Studies on the photoperiodic sex differentiation in cucumber, Cucumis sativus L. II : Aging effect on the photoperiodic dependency of sex differentiation”

1. Using cucumber varieties, “Higan-fushinari” and “Sagami-hanjiro,” the experiments were carried out in the Phytotron to know the aging effect on the sex differentiation and the effect of SD and LD treatments. 2. Aging effect was examined by using the seedlings grown in continuous light and being treated with SD for 10 days at the different ages and observing the male nodes on the main stem which were brought about by SD treatment. 3. The influence of the treatment at the age of 2 leaves appeared at the portion extending from the 4th through 12th nodes along the main stem, and that decreased, in turn, with age and only a little influence could be observed when the treatment was given at the age of 5 leaves. 4. The portion of stem where influences of treatment were brought about did not always shift upwards along the main stem, but it lowered along the main stem from the upper part where the development of flowers advanced most. 5. The effect of number of cycles of photoperiodic treatment given and the effectiveness of LD or SD cycles were examined using SD- and LD-grown seedlings. “Higan-fushinari” was treated with SDs or LDs for 5 or 10 days at the age of 2 or 4 leaves. “Sagami-hanjiro” was treated with SDs or LDs for 5 or 10 days at the age of 4 leaves. 6. In “Sagami-hanjiro,” no difference in the effect between 5 and 10 days treatments was observed. In “Higaan-fushinari” the effect of 10 days treatment was greater than that of 5 days one at the age of 2 leaves. At the age of 4 leaves, however, the difference between them was not clear. 7. Effectiveness of SD treatments and that of LD ones were the same in “Sagami-hanjiro” and in “Higan-fushinari” at the age of 2 leaves. In the latter form at the age of 4 leaves, however, effect of SD treatments was greater than that of LDs. 8. From these results, considering together with those of the former paper, it is concluded that there could observe the photoperiodism in the sex differentiation of cucumber like in the flower formation in plants