Mar . 10,1923 
Aluminum and Iron Compounds in Corn Plants 
821 
equally well to plants in all localities, irrespective of whether rootrots 
develop in them and appear to become a serious menace to the crop. 
SUMMARY 
(1) One of the most characteristic differences between normally grow¬ 
ing corn plants and those which become severely rootrotted is the con¬ 
dition of the vascular plate tissues in the nodes of the stalks. The plants 
which become severely rootrotted are those which have the nodal tissues 
discolored and in various stages of disintegration. 
(2) This disintegration of the nodal plate tissues begins in the absence 
of any specific organisms in the tissues. 
(3) The brown, yellowish brown, and brownish purple discolorations 
with their consequent disintegrations which are frequently found in dis¬ 
eased plants have been produced artificially by injecting solutions of cer¬ 
tain salts of aluminum and iron into the plants. Definite chlorophyll and 
leaf-tissue changes have been produced also. Other factors, however, 
may operate to produce similar effects. 
(4) These artificially induced changes in the plant parts closely resemble 
the phenomena which develop in plants growing in the field under condi¬ 
tions favorable to rootrots. 
(5) The most severe cases of rootrots have been found in soils notable 
because of their deficiencies of lime and available phosphates. 
(6) Such soils have variable quantities of salts of aluminum and iron 
available for absorption by plants. 
(7) Com plants show marked differences in the quantities of aluminum 
and iron salts which are absorbed by them. These differences develop 
when the salts are available in subtoxic concentrations in the soil and are 
believed to be due to specific selective capacities of different plants to 
absorb the available aluminum and iron salts from the soil. This type 
of selective absorption cannot operate when the aluminum and iron salts 
occur in quantities which are toxic to the roots. 
(8) A definite cumulative toxicity of aluminum salts within the plants 
was established by the injection experiments, and it is believed that the 
same phenomenon occurs naturally in the field. The relative quantities 
of the available metals and of nitrates in the soil determine, in a large 
measure, the rate of development of the cumulative toxicity of the metals 
within the plants. Those plants which contain the largest quantities of 
these metals are the ones which seem to develop the most severe cases of 
rootrots when the organisms are present in the soil and the meteorological 
conditions favor their optimum growth. 
(9) When abundant aluminum injuries occur in the corn plants in cer¬ 
tain fields it is an indication that the soil is deficient in available phos¬ 
phates. 
(10) The application of lime and phosphates to soils in which rootrots 
have developed in destructive proportions has been decidedly beneficial 
in controlling them. The use of limestone alone in some instances proved 
harmful, but in all cases studied so far the application of available phos¬ 
phates produced plants which were better and more resistant to the 
rootrots. 
