FUNCTIONAL ROLE OF SECONDARY METABOLITES IN INTER-SPECIES PLANT COMPETITION

Abstract

Secondary metabolites (SMs) play a crucial role in shaping inter-species plant interactions, yet their precise functional role in competitive ecological outcomes remains insufficiently understood. This study quantitatively investigates how SMs influence germination, growth, and species dominance across controlled greenhouse experiments and natural field conditions. Five ecologically relevant plant species—Avena sativa, Trifolium pratense, Chenopodium album, Amaranthus retroflexus, and Medicago sativa—were analyzed for their allelopathic impact via bioassays, metabolite profiling (HPLC, GC–MS), and biodiversity surveys. Results demonstrated that Chenopodium album and Avena sativa exhibited the strongest germination inhibition effects, reducing germination rates by up to 51.3% and radicle length by over 36%. Metabolite analysis revealed elevated levels of phenolics and terpenoids in these species, directly correlating with suppression outcomes. Biomass allocation studies showed an average reduction of 25–35% in mixed cultures compared to monocultures, with corresponding declines in root–shoot ratios. Field studies further validated that higher rhizospheric SM concentrations were associated with reduced Shannon diversity indices and increased competitive balance ratios. Correlation matrices confirmed significant relationships between metabolite concentration and ecological suppression metrics (r ≥ 0.75). Collectively, these findings demonstrate that SMs are not passive defense compounds but active biochemical tools that alter inter-species dynamics and influence plant community structure. The study presents a novel integrative framework combining chemical ecology and plant competition theory, offering practical insights for weed management, ecological restoration, and biodiversity conservation. By identifying specific metabolites with strong ecological impacts, this research lays the foundation for future exploration into targeted allelopathic applications and metabolic engineering for ecological resilience.