Cd-K双重处理对水稻幼苗生长和Cd吸收转运的影响及相关转运通道分析

以水稻( Oryza sativa Linn.)高 Cd 积累品种‘T 优705’(‘T You 705’)和低 Cd 积累品种‘湘早籼24’(‘Xiangzaoxian 24’)为实验材料,采用水培法对不同浓度Cd(0.0和2.7μmol·L-1 Cd)和K(0、30和60 mmol·L-1 K)处理条件下2个品种幼苗的相对生长量、根系和地上部的Cd含量及其亚细胞分布特征进行了比较,并分析了添加离子通道活性抑制剂TEA和LaCl3后幼苗根系和地上部的Cd和K含量；在此基础上,比较了NSCCs(非选择性阳离子通道)和K专性通道对2个品种幼苗根系和地上部Cd和K吸收贡献率的影响。结果表明：与Cd单一处理组(2.7μmol·L-1 Cd)相比, Cd-K双重处理组(2.7μmol·L-1 Cd-30 mmol·L-1 K和2.7μmol·L-1 Cd-60 mmol·L-1 K)2个品种幼苗的相对生长量显著提高,而幼苗根系和地上部的Cd含量显著下降；随K浓度的提高,2个品种幼苗根系细胞壁和细胞液中的Cd含量显著下降,但细胞壁中Cd含量的分配比例增大而细胞液中Cd含量的分配比例则减小。在含2.7μmol·L-1 Cd和30 mmol·L-1 K的培养液中分别添加5 mmol·L-1 TEA或0.2 mmol·L-1 LaCl3后,2个品种幼苗根系和地上部的Cd和K含量均显著下降,其中,LaCl3处理组的根系Cd含量降幅高于TEA处理组,但LaCl3处理组的根系K含量降幅则低于TEA组。 NSCCs对品种‘T优705’幼苗根系和地上部Cd吸收的贡献率显著低于品种‘湘早籼24’幼苗,而K专性通道对品种‘T优705’幼苗根系K吸收和地上部Cd吸收的贡献率则显著低于品种‘湘早籼24’幼苗。研究结果显示：添加外源K可缓解Cd对水稻幼苗生长的抑制作用,并通过提高细胞壁与Cd的结合能力来降低细胞液中Cd的积累,以此减弱幼苗对Cd的吸收和转运能力；幼苗体内的K和Cd均可通过K专性通道和NSCCs转运,其中,K吸收和转运主要通过K专性通道完成,而Cd吸收和转运主要通过NSCCs完成。此外,品种‘T优705’可能具有多种离子通道参与Cd的吸收和转运,而品种‘湘早籼24’主要依赖NSCCs参与Cd的吸收和转运,且后者对K的吸收和积累强于前者。

Effect of Cd-K double treatment on growth and Cd absorption and transport of Oryza sativa seedling and related transport channel analysis

Taking high-Cd-accumulation cultivar ‘T You 705 ’ and low-Cd-accumulation cultivar‘Xiangzaoxian 24’ of Oryza sativa Linn. as experimental materials, relative growth amount, Cd content and its subcellular distribution characteristics in root and above-ground part of two cultivar seedlingsunder treatment conditions of Cd (0. 0 and 2. 7 μmol·L-1 Cd) and K (0, 30 and 60 mmol·L-1 K) with different concentrations were compared by hydroponics, and Cd and K contents in root and above-ground part of seedling after added ion channel activity inhibitor TEA and LaCl3 were analyzed. On this basis, effects of NSCCs ( nonselective cation channels) and K specific channel on contribution rate to Cd and K absorption of root and above-ground part of two cultivar seedlings were compared. The results show that compared with single Cd treatment group ( 2 . 7 μmol · L-1 Cd ) , relative growth amount of two cultivar seedlings in Cd-K double treatment groups (2. 7 μmol·L-1 Cd-30 mmol·L-1 K and 2. 7μmol·L-1 Cd-60 mmol·L-1 K) increases significantly, while Cd content in root and above-ground part of seedling decreases significantly. With increasing of K concentration, Cd content in cell wall and cell sap of root of two cultivar seedlings decreases significantly, but allocation proportion of Cd content in cell wall increases, while that in cell sap decreases. After added 5 mmol·L-1 TEA or 0. 2 mmol·L-1 LaCl3 in culture solution containing 2. 7 μmol·L-1 Cd and 30 mmol·L-1 K, respectively, Cd and K contents in root and above-ground part of two cultivar seedling decrease significantly, in which, decreasing range of Cd content in root in LaCl3 treatment group is higher than that in TEA treatment group, but decreasing range of K content in root in LaCl3 treatment group is lower than that in TEA treatment group. Contribution rate of NSCCs to Cd absorption of root and above-ground part of cultivar ‘T You 705 ’ seedling is significantly lower than that of cultivar ‘Xiangzaoxian 24’seedling, while contribution rate of K specific channel to K absorption of root and to Cd absorption of above-ground part of cultivar ‘T You 705’ seedling is significantly lower than that of cultivar‘Xiangzaoxian 24’ seedling. It is suggested that adding exogenous K can relieve inhibition of Cd to growth of O. sativa seedling, and through increasing binding ability of cell wall with Cd to decrease Cd accumulation in cell sap, so as to reduce absorption and transport capacities of seedling to Cd. K and Cd in seedling both can be transported by K specific channel and NSCCs, in which, K absorption and transport is mainly finished by K specific channel, while Cd absorption and transport is mainly finished by NSCCs. In addition, cultivar ‘T You 705’ may possess many ion channels to participate Cd absorption and transport, while cultivar ‘Xiangzaoxian 24 ’ mainly depends on NSCCs to participate Cd absorption and transport, and K absorption and accumulation of the latter are stronger than those of the former.