作物根系镉滞留作用及其生理生化机制  

Immobilization Effect and Its Physiology and Biochemical Mechanism of the Cadmium in Crop Roots

作　　者：王学华[1] 戴力[1] 

机构地区：[1]湖南农业大学农学院,长沙410128

出　　处：《中国农业科学》2016年第22期4323-4341,共19页Scientia Agricultura Sinica

基　　金：国家"十二五"科技支撑计划(2013BAD07B11)

摘　　要：一定程度的镉胁迫严重影响了作物的生长发育和农产品的产量及品质。文中全面综述了重金属镉胁迫对作物和人类的危害,以及镉在作物体内的吸收、转运和积累特征及其相关的主要调控基因和功能。简要概述了作物抗镉耐镉机制,重点讨论了其中的根系镉滞留作用的生理和生化机制。重金属镉主要通过根部吸收进入植株,在根中,Cd^(2+)首先进入由细胞间隙、细胞壁微孔以及细胞壁到质膜之间的空隙等构成的"自由空间",然后通过主动或被动吸收跨膜进入胞质,再经共质体或质外体途径运输到木质部导管中。水稻等作物主要通过下列途径来适应镉胁迫:细胞壁的滞留作用、原生质体的螯合作用、液泡的区室化作用、逆境蛋白和脯氨酸的积累、抗氧化酶系统活性的提高、根系的滞留作用。根系镉滞留作用作为一种重要的抗耐镉毒害的方式,在调控作物对镉的吸收、转运和分配积累,阻碍镉进入植株地上部和原生质体,减少镉对作物自身生长发育及农产品产量和品质的影响等方面起着非常重要的作用。主要包括根茎间低转运量导致的镉滞留、根系细胞壁滞留和液泡滞留。(1)根茎间低转运量导致的镉滞留。该种滞留作用主要受到根系木质部的镉装载能力和镉长距离运输载体——植物螯合肽(PCs)含量的影响;它们主要受到质膜上跨膜离子转运蛋白HMA2和HMA4以及细胞中的PCs合成酶及其相应基因(如HMA2、HMA4、PCs1等)的调控。这些蛋白和基因对木质部的镉滞留起到负调控作用。(2)细胞壁滞留作用。根系细胞壁滞留发生在质外体部分(包括细胞壁和胞间层),主要与质外体的组成成分和结构相关,其中起关键作用的是果胶多糖,半纤维素也起到一定作用。根据果胶和半纤维素滞留镉的作用方式的不同,细胞壁滞留作用可分为物理滞留和化学滞留。物理滞留主要与细胞壁A certain degree of cadmium stress has seriously influenced crop growth, development, yield and quality of farm produce. In this review, the authors comprehensively summarized the damages of Cd to crops and a human being, and the characteristics of the Cd absorption, transport and accumulation as well as their dependent main regulatory genes and their functions. The resistant and tolerant mechanisms of crops to the Cd toxicity were simply summarized, while the physiology and biochemical mechanism of the root cadmium immobilization effect which was one of them were emphatically introduced. The Cd got into the plant via the root absorption mostly, and in the root, the Cd^（2＋） entered the ＂free space＂ firstly, which is constituted by the cell space, the cell wall micropore and the space between cell wall and plasma membrane, afterwards, passed through the plasma membrane into the cytoplasm by the way of active or passive absorption, and then were transported into the xylem vessel through symplast or apoplast pathway. Rice and others crops mainly use the following ways to adapt the Cd stress： The retention effect of cell wall, the chelation effect in symplast, the compartmentation effect of vacuole, the accumulation of stress protein and proline, the enhancement of antioxidase system activity and the immobilization effect of the root. As an important way to resist and tolerate the cadmium toxicity, the immobilization effect of cadmium in crop root plays a crucial role in regulating the Cd absorption, transport, distribution and accumulation in crop, preventing Cd entering into bioplasts and shoots of plant, and reducing the harm of Cd to the growth and development of the crop and the yield and quality of the farm produce. It mainly contains the retention caused by the low root-to-shoot Cd transport volume, the cell wall and the vacuolar.（i） The retention caused by the low root-to-shoot Cd transport volume. This retention effect is mostly influenced by the xylem Cd loading capacity of the root and the

关 键 词：根系 镉 滞留作用 植物螯合肽 细胞壁 

分 类 号：S311[农业科学—作物栽培与耕作技术]