Plant metobolism 



9 



All organic compounds found in plants result from the complex of 

 reactions termed metabolism. These processes obviously must be ex- 

 ceedingly diverse to involve such a variety of substances. Although 

 knowledge of the reactions occurring is increasing rapidly, there is 

 still a vast amount to be learned. The complete story may never be 

 written and probably cannot even be approached for many years. Any 

 schemes drawn now must necessarily be tentative and subject to exten- 

 sive revision as work progresses. Yet the available information is 

 fundamental to an understanding of plant physiology and therefore 

 should be summarized in any book on general biochemistry. 



Fortunately, the metabolism of plants and animals is similar in 

 many respects, making it unnecessary to cover all the reactions in de- 

 tail for both kingdoms. The systems outlined below have not been 

 demonstrated for any single species but represent a combination of the 

 results from studies on a number of different plants. This treatment 

 assumes that a reaction observed in two or more species is widespread 

 and leaves the exceptions to subsequent work. Occasional errors have 

 proved embarrassing, but this approach has been satisfactory in gen- 

 eral. 



The metabolism of any given compound bears either a direct or 

 an indirect relationship to the metabolism of all the other compounds 

 of the plant. For convenience, however, the metabolites are grouped 

 into major classes. An attempt is made to indicate the interrelation- 

 ships between these groups of compounds. In addition, special atten- 

 tion is devoted to photosynthesis and carbon dioxide fixation, processes 

 rather characteristic of plants but not limited to them. 



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