Comparative Effects of Salt and Alkali Stresses on Plant Physiology of Willow
Abstract
At present, soil salinization has become an increasingly serious concern in the world. Large areas of saline alkali land in China are a heavy constraint to the sustainable development of agriculture. In Northern China, saline alkali soil contains varied types of salt ion, such as Na Cl, Na2SO4, Na2CO3, and Na HCO3. Willow is a very important tree species for afforestation and conserving soil and water, which is often used to improve ecological environment of saline alkali land, so that it is of significance to study the salt and alkali stress on the plant physiology of willow. Salinization and alkalization of soil is a widespread environment problem, which could be divided into salt-stress and alkali-stress in terms of the salt characteristics. In fact, the destructive results caused by alkali-stress are more serious than those by salt-stress. A willow cultivar Yan Liu 1(Salix psammophila) was used to study the stress conditions of 6 salinities and 6 alkalities simulated by mixing two neutral salts(Na Cl and Na2SO4) and two alkaline salts(Na HCO3 and Na2CO3) in the molar ratio of 9∶1 respectively with 14 days' stress. The concentration range of treatment was set between 50 and 200 mmol·L-1 for salt and alkali stress. The results showed that the content of leaf water all decreased with increasing concentration of salt and alkali treatment, and more water was lost from the leaf under the alkali stress; when the alkali salt stress reached the 200mmol/L, the leaf water content was a minimum of 23.8%, which was 32% of the control(P0.01). This reached extremely significant difference, and more water content was lost than that under the salt stress. Similarly, with increasing alkali salt concentration and under alkaline salt stress, the proline, soluble sugar and soluble protein in the leaf grew. When the alkali salt concentration reached to 200 mmol·L-1, the content of proline was 100.38 μg·g-1 which was 3.18 times of the control(P0.01), reaching extremely significant difference, and was 1.57 times of the result under the salt stress. When the alkali concentration was 150 mmol·L-1, the content of soluble sugar in leaf was 2.4 mg·g-1, which was 1.86 times of the control(P0.05)reaching the significant difference, and was 1.69 times than that under the salt stress(P0.05). When the alkali concentration was 150 mmol·L-1, the content of soluble of was 7.84 mg·g-1, 1.67 times of the control(P0.05)reaching the significant difference, and 1.56 times of the result under salt stress(P0.05). The final results showed that the alkali stress was different from salt stress, and the alkali had stronger injury to willow than the salt stress.