The Behavior of Isocitric Acid in Excised Leaves of Bryophyllum Calycinum During Culture in Alternating Light and Darkness

In an earlier study of the diurnal variation of organic acids and starch in excised leaves of Bryophyllum calycinum (3), it was observed that the quantity of isocitric acid present did not change significantly during a threeday period of culture in water under greenhouse conditions of illumination. Because of the contrast between the behavior of this substance and that of malic and citric acids, it seemed essential to repeat the experiment under even more carefully controlled conditions and to employ improvements in the method for the determination of isocitric acid which have now become available (1). The outcome has been a confirmation of the earlier experiment. The changes in the quantity of isocitric acid in Bryophyllum leaves exposed to normal diurnal alternations of light and darkness, if significant at all, are scarcely in excess of the combined errors involved in the sampling and in the method of determination.