《植物生理学报》 2016, 52(1): 125-133
通信作者：汤继华；E-mail: Tangjihua1@163.com; liuzhongqi508@163.com
摘 要：
在人工气候室水培条件下, 对19份水稻核心种质和5份水稻品种的幼苗耐镉特性和镉离子(Cd2+)吸收动力学特性进行了研究, 试验结果表明, 水稻幼苗的根系生物量和镉含量都存在广泛的遗传差异。在0~4.45 μmol•L-1的外界环境中, 不同基因型水稻幼苗根系的Cd2+吸收动力学特征都符合米氏方程, 但特征值Fmax和Km在基因型间有明显差异。Fmax最小为37.8nmol•g-1 (DW)•h-1, 最大为87.5 nmol•g-1 (DW)•h-1。当根系Fmax值高于55.5 nmol•g-1 (DW)•h-1时, 地上部的Cd2+积累动力学特征也符合米氏方程; 但当根系Fmax值小于50.8 nmol•g-1 (DW)•h-1时, 地上部的Cd2+积累动力学特征却符合线性方程, 此时截距a与Km值有密切关系, Km值为0.5~1.3 μmol•L-1时a为正, Km值为2.9~3.9 μmol•L-1时a为负。在4.45 μmol•L-1的Cd胁迫环境下, 根系和地上部的Cd积累量与米氏方程的Fmax和线性方程的斜率b表现出显著的线性相关。Cd转运效率既与环境中的Cd2+浓度有关, 也与地上部的Cd积累特性有关。地上部Cd积累特性符合线性方程的水稻品种, 其转运效率随着环境中Cd2+浓度的增加而持续升高, 而地上部Cd积累特性符合米氏方程的水稻品种, 其转运效率往往随着环境中Cd2+浓度的升高而降低。这些结果说明水稻根系和地上部对Cd2+的吸收存在不同的阻控机制, Cd2+吸收特性和转运效率在基因型间有丰富的遗传多样性。根系Fmax小且地上部线性方程斜率b也小的基因型多为根系Cd积累量低和Cd转运率低的低积累种质资源。关键词：水稻; 吸收动力学; 镉(Cd); 转运效率; 遗传多样性
收稿：2015-10-22 修定：2015-12-28
资助：中国农科院科技创新工程项目(2015-cxgc-lzq)和公益性行业(农业)科研专项(201403015)。
Corresponding author: TANG Ji-Hua; E-mail: Tangjihua1@163.com; liuzhongqi508@163.com
Abstract:
24 rice (Oryza sativa ssp. indica) cultivars including 19 core germplasms and 5 modern cultivars were used to study the characteristics of tolerance and absorption kinetics of rice seedlings to cadmium under hydroponic conditions in phytotron. The results showed that there were extensive genetic differences in root biomass and cadmium content of rice seedlings. The Cd2+ absorption kinetic characteristics of roots in rice seedlings from different genotypes was well described with Michaelis-Menten equation when Cd2+ concentration around root varied from 0 μmol•L-1 to 4.45 μmol•L-1, but Cd2+ uptake kinetic parameters Fmax and Km among genotypes had obvious differences. Fmax varied from 37.8 nmol•g-1 (DW)•h-1 to 87.5 nmol•g-1 (DW)•h-1. The above-ground Cd2+ accumulation kinetic characteristics was also well fitted by Michaelis-Menten equation when the root Fmax was higher than 55.5 nmol•g-1 (DW)•h-1. However, the above-ground Cd2+ accumulation kinetic characteristics was well fitted by a linear equation when Fmax was lower than 50.8 nmol•g-1 (DW)•h-1. There was a close relationship between intercept a and Km value at this time. The intercept a of above-ground was positive when Km varied from 0.5 μmol•L-1 to 1.3 μmol•L-1 but negative when Km varied from 2.9 μmol•L-1 to 3.9 μmol•L-1. When Cd2+ concentration around root was 4.45 μmol•L-1, the Cd accumulation in root and above-ground was significantly and linearly correlated with the Fmax of Michaelis-Menten equation as well as with the slope b of linear equation. Cd transport efficiency was associated with Cd2+ concentration in environment, and also with Cd accumulation characteristics of above-ground. The Cd transport efficiency of rice varieties was rising with the increase of Cd2+ concentration in the environment when their above-ground Cd2+ absorption kinetic characteristics was well fitted with linear equation, but increased first and then decreased when their above-ground Cd2+ absorption kinetic characteristics was accorded with Michaelis-Menten equation. These results suggest that there are different control mechanisms in root and above-ground for Cd absorption. Cd2+ absorption features and transport efficiency have abundant genetic diversity among genotypes. Most rice core germplasms with small root Fmax and slop b in the linear equation of above ground Cd2+ absorption are the excellent genotypes with both low Cd accumulation in root and Cd transport efficiency from root to shoot.Key words: rice; absorption kinetics; cadmium; transport efficiency; genetic diversity
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