土壤-水稻系统中锑的迁移转化机制研究

Antimony (Sb) is a toxic carcinogenic element. In China soil, water, and agricultural products have been seriously polluted by Sb in some areas due to some natural and artificial factors.High levels of Sb in environment can decrease the yields of paddy-rice and threaten the health of humans.Previous studies have shown that Sb is not an essential element to plants, but it can be accumulated by plants. Excess Sb can produce damages to plants. However, some questions are still left to be resolved, for example, which pathway plants will choose to take up Sb, passive or active? In this study, we attempt to investigate the mechanisms on Sb uptake, migration of Sb from soil to paddy rice, speciation transformation of Sb in soil and tissues of paddy rice, toxicity and detoxification of different Sb species in paddy-rice. Several experiments will be carried out, including: (1)the effects of water management and fertilizers of P,Ca and Fe on the concentration of different Sb speciations in soil and tissues of paddy rice, the speciation transformation of Sb in soil, the some characteristics of microbes in soil, the formation of iron plaque and its role in restraining Sb, the yield and the quality of rice.(2)the effects of transpiration and some additives (HgCl2 and Si) on the uptake of Sb(V) and Sb(III) in paddy-rice;(3) the effects of root cell wall components, root exudates, root morphology on the uptake of different Sb speciations; (4) the efficiency of paddy rice absorbing Sb from hydroponic solution and transferring Sb from roots to shoots, where the speciation changes of Sb will also be monitored; (5)the differences in effects of Sb(V) and Sb(III) on the growth and development of roots, photosynthesis, responses of antioxidants, contents of some low molecular weight substances, cell structure, and subcellular distribution of Sb. The seeds of paddy-rice gathered from Sb-polluted areas in Hunan province will be used in this study. Some advanced technologies will be applied, such as differential centrifugation separation technology, SEM/TEM technology in combination with energy spectrum analysis,high performance liquid chromatography, high performance liquid chromatography combined with inductively coupled plasma mass spectrometry and chromatography of ions. It is hoped that the results of this study will help people understand the mechanisms on the behaviors of different Sb species in plants,and realize the risks of Sb-pollution to environment and health of human beings, and make people give more concerns on Sb pollution in future.

锑(Sb)是一种致癌元素，我国部分地区水稻受到严重的Sb污染。以往的研究表明，Sb不是水稻必需营养元素，但水稻能富集Sb，过量的Sb对水稻产生毒害。迄今，有关Sb在土壤-水稻系统中的迁移、转化，及其影响因素等方面的研究比较缺乏。本项目以水稻为研究材料，利用扫描/透射电镜-能谱分析、电感耦合等离子质谱等技术，研究Sb从土壤向水稻迁移、转化的规律及其影响因素；重点研究土壤-水稻根系系统中Sb的迁移/转化与土壤微生物群落特征、水分、竞争(结合)离子、根系系统(铁膜，根系形态及细胞壁组分)之间的关系；不同形态Sb从根系向叶片迁移过程中，Sb的木质部转运效率及形态转化、Sb的细胞定位及毒性,以及蒸腾作用、吸收抑制剂在Sb转运过程中所起的作用。揭示Sb在土壤-水稻系统中的迁移、转化机理。其研究成果对于拓展Sb在植物体内行为机理的认识、保护受Sb污染的环境、降低Sb污染对人体健康的危害具有重要意义。

锑(Sb)在环境中普遍存在，水稻是我国重要粮食作物，也是易富集Sb的一种农作物。本研究通过一系列试验研究了不同形态Sb对水稻的毒害作用机制，不同形态Sb在水稻体内吸收、转运、形态转化及其影响因素。主要研究结果如下：.(1) 20 mg•L-1 Sb(III)抑制了根长、根体积、根表面积、根尖数和根分叉数；而20 mg•L-1 Sb(V)仅降低了水稻根面积、根直径和分叉数；Sb(III)增加了水稻根系粗根和中等根比例，降低了细根比例；而Sb(V)降低了粗根和中等根比例，增加了细根比例。.(2)Sb(III)处理下水稻吸收Sb的能力较Sb(V)处理时的强；水稻向地上部分转运Sb的能力较弱；Sb(III)处理下，水稻体内Sb的形态主要以Sb(III)为主；而Sb(V)处理下，水稻体内Sb的形态主要以Sb(V)为主。.(3)Sb(III)处理显著增加了水稻地上部分Mg、K、Ca、Fe、Cu、Zn的含量；而在Sb(V)处理下，仅10 mg•L-1处理浓度显著增加了大部分必需营养元素的含量。.(4)Sb(V)处理显著增加了水稻伤流液的数量，增加了伤流液中Fe、Cu的含量；而Sb(III)未显著影响伤流液的量，但部分处理水平显著增加了伤流液中Fe、Cu、Sb的含量；伤流液中Ca的含量在两种形态Sb处理下均降低。.(5)不同形态Sb处理下，细胞壁和细胞液均富集了绝大部分Sb。两种形态Sb均对水稻产生氧化胁迫；SOD和APX被不同形态Sb处理激活，而不同形态Sb处理大部分情况下均显著抑制POD活性。.(6)不同形态Sb处理下，水稻根系中果胶和木质素含量均显著增加，而半纤维素I和半纤维素II含量基本未增加；大部分情况下不同形态Sb处理均显著增加了根系分泌草酸的量，降低了甲酸和乙酸的分泌量。Sb(III)处理显著增加了根系脱落酸(ABA)的含量，而Sb(V)处理基本未显著影响根系ABA的含量；不同形态Sb处理对水杨酸(SA)含量基本未有显著影响。.(7)添加P未能表现出降低水稻糙米中As和Cd含量的能力；而添加Ca和Fe均能抑制水稻吸收As，特别是高剂量的Ca和Fe在一定程度上降低水稻稻米中Cd的含量。添加P、Ca和Fe处理一定程度提高了水稻其它部位对Sb的吸收，但可以降低糙米中Sb的含量。间歇灌溉能同时将糙米中的As、Sb和Cd含量维持在一个最佳的含量水平。