Studies on the growth behaviour of cucumber in controlled environments III

1. Cucumber variety“Higan-fushinari”which bore female flowers in longer photoperiods than 16 hours was grown in various photoperiodic combinations of white, blue, red lights, being of the same intensity of 0.04gcal/cm2, min., and darkness at the temperature of 28±1.5°C. The effects on the expansion of leaves, elongation and also on the sex differentiation were examined.2. In any light qualities, the longer the photoperiod was, the more the number of unfolded leaves became. In 16 and 8 hours photoperiod, it was the most in white and the least in blue light. In continuous illumination of a single light, number of unfolded leaves did not show variation. In that of photoperiodic combinations of various lights, it was much larger than that of a single light. This tendency was most prominent when the part of continuous light was given with blue light.3. In any light qualities, stem elongation was greater when the photoperiod was longer. In continuous light of a single light, blue light was more effective for elongation compared with others. In 16 hours photoperiod it was the greatest in white and the least in red light, and in 8 hours photoperiod it was the greatest in white and the least in blue light. In the continuous light of the periodic combinations of lights, the stem elongation was greater when plants were irradiated with blue light than with others.4. In any light qualities, flower buds were initiated. In general, they developed and the sexuality of flowers was distinguished at the higher nodes than 10th on the main stem. In a single light of red, no development of initiated flower-buds was observed and the sexuality of flowers was not distinguished. In continuous illumination and 16 hours of white or blue light, male flowers were observed at the higher nodes than 10th, but few female ones were observed. In 8 hours of blue light, only male flowers were observed at the very low nodes on the main stem.