Adaptation strategies of temperate fruit and nut trees to freeze-thaw cycles: Hydraulic dynamics and recovery mechanisms

• Freeze–thaw cycles induce embolism with species-specific recovery capacity. • Narrower xylem conduits increase safety but limit water transport efficiency. • Soluble sugars and water content facilitate embolism repair after winter. • Conduit-related traits guide cultivar selection for cold-resilient orchards. • Frost fatigue lowers embolism resistance across temperate fruit tree species. Frequent freeze-thaw cycles, intensified by climate change, impose substantial stress on temperate deciduous trees by inducing xylem embolism and disrupting water transport. However, their effects on the hydraulic functioning and recovery mechanisms of fruit and nut trees remain insufficiently understood. In this study, we investigated four species—walnut ( Juglans regia ,W185 and XX2), apple ( Malus pumila , HFS and WL), apricot ( Prunus armeniaca, DGX and XBX), and plumcot ( Prunus simonii , KLD and WD)—in southern Xinjiang over one winter and summer season (2023). We assessed xylem hydraulic traits, anatomical structures, non-structural carbohydrates (NSCs) dynamics, and branch water content to elucidate mechanisms of freeze-thaw-induced hydraulic disfunction and recovery. Key findings include: (1) freeze-thaw cycles significantly reduced specific hydraulic conductivity (Ks) and increased percentage loss of conductivity (PLC), with pronounced differences among cultivars and across sampling times; (2) W185 and XX2 exhibited greater hydraulic recovery by March, coinciding with higher soluble sugar concentrations and branch water content; (3) PLC was positively correlated with conduit diameter and embolism vulnerability (P50, P88), whereas narrower conduits conferred greater hydraulic safety; (4) all cultivars experienced frost fatigue, evidenced by reduced embolism resistance (P50) during winter; and (5) recovery of hydraulic function was strongly associated with NSCs mobilization and water status. These results advance our understanding of the structural and physiological responses of fruit trees to freeze-thaw stress. For an applied perspective, selecting cultivars with narrower vessels or enhancing NSC availability during late winter may help mitigate freeze-induced damage. In breeding programs, targeting xylem traits that facilitate embolism repair can improve cold resilience. This study provides practical guidance for climate-adaptive orchard management under increasingly variable winter conditions.