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  • 1
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Assimilate translocation ; Leguminosae (paraveinal mesophyll) ; Paraveinal mesophyll ; Vacuolar protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaves of eight species of Leguminosae-Papilionoideae were examined for the presence of a highly specialized cell layer called the paraveinal mesophyli (PVM). Three species, Glycine max (L.) Merr, Psophocarpus tetragonolobus D.C. and Vigna radiata L., contained PVM; five (Medicago sativa L., Phaseolus vulgaris L., Pisum sativum L., Vicia faba L., Vigna unguiculata L.) did not. The PVM of G. max and P. tetragonolobus was anatomically identical and consisted of large, interconnected, multiarmed cells forming a network, one cell thick, spanning the region between vascular bundles and abutting the bundle sheath at the level of the phloem. The PVM of V. radiata differed in that elaborate extensions of individual bundle-sheath cells comprised the entire intervascular network. The PVM cells of all three species were large, contained a dense, thin peripheral layer of cytoplasm, and a large central vacuole. The cytoplasm contained few small chloroplasts and few microbodies, but was enriched in rough endoplasmic reticulum. Plasmodesmata were common in crosswalls between adjacent PVM cells and between PVM cells and other cell types abutting them. Vacuolar material was present in all three species, but was variable in appearance. That of G. max was present in large amounts, semifibrillar and finely dispersed. That of P. tetragonolobus was also present in large amounts but primarily as large aggregates, although some fibrillar material was also present. Vigna radiata had small amounts of vacuolar material evenly distributed between small aggregates and dispersed fibrils. Removal of flowers or young pods resulted in further increase of the vacuolar material in G. max PVM and increase of the fibrillar material in P. tetragonolobus, but had no appreciable affect on the vacuolar material in V. radiata. Histochemical staining indicated the vacuolar material in G. max and P. tetragonolobus was proteinaceous.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Assimilate compartmentation ; Dictyosome ; Glycine (paraveinal mesophyll) ; Paraveinal mesophyll ; Translocation (assimilates) ; Vacuolar protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The paraveinal mesophyll (PVM) is a unique and specialized, one-cell-thick tissue spanning the vascular bundles at the level of the phloem in soybean (Glycine max) (L.) Merr.) leaves. Its position within the leaf dictates that all photosynthate produced in the palisade and spongy mesophyll must pass through this specialized layer enroute to the phloem. Symplastic continuity, via plasmodesmata, exists between the PVM and bundle sheath, palisade parenchyma and spongy mesophyll. During leaf ontogeny the PVM is the first tissue to differentiate and at maturity these cells are six to eight times larger than other mesophyll cells, are highly vacuolate, and are interconnected by tubular arms. The PVM undergoes several unique structural and metabolic modifications during leaf development. The PVM cytoplasm, in vegetative plants, is dense, enriched in rough endoplasmic reticulum and dictyosomes, but contains few, small starch-free chloroplasts and few microbodies. Unlike the tonoplast of mesophyll cells, the tonoplast of the PVM is unusually thick and dense-staining. During leaf development the vacuoles of PVM cells accumulate a glycoprotein derived from the dictyosomes which reacts with the protein staining reagents, mercuric bromophenol blue and sulfaflavine, and is degraded by Pronase. Both the vacuolar material and tonoplast are also stained by phosphotungstic acid, which at low pH is relatively selective for glycoprotein. A unique role of the PVM in the transport and compartmentation of nitrogen reserves in soybeans is discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2048
    Keywords: Assimilate compartmentation ; Glycine (paraveinal mesophyll) ; Paraveinal mesophyll ; Vacuolar protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen and carbohydrate assimilates were temporally and spatially compartmented among various cell types in soybean (Glycine max L., Merr.) leaves during seed filling. The paraveinal mesophyll (PVM), a unique cell layer found in soybean, was demonstrated to function in the synthesis, compartmentation and remobilization of nitrogen reserves prior to and during the seed-filling stages. At anthesis, the PVM vacuoles contain substantial protein which completely disappears by two weeks into the seed filling. Distinct changes in the PVM cytoplasm, tonoplast and organelles were correlated with the presence or absence of the vacuolar material. Microautoradiography following the accumulation of several radiolabeled sugars and amino acids demonstrated the glycoprotein nature of the vacuolar material. Incorporation of methionine, leucine, glucose, and glucosamine resulted in heavy labelling of the PVM vacuole, in contrast to galactose, proline, and mannose which resulted in a much reduced labelling pattern. In addition, starch is unequally compartmented and degraded among the various leaf cells during seed filling. At the end of the photoperiod at the flowering stage, the highest starch accumulation was in the second palisade layer followed by the spongy mesophyll and the first (uppermost) palisade layer. Starch in the first palisade layer was completely degraded during the dark whereas the starch in the second palisade and spongy mesophyll was not remobilized to any appreciable extent. By mid-podfilling (approximately five weeks postanthesis) starch was absent in the first palisade layer at the end of the photoperiod while the second palisade and spongy mesophyll layers contained substantial starch. Starch was remobilized from these latter cells during the remainder of seed filling when current photosynthetic production is low. Structural changes associated with cell senescence first appear in the upper palisade layer and then progress (excluding the PVM) to the second palisade and spongy mesophyll layer. The PVM and phloem appear to retain their structural integrity into the leaf yellowing stage. Reducing sink capacity by pod removal resulted in a continued accumulation of vacuolar protein, an increase in cytoplasmic volume, and fragmentation of the vacuole in the PVM. Pod removal also resulted in an increased amount of accumulated starch (which did not turn over) in all mesophyll layers, and an increase in cell size and cell-wall thickness.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of bioenergetics and biomembranes 6 (1975), S. 221-231 
    ISSN: 1573-6881
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Cyanide and mercury treatment of chloroplast membranes inactivates plastocyanin as shown by the inability of the extracted plastocyanin to restore electron transport in a bioassay on chloroplasts depleted of their endogenous plastocyanin by digitonin treatment. The extraction procedure did remore the enzyme from cyanide and mercury treated chloroplasts as shown by sodium dodecyl sulfate polyacrylamide electrophoresis of the extracts. This procedure normally shows a plastocyanin band at 11,000 dalton molecular weight and the band was present in extracts from control and cyanide or mercury treated membranes.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 6 (1987), S. 217-221 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Physiological studies show that the driving force for long distance transport and the control of nutrient movement in plants resides largely in the regulated, membrane transport of a few carbohydrates, principally sucrose. The evidence is reviewed here and biochemical studies on sucrose carrier proteins are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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