硅在植物体内的分布和吸收及其在病害逆境胁迫中的抗性作用

Distribution and absorption of silicon in plant and its role in plant disease resistance under environmental stress

硅在地壳中含量位居第二位,尽管还没有被列为植物生长的必需营养元素,但它在促进植物生长发育和营养吸收、提高植物对非生物逆境胁迫和生物逆境胁迫的抗性等方面都具有重要作用。综述了近些年来国内外关于硅在植物体内的分布、吸收及其生理效应,重点介绍了硅在病害逆境胁迫中的抗性作用机理。高等植物以单硅酸[Si(OH)4]的形式吸收硅,存在硅的主动吸收和被动吸收机制。硅主要沉积在叶片及叶鞘表皮细胞,形成硅化细胞和角质-硅双层结构,能增强寄主植物细胞壁的机械强度和稳固性,从而延缓和抵御病菌的侵入和扩展。更多的证据表明,硅处理能增加植物叶片保护酶(过氧化物酶、多酚氧化酶、苯丙氨酸解氨酶等)活性和诱导寄主产生次生代谢抗性物质(如植保素、多酚类化合物、木质素),从而激活植物的防御系统,增强对病原菌的抵抗能力。分子水平上的研究显示,硅能诱导与植物防御机制相关的基因表达,参与抗病信号分子(如水杨酸、茉莉酸和乙烯)在信号传导中的作用。

Silicon （Si） is the second largest abundant mineral element in the earth＇s crust. Although Si is still not listed as an essential element for the majority of plant species,it plays important roles in stimulating plant growth and nutrition uptake and enhancing plant resistance to abiotic and biotic stresses. This paper reviewed the distribution and absorption of Si in plant and its physiological functions with focusing on the mechanisms of Si mediated pathogen resistance. Higher plants mainly take up Si in the form of [Si（OH）4],and there are active and passive Si uptake mechanisms. Silicon can deposit in the epidermal cell walls beneath the cuticle,form a cuticle-Si double layer and enhance cell wall mechanical strength and stability,and therefore retard and resist pathogen from penetration and spreading. More research evidence shows that Si-treated plants can significantly increase the activity of protective enzymes such as peroxidase,polyphenol oxidase,phenylalanine ammonia-lyase,etc. in leaves and the production of antifungal compounds such as phenolic metabolism product,phytoalexins,pathogenesis-related proteins,etc.,which in turn activate the plant defense system and enhance the plant resistance to pathogen. Studies in molecular level show that Si can induce the expression of defense-related genes as well as interact with disease-resistant signal molecules such as salicylic acid,jasmonic acid and ethylene for signal transduction.