66 



THE FLOWERING PROCESS 



6 9 12 15 



T-- TFMPERATURE IN °C 



18 



Figure 4-4 



Sample curves showing hypothetical reaction rates as a function of 

 temperature for reactions with Qio values of 1.5 or 4.0. If the reaction 

 with Gio= 1.5 is considered to be reaction I in the formula in the text, 

 and the reaction with !2io= 4.0 to be reaction II, then the hypothetical 

 product B will be proportional to curve II minus curve I, as shown. 

 Compare the shape of curve B with Fig. 4-1 . 



might by definition identify B in the above formula with the vernaUn 

 of Melchers. Is the active fraction of the soak waters also vernalin ? 

 It seems possible, but too little work has been done to say. How about 

 substance E ? Here the evidence is surely in favor, but again more 

 work is required. 



What about the gibberellins ? In this instance enough work has 

 been done to allow the tentative conclusion that the gibberellins and 

 vernalin are not identical. But if the gibberellins are nevertheless a 

 physiological part of the flowering mechanism in some plants at 

 least, as the evidence also seems to indicate, where do they fit in the 

 above formula ? Apparently they do not fit, and so our formula must 

 be too simple. Certainly there is a great deal left to learn about the 

 biochemistry of vernalization ! 



