EFFECTS OF CPPU (N-(2-CHLORO-4-PYRIDYL)-N-PHENYLUREA) ON FRUIT-GROWTH, MATURITY, AND STORAGE QUALITY OF KIWIFRUIT

Effects of the synthetic cytokinin CPPU (N-(2-chloro-4-pyridyl)-N'-phenylurea; common name forchlorfenuron) on kiwifruit (Actinidia deliciosa) cv. Hayward fruit growth, maturity, and storage quality were examined. CPPU was applied to fruitlets 21 days after flowering, either as a 5 mg/litre dip or as a 5 mg/litre spray. Dipping increased mean fresh weight of fruit at harvest by 43% and spraying by 33%. Most of the increase in fruit size was because of an increase in the volume of ''small'' isodiametric parenchyma cells in the outer pericarp. The volume of ''large'' ovoid parenchyma cells in the outer pericarp was not affected by CPPU treatment. CPPU application increased the rate of accumulation of soluble solids in fruit prior to harvest but did not increase the proportion of total dry matter. CPPU also caused increased growth of the outer pericarp at the stylar end of the fruit, resulting in small protuberances. Morphological attributes of fruit including the ratio of length to diameter, and flatness, were unaffected by CPPU treatment. Dipped fruit contained less tannin in the skin at harvest and appeared greener than untreated fruit at harvest and after storage. Fruit firmness was similar in treated and untreated fruit at harvest, and their rates of softening in storage at 0-degrees-C were similar.