SEASONAL CHANGES OF IAA AND CYTOKININ IN SHOOTS OF COLUMNAR TYPE APPLE TREES

Changes of endogenous indole-3-acetic acid (IAA), cytokinin and cytokinin composition were investigated in shoots of 'Maypole' and 'Tuscan' columnar type apple trees, and 'McIntosh' normal type apple trees. The changes of IAA, cytokinin and cytokinin composition depending on growth stages in columnar type trees resembled those of 'McIntosh'. Columnar type trees generally showed higher endogenous IAA and cytokinin concentrations than those of normal type trees, and these concentrations were higher in 'Tuscan' which has intense columnar growth habit amongst columnar type cultivars. The ZR ratio was higher in columnar type than in normal type trees. Results suggested that these differences affect specific shoot growth in columnar type trees such as the production of many spurs, shoot elongation continuing through to autumn, and thickened shoots.