ACIDITY OF CORN AND ITS RELATION TO VEGETA¬ 
TIVE VIGOR 1 
By Annie May Hurd 
Assistant Physiologist, Office of Cereal Investigations, Bureau of Plant Industry, United 
States Department of Agriculture 
INTRODUCTION 
Some investigators are inclined to believe that there is but little 
variation in the cell-sap reaction of healthy plants of a given species, 
and that the hydrogen-ion concentration of each cell remains practically 
the same during its life (2 ). 2 The well-known facts that blood is so 
buffered that in a healthy individual its reaction never varies more than 
a few hundredths of a P H unit from the norm, and that acidosis leads to 
profound physiological disturbances lend color to the supposition that 
the same might be true of plant juices. Consistent with this is the 
statement of Truog and Meacham (16), that for each species 
of plant there undoubtedly is a certain acidity which is most favor¬ 
able for the life processes of that particular species. That this optimal 
reaction of the plant is susceptible to change is suggested by Cleven¬ 
ger (5) who says, “It seems possible that certain conditions may 
change the acidity of the plant juice sufficiently to produce an acidity 
which is unfavorable for the plant.” Moreover, Haas ( 8 ) is led by his 
work on sweet clover, which showed a difference in vigor between the 
first and the second year's growth, and a higher hydrogen-ion concentra¬ 
tion in the less vigorous plants, to ask the question, “Do the more 
vigorously growing plants of a species show a decrease in the actual 
reaction of their juice compared with that of less actively growing plants 
of the same species?” 
This same question was very strongly suggested by the first few experi¬ 
ments of the present investigation, originally designed to determine 
whether or not there are varietal differences in the acidity of corn (maize) 
seedlings. A surprising variability in the acidity values 3 of plants of the 
same variety precluded conclusions on the latter question, but focused 
attention on an apparent correlation between the measurements and 
vegetative vigor. 
PROCEDURE AND METHODS 
Ten strains of Reid Yellow Dent corn (Zea mays), self-pollinated one 
year, were selected for these experiments by Dr. G. N. Hoffer at La 
Fayette, Ind. Dr. Hoffer, referring to the growth of these strains in 
Indiana, describes the plants of No. 31 and 972 as vigorous, without 
1 Accepted for publication June as, 1923. 
* Reference is made by number (italic) to ‘ ‘ Literature cited,” p. 468-469. 
• Throughout this paper**acidity,” unqualified, is used as a general term, including hydrogen-ion con¬ 
centration and titratable acidity. 
Journal of Agricultural Research, 
Washington, D. C. 
agk 
(457) 
Vol. XXV, No. 11 
Sept. 15, 1923 
Key No. G-328 
