June 23,1923 
Protein Percentage of Wheat, Oats, and Barley 1045 
It was the intention to show the relative variation between wheat, 
a naked grain, and oats and barley, to which the glumes adhere, in the 
amount of material lost. As oats and barley are apparently less variable 
in their protein percentage than wheat,^ it was thought that the 
adhering glumes might be influential in inhibiting respiration and con¬ 
sequently account for this lesser fluctuation. This demonstration was 
made impossible through inability to obtain samples of uniform mois¬ 
ture content, which, no doubt, is largely responsible for the wide dif¬ 
ference in the results. 
Olf RieSPIRATlON UPON PROTEIN PERCENTAGES 
The result of the loss of carbohydrate material as affecting a variation 
in the protein percentage can be ascertained by estimating the per¬ 
centage of the grain which is subjected to respiration activities. The 
composition of the average grain is approximately 12.50 per cent protein, 
2.50 per cent ash, and 85 per cent carbohydrate. Respiration being 
confined to the carbohy^ate portion of the grain, it would require 
approximately 7 per cent variation in this material to effect a i per 
cent difference in the protein percentage. As the number of grams of 
carbohydrate loss, in this case, is based upon the 100 gm. basis, these 
same figures represent the loss in percentage. The protein will vary i 
per cent for each 7 per cent loss or gain in carbohydrate. 
Calculating from the amount of carbohydrate material lost as given 
in Table I, it becomes apparent that there is a possible variation in wheat 
of 1,46 per cent, oats 1.62 per cent, and barley 2.2 per cent protein, due 
to respiration. 
While these figures seem upon first thought to be definitely significant, 
it is not probable that respiration creates a variation in the protein 
content as wide as the above possibilities suggest. As indicated, con¬ 
siderable carbohydrate is lost during the ripening period, but fresh 
material is no doubt being moved into the grain until complete 
maturity, which is sufficient at least to counterbalance that which is 
lost. It must be recognized, however, that the amount of material 
being moved into the grain will be a variable factor and dependent 
largely upon the environmental conditions which prevail at that time. 
Brenchley (i) has shown that in the development of the barley grain 
the maximum dry weight of 1,000 gm. is reached when the moisture 
content is approximately 40 per cent, and that this dry weight remains 
practically constant and does not fall off during the desiccation process, 
while the moisture content is being lowered to 21 per cent. The fact 
that the weight of dry matter is not lowered indicates that up to the 
time of maturity considerable material is being moved into the grain to 
compensate for that lost by respiration. 
More confirmation of this supposition is presented by Harlan (3) in 
his study of the development of the barley grain, where he has shown 
that deposits of dry matter in the kernel continue until very near the 
point of absolute ripeness. He concludes (4) from irrigation studies 
that plants are able to utilize water to the date of full maturity, with 
much increase in dry matter content. 
* McGinness, F. W. op. cit. 
