sept. 15.1933 Acidity of Corn and its Relation to Vegetative Vigor 465 
DISCUSSION 
Sufficient data have been presented to show that not only the titra- 
able acidity, but also the hydrogen-ion concentration, of the expressed 
juice of corn plants is extremely variable. It has been shown that there 
exists a most striking dependence of acidity upon the reaction of the 
plant to its environment in so far as we can judge of this reaction by 
vegetative vigor. In Clevenger’s (6, p. 230) article are discussed some of 
the ways in which he and others have found acid accumulation to be 
dependent upon internal and external factors. 
It would not be amiss at this point to summarize the various P H 
values reported in the literature for corn juice. Truog and Meacham 
(16) give 5.2 and 5.3 for the expressed juice of whole tops of corn plants 
from unlimed and limed soil, respectively. Haas (8) gives 5.19 and 5.48 
for the tops of two different plantings, the first in Plainfield sand and the 
second in Colby silt loam. Bryan (4) found a variation from 5.1 to 5.2 
in corn leaves, the plants being grown in sand and in solution cultures. 
Bauer and Haas (3), by applying various fertilizer treatments to quartz- 
sand cultures, obtained values varying from 5.31 to 5.49 in leaves and 
from 5.31 to 5.95 in stalks. 
The range of P H and titratable acidity values for entire corn tops ob¬ 
tained in the present investigation is given in Table VI, together with the 
more obvious environmental factors and estimates of the relative vigor 
of the plants. These values are the averages from Tables I, II, III, IV, 
and are brought together to facilitate intercomparisons. Each value is 
an average of all the measurements made on the respective series, each 
composed of 40 to 50 plants, and including an approximately equal num¬ 
ber of plants of each of the 10 strains. Both the maximum and the 
minimum measurements of titratable acidity obtained in each series and 
given under “range” follow the same order as do the respective means, 
and make the reality and significance of differences between the latter 
more convincing. 
Table VI .—Summary of the effect of environment on the titratable acidity and hydrogen - 
ton concentration of tops of corn plants and the apparent correlation of these characters 
with vegetative vigor 
Se¬ 
ries. 
Months 
grown 
<1922). 
Environment 
Relative 
vigor. 
Ph. 
Total acidity 
(CC. N j 20 
NaOH). 
Spe¬ 
cific 
grav¬ 
ity. 
Place. 
Soil. 
Soil 
reac¬ 
tion. 
Out¬ 
door 
tem¬ 
pera¬ 
ture. 1 
Mean. 
Range. 
Ph 
°C. 
I 
April-May.. 
Greenhouse A 
/ 1 Kpn r»Vi 
Sandy loam 
7.0 
62 
Very good 
5*5 
5 . 5 
4.4- 6.6 
II 
May-June... 
uccp ucnui 
Greenhouse B 
Sandy clay 
6.5 
69 
Poor. 
5.3 
6.8 
5.7- 8.8 
shallow 
loam 
bench 
IIP 
May~July... 
.do. 
.do. 
6. 2 
73 
Very poor 
5 -1 
10.3 
6.9-12.3 
1.0233 
IV 
Junc-July... 
Greenhouse A 
Sandy loam 
7- a 
76 
Very good 
5-5 
4 - 7 
3 - 7 - 5 .6 
1.0149 
deep bench 
1 Averages of hourly temperature readings of the Weather Bureau for each day during the growth of the 
series. 
1 Grown in the same soil as Series II, planted between the rows before that series was cut. 
