Flower Bud Formation of <i>Cryptomeria</i> through the Action of Gibberellic Acid in Relation to Growing Conditions 4

It is well known that treatment of gibberellic acid on Cryptomeria is very effective to bear flower buds. But the number, the ratio on sexual differentiation and the development of flower buds borne through the action of gibberellic acid are varied by many factors controlling the growth. The author reported the effects of soil moisture, fertillizer and photoperiod in the previous papers of this series.<br> In this work, effects of gibberllic acid to the growth and flower formation were studied on the seedlings grown under different conditions in density and fertilizing. In the spring of 1961, 1-year-old seedlings of Cryptomeria japonica were transplanted and grown under different conditions given in Table 1. Foliar spraying of gibberellic acid were made in the next year.<br> The effect of density and fertilizer on the growth was obvious as shown from Table 2 to 6. The rate of growth of each seedling measured on height, diameter, length of branch, fresh weight of shoot and fresh weight of subterranean parts were arranged roughly to the following orders from larger to smaller; fertilized NPK>fertilized PK>not fertilized and sparse> medium> dense.<br> The role of gibberellic acid was decisive for the flower formation. No spray resulted no formation of the flower buds. From Table 7 it will be seen that the flower buds born through the summer spray abounded in made one and those through the fall spray in female one. But the ratio on sexual differentiation of the flower was varied with other growing conditions. Under the poor fertilizing conditions, flower buds decreased in number and consisted of only female one. As shown by Table 8, there was no bearing of the flower buds on the twigs, which were branched from the lower part of the stem and stunted under the shadows by vigorous growing upper parts, such as N_D MNPK. From these results, an existence of close relations between the growing conditions and formation of flowers was clear.