May, 1922] TOTTINGHAM AND RANKIN — NUTRIENT SOLUTIONS 
Comparison of Different Concentrations and Renewal 
Rates of Solutions 
Wheat seedlings reared on flowing tap water were mounted in groups 
uf 5 in each 480-cc- jar. Three jars received Livingston and Tottingham's 
solution R8C1 diluted to o.i the usual concentration and renewed con- 
tinuously, approximately at the rate of 2 liters per jar in 24 hours. A 
second group of three jars received o.oi the usual concentration of the 
same solution at the rate of 4 hters per jar in 24 hours. Finally, a third 
set of jars received the solution at 0.001 the usual concentration at the 
rate of 8 liters per jar in 24 hours. It will be noted that the rates of renewal 
were not increased in proportion to the dilution of the nutrient solution. 
The proportions used were dictated largely by practical considerations of 
time and apparatus available. 
The young plants were grown under these conditions from May 3 to 
May 16, 192 1. During this period the atmospheric conditions of the green- 
house, as measured by atmometers (Livingston, 8), were as follows: 
Mean daily evaporation from standard spherical white atmometer, 20.4 cc. 
Mean daily evaporation from standard spherical black atmometer, 25.6 cc. 
Ratio of black to white instrument, 1.25. 
The cultures at 0.001 the usual concentration were discontinued on 
May 7, when the plants showed decided signs of withering, with little 
growth. At the time of discontinuing the series, the plants grown in o.oi 
the usual concentration of solution were decidedly withered and had ap- 
parently ceased to grow, while the leaves of cultures grown in o.i the usual 
concentration of solution were beginning to turn yellow. The yields are 
presented in table 3. 
Table 3. Influence upon Growth of Concentration and Rate of Renewal of the Nutrient 
Solution 
Concentration 
of Solution 
Rate of 
Supply 
Average Length 
Average Dry Weight 
Tops 
Roots 
Tops 
Roots 
Mm. 
Mm. 
Mg. 
Mg. 
O.I usual 
O.OI " 
O.OOI " 
2 1. in 24 hr. 
4 " " " " 
8 " " " 
225 (38)* 
144 (19) 
84 (3) 
72 (3) 
Practically 
201 (9) 
92 (27) 
no growth 
117 (10) 
70 (3) 
* Average departure from mean. 
From these data it appears that, for these rates of renewal, o.oi the 
usual concentration of this nutrient solution was not nearly sufficient for 
maximum growth. The limits of practicability in rate of supply and de- 
gree of dilution of the solution for maximum growth are important points 
for further investigation. 
