This experiment was conducted to examine the effect of dichlorprop alone or in combination with calcium salts, calcium acetete or calcium hydroxide, on the fruit ripening in ´Tsugaru´ apples. Results were summarized as follows.
1. The application of 30 ppm dichlorprop alone forced fruit maturity by 20 days as compared by the untreated control. Total marketing period was greatly shortened due to the early softening of flesh.
2. Both of the calcium salts added in dichlorprop solution delayed fruit maturity. However, calcium acetate appeared to be more effective than calcium hydroxide, and maturity was suppressed more strongly at the concentration of 8.8 g/ℓ than that of 4.4 g/ℓ.
3. Five sprays of calcium acetate (4.4 g/ℓ) prior to the application of dichlorprop reduced 1-aminocyclopropane-l-carboxylic acid content, ethylene forming enzyme activity, internal ethylene concentration, and ethylene evolution, but did not greatly alter the maturity as compared with those of the separate applications.
Results indicated that maturity alteration by calcium in dichlorprop treatment may be associated with not only total calcium concentration in fruits but also changes of fruit response to the calcium in dichlorprop preparation or dichlorprop itself.
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