Aug. 15,1921 
Effect of Ammonium Sulphate upon Plants 
719 
the second were only slightly chlorotic as the result of an insufficient 
supply of available iron. 
At the end of the growth period of 35 days the dry weights of tops and 
roots were obtained in the usual way. The yield for the cultures of the 
two series, together with the average hydrogen-ion exponents of the 
solutions obtained at the end of the various growth intervals, are given 
in Table VIII. The yield values of tops and roots as given in this table 
are represented graphically in figure 7, the upper set of graphs represent¬ 
ing the yields of tops and the lower set the root yields. The dry-weight 
values as ordinates are here plotted against the amounts of iron in milli¬ 
grams per liter of solution as abscissas. 
Table VIII.— Hydrogen-ion concentrations and dry-weight yields of wheat grown in two 
types of nutrient solutions supplied with varying quantities of iron in the form offerrous 
sulphate 
Quantities of iron (in milli¬ 
Tottingham’s solution (T3R1C5), 
series C. 
Tottingham’s solution (T3R1C5) 
modified, [(NHdaSO* substituted 
for KNOa], series D. 
grams per liter of solution). 
Dry weight 
of tops 
Dry weight 
of roots. 
Average 
PH 
values.® 
Dry weight 
of tops 
Dry weight 
of roots. 
Average 
PH 
values. 
0.00. 
Gm. 
I.4017 
Gm. 
0.5113 
5-53 
Gm. 
2.2010 
Gm. 
0.4726 
4.63 
.01. 
2.1212 
•7513 
5.68 
2.4131 
I.0250 
4.54 
.10. 
3.0448 
1.1837 
5-68 
1 * 95 2 5 
.3233 
4.64 
•25 .. 
2.6691 
.8798 
5-63 
1.4792 
•2738 
4.60 
•50 .. 
2.3908 
.6265 
5.60 
2.0002 
• 37 12 
4.64 
•75 . 
2.7478 
.8182 
5-59 
1.1501 
.2227 
4.63 
1.00.. 
2.2148 
.6210 
5-59 
I - I 937 
.2263 
4.60 
i- 5 o. 
3.I924 
1.1366 
5.61 
1.3032 
•2543 
4.64 
2.00. 
2.4451 
.7448 
5-58 
1-3113 
•2354 
4-63 
3 00 . 
2.5870 
. 7962 
5-55 
.9408 
. I829 
4.56 
S-oo. 
2 2296 
•SS58 
5*51 
.8288 
. l6o8 
4-53 
® These values represent the average of all the determinations made for each solution at the end of the 
growth intervals throughout the experiment period. The initial PH values of all the solutions in each 
series were approximately 4.7. 
As indicated by the graphs of figure 7 the yields of tops and roots 
from the cultures containing ammonium sulphate (series D), not includ¬ 
ing the yield from the first culture in the series, were always much inferior 
to the corresponding yields from the Tottingham solutions. The first 
three cultures show a rapid decline in yield with increasing small amounts 
of iron, after which the decrease in yields is less marked, although there 
is a general decrease in the yields of both tops and roots with increasing 
amounts of iron throughout the series, as the gradual downward slope 
of the graphs indicates. This is in entire agreement with the general 
appearance and condition of the plants as already described, with respect 
to the evidence of a toxic influence as indicated by the apparent size, 
color, and the generally depressed condition of the plants which was 
progressively more pronounced with increasing amounts of iron. 
