To establish an efficient cultivation system for producing high-quality cucumbers (Cucumissativus L. cv. Kema), a comparison of cucumbers grown in soil culture and hydroponic solution culture with different nutrient levels was carried out. The hydroponically grown cucumbers were bitter compared with the cucumbers grown in soil. The maximum and minimum fruit productions were obtained at high and low nutrient levels, respectively. However, most of the cucumbers were bitter when they were grown at high nutrient level. The cucumbers had the lowest concentration of nitrate ion in the hydroponic culture solution with low nutrient level, and vice versa. Nitrate ions may cause bitterness in cucumbers by promoting nitrogen metabolism, which in turn favors the enzymatic synthesis of cucurbitacin C. From these results, we conclude that the yield of bitter cucumbers can be reduced by growing them in soil culture rather than in rockwool culture and in hydroponic solution with low nutrient level.

　To establish an efficient cultivation system for producing high-quality cucumbers (Cucumis sativus L. cv. Kema), a comparison of cucumbers grown in hydroponic solution culture with different fertilizers applied and nutrient media used were investigated. In the hydroponic solution culture, the cucumber s grown the application of chemical fertilizer were more bitter than the cucumbers grown with the application of organic fertilizer. The cucumbers grown in the chemical hydroponic solution by the deep-flow technique were bitter compared with the cucumbers grown in the hybrid hydroponic solutions (with chemical and organic fertilizers) with a solid substrate. The greatest number of harvested cucumbers was obtained in the chemical hydroponic solutions with a solid substrate, and the least number of harvested cucumbers was obtained in the hydroponic solution with organic fertilizer with a solid substrate. In hydroponics by the deep-flow technique, the cucumbers grown with the application of organic fertilizer had the lowest total phenol concentration, whereas the cucumbers grown with the application of chemical fertilizer had the highest total phenol concentration. The cucumbers grown using organic hydroponics by the deep-flow technique had the lowest nitrate ion concentration, whereas the cucumbers grown using chemical hydroponics by the deep-flow technique had the highest nitrate ion concentration. From these results, we conclude that the yield of bitter cucumbers can be reduced by the application of organic fertilizer in hydroponics rather than by the application of chemical fertilizer, and by the use of hydroponics with a solid substrate rather than by the deep-flow technique.

　The effects of immersion in aqueous 1-methylcyclopropene (1-MCP) solution on the ripening of bananas were investigated. Mature green bananas were immersed in water (control) or 0.1, 1, 10, 50, 100, or 1,000 μg (active ingredient) L^－1 aqueous 1-MCP solution for 10 min 2 days after the start of ethylene treatment (DASE) and stored at 20℃ in the dark. In the bananas treated in 50, 100, and 1,000 μg L^－1 1-MCP solutions, an increase in color score was suppressed, and the ratio of the brown spot area to the surface area increased slightly and remained low until 12 DASE. To investigate the effects of the duration of immersion on ripening, the bananas were immersed in100 μg L^－1 aqueous 1-MCP solution for 0.5, 1, 3, 6, 10, or 15 min or not immersed (control) 2 DASE and stored at 20℃ in the dark. In the bananas treated for 10 and 15 min, increases in the score and ratios were suppressed. The internal quality of the bananas immersed in 100 μg L^－1 aqueous 1-MCP solution for 10 min, which was effective and efficient in suppressing ripening, was similar to that of the control, and the edible period was prolonged by more than twofold. These results suggest that immersion of bananas in aqueous 1-MCP solution is a very practical postharvest application because of the easy availability of 1-MCP.