Water content, fractional composition of water, carbohydrate and fatty acid composition of lipids in renewal buds of <I>Hylotelephium triphyllum</I> (Crassulaceae) during overwintering

Renewal buds are a good model for studying growth, metabolism and bioenergetics under the influence of environmental factors (light, temperature). Such studies can provide new information about physiological, biochemical and molecular mechanisms of shoot growth at the stage of growth inside the bud under the influence of exogenous and endogenous factors. The paper contains the data on seasonal changes in energy metabolism, fractional composition of water, content of photosynthetic pigments, soluble carbohydrates, protein, and fatty acids in renewal buds of Hylotelephium triphyllum (Haw.) Holub. In the renewal buds formed in August, the total water content is about 85%, the share of water passing into the crystalline state – more than 90%, the temperature of the water-to-ice phase transition – −6°C. The intensity of respiration decreases, and the rate of energy storage, accumulation of soluble carbohydrates and unsaturated fatty acids increases gradually against the high water content and high proportion of unbounded water in plant tissues as long as the average daily temperatures decrease. There is a direct relationship between the respiration intensity, heat release, and energy storage. During the autumn-winter-spring period, the proportion of stored energy from the energy produced by respiration is about 40%. The formation of the photosynthetic apparatus of renewal buds is accompanied by a decrease in the rate of heat release and in the amount of stored energy. The swelling of buds proceeds simultaneously with an increase in the content of fatty acids, which indicates the activation their synthesis and coincides with the spring maximum content of chlorophylls and carotenoids. At this period, the total water content is about 75%, the proportion of water passing into the crystalline state – about 99%. The temperature of the water-to-ice phase transition is −4.7°C. This temperature value of ice formation is probably the minimum possible temperature at which irreversible damages to cellular structures occur in renewal buds. Consequently, the high water saturation in renewal buds of Hylotelephium triphyllum maintains metabolic processes and, as a result, favors the implementation of morphophysiological and structural rearrangements in them but also significantly increases the risk of damage by negative temperatures in low-snow winters.