .s -1 (POD 7 ) for a 4% biomass loss in this poplar clone under different water regimes was 4.1 mmol m -2 . Our results suggest that current O 3 levels in most parts of China threaten poplar growth and that interaction with water availability is a key factor for O 3 risk assessment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Estimating ecosystem iso/anisohydry using microwave satellite data and its applications in ecohydrology

NASA Astrophysics Data System (ADS)

Li, Y.; Guan, K.; Gentine, P.; Konings, A. G.; Bhattacharya, A.; Meinzer, F. C.; Kimball, J. S.; Xu, X.; Anderegg, W.; McDowell, N. G.; Martínez-Vilalta, J.; Long, D. G.; Good, S. P.

2017-12-01

The concept of iso/anisohydry describes the degree to which plants regulate their water status, operating from isohydric with strict stomatal closure to anisohydric with greater stomatal conductance under drying conditions. Though some species-level measures of iso/anisohydry exist at limited locations, ecosystem scale information is still largely unavailable. In this study, we use diurnal observations from active (Ku-Band backscatter from QuikSCAT) and passive (X-band Vegetation Optical Depth [VOD] from AMSR-E) microwave satellite data to estimate global ecosystem iso/anisohydry. The two independent estimates from radar backscatter and VOD show good agreement at low and mid-latitudes but diverge at high latitudes. Grasslands, croplands, wetlands, and open shrublands are more anisohydric, whereas evergreen broadleaf and deciduous broadleaf forests are more isohydric. The direct validation with upscaled in-situ species iso/anisohydry estimates indicates that the VOD estimates have much better agreement than the backscatter in terms of their iso/anisohydry metrics. The indirect validation suggests that both estimates are consistent with prior knowledge that vegetation water status of anisohydric ecosystems more closely tracks environmental fluctuations of water availability and demand than their isohydric counterparts. The ecosystem level iso/anisohydry can be applied to reveal new insights into spatio-temporal ecosystem response to droughts. We conducted a case study to demonstrate the potential application of iso/anisohydry. We find that during the 2011 drought in US, over the drought affected region in the southern US, isohydric ecosystems experienced larger decline in productivity (NDVI and GPP) than anisohydric ones. However, during the 2012 drought in central US, both isohydric and anisohydric ecosystems exhibited similar decline in productivity.

Quantitative limitations to photosynthesis in K deficient sunflower and their implications on water-use efficiency.

PubMed

Jákli, Bálint; Tavakol, Ershad; Tränkner, Merle; Senbayram, Mehmet; Dittert, Klaus

2017-02-01

Potassium (K) is crucial for crop growth and is strongly related to stress tolerance and water-use efficiency (WUE). A major physiological effect of K deficiency is the inhibition of net CO 2 assimilation (A N ) during photosynthesis. Whether this reduction originates from limitations either to photochemical energy conversion or biochemical CO 2 fixation or from a limitation to CO 2 diffusion through stomata and the leaf mesophyll is debated. In this study, limitations to photosynthetic carbon gain of sunflower (Helianthus annuus L.) under K deficiency and PEG- induced water deficit were quantified and their implications on plant- and leaf-scale WUE (WUE P , WUE L ) were evaluated. Results show that neither maximum quantum use efficiency (F v /F m ) nor in-vivo RubisCo activity were directly affected by K deficiency and that the observed impairment of A N was primarily due to decreased CO 2 mesophyll conductance (g m ). K deficiency additionally impaired leaf area development which, together with reduced A N , resulted in inhibition of plant growth and a reduction of WUE P . Contrastingly, WUE L was not affected by K supply which indicated no inhibition of stomatal control. PEG-stress further impeded A N by stomatal closure and resulted in enhanced WUE L and high oxidative stress. It can be concluded from this study that reduction of g m is a major response of leaves to K deficiency, possibly due to changes in leaf anatomy, which negatively affects A N and contributes to the typical symptoms like oxidative stress, growth inhibition and reduced WUE P . Copyright © 2016 Elsevier GmbH. All rights reserved.

Mix-and-match: ligand-receptor pairs in stomatal development and beyond.

PubMed

Torii, Keiko U

2012-12-01

Stomata are small valves on the plant epidermis balancing gas exchange and water loss. Stomata are formed according to positional cues. In Arabidopsis, two EPIDERMAL PATTERNING FACTOR (EPF) peptides, EPF1 and EPF2, are secreted from stomatal precursors enforcing proper stomatal patterning. Here, I review recent studies revealing the ligand-receptor pairs and revising the previously predicted relations between receptors specifying stomatal patterning: ERECTA-family and TOO MANY MOUTHS (TMM). Furthermore, EPF-LIKE9 (EPFL9/Stomagen) promotes stomatal differentiation from internal tissues. Two EPFL peptides specify inflorescence architecture, a process beyond stomatal development, as ligands for ERECTA. Thus, broadly expressed receptor kinases may regulate multiple developmental processes through perceiving different peptide ligands, each with a specialized expression pattern. TMM in the epidermis may fine-tune multiple EPF/EPFL signals to prevent signal interference. Copyright © 2012 Elsevier Ltd. All rights reserved.

Stomatal Complex Development and F-Actin Organization in Maize Leaf Epidermis Depend on Cellulose Synthesis.

PubMed

Panteris, Emmanuel; Achlati, Theonymphi; Daras, Gerasimos; Rigas, Stamatis

2018-06-06

Cellulose microfibrils reinforce the cell wall for morphogenesis in plants. Herein, we provide evidence on a series of defects regarding stomatal complex development and F-actin organization in Zea mays leaf epidermis, due to inhibition of cellulose synthesis. Formative cell divisions of stomatal complex ontogenesis were delayed or inhibited, resulting in lack of subsidiary cells and frequently in unicellular stomata, with an atypical stomatal pore. Guard cells failed to acquire a dumbbell shape, becoming rounded, while subsidiary cells, whenever present, exhibited aberrant morphogenesis. F-actin organization was also affected, since the stomatal complex-specific arrays were scarcely observed. At late developmental stages, the overall F-actin network was diminished in all epidermal cells, although thick actin bundles persisted. Taken together, stomatal complex development strongly depends on cell wall mechanical properties. Moreover, F-actin organization exhibits a tight relationship with the cell wall.

Testing Earth System Models with Earth System Data: using C isotopes in atmospheric CO2 to probe stomatal response to future climate change

NASA Astrophysics Data System (ADS)

Ballantyne, A. P.; Miller, J. B.; Bowling, D. R.; Tans, P. P.; Baker, I. T.

2013-12-01

The global cycles of water and carbon are inextricably linked through photosynthesis. This link is largely governed by stomatal conductance that regulates water loss to the atmosphere and carbon gain to the biosphere. Although extensive research has focused on the response of stomatal conductance to increased atmospheric CO2, much less research has focused on the response of stomatal conductance to concomitant climate change. Here we make use of intensive and extensive measurements of C isotopes in source CO2 to the atmosphere (del-bio) to make inferences about stomatal response to climatic factors at a single forest site and across a network of global observation sites. Based on intensive observations at the Niwot Ridge Ameriflux site we discover that del-bio is an excellent physical proxy of stomatal response during the growing season and this response is highly sensitive to atmospheric water vapor pressure deficit (VPD). We use these intensive single forest site observations to inform our analysis of the global observation network, focusing in on the growing season across an array of terrestrial sites. We find that stomatal response across most of these terrestrial sites is also highly sensitive to VPD. Lastly, we simulate the response of future climate change on stomatal response and discover that future increases in VPD may limit the biosphere's capacity to assimilate future CO2 emissions. These results have direct implications for the benchmarking of Earth System Models as stomatal conductance in many of these models does not vary as a function of VPD.

UV fluorescence excitation imaging of healing of wounds in skin: Evaluation of wound closure in organ culture model.

PubMed

Wang, Ying; Gutierrez-Herrera, Enoch; Ortega-Martinez, Antonio; Anderson, Richard Rox; Franco, Walfre

2016-09-01

Molecules native to tissue that fluoresce upon light excitation can serve as reporters of cellular activity and protein structure. In skin, the fluorescence ascribed to tryptophan is a marker of cellular proliferation, whereas the fluorescence ascribed to cross-links of collagen is a structural marker. In this work, we introduce and demonstrate a simple but robust optical method to image the functional process of epithelialization and the exposed dermal collagen in wound healing of human skin in an organ culture model. Non-closing non-grafted, partial closing non-grafted, and grafted wounds were created in ex vivo human skin and kept in culture. A wide-field UV fluorescence excitation imaging system was used to visualize epithelialization of the exposed dermis and quantitate wound area, closure, and gap. Histology (H&E staining) was also used to evaluate epithelialization. The endogenous fluorescence excitation of cross-links of collagen at 335 nm clearly shows the dermis missing epithelium, while the endogenous fluorescence excitation of tryptophan at 295 nm shows keratinocytes in higher proliferating state. The size of the non-closing wound was 11.4 ± 1.8 mm and remained constant during the observation period, while the partial-close wound reached 65.5 ± 4.9% closure by day 16. Evaluations of wound gaps using fluorescence excitation images and histology images are in agreement. We have established a fluorescence imaging method for studying epithelialization processes, evaluating keratinocyte proliferation, and quantitating closure during wound healing of skin in an organ culture model: the dermal fluorescence of pepsin-digestible collagen cross-links can be used to quantitate wound size, closure extents, and gaps; and, the epidermal fluorescence ascribed to tryptophan can be used to monitor and quantitate functional states of epithelialization. UV fluorescence excitation imaging has the potential to become a valuable tool for research, diagnostic and educational purposes on evaluating the healing of wounds. Lasers Surg. Med. 48:678-685, 2016. © 2016 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc. © 2016 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Generalized hydromechanical model for stomatal responses to hydraulic perturbations.

PubMed

Kwon, H W; Choi, M Y

2014-01-07

Stomata respond in a common pattern to various hydraulic perturbations on any part of the 'soil-plant-air' system: initial transient 'wrong-way' responses and final stationary 'right-way' responses. In order to describe this pattern on the basis of statistical physics, we propose a simple model where turgor pressure of a cell is taken to be a power function of its volume, and obtain results in qualitative agreement with experimental data for responses to a variety of hydraulic perturbations: Firstly, stationary stomatal conductance as a function of the vapor pressure deficit divides into three regimes characterized by sensitivities of the stomatal conductance and the transpiration rate with respect to vapor pressure deficit; secondly, for every hydraulic perturbation, the initial transient 'wrong-way' responses always appear; thirdly, on condition that water is supplied insufficiently, stomatal oscillations are often observed; finally, stomatal responses following leaf excision exhibit, after the initial transient wrong-way responses, slow relaxation to stomatal closing. In particular, comparison of areoles having different numbers of stomata demonstrates that areoles with small numbers of stomata tend to provoke lack of water in the soil as well as in the plant. In addition, our model also describes well dependence of the stomatal conductance on temperature. It may be extended further to describe stomatal responses to other environmental factors such as carbon dioxide, light, and temperature. © 2013 Elsevier Ltd. All rights reserved.

Arabidopsis ANGUSTIFOLIA3 (AN3) is associated with the promoter of CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) to regulate light-mediated stomatal development.

PubMed

Meng, Lai-Sheng; Li, Cong; Xu, Meng-Ke; Sun, Xu-Dong; Wan, Wen; Cao, Xiao-Ying; Zhang, Jin-Lin; Chen, Kun-Ming

2018-04-12

Light signals are perceived by multiple photoreceptors that converge to suppress the RING E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) for the regulation of stomatal development. Thus, COP1 is a point of integration between light signaling and stomatal patterning. However, how light signaling is collected into COP1 for the production and spacing of stomata is still unknown. Here, we report that the loss-of-function mutant of ANGUSTIFOLIA3 (AN3) delays asymmetric cell division, which leads to decreased stomatal index. Furthermore, overexpression of AN3 accelerates asymmetric cell division, which results in clusters of stomata. In addition, the stomatal development through AN3 regulation is mediated by light signaling. Finally, we find that an3 is a light-signaling mutant, and that AN3 protein is light regulated. Self-activation by AN3 contributes to the control of AN3 expression. Thus, AN3 is a point of collection between light signaling and stomatal patterning. Target-gene analysis indicates that AN3 is associated with COP1 promoter for the regulation of light-controlling stomatal development. Together, these components for regulating stomatal development form an AN3-COP1-E3 ubiquitin ligase complex, allowing the integration of light signaling into the production and spacing of stomata. © 2018 John Wiley & Sons Ltd.

[Suitability of four stomatal conductance models in agro-pastoral ecotone in North China: A case study for potato and oil sunflower.

PubMed

Huang, Ming Xia; Wang, Jing; Tang, Jian Zhao; Yu, Qiang; Zhang, Jun; Xue, Qing Yu; Chang, Qing; Tan, Mei Xiu

2016-11-18

The suitability of four popular empirical and semi-empirical stomatal conductance models (Jarvis model, Ball-Berry model, Leuning model and Medlyn model) was evaluated based on para-llel observation data of leaf stomatal conductance, leaf net photosynthetic rate and meteorological factors during the vigorous growing period of potato and oil sunflower at Wuchuan experimental station in agro-pastoral ecotone in North China. It was found that there was a significant linear relationship between leaf stomatal conductance and leaf net photosynthetic rate for potato, whereas the linear relationship appeared weaker for oil sunflower. The results of model evaluation showed that Ball-Berry model performed best in simulating leaf stomatal conductance of potato, followed by Leuning model and Medlyn model, while Jarvis model was the last in the performance rating. The root-mean-square error (RMSE) was 0.0331, 0.0371, 0.0456 and 0.0794 mol·m -2 ·s -1 , the normalized root-mean-square error (NRMSE) was 26.8%, 30.0%, 36.9% and 64.3%, and R-squared (R 2 ) was 0.96, 0.61, 0.91 and 0.88 between simulated and observed leaf stomatal conductance of potato for Ball-Berry model, Leuning model, Medlyn model and Jarvis model, respectively. For leaf stomatal conductance of oil sunflower, Jarvis model performed slightly better than Leuning model, Ball-Berry model and Medlyn model. RMSE was 0.2221, 0.2534, 0.2547 and 0.2758 mol·m -2 ·s -1 , NRMSE was 40.3%, 46.0%, 46.2% and 50.1%, and R 2 was 0.38, 0.22, 0.23 and 0.20 between simulated and observed leaf stomatal conductance of oil sunflower for Jarvis model, Leuning model, Ball-Berry model and Medlyn model, respectively. The path analysis was conducted to identify effects of specific meteorological factors on leaf stomatal conductance. The diurnal variation of leaf stomatal conductance was principally affected by vapour pressure saturation deficit for both potato and oil sunflower. The model evaluation suggested that the stomatal conductance models for oil sunflower are to be improved in further research.

Spatial Distribution of Photosynthesis during Drought in Field-Grown and Acclimated and Nonacclimated Growth Chamber-Grown Cotton 1

PubMed Central

Wise, Robert R.; Ortiz-Lopez, Adriana; Ort, Donald R.

1992-01-01

Inhomogeneous photosynthetic activity has been reported to occur in drought-stressed leaves. In addition, it has been suggested that these water stress-induced nonuniformities in photosynthesis are caused by “patchy” stomatal closure and that the phenomenon may have created the illusion of a nonstomatal component to the inhibition of photosynthesis. Because these earlier studies were performed with nonacclimated growth chamber-grown plants, we sought to determine whether such “patches” existed in drought-treated, field-grown plants or in chamber-grown plants that had been acclimated to low leaf water potentials (ψleaf). Cotton (Gossypium hirsutum L.) was grown in the field and subjected to drought by withholding irrigation and rain from 24 d after planting. The distribution of photosynthesis, which may reflect the stomatal aperture distribution in a heterobaric species such as cotton, was assayed by autoradiography after briefly exposing attached leaves of field-grown plants to 14CO2. A homogeneous distribution of radioactive photosynthate was evident even at the lowest ψleaf of −1.34 MPa. “Patchiness” could, however, be induced by uprooting the plant and allowing the shoot to air dry for 6 to 8 min. In parallel studies, growth chamber-grown plants were acclimated to drought by withholding irrigation for three 5-d drought cycles interspersed with irrigation. This drought acclimation lowered the ψleaf value at which control rates of photosynthesis could be sustained by approximately 0.7 MPa and was accompanied by a similar decline in the ψleaf at which patchiness first appeared. Photosynthetic inhomogeneities in chamber-grown plants that were visible during moderate water stress and ambient levels of CO2 could be largely removed with elevated CO2 levels (3000 μL L−1), suggesting that they were stomatal in nature. However, advanced dehydration (less than approximately 2.0 MPa) resulted in “patches” that could not be so removed and were probably caused by nonstomatal factors. The demonstration that patches do not exist in drought-treated, field-grown cotton and that the presence of patches in chamber-grown plants can be altered by treatments that cause an acclimation of photosynthesis leads us to conclude that spatial heterogeneities in photosynthesis probably do not occur frequently under natural drought conditions. Images Figure 1 Figure 3 Figure 4 PMID:16652956

Interactive Effects of CO2 Concentration and Water Regime on Stable Isotope Signatures, Nitrogen Assimilation and Growth in Sweet Pepper.

PubMed

Serret, María D; Yousfi, Salima; Vicente, Rubén; Piñero, María C; Otálora-Alcón, Ginés; Del Amor, Francisco M; Araus, José L

2017-01-01

Sweet pepper is among the most widely cultivated horticultural crops in the Mediterranean basin, being frequently grown hydroponically under cover in combination with CO 2 fertilization and water conditions ranging from optimal to suboptimal. The aim of this study is to develop a simple model, based on the analysis of plant stable isotopes in their natural abundance, gas exchange traits and N concentration, to assess sweet pepper growth. Plants were grown in a growth chamber for near 6 weeks. Two [CO 2 ] (400 and 800 μmol mol -1 ), three water regimes (control and mild and moderate water stress) and four genotypes were assayed. For each combination of genotype, [CO 2 ] and water regime five plants were evaluated. Water stress applied caused significant decreases in water potential, net assimilation, stomatal conductance, intercellular to atmospheric [CO 2 ], and significant increases in water use efficiency, leaf chlorophyll content and carbon isotope composition, while the relative water content, the osmotic potential and the content of anthocyanins did change not under stress compared to control conditions support this statement. Nevertheless, water regime affects plant growth via nitrogen assimilation, which is associated with the transpiration stream, particularly at high [CO 2 ], while the lower N concentration caused by rising [CO 2 ] is not associated with stomatal closure. The stable isotope composition of carbon, oxygen, and nitrogen (δ 13 C, δ 18 O, and δ 15 N) in plant matter are affected not only by water regime but also by rising [CO 2 ]. Thus, δ 18 O increased probably as response to decreases in transpiration, while the increase in δ 15 N may reflect not only a lower stomatal conductance but a higher nitrogen demand in leaves or shifts in nitrogen metabolism associated with decreases in photorespiration. The way that δ 13 C explains differences in plant growth across water regimes within a given [CO 2 ], seems to be mediated through its direct relationship with N accumulation in leaves. The changes in the profile and amount of amino acids caused by water stress and high [CO 2 ] support this conclusion. However, the results do not support the use of δ 18 O as an indicator of the effect of water regime on plant growth.

Interactive Effects of CO2 Concentration and Water Regime on Stable Isotope Signatures, Nitrogen Assimilation and Growth in Sweet Pepper

PubMed Central

Serret, María D.; Yousfi, Salima; Vicente, Rubén; Piñero, María C.; Otálora-Alcón, Ginés; del Amor, Francisco M.; Araus, José L.

2018-01-01

Sweet pepper is among the most widely cultivated horticultural crops in the Mediterranean basin, being frequently grown hydroponically under cover in combination with CO2 fertilization and water conditions ranging from optimal to suboptimal. The aim of this study is to develop a simple model, based on the analysis of plant stable isotopes in their natural abundance, gas exchange traits and N concentration, to assess sweet pepper growth. Plants were grown in a growth chamber for near 6 weeks. Two [CO2] (400 and 800 μmol mol−1), three water regimes (control and mild and moderate water stress) and four genotypes were assayed. For each combination of genotype, [CO2] and water regime five plants were evaluated. Water stress applied caused significant decreases in water potential, net assimilation, stomatal conductance, intercellular to atmospheric [CO2], and significant increases in water use efficiency, leaf chlorophyll content and carbon isotope composition, while the relative water content, the osmotic potential and the content of anthocyanins did change not under stress compared to control conditions support this statement. Nevertheless, water regime affects plant growth via nitrogen assimilation, which is associated with the transpiration stream, particularly at high [CO2], while the lower N concentration caused by rising [CO2] is not associated with stomatal closure. The stable isotope composition of carbon, oxygen, and nitrogen (δ13C, δ18O, and δ15N) in plant matter are affected not only by water regime but also by rising [CO2]. Thus, δ18O increased probably as response to decreases in transpiration, while the increase in δ15N may reflect not only a lower stomatal conductance but a higher nitrogen demand in leaves or shifts in nitrogen metabolism associated with decreases in photorespiration. The way that δ13C explains differences in plant growth across water regimes within a given [CO2], seems to be mediated through its direct relationship with N accumulation in leaves. The changes in the profile and amount of amino acids caused by water stress and high [CO2] support this conclusion. However, the results do not support the use of δ18O as an indicator of the effect of water regime on plant growth. PMID:29354140

The Use of Split-Thickness Skin Grafts on Diabetic Foot Ulcerations: A Literature Review

PubMed Central

McCartan, Brant; Dinh, Thanh

2012-01-01

Diabetic foot ulcerations are historically difficult to treat despite advanced therapeutic modalities. There are numerous modalities described in the literature ranging from noninvasive topical wound care to more invasive surgical procedures such as primary closure, skin flaps, and skin grafting. While skin grafting provides faster time to closure with a single treatment compared to traditional topical wound treatments, the potential risks of donor site morbidity and poor wound healing unique to the diabetic state have been cited as a contraindication to its widespread use. In order to garner clarity on this issue, a literature review was undertaken on the use of split-thickness skin grafts on diabetic foot ulcers. Search of electronic databases yielded four studies that reported split-thickness skin grafts as definitive means of closure. In addition, several other studies employed split-thickness skin grafts as an adjunct to a treatment that was only partially successful or used to fill in the donor site of another plastic surgery technique. When used as the primary closure on optimized diabetic foot ulcerations, split-thickness skin grafts are 78% successful at closing 90% of the wound by eight weeks. PMID:22666573

Computational Modeling and Simulation of Genital Tubercle Development

EPA Pesticide Factsheets

Hypospadias is a developmental defect of urethral tube closure that has a complex etiology involving genetic and environmental factors, including anti-androgenic and estrogenic disrupting chemicals; however, little is known about the morphoregulatory consequences of androgen/estrogen balance during genital tubercle (GT) development. Computer models that predictively model sexual dimorphism of the GT may provide a useful resource to translate chemical-target bipartite networks and their developmental consequences across the human-relevant chemical universe. Here, we describe a multicellular agent-based model of genital tubercle (GT) development that simulates urethrogenesis from the sexually-indifferent urethral plate stage to urethral tube closure. The prototype model, constructed in CompuCell3D, recapitulates key aspects of GT morphogenesis controlled by SHH, FGF10, and androgen pathways through modulation of stochastic cell behaviors, including differential adhesion, motility, proliferation, and apoptosis. Proper urethral tube closure in the model was shown to depend quantitatively on SHH- and FGF10-induced effects on mesenchymal proliferation and epithelial apoptosis??both ultimately linked to androgen signaling. In the absence of androgen, GT development was feminized and with partial androgen deficiency, the model resolved with incomplete urethral tube closure, thereby providing an in silico platform for probabilistic prediction of hypospadias risk across c

Multi-Material Closure Model for High-Order Finite Element Lagrangian Hydrodynamics

DOE PAGES

Dobrev, V. A.; Kolev, T. V.; Rieben, R. N.; ...

2016-04-27

We present a new closure model for single fluid, multi-material Lagrangian hydrodynamics and its application to high-order finite element discretizations of these equations [1]. The model is general with respect to the number of materials, dimension and space and time discretizations. Knowledge about exact material interfaces is not required. Material indicator functions are evolved by a closure computation at each quadrature point of mixed cells, which can be viewed as a high-order variational generalization of the method of Tipton [2]. This computation is defined by the notion of partial non-instantaneous pressure equilibration, while the full pressure equilibration is achieved bymore » both the closure model and the hydrodynamic motion. Exchange of internal energy between materials is derived through entropy considerations, that is, every material produces positive entropy, and the total entropy production is maximized in compression and minimized in expansion. Results are presented for standard one-dimensional two-material problems, followed by two-dimensional and three-dimensional multi-material high-velocity impact arbitrary Lagrangian–Eulerian calculations. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.« less

Near-wall effects for momentum, heat and mass transport in gas-particle suspensions at moderate Reynolds numbers

NASA Astrophysics Data System (ADS)

Radl, Stefan; Municchi, Federico; Goniva, Christoph

2016-11-01

Understanding transport phenomena in fluid-particle systems is of primary importance for the design of large-scale equipment, e.g., in the chemical industry. Typically, the analysis of such systems is performed by numerically solving a set of partial differential equations modeling the particle phase and the fluid phase as interpenetrating continua. Such models require a number of closure models that are often constructed via spatial filtering of data obtained from particle-resolved direct numerical simulations (PR-DNS). In the present work we make use of PR-DNS to evaluate corrections to existing closure models. Specifically, we aim on accounting for wall effects on the fluid-particle drag force and the particle-individual Nusselt number. We then propose an improved closure model to be used in particle-unresolved Euler-Lagrange (PU-EL) simulations. We demonstrate that such an advanced closure should account for a dimensionless filter size, as well as a normalized distance from the wall. In addition, we make an attempt to model the filtered fluid velocity profile in wall-bounded suspension flows. The authors acknowledge funding from the European Commission through FP7 Grant Agreement No. 604656, as well as VSC-3 and dcluster.tugraz.at.

Multi-Material Closure Model for High-Order Finite Element Lagrangian Hydrodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dobrev, V. A.; Kolev, T. V.; Rieben, R. N.

We present a new closure model for single fluid, multi-material Lagrangian hydrodynamics and its application to high-order finite element discretizations of these equations [1]. The model is general with respect to the number of materials, dimension and space and time discretizations. Knowledge about exact material interfaces is not required. Material indicator functions are evolved by a closure computation at each quadrature point of mixed cells, which can be viewed as a high-order variational generalization of the method of Tipton [2]. This computation is defined by the notion of partial non-instantaneous pressure equilibration, while the full pressure equilibration is achieved bymore » both the closure model and the hydrodynamic motion. Exchange of internal energy between materials is derived through entropy considerations, that is, every material produces positive entropy, and the total entropy production is maximized in compression and minimized in expansion. Results are presented for standard one-dimensional two-material problems, followed by two-dimensional and three-dimensional multi-material high-velocity impact arbitrary Lagrangian–Eulerian calculations. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.« less

Salicaceae Endophytes Modulate Stomatal Behavior and Increase Water Use Efficiency in Rice

PubMed Central

Rho, Hyungmin; Van Epps, Victor; Wegley, Nicholas; Doty, Sharon L.; Kim, Soo-Hyung

2018-01-01

Bacterial and yeast endophytes isolated from the Salicaceae family have been shown to promote growth and alleviate stress in plants from different taxa. To determine the physiological pathways through which endophytes affect plant water relations, we investigated leaf water potential, whole-plant water use, and stomatal responses of rice plants to Salicaceae endophyte inoculation under CO2 enrichment and water deficit. Daytime stomatal conductance and stomatal density were lower in inoculated plants compared to controls. Leaf ABA concentrations increased with endophyte inoculation. As a result, transpirational water use decreased significantly with endophyte inoculation while biomass did not change or slightly increased. This response led to a significant increase in cumulative water use efficiency at harvest. Different endophyte strains produced the same results in host plant water relations and stomatal responses. These stomatal responses were also observed under elevated CO2 conditions, and the increase in water use efficiency was more pronounced under water deficit conditions. The effect on water use efficiency was positively correlated with daily light integrals across different experiments. Our results provide insights on the physiological mechanisms of plant-endophyte interactions involving plant water relations and stomatal functions. PMID:29552021

Increased sink strength offsets the inhibitory effect of sucrose on sugarcane photosynthesis.

PubMed

Ribeiro, Rafael V; Machado, Eduardo C; Magalhães Filho, José R; Lobo, Ana Karla M; Martins, Márcio O; Silveira, Joaquim A G; Yin, Xinyou; Struik, Paul C

2017-01-01

Spraying sucrose inhibits photosynthesis by impairing Rubisco activity and stomatal conductance (g s ), whereas increasing sink demand by partially darkening the plant stimulates sugarcane photosynthesis. We hypothesized that the stimulatory effect of darkness can offset the inhibitory effect of exogenous sucrose on photosynthesis. Source-sink relationship was perturbed in two sugarcane cultivars by imposing partial darkness, spraying a sucrose solution (50mM) and their combination. Five days after the onset of the treatments, the maximum Rubisco carboxylation rate (V cmax ) and the initial slope of A-C i curve (k) were estimated by measuring leaf gas exchange and chlorophyll fluorescence. Photosynthesis was inhibited by sucrose spraying in both genotypes, through decreases in V cmax , k, g s and ATP production driven by electron transport (J atp ). Photosynthesis of plants subjected to the combination of partial darkness and sucrose spraying was similar to photosynthesis of reference plants for both genotypes. Significant increases in V cmax , g s and J atp and marginal increases in k were noticed when combining partial darkness and sucrose spraying compared with sucrose spraying alone. Our data also revealed that increases in sink strength due to partial darkness offset the inhibition of sugarcane photosynthesis caused by sucrose spraying, enhancing the knowledge on endogenous regulation of sugarcane photosynthesis through the source-sink relationship. Copyright © 2016 Elsevier GmbH. All rights reserved.

Transmission and pathogenesis of vesicular stomatitis viruses

USDA-ARS?s Scientific Manuscript database

Vesicular Stomatitis (VS) is caused by the Vesicular Stomatitis Virus (VSV), a negative single stranded RNA arthropod-borne virus member of the Family Rhabdoviridae. The virion is composed of the host derived plasma membrane, the envelope, and an internal ribonucleoprotein core. The envelope contain...

Relating Stomatal Conductance to Leaf Functional Traits.

PubMed

Kröber, Wenzel; Plath, Isa; Heklau, Heike; Bruelheide, Helge

2015-10-12

Leaf functional traits are important because they reflect physiological functions, such as transpiration and carbon assimilation. In particular, morphological leaf traits have the potential to summarize plants strategies in terms of water use efficiency, growth pattern and nutrient use. The leaf economics spectrum (LES) is a recognized framework in functional plant ecology and reflects a gradient of increasing specific leaf area (SLA), leaf nitrogen, phosphorus and cation content, and decreasing leaf dry matter content (LDMC) and carbon nitrogen ratio (CN). The LES describes different strategies ranging from that of short-lived leaves with high photosynthetic capacity per leaf mass to long-lived leaves with low mass-based carbon assimilation rates. However, traits that are not included in the LES might provide additional information on the species' physiology, such as those related to stomatal control. Protocols are presented for a wide range of leaf functional traits, including traits of the LES, but also traits that are independent of the LES. In particular, a new method is introduced that relates the plants' regulatory behavior in stomatal conductance to vapor pressure deficit. The resulting parameters of stomatal regulation can then be compared to the LES and other plant functional traits. The results show that functional leaf traits of the LES were also valid predictors for the parameters of stomatal regulation. For example, leaf carbon concentration was positively related to the vapor pressure deficit (vpd) at the point of inflection and the maximum of the conductance-vpd curve. However, traits that are not included in the LES added information in explaining parameters of stomatal control: the vpd at the point of inflection of the conductance-vpd curve was lower for species with higher stomatal density and higher stomatal index. Overall, stomata and vein traits were more powerful predictors for explaining stomatal regulation than traits used in the LES.

Drawing the future

PubMed Central

2008-01-01

Gas exchange between the plant and the atmosphere is regulated by controlling both the stomatal density and the aperture of the stomatal pore. Environmental factors such as light, the level of atmospheric CO2 and hormones regulate stomatal development and/or function. Because atmospheric CO2 levels have been rising since the Industrial Revolution, and it is predicted that they will continue doing so in the future, an understanding of the CO2 signalling mechanisms in the stomatal responses will help to know how plants were in the past and will allow predicting how they will respond to climate change in the near future. This article covers the recent knowledge of the CO2 signalling mechanisms that regulate both stomatal function and development. PMID:19513216

Opinion: the red-light response of stomatal movement is sensed by the redox state of the photosynthetic electron transport chain.

PubMed

Busch, Florian A

2014-02-01

Guard cells regulate CO2 uptake and water loss of a leaf by controlling stomatal movement in response to environmental factors such as CO2, humidity, and light. The mechanisms by which stomata respond to red light are actively debated in the literature, and even after decades of research it is still controversial whether stomatal movement is related to photosynthesis or not. This review summarizes the current knowledge of the red-light response of stomata. A comparison of published evidence suggests that stomatal movement is controlled by the redox state of photosynthetic electron transport chain components, in particular the redox state of plastoquinone. Potential consequences for the modeling of stomatal conductance are discussed.

Genetic and antigenic relationships of veicular stomatitis viruses from South America

USDA-ARS?s Scientific Manuscript database

Vesicular stomatitis (VS) viruses have beenclassified into two serotypes: New Jersey (VSNJV) and Indiana (VSIV). Here, we have characterized field isolates causing vesicular stomatitis in Brazil and Argentina over a 35-year span. Cluster analysis based on either serological relatedness, as inferred ...

Ozone risk assessment for agricultural crops in Europe: Further development of stomatal flux and flux-response relationships for European wheat and potato

NASA Astrophysics Data System (ADS)

Pleijel, H.; Danielsson, H.; Emberson, L.; Ashmore, M. R.; Mills, G.

Applications of a parameterised Jarvis-type multiplicative stomatal conductance model with data collated from open-top chamber experiments on field grown wheat and potato were used to derive relationships between relative yield and stomatal ozone uptake. The relationships were based on thirteen experiments from four European countries for wheat and seven experiments from four European countries for potato. The parameterisation of the conductance model was based both on an extensive literature review and primary data. Application of the stomatal conductance models to the open-top chamber experiments resulted in improved linear regressions between relative yield and ozone uptake compared to earlier stomatal conductance models, both for wheat ( r2=0.83) and potato ( r2=0.76). The improvement was largest for potato. The relationships with the highest correlation were obtained using a stomatal ozone flux threshold. For both wheat and potato the best performing exposure index was AF st6 (accumulated stomatal flux of ozone above a flux rate threshold of 6 nmol ozone m -2 projected sunlit leaf area, based on hourly values of ozone flux). The results demonstrate that flux-based models are now sufficiently well calibrated to be used with confidence to predict the effects of ozone on yield loss of major arable crops across Europe. Further studies, using innovations in stomatal conductance modelling and plant exposure experimentation, are needed if these models are to be further improved.

Spatial and Temporal Relationships of Stomatal Development and Function in a Temperate Forest Canopy

NASA Astrophysics Data System (ADS)

Dow, G.; Richardson, A. D.

2017-12-01

Mechanisms that control stomatal development ultimately constrain leaf physiology by determining the anatomical maximum rate for gas-exchange (gsmax). However, we know comparatively less about how these regulatory processes define stomatal conductance (gs) and photosynthesis or how this information translates between model systems and important crop or native plant species. Here, we test relationships between stomatal development and leaf physiology that have been established in model systems by sampling trees in a mature forest ecosystem. We found that plasticity in gsmax was limited throughout the canopy, despite other changes in leaf structure and function that are driven by environmental gradients in the canopy. However, the ratio between gs and gsmax was predictive of gas flux in the canopy and species-independent. Variation in the gs : gsmax ratio appeared to minimize the energy required to control aperture size via guard cell turgor pressure, thus compensating for the initial over-investment in stomatal production. gsmax also remained a strong predictor of photosynthetic potential and intrinsic water-use efficiency. The temporal relationship between gsmax and these functional leaf traits might depend on long-term adjustments in stomatal development, which was sensitive to increases in atmospheric CO2 in our study. The absence of a spatial response and the presence of a temporal response in stomatal development infers that multiple mechanisms may integrate environmental signaling in the developmental pathway. Collectively, this research helps to define the larger significance of the stomatal mechanisms being identified in model systems.

A Modeling Approach to Quantify the Effects of Stomatal Behavior and Mesophyll Conductance on Leaf Water Use Efficiency

PubMed Central

Moualeu-Ngangue, Dany P.; Chen, Tsu-Wei; Stützel, Hartmut

2016-01-01

Water use efficiency (WUE) is considered as a determinant of yield under stress and a component of crop drought resistance. Stomatal behavior regulates both transpiration rate and net assimilation and has been suggested to be crucial for improving crop WUE. In this work, a dynamic model was used to examine the impact of dynamic properties of stomata on WUE. The model includes sub-models of stomatal conductance dynamics, solute accumulation in the mesophyll, mesophyll water content, and water flow to the mesophyll. Using the instantaneous value of stomatal conductance, photosynthesis, and transpiration rate were simulated using a biochemical model and Penman-Monteith equation, respectively. The model was parameterized for a cucumber leaf and model outputs were evaluated using climatic data. Our simulations revealed that WUE was higher on a cloudy than a sunny day. Fast stomatal reaction to light decreased WUE during the period of increasing light (e.g., in the morning) by up to 10.2% and increased WUE during the period of decreasing light (afternoon) by up to 6.25%. Sensitivity of daily WUE to stomatal parameters and mesophyll conductance to CO2 was tested for sunny and cloudy days. Increasing mesophyll conductance to CO2 was more likely to increase WUE for all climatic conditions (up to 5.5% on the sunny day) than modifications of stomatal reaction speed to light and maximum stomatal conductance. PMID:27379150

Stomatal response of swordfern to volcanogenic CO2 and SO2 from Kilauea volcano

NASA Astrophysics Data System (ADS)

Tanner, Lawrence H.; Smith, David L.; Allan, Amanda

2007-08-01

The experimentally determined relationship between atmospheric pCO2 and plant stomata has been used to interpret large but transient changes in atmospheric composition, such as may have resulted from the eruptions of flood basalt. However, this relationship has not been tested in the field, i.e. in the vicinity of active volcanoes, to examine the specific effects of volcanogenic emissions. Moreover, the interpretation of paleoatmospheric pCO2 from fossil stomatal data assumes that the stomatal response resulted solely from variation in pCO2 and ignores the potential effect of outgassed SO2. We hypothesize that volcanogenic SO2 also has a significant effect on leaf stomata and test this hypothesis by measuring the stomatal index of the common swordfern (Nephrolepis exaltata) in the plumes of the actively outgassing vents of Kilauea volcano. We find that, compared to control locations, stomatal index is lowest at sample sites in the plume of Halema'uma'u Crater, where concentrations of both CO2 and SO2 are much higher than background. However, sites located directly in the plume of Pu'u O'o, where SO2 levels are high, but CO2 levels are not, also yield low values of stomatal index. We propose that shifts in the stomatal index of fossil leaves may record transient atmospheric increases in both SO2 and CO2, such as may be caused by eruptions of flood basalts. Calculations of pCO2 based on stomatal frequency are likely to be exaggerated.

Experimental infection of Didelphis marsupialis with Vesicular Stomatitis New Jersey Virus

USDA-ARS?s Scientific Manuscript database

Although vesicular stomatitis has been present for many years in the Americas, many aspects of its natural history remain undefined. In this study we challenged five adult Virginia opossums (Didelphis marsupialis) with vesicular stomatitis New Jersey serotype virus (VSNJV). Opossums had no detecta...

Modeling stomatal conductance in the Earth system: linking leaf water-use efficiency and water transport along the soil-plant-atmosphere continuum

NASA Astrophysics Data System (ADS)

Bonan, G. B.; Williams, M.; Fisher, R. A.; Oleson, K. W.

2014-05-01

The empirical Ball-Berry stomatal conductance model is commonly used in Earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must both be empirically parameterized. We evaluated the Ball-Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil-plant-atmosphere continuum (SPA) to numerically optimize photosynthetic carbon gain per unit water loss while preventing leaf water potential dropping below a critical minimum level. We evaluated two alternative optimization algorithms: intrinsic water-use efficiency (Δ An/Δ gs, the marginal carbon gain of stomatal opening) and water-use efficiency (Δ An/Δ El, the marginal carbon gain of water loss). We implemented the stomatal models in a multi-layer plant canopy model, to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using: (1) leaf analyses; (2) canopy net radiation, sensible heat flux, latent heat flux, and gross primary production at six AmeriFlux sites spanning 51 site-years; and (3) parameter sensitivity analyses. Without soil moisture stress, the performance of the SPA stomatal conductance model was generally comparable to or somewhat better than the Ball-Berry model in flux tower simulations, but was significantly better than the Ball-Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from the physiological theory linking leaf water-use efficiency and water flow to and from the leaf along the soil-to-leaf pathway rather than being imposed a priori, as in the Ball-Berry model. Similar functional dependence of gs on Ds emerged from the water-use efficiency optimization. Sensitivity analyses showed that two parameters (stomatal efficiency and root hydraulic conductivity) minimized errors with the SPA stomatal conductance model. The critical stomatal efficiency for optimization (ι) was estimated from leaf trait datasets and is related to the slope parameter (g1) of the Ball-Berry model. The optimized parameter value was consistent with this estimate. Optimized root hydraulic conductivity was consistent with estimates from literature surveys. The two central concepts embodied in the stomatal model, that plants account for both water-use efficiency and for hydraulic safety in regulating stomatal conductance, imply a notion of optimal plant strategies and provide testable model hypotheses, rather than empirical descriptions of plant behavior.

TOO MANY MOUTHS promotes cell fate progression in stomatal development of Arabidopsis stems.

PubMed

Bhave, Neela S; Veley, Kira M; Nadeau, Jeanette A; Lucas, Jessica R; Bhave, Sanjay L; Sack, Fred D

2009-01-01

Mutations in TOO MANY MOUTHS (TMM), which encodes a receptor-like protein, cause stomatal patterning defects in Arabidopsis leaves but eliminate stomatal formation in stems. Stomatal development in wild-type and tmm stems was analyzed to define TMM function. Epidermal cells in young tmm stems underwent many asymmetric divisions characteristic of entry into the stomatal pathway. The resulting precursor cells, meristemoids, appropriately expressed cell fate markers such as pTMM:GFP. However, instead of progressing developmentally by forming a guard mother cell, the meristemoids arrested, dedifferentiated, and enlarged. Thus asymmetric divisions are necessary but not sufficient for stomatal formation in stems, and TMM promotes the fate and developmental progression of early precursor cells. Comparable developmental and mature stomatal phenotypes were also found in tmm hypocotyls and in the proximal flower stalk. TMM is also a positive regulator of meristemoid division in leaves suggesting that TMM generally promotes meristemoid activity. Our results are consistent with a model in which TMM interacts with other proteins to modulate precursor cell fate and progression in an organ and domain-specific manner. Finally, the consistent presence of a small number of dedifferentiated meristemoids in mature wild-type stems suggests that precursor cell arrest is a normal feature of Arabidopsis stem development.

Phenomics allows identification of genomic regions affecting maize stomatal conductance with conditional effects of water deficit and evaporative demand.

PubMed

Prado, Santiago Alvarez; Cabrera-Bosquet, Llorenç; Grau, Antonin; Coupel-Ledru, Aude; Millet, Emilie J; Welcker, Claude; Tardieu, François

2018-02-01

Stomatal conductance is central for the trades-off between hydraulics and photosynthesis. We aimed at deciphering its genetic control and that of its responses to evaporative demand and water deficit, a nearly impossible task with gas exchanges measurements. Whole-plant stomatal conductance was estimated via inversion of the Penman-Monteith equation from data of transpiration and plant architecture collected in a phenotyping platform. We have analysed jointly 4 experiments with contrasting environmental conditions imposed to a panel of 254 maize hybrids. Estimated whole-plant stomatal conductance closely correlated with gas-exchange measurements and biomass accumulation rate. Sixteen robust quantitative trait loci (QTLs) were identified by genome wide association studies and co-located with QTLs of transpiration and biomass. Light, vapour pressure deficit, or soil water potential largely accounted for the differences in allelic effects between experiments, thereby providing strong hypotheses for mechanisms of stomatal control and a way to select relevant candidate genes among the 1-19 genes harboured by QTLs. The combination of allelic effects, as affected by environmental conditions, accounted for the variability of stomatal conductance across a range of hybrids and environmental conditions. This approach may therefore contribute to genetic analysis and prediction of stomatal control in diverse environments. © 2017 John Wiley & Sons Ltd.

Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation

DOE PAGES

Garcia-Forner, Nuria; Adams, Henry D.; Sevanto, Sanna; ...

2015-08-08

Here, relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P.more » edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.« less

Sucrose breakdown within guard cells provides substrates for glycolysis and glutamine biosynthesis during light-induced stomatal opening.

PubMed

Medeiros, David B; Perez Souza, Leonardo; Antunes, Werner C; Araújo, Wagner L; Daloso, Danilo M; Fernie, Alisdair R

2018-05-01

Sucrose has long been thought to play an osmolytic role in stomatal opening. However, recent evidence supports the idea that the role of sucrose in this process is primarily energetic. Here we used a combination of stomatal aperture assays and kinetic [U- 13 C]-sucrose isotope labelling experiments to confirm that sucrose is degraded during light-induced stomatal opening and to define the fate of the C released from sucrose breakdown. We additionally show that addition of sucrose to the medium did not enhance light-induced stomatal opening. The isotope experiment showed a consistent 13 C enrichment in fructose and glucose, indicating that during light-induced stomatal opening sucrose is indeed degraded. We also observed a clear 13 C enrichment in glutamate and glutamine (Gln), suggesting a concerted activation of sucrose degradation, glycolysis and the tricarboxylic acid cycle. This is in contrast to the situation for Gln biosynthesis in leaves under light, which has been demonstrated to rely on previously stored C. Our results thus collectively allow us to redraw current models concerning the influence of sucrose during light-induced stomatal opening, in which, instead of being accumulated, sucrose is degraded providing C skeletons for Gln biosynthesis. © 2018 The Authors The Plant Journal © 2018 John Wiley & Sons Ltd.

Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia-Forner, Nuria; Adams, Henry D.; Sevanto, Sanna

Here, relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P.more » edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies.« less

Crosstalk between the Circadian Clock and Innate Immunity in Arabidopsis

PubMed Central

Zhang, Chong; Xie, Qiguang; Anderson, Ryan G.; Ng, Gina; Seitz, Nicholas C.; Peterson, Thomas; McClung, C. Robertson; McDowell, John M.; Kong, Dongdong; Kwak, June M.; Lu, Hua

2013-01-01

The circadian clock integrates temporal information with environmental cues in regulating plant development and physiology. Recently, the circadian clock has been shown to affect plant responses to biotic cues. To further examine this role of the circadian clock, we tested disease resistance in mutants disrupted in CCA1 and LHY, which act synergistically to regulate clock activity. We found that cca1 and lhy mutants also synergistically affect basal and resistance gene-mediated defense against Pseudomonas syringae and Hyaloperonospora arabidopsidis. Disrupting the circadian clock caused by overexpression of CCA1 or LHY also resulted in severe susceptibility to P. syringae. We identified a downstream target of CCA1 and LHY, GRP7, a key constituent of a slave oscillator regulated by the circadian clock and previously shown to influence plant defense and stomatal activity. We show that the defense role of CCA1 and LHY against P. syringae is at least partially through circadian control of stomatal aperture but is independent of defense mediated by salicylic acid. Furthermore, we found defense activation by P. syringae infection and treatment with the elicitor flg22 can feedback-regulate clock activity. Together this data strongly supports a direct role of the circadian clock in defense control and reveal for the first time crosstalk between the circadian clock and plant innate immunity. PMID:23754942

MicroRNA156 improves drought stress tolerance in alfalfa (Medicago sativa) by silencing SPL13.

PubMed

Arshad, Muhammad; Feyissa, Biruk A; Amyot, Lisa; Aung, Banyar; Hannoufa, Abdelali

2017-05-01

Alfalfa (Medicago sativa) is an important forage crop that is often grown in areas that frequently experience drought and water shortage. MicroRNA156 (miR156) is an emerging tool for improving various traits in plants. We tested the role of miR156d in drought response of alfalfa, and observed a significant improvement in drought tolerance of miR156 overexpression (miR156OE) alfalfa genotypes compared to the wild type control (WT). In addition to higher survival and reduced water loss, miR156OE genotypes also maintained higher stomatal conductance compared to WT during drought stress. Furthermore, we observed an enhanced accumulation of compatible solute (proline) and increased levels of abscisic acid (ABA) and antioxidants in miR156OE genotypes. Similarly, alfalfa plants with reduced expression of miR156-targeted SPL13 showed reduced water loss and enhanced stomatal conductance, chlorophyll content and photosynthetic assimilation. Several genes known to be involved in drought tolerance were differentially expressed in leaf and root of miR156 overexpression plants. Taken together, our findings reveal that miR156 improves drought tolerance in alfalfa at least partially by silencing SPL13. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Reintroducing radiometric surface temperature into the Penman-Monteith formulation

NASA Astrophysics Data System (ADS)

Mallick, Kaniska; Boegh, Eva; Trebs, Ivonne; Alfieri, Joseph G.; Kustas, William P.; Prueger, John H.; Niyogi, Dev; Das, Narendra; Drewry, Darren T.; Hoffmann, Lucien; Jarvis, Andrew J.

2015-08-01

Here we demonstrate a novel method to physically integrate radiometric surface temperature (TR) into the Penman-Monteith (PM) formulation for estimating the terrestrial sensible and latent heat fluxes (H and λE) in the framework of a modified Surface Temperature Initiated Closure (STIC). It combines TR data with standard energy balance closure models for deriving a hybrid scheme that does not require parameterization of the surface (or stomatal) and aerodynamic conductances (gS and gB). STIC is formed by the simultaneous solution of four state equations and it uses TR as an additional data source for retrieving the "near surface" moisture availability (M) and the Priestley-Taylor coefficient (α). The performance of STIC is tested using high-temporal resolution TR observations collected from different international surface energy flux experiments in conjunction with corresponding net radiation (RN), ground heat flux (G), air temperature (TA), and relative humidity (RH) measurements. A comparison of the STIC outputs with the eddy covariance measurements of λE and H revealed RMSDs of 7-16% and 40-74% in half-hourly λE and H estimates. These statistics were 5-13% and 10-44% in daily λE and H. The errors and uncertainties in both surface fluxes are comparable to the models that typically use land surface parameterizations for determining the unobserved components (gS and gB) of the surface energy balance models. However, the scheme is simpler, has the capabilities for generating spatially explicit surface energy fluxes and independent of submodels for boundary layer developments. This article was corrected on 27 AUG 2015. See the end of the full text for details.

Phototropins But Not Cryptochromes Mediate the Blue Light-Specific Promotion of Stomatal Conductance, While Both Enhance Photosynthesis and Transpiration under Full Sunlight12[C][W][OA

PubMed Central

Boccalandro, Hernán E.; Giordano, Carla V.; Ploschuk, Edmundo L.; Piccoli, Patricia N.; Bottini, Rubén; Casal, Jorge J.

2012-01-01

Leaf epidermal peels of Arabidopsis (Arabidopsis thaliana) mutants lacking either phototropins 1 and 2 (phot1 and phot2) or cryptochromes 1 and 2 (cry1 and cry2) exposed to a background of red light show severely impaired stomatal opening responses to blue light. Since phot and cry are UV-A/blue light photoreceptors, they may be involved in the perception of the blue light-specific signal that induces the aperture of the stomatal pores. In leaf epidermal peels, the blue light-specific effect saturates at low irradiances; therefore, it is considered to operate mainly under the low irradiance of dawn, dusk, or deep canopies. Conversely, we show that both phot1 phot2 and cry1 cry2 have reduced stomatal conductance, transpiration, and photosynthesis, particularly under the high irradiance of full sunlight at midday. These mutants show compromised responses of stomatal conductance to irradiance. However, the effects of phot and cry on photosynthesis were largely nonstomatic. While the stomatal conductance phenotype of phot1 phot2 was blue light specific, cry1 cry2 showed reduced stomatal conductance not only in response to blue light, but also in response to red light. The levels of abscisic acid were elevated in cry1 cry2. We conclude that considering their effects at high irradiances cry and phot are critical for the control of transpiration and photosynthesis rates in the field. The effects of cry on stomatal conductance are largely indirect and involve the control of abscisic acid levels. PMID:22147516

Phototropins but not cryptochromes mediate the blue light-specific promotion of stomatal conductance, while both enhance photosynthesis and transpiration under full sunlight.

PubMed

Boccalandro, Hernán E; Giordano, Carla V; Ploschuk, Edmundo L; Piccoli, Patricia N; Bottini, Rubén; Casal, Jorge J

2012-03-01

Leaf epidermal peels of Arabidopsis (Arabidopsis thaliana) mutants lacking either phototropins 1 and 2 (phot1 and phot2) or cryptochromes 1 and 2 (cry1 and cry2) exposed to a background of red light show severely impaired stomatal opening responses to blue light. Since phot and cry are UV-A/blue light photoreceptors, they may be involved in the perception of the blue light-specific signal that induces the aperture of the stomatal pores. In leaf epidermal peels, the blue light-specific effect saturates at low irradiances; therefore, it is considered to operate mainly under the low irradiance of dawn, dusk, or deep canopies. Conversely, we show that both phot1 phot2 and cry1 cry2 have reduced stomatal conductance, transpiration, and photosynthesis, particularly under the high irradiance of full sunlight at midday. These mutants show compromised responses of stomatal conductance to irradiance. However, the effects of phot and cry on photosynthesis were largely nonstomatic. While the stomatal conductance phenotype of phot1 phot2 was blue light specific, cry1 cry2 showed reduced stomatal conductance not only in response to blue light, but also in response to red light. The levels of abscisic acid were elevated in cry1 cry2. We conclude that considering their effects at high irradiances cry and phot are critical for the control of transpiration and photosynthesis rates in the field. The effects of cry on stomatal conductance are largely indirect and involve the control of abscisic acid levels.

Nocturnal and daytime stomatal conductance respond to root-zone temperature in ‘Shiraz’ grapevines

PubMed Central

Rogiers, Suzy Y.; Clarke, Simon J.

2013-01-01

Background and Aims Daytime root-zone temperature may be a significant factor regulating water flux through plants. Water flux can also occur during the night but nocturnal stomatal response to environmental drivers such as root-zone temperature remains largely unknown. Methods Here nocturnal and daytime leaf gas exchange was quantified in ‘Shiraz’ grapevines (Vitis vinifera) exposed to three root-zone temperatures from budburst to fruit-set, for a total of 8 weeks in spring. Key Results Despite lower stomatal density, night-time stomatal conductance and transpiration rates were greater for plants grown in warm root-zones. Elevated root-zone temperature resulted in higher daytime stomatal conductance, transpiration and net assimilation rates across a range of leaf-to-air vapour pressure deficits, air temperatures and light levels. Intrinsic water-use efficiency was, however, lowest in those plants with warm root-zones. CO2 response curves of foliar gas exchange indicated that the maximum rate of electron transport and the maximum rate of Rubisco activity did not differ between the root-zone treatments, and therefore it was likely that the lower photosynthesis in cool root-zones was predominantly the result of a stomatal limitation. One week after discontinuation of the temperature treatments, gas exchange was similar between the plants, indicating a reversible physiological response to soil temperature. Conclusions In this anisohydric grapevine variety both night-time and daytime stomatal conductance were responsive to root-zone temperature. Because nocturnal transpiration has implications for overall plant water status, predictive climate change models using stomatal conductance will need to factor in this root-zone variable. PMID:23293018

Systems Analysis of Guard Cell Membrane Transport for Enhanced Stomatal Dynamics and Water Use Efficiency1[W][OPEN

PubMed Central

Wang, Yizhou; Hills, Adrian; Blatt, Michael R.

2014-01-01

Stomatal transpiration is at the center of a crisis in water availability and crop production that is expected to unfold over the next 20 to 30 years. Global water usage has increased 6-fold in the past 100 years, twice as fast as the human population, and is expected to double again before 2030, driven mainly by irrigation and agriculture. Guard cell membrane transport is integral to controlling stomatal aperture and offers important targets for genetic manipulation to improve crop performance. However, its complexity presents a formidable barrier to exploring such possibilities. With few exceptions, mutations that increase water use efficiency commonly have been found to do so with substantial costs to the rate of carbon assimilation, reflecting the trade-off in CO2 availability with suppressed stomatal transpiration. One approach yet to be explored in detail relies on quantitative systems analysis of the guard cell. Our deep knowledge of transport and homeostasis in these cells gives real substance to the prospect for reverse engineering of stomatal responses, using in silico design in directing genetic manipulation for improved water use and crop yields. Here we address this problem with a focus on stomatal kinetics, taking advantage of the OnGuard software and models of the stomatal guard cell recently developed for exploring stomatal physiology. Our analysis suggests that manipulations of single transporter populations are likely to have unforeseen consequences. Channel gating, especially of the dominant K+ channels, appears the most favorable target for experimental manipulation. PMID:24596330

Nocturnal and daytime stomatal conductance respond to root-zone temperature in 'Shiraz' grapevines.

PubMed

Rogiers, Suzy Y; Clarke, Simon J

2013-03-01

Daytime root-zone temperature may be a significant factor regulating water flux through plants. Water flux can also occur during the night but nocturnal stomatal response to environmental drivers such as root-zone temperature remains largely unknown. Here nocturnal and daytime leaf gas exchange was quantified in 'Shiraz' grapevines (Vitis vinifera) exposed to three root-zone temperatures from budburst to fruit-set, for a total of 8 weeks in spring. Despite lower stomatal density, night-time stomatal conductance and transpiration rates were greater for plants grown in warm root-zones. Elevated root-zone temperature resulted in higher daytime stomatal conductance, transpiration and net assimilation rates across a range of leaf-to-air vapour pressure deficits, air temperatures and light levels. Intrinsic water-use efficiency was, however, lowest in those plants with warm root-zones. CO(2) response curves of foliar gas exchange indicated that the maximum rate of electron transport and the maximum rate of Rubisco activity did not differ between the root-zone treatments, and therefore it was likely that the lower photosynthesis in cool root-zones was predominantly the result of a stomatal limitation. One week after discontinuation of the temperature treatments, gas exchange was similar between the plants, indicating a reversible physiological response to soil temperature. In this anisohydric grapevine variety both night-time and daytime stomatal conductance were responsive to root-zone temperature. Because nocturnal transpiration has implications for overall plant water status, predictive climate change models using stomatal conductance will need to factor in this root-zone variable.

Microswitch and Keyboard-Emulator Technology to Facilitate the Writing Performance of Persons with Extensive Motor Disabilities

ERIC Educational Resources Information Center

Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Green, Vanessa; Oliva, Doretta; Lang, Russell

2011-01-01

This study assessed the effectiveness of microswitches for simple responses (i.e., partial hand closure, vocalization, and hand stroking) and a keyboard emulator to facilitate the writing performance of three participants with extensive motor disabilities. The study was carried out according to an ABAB design. During the A phases, the participants…

Soybean grown under elevated CO2 benefits more under low temperature than high temperature stress: Varying response of photosynthetic limitations, leaf metabolites, growth, and seed yield.

PubMed

Xu, Guangli; Singh, Shardendu K; Reddy, Vangimalla R; Barnaby, Jinyoung Y; Sicher, Richard C; Li, Tian

2016-10-20

To evaluate the combined effect of temperature and CO 2 on photosynthetic processes, leaf metabolites and growth, soybean was grown under a controlled environment at low (22/18°C, LT), optimum (28/24°C, OT) and high (36/32°C HT) temperatures under ambient (400μmolmol -1 ; aCO 2 ) or elevated (800μmolmol -1 ; eCO 2 ) CO 2 concentrations during the reproductive stage. In general, the rate of photosynthesis (A), stomatal (g s ) and mesophyll (g m ) conductance, quantum yield of photosystem II, rates of maximum carboxylation (V Cmax ), and electron transport (J) increased with temperature across CO 2 levels. However, compared with OT, the percentage increases in these parameters at HT were lower than the observed decline at LT. The photosynthetic limitation at LT and OT was primarily caused by photo-biochemical processes (49-58%, L b ) followed by stomatal (27-32%, L s ) and mesophyll (15-19%, L m ) limitations. However, at HT, it was primarily caused by L s (41%) followed by L b (33%) and L m (26%). The dominance of L b at LT and OT was associated with the accumulation of non-structural carbohydrates (e.g., starch) and several organic acids, whereas this accumulation did not occur at HT, indicating increased metabolic activities. Compared with OT, biomass and seed yield declined more at HT than at LT. The eCO 2 treatment compensated for the temperature-stress effects on biomass but only partially compensated for the effects on seed yield, especially at HT. Photosynthetic downregulation at eCO 2 was possibly due to the accumulation of non-structural carbohydrates and the decrease in g s and A std (standard A measured at 400μmolmol -1 sub-stomatal CO 2 concentration), as well as the lack of CO 2 effect on g m , V Cmax , and J, and photosynthetic limitation. Thus, the photosynthetic limitation was temperature-dependent and was primarily influenced by the alteration in photo-biochemical processes and metabolic activities. Despite the inconsistent response of photosynthesis (or biomass accumulation) and seed yield, eCO 2 tended to fully or partially compensate for the adverse effect of the respective LT and HT stresses under well-watered and sufficient nutrient conditions. Copyright © 2016 Elsevier GmbH. All rights reserved.

Do fossil plants signal palaeoatmospheric carbon dioxide concentration in the geological past?

PubMed Central

McElwain, J. C.

1998-01-01

Fossil, subfossil, and herbarium leaves have been shown to provide a morphological signal of the atmospheric carbon dioxide environment in which they developed by means of their stomatal density and index. An inverse relationship between stomatal density/index and atmospheric carbon dioxide concentration has been documented for all the studies to date concerning fossil and subfossil material. Furthermore, this relationship has been demonstrated experimentally by growing plants under elevated and reducedcarbon dioxide concentrations. To date, the mechanism that controls the stomatal density response to atmospheric carbon dioxide concentration remains unknown. However, stomatal parameters of fossil plants have been successfully used as a proxy indicator of palaeo-carbon dioxide levels. This paper presents new estimates of palaeo-atmospheric carbon dioxide concentrations for the Middle Eocene (Lutetian), based on the stomatal ratios of fossil Lauraceae species from Bournemouth in England. Estimates of atmospheric carbon dioxide concentrations derived from stomatal data from plants of the Early Devonian, Late Carboniferous, Early Permian and Middle Jurassic ages are reviewed in the light of new data. Semi-quantitative palaeo-carbon dioxide estimates based on the stomatal ratio (a ratio of the stomatal index of a fossil plant to that of a selected nearest living equivalent) have in the past relied on the use of a Carboniferous standard. The application of a new standard based on the present-day carbon dioxide level is reported here for comparison. The resultant ranges of palaeo-carbon dioxide estimates made from standardized fossil stomatal ratio data are in good agreement with both carbon isotopic data from terrestrial and marine sources and long-term carbon cycle modelling estimates for all the time periods studied. These data indicate elevated atmospheric carbon dioxide concentrations during the Early Devonian, Middle Jurassic and Middle Eocene, and reduced concentrations during the Late Carboniferous and Early Permian. Such data are important in demonstrating the long-term responses of plants to changing carbon dioxide concentrations and in contributing to the database needed for general circulation model climatic analogues.

Intraspecific variation in stomatal traits, leaf traits and physiology reflects adaptation along aridity gradients in a South African shrub

PubMed Central

Carlson, Jane E.; Adams, Christopher A.; Holsinger, Kent E.

2016-01-01

Background and Aims Trait–environment relationships are commonly interpreted as evidence for local adaptation in plants. However, even when selection analyses support this interpretation, the mechanisms underlying differential benefits are often unknown. This study addresses this gap in knowledge using the broadly distributed South African shrub Protea repens. Specifically, the study examines whether broad-scale patterns of trait variation are consistent with spatial differences in selection and ecophysiology in the wild. Methods In a common garden study of plants sourced from 19 populations, associations were measured between five morphological traits and three axes describing source climates. Trait–trait and trait–environment associations were analysed in a multi-response model. Within two focal populations in the wild, selection and path analyses were used to test associations between traits, fecundity and physiological performance. Key Results Across 19 populations in a common garden, stomatal density increased with the source population’s mean annual temperature and decreased with its average amount of rainfall in midsummer. Concordantly, selection analysis in two natural populations revealed positive selection on stomatal density at the hotter, drier site, while failing to detect selection at the cooler, moister site. Dry-site plants with high stomatal density also had higher stomatal conductances, cooler leaf temperatures and higher light-saturated photosynthetic rates than those with low stomatal density, but no such relationships were present among wet-site plants. Leaf area, stomatal pore index and specific leaf area in the garden also co-varied with climate, but within-population differences were not associated with fitness in either wild population. Conclusions The parallel patterns of broad-scale variation, differences in selection and differences in trait–ecophysiology relationships suggest a mechanism for adaptive differentiation in stomatal density. Densely packed stomata may improve performance by increasing transpiration and cooling, but predominately in drier, hotter climates. This study uniquely shows context-dependent benefits of stomatal density – a trait rarely linked to local adaptation in plants. PMID:26424782

Dynamics of canopy stomatal conductance, transpiration, and evaporation in a temperate deciduous forest, validated by carbonyl sulfide uptake

DOE PAGES

Wehr, Richard; Commane, Roisin; Munger, J. William; ...

2017-01-26

Stomatal conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface–atmosphere energy exchange. The environmental response of stomatal conductance has been measured mainly on the leaf scale, and theoretical canopy models are relied on to upscale stomatal conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate stomatal conductance and associated transpiration in a temperate deciduous forest directly on the canopy scale via two independent approaches: (i) from heat and water vapor exchange and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem–atmosphere exchange ofmore » OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy stomatal conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy stomatal conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where stomatal conductance shows declining marginal increases) and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on stomatal conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counterintuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of the two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is needed to further model development and improve our understanding of carbon and water cycling.« less

Dynamics of canopy stomatal conductance, transpiration, and evaporation in a temperate deciduous forest, validated by carbonyl sulfide uptake

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wehr, Richard; Commane, Roisin; Munger, J. William

Stomatal conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface–atmosphere energy exchange. The environmental response of stomatal conductance has been measured mainly on the leaf scale, and theoretical canopy models are relied on to upscale stomatal conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate stomatal conductance and associated transpiration in a temperate deciduous forest directly on the canopy scale via two independent approaches: (i) from heat and water vapor exchange and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem–atmosphere exchange ofmore » OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy stomatal conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy stomatal conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where stomatal conductance shows declining marginal increases) and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on stomatal conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counterintuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of the two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is needed to further model development and improve our understanding of carbon and water cycling.« less

Ferns are less dependent on passive dilution by cell expansion to coordinate leaf vein and stomatal spacing than angiosperms

PubMed Central

Jordan, Gregory J.; Brodribb, Timothy J.

2017-01-01

Producing leaves with closely spaced veins is a key innovation linked to high rates of photosynthesis in angiosperms. A close geometric link between veins and stomata in angiosperms ensures that investment in enhanced venous water transport provides the strongest net carbon return to the plant. This link is underpinned by “passive dilution” via expansion of surrounding cells. However, it is not known whether this ‘passive dilution’ mechanism is present in plant lineages other than angiosperms and is another key feature of the angiosperms’ evolutionary success. Consequently, we sought to determine whether the ‘passive dilution’ mechanism is; (i) exclusive to the angiosperms, (ii) a conserved mechanism that evolved in the common ancestor of ferns and angiosperms, or (iii) has evolved continuously over time. To do this we first we assessed the plasticity of vein and stomatal density and epidermal cell size in ferns in response to light environment. We then compared the relationships between these traits found among ferns with modelled relationships that assume vein and stomatal density respond passively to epidermal cell expansion, and with those previously observed in angiosperms. Vein density, stomatal density and epidermal cell size were linked in ferns with remarkably similar relationships to those observed in angiosperms, except that fern leaves had fewer veins per stomata. However, plasticity was limited in ferns and stomatal spacing was dependent on active stomatal differentiation as well as passive cell expansion. Thus, ferns (like angiosperms) appear to coordinate vein and stomatal density with epidermal cell expansion to some extent to maintain a constant ratio between veins and stomata in the leaf. The different general relationships between vein density and stomatal density in ferns and angiosperms suggests the groups have different optimum balances between the production of vein tissue dedicated to water supply and stomatal tissue for gas exchange. PMID:28953931

BASL and EPF2 act independently to regulate asymmetric divisions during stomatal development

PubMed Central

Hunt, Lee

2010-01-01

The initiation of stomatal development in the developing Arabidopsis epidermis is characterized by an asymmetric ‘entry’ division in which a small cell, known as a meristemoid, and a larger daughter cell is formed. The meristemoid may undergo further asymmetric divisions, regenerating a meristemoid each time, before differentiating into a guard mother cell which divides symmetrically to form a pair of guard cells surrounding a stomatal pore. Recently EPF2 and BASL have emerged as regulators of these asymmetric divisions and here we present results indicating that these two factors operate independently to control stomatal development PMID:20220310

Systems engineering aspects of a preliminary conceptual design of the space station environmental control and life support system

NASA Technical Reports Server (NTRS)

Lin, C. H.; Meyer, M. S.

1983-01-01

The systems engineering aspects of developing a conceptual design of the Space Station Environmental Control and Life Support System (ECLSS) are discussed. Topics covered include defining system requirements and groundrules for approach, formulating possible cycle closure options, and establishing a system-level mass balance on the essential materials processed in oxygen and water cycles. Consideration is also given to the performance of a system trade-off study to determine the best degree of cycle closure for the ECLSS, and the construction of a conceptual design of the ECLSS with subsystem performance specifications and candidate concepts. For the optimum balance between development costs, technological risks, and resupply penalties, a partially closed cycle ECLSS option is suggested.

Predicting photosynthesis and transpiration responses to ozone: decoupling modeled photosynthesis and stomatal conductance

NASA Astrophysics Data System (ADS)

Lombardozzi, D.; Levis, S.; Bonan, G.; Sparks, J. P.

2012-08-01

Plants exchange greenhouse gases carbon dioxide and water with the atmosphere through the processes of photosynthesis and transpiration, making them essential in climate regulation. Carbon dioxide and water exchange are typically coupled through the control of stomatal conductance, and the parameterization in many models often predict conductance based on photosynthesis values. Some environmental conditions, like exposure to high ozone (O3) concentrations, alter photosynthesis independent of stomatal conductance, so models that couple these processes cannot accurately predict both. The goals of this study were to test direct and indirect photosynthesis and stomatal conductance modifications based on O3 damage to tulip poplar (Liriodendron tulipifera) in a coupled Farquhar/Ball-Berry model. The same modifications were then tested in the Community Land Model (CLM) to determine the impacts on gross primary productivity (GPP) and transpiration at a constant O3 concentration of 100 parts per billion (ppb). Modifying the Vcmax parameter and directly modifying stomatal conductance best predicts photosynthesis and stomatal conductance responses to chronic O3 over a range of environmental conditions. On a global scale, directly modifying conductance reduces the effect of O3 on both transpiration and GPP compared to indirectly modifying conductance, particularly in the tropics. The results of this study suggest that independently modifying stomatal conductance can improve the ability of models to predict hydrologic cycling, and therefore improve future climate predictions.

The alpha-subunit of the Arabidopsis heterotrimeric G protein, GPA1, is a regulator of transpiration efficiency.

PubMed

Nilson, Sarah E; Assmann, Sarah M

2010-04-01

Land plants must balance CO2 assimilation with transpiration in order to minimize drought stress and maximize their reproductive success. The ratio of assimilation to transpiration is called transpiration efficiency (TE). TE is under genetic control, although only one specific gene, ERECTA, has been shown to regulate TE. We have found that the alpha-subunit of the heterotrimeric G protein in Arabidopsis (Arabidopsis thaliana), GPA1, is a regulator of TE. gpa1 mutants, despite having guard cells that are hyposensitive to abscisic acid-induced inhibition of stomatal opening, have increased TE under ample water and drought stress conditions and when treated with exogenous abscisic acid. Leaf-level gas-exchange analysis shows that gpa1 mutants have wild-type assimilation versus internal CO2 concentration responses but exhibit reduced stomatal conductance compared with ecotype Columbia at ambient and below-ambient internal CO2 concentrations. The increased TE and reduced whole leaf stomatal conductance of gpa1 can be primarily attributed to stomatal density, which is reduced in gpa1 mutants. GPA1 regulates stomatal density via the control of epidermal cell size and stomata formation. GPA1 promoter::beta-glucuronidase lines indicate that the GPA1 promoter is active in the stomatal cell lineage, further supporting a function for GPA1 in stomatal development in true leaves.

Probabilistic density function method for nonlinear dynamical systems driven by colored noise.

PubMed

Barajas-Solano, David A; Tartakovsky, Alexandre M

2016-05-01

We present a probability density function (PDF) method for a system of nonlinear stochastic ordinary differential equations driven by colored noise. The method provides an integrodifferential equation for the temporal evolution of the joint PDF of the system's state, which we close by means of a modified large-eddy-diffusivity (LED) closure. In contrast to the classical LED closure, the proposed closure accounts for advective transport of the PDF in the approximate temporal deconvolution of the integrodifferential equation. In addition, we introduce the generalized local linearization approximation for deriving a computable PDF equation in the form of a second-order partial differential equation. We demonstrate that the proposed closure and localization accurately describe the dynamics of the PDF in phase space for systems driven by noise with arbitrary autocorrelation time. We apply the proposed PDF method to analyze a set of Kramers equations driven by exponentially autocorrelated Gaussian colored noise to study nonlinear oscillators and the dynamics and stability of a power grid. Numerical experiments show the PDF method is accurate when the noise autocorrelation time is either much shorter or longer than the system's relaxation time, while the accuracy decreases as the ratio of the two timescales approaches unity. Similarly, the PDF method accuracy decreases with increasing standard deviation of the noise.

Spontaneous eyelid closures link vigilance fluctuation with fMRI dynamic connectivity states

PubMed Central

Wang, Chenhao; Ong, Ju Lynn; Patanaik, Amiya; Chee, Michael W. L.

2016-01-01

Fluctuations in resting-state functional connectivity occur but their behavioral significance remains unclear, largely because correlating behavioral state with dynamic functional connectivity states (DCS) engages probes that disrupt the very behavioral state we seek to observe. Observing spontaneous eyelid closures following sleep deprivation permits nonintrusive arousal monitoring. During periods of low arousal dominated by eyelid closures, sliding-window correlation analysis uncovered a DCS associated with reduced within-network functional connectivity of default mode and dorsal/ventral attention networks, as well as reduced anticorrelation between these networks. Conversely, during periods when participants’ eyelids were wide open, a second DCS was associated with less decoupling between the visual network and higher-order cognitive networks that included dorsal/ventral attention and default mode networks. In subcortical structures, eyelid closures were associated with increased connectivity between the striatum and thalamus with the ventral attention network, and greater anticorrelation with the dorsal attention network. When applied to task-based fMRI data, these two DCS predicted interindividual differences in frequency of behavioral lapsing and intraindividual temporal fluctuations in response speed. These findings with participants who underwent a night of total sleep deprivation were replicated in an independent dataset involving partially sleep-deprived participants. Fluctuations in functional connectivity thus appear to be clearly associated with changes in arousal. PMID:27512040

Robotic treatment of a type 2 calyceal diverticulum in a child: is suture closure and marsupialisation enough for a good outcome?

PubMed

Sripathi, V; Mitra, Aparajita; Padankatti, Rajiv L; Ganesan, T

2017-10-27

Calyceal diverticula in children are rare and 20% eventually become symptomatic. Following the use of laparoscopic or endoscopic treatments, 85% of children report symptomatic relief. However, complete radiological resolution is seen only in three-fourths of the laparoscopic group and a quarter of those treated via endoscopy. Diathermy ablation of the lining and/or prolonged double J stenting has not altered this outcome. The robotic approach is superior to the other two techniques as the leak can be clearly identified and securely suture ligated. We believe that this is the third published report of the successful closure of a calyceal diverticulum in a child using robotic assistance. A ten-year-old boy presented with severe pain in the right flank and a palpable renal swelling. Retrograde injection of contrast outlined a large exophytic calyceal diverticulum (type 2) in the lower pole. Robotic assistance allowed precise suture closure of the neck as well as partial marsupialisation of the diverticulum. The child was discharged within 48 h and remains symptom free 18 months later. Calyceal diverticula are rare but technically challenging entities. We have shown a good outcome with only suture closure of the leak. Diathermy ablation of the lining and prolonged internal stenting were avoided.

Hierarchy of cellular decisions in collective behavior: Implications for wound healing.

PubMed

Wickert, Lisa E; Pomerenke, Shaun; Mitchell, Isaiah; Masters, Kristyn S; Kreeger, Pamela K

2016-02-02

Collective processes such as wound re-epithelialization result from the integration of individual cellular decisions. To determine which individual cell behaviors represent the most promising targets to engineer re-epithelialization, we examined collective and individual responses of HaCaT keratinocytes seeded upon polyacrylamide gels of three stiffnesses (1, 30, and 100 kPa) and treated with a range of epidermal growth factor (EGF) doses. Wound closure was found to increase with substrate stiffness, but was responsive to EGF treatment only above a stiffness threshold. Individual cell behaviors were used to create a partial least squares regression model to predict the hierarchy of factors driving wound closure. Unexpectedly, cell area and persistence were found to have the strongest correlation to the observed differences in wound closure. Meanwhile, the model predicted a relatively weak correlation between wound closure with proliferation, and the unexpectedly minor input from proliferation was successfully tested with inhibition by aphidicolin. Combined, these results suggest that the poor clinical results for growth factor-based therapies for chronic wounds may result from a disconnect between the individual cellular behaviors targeted in these approaches and the resulting collective response. Additionally, the stiffness-dependency of EGF sensitivity suggests that therapies matched to microenvironmental characteristics will be more efficacious.

Estimating maximum mean canopy stomatal conductance for use in models

Treesearch

Brent E. Ewers; Ram Oren; Kurt H. Johnsen; J.J Landsberg

2001-01-01

Fertilized (F) and irrigated and fertilized (IF) stands of Pinus taeda L. produced twice the leaf area index of irrigated (I) and control (C) stands. Based on sap flux-scaled mean stomatal conductance (GS), we found that stomatal conductance in F was half that in other treatments. During the growing season, GS was related to...

Complete Genome Sequences of Two Vesicular Stomatitis Virus Isolates Collected in Mexico.

PubMed

Velazquez-Salinas, Lauro; Isa, Pavel; Pauszek, Steven J; Rodriguez, Luis L

2017-09-14

We report two full-genome sequences of vesicular stomatitis New Jersey virus (VSNJV) obtained by Illumina next-generation sequencing of RNA isolated from epithelial suspensions of cattle naturally infected in Mexico. These genomes represent the first full-genome sequences of vesicular stomatitis New Jersey viruses circulating in Mexico deposited in the GenBank database.

Comparison of different stomatal conductance algorithms for ozone flux modelling [Proceedings

Treesearch

P. Buker; L. D. Emberson; M. R. Ashmore; G. Gerosa; C. Jacobs; W. J. Massman; J. Muller; N. Nikolov; K. Novak; E. Oksanen; D. De La Torre; J. -P. Tuovinen

2006-01-01

The ozone deposition model (D03SE) that has been developed and applied within the EMEP photooxidant model (Emberson et al., 2000, Simpson et al. 2003) currently estimates stomatal ozone flux using a stomatal conductance (gs) model based on the multiplicative algorithm initially developed by Jarvis (1976). This model links gs to environmental and phenological parameters...

The Plasma Membrane H+-ATPase AHA1 Plays a Major Role in Stomatal Opening in Response to Blue Light1

PubMed Central

Yamauchi, Shota; Takemiya, Atsushi; Sakamoto, Tomoaki; Kurata, Tetsuya; Tsutsumi, Toshifumi

2016-01-01

Stomata open in response to a beam of weak blue light under strong red light illumination. A blue light signal is perceived by phototropins and transmitted to the plasma membrane H+-ATPase that drives stomatal opening. To identify the components in this pathway, we screened for mutants impaired in blue light-dependent stomatal opening. We analyzed one such mutant, provisionally named blus2 (blue light signaling2), and found that stomatal opening in leaves was impaired by 65%, although the magnitude of red light-induced opening was not affected. Blue light-dependent stomatal opening in the epidermis and H+ pumping in guard cell protoplasts were inhibited by 70% in blus2. Whole-genome resequencing identified a mutation in the AHA1 gene of the mutant at Gly-602. T-DNA insertion mutants of AHA1 exhibited a similar phenotype to blus2; this phenotype was complemented by the AHA1 gene. We renamed blus2 as aha1-10. T-DNA insertion mutants of AHA2 and AHA5 did not show any impairment in stomatal response, although the transcript levels of AHA2 and AHA5 were higher than those of AHA1 in wild-type guard cells. Stomata in ost2, a constitutively active AHA1 mutant, did not respond to blue light. A decreased amount of H+-ATPase in aha1-10 accounted for the reduced stomatal blue light responses and the decrease was likely caused by proteolysis of misfolded AHA1. From these results, we conclude that AHA1 plays a major role in blue light-dependent stomatal opening in Arabidopsis and that the mutation made the AHA1 protein unstable in guard cells. PMID:27261063

The Plasma Membrane H+-ATPase AHA1 Plays a Major Role in Stomatal Opening in Response to Blue Light.

PubMed

Yamauchi, Shota; Takemiya, Atsushi; Sakamoto, Tomoaki; Kurata, Tetsuya; Tsutsumi, Toshifumi; Kinoshita, Toshinori; Shimazaki, Ken-Ichiro

2016-08-01

Stomata open in response to a beam of weak blue light under strong red light illumination. A blue light signal is perceived by phototropins and transmitted to the plasma membrane H(+)-ATPase that drives stomatal opening. To identify the components in this pathway, we screened for mutants impaired in blue light-dependent stomatal opening. We analyzed one such mutant, provisionally named blus2 (blue light signaling2), and found that stomatal opening in leaves was impaired by 65%, although the magnitude of red light-induced opening was not affected. Blue light-dependent stomatal opening in the epidermis and H(+) pumping in guard cell protoplasts were inhibited by 70% in blus2 Whole-genome resequencing identified a mutation in the AHA1 gene of the mutant at Gly-602. T-DNA insertion mutants of AHA1 exhibited a similar phenotype to blus2; this phenotype was complemented by the AHA1 gene. We renamed blus2 as aha1-10 T-DNA insertion mutants of AHA2 and AHA5 did not show any impairment in stomatal response, although the transcript levels of AHA2 and AHA5 were higher than those of AHA1 in wild-type guard cells. Stomata in ost2, a constitutively active AHA1 mutant, did not respond to blue light. A decreased amount of H(+)-ATPase in aha1-10 accounted for the reduced stomatal blue light responses and the decrease was likely caused by proteolysis of misfolded AHA1. From these results, we conclude that AHA1 plays a major role in blue light-dependent stomatal opening in Arabidopsis and that the mutation made the AHA1 protein unstable in guard cells. © 2016 American Society of Plant Biologists. All Rights Reserved.

Stomatal cell wall composition: distinctive structural patterns associated with different phylogenetic groups

PubMed Central

Shtein, Ilana; Shelef, Yaniv; Marom, Ziv; Zelinger, Einat; Schwartz, Amnon; Popper, Zoë A.; Bar-On, Benny

2017-01-01

Background and Aims Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. Methods A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns (Asplenium nidus and Platycerium bifurcatum) and angiosperms (Arabidopsis thaliana and Commelina erecta) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata (Sorghum bicolor and Triticum aestivum). Key Results Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidney-shaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. Conclusions The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution. PMID:28158449

Overexpression of plasma membrane H+-ATPase in guard cells promotes light-induced stomatal opening and enhances plant growth.

PubMed

Wang, Yin; Noguchi, Ko; Ono, Natsuko; Inoue, Shin-ichiro; Terashima, Ichiro; Kinoshita, Toshinori

2014-01-07

Stomatal pores surrounded by a pair of guard cells in the plant epidermis control gas exchange between plants and the atmosphere in response to light, CO2, and the plant hormone abscisic acid. Light-induced stomatal opening is mediated by at least three key components: the blue light receptor phototropin (phot1 and phot2), plasma membrane H(+)-ATPase, and plasma membrane inward-rectifying K(+) channels. Very few attempts have been made to enhance stomatal opening with the goal of increasing photosynthesis and plant growth, even though stomatal resistance is thought to be the major limiting factor for CO2 uptake by plants. Here, we show that transgenic Arabidopsis plants overexpressing H(+)-ATPase using the strong guard cell promoter GC1 showed enhanced light-induced stomatal opening, photosynthesis, and plant growth. The transgenic plants produced larger and increased numbers of rosette leaves, with ∼42-63% greater fresh and dry weights than the wild type in the first 25 d of growth. The dry weights of total flowering stems of 45-d-old transgenic plants, including seeds, siliques, and flowers, were ∼36-41% greater than those of the wild type. In addition, stomata in the transgenic plants closed normally in response to darkness and abscisic acid. In contrast, the overexpression of phototropin or inward-rectifying K(+) channels in guard cells had no effect on these phenotypes. These results demonstrate that stomatal aperture is a limiting factor in photosynthesis and plant growth, and that manipulation of stomatal opening by overexpressing H(+)-ATPase in guard cells is useful for the promotion of plant growth.

Solar-induced chlorophyll fluorescence tracks the trend of canopy stomatal conductance and transpiration at diurnal and seasonal scales

NASA Astrophysics Data System (ADS)

Zhang, Y.; Shan, N.; Ju, W.; Chen, J.

2017-12-01

Transpiration is the process of plant water loss through the stomata on the leaf surface and plays a key role in the energy and water balance of the land surface. Plant stomata function as a control interface for regulating photosynthetic uptake of CO2 and transpiration, strongly linked to plant productivity. Stomatal conductance is fundamental to larger-scale regional prediction of carbon-water cycles and their feedbacks to climate. The widely used Ball-Berry model coupled photosynthesis to a semi-empirical model of stomatal conductance. However large uncertainties remain in simulation of carbon assimilation rate in ecosystem and regional scales. The strong correlations of solar-induced fluorescence (SIF) and GPP have been demonstrated and provides an important opportunity to accurately monitor photosynthetic activity and water exchange. In this presentation, we compared both canopy-observed SIF and satellite-derived SIF with tower-based canopy stomatal conductance from hourly to 8-day scales in forest and cropland ecosystem. Using the model of stomatal conductance based on SIF, the transpiration was estimated at hourly and daily scales and compared with flux tower measurements. The results showed that the seasonal pattern of canopy stomatal conductance agreed better with SIF compared to NDVI and their relationship was higher during sunny days for forest ecosystem. Canopy stomatal conductance correlated with both tower-observed SIF and SIF from the Global Ozone Monitoring Experiment-2. Estimation of transpiration from SIF performed well in both forest and cropland ecosystem. This remotely sensed approaches from SIF for modelling stomatal conductance opens a new era to analysis and simulation of coupled carbon and water cycles under climate change.

Stomatal vs. genome size in angiosperms: the somatic tail wagging the genomic dog?

PubMed Central

Hodgson, J. G.; Sharafi, M.; Jalili, A.; Díaz, S.; Montserrat-Martí, G.; Palmer, C.; Cerabolini, B.; Pierce, S.; Hamzehee, B.; Asri, Y.; Jamzad, Z.; Wilson, P.; Raven, J. A.; Band, S. R.; Basconcelo, S.; Bogard, A.; Carter, G.; Charles, M.; Castro-Díez, P.; Cornelissen, J. H. C.; Funes, G.; Jones, G.; Khoshnevis, M.; Pérez-Harguindeguy, N.; Pérez-Rontomé, M. C.; Shirvany, F. A.; Vendramini, F.; Yazdani, S.; Abbas-Azimi, R.; Boustani, S.; Dehghan, M.; Guerrero-Campo, J.; Hynd, A.; Kowsary, E.; Kazemi-Saeed, F.; Siavash, B.; Villar-Salvador, P.; Craigie, R.; Naqinezhad, A.; Romo-Díez, A.; de Torres Espuny, L.; Simmons, E.

2010-01-01

Background and Aims Genome size is a function, and the product, of cell volume. As such it is contingent on ecological circumstance. The nature of ‘this ecological circumstance’ is, however, hotly debated. Here, we investigate for angiosperms whether stomatal size may be this ‘missing link’: the primary determinant of genome size. Stomata are crucial for photosynthesis and their size affects functional efficiency. Methods Stomatal and leaf characteristics were measured for 1442 species from Argentina, Iran, Spain and the UK and, using PCA, some emergent ecological and taxonomic patterns identified. Subsequently, an assessment of the relationship between genome-size values obtained from the Plant DNA C-values database and measurements of stomatal size was carried out. Key Results Stomatal size is an ecologically important attribute. It varies with life-history (woody species < herbaceous species < vernal geophytes) and contributes to ecologically and physiologically important axes of leaf specialization. Moreover, it is positively correlated with genome size across a wide range of major taxa. Conclusions Stomatal size predicts genome size within angiosperms. Correlation is not, however, proof of causality and here our interpretation is hampered by unexpected deficiencies in the scientific literature. Firstly, there are discrepancies between our own observations and established ideas about the ecological significance of stomatal size; very large stomata, theoretically facilitating photosynthesis in deep shade, were, in this study (and in other studies), primarily associated with vernal geophytes of unshaded habitats. Secondly, the lower size limit at which stomata can function efficiently, and the ecological circumstances under which these minute stomata might occur, have not been satisfactorally resolved. Thus, our hypothesis, that the optimization of stomatal size for functional efficiency is a major ecological determinant of genome size, remains unproven. PMID:20375204

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

NASA Astrophysics Data System (ADS)

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

2013-04-01

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

Stomatal movements in laurophyllous plants

NASA Astrophysics Data System (ADS)

Pautov, A. A.; Bauer, S. M.; Ivanova, O. V.; Sapach, Y. O.; Krylova, E. G.

2018-05-01

Stomata are the structural elements of plant epidermis which control transpiration and gas exchange. Each stoma consists of two guard cells divided by the stomatal aperture. These cells are capable of reversible deformations determining the width of aperture. It is known that these deformations depend on the value of turgor pressure in the guard cells and on the structure of their walls. In this work, the influence of the outer tangential wall geometry of the guard cells on stomatal movements is estimated by means of the finite element method in the ANSYS software. The application of modelling has shown that cuticular outgrowths on the tangential walls influence the degree and pattern of guard cell deformations. The outgrowths prevent wide opening of the stomatal aperture and cause its sinking deep into leaf epidermis. The functional significance of such stomatal movements is discussed. It is deduced that the discovered phenomenon had great importance to the survival of laurophyllous plants in conditions of aridization.

Stomatal innovation and the rise of seed plants.

PubMed

McAdam, Scott A M; Brodribb, Timothy J

2012-01-01

Stomatal valves on the leaves of vascular plants not only prevent desiccation but also dynamically regulate water loss to maintain efficient daytime water use. This latter process involves sophisticated active control of stomatal aperture that may be absent from early-branching plant clades. To test this hypothesis, we compare the stomatal response to light intensity in 13 species of ferns and lycophytes with a diverse sample of seed plants to determine whether the capacity to optimise water use is an ancestral or derived feature of stomatal physiology. We found that in seed plants, the ratio of photosynthesis to water use remained high and constant at different light intensities, but fern and lycophyte stomata were incapable of sustaining homeostatic water use efficiency. We conclude that efficient water use in early seed plants provided them with a competitive advantage that contributed to the decline of fern and lycophyte dominated-ecosystems in the late Paleozoic. © 2011 Blackwell Publishing Ltd/CNRS.

Developmental priming of stomatal sensitivity to abscisic acid by leaf microclimate.

PubMed

Pantin, Florent; Renaud, Jeanne; Barbier, François; Vavasseur, Alain; Le Thiec, Didier; Rose, Christophe; Bariac, Thierry; Casson, Stuart; McLachlan, Deirdre H; Hetherington, Alistair M; Muller, Bertrand; Simonneau, Thierry

2013-09-23

Plant water loss and CO2 uptake are controlled by valve-like structures on the leaf surface known as stomata. Stomatal aperture is regulated by hormonal and environmental signals. We show here that stomatal sensitivity to the drought hormone abscisic acid (ABA) is acquired during leaf development by exposure to an increasingly dryer atmosphere in the rosette plant Arabidopsis. Young leaves, which develop in the center of the rosette, do not close in response to ABA. As the leaves increase in size, they are naturally exposed to increasingly dry air as a consequence of the spatial arrangement of the leaves, and this triggers the acquisition of ABA sensitivity. Interestingly, stomatal ABA sensitivity in young leaves is rapidly restored upon water stress. These findings shed new light on how plant architecture and stomatal physiology have coevolved to optimize carbon gain against water loss in stressing environments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Infection of guinea pigs with vesicular stomatitis New Jersey virus Transmitted by Culicoides sonorensis (Diptera: Ceratopogonidae).

PubMed

Pérez De León, Adalberto A; O'Toole, Donal; Tabachnick, Walter J

2006-05-01

Intrathoracically inoculated Culicoides sonorensis Wirth & Jones were capable of transmitting vesicular stomatitis New Jersey virus (family Rhabdoviridae, genus Vesiculovirus, VSNJV) during blood feeding on the abdomen of six guinea pigs. None of the guinea pigs infected in this manner developed clinical signs of vesicular stomatitis despite seroconversion for VSNJV. Guinea pigs infected by intradermal inoculations of VSNJV in the abdomen also failed to develop clinical signs of vesicular stomatitis. Three guinea pigs given intradermal inoculations of VSNJV in the foot pad developed lesions typical of vesicular stomatitis. Transmission by the bite of C. sonorensis may have facilitated guinea pig infection with VSNJV because a single infected C. sonorensis caused seroconversion and all guinea pigs infected by insect bite seroconverted compared with 50% of the guinea pigs infected by intradermal inoculation with a higher titer VSNJV inoculum. The role of C. sonorensis in the transmission of VSNJV is discussed.

Understanding the school community's response to school closures during the H1N1 2009 influenza pandemic.

PubMed

Braunack-Mayer, Annette; Tooher, Rebecca; Collins, Joanne E; Street, Jackie M; Marshall, Helen

2013-04-15

During the 2009 H1N1 influenza pandemic, Australian public health officials closed schools as a strategy to mitigate the spread of the infection. This article examines school communities' understanding of, and participation in, school closures and the beliefs and values which underpinned school responses to the closures. We interviewed four school principals, 25 staff, 14 parents and 13 students in five schools in one Australian city which were either fully or partially closed during the 2009 H1N1 pandemic. Drawing on Thompson et al's ethical framework for pandemic planning, we show that considerable variation existed between and within schools in their attention to ethical processes and values. In all schools, health officials and school leaders were strongly committed to providing high quality care for members of the school community. There was variation in the extent to which information was shared openly and transparently, the degree to which school community members considered themselves participants in decision-making, and the responsiveness of decision-makers to the changing situation. Reservations were expressed about the need for closures and quarantine and there was a lack of understanding of the rationale for the closures. All schools displayed a strong duty of care toward those in need, although school communities had a broader view of care than that of the public health officials. Similarly, there was a clear understanding of and commitment to protect the public from harm and to demonstrate responsible stewardship. We conclude that school closures during an influenza pandemic represent both a challenge for public health officials and a litmus test for the level of trust in public officials, government and the school as institution. In our study, trust was the foundation upon which effective responses to the school closure were built. Trust relations within the school were the basis on which different values and beliefs were used to develop and justify the practices and strategies in response to the pandemic.