68 THE FLOWERING PROCESS 



warm conditions. This response is also dependent upon the cold, and 

 thus there is an aspect of flowering in this species in which an induc- 

 tive effect can be observed. It seems reasonable to expect that this 

 response is related to endogenous gibberellins. 



2. Flower Formation in Bulbous Plants (17) 



Blaauw and his team of workers in Holland were primarily 

 interested in discovering the optimal storage temperatures and other 

 treatments which might be used to produce an abundant harvest of 

 commercial flower bulbs and then to insure the best growth, flowering, 

 and sometimes accelerated blooming of these plants after they were 

 turned over to the customer. Often very special treatments had to be 

 used, such as in the shipment of bulbs to the Southern Hemisphere. 

 Their approach was to carefully examine the internal morphology of 

 the bulbs during an annual cycle in the field (sometimes at the native 

 location) and during commercial production. Then they would 

 subject bulbs to accurately controlled storage conditions, still 

 observing changes in morphology, and finally bulbs were planted in 

 the greenhouse or the field and their ultimate growth and flowering 

 observed. Such a procedure has been going on for more than 40 

 years, and we now have available an extensive literature relating to 

 the subject. Of course, work has also been done in other laboratories, 

 especially during more recent years. 



Unfortunately, the work has been almost completely descriptive, 

 since this serves the ends of the supporting industry very well. 

 Relatively few attempts have been made to study the biochemical 

 changes taking place during flower formation or to formulate any 

 sort of theoretical scheme attempting to understand the nature of the 

 changes. Perhaps this is not so unfortunate after all, because we at 

 least have an extensive foundation of descriptive data for future 

 formulation of theory. 



A few generalizations are apparent from the work. Flower 

 formation in the bulbs is first dependent completely upon their size. 

 Bulbs which are too small will not respond. In some cases (e.g. tulip) 

 all leaf primordia are formed before flower formation, in other cases 

 (e.g. iris) the number of leaves formed before the flowers is variable, 

 and in other cases (e.g. hyacinth) leaf and flower formation may go 

 on simultaneously. All species studied showed optimal temperatures 

 for flower formation, and temperatures too high or too low either 



