Abstract: The responses for seedling growth, regulation of Na+ and K+ uptake and transport to shoot, ion compartmentation and Na+ efflux in saline conditions were investigated to determine adaptive mechanisms of salt tolerance in H. brevisubulatum. The results showed that, (1) the dry mass of shoot and root had no significant difference in the range of 350mmol.L-1 NaCl stress, and NaCl stress inhibited the growth of shoot more severely than that of root; (2) the increment of Na+ content in root was more than that in shoot, the decrease of K+ content in shoot less than that in root, the ratios of K+ to Na+ in shoot and root were all more than 1.0, the higher K+/Na+ resulted from the higher K+-Na+ selectivity of plasm membrane; (3) X-ray microanalysis indicated Na+ in cytoplasm was compartmented into vacuole while NaCl≥150mmol.L-1; (4) salt gland was the main path for Na+ efflux out of shoot. The conclusions were made: plants grew normally when NaCl concentration was less than 350mmol.L-1, H. brevisubulatum tended to take up less Na+ and maintain higher K+ in the shoot, Na+ secretion via salt glands and Na+ compartmentation in vaculoe were the adaptive key mechanisms of salt tolerance in H. brevisubulatum.

Key words: Hordeum brevisubulatum, NaCl stress, Salt tolerance, Ion compartmentation, Salt gland