红壤稻田有效硅形态及其抑制水稻砷累积的化学机制

It has been received widespread attention that silicon could inhibit arsenic accumulation in rice, however, most of the researches are concentrated on the effect of silicon on plant arsenic uptake, or the related physiological mechanisms, few studies have been carried out on the geochemical mechanisms of silicon species in soil and its plant availability, which could reduce arsenic accumulation in rice. The present project is to study the relationship among silicon speciation, bioavailability and arsenic accumulation. Firstly, different types of red soil in southern China are collected, and the laboratory analysis will be conducted to determine the relationship between the species of silicate in red paddy soil, and its influencing factors, e.g., physiochemical characters, weathering index, which is to determine the key geochemical factors on soil Si bioavailability; Secondly, a pot experiment with different types of soils will be conducted to study the types of soil Si and the uptake and distribution in rice, by using the 30Si stable isotope in different development stage, and to analyze the effect of silicon types on As uptake and accumulation in rice, which are to ascertain the available Si types in plant Si uptake and As accumulation; Thirdly, a rhizobox experiment will be carried out to ascertain the key environmental factors affecting the transformation of Si types and As bioavailability in rhizosphere and bulk soils, and the relationship of the shoot Si combined chemical bond with XPS and As accumulation will also be analyzed, which are to illustrate the interactional mechanisms of the transformation of Si types in soil, Si bioavailability and As accumulation in rice.

硅对水稻砷吸收的抑制作用和相关生理机制研究已受到广泛关注，而对于硅酸盐形态转化及其生物有效性抑制水稻砷吸收积累的土壤化学机制研究鲜有报道。本项目针对华南红壤稻田有效硅形态与水稻硅吸收和砷积累的关系这一核心科学问题开展研究。选取不同母质类型发育的红壤，分析其土壤理化性状、风化系数等指标与土壤硅形态转化、有效硅含量的关系，明确影响土壤有效硅含量的关键地球化学因子；盆栽试验条件下，研究不同类型土壤硅酸盐形态与不同生育期水稻硅吸收和砷积累的关系，利用硅稳定性同位素示踪技术研究土壤硅酸盐形态与水稻硅、砷吸收分布的关系，确定影响水稻硅吸收和抑制砷累积的关键土壤硅形态以及植株硅、砷吸收的关键生育期；采用根箱实验，研究华南红壤稻田水稻根际/非根际土壤硅形态转化和砷有效性差异及影响因素，并分析水稻地上部硅含量和结合价态与砷累积分布的关系，阐明华南红壤稻田硅形态转化与植株硅有效性以及砷有效性的交互作用机制。

硅对水稻砷吸收的抑制作用和相关生理机制研究已受到广泛关注，而对于硅酸盐形态转化及其生物有效性抑制水稻砷吸收积累的土壤化学机制研究鲜有报道。本项目针对华南红壤稻田有效硅形态与水稻硅吸收和砷积累的关系这一核心科学问题开展研究。项目研究了华南红壤污染区不同提取态硅含量和植株有效性的关系，及其抑制水稻砷积累的土壤化学机制。研究发现土壤硅含量与植株根系和茎秆硅含量相关性显著，对结果的综合比较分析发现草酸-草酸铵态硅较为适合作为红壤区水稻硅营养的评价方法。而对水稻籽粒砷含量相关性分析发现，以柠檬酸提取态、草酸-草酸铵提取态以及DCB-Si对籽粒As的含量呈极显著的负相关关系，说明土壤硅含量能够显著抑制植株砷向籽粒中的转运。并分析了土壤理化性质对土壤硅形态及其有效性的影响，为矿区周边砷污染土壤治理提供了理论依据。在此基础上，并利用盆栽试验，研究了叶面喷硅对缓解水稻砷毒害的影响，揭示了硅营养添加降低了水稻砷的吸收和向地上部的转移，减轻了植株膜系统的损伤，并增强了水稻植株的抗氧化系统活性，初步揭示了硅抑制水稻砷累积和毒害的生理生化机制，并为大田水稻砷污染防治开辟了一条新的途径。