硅酸盐提高番茄抗盐性的效应与生理机制

研究了盐胁迫下外源硅对盐敏感番茄(Solanum lycopersicum)中杂9号和耐盐番茄金鹏朝冠幼苗生长、根系特征、光合作用、渗透调节及抗氧化酶活性的影响,以探讨硅提高番茄抗盐性的生理机制。结果表明,在150 mmol·L-1Na Cl胁迫下,两个番茄品种的生物量、净光合速率、抗氧化酶(超氧化物歧化酶、过氧化氢酶和过氧化物酶)活性、可溶性蛋白含量及渗透势均显著降低,而H2O2和丙二醛含量显著升高;外源硅可显著改善盐胁迫下番茄的生长、提高光合和蒸腾作用及抗氧化酶活性、促进根系生长、降低膜脂过氧化;不同浓度硅对盐胁迫的缓解效果不同,两个品种均在硅酸盐浓度为2.0 mmol·L-1左右时缓解效果最好。硅可通过促进番茄根系的生长和水分吸收、提高叶片的光合作用及降低植株的氧化损伤来提高其抗盐性,而渗透调节与降低蒸腾失水不是本试验条件下硅诱导番茄抗盐的机理。

Effect of Silicate on Salt Resistance in Tomato and Underlying Physiological Mechanisms

Tomato plant is a silicon-excluder and therefore an ideal plant material for studying the physiological and biochemical mechanisms of silicon-mediated resistance to various environmental stresses including salinity. However, there is relatively little research on the effect of silicon on salt resistance in tomato plant and the underlying mechanisms. In this study, the effects of exogenous silicate on plant growth, root characteristics, photosynthesis, osmotic adjustment and activities of antioxidant enzymes in tomato plants were investigated in salt-sensitive cv. Zhongza No.9 and salt-tolerant cv. Jinpengchaoguan under salt stress. Plants were grown in diluted Hoagland solution with or without addition of silicate under salt stress. Under 150 mmol·L^-1 NaCl stress, biomass, net photosynthetic rate, activities of antioxidant enzymes(superoxide dismutase, catalase and peroxidase), soluble protein content and osmotic potential of tomato were all significantly decreased; while the contents of H₂O₂ and malonaldehyde were obviously increased. Additions of exogenous silicate significantly improved plant(shoots and roots) growth, increased photosynthesis, transpiration and activities of antioxidant enzymes, but decreased lipid peroxidation. The alleviative effects of silicate on salt resistance were concentration-dependant, with about 2.0 mmol·L^-1 of optimum silicate concentration for both cultivars. The present results suggest that silicon could increase salt resistance by enhancing root growth and water uptake, improving photosynthesis and decreasing oxidative damages in tomato seedlings; whereas osmotic adjustment and decrease in transpiration might not be the mechanisms for silicon-mediated salt resistance under the present experimental conditions. Silicon enhancement of salt tolerance in tomato plants suggests a potential application of silicon fertilizer in tomato production.