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Further Evidence for Osmoregulation in Epidermal Leaf Cells of Seagrasses

Richard Jagels
American Journal of Botany
Vol. 70, No. 3 (Mar., 1983), pp. 327-333
Stable URL: http://www.jstor.org/stable/2443240
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Further Evidence for Osmoregulation in Epidermal Leaf Cells of Seagrasses
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Abstract

A comparison of the epidermal leaf cell ultrastructure of three seagrasses, Thalassia testudinum (tropical, high salinity), Zostera marina (North temperate, moderate salinity), and Ruppia maritima (North temperate, brackish) provides confirmation for the theory that an invaginated plasmalemma-mitochondrial transport system is developed at least in part as a response to salt concentration. Cytochemical localization of presumed Cl- ion provides further evidence for the presence of a salt secretion or exclusion mechanism. Immature epidermal leaf cells communicate with each other and with mesophyll cells through numerous plasmodesmata, but during cell maturation these cytoplasmic connections are lost and the apoplastic transport system develops to replace the symplastic one. The two North temperate region seagrasses contain cytoplasmic lipids which are absent in the tropical species. Thalassia and Zostera have chloroplasts which lack starch, but stain densely for polysaccharides with thiocarbohydrazide. The polysaccharide staining is essentially negative in the chloroplasts of Ruppia, but mesophyll chloroplasts of this brackish water species contain starch. These and other cytological findings are compared with other seagrasses.

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