Phenols and bud dormancy I. Variations in total phenols and phenylalanine ammonia lyase activity in dormant buds of Fagus sylvatica L.

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Abstract
Quantitative analyses of the total phenols (glucosides and aglycones) and phenylalanine ammonia lyase (PAL) activity were determined separately in bud scales and the leaf primordia of dormant buds (apical, subapical and basal) of Fagus sylvatica L. until bud burst. In all the leaf primorida, the phenol and glucoside contents did not change substantially from November to March. From dormancy break to bud burst, phenols and glucosides accumulated in the subapical and basal buds. PAL activity, after a drop at the inception of dormancy, followed a trend similar to that of the total phenol content during dormancy. After dormancy break, the PAL activity of the apical bud was higher than that of the subapical and basal buds. During this period several differences were observed between PAL activity and phenolic content along the branch. No aglycones were detected during dormancy (except small quantities in the subapical buds). However, small amounts were detected in all three bud types after dormancy break. On the other hand, in the bud scales during the winter total phenols per bud, glucosides and PAL activity values (except in the apical buds) show a slight decrease. After dormancy break, PAL activity disappeared and aglycone levels increased slightly. At the same time it was not possible to determine any clear net variation in the levels of phenols and glucosides. It seems, therefore, that the inception and maintenance of dormancy in F. sylvatica buds cannot be correlated to the total phenolic pool and PAL activity in leaf primordia, while some kind of correlation seems to occur in the case of bud scales.