Aug. is, 1918 Effect of Oxygen Pressures on Metabolism of Sweet Potato 275 
EXPERIMENTAL WORK 
EXPERIMENTS AT PRESSURES GREATER THAN ONE ATMOSPHERE 
Two experiments were conducted under pressures greater than one 
atmosphere. These require only a brief discussion, since in both cases 
the sweet potatoes were killed. In the first experiment the potatoes 
were stored for 10 days in air at 30° C. and under a pressure of 10 atmos¬ 
pheres. At the end of that period the potatoes showed a few spots where 
organisms had developed; otherwise the tissues were intact but killed. 
No analyses of these were made. In the second experiment the potatoes 
were kept for 5 days in oxygen at 30° and at a pressure of 5 atmospheres. 
These also were killed. The tissues were watery but firm and, so far 
as could be observed microscopically, were free from fungi and bacteria. 
Two of the halves were analyzed. The results are given in Table I. 
In this and in the subsequent tables the halves analyzed at the beginning 
of the experiment are marked “a,” and the stored halves are marked “b.” 
Table I. —Changes in composition of sweet potatoes stored for § days in oxygen at jo° C. 
and at a pressure of 5 atmospheres 
Sweet potato 
No. 
On the basis of fresh material. 
On the basis of dry matter. 
Moisture. 
Starch. 
Reducing 
sugar as 
glucose. 
Cane 
sugar. 
Starch. 
Reducing 
sugar as 
glucose. 
Cane 
sugar. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
Per cent . 
Per cent. 
Per cent. 
ia. 
75 - 50 
17.09 
°- 3 * 
I* 63 
69. ,76 
I. 27 
6. 65 
ib.. 
73 - 8 S 
17.78 
75 
•63 
67.99 
6. 69 
2. 41 
6a. 
71. 14 
21.39 
.40 
I. 72 
74.12 
i- 39 
5 - 9<5 
6b. 
7 1 - °4 
20. 70 
1. 81 
•95 
71.48 
6.25 
3- 28 
The data show that under these conditions the hydrolysis of starch 
proceeded to a very limited extent, and that not only did no synthesis 
of cane sugar take place but cane sugar disappeared. As a result of the 
hydrolysis of starch and cane sugar there was a considerable accumula¬ 
tion of reducing sugar. To what extent these changes took place in the 
living potato it is not possible to say. It is likely from the disappearance 
of cane sugar that the roots were quickly killed and that the synthesis of 
cane sugar at least does not go on in killed tissues. The hydrolysis 
of starch also is greatly retarded. Since the whole problem of the 
effects of high pressures on the metabolism of the plant organs requires 
a detailed investigation, no further experiments in this field were con- * 
ducted at this time. 
EXPERIMENTS AT ATMOSPHERIC PRESSURE 
In the first set of experiments at atmospheric pressure different lots 
of halved sweet potatoes were stored for five days in oxygen, air, and 
