CHAPTER IX 



THE WATER OF THE SOIL IN ITS RELATION TO 

 PLANTS 



Water begins its service to plants by promoting the proc- 

 esses of soil weathering, which results in the simplification of 

 compounds for plant utilization. It also functions more di- 

 rectly in plant development in maintaining the turgidity of 

 the cells, in carrying materials, regulating temperature and 

 in furnishing a supply of hydrogen and oxygen for the plant. 

 These direct and indirect functions of water in relation to 

 plant growth may be considered from a number of different 

 viewpoints. 



97. Functions of water to plants. — Water acts as a 

 solvent and as a medium for the transfer of nutrients from 

 the soil to the plant. This transfer relationship is rather 

 complex, since most nutrient materials penetrate the cell- walls 

 of the absorbing surfaces of the roots in an ionic condition. 

 As a nutrient water becomes a part of the cell contents with- 

 out change or is broken down into its elements and utilized in 

 the production of new compounds. In addition, water by 

 maintaining turgidity, in equalizing the temperature by evap- 

 oration from the leaves, and in facilitating quick shifts of 

 nutrients and food from one part of the plant to another, 

 acts as a carrier during assimilation and while synthetic and 

 metabolic processes are going on. 



Soil-moisture, therefore, in proper amounts, becomes one 

 of the controlling factors in crop growth and must be looked 

 to before the maximum utilization of the nutrient elements 

 can be expected. The amount of water held within the plant 



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