June, 1922] 



MUENSCHER — ABSORPTION OF SALTS 



327 



This indicates a possible relation between the food supplied by the tops to 

 the roots and the utilization of inorganic salts in root growth. The plants 

 which were not shaded and had a greater food supply also had a relatively 

 greater ash content in their roots. Table 10 presents the ratio of roots to 

 tops for all cultures. The root-top ratio of dry weights increases in both 



Table 10. Ratio of Roots to Tops under all Conditions under which Cultures were Grown 

 Td _ Dry weight of tops Tg _ Green weight of tops 



Rd Dry weight of roots Rg Green weight of roots 



Winter Series 



Sunlight. . . 

 Shade tent . 

 Sunlight 



(0.07% solution) 

 (0.07% solution) 

 (0.28% solut ion) 



5-1 

 7.8 



5-5 



2-3 



2.4 

 1-9 



series of the light-shade cultures where the food supply is increased by 

 increased photosynthetic activity. 



If only one of the two above-described series of cultures were used, and 

 the results obtained were attributed to only one factor, namely, a variation 

 in transpiration, one might conclude either that there is a relation between 

 transpii;ation and the quantity of salts absorbed or that there is not, de- 

 pending upon which series of cultures one happened to choose. As a matter 

 of fact, when transpiration was reduced by shading, the photosynthetic 

 activity of the leaves was also reduced, thus reducing the food available for 

 growth. With a reduction in growth, smaller quantities of mineral nutrients 

 are used and therefore inward diffusion is slower. This probably accounts for 

 the greater difference in absolute ash content between the plants grown in 

 the sun and in the shade as compared with the slight difference between the 

 plants grown in the dry and humid chambers. The fact that the per- 

 centage of ash, basedi upon dry weight of the whole plants, varies but slightly 

 in the plants grown in dry or humid atmosphere or in light or shade bears 

 out the indication that in these cultures there is a relation between growth 

 and the absorption of essential salts, regardless of the rate of transpiration. 



Summary 



1 . All plants used in the experiments reported in this paper came from a 

 pure line of barley. The cultures were grown for five weeks in Knop's solu- 

 tion in quart jars under conditions of high and low transpiration. 



2. The transpiration rate was reduced by (i) increasing the atmos- 

 pheric humidity, (2) reducing the light intensity, (3) increasing the con- 

 centration of the nutrient solution. 



