THE SYNTHESIS OF FLOWERING HORMONE 



169 



the antimetabolites which inhibit flowering, there is a test. The 

 inhibitor is simply applied in the presence of the suspected meta- 

 bolite. If as the concentration of metabolite is increased the inhibi- 

 tion decreases, then we can feel fairly certain that the metaboUte is a 

 part of the flowering process. Such an experiment is illustrated in 

 Fig. 9-9. There are some complications here, too, but the test is 

 basically a good one. 



60n 



50 



u 4-0 

 o 



< 



_j 30 + 

 < 



o 



il* 2-0 



l-O- 



I 2345 6 789 



DAYS AFTER INDUCTION (time of treatment) 



Figure 9-10 

 Effects on flowering of a representative metabolic inhibitor (2,4- 

 dinitrophenol) applied at various times in relation to a single 16-hour 

 inductive dark period. The translocation curve is obtained by defoHa- 

 tion at various times (see Fig. 9-1) and the development curve is 

 obtained by examining buds at various times after the inductive dark 

 period (see Fig. 5-9). Except for the development curve, all points 

 represent Floral Stage of plants examined 9 days after induction (as is 

 the case for virtually all of the cocklebur figures in this book). Data 

 from F. B. SaUsbury, 1957, Plant Physiol. 32, 600-608. 



Actually, there are some technical problems in discovering eff"ective 

 compounds in the first place. Is it possible, for example, that a com- 

 pound which is applied at the beginning of the dark period might 

 be ineffective, whereas it would be effective if it were applied at some 



