Effect Of Exogenous Se On Photosynthetic Carbon Assimilation In Tomato Seedlings Under NaCl Stress

Salt stress is one of the most important abiotic stresses limiting crop growth. Although processing tomato is one of the most important vegetable crops cultivated in Xinjiang and the demand of market for it is large, the secondary salinization of soil leads to a decrease in the yield and quality of processing tomato.So it is crunch time for research to improve the salt tolerance of processing tomato.In this study, tomato cultivar ‘shuangfeng 87-5’ was used as experiment material, and the effects of exogenous Se on photosynthetic carbon assimilation, antioxidant system, mineral element of content and distribution in processing tomato seedlings under salt stress was investigated. The main results obtained were presented as follows:1. Na Cl stress inhibited the growth of processing tomato seedlings, whereas application of exogenous Se reversed the negative effects of Na Cl stress.2. Na Cl stress significantly decreased net photosynthetic rate(Pn) and inhibited the activity of Rubisco, RCA and FBPase, as well as the expression levels of key genes in relative to CO2 assimilation in tomato seedlings Na Cl stress leaded to increase of dark respiration rate(Rd) and decline of apparent quantum efficiency of photosynthesis, Rubisco maximum carboxylation efficiency and Ru BP regeneration rate, thereby inhibited the accumulation of photosynthetic product and the growth of plant. Application of exogenous Se significantly increased photochemical activity of PSⅡ, the apparent quantum efficiency of photosynthesis(AQY), Rubisco maximum carboxylation efficiency and Ru BP regeneration rate, the activity of Rubisco, RCA and FBPase, the expression levels of key genes in relative to CO2 assimilation, decreased Rd, reduced the inhibition of photosynthetic carbon assimilation under Na Cl stress, resulting in increase of Pn, accumulated photosynthetic products, and effectively alleviated inhibition of seedling growth in tomato under Na Cl stress.3. Na Cl stress inhibited significantly the activity and expression level of m RNA of most antioxidant enzymes in leaves of tomato seedlings, and reduced redox state, increased oxidative stress,accumulated a large amount of active oxygen can not be cleared in time, increased membrane lipid peroxidation.Exogenous selenium induced increse of redox state, formation of leaves under Na Cl stress increased, the activity and expression level of m RNA of enzyme related antioxidant, enhanced the scavenging ability of active oxygen, alleviating membrane lipid peroxidation in leaves of tomato seedlings under Na Cl stress.4. Na Cl stress increased the element content of Na and Cl, decreased the element content of K, Ca and Mg in leaves and roots, leading to decrease of roots activity and ion toxicity in leaves. Application of exogenous Se significantly increased the element content of K, Ca and Mg in leaves and the element content of Ca and Mg in roots, roots activity and transport speed of K+. Na Cl stress accumulated the element content of Cl in phloem, alleviating damage on chloroplast of toxic ions in tomato leaves.