Physiological and Biochemical Characteristics of Vegetative Buds of Siberian Larch Growing in the Conditions of the Middle Taiga Subzone of the Komi Republic

This paper includes the results of physiological and biochemical studies of L. sibirica vegetative buds in the taiga zone of the Komi Republic (Russia). The change in the phenological state of L. sibirica during the dormancy period and the transition to vegetative period is accompanied by a significant alteration of metabolism. In the autumn–winter period, the buds of L. sibirica synthesise a large amount of cryoprotective compounds such as soluble sugars, soluble protein, and free amino acids. During this period, the buds also contain a considerable quantity of unsaturated fatty acids (UFAs) (about 60% of the sum of all fatty acids (FAs)), mainly linoleic and oleic FAs. The beginning of the sap flow period is marked by a gradual increase in content of sugars and soluble proteins, which reach maximum values towards the end of April. The FA composition of the buds changed significantly. The content of UFAs decreased significantly and that of saturated FAs increased, indicating the activation of a FA synthase, the final product of which is palmitic acid. The water content and the share of freezing water in buds decreases to 45 and 16%, respectively, in December. The low water content and the presence of a significant fraction of nonfreezing water allows us to be certain about the development of quite sufficient cryo-resistance in larch bud tissues against low negative temperatures in the autumn–winter period. The biochemical changes in the buds adapting to low temperatures are primarily aimed at changing the state of water, whereby its phase transitions become relatively safe.