834 EXPERIMENT STATION BECORD. 



pp. 7,9, /*/. 1). — This bulletin gives results of a study of environmental influences 

 upon the chemical composition of wheat and of line-selection breeding for varia- 

 tion of nitrogen content of wheat. A review of investigations concerning the 

 composition of wheat is also given. 



From results of a previous study of the relation of climate to the composition 

 of wheat (E. S. R., 26, p. 738) the author was led to conclude " that the climate, 

 as the determining influence upon the length of the development period of the 

 wheat kernel, was the chief factor in fixing the composition of the crop of any 

 given season or locality." In further studying the effect of different factors of 

 climatic and soil environment, acting singly or in combination upon the composi- 

 tion of wheat, it was found that by growing wheat under the same climatic 

 conditions, but in different soils, the differences in composition of the original 

 seed could not have been due to differences in the soil composition ; nor was there 

 any relationship between the protein content of the resultant crops and the com- 

 position of the soil upon which they grew. 



Under conditions of uniform soil, growing season, distribution of annual rain- 

 fall, elevation, etc., with the total annual rainfall the only variable factor, the 

 average protein content of wheat varied for the various counties inversely with 

 the total rainfall received; and figures compiled from the principal wheat dis- 

 tricts of the United States, including irrigated districts of Utah, indicated " that 

 the moisture supply is a very potent factor in determining the composition of the 

 wheat grown in any given locality or season." 



In studying the influences of sunlight, wheats grown in cloudy weather, under 

 cloth of varying density, and in sunshine were analyzed. These results showed 

 that " shading, whatever the texture used or the length of the shading period, 

 caused an inci-ease in the percentage of mineral and nitrogenous matter and 

 decreased percentage of carbohydrates. The increase in other constituents is 

 not directly proportional to the decrease in starch. Hence, we conclude that the 

 changes produced by the exclusion of direct sunlight are not simply a deterrence 

 of the elaboration of starch or carbohydrates, but that other physiological 

 changes are induced by the shading, which are not yet understood." 



With reference to the influence of the length of the growing season it was 

 found that the results of fall and sirring seeding of the same variety of wheat 

 " indicate that the variations in composition of same variety when given a 

 longer or shorter growing season are likely to be fully as great, or even greater 

 than the differences in composition of fall or spring-sown grain of different 

 varieties grown in the same locality." It also appeared from these results 

 " that the differences in composition between fall-sown and spring-sown wheats 

 are not due to actual differences in the habit of growth and development of the 

 different varieties, so-called ' varietal characters,' but to the elongation or short- 

 ening of the growth period by the planting at different seasons of the year." 

 Shortening the development period of grain, by harvesting it before it is quite 

 I'ipe, apparently increased the proportion of protein in the wheat and of gluten 

 in the flour. 



It is notetl that spring wheats in general are richer in protein than winter 

 wheats, but that in 1009 the reverse was true due to a short period of hot, dry 

 weather in the latter part of June, which ripened winter wheat rapidly, followed 

 by an unusually cool damp period which ripened spring wheat slowly. 



A .study of the correlation of the number of days of kernel formation with 

 the composition of the resulting grain showed that " the average weight of 

 kernel varies directly with the length of development period; that the per- 

 centage of nitrogen in the grain varies inversely with the length of this period : 

 and that the length of this period is the determining factor in the tinal com- 

 position of the grain." 



