Vol. XXIII, No. 10 
814 Journal of Agricultural Research 
SOIL CONDITIONS WHICH FAVOR ALUMINUM AVAILABILITY 
The conditions which develop in a soil to make the aluminum salts 
available also account for increased quantities of available iron salts, and, 
therefore, salts of both elements are absorbed at the same time. Because 
of this close chemical relation of these two metals it is necessary to study 
much further the effects of fertilizers and soil acidity upon their respective 
availabilities to the com plants. The fact that chemical tests of diseased 
and normal stalks in the field show variations in the accumulations of 
compounds of each metal in the stalks in the nodal tissues suggests that 
the specific effects of the metals upon the discoloration and rate of dis¬ 
integration of the vascular plate tissues may be determined by certain 
conditions in the soil or by variations in the “elective” capacities of 
different plants to absorb quantities of these metallic salts when available. 
It is important, therefore, that the corn plants in the seedling and 
juvenile stages of growth should be least affected by the available metals. 
Acid phosphate applied to the soil at planting time greatly stimulates the 
growth of young plants in experimental plots. Whether this is due to the 
increased phosphorus or to the precipitation of the available aluminum 
which might affect the plants is uncertain, yet it is known that aluminum 
toxicity takes place in the absence of sufficient phosphates to precipitate 
the aluminum salts in the soil solution. And, furthermore, the plants in 
the youngest stage of development would be most rapidly affected and 
therefore show the effects of toxicity in retarded growth. 
TISSUES IN WHICH THE METALS ACCUMULATE 
By treating the vascular plate, zone B tissues, in healthy plants with 
concentrated nitric acid, the cells where the accumulations of the organic 
metallic compounds occur first will give a distinct xanthoproteic reac¬ 
tion. The cells lie close to the xylem elements of the branching bundles in 
the vascular plate. When the disintegration of the tissues begins, these 
cells are the first ones to break down. 
This disintegration effect on the zone B tissues may have much signifi¬ 
cance although it must be admitted that very little is known regarding it 
at the present time. When the metals accumulate in these nodal tissues 
after their injection into the stalks it has been found that the nodal tissues 
in zone B, as shown in plate 3, A, give a strong test for peroxidase with 
gum guaiacum. This reaction is probably of much significance and may 
indicate in a measure the probable cause of the discolorations which are 
consequent to the increased metallic content of these tissues. 
Bayliss (j) reports that— 
a peroxidase is in all probability a peculiarly active form of the colloidal hydroxides 
of manganese, iron, or copper preserved in this active state by the presence of an 
emulsoid colloid, such as gum or albumin. 
He states further that the metals found to be active as peroxidases are 
those capable of existing in two states of different valencies. If this 
conclusion of Bayliss is correct it would assist in interpreting the phe¬ 
nomena observed in the nodal vascular plate tissues in the treated stalks 
and in diseased stalks. The fact that the iron and aluminum accumula¬ 
tions are organic aggregates of some kind in these tissues, and the fact 
that the tissues become strongly active enzymatically, with special refer¬ 
ence to peroxidase, may be .significant. The intensity of this action 
probably would determine the period of functioning of these tissues. The 
