1042 
Journal of Agricultural Research 
Vol. XXIV, No. 12 
That the external environmental conditions are responsible largely 
for the protein percentage found in the grain has been noted from the 
earliest observations. A realization, however, of the manner in which 
the contents of the grain are influenced by the capricious nature of ex¬ 
ternal conditions and the physiological complexities which may arise 
during the life of the plant, is of more recent discovery. In order to 
understand fully how an environmental condition may a&ct a variation 
in the chemistry of the grain, it is necessary to follow out, from the earliest 
stages, the development of a kernel and the processes through which it 
reaches maturity. 
Early investigational work along this line consisted of chemical 
analyses of the grain being made shortly after the time of flowering or 
when the mold of the grain was first formed, and continuing progressively 
at short intervals until the grain was mature. The nitrogen percentage 
was found to be highest as the kernel mold was formed and became 
decreasingly less as the grain filled and approached maturity. These 
observations led investigators to assume that most, or practically all, 
of the nitrogenous material was taken from the soil and moved into the 
grain during the earlier stages of growth, and that the filling of the 
endosperm with starch or carbohydrate material was carried out in tlie 
later stages of growth. Thus, it was concluded that the percentage of 
protein would be influenced directly by the amount of carbohydrate pro¬ 
duced and translocated during the filling stage. As the environmental 
conditions in most of the grain sections are favorable to maximum growth 
during the early stage of development, and very often too severe to per¬ 
mit later growth to proceed or the grain to be filled, this was the natural 
conclusion to be drawn. 
More recent work by Brenchley (2)^ of the Rothamsted Experiment 
Station, Thatcher (5, 6 ), of the Minnesota Agricultural Experiment Station, 
and others, has brought out some slightly different ideas on the subject. 
These investigators have shown that the greater amount of nitrogenous 
material of the wheat or barley kernel is not taken up during the early 
stage of growth, but that the nitrogen inflow is continuous until the grain 
has reached maturity. According to Brenchley the nitro-carbohydrate 
movement into the grain is in constant ratio during the entire period of 
kernel development. It has been suggested that the variation in protein 
content is not due to the failure of Bie plant to produce and translocate 
carbohydrate material at the later stages of growth, but that the per¬ 
centage of nitrogen found in the kernel is determined by the amount of 
carbohydrate lost by respiration during the desiccation process through¬ 
out the ripening period. 
The difference of opinion as to which process is most effective in deter¬ 
mining the character of the grain contents suggested the necessity of 
obtaining definite data to verify the later idea, which appears from avail¬ 
able information to be an unwarranted conclusion. The authors have con¬ 
ducted a project through the years 1920 and 1921 to determine the 
variation in protein in wheat, oats, and barley, as affected by respiration, 
and to show the relative variation in protein when the same grains are 
grown under widely different conditions. 
* Reference is made by number (italic) to “ Literature cited," p. 1048. 
