Mechanism of exogenous citric acid alleviating salt stress in Festuca arundinacea

As a natural compound, citric acid has been used as an exogenous additive to alleviate environmental stresses on plants. In this study, tall fescue (Festuca arundinacea) was treated with two salt concentrations (150 and 300 mmol·L⁻¹) to explore the effects of exogenous citric acid on the growth, physiological characteristics, and related gene expression levels of tall fescue under different concentrations of NaCl. The results showed that plant height, leaf water content, and the activities of antioxidant enzymes, such as peroxidase, were increased after the application of citric acid after 150 mmol·L⁻¹ NaCl treatment. In addition, citric acid improved the photosynthesis of tall fescue by promoting chlorophyll synthesis. It also induced the expression of SOS1, NHX1, ATCS, and regulated the negative effects of Na⁺. However, under long-term treatment with 300 mmol·L⁻¹ NaCl, citric acid had no significant effects on the growth and physiological conditions of tall fescue. These results indicated that, when the NaCl concentration was less than 300 mmol·L⁻¹ or when plants were treated with 300 mmol·L⁻¹ for a short time, the addition of citric acid effectively alleviated salt damage in tall fescue.