May, 1921] 
DICKSON — COMPOSITION OF OAT PLANT 
263 
The Relation between Nutrients and Calcium Content of Straw 
The calcium content of the straw of the oat plant varies in a way in 
general similar to, although more marked than, that characteristic of the 
grain. Lawes and Gilbert (1884) have shown that the composition of the 
straw (leaves and stems) of various plants may be modified very markedly 
by the addition of nutritive elements as well as by the subtraction of these 
elements. The results have been so consistent in field work of this nature 
as to lead certain investigators to suggest that the composition of the grain, 
the reproductive part of the plant, is very stable, while the variation, if 
any occurs, is in the straw and roots. The average percentages of calcium 
in the straw produced in the different culture solutions are given in table 5. 
Table 5. The Average Calcium Content of Straw from Plants Grown in the Normal Solution 
and in Solutions with One Nutritive Element in Each Case Reduced to One Tenth Normal 
Solution, Deficient Element 
Given 
Percent CaO in Straw 
1915 Crop 
1916 Crop 
1917 Crop 
Average 
Normal 
2.315 
2.176 
4.850 
3.114 
Ca 0.1 
0.520 
0.220 
0.485 
0.408 
Mg 0.1 
4.030 
2.589 
K 0.1 
2.362 
1.666 
4.260 
2.763 
P 0.1 
3.175 
1.072 
0.935 
1.727 
N 0.1 
1.288 
1-335 
1.935 
I.519 
The average calcium content of the straw from the calcium-deficient 
solutions — containing one tenth of the calcium present in the normal solution 
• — is only 13 percent of that of the straw produced in the normal cultures. 
The calcium content of the straw from the potassium-deficient solutions, al- 
though high comparatively speaking, is not as high as in the grain from the 
same set of cultures. The calcium content of the straw of the plants from 
the phosphorus-deficient cultures is considerably lower than that of the 
plants from the nitrogen-deficient solutions, and in both it is lower than the 
calcium content of the check plants. 
In general, a deficiency of calcium in the culture solution causes a very 
marked lowering of the calcium content of both grain and straw of plants 
grown therein. A deficiency of potassium or of magnesium does not greatly 
affect the intake and storage of calcium either in the grain or in the straw. 
A deficiency of either phosphorus or nitrogen causes a lowering of the cal- 
cium content of both grain and straw; especially is this true for plants in 
the phosphorus-deficient solutions. The average composition of the plants 
for the three years is given in table 8, and in graphic form in figure i. 
The Relation between Nutrients and Phosphorus Content of Grain 
Phosphorus, unlike calcium, enters into chemical combination with a 
great many of the plant compounds, especially with those of the seed. 
