THE WATER RELATIONS OF MATURE `SUNDROP' APRICOT TREES IN RESPONSE TO DIFFERENT VIGOUR CONTROL TECHNIQUES

Abstract

In the absence of dwarfing rootstocks for apricot, techniques which reduce vegetative growth are important in the orchard management system. A number of techniques may be employed to moderate vegetative vigour of fruit trees. In the orchard in the humid climate of Palmerston North, New Zealand, five-year-old vigorousSundrop' apricot trees on `Golden Queen' peach seedlings trained on Tatura trellis at 2000 tree ha -1 were used. The treatments were regulated deficit irrigation (RDI), dormant root-pruning, soil applied Paclobutrazol (PBZ) and untreated control. The objectives were to examine the effects of these treatments on the internal water relations of apricot. Also, to determine whether the mechanism of response to root pruning appeared similar to the mechanism of response to water stress. Throughout the season treatment effects on vegetative, reproductive growth and leaf physiology of the trees were monitored. Predawn and midday xylem water potential (Ψ xylem) in root pruned and water stressed trees were lower than in control trees, but Cultar treatments did not significantly affect this. PBZ treated trees had the same water status as controls. Root-pruned trees developed an increased internal water deficit in the leaves and fruits especially at the time of highest water demand during fruit stage III.