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 ina 
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 
