Effects of drought and waterlogging stress on the ascorbate-glutathione cycle of hairgrass

The ascorbate-glutathione (AsA-GSH) metabolic cycle serves as a central regulatory hub for maintaining cellular redox homeostasis in plants, providing a critical defense mechanism against oxidative damage caused by abiotic stressors, such as water deficit. This study employed a completely randomized block design to analyze dynamic changes in AsA and GSH content, along with enzymatic activity profiles in the AsA-GSH cycle, within Deschampsia caespitosa shoots and roots under varying intensities of waterlogging treatments heavy waterlogging stress (HW), medium waterlogging stress (MW), light waterlogging stress (LW) and drought treatments light dry stress (LD), medium dry stress (MD), heavy dry stress (HD). Key findings include: 1) Stress tolerance thresholds‌: Complete mortality occurred in plants exposed to HW and HD treatments by day 35. Under MW and LW conditions, both shoot and root antioxidant levels (AsA/GSH) and redox homeostasis progressively increased with rising stress intensity. Conversely, LD and MD treatments triggered an initial elevation followed by a decline in these parameters, suggesting distinct adaptation strategies between waterlogging and drought. 2) Enzymatic coordination‌: Water stress substantially upregulated key enzymes involved in both AsA biosynthesis (L-galactose-1,4-lactone dehydrogenase) and regeneration pathways (ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione peroxidase, and glutathione reductase). Strong positive correlations were observed between enzymatic activity levels and antioxidant concentrations/redox status, confirming pathway synergy in reactive oxygen species scavenging‌. These results demonstrate that D. caespitosa maintains high AsA-GSH cycle efficiency under LW, MW, and LD conditions through the coordinated enhancement of biosynthesis and regeneration capacities, effectively mitigating ROS accumulation. This study elucidates the molecular basis of wetland plant adaptation to hydrological extremes and provides actionable insights for alpine wetland restoration using stress-resilient species.