July 15, 1921 
Assimilation of Nutrient Salts by Corn 
569 
5. When the roots were divided between solutions that were lacking 
in the same number of nutrients, root growth was greatest in the solu¬ 
tion containing nitrogen. 
6. The relative, as well as the absolute, root growth made in any 
solution, however, depended on the character of the solution in which 
the remainder of the roots were growing. 
7. When the roots were divided among three incomplete solutions, 
each of which lacked either one or two of the elements, nitrogen, phos¬ 
phorus, and potassium, the amount of nitrogen assimilated approached 
the normal assimilation of nitrogen—that is, the assimilation of plants 
with all their roots in a complete solution—considerably nearer than the 
amount of potassium assimilated approached the normal assimilation of 
potassium; also, potassium was assimilated to a very slightly nearer 
normal extent than phosphorus. This fact doubtless would not hold 
for all plants or for all stages of growth. 
DISCUSSION OF RESULTS 
The rate at which nutrient ions are assimilated by the plant is doubtless 
dependent upon the rates of absorption, translocation within the plant, 
and utilization, or the rate at which the ions are built up into complex 
compounds. These three rates of absorption, translocation, and utiliza¬ 
tion are, of course, mutually dependent, a reduction in any one reducing 
the other two. 
The inability of a plant to effect a maximum assimilation of an ion 
which is supplied to only a portion of the roots evidently is not due to 
the root cells being unable to absorb this ion with sufficient rapidity. 
Data presented in the previous paper showed that roots could increase 
their rate of absorption very markedly. When only one-fourth of a 
plant's roots were supplied with nitrates, these roots absorbed nitrogen 
2.26 times as rapidly as the roots of plants which were completely supplied 
with nitrates. 
The diminished assimilation of nutrients when the roots are divided 
between incomplete solutions is more probably due to a diminution in 
the rate at which the nutrients are translocated to the cells where they 
are utilized. Although it is not known exactly how the ions are trans¬ 
located, a rough explanation can be given of how the transference of 
ions in the vegetative part of the plant would be slowed down by absorp¬ 
tion of the different nutrients by separate roots. 
When, for instance, the nitrogen, phosphorus, and potassium are 
confined to separate roots (as in experiment VIII), there is an unusual 
transference of nitrogen to the roots in the phosphorus and potassium 
solutions, and an extraordinary transference of phosphorus to the roots 
in the nitrogen and potassium solutions, etc. The extra work of this 
unusual transference of nutrients, however, is hardly sufficient to account 
for the diminished assimilation. 
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