Allelopathic Effects of Trifolium repens Root Exudates on Germination and Early Seedling Establishment of Poa annua

Abstract

Trifolium repens (white clover) is widely recognized for its ecological and agricultural importance as a cover crop and forage species, with the ability to influence surrounding vegetation through allelopathic interactions. Poa annua, a highly invasive annual grass weed, commonly infests turfgrass systems, orchards, and cultivated fields, where it competes aggressively with desirable plant species. The present study was conducted to evaluate the allelopathic effects of T. repens root exudates on the germination and early seedling establishment of Poa annua. Laboratory and greenhouse experiments were carried out using aqueous root exudate extracts obtained from T. repens plants. Different concentrations of root exudates were applied to P. annua seeds to assess their effects on germination percentage, germination rate, root elongation, shoot growth, and seedling vigor. The results demonstrated that T. repens root exudates significantly influenced the germination and early growth of P. annua in a concentration-dependent manner. Higher concentrations of root exudates markedly reduced seed germination, delayed germination rate, and inhibited root and shoot development of seedlings. Root growth was more strongly affected than shoot growth, indicating greater sensitivity of below-ground tissues to allelochemical compounds present in the exudates. Seedling vigor and establishment potential were also substantially reduced under elevated exudate concentrations. The inhibitory effects observed in the study suggest the presence of bioactive allelochemicals released by T. repens roots that interfere with physiological and metabolic processes involved in seed germination and seedling development. The findings highlight the potential use of T. repens as a suppressive cover crop for ecological weed management. Understanding allelopathic interactions between plant species can contribute to the development of sustainable weed control strategies aimed at reducing reliance on synthetic herbicides and improving agroecosystem sustainability.