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TEXTBOOK OF PLANT PHYSIOLOGY 



for it is reproduced by the plants when grown on soils where no 

 salts are present. But with an increase of the salt concentration 

 in the soil, succulence increases, which after all may be regarded, 



in a measure at least, as one of the 

 direct results of high soil salinity. 



Because of the abundance of sodium 

 chloride in some saline soils, large 

 quantities of this salt are found also 

 in the ash of plants native to such 

 soils. Some of the saline plants, as 

 for instance Statice gmelini, can re- 

 move the surplus through special 

 glands, however, and consequently 

 have a much lower salt content. 

 \ / K "% n Sodium chloride is not an absolute 



physiological necessity for saline plants. 

 They can grow on soils which are not 

 saline. The experiments by Keller, 

 though, have shown that the addi- 

 tion of this salt improves their de- 

 velopment (Fig. 39). This is one of 

 the reasons why they are able to 

 displace from alkali soils all the other 

 plants, most of which are injured by 

 certain quantities of salt. Excessive 

 amounts of sodium chloride, however, 

 can destroy even the most tolerant of 

 saline plants. 



There are plants which accu- 

 mulate considerable amounts of ni- 

 trates in a manner similar to the 

 halophytes. These plants thrive best 

 They are often found near dwellings 

 Among such plants are 



Fig. 38. — Salicornia, a fleshy 



plant from saline soil {after 



Schimper). 



on soils rich in nitrates. 



where the soil contains much refuse. 



included several species of Atriplex and Chenopodium, the nettles, 



sunflower, and many others. It is interesting to note that the 



concentration of nitrates in the sap of such plants is many times 



higher than the concentration of these salts in the soil solution. 



Hence it is legitimate to call these plants nitrate accumulators, as 



sea algae may be termed accumulators of iodine and bromine. 



