Wheat (Triticum aestivum L.), a key grain food crop worldwide, faces increasing threats from combined abiotic stresses exacerbated by climate change. However, the comprehensive effects of drought, salinity, and high-temperature pressure on wheat seedlings remain poorly understood. Using the cultivar “Yannong 1212”, we conducted hydroponic experiments to investigate the physiological, morphological, antioxidant, osmoregulatory, membrane lipid peroxidation, and molecular responses of wheat seedlings to single and combined stresses, and then conducted multivariate statistical analyses. The results showed that drought or salt stress inhibited seed germination in a concentration-dependent manner. However, the combined stresses significantly inhibited germination and seedling growth, leading to leaf chlorosis, chlorophyll degradation, stomatal closure, and chloroplast damage. Physiologically, the combined effect of multiple stresses induced excessive ROS and MDA accumulation, promoted proline and soluble sugar synthesis, and triggered the dynamic responses of antioxidant enzymes. Drought stress increased SOD, POD, and CAT activities, whereas salt stress had the opposite effect, and combined stresses further increased SOD and POD activities, but reduced CAT activity. Additionally, stress-responsive genes were rapidly upregulated. Multivariate analyses confirmed that the combined stress of drought and heat was the most damaging. These findings explain the synergistic damage mechanisms of combined stresses, providing a theoretical basis for genetic improvement of wheat’s stress tolerance.
Li et al. (Fri,) studied this question.