CHAPTER XVIII 



METABOLISM— DIGESTION— TRANSLOCATION— GROWTH 

 Interrelationship of Organs. — Tke higher plant is a very 

 complex organism, consisting of many types of cells and tissues, 

 of systems and organs. These organs serve many ciomplex 

 physiological functions in the life history of the plant and are 

 interdependent upon each other. Water is absorbed by the roots, 

 and transported through the stems to the aerial parts, vs^here a 

 part of it is used for the making of foods and a part given off 

 by transpiration. The water carries the minerals which are 

 also' used in the making of food and the soluble foods to various 

 parts of the plant for use or storage. The stems serve for trans- 

 portation and other purposics. The leaves serve for photosyn- 

 thetic and other food-making processes and for transpiration. 

 The flowers serve for reproduction. Therefore, it is very evident 

 that an equilibrium must exist between the various parts of the 

 plant if it is to perform its functions to the best advantage. 



Metabolism. — Having studied the taking in of water and the 

 various raw foods which it carries in solution, the transpiration 

 of water, the taking in of carbon dioxide, and photosynthesis, 

 we vvdll now turn our attention to the complex acti'vities of the 

 plant which involve growth. All the above processes must pre- 

 cede or accompany growth, which involves the utilization of 

 grape sugar and other true food compounds which are manu- 

 factured by the plant. These true food compounds are used 

 directly in the making of protoplasm, or they may be stored for 

 the tiine and tised later. 



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