• ISSN 1008-505X
  • CN 11-3996/S
李芹, 张曼, 张锡洲, 余海英, 李廷轩. 水稻镉安全材料分蘖期根部镉积累分布特征[J]. 植物营养与肥料学报, 2019, 25(3): 443-452. DOI: 10.11674/zwyf.18102
引用本文: 李芹, 张曼, 张锡洲, 余海英, 李廷轩. 水稻镉安全材料分蘖期根部镉积累分布特征[J]. 植物营养与肥料学报, 2019, 25(3): 443-452. DOI: 10.11674/zwyf.18102
LI Qin, ZHANG Man, ZHANG Xi-zhou, YU Hai-ying, LI Ting-xuan. Accumulation and distribution characteristics of Cd in roots of cadmium-safe rice line at tillering stage[J]. Journal of Plant Nutrition and Fertilizers, 2019, 25(3): 443-452. DOI: 10.11674/zwyf.18102
Citation: LI Qin, ZHANG Man, ZHANG Xi-zhou, YU Hai-ying, LI Ting-xuan. Accumulation and distribution characteristics of Cd in roots of cadmium-safe rice line at tillering stage[J]. Journal of Plant Nutrition and Fertilizers, 2019, 25(3): 443-452. DOI: 10.11674/zwyf.18102

水稻镉安全材料分蘖期根部镉积累分布特征

Accumulation and distribution characteristics of Cd in roots of cadmium-safe rice line at tillering stage

  • 摘要:
    目的 镉 (Cd) 低积累作物的培育和应用是减少土壤中Cd通过食物链危害人体健康的重要途径。通过研究Cd处理下水稻分蘖期根部Cd的积累分布特征,揭示水稻Cd安全材料根部Cd的固持机理,为水稻Cd安全品种的培育提供理论依据。
    方法 以水稻Cd安全材料D62B为供试材料,普通材料Luhui17为对照,进行水培试验。水稻秧苗于三叶一心时移栽至盆中 (40 cm × 60 cm × 15 cm),以CdCl2·2.5H2O加入营养液,设0 (CK)、0.5 (Cd0.5)、1.0 (Cd1)、2.0 (Cd2) mg/L 4个Cd浓度处理,30天后收获,分为根和地上部测定其Cd全量。采用化学试剂逐步提取法和差速离心法分别测定根部Cd化学形态和亚细胞分布特征,并进一步结合细胞壁多糖,研究其对Cd的响应特征。
    结果 1) Cd处理下D62B各部位Cd含量显著低于Luhui17,转移系数较小,其根部Cd向地上部转移较少。2) 随Cd处理浓度升高D62B根部水提取态Cd分配比例降低,盐酸提取态Cd、残渣态Cd分配比例升高,Cd移动性减弱。D62B根部Cd以氯化钠提取态为主 (48.9%~52.1%),高浓度Cd处理 (2.0 mg/L) 下其分配比例是Luhui17的1.11倍,水提取态是Luhui17的82.3%,其根中Cd的移动性弱于普通材料。3) D62B根部Cd主要分布于可溶部分和细胞壁,其中细胞壁Cd分配比例为38.6%~41.8%,高于Luhui17。随Cd处理浓度升高,D62B根细胞壁Cd分配比例降幅小于Luhui17,其细胞壁对Cd的固持作用有限但强于普通材料。4) D62B根细胞壁半纤维素1的Cd含量是果胶的7.74~8.40倍,Cd主要与细胞壁中半纤维素1结合。半纤维素1 Cd含量随Cd处理浓度升高而显著增加,2.0 mg/L Cd处理下D62B和Luhui17半纤维素1单位总糖Cd结合量较1.0 mg/L Cd处理分别增加32.6%、11.2%,D62B根细胞壁半纤维素1的Cd结合能力强于Luhui17。
    结论 水稻Cd安全材料D62B各部位Cd含量低于Luhui17,其转移系数较小。D62B根中Cd主要为氯化钠提取态,随Cd处理浓度升高,根部Cd向移动性较弱的化学形态转化。D62B根细胞壁中Cd主要与半纤维素1结合,由于其Cd结合能力较强,D62B根细胞壁对Cd的固持作用强于普通材料。因此,D62B对Cd的转移能力弱于普通材料,是其籽粒Cd安全的重要原因。

     

    Abstract:
    Objectives Cultivation of low Cd accumulation cultivars is an effective measure to minimize Cd influx into the human food chain. The mechanism of Cd immobilization in the roots of the cadmium-safe rice lines were studied in this paper.
    Methods A hydroponic experiment was conducted using a cadmium-safe rice line (D62B) and a common rice line (Luhuil7) as the comparing material. The rice seedlings of 3-leaf-1-sprout stage were cultured in nutrient solution for a week, then exposed to solution of Cd at 0 (CK), 0.5 (Cd 0.5), 1 (Cd 1) and 2 (Cd 2) mg/L supplying with CdCl2·2.5H2O for 30 days. The plants were harvested and divided into roots and shoots to measure the Cd content, and the chemical forms and subcellular distribution of Cd in roots were analyzed, and the modifications of cell wall polysaccharides to Cd of roots cell wall were discussed.
    Results Compared with Luhui17, D62B showed a lower Cd content in different parts, smaller transfer factor, and less Cd translocation from roots to shoots. Besides the decrease of the proportion of Cd extracted by d-H2O in roots of two rice lines, the proportion of Cd extracted by 0.6 mg/L HCl and Cd in the residue exhibited an increasing trend with increasing Cd concentration in the solution, indicating that the mobility and activity of Cd in roots of two rice lines decreased with Cd treatments. Among different chemical forms of Cd in roots of D62B, the Cd extracted by 1 mol/L NaCl accounted for the largest part (48.9%−52.1%). Furthermore, its proportion was 1.11 times of that of Luhui17, while those extracted by d-H2O were lower (82.3%) at 2.0 mg/L Cd treatment, indicating that the mobility and activity of Cd in roots of D62B were much lower than those of Luhui17. The vast majority of Cd was in soluble fraction and in the cell wall of the roots. The Cd in the roots cell wall of D62B was 38.6%−41.8%, higher than that of Luhui17. With increasing Cd content, the proportion of Cd in roots cell wall decreased, but D62B showed a greater capacity than Luhui17 to attain Cd within cell wall with a limit. As the hemicellulose 1 is the major site for Cd storage in roots cell wall, the Cd content in hemicellulose 1 of roots cell wall was 7.74−8.40 times that in pectin of D62B. The Cd content in hemicellulose 1 of two rice lines significantly increased with increasing Cd concentrations. The amount of Cd in polysaccharide of hemicellulose 1 of D62B and Luhui17 increased by 32.6% and 11.2%, respectively, at 2.0 mg/L Cd treatment compared to those at 1.0 mg/L Cd treatment. Furthermore, the total polysaccharide content in hemicellulose 1 as well as the Cd content of roots cell wall increased with the increase of Cd concentration, suggesting that the increase in hemicellulose 1 contributed greatly to the fixation of Cd2+ in the cell wall.
    Conclusions The cadmium-safe rice line designated D62B showed lower Cd content in plant and smaller transfer factor than those of Luhui17. Cd extracted by 1 mol/L NaCl was the major form in roots of D62B. Increasing Cd concentration resulted in conversion of Cd to less mobile forms. Cd in roots cell wall was mainly fixed by hemicellulose 1, and D62B showed a stronger fixation than Luhui17. The stronger capacity of cell wall of D62B to retain Cd was associated with fixation of hemicellulose 1. Cd in the immobile form and immobilization in hemicellulose 1 of roots cell wall of cadmium-safe rice line restrains the translocation of Cd from roots to shoots, which is a major mechanism that differentiate the rice lines the in governing the accumulation of Cd in grains.

     

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