Foliar trehalose pretreatment alleviates physiological and metabolic damage of ‘Kyoho’ grape under low-temperature stress

Background Low temperature is a major abiotic stress that limits grape production in cooler regions. The cell membrane is the primary target of low-temperature injury, and the membrane lipid peroxidation chain reaction triggered by a burst of reactive oxygen species (ROS) drives the loss of membrane integrity and the rise in permeability. Foliar application of exogenous regulators such as trehalose is an effective measure to enhance plant cold resistance; however, the concentration-dependent effects of exogenous trehalose on grape cold resistance remain unclear. Methods One-year-old ‘Kyoho’ grape cutting seedlings were foliar-sprayed with trehalose at 50–250 mmol L −1 and, 24 h later, exposed to 0 °C for 7 d. Membrane integrity, reactive oxygen species, antioxidant enzymes and non-enzymatic antioxidants, osmotic adjustment substances, ion balance, and energy-respiratory metabolism indicators were measured, and principal component analysis (PCA) was performed. Results Compared with the unstressed control (CK), low-temperature stress severely damaged leaf cell membranes, markedly increasing relative electrolyte conductivity (REC) and malondialdehyde (MDA) content (p < 0.05), and disrupted intracellular ROS homeostasis, with significant elevations of hydrogen peroxide (H 2 O 2 ) and superoxide anion (O2 ·− ). Exogenous trehalose mitigated ROS accumulation and membrane lipid peroxidation in a hormesis-like, concentration-dependent manner: protection increased from T1 (50 mmol L −1 ) to a peak at T2 (100 mmol L −1 )—which significantly reduced REC, MDA, H 2 O 2 and O2 ·− relative to the low-temperature (LT) group (p < 0.05)—and declined at T3–T5, being largely lost at 250 mmol L −1 . The optimal 100 mmol L −1 treatment also enhanced enzymatic (SOD, POD, CAT) and non-enzymatic (AsA, GSH, soluble sugars, soluble protein, total phenols) antioxidant defenses, promoted energy-respiratory metabolism (CCO, NAD(H), NADP(H), respiration rate) and osmotic adjustment (soluble sugars, soluble protein, proline, glycine betaine), and maintained Na + /K + balance. PCA separated the 100 mmol L −1 group from LT, closest to CK, with the first two principal components explaining 68.9% of the total variance. Conclusion These findings indicate that an appropriate concentration of exogenous trehalose partially preserves membrane integrity and alleviates oxidative injury under low-temperature stress through coordinated regulation of antioxidant defense and energy-respiratory metabolism, providing a quantitative basis for the application of exogenous trehalose in cold-resistant grape cultivation.