THE SYNTHESIS OF FLOWERING HORMONE 



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periods of different durations and at different temperatures from 

 5 to 35°C. Before and after the dark period all plants were kept at 

 the same temperature. The results are shown in Figs. 9-5 and 9-6. 

 Obviously the flowering process is highly temperature sensitive. We 

 can note, however, that the critical dark period was changed less than 

 30 min by temperature changes from 15 to 30°C. Even more 

 interesting is the observation that the initial slopes (part A of Fig. 9-2) 

 are essentially the same at the various temperatures from 15 to 30°C. 

 This would seem to indicate that synthesis of flowering hormone 

 during the first extremely active hours of the dark period is not 

 influenced by temperature. No satisfying explanation for this amazing 

 observation is presently available. One wonders if the so-called 

 "synthesis" during those active hours might not be some sort of 

 physical process such as release of previously made hormone from 

 something to which it is bound, or perhaps transport from one 

 location to another. The observation certainly merits further 

 investigation. 



Figure 9-5 

 Flowering as a function of night length applied at various temperatures. 

 Temperatures before and after the dark period were all the same (green- 

 house grown plants). Of the 42 measured points, only three do not lie 

 very close to the lines as shown. Data previously unpublished. 



Figure 9-6 

 The curves of Fig. 9-5 (without the points) converted so that Floral 

 Stage is shown as a function of temperature for different dark period 



lengths. 



