Exogenous Sugar Alleviates Salt Stress in Cucumber Seedlings by Regulating the Antioxidant System and Hormone Signaling.

Abstract

This study explored the regulatory effects of exogenous glucose (Glu) and sucrose (Suc) on the growth performance and physiological mechanisms of cucumber seedlings under salt stress. Using two cucumber cultivars as experimental materials, pot experiments demonstrated that salt stress significantly suppressed seedling growth, decreased chlorophyll content, and triggered oxidative damage. However, pretreatment with exogenous sugars effectively mitigated these adverse effects by maintaining photosynthetic efficiency, enhancing the activities of key antioxidant enzymes-superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX)-and reducing the accumulation of reactive oxygen species (ROS) and membrane lipid peroxidation. Transcriptomic analysis revealed that the two sugars differentially modulated antioxidant pathways and transcription factor networks to synergistically enhance salt tolerance. Specifically, sucrose preferentially activated POD, whereas glucose specifically induced APX and RbohD. Furthermore, glucose upregulated NAC and ERF family genes, while sucrose suppressed certain WRKY members. Both sugars contributed to the restoration of auxin and abscisic acid (ABA) signaling pathways. This study provides a theoretical foundation for the role of sugar signaling in enhancing crop resistance to abiotic stress.