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IntroductionThe study of carbohydrate metabolism has received considerable attention in the animal domain. It has been assumed by many that carbohydrate metabolism in higher plants follows a similar path. Many investigators have contributed toward the elucidation of this assumption but the final goal has not yet been reached. The literature on the subject has been ably surveyed by VICKERY et al. (19), PUCHER et al. (11), and SIDERIS et al. (16) and will not be reviewed in detail in the present paper.The reactions occurring during the metabolism of carbohydrates are separated into two main schemes-one taking place under anaerobic, the other under aerobic conditions. The problems having received the most attention are largely concerned with anaerobic processes such as the fermentation of sugar to ethyl alcohol and the formation of lactic acid. The reactions leading to the complete oxidation of carbohydrates under aerobic conditions (i.e. respiration) are not as well understood.The object of the present investigation is to study the possible steps involved in the respiratory mechanism of plant tissues inasmuch as they are connected with the aerobic path of carbohydrates, by determining the extent to which some of the metabolic intermediates known for animal tissues fit into the plant domain.The program of research was planned to include several parts, the first being the study of the growth of chlorella when supplied with organic acids known to enter in the path of aerobic carbohydrate metabolism in animal tissues. Other portions are concerned with the effects of organic acids on respiration and the study of the action of various enzymes and enzyme inhibitors. These will be reported in subsequent publications. Materials and methodsMATERIALS.-The strain of chlorella used was originally isolated from soil by WANN (20) and has been maintained in pure culture in the Plant Physiology laboratory at Cornell University. According to CLARK (2), the species has not been described taxonomically.The chlorella used were all derived from a single cell obtained by plating out a suspension of cells at the beginning of the investigation. The Stock culture vessels were inoculated with a transfer loop and the organic acid cultures were inoculated with pipettes. The pipettes used for inoculation were sterilized in a hot air oven at 160°C to two hours. A small wad of cotton was inserted in the mouth end before sterilization.The flasks were then placed in the insulated thermostated chamber as described by MANDELS (8) and were automatically shaken for five minutes every hour. The light intensity applied for stock cultures was about 500 foot candles. On the other hand, the organic acid cultures were kept in the dark. For this purpose, the insulated chamber was protected from light by four layers of black cotton cloth. In both cases, the temperature of the chamber was adjusted to 280 C ± .5°.In preparing the inoculum for organic acid cultures, a known amount of cells was needed to permit an accurate measurement of growth. To free the...

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IntroductionIn a series of studies (16, 18, 20) on the organic acids of citrus fruits, the authors have pointed out that large amounts of organic acids exist in the juice of the pulp, as compared with exceptionally low concentrations in the peel. The vascular system of the fruit is confined chiefly to the mesocarp (albedo), and the latter thus serves the important function of transporting water and solutes from the tree to the juice vesicles of the pulp. Since these vesicles contain relatively large amounts of organic acids, it would appear that higher concentrations than are present should occur in the mes6carp, that is, if the total organic acid radical is transferred from leaves to vesicles. This situation led to the postulation that the organic acids of the juice are possibly synthesized in the pulp vesicles rather than in the leaves and subsequently transferred to the pulp. Quantitative determination and identification of the organic acids present in the leaves should provide fundamental data necessary for a solution to this problem.The present investigation has been concerned with the extraction of the organic acids from ground, dried Valencia orange leaves with absolute ethyl ether, and with the subsequent determination of total and individual organic acids in the water solution of the ether extract. In addition, water-soluble organic acids were extracted directly from aliquot portions of the dried leaf samples, and these data were compared with the total and individual acids extracted with ether. This information revealed the amounts of organic acids present in the leaves in soluble and insoluble states. The influence of these factors on the buffer system of the leaves is discussed. Furthermore, certain relationships are proposed concerning the synthesis and translocation of organic acids from the leaves to the fruit.