Integrated Analysis of Phenotypic, Physiological, and Biochemical Traits in Betula platyphylla Sukaczev Under Cold Stress Conditions

Betula platyphylla Sukaczev (white birch) is a cold-tolerant tree species native to northeastern Asia, valued for its ecological adaptability and economic utility. While its responses to various abiotic stresses have been studied, the physiological and biochemical mechanisms underlying its cold stress tolerance remain insufficiently explored. In this study, we investigated the effects of prolonged cold exposure (6 °C for up to 27 days) on key physiological and biochemical traits of B. platyphylla seedlings, including plant height, chlorophyll content, electrolyte leakage (EL), malondialdehyde (MDA), proline levels, and antioxidant enzyme activities (SOD, CAT, POD). Cold stress resulted in visible phenotypic changes, reduced growth, and significant declines in chlorophyll content, suggesting inhibited photosynthesis. EL and MDA levels increased with exposure duration, indicating progressive membrane damage and oxidative stress. In response, antioxidant enzyme activities and proline accumulation were significantly enhanced, reflecting a coordinated defense strategy. Correlation analyses further revealed strong associations among antioxidant enzymes, MDA, proline, and EL under cold stress. These findings advance our understanding of the adaptive responses of B. platyphylla to low-temperature stress and provide a physiological and biochemical basis for future breeding programs aimed at improving cold tolerance.