Effects of exogenous salicylic acid on antioxidative responses, phenolic metabolism and photochemical activity of strawberry under salt stress

To further clarify the specific photochemical mechanisms of salicylic acid (SA)-mediated adaptation to salt stress, this experiment was conducted to examine the effect of SA (100 and 500 μM) on photosynthesis, antioxidative capacity and phenolic metabolism in strawberry plants under salt stress (50 mM). The results showed that high SA had a negative effect on strawberry plants as reduced leaf dry weight in plants that exposed to 500 μM SA under non-salt stress conditions. Salt stress negatively affected the leaf dry weight, whereas foliar spray of 100 μM SA alleviated the salt-induced inhibitory effects on the plant growth. Salt stress caused a significant decrease in photosystem performance index (PIabs); however, plants exposed to salt stress after SA pretreatment conserved their photosynthetic electron transport rate, compared with NaCl-alone treated plants, relating to the improvement of water-splitting complex on the donor side of PSII (Fv/Fo). The application of 100 μM SA in saline condition also increased the accumulation of soluble sugars like trehalose (Tre). Lipid peroxidation was observed in plants subjected to salinity stress, as evidenced by higher malondialdehyde (MDA) levels. In contrast, foliar spray of SA at a concentration of 100 μM promoted catalase (CAT) activity as well as phenolic content, thus reducing MDA and, consequently oxidative damage to membranes. Hence, foliar application of SA at 100 μM was effective in alleviation of salt stress in strawberry by improving PSII functioning, induction of compatible osmolytes and phenol metabolism, and mitigating membrane damage.