Different effect of humidity on growth and salt tolerance of two soybean cultivars

Two soybean (Glycine max (L.) Merr) cultivars, Tachiyutaka and Dare, were g rown in pots at 30 and 70% relative humidity (RH) and treated with 0 (contr ol), 40 (moderate), 80 and 120 (severe) mM NaCl for 3 weeks. Increasing RH enhanced growth of salt sensitive cultivar, Tachiyutaka, but had no effect on salt tolerant cultivar. Dare, under control and moderate saline conditio ns. Both cultivars benefited from elevated humidity under severe saline con ditions. Cultivar Tachiyutaka had poorer ability for controlling translocat ion of Na+ to the leaves, lower Na+ exclusion ability in the roots, and low er root activity under NaCl treatment, compared with cv. Dare. The increase d growth of cv. Tachiyutaka at high RH was consistent with decreased Na+ ac cumulation in the leaves, increased stomatal conductance and root activity, while the unchanged growth of cv. Dare was consistent with similar Na+ acc umulation in the leaves, and the decreased root activity.