THE ABSORPTION OF CARBON BY THE ROOTS OF 
PLANTS 1 
By J. F. Breazeale 
Associate Biochemist , Western Irrigation Agriculture, Bureau of Plant Industry , United 
States Department of Agriculture 
In an experience of several years in fertilizer and nutrition investiga¬ 
tions the writer frequently has had occasion to run cultures of wheat 
seedlings in solutions of the salts of the three fertilizer elements, nitrogen, 
potassium, and phosphorus, singly and in all combinations. When 
working under known conditions, with pure materials, on ashing the 
crop thus grown and dissolving the ash for a potassium or phosphorus 
determination, he has almost without exception found that the presence 
of nitrates in the solution is followed by the presence of carbonates in 
the ash. 
Using the several kinds of salts singly and in all possible combinations 
and, as a control, a culture solution of distilled water only, the reaction 
of the ash toward hydrochloric acid has been observed to be as follows: 
Culture solution. 
Reaction. 
Control, distilled water. No effervescence. 
Sodium nitrate (NaNO a ). Effervescence. 
Potassium chlorid (KC 1 ). No effervescence. 
Sodium phosphate (Na 2 HP 0 4 ). No effervescence. 
Sodium nitrate and potassium chlorid. Effervescence. 
Sodium nitrate and sodium phosphate. Effervescence. 
Potassium chlorid and sodium phosphate. No effervescence. 
Sodium nitrate, potassium chlorid, and sodium phosphate. . . Effervescence. 
It was also noticed, incidentally, that sodium carbonate in the culture 
solution would result in an ash that effervesced with acid, as would 
calcium and other carbonates, and also bicarbonates. A further inter¬ 
esting point noticed was that the absorption of an element of plant food 
is greatly influenced by the presence of a different element of plant 
food in the nutrient solution. For example, the absorption of potassium 
from a solution of potassium chlorid, of a definite concentration, may be 
doubled by the addition of sodium nitrate to the solution. These obser¬ 
vations were followed by much work, carried on at intervals, which finally 
culminated in the two experiments here described. 
About 1,000 seeds of Pacific Bluestem wheat were sprouted upon 
each of eight perforated disks floating in water. When the seeds had 
germinated and the plumules had reached a length of i cm., 200 of the 
best plants from each disk were transplanted to eight other disks, each 
of which was floated in 2,500 cc. of a different nutrient solution and 
placed under observation. In a day or two, in such cases, the plu¬ 
mule will grow through the perforations and the seedling establish 
itself in the solution. The solutions were not changed, but were kept 
up to volume with distilled water. When the plants had been under 
observation for 21 days, they were dried and weighed. One hundred 
1 Accepted for publication Aug. n, 1923. 
Journal of Agricultural Research, 
Washington, D. C. 
ahn 
(303) 
Vol. XXVI, No. 7 
Nov. 17, 1923 
Key No. G-336 
