A combination of salt stress and waterlogging provides protection to tomato plants against the negative effects of waterlogging individually applied.

Abstract

Salt stress and waterlogging are two of the most common abiotic stresses in nature, often occurring concurrently. However, our understanding of the mechanisms underlying responses of plants to a combination of these stresses remains limited. In this study, we investigated growth, physiological and biochemical responses of Solanum lycopersicum cv. Micro-Tom to salt stress, waterlogging and the combination of both. Under waterlogging individually, plants showed increased plant height and longer root length. However, they exhibited a significantly smaller leaf area, fewer leaves, reduced fresh and dry weights, and lower relative water content compared to plants grown under controlled conditions. These effects were more severe than those caused by salt stress alone. Interestingly, the growth inhibition from waterlogging was alleviated under combined salt and waterlogging stress. This attenuation may be associated with decreased accumulation of H₂O₂ and oxidized lipids, along with increased proline and photosynthetic pigment contents compared with waterlogging individually applied. However, ROS accumulations and contents of photosynthetic pigments were not straightforwardly linked to the activity of photosynthesis. In addition, activities of various antioxidant enzymes such as CAT, GPX and GST as well as those involved in the AsA-GSH cycle were differently altered by salt stress and waterlogging, individually and in combination. Taken together, these results suggest that the response of tomato plants to salt stress and waterlogging, individually and in combination, can be differently modulated via fine-tuning of acclimation mechanisms to oxidative stress.