Bud vigor, budburst lipid peroxidation, and hormonal changes during bud development in healthy and moribund beech (Fagus sylvatica L.) trees

Despite meristem totipotency, epicormic branches from moribund trees produce buds with less vigor and increased lipid peroxidation compared to those of healthy trees. A better understanding of the factors governing bud vigor and development, and their underlying mechanisms is essential for management of broad-leaved stands, of which oaks and beeches are among the most important species. This study investigated possible differences in leaf bud vigor and development in healthy and moribund beech trees. Leaf buds on shaded branches found in the understory of a natural beech stand in Catalonia (NE Spain) were used for comparison. The vigor, extent of lipid peroxidation, and hormonal profile of leaf buds of healthy and moribund beech trees were investigated. Results showed less bud vigor in moribund trees than in healthy ones. In the former, there was increased lipid peroxidation at budburst. Although endogenous levels of gibberellins, cytokinins, and auxin were significantly influenced by bud development in both tree types, buds of moribund trees showed markedly different dynamics in the endogenous concentrations of auxin, abscisic acid and the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid. We conclude that moribund trees (a) are less efficient in producing new leaves, as indicated by less bud vigor and greater lipid peroxidation at budburst than healthy trees and (b) show a marked differential hormonal pattern during bud development compared to healthy trees.