76 WATER AND MINERAL NUTRIENTS 



the one whose roots are warm, whereas the other may show 

 signs of wilting. 



157. Plants take from the soil an immense quantity of 

 water. A single corn plant may require in a growing season 

 200 to 500 pounds of water. From 250 to 400 or more pounds 

 of water are required for the production of one pound of 

 dry matter in plants. Most of the water absorbed by the 

 roots is given off by the plant as water vapor in a process 

 of evaporation called transpiration (166). 



158. Water serves the plant in a number of ways. It is 

 a nutrient for the plant and takes part in the formation of 

 substances manufactured by the plant. The cell sap is 

 water with substances in solution. The water serves as a 

 carrier of the materials derived from the soil and also 

 for the manufactured food made within the plant. Let us 

 see what nutrients the ordinary green plants secure from 

 the soil. 



159. Nutrient Materials Secured from the Soil. — We have 

 seen that all nutrient material must be in solution in water 

 to be taken in by the root. The ordinary green plant obtains 

 from the soil the following essential elements: 



Nitrogen, chemical symbol N. Potassium, K. 



Phosphorus, P. Calcium, Ca. 



Sulfur, S. Magnesium, Mg. 

 Iron, Fe. 



Chlorin is also an essential element for buckwheat. The 

 elements in the above list (except nitrogen) are known as 

 the mineral elements. All of the above elements are taken 

 up not in their elemental form but in the form of salts. 



160. Ten elements are essential for the growth of all 

 green plants. In addition to the seven above mentioned, the 

 plant requires hydrogen, H, oxygen, O, and carbon, C. 

 Hydrogen and oxygen are supplied in the form of water, 

 which has the chemical formula H2O. Carbon for the green 



