Cytochemical localization of ATPase activity in the leaves of a seagrass and a submerged halophyte

Abstract

Flowering plants that grow submerged in seawater are known as seagrasses, while those that grow submerged in water of generally lower and varying salinity as in estuaries, are known as submerged halophytes. Knowledge of salt tolerance mechanisms in both groups of plants is important to our understanding of their biology. Recently, high ATPase activity was reported to be associated with the copiously-invaginated plasma membrane of leaf epidermal cells of a seagrass (Zostera marina), suggesting that ATPase played a role in salt regulation. In the present study, the seagrass Halophila ovalis and the submerged halophyte Ruppia maritima growing at salinities of 35°/00 and 25°/00 respectively, were used. The subcellular distribution of ATPase in leaf epidermal cells of both submerged aquatics was accomplished using a lead precipitation technique specific for ATPase activity. Lead deposits in the cells were an indication of sites of ATPase activity. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) microanalysis using a Joel 6100 SEM with a Noran Voyager 2100 EDX microanalyser, were used to study lead distribution. Ultrathin sections for the TEM were examined unstained.