SEASONAL VARIABILITY OF LEAF APPEARANCE RATE OF PROLEPTIC AND EPICORMIC SHOOTS OF PEACH (PRUNUS PERSICA) GROWN IN NORMAL AND DEFICIT IRRIGATION TREATMENTS

Abstract

Much attention is devoted to understanding whole plant physiology and the architectural manipulation of peach tree canopies to optimize yield, minimize losses and to understand developmental responses to the environment. One method to visualize and understand plant physiological responses is to synthesize field data sets into mechanistically-based computer simulation models. The L-PEACH model is a functional-structural interactive plant model that simulates 3D peach tree architecture and carbohydrate flow and distribution. The construction of this virtual tree is based on metamers, repetitive subunits defined as node+leaf+axillary meristem+internodal segments. The rate at which metamers are added over the course of a field season is very important for modeling shoot growth rates but not well established experimentally. Additionally, the canopy is composed of several shoot types that behave differently. In this 2010 California field study, we investigated seasonal patterns of leaf appearance rates (LAR), the time interval between successive leaves, in normal and deficit irrigated treatments on both proleptic and epicormic shoots of mature de-fruited trees. Leaf appearance and leaf growth rate measurements were recorded three times per week from the beginning of the season in April to the end of the growing season in late September. LAR fluctuated over the course of the season and generally slowed as the season progressed. Epicormic shoots added leaves at a significantly faster rate than proleptic shoots in both water deficit and normally irrigated treatments. Although there was a difference in stem water potential between irrigation treatments, there were no significant differences in the LAR between water treatments.