土壤—植物系统硒的迁移转化机制研究进展

Advance on Selenium Migration and Transformation Mechanism in Soil-plant Systems

元素硒是许多生物(包括土壤微生物,植物、动物和人类)机体必需的微量营养元素之一,而且对植物、动物和人具有双重生物效应。半个多世纪以来土壤—植物系统元素硒的迁移、转化和富集过程一直备受关注。土壤硒的存在形态包括可溶态硒、可交换态及碳酸盐结合态硒、铁锰氧化物结合态硒、有机物结合态硒和残渣态硒5种形态,其中可溶态硒和可交换态及碳酸盐结合态硒具生物有效性,有机物结合态硒随着有机质分解可转化为可溶态硒而成为土壤潜在有效硒源。不同植物硒含量水平取决于区域土壤有效硒含量和不同植物的硒吸收和富集水平。因此,土壤硒的生物有效性是决定食物链硒含量的关键,同时土壤有效硒通过调节根际环境和植物代谢过程提高植物抗逆性。土壤—植物系统元素硒的迁移和转化是一个复杂的生物地球化学过程,受地壳运动、母岩性质、气候、地貌、土壤环境(物理、化学和微生物活动)条件、土壤硒含量及其化学性质、植物种类及其生理习性、田间管理过程等因素的耦合作用影响。为充分合理利用土壤硒资源,将来应加强植物体内,尤其是主要粮食作物、蔬菜、果树和地道药材叶片、果实中硒迁移、转化和富集研究,为缺硒地区硒的生物强化、富硒地区农作物种植选择和居民食品选择及其风险评价提供基础数据。

Selenium(Se)is an essential micronutrient for many organisms(including soil microorganisms,plants,animals,and humans),and has dual biological effects on plants,animals,and humans.The migration,transformation,and enrichment of Se in soil-plant systems have attracted considerable attention for more than half a century.There are five forms of soil Se:soluble Se(SOL-Se),exchangeable carbonate-bound Se(EXC-Se),iron-manganese oxide-bound Se(FMO-Se),organic matter-bound Se(OM-Se),and residual Se(RES-Se),of which SOL-Se and EXC-Se are characterized by bioavailability.OM-Se can be converted into soluble Se by the decomposition of organic matter and is a potentially effective selenium source in soil.The Se content of different plants depends on the soil-available Se content and the Se absorption and enrichment levels of different plants.Therefore,the bioavailability of soil Se plays a critical role in determining the Se content in the food chain,and soil-available Se can improve plant stress resistance by regulating the rhizosphere environment and metabolic processes.Soil-plant system Se migration is a complex biogeochemical process that is dominated by coupled crustal movement,parent rock properties,climate,geomorphology,soil environment(physico-chemical properties and microbial activity)conditions,soil Se content and chemical properties,plant species and biological habits,and field management processes.For the rational utilization of soil Se resources,research needs to focus on Se migration,transformation,and enrichment in plants,especially the main food crops,vegetables,fruit trees,and Authentic Chinese herbs.This study provides basic data for Se biofortification in Se-deficient areas,and crop selection,food selection,and risk assessment in Se-rich areas.