Plant response to combined salinity and waterlogging stress: Current research progress and future prospects

Salinity and waterlogging stresses have catastrophic effects on plants. Physiological and molecular mechanisms of plant responses to individual salinity and waterlogging stresses have been widely investigated. Several research studies have been conducted to understand the combined effects of salinity and waterlogging on plant growth, photosynthesis, and mineral homeostasis, but no systematic review has been performed yet to comprehend the cumulative effects of salinity and waterlogging on plants. This work employed a systematic approach to examine how plants respond to combined salinity and waterlogging stress compared to individual stresses, and to identify potential research gaps in this field. Our analysis indicates that combined salinity and waterlogging stress inhibits growth processes more strongly than salinity or waterlogging stress alone. In addition, the combined effect of salinity and waterlogging on photosynthesis and ionic homeostasis is greater than the sum of the individual effect of each. Our analysis further implies that tolerance to combined salinity and waterlogging stress is mostly determined by salinity tolerance. An examination of subgroups found that hydrophytes are more vulnerable to combined salinity and waterlogging than halophytes. We identified several research gaps that should be addressed in future research to enhance plant salinity and waterlogging stress tolerance.