CHAPTER IV 

 NATURE OF ALKALI INJURY TO THE PLANT 



Many of the general effects of excessive quantities of 

 soluble salts in the soil are well known, but there still 

 remain to be worked out a number of important problems, 

 the solution of which will throw a great deal of light on the 

 exact nature of alkali injury. Every farmer in alkali 

 regions recognizes by the appearance of the soil and the 

 limitations in crop growth the presence of alkali, but the 

 actual underlying causes of the abnormal conditions are in 

 part a mystery to even the most profound students of the 

 subject. 



Prevention of Water Absorption. Doubtless one of 

 the very important injuries caused by alkali results from 

 checked absorption of water by plants. It matters not 

 how desirable other conditions are how much plant- 

 food is available, how deep the soil, or how favorable the 

 temperature if the plant cannot secure water it can make 

 no growth. Roots absorb water from the soil by the 

 process of osmosis. Because the cell-sap of root-hairs 

 contains a stronger solution than the soil, water passes 

 through the cell-wall and plasma membrane into the cell 

 where it assists in the vital processes of the plant. Since 

 carbohydrates are constantly being elaborated in the 

 leaves, the cell-sap farthest from the roots is more con- 

 centrated than that which has recently been diluted in the 

 roots by the entrance of water from the soil. The transpi- 



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