Allelopathic characterization and allelochemicals identification of hemp ( Cannabis sativa L.) leaf residue

Allelopathy presents significant potential in sustainable agriculture as a defensive mechanism for plants. Hemp (Cannabis sativa L.) exhibited allelopathic properties, and the cultivation of hemp as an economic crop yields substantial leaf residue. This study aims to evaluate the allelopathic effects as well as a mode of action of hemp leaf on target plants and to identify the allelochemicals released from hemp leaf. The investigation focused on the phytotoxic effects of hemp leaf leachate, obtained via the sandwich method at concentrations of 0.25 %, 0.50 % and 1.00 %, on wheat, itchgrass, lettuce, pea bean and hemp species. Results indicated that a high concentration of hemp leaf inhibited seed germination and seedling growth across the tested plants with varying degrees of inhibition observed among recipient species. Analysis of hemp leaf's allelopathic action revealed its efficacy in inducing reactive oxygen species (ROS) overproduction, diminishing cell viability and inhibiting mitosis division, leading to root growth inhibition. These effects are attributed to the synergistic action of phenolic compounds and cannabinoids released from hemp leaves. Pot culture experiments incorporating hemp leaf into soil corroborate observations made under laboratory conditions, demonstrating consistent impacts on germination and seedling growth. Hemp leaf had no effect on pigment accumulation, but at high concentrations, it reduced the leaf area of all tested plants. Hemp leaf residues became intricately intertwined with soil factors. The biomass of hemp leaf emerges as a potential source of herbicidal substances, offering a promising prospect for integration into agricultural systems to achieve effective and sustainable weed control.