[Reprinted from the American Journal of Botany, 9: 311-329, June, 1922.] 



THE EFFECT OF TRANSPIRATION ON THE ABSORP- 

 ■ TION OF SALTS BY PLANTS 



Walter C. Muenscher 

 (Received for publication November 22, 1921) 



Various opinions have been offered regarding the relation between 

 transpiration and the absorption of solutes. Those investigators who sup- 

 port the older theory maintain that the quantity of salts taken into a plant 

 is directly proportional to the amount of water. transpired, and that the 

 quantity of water transpired is in inverse ratio to the concentration of the 

 solution. Some workers maintain that there is no direct relation between 

 transpiration and the absorption of salts. In other words, the rate at 

 which salts enter the cell is independeAt of the rate at which water enters 

 the cell. Others accept the theory that the water and solutes .of a solution 

 enter a plant at independent rates, but niaintain that after the solutes 

 enter the plant they move along with the water in the "transpiration 

 stream." 



A large amount of literature has appeared dealing with transpiration 

 and water requirements, but, with few exceptions, no papers have appeared 

 which offer any considerable data on a possible relation between transpira- 

 tion and the intake of solutes. In spite of this fact, many authors have 

 not hesitated to employ various theories regarding the relation between 

 transpiration and the absorption of salts in explaining results which they 

 have obtained in investigations upon transpiration and water requirements. 

 The fact still stands, however, that a careful search through the literature 

 reveals no conclusive data which would substantiate the correctness of any 

 of these theories. From a theoretical standpoint it would be reasonable 

 to assume that the entrance of water and solutes into the plant takes place 

 independently, since they enter not through openings which would allow 

 for mass flow but through membranes which necessitate diffusion. Actual 

 data presented are conflicting. The writer has been carrying on a number 

 of experiments with reference to a possible relation between transpiration 

 and the absorption and distribution of salts in plants. The results obtained 

 in those experiments bearing on absorption only are reported in this paper. 



Historical 



Some of the earlier workers varied transpiration by increasing the supply 

 of water or mineral nutrients and determined the effect of this change upon 

 the dry weight and ash content of the plants; Lawes (1850) reported re- 

 sults obtained with several legumes and cereals grown in jars of soil treated 



311 



