Physiological and Multi-Omics Insights into Drought Adaptation of Poacynum hendersonii Seedlings Under Different Water Deficit Regimes

This study used Poacynum hendersonii (Hook. f.) Woods. seedlings as experimental material. A soil drought group (gradual soil drying) and a PEG-simulated drought group (15% PEG-6000 treatment) were established. By combining physiological measurements, metabolomics, and transcriptomics, we investigated the physiological and molecular mechanisms of P. hendersonii in response to drought stress. The results showed that under drought stress, P. hendersonii alleviated oxidative damage by activating the antioxidant enzyme system (catalase, CAT; superoxide dismutase, SOD; peroxidase, POD), and enzyme activities recovered significantly after rehydration. In the osmotic stress group (PEG), hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents increased significantly in the later stages, whereas membrane damage was milder in the soil drought group. Metabolomics analysis revealed significant enrichment of starch and sucrose metabolism pathways during early drought, shifting to unsaturated fatty acid biosynthesis and carbon metabolism in later stages. PEG-simulated drought specifically induced the accumulation of arachidonic acid, which may be associated with ferroptosis-like processes, although direct evidence is lacking. Transcriptomics analysis identified 23,623 differentially expressed genes (DEGs), with transcription factor families such as bHLH, MYB, and NAC playing key roles in drought response. Weighted Gene Co-expression Network Analysis (WGCNA) further revealed gene modules significantly correlated with physiological traits, indicating that enhanced respiratory metabolism (glycolysis, tricarboxylic acid (TCA) cycle) is an important strategy for P. hendersonii to adapt to drought. The study also found that while PEG-simulated drought could simulate the physiological effects of soil drought, significant differences existed in molecular pathways, particularly during later stress stages. This research provides a theoretical basis for elucidating the drought resistance mechanisms of P. hendersonii and offers potential targets for crop drought resistance breeding.