Abstract
Ascorbic acid (AsA) is a well-known antioxidant that improves plant tolerance to salt stress; however, its effectiveness has not yet been sufficiently demonstrated depending on the method of application. In this context, this study was conducted to investigate the effects of 1 mM AsA applied as a priming agent (AsA/P), through the rooting medium (AsA/R), or via foliar spraying (AsA/F) on the growth, key biochemical parameters, and the antioxidant defense system of tomato seedlings (cv. Rio Grande)grown for two weeks in the presence of 100 mM NaCl. Results showed a noticeable reduction in growth traits, with significant decreases in relative water content (RWC), chlorophyll, total carbohydrates, proline, polyphenols, and AsA content, as well as in the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). However, the contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were significantly increased in salt-treated compared to control seedlings. Regardless of the application method, AsA improved seedling growth and increased RWC, chlorophyll, total carbohydrates, and proline contents. Furthermore, the contents of AsA and polyphenols, as well as the activities of SOD, CAT, and APX, were significantly enhanced, leading to a substantial decrease in the contents of H2O2 and MDA. The results also indicated that the AsA-induced mitigating effects were more prominent with the AsA/R method, followed by the AsA/F, whereas the AsA/P method was less effective. In conclusion, compared to the AsA/F and AsA/P methods, the AsA/R treatment can beconsidered an efficient and promising method to ameliorate the growth of tomato seedlings in salt-affected soils.