Improving photosynthesis and drought tolerance in <i>Nicotiana tabacum</i> L. by foliar application of salicylic acid

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