The Plant as Related to the Soil 



41 



must have a continuous supply of water. The soil is 

 able to store up water in the tiny spaces that separate 

 its particles. The roots penetrate the soil and take up 

 this water as the plant needs it. Plants can not take 

 up solid food. All food substances must be dissolved 

 before they can be 

 absorbed. Hence, 

 water is important, 

 not only as a food, 

 but also as a sol- 

 vent for the particles 

 of soil. The solutions 

 pass through the thin, 

 delicate membranes 

 (cell-walls) of the cells 

 (the root -hairs) by 

 osmosis. 



(d) It retains and 

 regulates the tempera- 

 ture. 



66a. Absorption of 

 Water by Roots Illustrated. 

 The upward movement of 

 water absorbed by plants 

 may be easily illustrated 

 in various ways. A good 

 way is to cover the end 

 of a lamp chimney with 

 parchment paper, as shown 

 in Fig. 27; then fill one- 

 fourth full with syrup. Support the chimney in a vessel of water, 

 with the syrup at the level of the water. After a time, it will be 

 found higher, due to the absorption of water through the membrane. 

 It acts like a large root-hair, which absorbs water from the soil 

 and forces it upward into the stems and leaves. The water would 



Fig. 27. To illustrate the absorption of 

 water by roots. The plant absorbs 

 water against the force of gravity. So 

 will a salt solution. 



