32 Gardening 



makes it possible for a plant to manufacture much food, 

 and the stem has in it " vessels " or bundles of long, 

 slender tubes that allow water and food materials to be 

 distributed throughout the plant. 



The plant as a whole. Thus we see that the roots, 

 stem, and leaves all work together to promote the life of 

 the plant as a whole. The roots anchor the plant and 

 supply water and minerals ; the leaves manufacture 

 sugar ; and the stem makes it possible for the plant to 

 display many leaves to the light and for water and food 

 to be carried where they are needed in the plant. Thus 

 roots, leaves, and stem each have a work to do, and the 

 work of each is necessary for the life of the plant as a 

 whole. 



Respiration in plants. All the living parts of a plant 

 breathe or respire. Like animals, plants take in oxygen 

 and use it in breaking down their foods. In this way 

 they obtain the heat and energy that they use in main- 

 taining their lives and in growing ; and like an animal, 

 a plant gives out carbon dioxid as a waste product 

 when it respires. 



Respiration is one of the most important life processes, 

 for it releases the energy that keeps a plant or an animal 

 alive. It may be compared to the burning of wood in a 

 stove or of coal in the fire box of an engine. Fuel is 

 consumed or combined with oxygen, and a gas (carbon 

 dioxid) is given off to the air. Heat and energy to do 

 work result from the chemical change. A plant does not 

 consume as much food as an animal that is actively mov- 

 ing about and doing work with its muscles. But a man 

 cannot live without taking in oxygen and burning food 



