EFFECT OF DIFFERENT OXYGEN PRESSURES ON 
THE CARBOHYDRATE METABOLISM OF THE SWEET 
POTATO 
By Heinrich Hasselbring 
Plant Physiologist , Office of Plant Physiological and Fermentation Investigations , 
Bureau of Plant Industry , United States Department of Agriculture 
INTRODUCTION 
The recognizable products which are formed as a result of starch 
transformation in the sweet potato ( Ipomoea batatas) during storage are 
reducing sugars and cane sugar. According to Miyaki 1 the reducing 
sugars consist of glucose and possibly fructose. Maltose has not been 
found. The main product is cane sugar, which has been frequently 
identified. 
In the course of ordinary storage the monosaccharids soon reach their 
maximum concentration, which in Big Stem and Southern Queen rarely 
exceeds 2 per cent of the weight of the fresh potato. The cane sugar 
continues to accumulate until in the varieties named it represents as 
much as 7 per cent of the fresh potato. 3 
The fact that the reducing sugars remain at a low concentration while 
the cane sugar continues to accumulate suggested that the reducing 
sugar is an intermediate product in the transformation of starch to cane 
sugar in the sweet potato in storage. Evidence that the changes proceed 
in this manner was obtained by a study of the process at low tempera¬ 
tures by which the rates of the different steps in the series of changes 
are unequally modified. 3 It was thus shown that the production of 
reducing sugar antecedes the formation of cane sugar. That a further 
separation of the various steps in this transformation, or possibly a 
suppression of one or more of the phases of the process, could be brought 
about by other means, such as changes in oxygen pressure, seemed not 
improbable, especially since Cruickshank in 1797 4 had observed that 
soaked barley seeds failed to become sweet in the absence of oxygen, 
and Boysen-Jensen 5 more recently found that cane sugar was not formed 
1 Miyaki, K. on the nature op the sugars pound in the tubers op sweet potatoes. In Jour. 
Biol. Chem., v. ai, no. a, p. 503-506. 1915. 
2 Hasselbring, Heinrich, and Hawkins, I,. A. physiological changes in sweet potatoes during 
storage. In Jour. Agr. Research, v. 3, no. 4, P* 33*“3 42. 1915. Literature cited, p. 341-342. 
* Hasselbring, Heinrich, and Hawkins, L- A. carbohydrate transpormations in sweet pota¬ 
toes. In Jour. Agr. Research, v. 5, no. 13, p. 543-560. 1915. 
* Cruickshank, William, some experiments and observations on the nature op sugar. In 
Rollo, John. An account of two cases of the diabetes mellitus . . . v. a, p. a 10-336. London, 1797. 
Reprinted in Jour. Nat. Phil., Chem., and Arts [Nicholsonl, v, 1, p, 337-341. 1797- French trans. by 
Guyton in Ann. Chim., v. as, p. 37-5©- 1798. 
8 BoYSEN-JENSEN, P. fjBER SYNTHETISCHE VORGANGE IM PPLANZI 4 CHEN ORGANISMUS. I. DIE 
rohrzuckersynthese. In Biochem. Ztschr., Bd. 40, Heft 5/6, p. 420-440, 2 fig. 1912. 
Journal of Agricultural Research, 
Washington, D. C. 
on 
Vol. XIV, No. 7 
Aug. 12,1918 
Key No. G-ist 
(273) 
