Zostera capensis Setchell.: I. Observations on the Fine Structure of the Leaf Epidermis

Summary Preliminary findings on the fine structure of the leaf epidermis of Zostera capensis are described. The epidermal cells have transfer cell characteristics. Wall ingrowths, ensheathed by the plasmalemma, are particularly well-developed along the inner tangential cell walls. Numerous mitochondria, with prominent cristae, are clustered around the ingrowths. The cells have dense cytoplasmic contents with a large population of vesicles and many profiles of smooth ER. Dictyosomes and microbodies are relatively sparse while chloroplasts, with well-developed grana systems, fill the cells. A thin but distinct cuticle covers the outer surface of the leaf. The outer tangential cell wall is about twice as thick as the other walls and has an interesting ultrastructure: the innermost part of this wall has staining characteristics which differ from the rest of the wall; wall striations, adjacent to this intenselystaining region, are more prominent here than in the other walls; and unusual sub-cuticular cavities which appear to contain some fibrillar material are present in the outermost portion of the wall. The possible physiological significance of the enlarged plasmalemma, the intensely staining inner region of the outer cell wall and the subcuticular cavities, are suggested.