The Effect of Temperature on the Behavior of Malic Acid and Starch in Leaves of Bryophyllum calycinum Cultured in Darkness.

Abstract

Excised leaves of B. calvcinum were cultured in water in darkness at 24[degree] and 6[degree]C in parallel experiments. The stimulation of the utilization of starch and the formation of malic acid at the lower temperature as compared with the higher temperature which has been known for some years was amply confirmed. The observed effects are tentatively ascribed to a difference in the influence of temperature on the rates of the reactions which on the one hand lead to the synthesis of malic acid and the utilization of starch and on the other hand to the loss of malic acid. The net rate of these latter reactions appears to be depressed at low temperature so that malic acid accumulates continuously whereas at higher temperatures it reaches a maximum and then diminishes. Similar considerations seem to apply to the behavior of an unfermentable carbohydrate component which is not sedoheptulose. They also appear to be applicable to the behavior of citric acid, but with this substance the effects are only slowly established and would require a prolonged period of culture for their full demonstration at low temperature.