Seasonal and Cultivar Differences in Salt-induced Change in Ascorbic Acid and Dehydroascorbic Acid Contents of Tomato Fruit

Abstract

Salt stress has been applied to improve the quality of tomato fruit, but ascorbic acid (ASA) and dehydroascorbic acid (DHA, oxidized form of ASA) contents in salt-stressed fruit have not been clearly understood. We examined the salt-induced changes in ASA and DHA contents of tomato fruit in two cultivars and two cropping seasons. Tomato plants were grown under closed irrigation systems in a greenhouse. Salt stress was applied by adding 50 mM and 100 mM NaCl to the nutrient solution. The results indicated that the ASA and DHA contents are not always increased by salt stress, and the effect depends on cropping seasons and cultivars. In the spring-summer season, the ASA and DHA contents in ‘Mini Carol’ (cherry type cultivar) decreased with an increase in the NaCl concentrations, whereas those in ‘House Momotaro’ (normal-fruited cultivar) increased. However, in the fall-winter season, the ASA and DHA contents in both the cultivars increased by salt stress. In addition, our data revealed that salt-induced changes in the ASA and DHA contents were not induced by changes in the ASA precursor, and suggest that, according to cultivars and cropping seasons, these changes may relate to the antioxidant systems against salt-induced oxidative stress.