July 15, 1921 
Assimilation of Nutrient Salts by Corn 
553 
In the two preceding experiments and in the work reported in the 
previous paper, where half the roots were in a complete solution, the lack 
of any one element did not significantly depress growth and assimilation 
more than the lack of another. In this experiment, however, where 
both the solutions were incomplete, growth and assimilation varied 
markedly according to which elements were supplied to only half the 
roots. A restriction of the supply of nitrogen and phosphorus to sepa¬ 
rate halves of the roots depressed growth and assimilation more than a 
similar restriction of the supply of nitrogen and potassium, or phosphorus 
and potassium. 
The relative growths of roots in the A and B flasks, shown by the rela¬ 
tive percentages of total roots by weight, in the two flasks is of interest. 
If the relative growths are indicative of the relative needs of the plant 
for the elements present in the solution, it would seem from the data on 
plants 33 to 48 that nitrogen is needed more than phosphorus; from 
plants 49 to 64, that nitrogen is needed much more than potassium; and 
from plants 65 to 80, that phosphorus is needed slightly more than potas¬ 
sium. The relative needs of the plants for these three elements may 
well hold for corn only and for this stage of growth of corn. 
TxpivRimi^nt IV.—The roots divided between two solutions, one of 
which lacked one element and the other two elements. 
The three nutrient solutions lacking nitrogen, phosphorus, and potas¬ 
sium, respectively, and the three solutions lacking nitrogen and phos¬ 
phorus, nitrogen and potassium, and phosphorus and potassium, 
respectively, can be combined in nine pairs. Only three of the possible 
combinations, however, afford in the pair a complete nutrient solution. 
The effect of these three pairs of solutions on growth and the assimilation 
of nutrients are shown in Tables VI and VII. 
The assumption made in the previous experiment, that corn needs 
nitrogen more than it needs phosphorus, and phosphorus slightly more 
than potassium during the period of growth covered by these tests, 
helps to explain the results obtained in this experiment as well as the 
results obtained in the succeeding ones. A second assumption, however, 
is needed—namely, the assimilation of nitrogen, phosphorus, or potassium 
is greater when these elements are absorbed from solutions containing 
two or all three of them than when they are absorbed from solutions con¬ 
taining only one of them. 
This second assumption explains why plants 49 to 64 assimilated rela¬ 
tively more nitrogen than plants 33 to 48 and relatively more phosphorus 
than plants 65 to 80, also why plants 65 to 80 assimilated relatively more 
potassium than plants 49 to 64. 
48496°—21-4 
