278 
Journal of Agricultural Research 
Vol. XXVIII, No. 3 
THE EFFECT OF CONCENTRATION UPON THE GROWTH AND 
COMPOSITION OF ORANGE SEEDLINGS 
A series of water cultures was conducted in a glass house for a period of 
122 days to study the effects of six concentrations of nutrient solution upon 
seedlings. The concentration of the nutrient solutions ranged from 364 to 
3635 parts per million. The solution used as a standard had the following com¬ 
position expressed in parts per million: 
Na 
K 
Ca 
Mg 
Mn 
Fe 
Cl 
NOs 
SO 4 
PO< 
Total 
7 
185 
158 
54 
Trace. 
Trace. 
10 
718 
216 
105 
1,454 
If we represent the total concentration of the standard as C, we may desig¬ 
nate the series employed as .25 C, .50 C, 1.0 C, 1.5 C, 2.0 C, and 2^5 C. Eighteen 
1-liter glass jars each containing three African sour orange seedlings ( Citrus 
aurantium) were used for each of the six concentrations. Each week the solu¬ 
tions in the jars were changed and the water Iqss measured. At the end of the 
122-day period the 54 seedlings used in each set of cultures were removed, 
weighed, and dried at a temperature between 60° and 70° C. The tops had 
attained a height of about 15 cm. The leaves, stems, and roots were kept 
separate for further determinations. 
Table I.— Relations between the concentration and reaction of nutrient solution 
and of the leaf sap of trees to which the nutrient solution was applied 
Nutrient solution 
Percolate 
Leaf sap 
Series 
Osmotic 
pressure 
Ph 
Ph of first 
portion of 
percolate 
Ph 
Osmotic 
pressure 
1-5_ 
SAND CULTURES 
Atm . 
0.728 
5.2 
5.9-7.2 
6.0 
Atm. 
20.8 
6-11..... 
1.459 
5.2 
6.6-8.0 
5.88 
22.59 
12-17...... 
1.568 
5.2 
5.4-7.8 
5.88 
21.26 
18-23..... 
1.001 
5.2 
6.4-8.0 
5.85 
23.10 
24-29... 
1.218 
5.2 
6.8-7.35 
5.87 
20.45 
30-35..... 
1.278 
7.55 
8.3+c 
5.95 
21.47 
36-41....... 
1.447 
7.45 
8.3+c 
5.80 
21.17 
42-46... 
0.708 
5.2 
7.0-7.4 
5.95 
22.53 
47-51_ 
0.531 
5.2 
6.0-7.2 
5.77 
21.89 
84-88_ 
SOIL CULTURES 
(«) 
cn 
5.80 
21.03 
89-92....... 
( c ) 
5.82 
20.32 
® Distilled water only was added. 
*> Distilled water containing 1,600 parts per million NaCl was added. 
« Sodium carbonate present. 
The data on the weight of the plants and of their ash are given in Table II, 
and show that the best growth of seedlings was made in 1.5 C, a solution which 
had an initial concentration of 2,181 parts per million. The plants grown in 
.25 C and .50 G were inferior to those in the other concentrations. The differ¬ 
ences in both green and dry weight of tops were greater than for the correspond¬ 
ing weights of roots; in fact, the latter were rather uniform. By way of com¬ 
parison, it may be stated that 54 seedlings of the size of those used to start these 
cultures had a green weight of 21.4 gm. and a dry weight of 3.52 gm. 
The data on transpiration per unit of dry weight of tops show considerably more 
variation than when computed per unit of dry weight of the entire plant. The 
