红三叶基于化感作用的生态适应机制研究

Soil acidification is one of the important environmental problems in agricultural production, and expands the serious trend year by year. Many plants can't live in acid soil. Red clover as the main grass seed of southern animal husbandry has strong ability of tolerance in the acid soil. In natural habitats, red clover has obvious competitive advantage and easily forms a strong plant community by means of allelopathy. Research results show that the secondary metabolites in red clover changed obviously in order to improve the resistance, in response to environmental stress. Allelochemicals were secondary metabolites which were synthesized and released into the environment by the plants, and important medium of allelopathy, and also has the obvious response to stress. However, under the condition of stress, the regularities which red clover releases allelochemicals weren't reported. This project is on the basis of previous research results which the main allelochemicals and their mechanisms of action have been understood. The secretion rules of root allelochemicals for the different varieties of red clover under acid stress will be studied in this project. In addition, through the evaluations of soil microbial community structure and function diversities, and influences on soil physical and chemical properties, the interaction relations between secretion of root and soil microbial communities will be also discussed. The research results would interpret the ecological adaptation mechanism of red clover based on effect of allelopathy under acid stress, and will be expected to be used as the theoretical basis on soil improvement, environment protection and grassland construction.

土壤酸化是制约农业生产的重要环境问题之一，且有逐年扩大严重的趋势。许多植物无法在酸性土壤中生存，而红三叶对酸性土壤有较好的适应能力，是南方畜牧业的主要草种。在自然生境中，红三叶具有显著化感作用，生态适应能力强。研究表明，在受到环境胁迫下，红三叶体内次生代谢物会发生明显变化，提高植物的抗逆性。化感物质是由植物体内合成并释放到环境中的次生代谢物，是化感作用的重要媒介，对环境胁迫也有明显响应。然而关于不同胁迫条件下，红三叶化感物质的分泌规律研究却未见报道。本项目将在前期已明确主效化感物质及其作用机理的基础上，对不同品种红三叶在酸胁迫下根系化感物质的分泌规律进行研究。此外，通过评价土壤微生物群落结构和功能多样性以及对土壤理化性质的影响，对根系分泌物与土壤微生物群落的互作关系进行研究。本项目研究成果，将从多方面阐释酸胁迫下红三叶基于化感作用的生态适应机制，为土壤改良、环境保护和草场建设提供理论依据。

土壤酸化成为制约现代农业发展的主要限制性因素之一，而且随着污染的加剧和农药化肥广泛过量使用，有愈演愈烈之势。红三叶是集生态、药用、观赏的重要豆科牧草，可以适应酸性土壤，然而其适应机制尚未可知。本项目开展了酸性条件下不同品种不同生长时期红三叶的生长性状、生理生化指标和次生代谢物及其土壤分泌物检测。结果表明，酸胁迫下红三叶生长受到显著抑制，同时根际土壤细菌的丰富度和多样性降低，土壤微生物的代谢功能减弱，土壤矿化速率减缓。而与此同时，红三叶可以通过增加其体内可溶性糖和异黄酮含量，并从根系中分泌物出大量异黄酮，从体内和体外两方面来抵御和适应酸环境。如土壤中厚壁菌门和Saccharibacteria的相对丰度与酸度呈正相关关系，厚壁菌门的葡萄球菌属的相对丰度也急剧增加。此外，酸性环境下土壤中可溶性铝的含量会大幅增加，对植物生长造成毒害，因此本项目还开展了红三叶对铝毒的适应机制研究。红三叶通过将大量的铝转移到叶片中进行固定，同时分泌异黄酮到根系表面与铝离子进行络合，从而有效地降低铝对根系的影响。本项目的研究成果将对于红三叶的种植与利用，生态环境的治理与恢复具有重要指导意义。