scholarly journals Electron Probe Microanalysis of Potassium and Chloride in Freeze-Substituted Leaf Sections of Zea Mays

1973 ◽  
Vol 26 (5) ◽  
pp. 1015 ◽  
Author(s):  
CK Pallaghy
Keyword(s):  
Potassium Concentration ◽  
Cell Types ◽  
Bundle Sheath ◽  
Concentration Gradients ◽  
Mesophyll Cells ◽  
Transmission Electron ◽  
Bundle Sheath Cells ◽  
Scanning Transmission ◽  
Diamond Knife ◽  
Sheath Cells

Small sections of leaves were floated on distilled water under either light or dark conditions, and were freeze-substituted in a 1 % solution of osmium tetroxide in acetone at -78�C followed by embedding in an epoxy resin. Approximately I-11m-thick sections were cut using a dry diamond knife and examined by scanning transmission electron microscopy. The relative concentrations of potassium and chloride in subcellular compartments were determined using an energy dispersive X-ray analyser. The concentration of sodium in the leaf (1�7 m-equivjkg of wet tissue) was too low to be detected by this method. The spatial resolution of this technique was sufficient to distinguish between concentrations in the chloroplasts, cytoplasm, vacuole, and nuclei. The concentration of chloride in stomata and some other epidermal cells was very much higher than in either mesophyll or bundle sheath cells. The potassium concentration in some vascular cells was at least two- to threefold higher than that in mesophyll or bundle sheath cells. The Cl : K ratio in mesophyll and bundle sheath cells resembled that in the solution (0 �10) used for growing the plants. The concentration of chloride in the "free" cytoplasm of mesophyll cells was always very low. Significant differences were found in the "ion" relations of mesophyll and bundle sheath cells. Whereas the ratio of potassium concentration between the vacuole and chloroplasts of mesophyll cells was high (1 �19) in the light and low (0�65) in the dark, the opposite was true for bundle sheath cells-O� 65 and 0�86 respectively. The ratio of potassium concentration between the vacuo les of mesophyll and those of bundle sheath cells was 1 �48 in the light, but only 0�76 in the dark. These concentration gradients are discussed in relation to a possible transfer of organic acid salts of potassium between these two cell types.

bundle sheath defective, a mutation that disrupts cellular differentiation in maize leaves

Development ◽  
1994 ◽  
Vol 120 (3) ◽  
pp. 673-681 ◽  
Author(s):  
J. A. Langdale ◽  
C. A. Kidner
Keyword(s):  
Gene Action ◽  
Morphological Differentiation ◽  
Cell Types ◽  
Bundle Sheath ◽  
Sheath Cell ◽  
Mesophyll Cells ◽  
Bundle Sheath Cell ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Sheath Cells

Post-primordial differentiation events in developing maize leaves produce two photosynthetic cell types (bundle sheath and mesophyll) that are morphologically and biochemically distinct. We have isolated a mutation that disrupts the differentiation of one of these cell types in light-grown leaves. bundle sheath defective 1-mutable 1 (bsd1-m1) is an unstable allele that was induced by transposon mutagenesis. In the bundle sheath cells of bsd1-m1 leaves, chloroplasts differentiate aberrantly and C4 photosynthetic enzymes are absent. The development of mesophyll cells is unaffected. In dark-grown bsd1-m1 seedlings, morphological differentiation of etioplasts is only disrupted in bundle sheath cells but photosynthetic enzyme accumulation patterns are altered in both cell types. These data suggest that, during normal development, the Bsd1 gene directs the morphological differentiation of chloroplasts in a light-independent and bundle sheath cell-specific fashion. In contrast, Bsd1 gene action on photosynthetic gene expression patterns is cell-type independent in the dark (C3 state) but bundle sheath cell-specific in the light (C4 state). Current models hypothesize that C4 photosynthetic differentiation is achieved through a light-induced interaction between bundle sheath and mesophyll cells (J. A. Langdale and T. Nelson (1991) Trends in Genetics 7, 191–196). Based on the data shown in this paper, we propose that induction of the C4 state restricts Bsd1 gene action to bundle sheath cells.

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.

Phenolic Deposits and Kranz Syndrome in Leaf Tissues of Spotted (Euphorbia maculata) and Prostrate (Euphorbia supina) Spurge

Weed Science ◽  
1983 ◽  
Vol 31 (1) ◽  
pp. 131-136 ◽  
Author(s):  
C. Dennis Elmore ◽  
Rex N. Paul
Keyword(s):  
Electron Microscopy ◽  
Phenolic Compounds ◽  
Light And Electron Microscopy ◽  
Bundle Sheath ◽  
Fixation Technique ◽  
Mesophyll Cells ◽  
Kranz Anatomy ◽  
Bundle Sheath Cells ◽  
Leaf Tissues ◽  
Sheath Cells

Spotted spurge (Euphorbia maculataL.) and prostrate spurge (E. supinaRaf.), both in subgenusChamesyce,were examined by light and electron microscopy using a caffeine - fixation technique to sequester the phenolic pools intercellularly. Both species have typical dicotyledon-type Kranz anatomy. Sequestered phenolic pools were located in vacuoles in epidermal and mesophyll cells. Only in spotted spurge, however, were additional phenolic pools formed in bundle - sheath cells. This study was undertaken because allelopathy has been demonstrated in prostrate spurge and because phenolic compounds have been implicated in allelopathy. These results would indicate that spotted spurge should also be allelopathic.

Photosynthesis in Gomphrena celosioides and Its Classification Amongst C4-pathway Plants

1976 ◽  
Vol 3 (6) ◽  
pp. 863 ◽  
Author(s):  
E Repo ◽  
MD Hatch
Keyword(s):  
Malate Dehydrogenase ◽  
Malic Enzyme ◽  
Bundle Sheath ◽  
Mesophyll Cells ◽  
C4 Species ◽  
Bundle Sheath Cells ◽  
Major Route ◽  
Gomphrena Celosioides ◽  
A Minor ◽  
Sheath Cells

Monocotyledonous C4 species classified as NADP-ME-type transfer malate from mesophyll to bundle sheath cells where this acid is decarboxylated via NADP malic enzyme (EC 1.1.1.40) to yield pyruvate and CO2. The dicotyledon G. celosioides is most appropriately classified in thls group on the basis of high leaf activities of NADP malic enzyme and NADP malate dehydrogenase (EC 1.1.1.82). However, this species contains high aspartate aminotransferase (EC 2.6.1.1) and alanine aminotransferase (EC 2.6.1.2) activities and centripetally located bundle sheath chloroplasts, features more typical of other groups of C4 species that cycle aspartate and alanine between mesophyll and bundle sheath cells. During the present study, we found that these aminotransferases and NADP malate dehydrogenase were predominantly located in mesophyll cells, that malate was the major C4 acid labelled when leaves were exposed to 14CO2, and that label was initially lost most rapidly from the C-4 of malate during a chase in 12CO2. These results are consistent with the major route of photosynthetic metabolism being the same as that operative in other NADP-ME-type species, although this may be supplemented by a minor route utilizing aspartate. In contrast to monocotyledonous NADP-ME-type C4 species, isolated bundle sheath cells from G. celosioides were capable of rapid photoreduction of NADP as judged by products formed during assimilation of 14CO2 and their capacity for light-dependent oxygen evolution. This was related to a relatively high frequency of single unstacked granum in the chloroplasts of these cells.

Comparison of photosynthetic carbon reduction (Kranz) cells having different ontogenetic origins in the C4 NADP – malic enzyme grass Arundinella hirta

1990 ◽  
Vol 68 (6) ◽  
pp. 1222-1232 ◽  
Author(s):  
Nancy G. Dengler ◽  
Ronald E. Dengler ◽  
Douglas J. Grenville
Keyword(s):  
Cell Walls ◽  
Vascular Tissue ◽  
Cell Types ◽  
Bundle Sheath ◽  
Carbon Reduction ◽  
Bundle Sheath Cells ◽  
Photosynthetic Carbon ◽  
Arundinella Hirta ◽  
Photosynthetic Carbon Reduction ◽  
Sheath Cells

The C4 grass Arundinella hirta is characterized by unusual leaf blade anatomy: photosynthetic carbon reduction takes place both within the chlorenchymatous bundle sheath cells of the longitudinal veins and within longitudinal strands of "distinctive cells" that form part of the leaf mesophyll and are often completely isolated from vascular tissue. Although they are equivalent physiologically, these two cell types have different ontogenetic origins: bundle sheath cells are delimited from procambium early in leaf development, whereas distinctive cells differentiate from ground meristem at a later developmental stage. Although the two cell types share numerous cytological features (large chloroplasts with reduced grana, thick cell walls with a suberin lamella), we also found significant differences in cell lengths, length to width ratios, cell cross-sectional areas, organelle numbers per cell cross section, phenol content of the cell walls, and numbers of pit fields in the longitudinal cell walls. The size and shape of bundle sheath cells are likely a direct consequence of procambial origin. The thicker walls of bundle sheath cells (in major veins) and their greater lignification may reflect the inductive effect of cell differentiation in the proximity of sclerenchyma and vascular tissues. Differences between major and minor vein bundle sheath cells may reflect differences in the timing of initiation of procambial strands. Our analysis of cell wall characteristics has also shown the presence of numerous primary pit fields in the transverse walls between adjacent distinctive cells in a file; plasmodesmata in these pit fields form a pathway for longitudinal symplastic transport not previously known to exist.

scholarly journals Arabidopsis leaf hydraulic conductance is regulated by xylem-sap pH, controlled, in turn, by a P-type H+-ATPase of vascular bundle sheath cells

2017 ◽  
Author(s):  
Yael Grunwald ◽  
Noa Wigoda ◽  
Nir Sade ◽  
Adi Yaaran ◽  
Tanmayee Torne ◽  
...  
Keyword(s):  
Proton Pump ◽  
Vascular Bundle ◽  
Xylem Sap ◽  
Hydraulic Conductance ◽  
Bundle Sheath ◽  
List Type ◽  
Mesophyll Cells ◽  
Leaf Hydraulic Conductance ◽  
Bundle Sheath Cells ◽  
Sheath Cells

AbstractThe leaf vascular bundle sheath cells (BSCs) that tightly envelop the leaf veins, are a selective and dynamic barrier to xylem-sap water and solutes radially entering the mesophyll cells. Under normal conditions, xylem-sap pH of <6 is presumably important for driving and regulating the transmembranal solute transport. Having discovered recently a differentially high expression of a BSCs proton pump, AHA2, we now test the hypothesis that it regulates this pH and leaf radial water fluxes.We monitored the xylem-sap pH in the veins of detached leaves of WT Arabidopsis, AHA mutants, and aha2 mutants complemented with AHA2 gene solely in BSCs. We tested an AHA inhibitor and stimulator, and different pH buffers. We monitored their impact on the xylem-sap pH and the whole leaf hydraulic conductance (Kleaf), and the effect of pH on the water osmotic permeability (Pf) of isolated BSCs protoplasts.Our results demonstrated that AHA2 is necessary for xylem-sap acidification, and in turn, for elevating Kleaf. Conversely, knocking out AHA2 alkalinized the xylem-sap. Also, elevating xylem sap pH to 7.5 reduced Kleaf and elevating external pH to 7.5 decreased the BSCs Pf.All these demonstrate a causative link between AHA2 activity in BSCs and leaf radial water conductance.One-sentence summaryBundle-sheath cells can control the leaf hydraulic conductance by proton-pump-regulated xylem sap pH

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