Mar. io. 2933 Aluminum and Iron Compounds in Corn Plants 
803 
SELECTIVE ABSORPTION IN RELATION TO RESISTANCE TO 
ROOTROTS 
It is believed that resistance of the com plants to rootrots may be 
closely related to what appears to be a selective absorptive capacity of 
plants toward aluminum and iron when these metals are available in 
subtoxic concentrations. Selective absorption may be a very important 
heritable character in com. If so, the phenomenon of susceptibility 
to rootrots which is associated with the accumulation of abundant 
quantities of iron and aluminum in different parts of corn plants may 
have as one of its causes a definite type of selective absorption for alumi¬ 
num and iron salts. Therefore, the accumulations will occur in the 
plants under conditions in the soil when the quantities of these available 
salts are in subtoxic proportions. Such conditions usually are found 
in most acid soils. 
It is true also that the quantity of available aluminum compounds 
in some soils may be sufficient to more than overcome the natural resis¬ 
tance possessed by strains which ordinarily show good growth in soils 
with lower concentrations of available iron and aluminum salts. In 
this case, irrespective of strain differences, the plants may be severely 
affected and a distinct toxic effect of the aluminum be noted in all of 
them. Plate 4 shows two fields where many of the plants were severely 
stunted. All of these plants had the typical nodal discolorations and 
disintegrations of the basal tissues shown in Plate 2, B. 
A field of Stowell's Evergreen Sweetcom was seen at Decatur, Ill., 
in August, 1920, in which all the plants were stunted in that part of the 
field which had been in clover sod the preceding season. In the part 
of the field which had been in com the plants showed good growth. 
The plants which were stunted showed concentrations of the metals 
in the nodal tissues, but no root lesions were noticed at that time. Later 
in the season many of these plants became severely rotted. The plants 
which had made better growth on the com land were notably less seriously 
attacked. The soil was the typical Illinois black loam and gave an 
acidity reaction of P H 5-6 for the clover-sod land and P H 6.2 for the 
com land. 
The nodal-tissue injuries shown in Plate 2, B, and Plate 5 are not the 
only effects resulting from the accumulation of these metals in the corn¬ 
stalks. Analyses of the various plant parts show that the metals are dis¬ 
tributed throughout the plant. The very obvious effects of the metals 
upon the nodal tissues gives them a seemingly greater importance in these 
tissues, but the unbalanced absorption of essential nutrients which takes 
place when these discolorations of the tissues are produced also accounts 
for a disturbance in the normal functioning of other active tissues. 
Analyses of the leaves from diseased and healthy stalks show wide 
variations in the quantities of aluminum in them. The average aluminum 
(A 1 2 0 3 ) content of the ash of the leaves of four selected normal stalks from 
a field near Battleground, Ind., in 1920, was 0.44 per cent, while the alu¬ 
minum content of the ash of the diseased plant leaves was 0.98 percent, ovei 
twice as much. The calcium (CaO) content was 0.70 per cent in the 
normal leaves and 0.56 per cent in the leaves from diseased stalks. 
The percentage of aluminum in the ash of the leaves from two root- 
rotted stalks from Bloomington, Ill., in 1918, was 1.16 per cent, while that 
of the leaves from stalks which remained healthy, and which were grown 
from the same seed ear, was 0.67 per cent. These cases which have just 
