July 1,1925 
The Heritable Properties of Wheat 
69 
dry weight, granted that the proper physiological conditions pre¬ 
vail, depends largely on what the minimum for that variety hap¬ 
pens to be. If, for example, two different varieties each having the 
same percentage of grain to total dry weight, and, consequently, 
equal capacity to increase the protein content of their grain, having 
6 and 8 per cent protein, respectively, as the minimum, would, as 
a result of treatment, produce grain that would vary proportionally 
in protein content. But the increase in one case, say it was 50 per 
cent, would be such as to retain for that product the character of 
soft wheat, while equal per cent increase in the other variety would 
result in grain belonging to the hard wheat class; 9 and 12 per cent, 
respectively, would be the per cent protein of these' two varieties. 
In the correlation between the order of ripening of the varieties 
after nitrogen was supplied, and that of the gain in per cent protein 
of the grain, is evidence that the genetic property which determines 
how quickly any wheat variety matures likewise expresses the 
relative capacity of that variety to increase the protein in grain. 
Whether any variety produces high-protein grain is, however, not 
determined by the mere property of earliness but by the physio¬ 
logical condition already defined, namely, the relative rate of the 
absorption of nitrogen, which, in turn, is dependent on the supply 
available to the plants. Thus if varieties requiring different numbers 
of days are to absorb and utilize a given limited amount of nitrogen 
supplied to the culture 90 days after planting, it is obvious that 
those varieties which utilize this material in the least number of 
days have a higher rate for that process, or processes, than have 
varieties which require a greater number of days. It is in this re¬ 
lation that the genetic property of earliness bears on the per cent 
protein in grain. It affects the relative rate of intake of nitrogen 
by the plants. Therefore, wheats that are early by heritable prop¬ 
erty are physiologically better adapted to produce higher-protein 
grain than are late wheats. This, however, in turn, does not mean 
that late varieties are necessarily low-protein wheats. On the con¬ 
trary, many are relatively high in protein. _ If sufficient nitrogen is 
available to the plants for a period of three to six weeks during 
certain phases of their growth (differing with the varieties), which 
includes the latter part of the “shooting” period for the culms, 
the period of heading, and the early part of the period of filling 
of the mold, then high-protein grain obtains. On the other hand, 
even though the soil does not contain as much nitrogen as the 
plants could' absorb (conditions that usually prevail in wheat¬ 
growing sections), this does not necessarily infer the production of 
low-protein wheat. Other compensating factors, such as that re¬ 
lated to ratio of grain to total dry weight, can preclude the perform¬ 
ance of results of any specific factor. 
As the protein content of wheat can be markedly affected by 
manipulation of the supply of nitrogen in the growth media, so 
climate, season, and soil, through their influence on the rate of 
supply of nitrogen to the plants must affect the protein content of 
the grain. In some regions climate and seasonal cnanges on varietal 
characters will have more pronounced influence on the quality of 
grain than in other sections. Likewise the effect of properties of 
soil on the protein content of grain may be markedly altered by the 
influence of climate and season. It therefore follows that while the 
