Limonene: A potent biostimulant for improving the drought tolerance in industrial hemp

Drought can significantly impact fiber crop cultivation due to the plants specific water requirements and its extended vegetative period. The objective of the research is to investigate the impact of various levels of foliar applied limonene for improving the drought stress tolerance in hemp. To evaluate the mechanism of drought tolerance in hemp, a pot trial was conducted under greenhouse conditions comprising of two factors drought stress i.e., control = 75%–100% field capacity, moderate drought stress = 50%–60% field capacity and severe drought stress = 30–40% field capacity and various treatments of foliar applied limonene (L 0 = control; L 1 = 0.01%; L 2 = 0.03%; L 3 = 0.05%). The findings revealed that drought stress had negative effect on hemp growth at various growth stages, biomass (above and below ground), photosynthesis and gas exchange traits under various severity levels of the drought. Severe drought stress significantly decreased the leaf greenness value (27.73%), lipid peroxidation (108.96%) and modulated the activities of antioxidant enzymes in the hemp plants. The optimal level of limonene (L 2 treatment group) showed significant improvement in biomass, photosynthetic and osmolyte traits relative to untreated control treatments. Furthermore, the multivariate analyses confirmed that exogenous limonene application at an optimal rate coordinates physiological and biochemical responses to mitigate drought stress. Overall, it was concluded that limonene application at an optimal rate (0.03%) was beneficial in mitigating the adverse effects of drought by maintaining their growth and antioxidant enzymes activity. These findings provide a theoretical basis for understanding the mechanism by which limonene application mitigates the drought stress. This finding may have significant implications for farmers, as it provides a potential solution to mitigate the negative effects of water stress on fiber crop productivity.