Studies on the postharvest physiology and storage of citrus fruits

I. Changes of respiration and ethylene production of some citrus fruits picked at different stages of development

Abstract

Changes of respiration and ethylene production of Satsuma orange (Citrus unshiu MARCOVITCH, cv. Ishikawa) and Natsudaidai (Citrus Natsudaidai HAYATA) picked at different stages of development were determined at 22±1°C.
1. Respiratory patterns of young, small Satsuma oranges were similar to those displayed by tipical climacteric fruits. The height of the respiratory rise was decreasing during development of fruits. Young Natsudaidai fruit did not show the clear climacteric like rise of respiration after harvest.
2. The initial respiratory rate of 22±1°C of detached Satsuma orange and Natsudaidai fruits decreased during development.
3. A dramatic increase in ethylene production was observed in small and young Satsuma orange after certain lag period during storage at 22±1°C. The rise in ethylene production was after 4 days in the fruits picked on 24th in July, after 6 days in the fruits picked on 24th in August, and after 14 days in the fruits picked on 24th in September, respectively. The rise in ethylene production was not accompanied by the rise of respiration and by abscission of stem end.
4. The rate of ethylene production at 22±1°C of Satsuma orange picked on 24th July (fruit weight 12.9g) was larger than those of fruits picked on 24th in August (fruit weight 39.7g) or in September (fruit weight 89.9g).
5. Respiratory rate at 30°C of tissue slices of peels or of pulp vesicles prepared from the Satsuma oranges picked at early in August was higher than those of fruits picked at early in September or in October.
6. Ethylene production rate by cut fruits (1/2, 1/4, 1/8) increased after 2-3 hours after cutting. By increasing the surface of cutting area, ethylene production was increased and its ratio was in proportion to the surface area. The rate of ethylene production from cut surface was 347-394mμl/cm²/25 hours.