富钾入侵植物调控根系分泌物和根际解钾菌联合解钾机制研究

Soil nutrients availability is frequently enhanced by exotic plant species invasion which promote its capacity for further invasion. More than 98% of total potassium is non-exchangble in soils and can be uptake only after being activated. However , many notorious invasive species can activate soil potassium and accumulate large amount of potassium in tissues. Up to now, how invasive species activates soil potassium via rhizosphere processes is unknown. This project aims to elucidate the processes of how invasive plant species responds to different soil potassium availability, regulates chemicals profile of root exudates and diversity of potassium-solublizing bacteria and enhances soil potassium availability. In this study, one of the potassium-rich and notorious invasive plant species, Solidago canadensis, is selected as an target species and compared to several accompanying native species. We study spatial distribution and transformation of potassium in soil and absorption by plants; the amount and chemicals profile of root exudates and their ability to activate soil potassium in response to soil potassium availability; diversity of potassium-solublizing bacteria and their ability to activate soil potassium and promote plant growth regulated by root exudates. This study will reveal the mechanisms of how potassium-rich invasive plant species enhances its ability to increase soil potassium availability and therefore may add more evidences how exotic species become successful in succeed in invaded regions.

提高土壤营养元素有效性以促进自身生长是外来植物成功入侵的机制之一。土壤中98%以上钾素为非交换态，须经活化为有效态方可被植物利用，但不少入侵植物却能够提高土壤钾素有效性并大量富集钾素，而富钾入侵植物如何通过根际过程活化土壤钾素尚未得到深入研究。本研究以富钾入侵植物加拿大一枝黄花（Solidago canadensis）为例，对比研究不同钾素水平下入侵植物和伴生土著植物的生长和钾素积累特性，阐明根际土壤中钾素空间分布、形态转化和有效性变化规律，揭示入侵植物钾素活化特征；在此基础上，通过根系分泌物释放量、解钾活性和关键解钾化学组分的变化，以及受根系分泌物调控的根际解钾菌遗传多样性、解钾活性和关键调控组分的变化，阐明根系分泌物和根际解钾菌的联合解钾机制。通过本项目研究有助于阐明基于提高土壤钾素有效性并富集钾素的入侵植物-土壤反馈作用机制，为深入揭示外来植物成功入侵机理及制定有效防控方案提供依据。

外来植物显著影响入侵地营养元素循环，并进而对自身入侵产生反馈作用。前期研究表明，入侵植物加拿大一枝黄花能显著富集钾素，可能是促进自身入侵的重要机理。项目比较研究了加拿大一枝黄花和本地植物对钾素的吸收和积累能力、通过凋落物和根系分泌物调控土壤解钾菌促进矿物钾向有效性钾的转变能力、钾素对加拿大一枝黄花和本地植物抗逆性、生长和竞争能力。研究发现和本地植物相比，加拿大一枝黄花能显著提高钾素在植被和土壤中的积累量，并提高了钾素的有孝心；其凋落物产量较高，分解速率较快，钾素含量更高，并能向土壤中更多钾素；加拿大一枝黄花根际土壤中含有更多土壤解钾菌，具有更高的多样性，其解钾能力更强；添加其凋落物和根系分泌物更能促进土壤中解钾菌的数量增长；添加土壤解钾菌能促进加拿大一枝黄花的生长。较高土壤营养水平提高了加拿大一枝黄花的竞争能力；较高钾素水平提高了加拿大一枝黄花的抗逆性，并促进了加拿大一枝黄花和本地植物的生长，提高了加拿大一枝黄花的竞争力。这些结果表明，钾素在加拿大一枝黄花入侵中具有重要作用，加拿大一枝黄花加速了钾素的循环，而钾素反过来可能促进了加拿大一枝黄花的入侵。研究结果为后续进一步研究外来植物入侵对生态系统的影响及外来植物入侵机理奠定了基础。