Physiological mechanism by which exogenous salicylic acid alleviates salt stress injury in Osmanthus fragrans seedlings

Salicylic acid (SA) mitigates salt stress in plants, yet its combined effects with salinity on Osmanthus fragrans remain unstudied. O. fragrans is a key Chinese ornamental tree, whose growth and use are restricted by salinization. Therefore, we aimed to evaluate the effect of SA application on O. fragrans under salt stress. O. fragrans seedlings were subjected to NaCl, SA, and NaCl+SA treatments, and their physiological and growth responses to salt stress were examined. Under NaCl, plant height, leaf mass per area, photosynthetic rate, and pigments of O. fragrans decreased by 29.5, 20.6, 42.2, and 29.2%, respectively. Notably, the SA application alleviated these effects by enhancing photosynthesis and the activities of antioxidant enzymes, improving photosynthetic pigments, and the contents of compatible solutes. The findings provide important insights into physiological mechanisms underlying SA-mediated salt tolerance, and provide a practical basis for the application of SA in improving the growth of O. fragrans in saline soils.