The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Tracy Lawson - One of the best experts on this subject based on the ideXlab platform.
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Mesophyll photosynthesis and guard cell metabolism impacts on stomatal behaviour
New Phytologist, 2014Co-Authors: Tracy Lawson, Andrew J Simkin, Gilor Kelly, David GranotAbstract:Contents 'Summary' 1064 I. 'Introduction' 1064 II. 'Coordination between Mesophyll and stomata' 1066 III. 'The Mesophyll signal' 1066 IV. 'Arguments against a Mesophyll-driven signal other than Ci' 1068 V. 'Guard cell osmoregulation and evidence for a role of sucrose' 1069 VI. 'Degradation of starch' 1070 VII. 'Guard cell photosynthetic production of Suc' 1070 VIII. 'Guard cell Suc imported from the Mesophyll' 1070 IX. 'Sugar sensing and metabolism' 1071 X. 'The importance of malate as a Mesophyll-driven signal' 1072 XI. 'Role of aquaporins' 1074 XII. 'Guard cell manipulation and possible future directions' 1074 'Acknowledgements' 1076 References 1076 Summary Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere. Guard cells determine stomatal aperture and must operate to ensure an appropriate balance between CO2 uptake for photosynthesis (A) and water loss, and ultimately plant water use efficiency (WUE). A strong correlation between A and stomatal conductance (gs) is well documented and often observed, but the underlying mechanisms, possible signals and metabolites that promote this relationship are currently unknown. In this review we evaluate the current literature on Mesophyll-driven signals that may coordinate stomatal behaviour with Mesophyll carbon assimilation. We explore a possible role of various metabolites including sucrose and malate (from several potential sources; including guard cell photosynthesis) and new evidence that improvements in WUE have been made by manipulating sucrose metabolism within the guard cells. Finally we discuss the new tools and techniques available for potentially manipulating cell-specific metabolism, including guard and Mesophyll cells, in order to elucidate Mesophyll-derived signals that coordinate Mesophyll CO2 demands with stomatal behaviour, in order to provide a mechanistic understanding of these processes as this may identify potential targets for manipulations in order to improve plant WUE and crop yield.
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Mesophyll photosynthesis and guard cell metabolism impacts on stomatal behaviour
New Phytologist, 2014Co-Authors: Tracy Lawson, Andrew J Simkin, Gilor Kelly, David GranotAbstract:Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere. Guard cells determine stomatal aperture and must operate to ensure an appropriate balance between CO2 uptake for photosynthesis (A) and water loss, and ultimately plant water use efficiency (WUE). A strong correlation between A and stomatal conductance (gs ) is well documented and often observed, but the underlying mechanisms, possible signals and metabolites that promote this relationship are currently unknown. In this review we evaluate the current literature on Mesophyll-driven signals that may coordinate stomatal behaviour with Mesophyll carbon assimilation. We explore a possible role of various metabolites including sucrose and malate (from several potential sources; including guard cell photosynthesis) and new evidence that improvements in WUE have been made by manipulating sucrose metabolism within the guard cells. Finally we discuss the new tools and techniques available for potentially manipulating cell-specific metabolism, including guard and Mesophyll cells, in order to elucidate Mesophyll-derived signals that coordinate Mesophyll CO2 demands with stomatal behaviour, in order to provide a mechanistic understanding of these processes as this may identify potential targets for manipulations in order to improve plant WUE and crop yield.
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the responses of guard and Mesophyll cell photosynthesis to co2 o2 light and water stress in a range of species are similar
Journal of Experimental Botany, 2003Co-Authors: Tracy Lawson, Kevin Oxborough, James I L Morison, Neil R BakerAbstract:High resolution chlorophyll a fluorescence imaging was used to compare the photosynthetic efficiency of PSII electron transport (estimated by Fq¢/Fm¢) in guard cell chloroplasts and the underlying Mesophyll in intact leaves of six different species: Commelina communis, Vicia faba, Amaranthus caudatus, Polypodium vulgare, Nicotiana tabacum, and Tradescantia albifora. While photosynthetic efficiency varied between the species, the efficiencies of guard cells and Mesophyll cells were always closely matched. As measurement light intensity was increased, guard cells from the lower leaf surfaces of C. communis and V. faba showed larger reductions in photosynthetic efficiency than those from the upper surfaces. In these two species, guard cell photosynthetic efficiency responded similarly to that of the Mesophyll when either light intensity or CO2 concentration during either measurement or growth was changed. In all six species, reducing the O2 concentration from 21% to 2% reduced guard cell photosynthetic efficiency, even for the C4 species A. caudatus, although the Mesophyll of the C4 species did not show any O2 modulation of photosynthetic efficiency. This suggests that Rubisco activity is significant in the guard cells of these six species. When C. communis plants were water-stressed, the guard cell photosynthetic efficiency declined in parallel with that of the Mesophyll. It was concluded that the photosynthetic efficiency in guard cells is determined by the same factors that determine it in the Mesophyll.
David Granot - One of the best experts on this subject based on the ideXlab platform.
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Mesophyll photosynthesis and guard cell metabolism impacts on stomatal behaviour
New Phytologist, 2014Co-Authors: Tracy Lawson, Andrew J Simkin, Gilor Kelly, David GranotAbstract:Contents 'Summary' 1064 I. 'Introduction' 1064 II. 'Coordination between Mesophyll and stomata' 1066 III. 'The Mesophyll signal' 1066 IV. 'Arguments against a Mesophyll-driven signal other than Ci' 1068 V. 'Guard cell osmoregulation and evidence for a role of sucrose' 1069 VI. 'Degradation of starch' 1070 VII. 'Guard cell photosynthetic production of Suc' 1070 VIII. 'Guard cell Suc imported from the Mesophyll' 1070 IX. 'Sugar sensing and metabolism' 1071 X. 'The importance of malate as a Mesophyll-driven signal' 1072 XI. 'Role of aquaporins' 1074 XII. 'Guard cell manipulation and possible future directions' 1074 'Acknowledgements' 1076 References 1076 Summary Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere. Guard cells determine stomatal aperture and must operate to ensure an appropriate balance between CO2 uptake for photosynthesis (A) and water loss, and ultimately plant water use efficiency (WUE). A strong correlation between A and stomatal conductance (gs) is well documented and often observed, but the underlying mechanisms, possible signals and metabolites that promote this relationship are currently unknown. In this review we evaluate the current literature on Mesophyll-driven signals that may coordinate stomatal behaviour with Mesophyll carbon assimilation. We explore a possible role of various metabolites including sucrose and malate (from several potential sources; including guard cell photosynthesis) and new evidence that improvements in WUE have been made by manipulating sucrose metabolism within the guard cells. Finally we discuss the new tools and techniques available for potentially manipulating cell-specific metabolism, including guard and Mesophyll cells, in order to elucidate Mesophyll-derived signals that coordinate Mesophyll CO2 demands with stomatal behaviour, in order to provide a mechanistic understanding of these processes as this may identify potential targets for manipulations in order to improve plant WUE and crop yield.
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Mesophyll photosynthesis and guard cell metabolism impacts on stomatal behaviour
New Phytologist, 2014Co-Authors: Tracy Lawson, Andrew J Simkin, Gilor Kelly, David GranotAbstract:Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere. Guard cells determine stomatal aperture and must operate to ensure an appropriate balance between CO2 uptake for photosynthesis (A) and water loss, and ultimately plant water use efficiency (WUE). A strong correlation between A and stomatal conductance (gs ) is well documented and often observed, but the underlying mechanisms, possible signals and metabolites that promote this relationship are currently unknown. In this review we evaluate the current literature on Mesophyll-driven signals that may coordinate stomatal behaviour with Mesophyll carbon assimilation. We explore a possible role of various metabolites including sucrose and malate (from several potential sources; including guard cell photosynthesis) and new evidence that improvements in WUE have been made by manipulating sucrose metabolism within the guard cells. Finally we discuss the new tools and techniques available for potentially manipulating cell-specific metabolism, including guard and Mesophyll cells, in order to elucidate Mesophyll-derived signals that coordinate Mesophyll CO2 demands with stomatal behaviour, in order to provide a mechanistic understanding of these processes as this may identify potential targets for manipulations in order to improve plant WUE and crop yield.
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The Role of Plasma Membrane Aquaporins in Regulating the Bundle Sheath-Mesophyll
2014Co-Authors: Nir Sade, Gilor Kelly, David Granot, Arava Shatil-cohen, Ziv Attia, Christophe Maurel, Yann Boursiac, Adi Yaaran, Stephen Lerner, Menachem MoshelionAbstract:Our understanding of the cellular role of aquaporins (AQPs) in the regulation of whole-plant hydraulics, in general, and extravascular, radial hydraulic conductance in leaves (K leaf ), in particular, is still fairly limited. We hypothesized that the AQPs of the vascular bundle sheath (BS) cells regulate K leaf . To examine this hypothesis, AQP genes were silenced using artificial microRNAs that were expressed constitutively or specifically targeted to the BS. MicroRNA sequences were designed to target all five AQP genes from the PLASMA MEMBRANE-INTRINSIC PROTEIN1 (PIP1) subfamily. Our results show that the constitutively silenced PIP1 (35S promoter) plants had decreased PIP1 transcript and protein levels and decreased Mesophyll and BS osmotic water permeability (Pf), Mesophyll conductance of CO2, photosynthesis, Kleaf, transpiration, and shoot biomass. Plants in which the PIP1 subfamily was silenced only in the BS (SCARECROW:microRNA plants) exhibited decreased Mesophyll and BS Pf and decreased Kleaf but no decreases in the rest of the parameters listed above, with the net result of increased shoot biomass. We excluded the possibility of SCARECROW promoter activity in the Mesophyll. Hence, the fact that SCARECROW:microRNA Mesophyll exhibited reduced Pf, but not reduced Mesophyll conductance of CO2, suggests that the BS-Mesophyll hydraulic continuum acts as a feed-forward control signal. The role of AQPs in the hierarchy of the hydraulic signal pathway controlling leaf water status under normal and limited-water conditions is discussed.
Ichiro Terashima - One of the best experts on this subject based on the ideXlab platform.
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Confirmation of Mesophyll signals controlling stomatal responses by a newly devised transplanting method.
Functional Plant Biology, 2019Co-Authors: Takashi Fujita, Ko Noguchi, Hiroshi Ozaki, Ichiro TerashimaAbstract:There are opposing views on whether the responses of stomata to environmental stimuli are all autonomous reactions of stomatal guard cells or whether Mesophyll is involved in these responses. Transplanting isolated epidermis onto Mesophyll is a potent methodology for examining the roles of Mesophyll-derived signals in stomatal responses. Here we report on development of a new transplanting method. Leaf segments of Commelina communis L. were pretreated in the light or dark at 10, 39 or 70 Pa ambient CO2 for 1 h. Then the abaxial epidermises were removed and the epidermal strips prepared from the other leaves kept in the dark at 39 Pa CO2, were transplanted onto the Mesophyll. After illumination of the transplants for 1 h at 39 Pa CO2, stomatal apertures were measured. We also examined the molecular sizes of the Mesophyll signals by inserting the dialysis membrane permeable to molecules smaller than 100–500 Da or 500–1000 Da between the epidermis and Mesophyll. Mesophyll pretreatments in the light at low CO2 partial pressures accelerated stomatal opening in the transplanted epidermal strips, whereas pretreatments at 70 Pa CO2 suppressed stomatal opening. Insertion of these dialysis membranes did not suppress stomatal opening significantly at 10 Pa CO2 in the light, whereas insertion of the 100–500 Da membrane decelerated stomatal closure at high CO2. It is probable that the Mesophyll signals inducing stomatal opening at low CO2 in the light would permeate both membranes, and that those inducing stomatal closure at high CO2 would not permeate the 100–500 Da membrane. Possible signal compounds are discussed.
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apoplastic Mesophyll signals induce rapid stomatal responses to co2 in commelina communis
New Phytologist, 2013Co-Authors: Takashi Fujita, Ko Noguchi, Ichiro TerashimaAbstract:Summary Previous studies have suggested that the Mesophyll contributes to stomatal CO2 responses. The effects of changes in CO2 concentration (100 or 700 ppm) on stomatal responses in red or white light were examined microscopically in a leaf segment, an epidermal strip and an epidermal strip placed on a Mesophyll segment of Commelina communis, all mounted on a buffer-containing gel. In both red and white light, stomata of the leaf segment opened/closed rapidly at low/high CO2. In red light, epidermal strip stomata barely responded to CO2. In white light, they opened at low CO2, but hardly closed at high CO2. Stomata of the epidermal strip placed on the Mesophyll responded in the same manner as those on the leaf segment. Insertion of a doughnut-shaped cellophane spacer (but not polyethylene spacer) between the epidermal strip and the Mesophyll hardly altered these responses. Stomata in leaf segments treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), a photosynthesis inhibitor, did not open in red light, but opened/closed at low/high CO2 in white light. These results indicate that the apoplast transfer of ‘Mesophyll signals’ and the stomatal opening at low CO2 are dependent on photosynthesis, whereas the stomatal closure at high CO2 is independent of photosynthesis.
V. I. P'yankov - One of the best experts on this subject based on the ideXlab platform.
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Shading-induced changes in the leaf Mesophyll of plants of different functional types
Russian Journal of Plant Physiology, 2008Co-Authors: L. A. Ivanova, L. A. Ivanov, D. A. Ronzhina, V. I. P'yankovAbstract:Changes in the structural characteristics of Mesophyll induced by shading were investigated in ten species of wild plants of diverse functional types. In all plant types, shading reduced leaf thickness and density by 30–50% and total surface of Mesophyll, by 30–70%. The extent and mechanisms of Mesophyll structural rearrangement depended on the plant functional type. In the ruderal plants, integral parameters of Mesophyll, such as the surface of cells and chloroplasts and Mesophyll resistance, changed threefold predominantly because of changes in the dimensions of the cells and chloroplasts. In these plants, shading reduced the volume of chloroplasts by 30%, and the chloroplast numbers per cell declined. The competitor plants showed a twofold increase in Mesophyll resistance due to a decrease in the number of photosynthesizing cells per leaf area unit. Moreover, these plants maintained constant dimensions of Mesophyll cells, ratios Mesophyll surface/Mesophyll volume and chloroplast surface/cell surface. In stress-tolerant plants, diffusion resistance of Mesophyll remained the same irrespective of the growing conditions, and Mesophyll rearrangement was associated with inversely proportional changes in the dimensions of the cells and cell volume per chloroplast. Noteworthy of these plants were relatively constant chloroplasts number per cell, per leaf area unit and total surface area of chloroplasts. The nature of relationship between the Mesophyll diffusion resistance and structural parameters of leaf Mesophyll differed in plants of diverse functional types.
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A Method for Calculating the Volume and Surface Area in Rice Mesophyll Cells
Russian Journal of Plant Physiology, 2003Co-Authors: O. L. Burundukova, Yu. N. Zhuravlev, N. V. Solopov, V. I. P'yankovAbstract:A method was developed for determining the surface area and volume of rice Mesophyll cells of elaborate configuration. The method was employed to calculate these indices in several types of rice Mesophyll cells found in seventy samples (53 species) of diverse origin coming from Japan, China, Korea, India, Nepal, Australia, France, Italy, Uzbekistan, Afghanistan, and Krasnodar and Primorskii regions. The cultivars of diverse geographic origin varied in cell shape and size due to the number, size, and arrangement of chloroplasts. When the volumes and surface areas of leaf Mesophyll cells were compared using the method reported herein and a simple empirical model of the cell as a single ellipsoid, the two methods produced relatively similar data for cell volume; however, the surface area calculated by the former method was about two times larger than in the latter case. The method described in this paper allows for accurate calculations of the volume and surface area of rice Mesophyll cells when data are available on the cell shape and linear dimensions and the number of chloroplasts per cell.
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Structural Adaptation of the Leaf Mesophyll to Shading
Russian Journal of Plant Physiology, 2002Co-Authors: L. A. Ivanova, V. I. P'yankovAbstract:Structural characteristics of the Mesophyll were studied in five boreal grass species experiencing a wide range of light and water supply conditions. Quantitative indices of the palisade and spongy Mesophyll tissues (cell and chloroplast sizes, the number of chloroplasts per cell, the total cell and chloroplast surface area per unit leaf surface area) were determined in leaves of each of the species. The cell surface area and the cell volume in spongy Mesophyll were determined with a novel method based on stereological analysis of cell projections. An important role of spongy parenchyma in the photosynthetic apparatus was demonstrated. In leaves of the species studied, the spongy parenchyma constituted about 50% of the total volume and 40% of the total surface area of Mesophyll cells. The proportion of the palisade to spongy Mesophyll tissues varied with plant species and growth conditions. In a xerophyte Genista tinctoria, the total cell volume, cell abundance, and the total surface area of cells and chloroplasts were 30–40% larger in the palisade than in the spongy Mesophyll. In contrast, in a shade-loving species Veronica chamaedris, the spongy Mesophyll was 1.5–2 times more developed than the palisade Mesophyll. In mesophyte species grown under high light conditions, the cell abundance and the total cell surface area were 10–20% greater in the palisade Mesophyll than in the spongy parenchyma. In shaded habitats, these indices were similar in the palisade and spongy Mesophyll or were 10–20% lower in the palisade Mesophyll. In mesophytes, CO2 conductance of the spongy Mesophyll accounted for about 50% of the total Mesophyll conductance, as calculated from the structural characteristics, with the Mesophyll CO2 conductance increasing with leaf shading.
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Structure of the Photosynthetic Apparatus in Leaves of Freshwater Hydrophytes: 2. Quantitative Characterization of Leaf Mesophyll and the Functional Activity of Leaves with Different Degrees of Submersion
Russian Journal of Plant Physiology, 2001Co-Authors: D. A. Ronzhina, V. I. P'yankovAbstract:The structure of leaf photosynthetic elements was investigated on 42 boreal plant species characterized by different degrees of submergence (helophytes, neustophytes, and hydatophytes). Six main types of Mesophyll structures were identified. Quantitative characteristics for the mesostructure of the photosynthetic apparatus in these groups were determined, such as the size and abundance of cells and chloroplasts in the Mesophyll and epidermis, the number of plastids per cell in each tissue, the total surface area of the Mesophyll cells, epidermal cells, and chloroplasts per unit leaf area. Analysis showed that quantitative characteristics of the photosynthetic apparatus in hydrophytes are determined by two factors: (a) the degree of leaf submergence and (b) the type of Mesophyll structure. With an increasing degree of immersion in water, the Mesophyll types change in a sequence isopalisade → dorsoventral → homogeneous. The leaves become thinner, their weight per unit area diminishes, cells and chloroplasts become less numerous (on a per unit leaf area basis), but their dimensions become larger. Adaptation to aquatic medium is also manifested in the increasing contribution of the epidermal tissue to the overall photosynthesis: in submerged leaves, the epidermis accounts for more than 50% of the photosynthetic activity. The occurrence of six structural types of leaves contrasting in their characteristics was confirmed by discriminatory analysis according to the qualitative parameters of Mesophyll.
Timothy J Brodribb - One of the best experts on this subject based on the ideXlab platform.
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Mesophyll cells are the main site of abscisic acid biosynthesis in water stressed leaves
Plant Physiology, 2018Co-Authors: Scott A M Mcadam, Timothy J BrodribbAbstract:The hormone abscisic acid (ABA) plays a critical role in enhancing plant survival during water deficit. Recent molecular evidence suggests that ABA is synthesized in the phloem companion cells and guard cells. However, the nature of cell turgor and water status in these two cell types cannot easily account for the rapid, water status-triggered ABA biosynthesis observed in leaves. Here, we utilize the unique foliar anatomies of an angiosperm (Hakea lissosperma) and four conifer species (Saxegothaea conspicua, Podocarpus latifolius, Cephalotaxus harringtonii, and Amentotaxus formosana) in which the Mesophyll can be isolated from the vascular tissue to identify the main site of ABA biosynthesis in water-stressed leaves. In all five species tested, considerable ABA biosynthesis occurred in Mesophyll tissue that had been separated from vascular tissue. In addition, the removal of the epidermis from the Mesophyll in two conifer species had no impact on the observed increase in ABA levels under water deficit. Our results suggest that Mesophyll cells are the predominant location of water deficit-triggered ABA biosynthesis in the leaf.
