水稻幼苗镉积累特征和离体叶片耐镉性的基因型差异

Genotypic Difference of Cadmium Accumulation Characteristics and Cadmium Tolerance in Detached Leaves of Rice( Oryza sativa L.) Seedlings

水稻根系对镉(Cd)的富集能力和向地上部的转运效率直接决定着水稻地上部的Cd积累量,是影响稻米中镉含量的关键因素。提高水稻根系对Cd的阻控能力有助于降低南方稻区大米镉含量超标的风险。以水稻核心种质资源中的高Cd积累品种‘齐头白谷’和低Cd积累品种‘27760’的幼苗和离体叶片为材料,对其Cd吸收转运特性和耐镉能力进行了比较研究。结果表明,根系细胞壁和原生质体的Cd吸收动力学特征都符合米氏方程,‘齐头白谷’的Cd最大吸收速率F_(max)显著大于‘27760’,Km值无显著差异。当根际环境中的Cd浓度高于0.89μmol·L^(-1)时,‘齐头白谷’的细胞壁和原生质体的Cd积累速率显著高于‘27760’。地上部细胞壁和原生质体的Cd吸收速率与根系可溶性组分中的Cd浓度呈显著的线性正相关。当根系可溶性组分中的Cd浓度相近时,‘齐头白谷’地上部细胞壁和原生质体的Cd积累速率显著高于‘27760’。在0.89~8.9μmol·L^(-1)的Cd溶液中,‘齐头白谷’离体叶片的失绿速度明显低于‘27760’。‘齐头白谷’具有耐Cd能力强、Cd积累速率快和转运效率高的特点。水稻离体叶片的耐Cd能力和幼苗根系的Cd积累能力以及幼苗的Cd转运能力高度相关,它们都可作为快速鉴定低Cd积累品种的生理指标。

The uptake capability of cadmium（ Cd） in roots and Cd transport efficiency from roots to shoots are the key factors affecting Cd accumulation in rice shoots. Increasing the inhibition of Cd uptake by rice roots is in advan-tage of reducing the risk to people health posed by high Cd content in rice grains in southern China. Here,seedlings from the core germplasms with high-Cd-accumulation,i. e.,‘Qitoubaigu ＇,and low-Cd-accumulation,i. e.,‘27760＇,as well as their detached leaves were used to study the characteristics of Cd uptake and tolerance to Cd toxicity. Experimental results indicated that the Cd absorption kinetic characteristics of root cell wall and protoplast were well described with Michaelis-Menten equations. The maximum Cd absorption rate Fm axof ‘Qitoubaigu ＇was significantly greater than that of ‘27760＇,while Kmvalues were not significantly different between two rice varieties. The Cd accumulation rates in cell wall and protoplast of ‘Qitoubaigu ＇were significantly higher than that of‘27760＇when the concentration of Cd in rhizosphere environment was over 0.89 μmol·L^-1. The Cd absorption rates in cell walls and protoplasts of aboveground parts were linearly increased with the Cd concentrations in soluble fractions of root cells. ‘Qitoubaigu＇showed significantly higher Cd accumulation rates in cell walls and protoplasts of aboveground parts than ‘27760＇when their Cd concentrations in soluble fractions of root cells were same. The detached leaves of ‘Qitoubaigu＇displayed lower chlorophyll decreasing rate than that of ‘27760＇when the detached leaves were maintained in Cd concentrations varied from 0.89 μmol·L^-1to 8.9 μmol·L^-1. ‘Qitoubaigu ＇had strong tolerance to Cd,fast Cd accumulation rate and high transport efficiency. The Cd tolerance of rice detached leaves was closely associated with the Cd accumulation in seedlings roots and Cd transport efficiency from roots to shoots.These physiological traits can be used for fast identification of low-Cd-accumulation variety.