Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China.
College of Resources and Environment, Hunan Agricultural University, Changsha, China.
Sci Total Environ. 2019 Oct 15;687:790-799. doi: 10.1016/j.scitotenv.2019.06.044. Epub 2019 Jun 12.
Understanding the mechanisms on how water management can minimize the concentrations of heavy metals in rice grains is important. Two water managements were concerned in our studies, including continuously flooding and alternate wetting and drying (AWD). Compared to AWD, a continuously flooded culture reduces the concentration of cadmium and other metals in the rice grains by reducing the root-to-shoot translocation and the availability of metals in rhizosphere. In a flooded environment, the rice rhizosphere was characterized by an increased soil pH, reduced fluorescein diacetate (FDA) activity, and lower metal bioavailability. In addition, flooding significantly decreased the iron plaque on the root surface and reduced the affinity for metals in rhizosphere. Water managements significantly changed soil microbial diversity, especially the proportion of anaerobic bacteria, including the iron-reducing bacteria Latescibacteria, Desulfuromonadales, and Geobacteraceae. Interestingly, these bacteria exhibited a significant correlation with cadmium that was adsorbed on the root. This study revealed that continuously flooded culture is a valuable strategy for minimizing heavy metal accumulation in rice grains. By increasing the abundance of unique bacterial community, iron plaque formation and the affinity of metals in rhizosphere were reduced, and the uptake and accumulation of heavy metals in rice plants was finally mitigated.
了解水分管理如何将重金属在水稻籽粒中的浓度最小化的机制非常重要。我们的研究中关注了两种水分管理方式，包括持续淹水和间歇性淹水与落干（AWD）。与 AWD 相比，连续淹水通过减少根到茎的转运和根际中金属的可用性，降低了镉和其他金属在水稻籽粒中的浓度。在淹水的环境中，水稻根际的特点是土壤 pH 值升高、荧光素二乙酸（FDA）活性降低以及金属生物利用度降低。此外，淹水还显著减少了根表面的铁帽，并降低了根际对金属的亲和力。水分管理显著改变了土壤微生物多样性，特别是厌氧细菌的比例，包括铁还原菌 Latescibacteria、脱硫单胞菌目和地杆菌科。有趣的是，这些细菌与吸附在根部的镉表现出显著的相关性。这项研究表明，连续淹水是减少水稻籽粒中重金属积累的一种有价值的策略。通过增加独特细菌群落的丰度，减少了铁帽的形成和根际中金属的亲和力，最终减轻了水稻植株对重金属的吸收和积累。
