Possible Selection of Cucumber Cultivars Suitable for a Closed Hydroponics System by the Bioasay with Cucumber Seedlings.

The selection of cucumber (Cucumis sativus L.) cultivars suitable for closed hydroponics system was investigated using the bioassay of cucumber seedlings. In the experiments, cucumber cultivars were classified into four types. The first type was 'PI 169391' which showed intermediate sensitivity to growth-retarding substances in culture solutions used once for different cultivars and growth reduction was found in the culture solution used once for the same cultivars. The second type was 'Encore I' which showed high sensitivity in solutions for different cultivars and growth reduction was not found in solution for the same cultivars. The third type was Hokushin' which showed intermediate sensitivity in solutions for different cultivars and growth reduction was not found in solution for the same cultivars. The fourth type was 'Aodai' in which sensitivity was low in that of different cultivars and growth reduction was not found in that of the same cultivars. Thus, cucumber cultivars, in which growth reduction of the seedlings was less in culture solution used once for the same cultivars, were most suitable for culturing in closed hydroponics.