Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) and salicylic acid (SA) exhibit protective effects against a wide array of stresses. In this study, we investigated the relative efficacy of exogenous H<sub>2</sub>O<sub>2</sub> and SA in conferring drought tolerance in rice (Oryza sativa L.). The experiment was repeated two times, firstly in a hydroponic system and secondly in soil. The results revealed that drought hampered germination indices, seedling growth, photosynthetic pigments, and water content, whereas increased proline content. It also triggered higher H<sub>2</sub>O<sub>2</sub> production and consequently elevated lipid peroxidation, which is a particular indication of oxidative damage. However, exogenous H<sub>2</sub>O<sub>2</sub> or SA treatment effectively alleviated oxidative damage in rice seedlings both in hydroponic and soil systems via upregulating antioxidant enzymes. Nevertheless, regulation of proline level and augmentation of plant-water status were crucial to confer drought tolerance. Exogenous H<sub>2</sub>O<sub>2</sub> or SA also protected photosynthetic pigments from oxidative damage that might help to maintain normal photosynthesis under drought. Besides, 5 mmol/L H<sub>2</sub>O<sub>2</sub> and 0.5 or 1 mmol/L SA showed similar effectiveness on mitigating drought stress. Finally, our findings suggest that exogenous H<sub>2</sub>O<sub>2</sub> or SA could evenly be effectual in the amending growth of rice seedlings under drought conditions.
Halo- and UV-B priming-mediated drought tolerance and recovery in rice seedlings
