172 



THE FLOWERING PROCESS 



Table 9-1. Compounds which Inhibit Flowering of Cocklebur, 



Arranged According to Their Effective Times 



OF Application — continued 



4. Time of Application: Determining the Step in the Flowering 

 Process Influenced by a Chemical 



When we find an effective compound, we must then determine 

 which step in the flowering process is being influenced. The way to 

 do this is to apply the compound to various groups of plants at 

 various times in relation to the inductive dark period. Usually 

 groups of plants are treated at intervals of two or more hours, begin- 

 ning at the start of the inductive dark period and continuing until 

 plants are examined 9 days later (during the last days, plants may 

 be treated only once each day). The Floral Stage at 9 days is plotted 

 as a function of the time when the compound was applied, producing 

 curves such as that in Fig. 9-10. Usually translocation (Fig. 9-1) 

 and development (Fig. 5-9) are measured in the same experiment. 

 Figure 9-11 and Table 9-1 summarize experiments with many 

 compounds. 



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