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chapter seven t ^g e a nd Flowering 



In the growth of most plants from seed, an appreciable period 

 elapses before flowers are initiated even under conditions that 

 would cause rapid flowering in more mature individuals. This is 

 often expressed by saying that in order to flower a plant must 

 reach the stage of readiness or "ripeness-to-flower," the latter being 

 a rendering of Klebs's (1918) term Bliihreife. Put so abstractly the 

 concept seems merely circular, but it is not unique in this regard. 

 Dormancy often seems to be defined as a state in which growth 

 does not take place under conditions favorable in all respects— 

 except for that condition required to break "dormancy." However, 

 this merely illustrates the limitation of abstract statements since 

 the questions involved in both dormancy and ripeness-to-flower are 



quite real. 



The relationship of age or developmental stage to the ability 

 to flower is not well understood, and differs vastly from species to 

 species. The requirement for a considerable amount of vegetative 

 growth is particularly marked in woody plants; many trees do not 

 flower until at least ten years of age, and some "juvenile" phases 

 are characterized not only by inability to flower but also by growth 

 habits and leaf shapes differing from those of the adult phase (see 

 Sax, 1958a). In herbaceous species, similar events lasting a much 

 shorter time are often observed. 



Since plants differ so greatly in the speed with which they 

 become ripe-to-flower, and probably in the mechanism involved, 

 the concept itself has little use except to call attention to a whole 

 range of phenomena. In spite of this, an even more general concept, 



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