Salt Stress and Comparative Physiology in the Gramineae. I. Ion Relations of Two Salt- and Water-Stressed Barley Cultivars, California Mariout and Arimar

Abstract

Two barley cultivars, California Mariout and the somewhat more salt-sensitive Arimar, were grown under different salinity regimes and in isosmotic polyethylene glycol (PEG) solutions. Shoot growth of both cultivars was inhibited more by NaCl than by PEG. The effects of various salt and osmotic stress regimes on the K⁺, Na⁺ and Cl^- status, the fresh weight : dry weight ratio and osmotic potential of the tissue were determined. The changes in these parameters were dependent on the rate at which the stress was applied. A gradual increase in stress led to K⁺/Na⁺ exchange in the shoot so as to maintain an almost constant (K⁺ + Na⁺) content on a dry weight basis. Tissue dehydration largely accounted for the increase in osmotic pressure. In contrast, salt shock resulted in a rapid nonselective accumulation of salt. Both osmotic stress and shock similarly brought about a dehydration of shoot tissue. A gradual osmotic stress slightly enhanced K⁺ accumulation in the roots. The greater salt sensitivity of the Arimar cultivar appeared to be related to a poorer ability to regulate Na⁺ plus Cl^- accumulation in shoots.