Halophytes

Abstract

Halophytes are plants adapted to live in a saline environment, be it seawater, a salt-water marsh, or a salt-desert; nearly all are angiosperms. The growth of dicotyledonous halophytes is frequently stimulated by salt, although that of most monocotyledonous halophytes is not. Survival requires osmotic adjustment, which is commonly achieved by using the ions present in the environment and which is associated with succulence in dicotyledons but generally not in monocotyledons. At the cellular level, survival depends on the ability of the plant to compartmentalize, in vacuoles, the ions used for osmotic adjustment, particularly sodium and chloride. A vital feature of the physiology of these plants is their ability to accumulate sufficient ions to maintain growth while avoiding either a water deficit or an excess of ions, either of which could prove toxic. The means by which relatively constant ion concentrations in the shoot are maintained are considered. The conclusion is drawn that ion uptake by the roots is not controlled by the shoots; rather, shoot growth is regulated by the supply of ions from the roots. The agricultural importance of halophytes in a world where most of the water is salty at any given moment is emphasized.