W. F. Loehwing 347 



THE FLOWERING STAGE 



In reference to the initiation of reproductive processes, recent data 

 (/j, 18, 80, 96, 144, 145. 150) have confirmed and elaborated many older 

 observations to the effect that the phenomenon of synapsis or sporo- 

 genesis represents a turning point in nutritional metabolism (55, 56, 61, 

 65, 141). (a) In monoecious species such as corn, it has been observed 

 that the origin of staminate and pistillate organs is associated with a 

 transitory but systemic acceleration of anabolic over catabolic processes 

 including more rapid salt absorption and dry weight gains. (/?) Under 

 normal conditions the metabolic stimulus associated with synapsis is 

 brief and soon gives way to a reduction in anabolic processes during the 

 ensuing phase of blossoming or anthesis. The flowering phase is usually 

 characterized by a subsidence of anabolic activity as well as the inaugu- 

 ration of fundamental modifications (jo) and redistribution of organic 

 and inorganic nutrient components (11, 25, 40, 61, y8). Subsequent 

 events vary considerably among species, some of which, for example, 

 undergo no further elongation of the main axis following anthesis (//). 

 While there are important differences between plants of determinate 

 habit, such as grasses, and those of indeterminate habit, as in many 

 dicots, the subsidence in rate of stem elongation can, nevertheless, often 

 be taken as an index of the fact that reproduction is already under way 

 even though gross morphological evidence of floral parts is not yet 

 visible (j], 104). (c) The decline of anabolic activity associated with 

 blossoming gradually gives way to what is usually the final resurgence 

 of absorption of mineral nutrients and acceleration of organic synthesis 

 in vegetative tissues. This anabolic stimulus is associated with the fusion 

 of male and female nuclei in syngamy and the very early enlargement 

 of young fruits (22, 38, 95. 96, 144, 145. /50). 



From the standpoint of ontogeny, much could be said in favor of 

 beginning such a discussion with sexual fertilization or syngamy which, 

 after all, is the actual inception of the new plant. Such a procedure 

 would be justified not only by the chronological sequence of events but 

 by the fact that many environmental factors to which the growing 

 embryo is exposed prior to its development into a mature and dormant 

 seed can predetermine in considerable degree the course of ontogeny 

 subsequent to seed germination. 



