メロン果実の貯蔵に関する研究 (第2報)

Abstract

The changes of respiration rate and ethylene production of melon fruits in the course of ripening after harvest were investigated with reference to cultivars and harvest maturity. Four cultivars of melon fruits of Raifu, Prince, Elizabeth, and Honey King were harvested at different stages of maturity and stored at 20°C.1. All of the Raifu melons harvested at three different ages of 28, 32, and 34 days after anthesis showed a typical climacteric pattern of respiration. Ethylene production changed in parallel with respiration rate during the course of the climacteric, and the time of the peaks of both coincided, however, a little but definite increase of ethylene production was detected prior to the onset of respiration rise. The older the age at harvest time became, the sooner the peaks of ethylene and respiration appeared, and the greater the magnitude of ethylene peak became.2. Prince melon did not show the typical and complete climacteric pattern of respiration, but there was a rise of ethylene production without corresponding rise of respiration. The early-harvested fruits, 21 days after anthesis, showed a climacteric-like rise of respiration, but the time of the increase did not coincide with that of ethylene production. The fruits harvested 24 days after anthesis showed a trend of gradual decrease of respiration, but did a rise of ethylene production shortly after harvest.3. Elizabeth melons showed a similar change to those of Prince melons, that is, while respiration rate decreased gradually throughout the experimental period, ethylene production exhibited a peak 3-4 days after harvest.4. In Honey King melons, the respiratory pattern was a monotonous drift downwards. Ethylene production in the fruits harvested 40 days after artificial pollination was slightly detected only when the fruits reached to a senescent stage, and that in the fruits harvested 55 days after pollination occurred at a very low level through approximately 10 days after harvest, and did not at progressive stage of over-ripe. Abnormally softened fruit called as “fermented fruits” showed a rise of respiration rate with a corresponding rise of ethylene production and tissue breakdown.5. It is supposed that the striking difference among cultivars in the respiratory pattern of harvested fruits would relate to the ripening characteristics and the storage life of these fruits. Prince, Elizabeth, and Honey King melons have a comparatively good shelf life and they attain ripening gradually without an appreciable respiratory peak, while in Raifu melon having poor shelf life ripening occurs rapidly with a climacteric rise of respiration.