Root exudate signals in plant–plant interactions

Abstract

Plant-to-plant signalling is a key mediator of interactions among plant species. Plants can perceive and respond to chemical cues emitted from their neighbours, altering survival and performance, impacting plant coexistence and community assembly. An increasing number of studies indicate root exudates as key players in plant-to-plant signalling. Root exudates mediate root detection and behaviour, kin recognition, flowering and production, driving inter-and intra-specific facilitation in cropping systems and mixed-species plantations. Altered interactions may be attributed to the signalling components within root exudates. Root ethylene, strigolactones, jasmonic acid, (-)-loliolide and allantoin are signalling chemicals that convey information on local conditions in plant-plant interactions. These root-secreted signalling chemicals appear ubiquitous in plants and trigger a series of belowground responses inter-and intra-specifically, involving molecular events in biosynthesis, secretion and action. The secretion of root signals, mainly mediated by ATP-binding cassette transporters, is critical. Root-secreted signalling chemicals and their molecular mechanisms are rapidly revealing a multitude of fascinating plant-plant interactions. However, many root signals, particularly species-specific signals and their underlying mechanisms, remain to be uncovered due to methodological limitations and root-soil interactions. A thorough understanding of root-secreted chemical signals and their mechanisms will offer many ecological implications and potential applications for sustainable agriculture.

Intraspecific kin recognition contributes to interspecific allelopathy：A case study of allelopathic rice interference with paddy weeds

“…Intraspecific genetic variation can have important ecological consequences for interspecific interactions (Ehlers, David, Damgaard, & Lenormand, 2016;Fridley & Grime, 2010;Genung, Bailey, & Schweitzer, 2012). Kin recognition and allelopathic interference are important mediators of interspecific or intraspecific interactions among plants (Bilas, Bretman, & Bennett, 2020;Dudley, Murphy, & File, 2013;Kong et al, 2018;Wang, Kong, Wang, & Meiners, 2020). From a model system of allelopathic rice interference with paddy weeds, this study presents the first evidence that intraspecific kin recognition may have consequences for interspecific allelopathic interference.…”

“…However, the role of allantoin as a signal of relatedness still needs to be verified in cultivar specific or upstream signals. Allantoin may not be the signal but rather the effect of an unidentified, underlying signal (Wang, Kong, Wang, & Meiners, 2020).…”

“…When one or more species occur together and interact, plants may detect and recognize their neighbors, potentially differentiating interspecific individuals from conspecific individuals (Gruntman & Novoplansky, 2004), and even intraspecifically between kin and non-kin individuals (Dudley & File, 2007). Following neighbor detection and recognition, plants may adjust their growth and defense strategies, altering plant coexistence and community assembly (Wang, Kong, Wang, & Meiners, 2020).…”

Friends, neighbours and enemies: an overview of the communal and social biology of plants

“…Root exudate detection and response is reviewed in detail elsewhere in this issue (Wang, Kong, Wang, & Meiners, 2020a).…”

“…At the moment, root exudates seem the most likely candidates to act in neighbour recognition, but it remains a clear priority for the field to identify which signals are involved, whether they do encode specific information, and if so how. Root exudate detection and response is reviewed in detail elsewhere in this issue (Wang, Kong, Wang, & Meiners, 2020a).…”