Abstract: Plant-plant interactions is a fundamental issue in ecology. Plants are able to detect and perceive inter-specific and intra-specific neighbors and then adjust their growth, reproduction and defense strategies. Such inter-specific and intra-specific recognition and perception are mostly media-ted by secondary metabolites. Those chemical communications can initiate and activate the corresponding mechanism in allelopathy. In recent years, several novel plant-plant chemical interactions have been observed, such as kin recognition, and flowering and reproduction mediated by root communication. Till now, the inter-specific and intra-specific chemical interactions among plants mediated by volatiles have been substantially clarified. However, the mechanisms and soil-borne signaling chemicals involved in plant-plant chemical interactions mediated by root exudates remain poorly understood. Belowground chemical interactions not only determine the behavior of root invasion (approaching) and avoidance (repelling), but also regulate the flowering time and florescence. Accordingly, the chemical interactions involve the coordination between belowground and aboveground parts. On the basis of allelopathy and chemical recognition as well as corresponding allelochemicals and signaling chemicals, this review outlined recent research advances regarding plant-plant chemical interactions from kin recognition, root communication and behavior patterns, belowground chemical interactions to regulate flowering and reproduction. The efforts represented a mechanistically exhaustive view of plant-plant interactions.

Key words: allelopathy, chemical communication, kin recognition, signaling chemicals, root behavior, flowering regulation