BIOCHEMISTRY OF PLANTS 



relative influence of climate and mineral nutrition of the plant on its 

 vitamin content. Also, the biochemical mechanisms in the plant that 

 result in the synthesis of essential amino acids, carbohydrates, and 

 higher fatty acids are of interest to students of both plant and animal 

 metabolism. Knowledge of the biochemistry of the plant is one of the 

 sources of information that constitutes a valuable asset to the plant 

 pathologist, the plant geneticist, the horticulturist, the specialist in 

 forestry, and indeed to all those who must of necessity come into contact 

 with plant systems of biochemical reactions, whether or not this is 

 consciously recognized. 



From some points of view, the plant offers, as compared with 

 the animal, methods of study with marked advantages. On the other 

 hand, there are disadvantages in the use of the higher plant for bio- 

 chemical investigation. The nature of a plant's growth is such that 

 most of its living cells perform the most diversified functions, a fact 

 which renders plant cells less suitable for research on specific bio- 

 chemical reactions. Tissues from animal organs often provide ma- 

 terial with specialized and highly intense activities suitable for the 

 investigation of enzyme reactions. It is doubtful that the plant in 

 general is as favorable as the animal for similar investigations, but this 

 view may be held only because fewer attempts have been made to 

 exploit the possibilities of plant material. There is no opportunity to 

 carry on with the plant the kind of experiments that are rendered 

 possible by the presence of a blood stream and organs of elimination. 

 The introduction of specific organic metabolites into the plant cell and 

 the study of their transformations within the cell involve special compli- 

 cations. In the examination of biochemical reactions taking place in 

 excised plant tissues, avoidance of bacterial and fungal contamination 

 often presents great difficulties. Further, the correlating eff"ects of 

 various plant hormones and of normal translocation of metabolites 

 make especially difficult the interpretation of the results of studies of 

 plant tissues in terms of the intact growing plant. 



Plants of the kind under consideration may be regarded as 

 normally complete synthetic systems, building up or breaking down 

 compounds representing an extraordinary array of organic structures 

 of biological interest, all derived from the simple substances required 

 for plant growth, namely, carbon dioxide, water, and inorganic ele- 

 ments to the number of fifteen or more. It might be postulated that 



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