Effect of NaCl Stress on Na~+,K~+ Content in Different Cultivars of Pumpkin Seedlings

Variations of Na+, and K+ content, the ratios of Na+/K+ in shoot and root of seedlings in 19 pumpkin cultivars were investigated after an 8-day exposure to 300 mmol/L NaCl. The results showed that the content of Na+ significantly increased while K+ content decreased, then the ion balance was broken. The relative absorption of salt ions and nutritional elements were reflected in the variations of Na+ content and the ratios of Na+/ K+. Na+ content in root and the ratios of Na+/ K+ in shoot in Q1 (Qingli) were significantly higher than those in H2 (Heimi pumpkin), H3 (Cucurbita ficifolia). From these results, it could be inferred that the variation tendency of Na+ content and the ratios of Na+/ K+ in shoot of different pumpkin cultivar seedlings were nearly in consistent with the salt injury index of those under NaCl stress. This further proved that strong salt-tolerance of Q1 was related to the low ratios of Na +/ K+ in shoot and the high content of K+ ions under salt stress. The sensitivity of H2 and H3 to salt was connected with the high ratios of Na+/ K+ in shoot, and the low content of K+ ions under salt stress.