Ultrastructural Characterization of the Storage Organs of Zoysia and Bermudagrass 1

Limited information exists concerning the ultrastructural characterization of storage organs of grasses including Zoysia japonica Steud and Cynodon dactylon L. The present study was undertaken to apply scanning electron microscopy in order to show differences in tissue components of rhizomes and stolons of these species which might be related to inherent low temperature tolerance. The epidermis, in all cases, contained cutinized cells which were covered by a heavily cuticularized surface layer. A sclerenchyma sheath consisting of thick‐walled, sclerified cells, five to seven cell layers thick, divided storage organs into a pith and cortex. The number of cortical cell layers separating the sheath from epidermis varied between species. A bundle sheath surrounded the vascular bundles which were located interior to the sclerenchyma sheath in both species. Cellular areas of the cortex and pith, excluding the sclerenchyma sheath, contained parenchyma cells whose main function appears to be starch storage. Cells interior to the sheath, mostly pith, stored larger quantities of starch than those exterior to the sheath. There were no major structural differences of cells between several cultivars studied or between species which would account for differences in cold hardiness. However, the heavily cuticularized epidermal surface, the thick‐walled epidermal cells, and the sclerenchyma sheath may play an important role in drought tolerance as well as thatch accumulation associated with both species.