Mar. io, 1923 
Aluminum and Iron Compounds in Corn Plants 
8i; 
increased peroxidase activity in the tissues may yield hydrogen peroxid, 
or other by-products, which in themselves may become toxic and account 
for the destruction of the tissues consequent to the metal accumulation. 
Furthermore, other metals and organic substances may enter the plant 
and stimulate this peroxidase activity in the zone B tissues. After the 
basal tissues and roots begin to rot the decomposition products from these 
rotted parts may be absorbed and act as toxins in the plant. These 
suggestions are given because the resultant effects of the root and stalk 
rots upon the plant present a complexity of phenomena which are 
difficult to analyze. 
On the other hand, the fact that the metals accumulate in the cells 
giving a strong xanthoproteic reaction may confirm the report of Szxics 
(24) that aluminum combines directly with protoplasm and “sets it.” 
Loew (1 5) infers that calcium-protein compounds exist in the organized 
particles from which the nucleus and chlorophyll bodies are built up. 
The replacement of the calcium by another element would lead to a 
disturbance in the structure of the protein molecule, and this would 
prove fatal. 
Whether or not calcium-protein aggregates exist in the cells in zone B 
tissues as well as in the leaf tissues, it is of much significance that when 
calcium was introduced along with the aluminum salts the injuries to 
the nodal and leaf tissues were reduced in severity during the length of 
time necessary for the aluminum ions alone and in equivalent concentra¬ 
tions to become actively toxic. The mass effect of a preponderance of 
calcium in the cell tissues may inhibit the disorganization of the protein 
aggregates by the aluminum and iron salts. 
The iron-citrate solution was absorbed readily by the stalks and killed 
the plants within three days. The characteristic effect of* the iron 
citrate was a rapid wilting of the stalk and a heavy precipitation of iron 
compounds all along the vascular bundles, as shown in Plate 18, A. 
The leaves developed a vinaceous gray color, and the tissues next to the 
vascular bundles in the stalk and leaves became brown. 
Ferrous sulphate was probably the most actively toxic form of iron salts 
tested (PI. 18, B). The dark brown discolorations along the vascular 
bundles in the leaves are characteristic of the first effects of ferrous sul¬ 
phate, and this is followed by a wilting and the death of the leaves. 
The vascular bundles in the stalk become brown, and in zone B dis¬ 
integration of the tissues occurs. The color of the darkened tissues is a 
brownish purple, not unlike the discolorations found in stalks growing 
in acid soils, as shown in Plates 2, B, and 5, A and B. The disinte¬ 
gration of the tissues, of course, is much more rapid than that which 
occurs naturally in the field, due to the stronger concentrations of the 
solution used. The most abundant nodal discolorations do not appear 
in the stalks until tassel time, a period of probably 60 to 80 days after the 
seed is planted, although seedlings growing in soils with large quantities 
of available aluminum and iron will show the basal tissue discolorations 
very early, according to their different relative absorption rates. 
Because of the gradual and progressive changes which can be induced 
in the corn plants by the injection of dilute solutions of aluminum and 
iron salts and because these so closely resemble the progress of develop¬ 
ment of similar symptoms in com plants growing in different types of 
soil, it is evident that the available salts of aluminum and iron in most 
soils are absorbed by the plants in dilute subtoxic concentrations and 
enter into organic combinations with various tissues in the plants. With 
