Jasmonate-Mediated Mitigation of Salinity Stress During Germination and Early Vegetative Development in Hemp

Climate change and soil salinization threaten crop productivity, particularly affecting salt-sensitive species like hemp (Cannabis sativa L.), which is gaining importance in sustainable agriculture and bioeconomy. Jasmonates (JAs) offer promising potential for enhancing plant abiotic stress tolerance. Given hemp's inherently low salt tolerance and limited data on JAs-mediated responses, we investigated salinity tolerance JAs modulation using methyl jasmonate (MeJA; 0.001-0.01 mM) and the JAs-biosynthesis inhibitor mefenamic acid (MEF; 0.01-0.1 mM) applied via seed priming or foliar treatment in factorial experiments with NaCl concentrations of 0.05-0.3 M. We demonstrate that MeJA and MEF differentially modulate responses of Henola hemp variety to salt stress during germination and seedling development. At 0.1 M NaCl, 0.01 mM MeJA enhanced germination rate by 25% compared to the salt-only control, indicating a protective effect on initial development, whereas 0.1 mM MEF exacerbated salt toxicity by increasing seed damage and reducing respiration by 57%, subsequently suppressing seedling growth. In 25-day-old seedlings exposed to 0.3 M NaCl, 0.001 mM MeJA treatment increased root length by 30 mm, fresh biomass by 50%, chlorophyll content by 20%, and photosynthetic efficiency by 23%, while reducing water deficit by 60% and leaf injury by 40%. MEF co-treatment partially reversed these protective effects, reducing MeJA-mediated improvements, confirming that maintaining JAs homeostasis is critical for salt-stress adaptation. These findings establish MeJA as a promising tool for enhancing hemp cultivation under saline conditions and provide a framework for integrating JAs treatments into sustainable hemp cultivation protocols.