Foliar Application of Selenium Enhances Drought Tolerance in Tomatoes by Modulating the Antioxidative System and Restoring Photosynthesis

Abstract

Drought stress can impact the physiological and biochemical properties of crops. However, selenium (Se) can effectively alleviate the abiotic stress experienced by plants. This study aims to investigate how applying selenium to tomato leaves affects their antioxidant system and photosynthetic traits when subjected to drought conditions. The experiment used four different foliar selenium concentrations and three different irrigation levels. The investigation scrutinized the effects of foliar spraying employing different selenium concentrations on the antioxidant system, osmotic adjustment substances, photosynthetic performance, and growth indices of tomatoes under drought stress. The findings indicated that drought stress led to cellular oxidative damage, significantly elevating peroxide, MDA, proline, and soluble sugar content (p < 0.001). Under severe drought stress, malondialdehyde (MDA) and proline levels increased by 21.2% and 110.0% respectively, compared to well-watered conditions. Concurrently, the net photosynthetic rate exhibited a reduction of 26.0% and dry matter accumulation decreased by 35.5%. However, after spraying with a low concentration of selenium, selenium reduced oxidative damage and malondialdehyde content by reducing the content of peroxide in leaves, restoring photosynthesis, and promoting the normal growth of tomato. Compared to the control group, spraying with 2.5 mg·L−1 selenium resulted in a 21.5% reduction in MDA content, a 111.8% increase in net photosynthetic rate, and a 29.0% increase in dry matter accumulation. When subjected to drought stress conditions, foliar spraying of low concentrations of selenium (2.5 mg·L−1) can effectively reduce oxidative damage caused by drought stress and alleviate growth constraints in tomatoes. In addition, treatments with high selenium concentrations exhibited specific toxic effects. These findings offer valuable insights into the mechanisms governing selenium-induced drought tolerance in tomatoes, thus advancing our comprehension of standard tomato production practices.