B. P. I.— 369. 



THE INFLUENCE OF A MIXTURE OF SOLUBLE 

 SALTS. PRINCIPALLY SODIUM CHLORID. UPON 

 THE LEAF STRUCTURE AND TRANSPIRATION 



OF WHEAT. OATS. AND BARLEY. 



INTRODUCTION. 



The investigation reported upon in the following pages was under- 

 taken with a view to ascertaining whether the presence of a mixture 

 of soluble salts, consisting chiefly of sodium chlorid, such as occurs 

 in excessive quantities in many natural " alkali" soils, will affect the 

 structure of plants not especially adapted to such soils, and if modi- 

 fications of structure take place whether they resemble those which 

 characterize plants growing naturally in saline soils (halophytic 

 plants). The effect of this salt upon the transpiration of nonhalo- 

 phytic plants was also studied. 



It has been possible to demonstrate that culture in a soil contain- 

 ing considerable quantities of sodium chlorid together with other 

 salts produces measurable changes in the leaf structure of wheat, 

 oats, and barley and that these changes are in the direction of 

 xerophytic and halophytic structure, i. e., that which characterizes 

 plants that naturally inhabit very dry situations or saline soils. The 

 most noticeable modification thus produced was the conspicuous 

 bloom or waxy deposit that formed on the surface of the leaves. In 

 control plants grown in nonsahne soil the bloom was so httle developed 

 as to be hardly observable. This development of bloom was accom- 

 panied by an easily measurable increase in the thickness of the cuticle 

 and outer walls of the epidermal cells and by a marked decrease in 

 their size. 



In regard to transpiration, it was found that when the "alkali" 

 salts are present in sufficient concentration to cause the modifications 

 of structure above noted transpiration is considerably reduced. On 

 the other hand, the same salts when present in amounts too small to 

 produce any measurable influence upon structure have a decidedly 

 stimulating effect upon transpiration. 



It is believed that this line of investigation will throw much light 

 upon the problem of what constitutes •"alkali resistance" and will 

 therefore be of service in the search for useful plants adapted to 

 growing in saline or "alkali" soils. 



134 7 



