PHYSIOLOGY OF SALT EXCRETION IN THE MANGROVE AVICENNIA MARINA (FORSK.) VIERH

Abstract

Diurnal and long‐term excretion by leaves of Avicennia marina seedlings growing in aqueous culture was correlated with substrate salinity and transpiration. Excretion was greater in 100% than 50% seawater but the reverse was true for transpiration. The diurnal excretion pattern, with exudation minimal during the day and maximal during the night, showed a negative correlation with the daily transpiration pattern. The total amount of salt excreted, however, showed a positive correlation with the total amount of water transpired. Root and xylem sap salinities were linearly related to substrate salinity but leaf Na+ increased to a maximum, indicating that control of leaf salt content is at the foliar, rather than the root level. Copyright © 1982, Wiley Blackwell. All rights reserved