370 GROWTH FACTORS AND FLOWERING 



inhibited elongation of the stems. The specific proportions of the two 

 compounds for mutual antagonism depend upon the photoperiod and 

 the stage of development of the plant on a specific photoperiod. Thus 

 far, the growth-regulating properties of the two compounds have been 

 antagonized in the first 2 weeks of short photoperiods; at different 

 proportions, mutual antagonism should be possible at any period of 



growth. 



Hastening of flower development is caused only by treatment with 

 gibberellin at the time the outer florets are showing color. Application 

 of gibberellin earlier during the short photoperiod induces elongation 

 of the stem but does not affect time of flowering. In contrast, the 

 period of maximum inhibition of growth and delay of flowering oc- 

 curred simultaneously when the plants were treated with Amo-1618 at 

 the start of short photoperiods. Treatment with Amo-1618 at the time 

 the outer florets were showing color inhibited the development of the 

 florets, but did not affect the time of anthesis as compared with that of 

 untreated plants. 



SUMMARY 



Mutual antagonism of gibberellin and a quaternary ammonium com- 

 pound (Amo-1618) on the growth and flowering of chrysanthemums, 

 short-photoperiodic plants, has been demonstrated. Gibbereflin by it- 

 self induces maximum elongation when applied in the third week of 

 short photoperiods; Amo-1618 by itself induces maximum suppression 

 of growth when applied at the start of short photoperiods. They are 

 mutually antagonistic when applied simultaneously in the approximate 

 concentration of 50-ppm solution of gibberellin to 500-ppm solution 

 of Amo-1618 four times in the first 2 weeks of short photoperiods. At 

 other times in the growth of the plant, different proportions of the two 

 compounds may be necessary to antagonize their growth-regulating 

 properties. 



REFERENCES 



Kurosawa, E. 1932. On certain experimental results concerning the over elonga- 

 tion of rice plants which owe to the filtrate got from the culture solution of 

 the "Bakanae" fungi. Kept. Taiwan Nat. Hist. Soc, 22, 198-201. (From 

 abstr.) 



