Abstract
1. Twenty four hours after 14CO2 feeding to the leaves, malic acid had the highest level of total and specific radioactivity among the organic acids extracted from the juice vesicles, and citric acid had the second highest total activity. An unidentified acid compound had a relatively high activity.
2. Pyruvic acid-2-14C was fed as a substrate for acid formation to the one young fruit on a shoot, and NaH14CO3 was fed as a source of carbon-dioxide to the other young fruit through the pedicel. After three hours of pyruvic acid feeding, malic acid, citric acid and aspartic acid were the major labelled compounds in the vesicles. Then, a marked increase and redistribution of activity in acids took place with time, and the levels of total and specific activity in citric acid increased steadily. The sorts of labelled compounds into which activity was incorporated from NaH14CO3 were essentially similar to those in pyruvic acid-2-14C feeding.
3. These results seem to support the theory that the dark fixation of carbondioxide plays an important role in the synthesis of the organic acids in citrus fruit vesicles.
