ANATOMICAL, HISTOCHEMICAL AND ULTRASTRUCTURAL FEATURES OF THE SEAGRASS PHYLLOSPADIX SCOULERI HOOK

Aspects of the anatomy, histochemistry and ultrastructure of vegetative organs of the North American seagrass Phyllospadix scouleri Hook. (Family Zosteraceae) were investigated. It can be distinguished from Japanese species of the same genus on the basis of leaf anatomy and ultrastructure. In common with other members of the family, leaf blades of P. scouleri possess epidermal cells with transfer cell features, subcuticular cavities in the outer wall of these cells, sieve tube elements with nacreous walls, and vascular parenchyma cells with transfer cell characteristics. Some anatomical and ultrastructural features of P. scouleri could be considered to represent adaptations to its habitat (rocky substrate and surf exposure). These include the development of mechanical tissues composed of cellulose cell walls in all vegetative organs to allow for flexibility, secretion of material by the roots for adhesion to the rocks, modification of the nodal regions of rhizomes to cope with strong water movements, and development of a thick cuticular covering over the rhizome surface for protection.