196 COLLEGE BOTANY 



the process involves chlorophyll, water, carbon dioxide, sun- 

 light and a suitable temperature. The action of the sunlight 

 on the chlorophyll results in the decomposition of both the 

 water and carbon dioxide (H 2 O and CO 2 ) and the formation of 

 carbohydrates. The final result of this process is the formation 

 of sugar or starch and the elimination of oxygen. This process 

 may be expressed as follows : 



6H 2 O + 6CO 2 = C 6 H 12 O 6 + 6O 2 



(Water) (Carbon (Glucose) (Free 



dioxide) oxygen) 



The liberated oxygen passes out through the cell walls and 

 thence out through the stomata, where it becomes a part of the 

 atmospheric oxygen. 



However, it should be remembered that the formation of 

 glucose (grape sugar) from H 2 O and CO 2 is not a direct process, 

 but is the final result of a number of intermediate processes 

 which are very complex and not well understood. However, 

 these higher carbohydrates, such as glucose and starch, are the 

 firstvisiblewell-defined carbohydrate products of photosynthesis. 



Photosynthesis probably begins with the dissociation of the 

 elements which compose water and carbon dioxide. This re- 

 quires a great deal of energy, and does not occur in nature, 

 except in the presence of chlorophyll when acted upon by sun- 

 light. This energy is not lost but stored up as latent energy in 

 the form of sugar or starch and is available when these com- 

 pounds are reduced to water and carbon dioxide. This latent 

 energy is available for future use by the plant, for use by animals 

 which feed upon plants and becomes very evident in the form 

 of heat and light when plant materials are used for fuel. TJiere- 

 fore, the chlorophyll utilizes the energy from the sun and makes 

 life possible on the earth. 



