Correlation between occurrence of bloom on cucumber fruit and air temperature in a plastic film greenhouse

In order to obtain useful data on the relationship between occurrence of bloom and environmental factors in cucumber (Cucumis sativus) cultivation, the possible correlations of the bloom occurrence on cucumber fruit with air temperature and relative humidity were investigated using four different kinds of rootstock in a plastic film greenhouse. To determine the level of bloom occurrence, the bloom was removed from the fruit surface by cellophane tape, and then affixed to a black acryl-board. Next, the lightness of the tape was measured with a colorimeter as indicative of the level of bloom occurrence. The bloom lightness of cucumber fruit grown on the 'Hikari 3 gou P-gata' and 'Junsei Shintosa' rootstock was always higher than on the 'Unryu 2 gou' and 'New Super Unryu' rootstock. In the former two, there was a high correlation between the occurrence of bloom and the daily mean air temperature.