Salinity tolerance of different halophyte types

Abstract

The salinity tolerance of plants exhibits a great importance in agriculture of arid areas where the salinization of soils is enhanced by irrigation in an increasing scale. Arid areas in this respect are problem areas. In humid regions the salt-balance in natural ecosystems as well as in agro-ecosystems is much more favourable. Cultivated plants, used by mankind as crop-plants, are almost all rather salt-sensitive. Plants growing naturally on saline stands have evolved various mechanisms to cope with salinity.

Several types of halophytes can be distinguished. Chemically defined halophyte types are not so clearly arranged on a salinity tolerance scale than ecophysiologically and/or anatomically-morphologically defined plant types. Thus, especially halo-succulent and salt-recreting plants are the main groups, other than the highly selective grasses. Within these groups, the concept of ecotypes has been used. It is obvious, that taxonomic relations of the halophytes give indications for a typical genetic background of salinity tolerance which, however, is very complex. This leads to altered and more precise descriptions of the phenomenon ‘salinity tolerance’. The latter has to be regarded in more than one aspect on the levels of the organell, the cell, the plant tissue, the organ and the whole individual plant. An outlook to agricultural perspectives is given.