PHYSIOLOGICAL BEHAVIOR OF ENZYMES AND CARBO- 
HYDRATE TRANSFORMATIONS IN AFTER- 
RIPENING OF THE POTATO TUBER 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 148 
CHARLES O. APPLEMAN 
Introduction 
An active growing period, followed by a period of rest, is a 
very general phenomenon among plants. Thus most seeds, 
tubers, and bulbs are structures whose growth processes have 
been arrested. Germination is simply a continuation of growth 
after the awakening from the rest period. The buds of the potato 
tuber, for example, will not grow, under the most favorable con- 
ditions, for several weeks after maturity; but after the awakening 
from this dormant condition they will grow under much less favor- 
able conditions in a cold cellar. 
Certain changes occur during the apparent dormancy, which 
are antecedent to the release of the abe processes, and these 
changes are known as “‘after-ripening.”” In many seeds the rest 
period is due to coat characters, which exclude or limit the supply 
‘of water or oxygen. After-ripening in such cases are processes 
which render the coats permeable to these substances. Often the 
processes of after-ripening are metabolic in character; this is 
especially true of tubers. 
Certain external agencies artificially applied have been found 
to accelerate the processes of after-ripening, and thereby greatly 
shorten the natural rest period. Miiier-THurGAU (1) has shown 
that exposure to o° C. for one month has this effect upon the 
resting potato tuber. Changes are thus brought about which 
break the rest period and allow growth to proceed several weeks 
earlier than under ordinary circumstances. He also found a 
great reduction of respiration, accompanied by an accumulation 
of sugars during exposure at low temperature. 
The following work is a further study of the metabolic wee 
Botanical Gazette, vol. 52] 
