Abstract
The present studies were performed to determine the amount of assimilated substances and clarify the physiological changes in the growing leaves of Colocasia esculenta (variety: Uhan) which was planted on June 1, 1957.
Growth of the leaves in length after unrolling was 14-40 percent of that before unrolling.
The leaves of the upper parts grew longer until the middle of August and no growth was observed thereafter.
The dry weight per unit area of the leaves (mea-sured by punch method) increased with increasing of their ages and the rate of increase was highest in the 10th-12th, 12th-14th and 13th-14th leaves (their unrolling times were June 31, August 18 and August 27 respectively).
The amount of the substances assimilated were highest from late July to late August, and later it decreased gradually. These changes paralleled to the average daily temperature and they had sudden-ly decreased when it went down below 20°C.
The values of the specific gravity of the leaf powder were slightly low until the middle of Sep-tember, and somewhat increased thereafter.
Concentration of the water extract of. tissue powder was highest toward the end of the growing period and were lowest in late August.
Specific electric conductivity of the same extract was highest in the early growing stage and lowest in late September.
Accordingly, the changes of these values suggest that the physiological activities of the leaves are highest in the early growing stage (from July to early September) and remarkably decrease in the middle September.
From these facts it is considered that the physi-ological chahges occur in the leaves of Colocasia esculenta in the middle of September.
