VARIATION OF TOTAL PHENOLIC CONTENT AND INDIVIDUAL LOW-MOLECULAR-WEIGHT PHENOLICS IN FOLIAGE OF MOUNTAIN BIRCH TREES (BETULA-PUBESCENS SSP TORTUOSA)

We studied seasonal and between-tree variation in the composition and content of total and individual low-molecular-weight phenolics (LMWP) in leaves of mountain birch trees (Betula pubescens ssp. tortuosa). Th e major phenolic compounds were chlorogenic acid, quercetin-3-O-beta-D -glucuronopyranoside, myricetin-3-O-(5-acetyl)-L-rhamnopyranoside, and 1-O-galloyl-beta-D-(2-O-acetyl)-glucopyranose. The content of total p henolics, as well as the sum of individual LMWP, varied only slightly among trees while variation in contents of individual LMWP was large. Concentrations of almost all phenolics decreased during the growing se ason but pairwise correlations between individual phenolics remained s imilar over the whole season indicating tree-specific LMWP profiles ov er the season. Among flavonoids, the between-tree component of variati on was 2.6 times as large as the seasonal component, while for variati on of nonflavonoids the between-tree component was larger than the sea sonal one. To explain the significant correlations within both flavono id and nonflavonoid compounds, we discuss the biogenesis of LMWP in bi rch leaves, as well as their ecological role.