Weed-derived allelochemicals enhance maize performance through multidimensional modulation of growth and stress...

Allelopathic interactions between plants offer promising opportunities for developing sustainable weed management and biostimulant strategies in agriculture. This study evaluated the effects of aqueous leaf extracts from five common weed species (Amaranthus retroflexus, Parthenium hysterophorus, Alternanthera philoxeroides, Cynodon dactylon, and Trichodesma indicum) on maize (Zea mays L.) under field-relevant conditions. Extracts were applied at 5%, 10%, and 20% concentrations using four application methods: seed soaking, soil incorporation, foliar spray, and rhizosphere simulation. Across treatments, maize germination decreased by 15-55% relative to the control (p ≤ 0.05), while shoot and root lengths were reduced by up to 40% and 50%, respectively. Chlorophyll a and b contents declined by 20-60% in highly inhibitory treatments, whereas moderate treatments maintained pigment levels comparable to the control. Oxidative stress markers increased significantly, with malondialdehyde and electrolyte leakage rising by 30-120% (p ≤ 0.05), accompanied by a 1.5-2.0-fold increase in antioxidant enzyme activities (SOD, CAT, POD). Proline content increased by up to 115%, while abscisic acid (ABA) and indole-3-acetic acid (IAA) levels increased by 2-fourfold in several treatments, indicating coordinated stress and growth regulation. Multivariate analyses (PCA, clustering, and radar profiling) identified Trichodesma 20% foliar spray, Parthenium 10% seed soaking, and Alternanthera 5% rhizosphere simulation as the most effective treatments, exhibiting improved stress tolerance and partial growth maintenance. These findings demonstrate that weed-derived allelochemicals can exert both inhibitory and adaptive effects on maize, highlighting their potential utility in eco-friendly crop management strategies.