238 ORGANIC AGRICULTURAL CHEMISTRY 



Chlorophyll Bodies and Chlorophyll. — This power of plants 

 to utilize the energy of the sunlight is dependent upon the 

 action of certain bodies known as chloroplasts or chlorophyll 

 bodies. These chlorophyll bodies have associated with them 

 a green pigment known as chlorophyll. It is this chlorophyll 

 which gives to the aerial parts of plants their green color 

 and which characterizes them as green plants. Much has been 

 learned of late years in regard to the chemical character of 

 chlorophyll, but its exact nature is still a question, and it will 

 not be desirable to enter into any discussion of it here. 



These two agencies always act together, the chlorophyll as 

 the assimilatory pigment, and the chloroplasts as the mechanism 

 of assimilation. Thus through the action of the chlorophyll in 

 its relation to sunlight some of the energy of the sun is used by 

 the chlorophyll bodies in bringing about a chemical reaction of 

 endothermic character which results in the synthesis in the 

 plant of complex organic compounds which have stored up in 

 them as potential the kinetic energy derived from the sun. 

 These compounds then become the energy food of the plant 

 itself. Because light is necessary for this synthesis it is known 

 as photosynthesis. The simple compounds involved in this photo- 

 synthesis are carbon dioxide and water. The former is present 

 in the atmosphere and the latter in both atmosphere and soil. 



Products of Photosynthesis. — We have stated that the 

 final products of this synthetic reaction are carbohydrates, fats 

 and proteins. We can ask, however, what is the first or direct 

 product? This question we are unable to answer definitely. 

 We do not know positively what individual compound is first 

 formed by this synthesis, nor can we even state absolutely 

 whether it is carbohydrate or fat or protein. 



We have written the endothermic reaction for the production 

 of glucose from carbon dioxide and water as : 



6 CO2 + 6 H2O + energy -> CeHisOe + 6 O2 



This is the reverse of the exothermic reaction whereby glucose 

 is oxidized to carbon dioxide and water with the liberation of 



