外源Cd在不同品种水稻组织中的细胞分布和化学形态特征研究

采用水培试验,以低镉(Cd)积累水稻品种‘D83A/R527’和高Cd积累水稻品种‘辐优838’为供试材料,设置3个Cd浓度(5μmol·L~(-1)、10μmol·L~(-1)、25μmol·L~(-1))处理,从Cd亚细胞及化学形态分布角度研究了不同基因型水稻品种的Cd积累特性,为探讨水稻对Cd的吸收积累生理机制提供科学依据。结果表明:(1)水稻‘D83A/R527’的根系和茎叶Cd含量及根系-茎叶转移系数均显著低于‘辐优838’(P0.05)。(2)两水稻根系各亚细胞组分中Cd含量表现为可溶部分(F3)细胞壁(F1)细胞器(F2),茎叶表现为细胞壁(F1)可溶部分(F3)细胞器(F2);‘D83A/R527’根系和茎叶细胞壁Cd的质量分数(36.76%~51.75%)高于‘辐优838’(31.29%~49.07%)。(3)两水稻品种Cd化学形态含量均表现为氯化钠提取态(F_(NaCl)-Cd)醋酸提取态(F_(HAc)-Cd)去离子水提取态(F_W-Cd)乙醇提取态(F_E-Cd)盐酸提取态(F_(HCl)-Cd);随Cd处理浓度的增加,‘D83A/R527’根系F_E-Cd和F_W-Cd(活性态Cd)质量分数逐渐下降(24.75%~18.34%),‘辐优838’活性态Cd逐渐上升(27.18%~28.68%),茎叶F_(HAc)-Cd和F_(HCl)-Cd(惰性态Cd)质量分数(32.41%~38.98%)逐渐上升且高于‘辐优838’(28.44%~31.22%),‘D83A/R527’根系和茎叶F_(NaCl)-Cd质量分数(32.71%~51.17%)均高于‘辐优838’(32.14%~47.63%)。综上,‘D83A/R527’水稻幼苗Cd积累量低;与‘辐优838’相比,‘D83A/R527’水稻幼苗根系和茎叶细胞壁质量分数较高,"活性态"Cd质量分数较低,"惰性态"Cd则更高,表明‘D83A/R527’水稻对Cd有更强的固持能力。

Histocyte distribution and cadmium forms in different rice cultivar seedlings with exogenous cadmium supply

A hydroponic experiment was conducted to study cadmium (Cd) accumulation characteristics in different rice genotypes — low Cd accumulation ('D83A/R527') and high Cd accumulation ('Fuyou838'). The subcellular distribution and chemical forms of Cd in the root and shoot of different rice genotypes were investigated after exposure to Cd concentrations of 5μmol·L-1, 10μmol·L-1 and 25μmol·L-1. The aim of the study was to explore subcellular distribution and chemical forms change of Cd in rice to provide refer-ence for research on Cd absorption mechanisms of rice. The results showed that: 1) the concentrations of Cd in roots and shoots and the transfer rate in 'D83A/R527' were significantly lower than those in 'Fuyou838' (P< 0.05). 2) The contents of Cd in subcellular fractions of two rice cultivars were in the orders of soluble fraction (F3) > cell wall (F1) > organelle (F2) in roots, but cell wall (F1) > soluble fraction (F3) > organelle (F2) in shoots. The proportions of Cd in cell walls (36.76%-51.75%) in both roots and shoots of 'D83A/R527' were higher than those in 'Fuyou838' (31.29%-49.07%). 3) The order of contents of Cd chemical forms revealed by different processing methods was sodium chloride extraction state (FNaCl-Cd) > acetic acid extractable state (FHAc-Cd) > deionized water extraction (FW-Cd) > ethanol extracted state (FE-Cd) > HCl extractable state (FHCl-Cd) in both cultivars. When Cd concentra-tion increased, the proportions of FE-Cd and FW-Cd (active forms) from root of 'D83A/R527' declined gradually (24.75%-18.34%), but increased gradually in 'Fuyou838' (27.18%-28.68%). The percentages of FHAC-Cd and FHCl-Cd (inertia forms) in shoot of 'D83A/R527' (32.41%-38.98%) were higher than those in 'Fuyou838' (28.44%-31.22%). The proportions of FNaCl-Cd in both root and shoot of 'D83A/R527' (32.71%-51.17%) were higher than those in 'Fuyou838' (32.14%-47.63%). In short, Cd accumulation in 'D83A/R527' was lower than that in 'Fuyou838'. Then cell wall mass fractions of both root and shoot systems were higher in 'D83A/R527' than that in 'Fuyou838'. Also there was lower accumulation of active forms of Cd and higher accumulation of inertia forms of Cd in 'D83A/R527' than that in 'Fuyou838'. Therefore, rice cultivar 'D83A/R527' had a better Cd fixation capacity than 'Fuyou838'.