INTRODUCTION TO 



BIOCHEMICAL 



SYSTEMATICS 



If there are any biologists who deny the evolution 

 of metabolic pathways in plants, they must certainly 

 constitute a small minority. At our present state of 

 knowledge the evolution of metabolic pathways 

 may be considered axiomatic. It is self-evident that 

 certain fundamental pathways such as those in- 

 volved in energy transfer and the synthesis of basic 

 protoplasmic constituents appeared before the seed 

 plants evolved, probably even before the origin of 

 cellular organisms. However, there are numerous 

 plant components, broadly classified as secondary 

 substances, which have undoubtedly evolved late 

 in the evolutionary progression. Pertinent questions 

 concerning each of these substances are related to 

 when and in what group of plants they first occurred 



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