Apr. 16,1917 
Absorption of Nutrients 
89 
The maximum amount of nitrogen, 100, is taken as that absorbed by 
plants with 100 per cent of their roots in the complete solution. As plants 
with no roots in a complete solution (the incomplete solution being 
nitrogen-free) can absorb no nitrogen, the zero point is also fixed. The 
two other points found experimentally for plants with 27 per cent and 
53 per cent of their roots 1 in the complete solution determine fairly well 
the form of the curve. 
From the uniformity of the preceding results it seems permissible to 
state, as a rule, that when all the roots of a plant are supplied with all 
the essential elements except one, the fewer the roots supplied with the 
one lacking element the 
less nearly the plant 
will attain a maxi¬ 
mum absorption o f 
this element. As this 
rule has been found 
valid for nitrogen, 
phosphorus, potas¬ 
sium, and iron, it 
probably applies to 
all the mineral nutri¬ 
ents. ' The rule holds 
when the total quan¬ 
tity of the element 
supplied is equal to or 
in excess of the needs 
of the plant. If the to¬ 
tal quantity of element 
supplied is insufficient FlG * I ~ Relation between portion of roots supplied with nitrogen and 
. , .. , , portion of maximum absorption attained. 
for the needs of the 
plant, a more equal absorption of the element by plants with part and with 
all their roots might be expected. This, however, has not been proved. 
The relative amounts of the element absorbed per gram of roots by 
plants with part and with all their roots supplied with the element 
varied considerably, according to several conditions, although this 
figure wp.s always much higher for the plants partially supplied than 
for those completely supplied. The greater the depression of growth by 
the smaller total amount of the element absorbed by the plants partially 
supplied, the greater was the quantity of the element absorbed per gram 
of roots. When the partially supplied plants had a greater ratio of 
roots to tops than the completely supplied plants, the absorption per 
gram of roots for the partial plants did not so greatly exceed -that of the 
complete plants. The smaller the portion of roots in the complete 
solution, the greater was the absorption of the element per gram of roots 
in the complete solution. 
1 The average of results from Experiments I to IV are used. 
78371 °— 17—2 
