chapter four 



Temperature 

 and Flowering 



Temperature affects all plant processes, and some temperature 

 interactions with photoperiodism have already been mentioned. 

 There are many plants in which flowering is either qualitatively or 

 quantitatively dependent upon exposure to near-freezing tempera- 

 tures, and it is largely with these that this chapter will deal. A few 

 other less well-defined relationships between temperature and 

 flowering will also be considered. 



VERNALIZATION: COLD TREATMENTS 

 AND FLOWERING 



It is evident from Chapter Two that photoperiodism provides 

 not only a convenient method lor controlling and studying flower- 

 ing in many plants, but also a basis for the explanation of many 

 seasonal phenomena. The same is true of low-temperature effects, 

 which play an important role in the life cycles of many temperate- 

 zone plants. Among the monocarpic plants, both biennials and 

 winter annuals are forms in which a cold treatment is required 

 before flowering can take place with optimum rapidity; in winter 

 annuals it can be given during germination to very young seedlings, 

 whereas biennials must first have made substantial growth. Many 

 perennials also, both woody and herbaceous, require cold treat- 

 ments each season to continue flowering. The ecological and adap- 



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