根系有机酸分泌物对茶树根土界面微域氟有效性的影响机理

茶树是高聚氟植物，根土界面微域是土壤氟进入根系，进而在叶片累积的重要通道。根系分泌物通过影响根际土壤有效态氟的含量，进而调控根系的吸收富集。有机酸作为茶树根系分泌物的主要组分，对根土界面氟形态与有效性的影响及其作用机理尚不清楚。本项目基于前期研究基础，利用根箱装置原位收集根际土壤溶液，采用HPIC-UVVIS及27Al-NMR技术研究茶树有机酸分泌物对土壤氟的溶出释放与氟形态及铝-氟络合物组成的影响；把薄膜梯度扩散技术与微电极技术相结合考察根际土壤有效态氟的释放与活化规律；利用透射电镜与ICP相结合的方法分析有机酸分泌物对茶树根表铁氧化物胶膜的结构、组成及其对根系吸收富集氟的影响；阐明有机酸分泌物影响茶树根土界面微域氟形态转化及有效态氟含量的变化规律，揭示有机酸分泌物调控根际和根表氟有效性的微观机理。该研究为剖析茶树高量富集土壤氟的根际效应，阻控土壤氟向茶树的迁移富集提供理论与实验依据。

Plant root exudates severely influence the physical, chemical and biological properties of nutrients and toxic substances in rhizosphere and root surface, and consequently control the absorption and accumulation of those substances by roots..Tea plant is a super-accumulator.Root-soil interface is a critical approach to absorb fluoride from soils to roots, and thus accumualte of fluoride in tea leaves(＞90%).Low molecular weight organic acids including malic acid, citric acid and oxalic acid, are the most constitutes in root exudate of tea plant, which can significantly impact the speciation and availability of nutrients and contaminants in micro-domain of root-soil interface. However, the reasons are not clear. The purposes of this study are to investigate the impacts of main organic acids in root secretion on the speciation and availablity of fluoride in root-soil interface by the root boxes methods. The competition and chelation of root secreted organic acids with aluminium in soil solution of rhizosphere, and its effects on the composition of Al-F complexes, release and activation of available fluoride will be studied by using HPIC coupled UV-VIS detector and 27Al nuclear magnetic resonance technology. The diffusive gradients in thin-films (DGT) and microelectrode technology will be performed to investigate the influences of root secreted organic acids on the contents of available fluoride in rhizosphere. The effects of different organic acids on the structure and constitute of iron plaque on the tea plant root surface will be studied by using the transmission electron microscopy and ICP methods. The mechanisms of how the different organic acids regulate the speciation and availability of fluoride in root-soil interface, and thereby control the fluoride absorbed by tea roots will be clarified. The results from this study will provide critical facts to explain the micro-mechanisms of soil fluoride absorbed and accumulated by tea roots, and then to elucidate the rhizosphere effects of hyperaccumulation of soil fluoride in tea plants.