274 LEAVES 



and a part of the elements for all other plant substances. Not 

 only do the other plant substances derive all or a important 

 part of their constituents from the photosynthetic sugar, but they 

 derive from it their stored energy. 



As was learned in the study of photosynthesis, the stored 



energy in the photosynthetic food is sunlight transformed into 



chemical energy and stored in a latent form by the processes of 



photosynthesis. Into whatever compounds, such as starch, 



cellulose, proteins, etc., the photosynthetic sugar is transformed, 



the latent energy is simply transferred to these compounds and 



the more complex the compounds usually the more energy they 



contain. Like storage batteries the plant compounds are charged 



with energy that is released as active energy when the compounds 



are broken down into their elements. Since animals do not 



carry on the process of photosynthesis, all of their energy must 



come from that stored in the plant compounds which they eat, 



and thus indirectly from the photosynthetic sugar made by plants. 



Thus the photosynthetic sugar may be regarded as the founda- 



tional plant substance, furnishing constitutents for the other 



plant substances and also the energy needed in performing the 



life processes. 



The various chemical transformations in both plants and 

 animals whereby compounds are either built up or broken down 

 constitute metabolism and are said to be anabolic when construc- 

 tive and catabolic when destructive. The transformations of 

 substances and energy are the chief characteristics of life. 



The photosynthetic food is involved in the formation of numer- 

 ous substances but the chief ones are protoplasm, carbohydrates, 

 proteins, fats, and enzymes. Some of the minor ones are the 

 volatile oils, glucosides, alkaloids, pigments, organic acids, and 

 tannin. 



Protoplasm. It is in connection with protoplasm, the living 

 substance of both plants and animals that the transformations 

 of substances and energy occur. Within the protoplasm sugar 

 is synthesized by the chloroplasts, and it is protoplasm that forms 

 cellulose, starch, proteins, fats, enzymes, and the many other 

 kinds of substances. At the same time substances are being con- 

 structed in the protoplasm others are being broken into simpler 

 compounds, and as a result many kinds of substances are com- 

 monly present in the protoplasm. 



