1980 Volume 49 Issue 2 Pages 277-285
Physiological changes associated with the maturation of apples on the tree were investigated using three apple cultivars: Jonathan (medium maturing, short shelf life), Indo (late, intermediate shelf life), and Ralls Janet (late, long shelf life). Fruits were picked 5-13 times at weekly intervals during the maturing period, and changes in respiration (CO2 evolution), ethylene emanation, and internal ethylene concentrations were determined in relation to several criteria of maturation, such as fruit weight, titratable acidity, content of soluble solids, starch, water soluble pectin, total pectin, and firmness of flesh. The changes in amylase and pectin methyl esterase activities were also determined.
1. While a climacteric rise in respiration was clearly observed during maturation on the tree in Jonathan and Indo apples, it did not occurr in Ralls Janet apples until the normal harvest period. Ralls Janet apples, however, showed a typical climacteric rise both when they were stored at 20°C, or attached to the tree, far beyond the usual harvesting time until the time when most fruits had naturally dropped.
2. Internal ethylene concentration was found to increase two weeks before the climacteric onset of respiration, reaching a levels of 4ppm at the climacteric minimum in Jonathan apples. In Indo and Rails Janet apples, a range of 0.3-0.5ppm predominated from a month before the climacteric onset. A sharp increase was found almost simultaneously with the climacteric rise in Indo; in Ralls Janet, the increase occurred at the time of climacteric minimum, reaching levels of several ppm.
3. Rapid increases in ethylene emanation occurred almost simultaneously with the climacteric rise in Jonathan and Indo, but only a slight increase was observed in Rails Janet even after the increase in respiration and internal ethylene concentration.
4. The relationship between maturity and the change in respiration was also compared among the three. With Jonathan, maturation advanced rapidly and the fruit became edible at the climacteric minimum of respiration. Indo apples became edible after the rise of respiration; the fruits contained high levels of starch and total pectin, and their decomposition progressed slowly. With Ralls Janet, while maturation advanced slowly, the rise of respiration occurred very late, and the climacteric peak was found a month after the fruits were edible.
5. Respiration rates and internal ethylene concentrations in Ralls Janet apples were much lowr than those of Jonathan and Indo apples through the pre-and post- climacteric phases. This fact seems to be related to the fact that Ralls Janet apples have a longer shelf life in comparison with the other two cultivars.