( 1IAPTER VIII. 



SYNTH! STORAGE AND BREAKDOWN. 



Livi ells and the plants which they compose are characterised 



narkable chemical activity. They promote a great variety 



hemic. d transformations which collectively constitute the Meta- 



boli the plant. We shall consider first the constructive phases 



of plant metabolism. One of the most important properties of the 



green plant is its ability, when supplied with a few simple raw materials, 



elaborate or synthesise within its cells a great variety of organic 



sub- vhich are utilised in the further growth of the plant, and 



in other activity The raw materials, comprising carbon dioxide, 



and mineral salts, are said to undergo assimilation into the 



substance of the plant. In a study of the synthetic activities of the 



plant the process of Photosynthesis, in which sugars are elaborated 



from carbon dioxide and water, occupies a very prominent position 



and will now be considered. 



Photosynthesis. 



:m implies, photosynthesis is a constructive process in 

 which tli -nee of light is a necessary condition. It is of twofold 



importance to the plant, for not only is it an essential step in the 

 manufacture of carbohydrates for incorporation into new cell-walls 

 new proteins, but it is also a process whereby light-energy 

 derived from the sun is fixed and stored in the plant for future use. 

 This • n of solar energy occurs because the green plant is 



I with a mechanism for conducting the synthesis of sugars 

 from carbon < ; . and water, an energy-consuming reaction, at the 



CX] inlight. The amount of energy utilised, 



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