根系分泌物介导的根系亲缘识别对植物生长策略的影响

One of the fascinating discoveries in plant ecology in the last decade is that plant roots are able to discriminate the identity of their neighbors between kin and non-kin. Kin selection theory predicts that such an ability of kin recognition enables plants to reduce competition intensity between their kin neighbors, leading to the increase of their fitness. However, this viewpoint remains the subject of intensive debate, which is mainly caused by the confounding effects on the results of previous studies employing the traditional root competition setups. Using Arabidopsis thaliana and Pisum sativum as model species, the present research project aims to investigate the effects of kinship on the intra-specific root interaction in plants. To avoid confounding factors, only root exudates of competitors rather than the real competitors will be introduced to the focal plants in our experiments, basing on the underlying physiological mechanism that root exudates function as the cues of neighbors’ identities in the kin recognition process. To investigate the effects of root-mediated kin recognition on growth strategy and fitness of plants, both vegetative (i.e. roots, leaves and stems) and reproductive (i.e. seeds) performance of plants in kin root exudates and non-kin root exudates treatments will be compared. In addition, to understand how resource environment regulates the effects of kin recognition, treatments of different nutrient levels will be applied; to understand how kinship structure environment regulates the effects of kin recognition, treatments of root exudates mixtures from both kin and non-kin will also be carried out. We hope these studies could provide theoretical bases for plant breeding and cultivation management, from the aspects of increasing levels of the cooperation and improving environmental conditions for the cooperation between kin neighbors, respectively.

植物根系具有识别亲缘与非亲缘竞争者的能力，是近十年来植物生态学领域的重大科学发现之一。亲缘选择理论预测，根系亲缘识别可使亲缘个体间竞争强度下降，适合度增加。然而，此观点仍存在较大争议。传统的根系竞争实验方法中不可控因素对研究结果的干扰，是产生争议的重要原因。本项目以拟南芥和豌豆为材料，根据根系分泌物介导根系亲缘识别这一生理学基础，采用以竞争者根系分泌物替代竞争者本体的实验方法，分析在不同亲缘类型根系分泌物实验处理中，植物的营养（根、茎、叶）生长和繁殖（种子）生长的差异，揭示根系亲缘识别对植物生长竞争策略及适合度的调控作用；并且，通过设置养分梯度，以及设计亲缘与非亲缘根系分泌物混合共存的实验处理，分别探讨资源环境和亲缘结构环境对根系亲缘识别效应的影响。研究旨在深入理解亲缘关系对植物种内相互作用的调控作用；期望从提升亲缘合作水平和改善亲缘合作环境角度，为植物品种改良和生产经营管理提供理论依据。

植物根系具有识别亲缘与非亲缘竞争者的能力，是近十年来植物生态学领域的重大科学发现之一。亲缘选择理论预测，根系亲缘识别可使亲缘个体间竞争强度下降，适合度增加。然而，此观点仍存在较大争议。本项目选取小麦为研究对象，根据根系分泌物介导根系亲缘识别过程这一生理学基础，采用以竞争者根系分泌物替代竞争者本体的实验方法，分析在不同亲缘类型根系分泌物实验处理中植物的生长差异，并且通过设计亲缘与非亲缘根系分泌物混合共存的实验处理，探讨亲缘结构环境对根系亲缘识别效应的影响；选取烟草为研究对象，采用水培法研究植物根系异我识别对植物抗逆、防御性生理特征的影响；选取芨芨草为研究对象，采用野外调查的方法，研究植物根系垂直分布特征对邻居植物的物种和类别的响应特征，及其对种间根系生态位分离现象的影响。研究发现，植物对亲缘识别的响应可在比根长、比叶面积等形态性状，而非生物量水平上体现。此外，植物应对由复杂邻体构成的混合型亲缘环境时的生长与竞争策略并非简单地基于邻体中的亲缘个体比例而定。因此，植物进行亲缘识别的内在机制不是依据亲缘信息密度（或浓度）的量效反应。植物对邻体感知和亲缘识别的响应不仅仅体现在竞争策略上，还可体现在抗逆防御方面。个体间根系互作能诱导植物产生防御性生理响应。这种响应可能是由于植物根系邻体识别过程与抗逆防御生理响应过程具有相同的化学调控因子所引起的巧合；也可能是由于邻体的出现与被病虫害攻击的概率增加具有相关性导致的自然选择的结果。在干旱区生态系统中，植物的种间根系生态位分离并不是一个普遍性现象；在群落尺度上，它的出现在很大一定程度上是种间特异性根系互作改变植物根系分布的结果。相关研究结果有利于深入理解亲缘关系对植物相互作用的调控机制，可为作物品种改良和农业生产经营管理，以及干旱区植被恢复提供科学依据。