微/纳米结构羟基磷灰石调控水稻根系吸收Pb的微观机理

Lead (Pb) in soil which could transfer to rice and accumulate in grain affected the quality of rice and food safety seriously, and attracted the social widespread attentions. This project intends to adopt micro/nanostructure material hydroxyapatite (HAP) which is applied to rice root to form barrier layer for heavy metal Pb, in order to reduce Pb absorption in aboveground parts of rice. Scanning electron microscope and laser confocal microscopy is used to study the adsorption of HAP in root surface and the absorption, transfer and distribution of HAP in rice root by means of the rice root section and HAP dye. Transmission electron microscopy is used to determine the distribution and orientation of the small size of HAP in root cells and subcellular fraction. The research clarifies the relationships of size and morphology with the adsorption of HAP in root surface or the absorption of HAP in root. Under simulative Pb pollution conditions, the immobilization effect of Pb by HAP in root is studied, and the combination of the scanning/transmission electron microscopy with ICP-MS reveals that the microcosmic mechanism of micro/nanostructure hydroxyapatite regulate the absorption of Pb in rice root. The expectation is to establish a new kind of method to reduce Pb uptake and transfer in rice by nanotechnology. The study is of great significance to ensure regional agricultural products safety, improve the quality of rice and protect human health.

土壤中铅（Pb）向水稻中传输并且在籽粒中富集严重影响了稻米的品质和食品的安全，已引起了社会的广泛关注。本项目拟采用将微/纳米结构材料羟基磷灰石（HAP）应用于水稻根部，在根部形成重金属Pb的阻挡层来减少水稻地上部Pb的吸收。通过对水稻根部的切片和HAP染色的方法，利用扫描电镜和激光共聚焦显微镜研究HAP在水稻根表的吸附和根内的吸收、转移和分布；利用透射电镜确定小尺寸HAP在根细胞和亚细胞中的分布和定位；阐明HAP在水稻根表吸附和根内吸收与HAP形貌和尺寸的关系。在人工模拟Pb污染的环境条件下，研究存在于根部的HAP对Pb的固定效果，并通过扫描/透射电镜和ICP-MS相结合的方法揭示微/纳米结构羟基磷灰石在水稻根表和根内调控水稻Pb吸收的微观机理，以期建立一种利用纳米技术减少Pb在水稻体内吸收和转移的新方法。本研究对于保证区域农产品安全、提高稻米质量、保障人体健康具有重要意义。

水稻中Pb的吸收和富集会严重影响稻米的食用安全，因而减少水稻体内Pb浓度(尤其是籽粒)具有重要意义。本项目从微纳结构羟基磷灰石(mnHAP)对水稻根表Pb的化学行为、纳米羟基磷灰石(nHAP)在根内的分布和归趋及其对根内Pb有效性的作用过程和机制等方面开展研究，主要结论为：(1)水稻根表可以吸附大量mnHAP，该种形貌和大小的HAP不能进入根内；mnHAP在根表可以通过离子交换和沉淀反应将Pb2+的形态改变，并减少其向根内部的转移；(2)水稻根部可以吸收nHAP(球状，粒径大小：20±5 nm)。在Pb处理14天后，与对照相比，nHAP处理的水稻对Pb2+的耐性增强并且地上部Pb含量显著降低。透射电镜和能谱结果表明，与Pb2+作用后，nHAP形貌发生显著变化，形成了针状或块状含Pb物质。并且反应产物主要分布在植物根部的细胞壁周围以及细胞间隙和液泡中。(3)通过盆栽实验研究发现，在培养前期(分蘖期) nHAP可以减少水稻Pb的吸收，后期(孕穗和成熟期)的阻控效果不是很理想。这主要是因为水稻一直生长，而固定材料的长效性不足造成的。以上的结果对利用纳米技术在植物根表和根内调控Pb的有效性具有较重要的参考意义。