CHAPTER XX 

 LOSS OF WATER 



You scarce could think so small a thing 

 Could leave a loss so large. 



— G. Massey. 



The plant requires, as has been already pointed out (Chap. IV), 

 large quantities of water which are used in the manufacture of 

 food. This water remains in the plant until the food is oxidized 

 or broken down when it may be released; but, in addition, the 

 plant needs water for other purposes. Water (1) is an essential 

 component of protoplasm, (2) serves as a solvent for oxygen and 

 carbon dioxide, (3) aids in the transportation of raw materials 

 and foods, (4) has a high specific heat and absorbs much excess 

 heat energy, and (5) maintains turgor in the living cells. 



The average water content of some common plants is indicated 



in the following table : 



Per cent 

 Plant wt. of water 



Apples (fruit) 83 



Beets 87 



Cabbage 90 



Carrots 85 



Red clover (green hay) 71 



White clover (green hay) 78 



Corn (dry seed) 11 



Corn (green fodder) 80 



Cowpeas (green hay) 84 



Cucumbers (fruit) 96 



Grape (leaves) 69 



Oats (dry grain) 11 



Onions 88 



Irish potatoes 79 



Sweet potatoes 71 



Pumpkins 93 



Rice (grain) 13 



Spinach 90 



Timothy (cured hay) 42 



Wheat (grain) 14 



In addition to satisfying all these needs, the plant also requires 

 large amounts of water to replace that lost by bleeding, through 

 the action of glands, by guttation, and by transpiration, each of 

 which causes of water loss will be discussed in turn. 



242 



