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

This study investigated the allelopathic potential of sorghum (Sorghum bicolor L.) by applying aqueous extracts (0, 2, 4, 6, and 8%), root residues, and burned root residues to eight crop species (sorghum, corn, wheat, barley, sunflower, rapeseed, alfalfa, and cowpea) under PEG-6000-induced drought stress (20% PEG) using a two-phase design (in vitro and greenhouse). In the petri dish experiment, sorghum derivatives caused clear, concentration-dependent reductions in germination indices, seedling growth, biomass accumulation, and biochemical attributes, including photosynthetic pigments, proline, soluble carbohydrates, and antioxidant enzyme activities (CAT, SOD, and APX). Alfalfa and cowpea showed the highest sensitivity to the combined allelopathic and osmotic stress and were excluded from the greenhouse assay. During the greenhouse phase, species-specific tolerance patterns emerged: sorghum showed the greatest resilience to root residue treatments under drought conditions, while the remaining crops displayed varying degrees of susceptibility. Overall, the findings demonstrate strong dose-responsive allelopathic effects of sorghum across laboratory and greenhouse conditions, highlighting its potential for sustainable weed management and crop rotation systems, while underscoring the importance of interspecific variation in plant tolerance to drought stress.