THE SYNTHESIS OF FLOWERING HORMONE 



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DAYS AFTER BEGINNING OF INDUCTION 



Figure 9-1 



Three translocation curves obtained by defoliation of plants at various 

 times following a 16-hr inductive dark period. Times of defoliation are 

 shown, and all plants were examined on the ninth day. The lines above 

 the numbers on the abscissa represent noon of the indicated day and the 

 bar on the abscissa indicates the inductive dark period. Approximate 

 times when half the stimulus was out of the leaf are indicated by the ti. 

 The figures represent half times after beginning of the dark period, and 

 the figures in parentheses represent half times after end of the dark 

 period. Dates refer to the day plants were placed in the dark treat- 

 ment. Plants represented by the ri=46 hr curve were kept under 

 2000 ft-c of fluorescent light in the growth chambers (23 X). Growth 

 chamber data are previously unpublished. 



the inductive dark period no hormone (or an ineffective amount) had 

 been transported out. Thirty-five to sixty hours later, all of the 

 hormone had left the leaf and was now in the stem on the way to the 

 bud. This is an excellent experiment to consider in light of the dis- 

 cussion of Floral Stages in Chapter 5, because we must assume that 

 Floral Stage after 9 days is a function of how much hormone reached 

 the tip. In this experiment, as well as in the night-length experiment 

 (see below), the assumption seems reasonable. 



