Seed Priming with Gibberellic Acid Enhances Drought Tolerance in Sweet Sorghum by Modulating Cuticular Wax and Cutin Composition.

Drought stress severely constrains sorghum productivity, and seed priming has emerged as a potential strategy to enhance stress resilience. However, the role of cuticle deposition in seed priming-mediated drought tolerance remains unclear. In this study, the optimal GA priming concentration was determined and its effects on cuticular wax and cutin composition, as well as leaf water loss, were investigated in sorghum seedlings. A preliminary experiment identified 10 mg L-1 GA as the optimal dose, as it produced the greatest height (11.5%) and biomass (79.8%) under drought stress while significantly reducing MDA and O2- levels, indicating effective alleviation of oxidative damage. Under well-watered conditions, GA priming moderately increased alkanes (45.6%) and primary alcohols (16.3%) while reducing aldehydes (27.3%). However, under drought conditions, GA induced substantially greater increases in alkanes (76.4%), primary alcohols (257.3%), amyrin (451.5%), and other alcohols (56.3%). Regarding cutin monomers, GA further elevated alkanoic acids and cyclopropaneoctanoic acid by 58.2% and 31.4%, respectively, on top of drought-induced accumulation, indicating a synergistic effect between GA and drought signals in promoting cuticular deposition. Additionally, GA redirected the production of cutin with a chain length of C16/C18 towardC22 cutin. GA-primed plants displayed the lowest water loss rates, correlating with enhanced cuticular deposition. Collectively, these findings demonstrate that, in the single genotype tested under controlled-environment conditions, GA priming enhances drought tolerance in sorghum seedlings, acting through the modulation of cuticle composition to reduce leaf water loss while alleviating oxidative damage and improving growth.