May, 1921] 
DICKSON — COMPOSITION OF OAT PLANT 
261 
The Relation between Nutrients and Calcium Content of Grain 
The general conception has been that there is very Httle variation in 
the composition of the seeds or reproductive parts of plants. Lawes and 
Gilbert (1884) state that the composition of the grain is not greatly varied 
by normal variations in soil composition. Their ideas of the limits of 
variation of the grain can best be stated in their own words : 
The composition of the grain only varies in any marked degree according to manure, 
when there is a very abnormal deficiency of one or more constituents, having regard to the 
amount of growth which is induced by the liberal supply of others. The composition of 
the grain is very uniform, notwithstanding there may be a very great excess of supply, and 
a relatively very great excess taken up by the plant, in which latter case a large excess 
remains in the straw. 
As previously stated, the earlier studies on composition have usually 
been made on plants which were grown under field conditions in soil of low 
or high fertility, or, in other words, where the supply of the available nutri- 
tive elements was not under strict limitations. It is evident from the data 
presented in table 4 that the calcium content of the grain varies greatly 
Table 4. The Average Calcium Content of Grain from Plants Grown in the Normal Solution 
and in Solutions with one Nutrient Element in Each Case Reduced to One Tenth Normal 
Solution, Deficient Element 
Given 
Percent CaO in Grain 
191 5 Crop 
1916 Crop 
1917 Crop 
Average 
Normal 
0.317 
0.405 
1.360 
0.694 
Ca 0.1 
0.042 
0.061 
0.180 
0.094 
Mg 0.1 
1.422 
0.729 
K 0.1 
0.216 
0.227 
1.760 
0.734 
P o.i 
0.275 
0.284 
0.540 
0.367 
N 0.1 
0.305 
0.548 
0.500 
0.451 
when the supply of available nutritive elements is limited to a definite small 
amount. 
The plants grown in culture solutions deficient in calcium — one tenth the 
amount in the normal culture solution — produced grain of very low calcium 
content, an average of ten percent lower than the calcium content of the 
grain produced in the normal solutions. 
Physiologists and biochemists consider the role of calcium as secondary 
in the formation of seed. Therefore, possibly it may be replaced to a 
greater or less extent by certain other bases, notably potassium and mag- 
nesium. Some proof supporting this hypothesis is given in the fact that the 
average calcium content of the grain produced in magnesium-deficient and 
potassium-deficient solutions is relatively high. The low calcium content 
of the grain produced in potassium-deficient solutions during the first two 
years, however, would indicate that this is not true under all environmental 
conditions. The calcium content of the grain produced in the phosphorus- 
and nitrogen-deficient solutions during the first two seasons is quite high. 
