RESPIRATION OF SWEET POTATO STORAGE-ROT FUNGI 
WHEN GROWN ON A NUTRIENT SOLUTION 
By L- L. Harter, Pathologist, and J. L. Weimer, Assistant Pathologist, Cotton, 
Truck, and Forage Crop Disease Investigations, Bureau of Plant Industry, United 
States Department of Agriculture 
INTRODUCTION 
Respiration in plants has been a favorite subject for botanical research 
for many years. Most of the earlier work was done with chlorophyll 
green plants, or parts of plants, some of the classical studies having been 
made upon seeds. The results of these researches have given us a better 
insight into the metalbolism of flowering plants, with some facts regard¬ 
ing the utilization of carbohydrates in respiration. Hasselbring and 
Hawkins (9) 1 in studying the respiration of the roots of sweet potatoes 
found that the reducing sugars were the immediate source of respiratory 
material. The cane sugar remained relatively stable when once formed 
and did not appear to be readily utilized so long as starch and other car¬ 
bohydrates were present in abundance. 
The results of investigations reported by the writers (23) show that 
the fungi responsible for most of the decay of sweet potatoes—namely 
Fusarium acuminatum E. and E. emend. Wollenw., Sclerotium bataticola 
Taub., Diplodia tubericola (E. and E.) Taub., Penicillium sp., Mucor 
racemosus Fes., Botrytis cinerea Pers., Rhizopus tritici Saito, and Sphae- 
ronema fimbriatum (E. and H.) Sacc.—with the exception of the last- 
named organism, can utilize glucose as a source of carbon. Not only 
were these fungi able to use glucose in various amounts, but they also pro¬ 
duced certain changes in the hydrogen-ion and osmotic concentrations of 
the culture medium. Some of the sugar was used in producing mycelium 
and in supplying energy for carrying on the vital processes of the organ¬ 
isms, although no doubt a part of it was utilized for other purposes. 
The investigations reported in^this paper were designed to throw fur¬ 
ther light (1) upon the question of the availability of glucose as a source 
of carbon for these same fungi, Sphaeronema fimbriatum excepted, and 
(2) upon the amount of the carbohydrate used in respiration as measured 
by the amount of carbon dioxid (C0 2 ) given off. 
methods 
In these investigations the fungi studied were grown in Erlenmeyer flasks 
on a liquid synthetic medium. The apparatus was set up in duplicate, 
1 Reference is made by number (italic) to “Literature cited,” p. 225-226. 
(211) 
Journal of Agricultural Research, 
Washington, D. C. 
xo 
Vol. XXI, No. 4 
May 16, 1921 
Key No. G-330 
