Inhibition or interference? Revisiting allelopathy through the effects of Triadica sebifera on Chrysanthemum...

Allelopathy has been viewed as an interaction in which plant-released secondary metabolites suppress the growth of neighboring plants through direct toxic effects. However, this perspective likely overestimates the role of toxicity. It remains unresolved whether the inhibitory effects commonly attributed to allelopathy primarily reflect passive physiological damage in recipient plants or instead arise from actively regulated responses initiated by the recipients themselves. Here, we establish an integrative framework to re-evaluate allelopathic effects, using Chrysanthemum seticuspe as an ecologically representative recipient species. Rather than treating allelopathy as an intrinsic property of a single donor plant, we adopt a recipient-centered perspective and systematically examine responses across developmental, cellular, physiological, hormonal, and transcriptomic scales, with interactions involving Triadica sebifera (Euphorbiaceae) leaf litter powder serving as an illustrative case. Growth assays revealed persistent suppression of early radicle elongation in recipient plants. Notably, this suppression was not associated with widespread cellular structural disruption. Instead, recipient plants exhibited predominantly coordinated regulatory responses, including transient oxidative signaling, activation of detoxification pathways, extensive hormonal reprogramming, and downregulation of growth-associated metabolic processes. Together, these responses indicate a regulated shift toward defense-prioritized developmental states rather than irreversible toxic injury. Collectively, our findings support a reinterpretation of allelopathy as a process that operates primarily through allelochemical interference, inducing active regulatory reprogramming in recipient plants. Under natural, low-concentration conditions, such interactions are likely to function as chemo-ecological filters that modulate plant development, tolerance, and competitive outcomes, thereby shaping plant coexistence and community.