scholarly journals Spatial photosynthesis modelling sets guidelines to constructing a viable single-cell cytoplasm-to-stroma C4 cycle

2018 ◽  
Author(s):  
Ivan Jurić ◽  
Julian M. Hibberd ◽  
Mike Blatt ◽  
Nigel J. Burroughs
Keyword(s):  
Spatial Model ◽  
Photosynthetic Efficiency ◽  
Surface Coverage ◽  
Carbon Assimilation ◽  
Mesophyll Cell ◽  
Chloroplast Envelope ◽  
Cell Geometry ◽  
Cell Cytoplasm ◽  
Mesophyll Cells ◽  
Chloroplast Stroma

AbstractIt has been proposed that introducing C4 photosynthesis into C3 crops would increase yield. The simplest scheme in- volves concentrating carbon originating from the cytosol in the chloroplast stroma of mesophyll cells without altering leaf or cell anatomy. Photosynthetic efficiency would then strongly depend on the chloroplast envelope permeability to CO2. We examine the performance of this C4 cycle with a spatial model of carbon assimilation in C3 mesophyll cell geometry, conducting a thorough exploration of parameter space relevant to C4 photosynthesis. For envelope perme- abilities below 300 µm/s C4 photosynthesis has a higher quantum efficiency than C3. However, even when envelope permeability is above this threshold, the C4 pathway can provide a substantial boost to carbon assimilation with only a moderate decrease in efficiency. Depending on the available light-harvesting capacity of plastids, C4 photosynthesis could boost carbon assimilation anywhere from 20% to 100%. Gains are even more prominent under CO2 deprivation, and can be achieved in conjunction with lower investment in plastids if chloroplast surface coverage is also altered. A C4 pathway operating within individual mesophyll cells of C3 plants could hence lead to higher growth rates and better drought resistance in dry, high-sunlight climates.

Subcellular Compartmentation of Indole-3-acetic Acid in Mesophyll Cells of Spinacia oleracea

1981 ◽  
Vol 36 (7-8) ◽  
pp. 679-685 ◽  
Author(s):  
B. Heilmann ◽  
W. Hartung ◽  
H. Gimmler
Keyword(s):  
Acetic Acid ◽  
Plant Hormone ◽  
Spinacia Oleracea ◽  
Surrounding Medium ◽  
Compartmental Analysis ◽  
Chloroplast Envelope ◽  
Mesophyll Cells ◽  
Subcellular Compartmentation ◽  
Chloroplast Stroma ◽  
Indole 3 Acetic Acid

Abstract A compartmental analysis of the distribution of the plant hormone indole-3-acetic acid (IAA) was performed with mesophyll cells of spinach leaves. The results indicated that up to about 45% of the total amount of free IAA in the laminae of spinach is localized within the chloroplasts, although these organelles occupy only about 7% of the tissue volume. This distribution is due to the dissociation properties of IAA which has a pK a of 4,7. The chloroplast envelope is easily permeable for the undissociated acid (IAAH) and less permeable for the anion (IAA"). The rate of uptake of LAA by chloroplasts was linearly dependent on the IAAH concentration gradient between medium and stroma. Uptake was increased by lowering the extraplastidic pH or by alkalization of the stroma during illumination. In illuminated chloroplasts, IAA was accumulated up to 4 fold compared to the surrounding medium owing to the pH gradient between the medium (pH 7.6) and the stroma (pH 8.0). The unexpectedly high plastidic IAA concentration observed in the dark (concentration ratio stroma/medium was about 2) suggested binding of IAA to chloroplast components. Due to this binding, the IAA distribution between medium and chloroplasts must not be used for calculating the stroma pH, as is possible with ABA. However, from the different distribution of IAA in light and darkness the light-induced alkalization of the chloroplast stroma can be calculated.

scholarly journals Photosynthetic efficiency and production of cowpea cultivars under deficit irrigation

2018 ◽  
Vol 13 (5) ◽  
pp. 1 ◽  
Author(s):  
Alberto Soares de Melo ◽  
Allisson Rafael Ferreira da Silva ◽  
Alexson Filgueiras Dutra ◽  
Wellison Filgueiras Dutra ◽  
Marcos Eric Barbosa Brito ◽  
...  
Keyword(s):  
Water Deficit ◽  
Deficit Irrigation ◽  
Photosynthetic Efficiency ◽  
Arid Regions ◽  
Carbon Fixation ◽  
Management Strategies ◽  
Carbon Assimilation ◽  
Green Beans ◽  
Gas Exchanges ◽  
Cowpea Cultivars

Cowpea is a crop with great economic, social and food importance in semi-arid regions, but its production is drastically reduced by the water deficit in these regions, requiring better management strategies that allow the crop’s production. This study therefore aimed to evaluate the photosynthetic efficiency and production of cowpea cultivars under deficit irrigation replacement levels. The experiment tested three cowpea genotypes (G1 = ‘BRS Aracé’, G2 = ‘BR 17 Gurguéia’ and G3 = ‘BRS Marataoã’) and four irrigation depths (40, 60, 80 and 100% of ETc), resulting in a 3 x 4 factorial scheme, arranged in randomized complete blocks design with four replicates. During the experiment, the gas exchanges, chlorophyll a fluorescence and production of the cowpea genotypes under deficit irrigation were evaluated. Carbon fixation in the photosynthetic metabolism of cowpea plants was reduced by accentuated water deficit, regardless of the genotype. The low stress severity was indicated by the lack of effects on chlorophyll fluorescence, indicating that the reduction in the rate of carbon assimilation was due to the stomatal effects. The irrigation with 80% of ETc can be used in the cultivation of the respective cultivars, but with small losses in the production. Among the genotypes, ‘BRS Marataoã’ stands out with respect to yield, with higher values for weight of pods and green beans.

Nitrate metabolism in relation to the aspartate-type C-4 pathway of photosynthesis in Eleusine coracana

1974 ◽  
Vol 52 (12) ◽  
pp. 2599-2605 ◽  
Author(s):  
C. K. M. Rathnam ◽  
V. S. R. Das
Keyword(s):  
Glutamate Dehydrogenase ◽  
Eleusine Coracana ◽  
Bundle Sheath ◽  
Chloroplast Envelope ◽  
Mesophyll Cells ◽  
Bundle Sheath Cells ◽  
Nitrate Metabolism ◽  
Type C ◽  
Envelope Membranes ◽  
Sheath Cells

The intercellular and intracellular distributions of nitrate assimilating enzymes were studied. Nitrate reductase was found to be localized on the chloroplast envelope membranes. The chloroplastic NADPH – glutamate dehydrogenase was concentrated in the mesophyll cells. The extrachloroplastic NADH – glutamate dehydrogenase was localized in the bundle sheath cells. Glutamate synthesized in the mesophyll chloroplasts was interpreted to be utilized exclusively in the synthesis of aspartate, while in the bundle sheath cells it was thought to be consumed in other cellular metabolic processes. Based on the results, a scheme is proposed to account for the nitrate metabolism in the leaves of Eleusine coracana Gaertn. in relation to its aspartate-type C-4 pathway of photosynthesis.

Structure of the chloroplast and its DNA in chloromonadophycean algae

1981 ◽  
Vol 49 (1) ◽  
pp. 401-409
Author(s):  
A.W. Coleman ◽  
P. Heywood
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Membrane ◽  
Nuclear Envelope ◽  
Chloroplast Dna ◽  
Single Layer ◽  
Longitudinal Axis ◽  
Chloroplast Envelope ◽  
Large Numbers ◽  
Gonyostomum Semen ◽  
Chloroplast Stroma

The arrangement and ultrastructure of chloroplasts is described for the Chloromonadophycean algae gonyostomum semen Diesing and Vacuolaria virescens Cienkowsky. The chloroplasts are present in large numbers and are discoid structures approximately 3–4 micrometer in length by 2–3 micrometer in width. In Gonyostomum semen the chloroplasts form a single layer immediately interior to the cell membrane; frequently their longitudinal axis parallels the longitudinal axis of the cell. The chloroplasts in Vacuolaria virescens are more than I layer deep and do not appear to be preferentially oriented. In both organisms, chloroplast bands usually consist of 3 apposed thylakoids, although fusion and interconnections between adjacent bands frequently occur. External to the girdle band (the outermost thylakoids) is the chloroplast envelope. This is bounded by endoplasmic reticulum but there is no immediately apparent continuity between this endoplasmic reticulum and the nuclear envelope. Electron-dense spheres in the chloroplast stroma are thought to be lipid food reserve. Ring-shaped electron-translucent regions in the chloroplast contain chloroplast DNA. The DNA is distributed along this ring in an uneven fashion and, when stained, resembles a string of beads. Each plastid has I ring, and the ring is unbroken in the intact plastid.

Properties and Regulation of Adenylate Kinase From Zea mays Leaf Operating in C4 Pathway Photosynthesis

1982 ◽  
Vol 9 (3) ◽  
pp. 287 ◽  
Author(s):  
MD Hatch
Keyword(s):  
Zea Mays ◽  
Adenylate Kinase ◽  
Kinase Activity ◽  
Mesophyll Cell ◽  
Reverse Reaction ◽  
Mesophyll Cells ◽  
Ph Optimum ◽  
Strong Inhibitor ◽  
Cell Extracts ◽  
Regulatory Properties

Adenylate kinase from the mesophyll cells of Zea mays was partially purified and its kinetic and regulatory properties determined. Fractionation of mesophyll cell extracts by (NH4)2SO4 precipitation, filtration on Sephacryl S-200 and diethylaminoethylcellulose chromatography gave a fraction purified about 90-fold. For the reaction in the direction of ADP synthesis (forward reaction), activity was influenced by a complex interaction between Mg2+, ATP and pH. Optimal activity was observed with a Mg2+ to ATP ratio of about unity and the pH optimum under these conditions was about 8.0. With an excess of Mg2+, activity was reduced and the pH optimum was shifted to lower values. Varying ATP or AMP in a lower range of concentrations gave simple Michaelis- Menten responses. However, at higher concentrations there was a complex response to increasing ATP, and AMP became inhibitory. For the reverse reaction the Km (ADP) was about 70 �M and the pH optimum was between 8.0 and 8.5. AMP was a strong inhibitor of the reverse reaction (competitive with respect to ADP), the KI being about 40 �M. Several other metabolites tested had no effect on adenylate kinase activity. Adenylate kinase extracted from washed mesophyll chloroplasts had essentially identical properties.

scholarly journals Different Cell Wall-Degradation Ability Leads to Tissue-Specificity between Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola

Pathogens ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 187
Author(s):  
Jianbo Cao ◽  
Chuanliang Chu ◽  
Meng Zhang ◽  
Limin He ◽  
Lihong Qin ◽  
...  
Keyword(s):  
Cell Wall ◽  
Tissue Specificity ◽  
Mesophyll Cell ◽  
Xanthomonas Oryzae ◽  
Cell Wall Degradation ◽  
Intercellular Spaces ◽  
Mesophyll Cells ◽  
Degradation Ability

Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) lead to the devastating rice bacterial diseases and have a very close genetic relationship. There are tissue-specificity differences between Xoo and Xoc, i.e., Xoo only proliferating in xylem vessels and Xoc spreading in intercellular space of mesophyll cell. But there is little known about the determinants of tissue-specificity between Xoo and Xoc. Here we show that Xoc can spread in the intercellular spaces of mesophyll cells to form streak lesions. But Xoo is restricted to growth in the intercellular spaces of mesophyll cells on the inoculation sites. In vivo, Xoc largely breaks the surface and inner structures of cell wall in mesophyll cells in comparison with Xoo. In vitro, Xoc strongly damages the cellulose filter paper in comparison with Xoo. These results suggest that the stronger cell wall-degradation ability of Xoc than that of Xoo may be directly determining the tissue-specificity.

Role of Changes in Cell Size in the Evolution of Wheat

1974 ◽  
Vol 1 (1) ◽  
pp. 157 ◽  
Author(s):  
RL Dunstone ◽  
LT Evans
Keyword(s):  
Grain Size ◽  
Cell Size ◽  
Mesophyll Cell ◽  
Cell Number ◽  
Aleurone Layer ◽  
Endosperm Cell ◽  
Projected Area ◽  
Mesophyll Cells ◽  
Blade Area

The objective of the present work was to examine to what extent increase in cell size has contributed to the parallel increases in leaf and grain size in the course of evolution in wheat. Eighteen lines were chosen to represent wild and cultivated wheats at the diploid and tetraploid levels, cultivated hexaploid wheats, and the two Aegilops species likely to have contributed the B and D genomes. All plants were grown at 21/16�C under natural light. The penultimate leaves and the basal grains from central spikelets were selected for comparison. The projected area of separated mesophyll cells from leaves was 1.5–2 times larger in the cultivated tetraploid and hexaploid wheats than in the diploids, and correlated positively but weakly with leaf blade area (r = 0.50), and negatively with photosynthetic rate in Triticum species (r = -0.66). Cell size in the endosperm bore no relation to cell size in the aleurone layer or mesophyll, or to grain volume. Aleurone cell size, however, correlated positively with both grain volume (r = 0.82) and mesophyll cell size (r = 0.79). Increase in grain weight during evolution has not involved increase in either specific gravity of the mature grain or endosperm cell size. Presumably increase in endosperm cell number has been the major factor. With increase in grain size during evolution there has been a fall in percentage nitrogen in the grain.

Bundle sheath cells and cell-specific plastid development in Arabidopsis leaves

Development ◽  
1998 ◽  
Vol 125 (10) ◽  
pp. 1815-1822 ◽  
Author(s):  
E.A. Kinsman ◽  
K.A. Pyke
Keyword(s):  
Vascular Tissue ◽  
Chloroplast Development ◽  
Mesophyll Cell ◽  
Ultrastructural Level ◽  
Bundle Sheath ◽  
Plastid Development ◽  
Mesophyll Cells ◽  
Differential Development ◽  
Bundle Sheath Cells ◽  
Sheath Cells

Bundle sheath cells form a sheath around the entire vascular tissue in Arabidopsis leaves and constitute a distinct leaf cell type, as defined by their elongate morphology, their position adjacent to the vein and by differences in their chloroplast development compared to mesophyll cells. They constitute about 15% of chloroplast-containing cells in the leaf. In order to identify genes which play a role in the differential development of bundle sheath and mesophyll cell chloroplasts, a screen of reticulate leaf mutants of Arabidopsis was used to identify a new class of mutants termed dov (differential development of vascular-associated cells). The dov1 mutant clearly demonstrates a cell-specific difference in chloroplast development. Mutant leaves are highly reticulate with a green vascular pattern. The underlying bundle sheath cells always contain normal chloroplasts, whereas chloroplasts in mesophyll cells are abnormal, reduced in number per cell and seriously perturbed in morphology at the ultrastructural level. This demonstrates that differential chloroplast development occurs between the bundle sheath and mesophyll cells in the Arabidopsis leaf.

scholarly journals Leptosphaeria maculans Elicits Apoptosis Coincident with Leaf Lesion Formation and Hyphal Advance in Brassica napus

2008 ◽  
Vol 21 (9) ◽  
pp. 1143-1153 ◽  
Author(s):  
Caixia Li ◽  
Susan J. Barker ◽  
David G. Gilchrist ◽  
James E. Lincoln ◽  
Wallace A. Cowling
Keyword(s):  
Brassica Napus ◽  
Trypan Blue ◽  
Cell Damage ◽  
Leptosphaeria Maculans ◽  
Mesophyll Cell ◽  
Healthy Tissue ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Cell Contact ◽  
Mesophyll Cells ◽  
Dependent Component

Programmed cell death, with many of the morphological markers of apoptosis, is increasingly recognized as an important process in plant disease. We have investigated the involvement and potential role of apoptosis during the formation of leaf lesions by the fungus Leptosphaeria maculans on susceptible Brassica napus cv. Westar. There were no signs of host cell damage until 7 to 8 days postinoculation (dpi), when trypan-blue-stained leaf mesophyll cells were first detected. Hyphae were visible in the intercellular spaces of the inoculated area from 5 dpi and were associated with trypan-blue-stained cells at 8 to 9 dpi. Hallmarks of apoptosis, observed coincident with or immediately prior to the formation of leaf lesions at 8 to 10 dpi, included membrane shrinkage of the mesophyll cell cytoplasm, loss of cell to cell contact in mesophyll cells, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling of nuclei in apparently “healthy” tissue immediately adjacent to dead areas. Hyphae were highly branched and prolific in the “healthy” tissue immediately adjacent to dead areas 9 to 10 dpi, and formed pycnidia inside dead areas 11 to 12 dpi. Coinfiltration of the tetrapeptide caspase inhibitor Ac-DEVD-CHO with spores of the pathogen significantly suppressed development of leaf lesions but did not affect fungus viability. We hypothesize that L. maculans elicits apoptosis as a dependent component of pathogenesis in susceptible B. napus, and that the fungus uses apoptotic cells as a source of nutrition for reproduction and further growth.

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