How Plants Live a3 
in his body, even though he lie entirely motionless ; and in 
like manner a plant must respire to keep up its life. 
Supplying the needs of plants. From our studies thus 
far we see that four of the great needs of a plant are air, 
light, water, and mineral salts. Most garden work is 
done in order that these four needs of the plant may be 
met so that it will live and make the best growth. In 
later chapters we shall learn in some detail how gar- 
deners make conditions favorable for the growth of their 
plants. 
Questions 
Name some of the principal needs of plants. State a few of the 
gardener’s tasks in caring properly for his plants. How did our 
ancestors learn to grow plants? What advantages does our 
modern knowledge give us in caring for plants? 
Name the parts of a typical garden plant. Tell how far the 
root systems of certain plants extend. Does a plant have any 
prominent parts, such as roots or leaves, that are not useful to the 
plant? What is the function (work) of the roots? Of the leaves? 
Of the stem? 
What is respiration? What do plants obtain through respira- 
tion? What waste product is given off when a plant or an- 
imal respires? To meet what needs of plants is most garden work 
done? 
Things to Do and Observe 
1. To note the extent of the root system of a young plant. Select 
a young plant about four inches tall. A beet, tomato, cabbage, 
or bean growing in the garden or in a pot or flat willdo. Try to 
get all of the roots out of the soil. Note the great number of 
rootlets and how fine the smallest of them are. Compare the 
spread of the roots with the spread of the parts above the ground. 
What does this show about the work of roots? About the room 
that plants need ? 
