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CHAPTER VI 
THE ROOT 
In general the roots of a plant serve to absorb water and 
mineral matter from the soil and to anchor the plant in the 
ground. ‘These may be said to be the chief functions of roots. 
Absorption of water. The stems, leaves, and fruits of plants 
are usually exposed to high rates of evaporation in the air, 
from which they are protected by a covering which is more or 
less impervious to water. This coating not only reduces the 
amount of water that they lose through transpiration but at 
the same time prevents them from absorbing water from the 
atmosphere. Such plants are therefore dependent on their roots 
for the absorption of water. 
Absorption of minerals. Plants not only need water, carbon 
dioxide, and oxygen, but also nitrogen, sulphur, phosphorus, 
potassium, calcium, magnesium, and iron. These last elements are 
obtained from the soil in the form of compounds dissolved in water. 
Some plants probably require, in addition, sodium and chlorine. 
Anchorage. Plants that are growing in the ground need 
roots not only for the absorption of water and mineral matter 
but also in order that they may be anchored to the substratum ; 
otherwise, erect plants would be blown over by the wind, 
while small creeping plants might be carried to unfavorable 
situations. There are three different types of root systems. 
Many dicotyledonous plants develop a long main root which 
grows deep in the soil and produces smaller secondary roots; 
such long roots are called taproots. In other cases the plant, 
instead of having a taproot, is anchored in the ground by 
several large secondary roots. Monocotyledonous roots, like 
monocotyledonous stems, do not have secondary thickening, and 
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