New Insights into Allelochemicals’ Structure–Activity Relationship and Their Impact on Plant Physiological Processes and Environmental Interactions

Allelochemicals, such as phenolics, terpenoids, alkaloids, and fatty acids, regulate biological activity through their specific chemical structures, thereby influencing the growth of neighboring plants and the ecological environment. They collectively modulate plant growth and development via multiple mechanisms─including interference with cell division, regulation of hormone levels, suppression of photosynthesis, disruption of respiratory metabolism, and alterations to antioxidant systems and the rhizosphere microenvironment. Although the roles of allelochemicals are widely recognized, a systematic framework integrating their chemical structures with multilevel physiological and ecological consequences remains lacking. This review systematically synthesizes the relationships among the chemical structures, biological activities, and ecological functions of allelochemicals and, through multifaceted analysis, reveals the molecular networks and ecological effects underlying allelopathy. Furthermore, we construct a theoretically grounded framework oriented toward agricultural applications, offering feasible pathways for ecofriendly weed control, crop yield enhancement, and sustainable ecosystem management.