Ethylene Production Rate: A Sensitive Indicator for Determining the Occurrence of Mechanical Stress in Tomato Fruits

Abstract

　Mechanical stresses, including impact stress, play an important role in changes of physiological, biological, eating, and appearance quality of horticultural produces. In this study, the effect of slight impact on the respiration and ethylene production of mature green tomato fruits was examined. First, to exclude changes in respiration and ethylene production derived from the climacteric during experiments, an attempt was made to accurately judge the ripening stage from the rate of ethylene production. No climacteric rises were observed at least within 48 h if the initial ethylene production was less than 8.2 nmol/kg/h. Tomato fruits, identified as mature green by this screening test, were dropped from 5 cm height for 1, 3, or 10 times. Their respiration and ethylene production greatly increased as a result of these very slight impacts when the fruits were dropped. Interestingly, ethylene production of the fruit was promoted by even a single drop from 5 cm, and the increase in ethylene production was more apparent than that of respiration. Moreover, 1-methylcyclopropene (1-MCP) treatment did not inhibit the increase in both of ethylene production and respiration rate caused by dropping the fruits 10 times. From these results, ethylene production seems to be the most predominant factor indicating the physiological change in tomato fruit which was treated with a slight impact, since the injury symptom is not always visible after the physical stress. The ethylene production rate, therefore, should be taken into consideration as one of sensitive indicators for determining the occurrence of mechanical stress in tomato fruits. Furthermore, ethylene production rate might be used as a basic screening parameter for selecting tomato fruits used in study of the effects of chemical and physical treatments on the metabolism and quality of postharvest horticultural produce.