NUTRITION OF PLANTS CONSIDERED AS AN ELEC¬ 
TRICAL PHENOMENON‘ 
By James F. Breazeale 
Associate Biochemist, Office of Biophysical Investigations, Bureau of Plant Industry, 
United States Department of Agriculture 
INTRODUCTION 
When wheat seeds are placed in a suitable nutrient solution and germi¬ 
nation begins, the demand of the embryo and tiny seedling for food is 
first upon the stored up material in the seed. As the plumule and radicle 
develop, however, absorption of food from the nutrient solution begins 
and gradually increases with increased growth. During the germina¬ 
tion process there is first an exudation of plant food, particularly phos¬ 
phorus and potassium, from the seed, with little or no absorption from 
the nutrient solution, but, when the plumule has reached a length of 2 or 3 
cm. and has broken through its sheath, a distinct demand for food begins 
to be manifested in the tissues. 
It is of much importance in fertilizer investigation to note tliat this 
demand of the plant for nutrient material may be measured by its pull 
upon the nutrient sdution, and it is equally important from a physio¬ 
logical standpoint to note that this demand may be modified in certain 
ways and may even be augmented or built up by withholding any of the 
food elements. There is a “residual effect'’ that is very pronotinced in 
plants; the desire for food when not available is carried over a long period 
of time and it seems to be cumulative. In this respect a plant seems 
to behave very much like an animal organism, the demand for food 
increasing as a fast continues. There is another very pronounced phe¬ 
nomenon that might well be termed a “time factor.” A plant will not 
necessarily absorb twice as much nutrient material in two hours as it 
absorbs in one. It seems to possess the power to prepare reserves—that 
is, to form compounds in one part of its system which may be trans¬ 
located to another part when needed. 
It seems that this “demand” for food must be taken into account in 
all studies of absorption. 
DEMAND OF WHEAT PLANTS IN THE PRESENCE OF A CONTINUOUS 
SUPPEY OF PEANT FOOD 
About a dozen culture pans were prepared, each pan holding 2,500 cc. 
of nutrient solution and containing about 500 plants. The plants were 
grown by sprinkling seed upon floating perforated aluminum disks, and 
the nutrient solutions, containing 125 parts per million each of nitrogen 
(N), potash (KjO), and phosphoric acid (P2O5) as sodium nitrate, potas¬ 
sium chlorid, and sodium phosphate, were changed daily. There was 
thus an abundance of plant food always at the disposal of the plant, 
and this was determined by measurements made from time to time. A 
^ Accepted for publication May 13,1922. 
(41) 
Journal of Agricultural Research, 
Washington, D. C. 
adf 
Vol. XXIV, No. I 
Apr. 7, 1923 
Key No. G-29S 
