330 GROWTH FACTORS AND FLOWERING 



case was the discovery by Gregory et al. (1954) that photoinduction 

 causes a spectacular increase in the dark fixation of CO2 in the short- 

 day plant Kalancho'e blossfeldiana. The parallelism between this 

 change and the progress of photoinduction is such as to suggest a close 

 relation. However, an analysis of the products of induced and non- 

 induced CO2 dark fixation did not reveal any significant differences 

 (Kunitake et al, 1957). The level of CO2 dark fixation and metabo- 

 lism in an induced Kalancho'e plant is raised, but this rise is one across 

 the board; no part of the existing system seems to be favored above the 

 other, and there is no evidence that a new pathway of CO2 metabolism 

 is established. This does not exclude a causal relation with flowering, 

 but it is not clear, if such a relation does exist, at which point CO2 

 dark metabolism and the processes of flower induction are linked. 



After thus having down-rated the more direct efforts at penetrating 

 into the biochemistry of flower formation, I might be expected to up- 

 rate the auxin and gibberellin approaches by showing that they have 

 done the trick and, logical or not, have crashed the gate into that 

 fascinating field. But I am afraid it would be too sanguine to make 

 such a claim. A skeptic might even summarize the status of these 

 approaches by saying, there is much to talk about and little to say 

 concerning the influence of auxin on flower formation, and there is 

 little to talk about concerning the influence of gibberellins — and 

 likewise little to say. However, at least gibberellin does produce 

 dramatic effects on flower formation in certain types of plants, and it 

 is reasonable to assume, as a working hypothesis, that gibberellin-like 

 materials play a part in the biochemical events that underhe flower 

 formation. But what part this is remains for future work to determine. 



AUXIN 



Influence of Auxin on Photoinduction in Short-Day Plants 



The influence of auxin on photoinduction was first noted about 20 

 years ago. In 1937, Dostal and Hosek reported that flower formation 

 in long-day-grown cuttings of Circaea lutetiana, a long-day plant, is 

 delayed by auxin treatment; in 1938, Hamner and Bonner showed 

 that the flower-inducing effect of a long dark period in Xanthium, 

 a short-day plant, is greatly reduced by simultaneous auxin applica- 



