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

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 (0.3mM) 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 stresss reduced the photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) while 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%, 52.22%. 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%.

干旱会导致烟草产量与品质下降，同时降低其净光合速率（net photosynthetic rate, Pn）。水杨酸（Salicylic acid, SA）参与调控众多植物生理过程，已被广泛应用于提升植物的抗旱性。本实验以烤烟（flue-cured tobacco）品种K326为试验材料，采用水培培养方式开展研究：每日向叶片喷施浓度为0.3mM的水杨酸溶液，连续处理3日后，采用15%聚乙二醇-6000（PEG-6000）溶液模拟中度干旱胁迫。结果表明，干旱胁迫会降低烟草的净光合速率、气孔导度（stomatal conductance, Gs）与蒸腾速率（transpiration rate, Tr），同时提升超氧化物歧化酶（superoxide dismutase, SOD）、过氧化物酶（peroxidase, POD）、过氧化氢酶（catalase, CAT）的活性，以及丙二醛（malondialdehyde, MDA）、脯氨酸与蛋白质的含量。与仅受PEG干旱胁迫处理的对照组相比，水杨酸处理使烟草的Pn、Gs与Tr分别提升了45.74%、26.82%与52.22%。此外，SOD、POD、CAT活性及蛋白质、脯氨酸含量分别提升了44.27%、50.18%、25%、34.69%与24.88%，而MDA含量则降低了23.89%。