不同水分管理对水稻土硒转化及水稻硒积累的影响机制

Selenium plays a very important role in maintaining the immune system of human body health and reducing the risk of cancer. The transformation of selenium in soil plant system plays a key role in the regulation of selenium in the food chain. Water management can affect the environmental chemical behavior of selenium in soil and the absorption and accumulation of selenium in plants. However, it is not clear that the mechanism of selenium speciation transformation and bioavailability of different water management in paddy soils is not clear at present. This project first used the empirical simulation test, the transformation between pH and Eh and clear paddy soil selenium speciation, on this basis, clear under different water management of selenium in soil rice system spatial chemical conversion mechanism, respectively from the angle of time (at different growth stages of rice) and space angle (bulk soil and Rhizosphere soil and iron plaque on root surface and pore water) of soil selenium speciation chemical conversion mechanism; and reveal the different water management transformation mechanism of selenium in paddy soil microorganism; carry out the relationship between the N-Fe-Se three in the rhizosphere of rice and the relationship between the accumulation of rice and selenium; clarify different water management effects of selenium to possible physiological mechanism of shoots the. Through the above research, this study reveals the mechanism of water management on the accumulation of selenium in rice, and has important theoretical and practical significance for the effective regulation of selenium from rice field to the food chain of agricultural products.

硒对于维持人体健康的免疫体系和减少癌症风险有非常重要的作用，土壤-植物系统中硒的迁移转化对低硒地区食物链中硒的调节起着非常关键的作用。稻田水分管理可能通过影响土壤Eh和pH而改变硒形态和生物有效性，目前有关水分管理对水稻土硒形态转化及生物有效性机制尚不明确。项目首先采用实证模拟试验，明确pH和Eh与水稻土硒形态转化的关系。在此基础上，明确不同水分管理下硒在土壤-水稻系统中时空化学转化机制，分别从时间角度（水稻不同生育阶段）和空间角度（本体土壤、根际土壤、根表铁膜、孔隙水）揭示土壤硒形态化学转化机制；同时阐明不同水分管理对稻田土壤硒微生物转化机制；深入开展N-Fe-Se三者在水稻根际间的相互关系与水稻硒积累的关系；阐明不同水分管理影响硒向地上部及籽粒转运的生理机制，最终揭示水分管理对水稻土硒转化及水稻硒积累的影响机制，为生产中从源头上有效调控硒从稻田向农产品食物链传递具有重要理论现实意义。

硒对于维持人体健康的免疫体系和减少癌症风险有非常重要的作用，土壤-植物系统中硒的迁移转化对低硒地区食物链中硒的调节起着非常关键的作用。水分能影响土壤中硒的环境化学行为和植物对硒的吸收积累。采用控制pH和Eh进行模拟试验，明确了土壤pH和Eh共同决定着水稻土中多个重要元素的氧化还原体系方向和次序，为土壤元素特别是硒元素转化和高效利用奠定了理论基础。干湿交替灌溉和湿润处理较常规灌溉可以显著提高籽粒硒含量，其原因是增加了稻田土壤有效态硒含量，而且长期淹水会促进Se向残渣态转化，不同水分管理模式对稻田土壤中有机结合态和铁膜氧化物结合态的影响较小，揭示了水分管理影响水稻籽粒硒积累的土壤化学机制。干湿交替和好氧灌溉中变形菌门的丰富度明显高于淹水灌溉。从纲水平看，Gammaproteobacteria的丰度与土壤有效硒含量呈正相关，故Gammaproteobacteria丰度的增加可能是土壤硒生物有效性增加的另一个重要原因，初步明确了水分管理对稻田土壤硒微生物转化机制。施用高碳氮比有机物料+干湿交替能显著提高土壤有效硒浓度，有机物矿化释放有机酸活化土壤难溶性硒。可能与有机物料分解产生多元酸（如柠檬酸）对土壤硒产生强烈的活化效应以及微生物的作用有关。氮肥能够调节铁还原细菌区系，促进Fe(Ⅲ)还原。铁还原菌可利用铁氧化物中的铁（即铁氧化物的异化还原），使水稻土中铁氧化物分解进而造成氧化物中硒的释放，增加了水稻硒的生物有效性，初步揭示N-Fe-Se三者在水稻根际间的相互关系及与水稻硒积累的关系。该研究初步明确了稻田水分调节影响稻米硒积累的机制，为应用遗传育种和农艺措施手段适当提高稻米中硒积累量，实现我国稻米生产的绿色、优质、高效提供理论及实践依据。