1959 Volume 28 Issue 4 Pages 277-287
1. Studies on the effect of some growth regula-tors on the floral initiation in spinach plants were carried out for the purposes of making easy the breeding procedure, and of obtaining a good product of seeds in certain slow bolting strains, such as the variety “King of Denmark”. The results obtained are as follows.
2. The application of MH (50 or 100 ppm in conc.) to the young seedlings resulted in the accele-ration of floral initiation, bolting and flowering, and also in raising a large amount of seeds. The plants treated with NAA (10 ppm in conc.) were more or less retarded, in turn, in their reproductive development compared with non-treated controls.
3. The application of Gibberellin (1_??_40 ppm in conc.) to the young seedlings during summer days showed a striking elongation of flower-stalks, but the floral initiation itself could not be induced at all. While the plants treated during autumn or winter months showed a remarkable acceleration of their floral induction. From these results with spi-nach plants, it might' be deduced that gibberellin can exert an effect equal to the so-called “vernalin”.
4. Different responses to the so-called chemical vernalization were detected with several chemicals. Gibberellin was the most effective one. One ppm of NAA was also quite effective to flower promotion, while 10 ppm of NAA had no definite effect. Maleic-hydrazide (50 ppm in conc.) used on the chemical vernalization showed a slight inhibitory effect on flowering.