Drought causes a decrease in tobacco yield and quality as well as a reduction in net photosynthetic rate. Salicylic acid (SA) is involved in the regulation of many physiological processes and has been widely used to improve plant drought tolerance. The hydroponic experiment was carried out on flue-cured tobacco variety K326. SA solutions (0.3 mM) were sprayed on the leaves every day for three days, after which 15% PEG-6000 was used to simulate moderate drought. The results showed that drought stress reduced the photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr), while it enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), malondialdehyde (MDA), proline and protein content. Compared with PEG drought stress, SA improved the Pn, Gs and Tr by 45.74%, 26.82%, and 52.22% respectively. Besides, the activities of SOD, POD, CAT, protein and proline content increased by 44.27%, 50.18%, 25%, 34.69% and 24.88%, respectively, while the MDA content decreased by 23.89%. Furthermore, SA spraying increased the drought tolerance of tobacco by modulating the expression level of the genes associated with photosynthesis, carbon metabolism, and photosynthesis-antenna proteins. Hence, SA spraying reduced the inhibition of drought on photosynthesis and stimulated the antioxidant system, thus improving the drought resistance in tobacco.

干旱导致烟草产量和质量下降以及净光合速率降低。水杨酸（SA）参与许多生理过程的调节，并被广泛用于提高植物的耐旱性。在烤烟品种K326上进行了水培试验。连续三天每天向叶片喷洒SA溶液（0.3 mM），之后用15% PEG-6000模拟中度干旱。结果表明，干旱胁迫降低了光合速率（Pn）、气孔导度（Gs）和蒸腾速率（Tr），而增强了超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）、丙二醛的活性。 (MDA)、脯氨酸和蛋白质含量。与PEG干旱胁迫相比，SA分别提高了Pn、Gs和Tr的45.74%、26.82%和52.22%。SOD、POD、CAT活性、蛋白质和脯氨酸含量分别增加44.27%、50.18%、25%、34.69%和24.88%，MDA含量降低23.89%。此外，喷施SA通过调节与光合作用、碳代谢和光合作用天线蛋白相关的基因的表达水平来提高烟草的耐旱性。因此，喷洒SA可以减轻干旱对光合作用的抑制，刺激抗氧化系统，从而提高烟草的抗旱性。SA喷洒通过调节与光合作用、碳代谢和光合作用天线蛋白相关的基因的表达水平来提高烟草的耐旱性。因此，喷洒SA可以减轻干旱对光合作用的抑制，刺激抗氧化系统，从而提高烟草的抗旱性。SA喷洒通过调节与光合作用、碳代谢和光合作用天线蛋白相关的基因的表达水平来提高烟草的耐旱性。因此，喷洒SA可以减轻干旱对光合作用的抑制，刺激抗氧化系统，从而提高烟草的抗旱性。