The effect of gibberellic acid upon the flower bud formation is affected by other factors controlling the growth. In this paper, foliar spraying of gibberellic acid was made on 1-year-old seedlings of Cryptomeria japonica which were grown under the conditions in Table 1.
The growth of the seedlings was affected by each treatment as shown in Table 2. The values of fresh weight of the seedlings on October, nearly the end of growing season, were arranged to the following order from the heavier to the lighter; fertilized>not fertilized, long day>natural day>short day and no spray of gibberellic acid_??_spray in the fall>spray in the summer. In addition, the effect of gibberellic acid appeared on the form of the seedlings. As shown by photograph 1, the appearance of seedlings treated with gibberellic acid was less stout in comparison with those belonging to no spray.
To flower bud formation, the role of gibberellic acid seemed to be decisive. No spraying of gibberellic acid resulted no formation of flower bud. The ratio in the number of the female flower to the male flower varied with time of the spraying. Table 3 shows that the flower buds born through the summer spray abonnded in male one and those through the fall spray in female one. The extent of seasonal change in the ratio of the sexual differentiation of flower bud was affected by other conditions related to the growth. Under the unfavourable conditions for growth, such as D_SM₀ in Table 3, extreme change in the ratio occured between G_s and G_F.
The time at which existence of flower buds became possible to observe by the naked eye, was delayed by long day conditions. The size of flower buds differed with different photoperiod as shown by Table 4 and photographs 2 to 4. It is very interest that the rate of development of the flower buds was stimulated by the unfavourable photperiodic conditions to the growth of entire seedlings.