Potential Effect of Root Exudates from Ten Crops on Promoting Stress Tolerance in Alfalfa (Medicago sativa) Seedlings

Allelopathy plays a major role in agricultural production, influencing plant protection, crop yield, and crop rotation systems. This study investigated the effects of root exudates on 3105c alfalfa (<i>Medicago sativa</i>) seeds and seedlings to identify crops with strong and weak allelopathic potential. The results revealed that corn (<i>Zea mays</i> L.) (T1) exhibited the strongest allelopathic effects, whereas soybean (<i>Glycine max</i> (Linn.) Merr.) (T10) exhibited the weakest effects. T1 promoted seed germination by increasing radicle length and the simple vitality index. Both T1 and T10 promoted 3105c seedling growth and enhanced antioxidant capacity, albeit through different mechanisms. T1 primarily increased antioxidant capacity by elevating ascorbate and dehydroascorbate levels while reducing malondialdehyde content. In contrast, T10 enhanced antioxidant capacity by increasing soluble sugar and protein levels via hydroxyl free radical inhibition. These findings demonstrate that the allelopathic properties of corn effectively promote alfalfa growth by enhancing seed germination and improving physiological stress resistance.