Abstract:The experiment was carried out to study the effects of iso-osmotic Ca(NO3)2 and NaCl stress on the growth and osmotic substances of cucumber ‘Jinchun No.2’ (with less salt resistance) seedlings in hydroponics.The results showed that:(1)The fresh and dry biomass weight were significantly decreased under both salt stress,but the decreased degree that under NaCl stress exceeded under Ca(NO3)2 stress.The root activity,K+ content in root,K+/Na+ ratio,root-shoot ratio were significantly decreased,but the root relative membrane permeability increased significantly under 84 mmol·L-1 NaCl stress.(2)NaCl stress inhibited seedlings growth mainly by restraining root growth;However,the effects of Ca(NO3)2 stress on the root relative membrane permeability,K+ content,and the ratio of K+/Na+ were less than that under NaCl stress.The root activity and root-shoot ratio were significantly increased under Ca(NO3)2 stress,but the leaf water content and osmotic adjustment was less than that under NaCl stress.(3)Soluble sugar is the main osmotic adjustment substance under NaCl stress,but mainly soluble protein under Ca(NO3)2 stress.The results showed that both treatments caused damage to cucumber seedlings plant,and iso-osmotic NaCl stress brought about heavier damage than that of Ca(NO3)2 stress.Ca(NO3)2 stress inhibited growth mainly by inducing physiological drought and NaCl mainly by destroying root plasma membrane structure.