Fatty acid composition of phospholipids in silver birch buds in the winter-spring period in Karelia and Yakutia

Changes in the fatty acid composition of phospholipids in buds during the winter-spring period (January–May) were studied in silver birch ( Betula pendula Roth) growing in Karelia and Yakutia. Phospholipids were isolated from total lipids using column chromatography, while fatty acids were separated through gas chromatography. The metrics for acyl-lipid desaturase activity were represented by the ratios of stearoyl- (SDR), oleoyl- (ODR), and linoleoyl- (LDR) desaturases. Our findings demonstrate that, regardless of geographical location, the predominant phospholipid fraction during the development of primordia within the bud consists of unsaturated fatty acids. During the period of exogenous bud dormancy, dienoic acids were the most prevalent; however, their share declined by the onset of the growing season, while the proportion of trienoic acids increased. These changes were accompanied by a slight rise in the double bond index. Conversely, the unsaturation index nearly doubled by March, with this change being particularly pronounced in Yakutia. Simultaneously, the SDR and ODR values were high, indirectly indicating the active involvement of ω9 and ω6 desaturases in maintaining the liquid-crystalline state of phospholipids. The LDR value in phospholipids was the lowest, yet it nearly tripled by the onset of the growing season in both Karelia and Yakutia. We hypothesize that the liquid state of phospholipids in the cell membranes of meristematic tissue in the buds of silver birch growing in Karelia and Yakutia during the winter-spring period is sustained by high desaturase activity, with the most significant response to temperature changes observed in acyl-lipid ω3 desaturase. Furthermore, through the course of evolution, silver birch in Yakutia has developed an additional mechanism that involves a pronounced reduction in cell and tissue water content, which also contributes to maintaining an ordered state of phospholipids and their functions, particularly when exposed to extremely low air temperatures and permafrost.