Physiological studies of vegetative growth of Prunus persica: Preformation, neoformation, and epicormic sprouting in peach

Understanding the physiology of vegetative growth is important for the efficient management of peach (Prunus persica) orchards. The influence of bud position, cultivar, tree age, tree carbohydrate status, date, drought, and light exposure on number of leaf primordial in over-wintering vegetative buds was evaluated in a study performed growth in peach. The number of leaf primordial present per bud roughly doubled from approximately five to ten between leaf drop and bud break. Parent shoot length, number of nodes on the parent shoot, cross-sectional area of the parent shoot, bud position along parent shoot, and bud cross-sectional area were correlated with the number of leaf primordial. The number of leaf primordial was significantly different among varieties and tree ages at leaf drop but not at bud break. The limited preformation found at bud break indicates that shoots with more than about ten nodes are produces from neoformed growth. In a related experiment, the effects of crop load and early epicormic sprout removal on current and subsequent year distribution of vegetative growth among epicormic, long and short shoots were investigated using fruit thinning and green pruning treatments. Long and epicormic shoot dry weight (DW) was significantly affected. Stem properties were more affected by crop load than were leaf properties. The crop load treatments did not affect subsequent year vegetative growth of any shoot type. In a subsequent study, factors influencing the initiation and growth of epicormic sprouts including light exposure, temperature, trunk growth, date of green pruning, and tissue concentrations of non-structural carbohydrate (NSC), were investigated by topping young trees and placing shelter cages around them. Date of pruning, light exposure, node number present in the stump, estimated bark NSC were significantly related to the DW per sprout. Date of green pruning appeared to be the most important factor, leading to the conclusion that correct timing of summer pruning may reduce subsequent epicormic sprouting.