Mechanisms of allelopathic interactions for sustainable weed management

Plant allelopathy is a response to external stimuli by releasing secondary metabolites. It can be an effective sustainable strategy for weed control. Roots are the main point of release of allelochemicals. This phenomenon has the potential to facilitate environmentally cleaner weed control and avoid the concerns associated with the misuse of agro-chemicals for pest and weed management. The review comprehensively elaborates the mechanisms involving the release of allelochemicals by plants and the factors affecting its transport from a donor plant to a receiver. Although allelochemicals are produced by the entire plant, root exudation is the primary source of release of these chemicals into the soil environment. The study attempts to lucidly explain the physiology behind phytotoxic effects imparted by allelochemicals on target plants. We have discussed the various direct and indirect effect of allelochemicals on plant physiology and morphology. The review sheds light on the phytotoxic variation caused due to variable residue decomposition rates under changing climatic conditions. The various crop-weed, weed-crop and weed-weed allelopathic interactions and their possible response mechanisms have been briefly elaborated with reference to earlier works. We have shown the potential of integrating allelopathy and agronomic management practices for sustainable and environmentally safe weed management. The mechanistic insight of interferences caused by environmental factors on the bioavailability of allelochemicals is essential to develop an environmentally sound method of curbing the weed menace in agro-ecosystems. The studies on transport processes involving the release of allelochemicals from plants need more attention so as to exploit this knowledge in regulating the output of these compounds at a cellular level.