CHAPTER XIII 



WATER AND MINERAL NUTRIENTS. ACTION ABOVE 

 THE ROOT 



155. The water in the soil is not usually present as free 

 water, but in the form of films that adhere to the indi- 

 vidual particles of soil. The root-hairs are in contact with 

 the soil particles and films of water. (Fig. 125.) The finer the 

 soil, the greater the number of soil-particles and the greater 

 the film-moisture. The film-moisture surrounding the grains 

 may not be perceptible, yet the plant 



can utilize it. Absorption by roots may 

 continue in a soil that seems to be 

 dust dry. 



156. The root must be warm if it is to 

 perform its functions. A proper tempera- 

 ture is essential to the life processes. 

 Should the soil of fields or greenhouses 

 be much colder than the air, the plant 

 suffers. When in a warm atmosphere, 

 or hi a dry atmosphere, plants need to 

 absorb much water from the soil, and 

 the roots must be warm if the root-hairs 

 are to supply the water as rapidly as it 

 is needed. If the roots are chilled, the 

 plant may wilt or die. Try this with two 

 potted plants, as radish, coleus, tomato. 

 Put one pot in a dish of ice water, and 

 the other hi a dish of warm water, and 



keep them in a warm room. In a short 125 - The rootlets and 



,. , . , , .. j . . root-hairs cling to the 



time notice how stiff and vigorous is part icie8 of sou. 



(75) 



