Research Faculty and Graduate School of Agriculture, Hokkaido University, Sapporo, Japan.
Research Center for Global Agromedicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
Adv Exp Med Biol. 2018;1081:129-147. doi: 10.1007/978-981-13-1244-1_8.
Boreal trees possess very high freezing resistance, which is induced by short-day length and low temperatures, in order to survive severe subzero temperatures in winter. During autumn, cooperation of photoreceptors and circadian clock system perceiving photoperiod shortening results in growth cessation, dormancy development, and first induction of freezing resistance. The freezing resistance is further enhanced by subsequent low temperature during seasonal cold acclimation with concomitant changes in various morphological and physiological features including accumulation of sugars and late embryogenesis abundant proteins. The mechanism of adaptation to freezing temperatures differs depending on the type of tissue in boreal trees. For example, bark, cambium, and leaf cells tolerate freezing-induced dehydration by extracellular freezing, whereas xylem parenchyma cells avoid intracellular freezing by deep supercooling. In addition, dormant buds in some trees respond by extraorgan freezing. Boreal trees have evolved overwintering mechanisms such as dormancy and high freezing resistance in order to survive freezing temperatures in winter.
北方树木具有很高的抗冻性，这是由短日照和低温诱导的，以在冬季极寒温度下存活。在秋季，光受体和生物钟系统合作感知日照缩短，导致生长停止、休眠发育和抗冻性的首次诱导。随着季节性寒冷驯化的进行，低温的进一步降低会伴随着各种形态和生理特征的变化，包括糖的积累和晚期胚胎丰富蛋白的积累，从而进一步增强抗冻性。适应冷冻温度的机制因北方树木的组织类型而异。例如，树皮、形成层和叶片细胞通过细胞外冻结耐受冷冻诱导的脱水，而木质部薄壁细胞通过深度过冷避免细胞内冻结。此外，一些树木的休眠芽通过器官外冻结来响应。北方树木已经进化出越冬机制，如休眠和高抗冻性，以在冬季存活下来。
