Ameliorative effects of foliar methanol spraying on salt injury to soybean seedlings differing in salt tolerance

By foliar application of a range of methanol solutions (0, 2.5, 5, 7.5, 10 %, v/v) on leaves of salt-stressed soybean seedlings, and comparing changes in plant height and relative electrolytic leakage, the appropriate concentration of foliar methanol for mitigating of salt injury to soybean was selected. On this basis, foliar application of the appropriate concentration of methanol solution was conducted on salt-stressed soybean cv. Jackson (the salt-sensitive) and cv. Lee68 (the salt-tolerant) seedlings. By comparing changes in plant dry matter weight, leaf area and net photosynthetic rate (Pn), root and leaf thiobarbituric acid reactive substances (TBARS) contents, and plant Na+, K+ contents and Na+/K+ ratios, physiological effects of foliar methanol application were analyzed. The results showed that: Use of different concentrations of methanol solution for foliar spraying all had ameliorative effects for salt-treated soybean seedlings, of which, 5 % concentration was the appropriate. Under salt stress, plant dry matter weight, leaf area and Pn of cv. Jackson and cv. Lee68 seedlings decreased significantly, TBARS contents in roots and leaves were increased significantly, K+ contents in soybean plants declined, while Na+ contents and Na+/K+ ratios increased remarkably, and as a whole, the changes in cv. Jackson were higher than those in cv. Lee68. Under salt stress plus leaf spraying of 5 % methanol, plant dry matter weight, K+ contents, leaf area and Pn of cv. Jackson and Lee68 seedlings were restored, root and leaf TBARS contents, plant Na+ contents and Na+/K+ ratios were all reduced, of which cv. Jackson displayed a more pronounced effect.