14 - Fungi and salt stress

Summary

Introduction

Salinization of soils is a growing threat to the future of agriculture in many parts of the world. Cultivation of arid and semi-arid land seems to be inevitably linked to salt accumulation; evaporation of water used for irrigation concentrates the dissolved salt and cultivation may compact the soil and cause retention of salts in the upper layers (Epstein et al., 1980). Hence, the understanding of the basic processes of salt tolerance and salt adaptation has important applied and environmental interests. An advantage of studying these processes in fungi is their experimental tractability, and the possibility of utilizing genetic approaches that are not available in other eukaryotic organisms.

Salt relations

Fungi occupy environments ranging from freshwater to cured food products and concentrated brines. Effects of increased salt concentration on fungal physiology are frequently explained in terms of the effects of a more general factor, the water potential (Ψ) of the environment. Often, this term has been used to describe the growth limits for a particular species below which growth does not occur. One should bear in mind though that the limiting value is not absolute, but depends on factors such as nutrition, temperature and the nature of the Ψ adjusting solute (Pitt & Hocking, 1977; Blomberg & Adler, 1992). The mycoflora of saline environments such as a salt marsh appears to differ little from that of more normal soils (Luard & Griffin, 1981).