EFFECTS OF PACLOBUTRAZOL ON PHENOLOGICAL CYCLING OF LOW-CHILL FLORDAPRINCE PEACH IN SUBTROPICAL AUSTRALIA

Low chill 'Flordaprince' peach trees were grown in subtropical Australia, either following two paclobutrazol applications to dwarf the trees, or nitrogen to invigorate them. Following blossom thinning, the number of fruits per tree was adjusted to give a uniform number of well-spaced fruits per tree. Paclobutrazol significantly reduced the competing spring shoot growth and resulted in earlier maturity of a greater crop of larger, better quality fruits. It also reduced the spring flush of root growth, but resulted in a greater autumn root flush. Stage 2 of fruit growth was slightly longer in the Vigorous trees, resulting in delayed seed and embryo growth and greater dry mass of the embryos. Starch reserves were shown to be greatest in the roots, followed by the trunk, shoots and leaves. The reserves dropped to their lowest levels during the stone hardening and fruit maturation stages, but rose after the end of shoot extension growth to reach a peak again by leaf fall. Leaf analysis showed that N, P and K concentrations decreased through the season, while Ca and Mg increased. There were significantly lower K, and higher Ca and Mg levels in paclobutrazol treated trees.