394 GROWTH FACTORS AND FLOWERING 



as in compensatory growth and attempts to elucidate the relation of 

 auxin to these two effects of axillary excision. 



MATERIALS AND METHODS 



Material and methods were the same as in Jacobs and Bullwinkel 

 (1953). Flowering was determined by checking the plants every day 

 for the first appearance of a macroscopic inflorescence at the distal end 

 of the main shoot. The inflorescences were recognizable while still very 

 small. In the first experiments the plants were checked only until all the 

 plants in one of the treatments had flowered — the data in Fig. 1 were 



100 



32 93 



PERCENT FLOWERING 



Fig. 1. Effect of excising all axillary shoots on the speed of flowering of 

 Coleiis plants which were small at the start of the experiment (pooled 

 data from 5 experiments). 



so recorded. For the later experiments, involving substitution of auxin 

 for the axillary shoots, we used the more precise method of determin- 

 ing average days to flowering (Fig. 3). (The early method gives arti- 

 ficially large separation of the treatments. ) 



RESULTS 



Confirmation was obtained of our previous reports that axiUary 

 excision causes compensatory growth and faster flowering of the main 

 shoot. Synthetic auxin can substitute for the axillaries in inhibiting 

 flowering, but has no detectable relation to the compensatory growth 

 effect. 



Excising Axillary Buds and Branches 



Four more repetitions of this experiment confirmed the previous 

 eight repetitions in showing that compensatory growth of the main 



