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通过水稻根铁斑可视化和量化碳“生锈汇”:机制、功能和全球意义。

Visualization and quantification of carbon "rusty sink" by rice root iron plaque: Mechanisms, functions, and global implications.

机构信息

Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, China.

State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Ningbo, China.

出版信息

Glob Chang Biol. 2022 Nov;28(22):6711-6727. doi: 10.1111/gcb.16372. Epub 2022 Aug 19.

Abstract

Paddies contain 78% higher organic carbon (C) stocks than adjacent upland soils, and iron (Fe) plaque formation on rice roots is one of the mechanisms that traps C. The process sequence, extent and global relevance of this C stabilization mechanism under oxic/anoxic conditions remains unclear. We quantified and localized the contribution of Fe plaque to organic matter stabilization in a microoxic area (rice rhizosphere) and evaluated roles of this C trap for global C sequestration in paddy soils. Visualization and localization of pH by imaging with planar optodes, enzyme activities by zymography, and root exudation by C imaging, as well as upscale modeling enabled linkage of three groups of rhizosphere processes that are responsible for C stabilization from the micro- (root) to the macro- (ecosystem) levels. The C activity in soil (reflecting stabilization of rhizodeposits) with Fe addition was 1.4-1.5 times higher than that in the control and phosphate addition soils. Perfect co-localization of the hotspots of β-glucosidase activity (by zymography) with root exudation ( C) showed that labile C and high enzyme activities were localized within Fe plaques. Fe addition to soil and its microbial oxidation to Fe by radial oxygen release from rice roots increased Fe plaque (Fe ) formation by 1.7-2.5 times. The C amounts trapped by Fe plaque increased by 1.1 times after Fe addition. Therefore, Fe plaque formed from amorphous and complex Fe (oxyhydr)oxides on the root surface act as a "rusty sink" for organic matter. Considering the area of coverage of paddy soils globally, upscaling by model revealed the radial oxygen loss from roots and bacterial Fe oxidation may trap up to 130 Mg C in Fe plaques per rice season. This represents an important annual surplus of new and stable C to the existing C pool under long-term rice cropping.

摘要

稻田土壤中的有机碳(C)储量比相邻旱地土壤高 78%,水稻根表形成的铁(Fe)斑是固定 C 的机制之一。在有氧/缺氧条件下,这种 C 稳定机制的过程顺序、程度和全球相关性尚不清楚。我们在微氧区(水稻根际)量化和定位了 Fe 斑对有机质稳定的贡献,并评估了这种 C 陷阱在稻田土壤中对全球碳封存的作用。通过平面光学位成像可视化和定位 pH 值、通过同工酶图谱定位酶活性、通过 14C 成像定位根分泌物,以及通过上推模型将负责从微观(根)到宏观(生态系统)水平稳定 C 的三组根际过程联系起来。与对照和磷酸盐添加土壤相比,添加 Fe 后土壤中 14C 活性(反映根分泌物的稳定)提高了 1.4-1.5 倍。β-葡萄糖苷酶活性(同工酶图谱)与根分泌物(14C)的热点完全共定位表明,易位 C 和高酶活性定位于 Fe 斑内。向土壤中添加 Fe 及其被水稻根径向释放的氧氧化为 Fe,使 Fe 斑(Fe)的形成增加了 1.7-2.5 倍。添加 Fe 后,被 Fe 斑捕获的 C 量增加了 1.1 倍。因此,根表面无定形和复杂的 Fe(氢)氧化物形成的 Fe 斑作为有机质的“生锈汇”。考虑到全球稻田的覆盖面积,通过模型上推表明,根的径向氧损失和细菌 Fe 氧化可能会在每个水稻季将高达 130 Mg C 固定在 Fe 斑中。这代表了在长期水稻种植下,对现有碳库的新的和稳定的 C 的重要年度盈余。

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