NUTRITION AND SEASONAL LIFE OF PLANTS 127 



plant involves the building of new living substances, the forma- 

 tion of new cells by innumerable cell divisions, and the expansion 

 of cells in the plant body by means of absorbed water. 



Respiration is also very active in germinating seeds and 

 growing plants, as can easily be demonstrated if germinating 



Transpiration Respiration Photosynthesis 



Cortex 



Phloem (food path) 

 \Xylem (water path) 

 Pith 



Absorption 



Water 



Sails-- 

 Oxygen' 



Respiratiort 



FIG. 63. The main physiological activities of a bean plant illustrated 

 diagrammatically 



seeds or growing seedlings of beans are placed in a thermos 

 bottle under proper precautions. A thermometer thrust among 

 them will quickly demonstrate the evolution of heat, which is 

 an index of the respiratory activity of the growing plant parts. 

 Photosynthesis and migration of foods. The leaves as they 

 unfold begin to absorb carbon dioxide and the energy of sun- 

 light. The roots also absorb water and soil salts, which pass up 



