RESPIRATION IN PLANTS 
229 
Storage temperature does not fall below 3° C. In a previous work, 
the writer found that at temperatures around 0° C, or below, the 
catalase activity is actually less than in normally stored tubers. 
This was accounted for in the destruction of the catalase by free acids. 
The presence of free acids is demonstrated by the acid exudate from 
tubers stored at this very low temperature. 
Table IV 
Effect of Cold Storage on Respiration of McCormick Potatoes 
Milligrams of CO2 per Kilo per Hour 
Date of Measurement 
Ratio 
Tubers Stored at Room 
Tubers Stored at 3° for 
Temperature 
20 Days 
February 18 
12.50 
35-15 
I : 2.81 
Table V 
Catalase and Oxidase Activity in the Juice from McCormick Tubers after a Period of 
Cold Storage 
Manometer Readings Expressed in Centimeters of Mercury, Using .1 cc. of Juice 
for Catalase and .5 cc. for Oxidase 
Experiment 
Tubers Stored at Room Temperature 
Tubers Stored at 
3*^ C. for 20 Days 
Catalase 
Oxidase 
Catalase 
Oxidase 
I 
+ 2.4 
- 3-0 
+ 4-2 
- 2.9 
2 
+ 3-5 
- 2.9 
+ 4-5 
- 2.7 
3 
+ 3-6 
- 2.9 
+ 4-2 
- 2.3 
4 
+ 2.4 
+ 4-4 
Average . 
+ 2.97 
- 2.93 
+ 4-32 
- 2.63 
Effect of Greening: Greening of potato tubers in light is a very 
familiar phenomenon. One of the physiological changes concomitant 
with the greening is a rise in respiration. This offered a good oppor- 
tunity to make a quantitative study of catalase and oxidase in rela- 
tion to a change in respiration naturally induced. In connection 
with other work, the writer found in different stages of greening, a 
much greater rise in respiration than in the experiments here recorded. 
Even with the degree of acceleration shown in Table VI there is an 
increase in catalase in the green tubers. But again, the oxidase 
activity is not increased with a rise in respiration; in fact, it is a little 
less in the green tubers than in the ungreened ones. 
