ScDiif'son and Allen: physical factors on transpiration. 51 



Effect of Some Common Acids and Alkalies on Transpiration 



The response of transpiration to acids and alkalies has been 

 studied by a number of investigators, whose results are contra- 

 dictory. Burgerstein ("Die Transpiration der Pflanzen," 1904) has 

 carried on the most extensive experiments along this line. In gen- 

 eral, he found that weak acid solutions accelerated transpiration, 

 and alkaline solutions when used extremely dilute also accelerated it, 

 but when stronger solutions were added transpiration was retarded. 



In the experiment here conducted only four acids and three alka- 

 lies were used, these being tested on two species of plants, Helian- 

 thus annuus and Zea mats. Half normal stock solutions were ac- 

 curately titrated in the Chemical Laboratory. 



Plants were tested both in potometers and in pots. In the latter 

 case they were grown in a loam soil. Weighings were taken every 

 twenty-four hours. The transpiration of plants in distilled water, 

 in potometers and soil was taken as a basis of comparison. The 

 table following gives summarized results of all readings made in 

 these tests. 



TABLE X. 



ZEA MAIS HELIANTHUS ANNUUS 



In Potometers In Soils 

 Distilled 29.7 43.1 



Water Per cent solu- Per cent solu- 



tion tion 



.065 .130 1.0 1.5 



Acids — 



HCL 31.2 32.3 44.7 44.9 



HNO3 30.8 30.9 43.8 46.2 



GHiOj -21120 . 29.9 30.4 43.5 44.4 



'C2H4O2 30.3 32.0 43.8 43.6 



Alkalies — 



KOH 26.2 25.3 40.8 43.7 



Na^Coi 28.3 28.1 43.0 42.5 



NH^OH 24.4 26.3 42.2 41.8 



That the acids and alkalies used in these experiments act as stim- 

 uli with respect to their influences on transpiration will be observed 

 in the above data. 



In every case in the summarized table the acids accelerated this 

 function, while in the majority of cases the alkalies retarded it. 

 In a very few cases weak alkaline solutions increased transpiration 

 as compared with that of distilled water. This differs somewhat 

 from that found by Burgerstein ("Die Transpiration der Pflanzen," 



