Root growth following defruiting improves peach tree water status

Tree growth and water status throughout the growing season and after fruit removal were studied in container-grown peach trees. Trees with fruit (F) and defruited (DF) trees were sampled destructively at bud break (8 March), I month after fruit removal (3 June), at harvest (6 August), and before leaf fall (15 October) to determine the mass of leaves, current season shoots, branches, trunk, and the entire root system. Tree water status was determined from the mid-day stem water potential (SWP) the day before each sampling date. Root growth in DF trees was greater than that observed in F trees, while the above-ground biomass was similar in DF and F trees. DF trees therefore had lower leaf:root biomass ratios than F trees throughout the fruit growing season. Environmental factors did not fully explain the seasonal variations in SWP. but there was a significant correlation between leaf:root biomass ratios and SWP. Reductions in leaf:root biomass ratios were accompanied by increases in SWP and, ultimately, DF trees, had higher SWP values than F trees in mid-Summer. Improvement in tree water status following fruit removal can be explained, in part, by additional root growth.