May, 1921] 
DICKSON — COMPOSITION OF OAT PLANT 
265 
translocation of phosphates, if, as is thought by a number of biochemists, 
magnesium is the chief carrier of phosphoric acid; and second, the calcium 
in the normal Knop's solution may be present in sufficient quantity to 
react with the phosphates to form the less soluble tricalcium phosphate, 
thus making the phosphorus present less available for the plant. The 
nitrogen-deficient culture solutions, likewise, produced plants with grain 
having a very high total phosphorus content. In all probability the 
factors concerned here are very complicated, as the deficiency of proteins 
would be apt to upset normal metabolism and therefore to produce very 
abnormal results within the plant. It is quite possible that much of the 
phosphorus in this latter case may be stored as the mineral phosphate in 
combination with the large amounts of bases present. The nutrition of 
the plant in this case is undoubtedly very much disturbed and very abnormal. 
A deficiency of potassium in the culture solution, on the contrary, results 
in the production of grain with a low phosphorus content, the average 
phosphorus content for the three years being 0.122 percent lower than in 
the check. The greatest reduction in phosphorus content, however, is in 
the grain from phosphorus-deficient solutions. The phosphorus content 
of this grain is reduced to 46 percent of the phosphorus present in the 
grain from the checks. In all probability the reduction took place in the 
amount of phytin and lecithin stored in the grain. In general, then, there 
is a very marked variation in the phosphorus content of grain produced 
under different nutritive conditions. A deficiency of phosphorus or of 
calcium causes the greatest variation, the lack of the former element pro- 
ducing a very marked decrease, that of the latter a moderate increase in 
phosphorus content. 
The Relation between Nutrients and Phosphorus Content of Straw 
The composition of the straw generally shows more marked variations 
than that of any other part of the plant, unless it be the roots, for the 
Table 7. The Average Phosphorus Content of Straw from Plants Grown in the Normal Solution 
and in Solutions with One Nutrient Element in Each Case Reduced to One Tenth the Normal 
Amount 
Solution, Deficient Element 
Given 
Percent P2O0 in Straw 
1915 Crop 
igi6 Crop 
1917 Crop 
Average 
Normal 
0.309 
0.734 
0.832 
0.628 
Ca 0.1 
0.415 
0.354 
1.230 
0.667 
Mg 0.1 
0.892 
0.673 
K 0.1 
0.265 
0.334 
0.682 
0.427 
P 0.1 
0.092 
0,060 
0.051 
0.068 
N 0.1 
0.834 
1.750 
1.805 
1.463 
unassimilated excess salts are stored here in the case of the addition of 
large amounts of specific elements, and on the other hand the straw releases 
