Independent leaf and root responses to autumn freezing in perennial herbs: Insights from cutting and transplant manipulations

Abstract Background Freezing resistance is a critical but often overlooked trait that influences growing season‐length and constrains plant distribution. A key limitation in its study is the prevalent reliance on excised tissues from cuttings, which bypasses whole‐plant physiology. Whether this approach biases results by disrupting leaf–root hormonal signaling has not yet been tested. Methods Here, we used a unique dual‐approach design comparing excised cuttings with intact transplanted individuals to directly test how sampling method affects the assessments of autumn freezing resistance in both leaves and roots. Results We detected no significant difference in autumn freezing resistance between the two sampling approaches. Roots, however, were significantly more vulnerable to frost than leaves. Although both tissue water content and carbohydrate levels were associated with freezing resistance, their interactive effect was significantly stronger in leaves, indicating divergent physiological stress‐response mechanisms between above‐ and below‐ground tissues. Conclusions Our study demonstrates that roots and leaves use distinct physiological strategies to cope with autumn freezing. This highlights the need to elucidate root‐specific mechanisms of freezing resistance, especially given the projected loss of insulating snow cover under climate change.