Allelopathic and autotoxic effects of sorghum extract and residues on seed behavior, and morphological, physiological, and biochemical responses of several plants

This study comprehensively evaluated the allelopathic effects of sorghum ( Sorghum bicolor L.) aqueous extracts (control, and 2, 4, 6, and 8% extract), root residues, burned root residues on germination indices, growth, and biochemical parameters of eight crops (sorghum, corn, wheat, barley, sunflower, rapeseed, alfalfa, and cowpea) under PEG-6000-induced drought stress (20% PEG) using a two-phase approach (in vitro and greenhouse). Laboratory results demonstrated significant concentration-dependent inhibition across all parameters, including germination indices, vegetative growth, dry weight, and biochemical attributes (such as photosynthetic pigments, proline, soluble carbohydrate, and enzymatic activities of catalase, superoxide dismutase, and ascorbate peroxidase). Alfalfa and cowpea showed extreme sensitivity and were excluded from greenhouse trials. The greenhouse phase revealed differential stress tolerance among the six remaining species under combined root residue treatments, with sorghum exhibiting superior resilience compared to other crops. These findings highlight the dose-responsive allelopathic potential of sorghum derivatives and their practical applications in weed management and crop rotation systems, while emphasizing species-specific tolerance mechanisms under drought conditions.