Climate change is intensifying the co-occurrence of salinity and waterlogging, exposing plants to a compound stress that is difficult to predict from single-stressor responses. Here, we synthesized evidence from 109 studies encompassing 4597 observations to quantify how plant growth and key physiological modules respond to salinity, waterlogging, and their combination across major ecological groups and crops. Across moderate stress intensities, combined effects were largely consistent with a multiplicative expectation (i.e., the combined effect equals the product of the individual effects), but shifted toward synergistic inhibition once salinity and/or flooding depth exceeded ecological-group-specific thresholds. Salinity tolerance was more closely associated with the maintenance of ion homeostasis, whereas waterlogging tolerance was more closely linked to sustaining internal aeration and metabolic function under hypoxia. Ecological strategies diverged sharply: hygrohalophytes maintained 56.5% of control growth under combined stress-significantly outperforming mesophytes (37.4%)-by jointly stabilizing Na+ exclusion/K+ retention, carbon-energy metabolism, and root aeration. Threshold analyses identified transition points beyond which energy limitation, ionic imbalance, and oxidative damage increasingly reinforced one another, driving a shift toward synergistic inhibition and pronounced performance decline. Because molecular pathways primarily fine-tune these core physiological modules, our synthesis indicates that near-term adaptation will depend on actionable management that limits root-zone salinity and improves aeration/drainage. Integrating evidence from stress-responsive genes, physiological decision nodes, and field-relevant interventions, we propose an operational gene-environment-management (G × E × M) framework that couples genetic potential with exposure-managing agronomy to keep systems below tipping points, thereby securing crop production and preserving biodiversity under accelerating compound climatic extremes.
Qiu et al. (Wed,) studied this question.