62 • Temperature and Flowering 



complicated by the fact that both short days and continuous light 

 favor flower initiation more than do long days in unvernalized 

 plants (Gott et al, 1955). A more clear-cut example of a vernalizable 

 SLDP is Campanula medium (see Doorenbos and Wellensiek, 

 1959), which has a qualitative requirement for either low tempera- 

 ture or short days before it can respond to long days. 



Although even in the above plants, vernalization generally has 

 to be followed by exposure to long days, CJirysanthemiim is not 

 the only plant in which it promotes a response to short days. 

 Junges (1958) found that short days following the vernalization of 

 a strain of Kohlrabi, Brassica oleracea var. gongyloides, a biennial, 

 promoted the subsequent flowering in long days and high tempera- 

 tures. Such results make it unwise to regard vernalization require- 

 ments as necessarily linked to any other environmental response. 



THE SEMANTICS OF VERNALIZATION: 



FURTHER EFFECTS OF TEMPERATURE 



ON FLOWERING 



A restricted definition of vernalization was given earlier, but 

 it is now time to acknowledge its fluidity. For one thing, the term 

 is so often misapplied to the breaking of bud or embryo dormancy 

 by low temperatures that it has become a mere jargon substitute 

 for "cold treatment"; this is deplorable, but perhaps too late to 

 mend. Even if one restricts its usage to effects on flowering, how- 

 ever, difficulties arise. It is clear enough how certain effects of near- 

 freezing temperatures on biennials and perennials are similar to 

 those on germinating winter annual seeds, and why the term 

 vernalization may well be used for both. As long as one is dealing 

 with an obviously inductive action on flowering of temperatures 

 low enough to prevent growth, the phenomena seem relatively 

 clear-cut. But when the same or very similar effects occur at 

 temperatures high enough to allow rapid growth, or are not induc- 

 tive, or interact with the conditions of light and darkness during 

 exposure, are they still vernalization? This is not simply a matter 

 of semantics; the point is that the influences of temperature on all 

 aspects of development are so manifold that "typical" vernali/a- 

 tion, as in rye or Hyoscyumus, probably is an extreme case of a 



