THE ROOT 231 



below, owing to the action of transpiration. If there is a defici- 

 ency of moisture in the soil, and the loss of moisture in the cells 

 of the upp^r structure cannot be made good by the rising flow 

 of liquid, the turgor of these cells will be diminished. The 

 cells cease to be stiff and become limp, and the whole plant, 

 or at least those parts which are not stiffened by woody cell- 

 Avalls, will fade. 



A plant will also fade, if it is transplanted and care is not 

 taken to leave the root-ends undisturbed. This is explained by 

 the fact that the plant deprived of its root-hairs cannot absorb 

 moisture from the soil. 



{d) Manuring and Rotation oj Crops. — As we have seen on 

 page 213, the minerals absorbed by the roots are nitrogen, 

 sulphur, phosphorus, kalium, natrium, calcium, silicium, mag- 

 nesium and iron. All plants do not feed on exactly the same 

 elements. Moreover, some require more of one, and others more 

 of another element. But all require a large quantity of nitrogen, 

 which they derive from various nitrogenous salts. Now, farmers 

 who year after year grow plants on the same fields, must take 

 pains to manure their fields, if their crops shall not deteriorate. 

 For, with the crop they remove a great quantity of raw plant- 

 food from the soil, so that the soil becomes poorer and poorer in 

 the materials available for plant-growth. The manure used 

 ordinarily is decaying or decayed animal and vegetable sub- 

 stances. Since the various requirements of different crops have 

 been investigated scientifically, manuring can be economised 

 by the use of artificial manure and richer crops can be secured 

 thereby. 



As some plants require more or less of a particular element 

 than others, and strike their roots more or less deep in the 

 ground, the farmer can rotate his crops, that is to say, if paddy 

 and pulses, for instance, are grown in a certain field one year, 

 they are followed up the next year by sugar-cane, and so on, 

 coming back again to paddy eventually. 



