1026 
Journal of Agricultural Research 
Vol. XXX, No. 11 
state: “In the case of the soy bean 
roots, while the hydrogen-ion con¬ 
centration usually showed a direct 
relation to the acidity of the soil, the 
total acidity (of the plant) usually 
varied in the opposite direction. The 
data of these experiments strikingly 
show the power possessed by plants to 
regulate internal acidity. Marked 
differences in the acidity of the soil 
caused only small differences in the 
acidity of the plant juices.” It might 
be that the acidity or alkalinity of 
soils as such is not always the limiting 
factor in soil productivity. It is 
recognized that the measure of soil 
acidity alone may be useful in deter¬ 
mining the amount of lime necessary 
to adjust a soil for a crop, but the 
establishment of the characteristic Ph 
point for the seeds as revealed in these 
tests together with the determination 
of the hydrogen-ion concentration of 
the soil solution might serve as a 
better indicator in the use of particular 
crops in particular soils. 
SUMMARY 
When seeds were immersed in repre¬ 
sentative salt solutions, mineral and 
organic acids, and the changes in 
hydrogen-ion concentration and reac¬ 
tion changes were recorded, it was 
found that different seeds are able to 
change the hydrogen-ion concentration 
of the solutions to definite points, and 
that certain equilibrium is reached in 
all solutions after the seeds have 
been immersed sufficiently long. The 
changes of the solutions in which 
previously soaked seeds were immersed 
are very similar to the changes in 
solutions caused by air-dry seeds. 
The reaction caused by dried seeds 
(dried at 100° to 102° C. for 48 and 96 
hours) are similar to the reaction 
changes caused by fresh seeds, although 
the rate of reaction is slightly less. 
The cotyledons of soy beans were more 
powerful to absorb ions from the solu¬ 
tions than were the seed coats; and the 
reaction changes caused by seed coats 
of corn were similar to the changes 
brought about by the whole seeds, 
while changes caused by the endosperm 
of the seeds (carbohydrates mainly) 
were negligible. The chemical proper¬ 
ties of the chief protein constituent of 
the seeds seem responsible for the 
changes in hydrogen-ion concentrations 
of the solutions. 
