The effect of water deficit on ethylene biosynthesis of cucumber, eggplant and green pepper fruits was studied at 25°C and different humidities (20, 53, 80, 97%RH). Although none or little ethylene production was observed at high humidity, rapid water deficit at low humidity caused ethylene production following a decrease in three kinds of fruits. Elevated ethylene production of the fruits was also induced by rapid fluctuating humidity, and continued of a high level after transferring to high humidity. 1-aminocyclopropane-1-carboxylic acid (ACC) content, ACC synthase activity and ACC oxidase activity in peel and pulp of the fruits increased rapidly accompanyed by rapid water deficit in the fruit at low humidity. These results seem to indicate that rapid water deficit at low humidity is unfavorable in the view of keeping the quality of fruits and vegetables, because of accelerating their ethylene biosynthesis.

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A new method for estimating respiration rate of fruits and vegetables in a modified atmosphere package (MAP) was developed, using the tomato fruit as an example. On the basis of the measured data of the gas partial pressures in the package, the oxygen consumption rate and carbon dioxide evolution rate were determined by computer using the non-linear least-squares method. The free volume of the pouch with packed tomato fruit was also determined simultaneously in the computation. The estimated values of respiration rates for tomato fruit were 9-13ml/kg · hr at 20°C. These values agreed well with those reported Previously by several investigators. The phenomena that the package wrapped with fresh fruits and vegetables shrank during storage can be explained theoretically by the result dependent on computation that the free volume in the package was decreased with the passage of time. A new calculation method is useful for the estimation of respiration rate in modeling MAP under unsteady conditions.

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To investigate the effect of electric fields on the postharvest life of some fruits and vegetables, they were exposed to an alternating current high electric field (HEF) for short periods. The high electric field (430 kV/m) treatment on pears, plums and bananas in the preclimacteric period suppressed the respiration rate during the climacteric period. Similarly, a little effect on the respiration rate was also observed in the apples treated by HEF in a postclimacteric period. Physicochemical properties (i. e., °Brix, pH, hardness and Hunter 'Lab' values) of the bananas 17 days after the HEF treatment indicated that HEF treatment retarded ripening (1.5-2 days) as compared to the control. It was found that the exposure of HEF (0. 5-3. 0 hr) on green sweet peppers elongated its freshness/greenness Respira-and also reduced the percentage of fresh weight loss as compared to the control.

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The effects of pods on starch and sugar contents were determined to clarify the sugar metabolism of stored green peas (Pisurn sativum L., cv.Kishu-usui). The quality of peas stored with pods was maintained at a longer period than peas without pods. The total sugar content of seeds stored with pods increased after 2 days of storage at 1 °C, but seeds with or without pods, especially without pods, decreased significantly during storage at 20°C. On the other hand, the total sugar contents of pods stored with seeds at 1°C and without seeds at 20°C showed almost no change, but pods with seeds at 20°C decreased markedly. The starch content of seeds stored with pods at 1 °C showed almost no change, but seeds with or without pods at 20°C increased greatly. The accumulation of the starch content of seeds stored with pods was as high as compared with seeds without pods.

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