THE EFFECT OF RESPIRATION UPON THE PROTEIN 
PERCENTAGE OF WHEAT, OATS, AND BARLEY ‘ 
By F. W. McGinnis, Assistant Professor of Farm Crops, Division of Agronomy and 
Farm Management, and G. S. Taylor, Analyst, Division of Chemistry, Department 
of Agriculture, University of Minnesota 
INTRODUCTION 
Scientific literature contains considerable information dealing with 
the protein content of small grains. In a review of the available informa¬ 
tion bearing upon this subject, which has accumulated during the past 
century, one chief point of interest seems to be the variation in protein 
percentage found in the different grains when produced under different 
conditions of soil and climate. 
Much study and investigational work has been conducted to ascertain 
the cause of the variation found in this regard, especially with wheat. 
Wheat has been the subject of greatest study, because of the interest of 
those engaged in the manufacture of wheat products, where the chemistry 
of the grain is of paramount importance in determining the quality of 
the output. 
The reason why grain produced under a given environment will yield 
a berry entirely different in chemical structure from that produced under 
a condition of a different nature, has been a subject of much study with 
the grain chemist as well as with those engaged in physiological inves¬ 
tigations. 
It seems to be the generally accepted idea at the present time that 
the percentage of protein in wheat is due to a certain environmental 
condition which prevails during the growth and maturity of the grain. 
Upon analysis of the grain, grown under widely different environmental 
conditions, this is generally found to be true. It is common knowledge 
that wheats grown in the north central section of the United States are 
of a higher protein percentage and milling value than those grown in the 
eastern or far western sections. There is no doubt that the varieties 
being grown for the highest total yield in these respective areas, account, 
to a certain degree, for the difference in protein percentage in the grain. 
But when consideration is confined within a variety, the variation is 
found to be very wide. 
Some investigators have attributed the difference to the available 
nitrogen in the soil, others to varietal differences, while most students 
of the subject have recognized it to be a physicochemical phenomenon 
correlated more directly with the climatic conditions which prevail during 
the life processes. In general, the protein percentage has been found 
to be dependent somewhat upon the length of the growing season and 
to a greater degree upon the length of the ripening period. As these two 
factors are dependent largely upon the amount of available moisture in 
the soil, the strongest correlation has been found between the amount of 
rainfall, its distrib^ution, and the protein percentage.^ 
' Accepted for publication Feb. 20,1923. Published with the approval of the Director as paper 397 of the 
Journal Series of the Minnesota Agricultural Experiment Station. 
* McGinnis, F. W. ths relative effect of environment upon the chemical composition of 
WHEAT, oats, barley, AND CORN. Unpublished thesis. Copies on file in Cornell University library, 
Ithaca, N. Y. 1918. 
Journal of Agricultural Research 
Washington, D. C. 
afc 
(1041) 
Vol. XXIV, No. 12 
June 23, 1933 
Key No. Minn.-47 
