5 EFFECT OF SOLUBLE SALTS UPON PLANTS. 



EFFECT OF A MIXTURE OF SOLUBLE SALTS, PRINCIPALLY 

 SODIUM CHLORID, ON PLANT STRUCTURE. 



METHODS OF EXPERIMENTS. 



Experiments to determine the influence of a mixture of salts in 

 modifying the structure of plants were undertaken with wheat 

 (Triticum durum), oats (Avena sativa), and barley (Hordeum dis- 

 tichum). The plants were grown in a greenhouse where the condi- 

 tions as to light, heat, and moisture were fairly uniform. The seeds 

 were germinated and the seedlings were grown for about four weeks 

 in the soils with which the experiments were made. 



The saline soil used was obtained from the vicinity of Salt Lake 

 City, Utah," and while it contained some sodium sulphate, sodium 

 bicarbonate, and potassium sulphate, the results obtained are prob- 

 ably to be attributed chiefly to the action of sodium chlorid, since 

 this is by far the most abundant salt present. 



By mixing the saline soil with the requisite quantity of garden loam 

 (from Washington, D. C), the different concentrations of total soluble 

 salts with which experiments were made (2 per cent, 1.5 per cent, and 

 1 per cent of the weight of the dry soil) were obtained, the per- 

 centages being calculated from the electrolytic resistance of the 

 saturated soil. 



On the basis of the analysis by the Bureau of Soils these three 

 concentrations of total soluble salts would represent, respectively, 1.4, 

 1, and 0.7 per cent of sodium chlorid. These percentages are con- 

 siderably above the limit which under natural field conditions is 

 generally considered safe for wheat, oats, and barley. In fact, 0.5 

 per cent of sodium chlorid will usually prevent the production of seed 

 in these plants. 



In every case a check planting was made in the garden loam to 

 serve as a control on the plants growing in the saline soil. 



In order to prevent the leaching out of the salt in watering, the 

 plants were grown in glass pots. These had a capacity of about 800 

 grams of the soil used. By careful watering, the salt was kept well 

 distributed through the soil in the pot until the seeds had germinated 

 and the plants had developed two or three leaves. 



The effect of the salts on the structure of the plant was determined 

 by sectioning the leaf and measuring the thickness of the cuticle and 

 the size of the epidermal cells. All sections were made near the mid- 



a An analysis by the Bureau of Soils, U. S. Department of Agriculture, of a sample of 

 soil used in these experiments before mixing it with garden loam showed that it 

 contained 2.1 per cent of soluble salts, of which 4.66 per cent was potassium sulphate, 

 16.98 per cent sodium sulphate, 70.58 per cent sodium chlorid, and 7.78 per cent 

 sodium bicarbonate. 



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