The influence of severe shoot pruning on growth, carbon and nitrogen status in young peach trees (Prunus persica).

One-year-old peach trees (Prunus persica (L.) Batsch) were severely pruned in July by removing 60% of the shoots. Tree responses were analyzed in terms of architecture and nutritional status. Tree growth was recorded from July to September by nondestructive (leaf production, thickening and branching of the remaining secondary axes) and destructive measurements (biomass partitioning and concentrations of total nitrogen (N) and nonstructural carbohydrates (NC) in specific tissues). The dry weights of pruned trees were lower than those of control trees at the end of the growing season (i.e., 2.5 months after pruning), whereas shoot:root ratios were restored to the initial values. Tree response occurred in two stages. During the first 24 days following pruning, the growth components of the remaining secondary axes were similar to the control, and new secondary axes were produced. During the next 17 days, increases in both diameter and branching of secondary axes contributed to the maintenance of pruned tree growth rate (similar to that of control trees) and restoration of initial shoot:root ratios. No significant effect of pruning was observed on NC concentrations, whereas N concentrations increased in several organs of the pruned trees during the first growth period. The transient increase in internal N availability contributed to the initiation of new axes and the restoration of a more functional biomass partitioning between shoots and roots.