The Water in Plants 



33 



APPROXIMATE AMOUNT OF WATER IN PLANTS 



53a. How many pounds of water in a ton of freshly cut alfalfa? 

 How many pounds of water in a ton of air-dry, or cured alfalfa? 



54. Loss of Water by Plants. Plants lose water through 

 the stomata in their leaves, and their other parts to a 

 slight extent. Some plants lose water very slowly, even 

 under very dry conditions, as, for instance, the cactus 

 on the dry, open prairies. It has been estimated that 

 ordinary cultivated plants lose water by transpiration 

 about one-fifth to one-tenth as fast as it would evapo- 

 rate from a surface of free water. In times of drought, 

 when the air is very dry, transpiration will be greater 

 than under ordinary conditions. Hot, dry winds in- 

 crease the rate at which water escapes from the plant. 

 (See 1 98, How Plants Dry the Soil.) 



55. Drought-resistant Varieties of cultivated plants 

 have coverings that prevent the ready escape of water. 

 This may be seen in the varieties of corn imported 

 from dry countries, which have thicker leaves and 

 coarser shucks than the native kinds. 



QUESTIONS 



1. In what three ways do plants use water? 2. How does the 

 plant get water? 3. How does the plant lose water? 4. How do 

 drought-resisting plants prevent the escape of water? 



