STUDIES IN THE METABOLISM OF CRASSULACEAN PLANTS: THE EFFECT OF TEMPERATURE UPON THE CULTURE OF EXCISED LEAVES OF BRYOPHYLLUM CALYCINUM

Abstract

When Bryophyllum calycimum leaves are detached from the plant and cultured in water in darkness at ordinary room temperature, the course of the changes in composition with respect to the organic acids, the protein and the starch depends upon the time of day at which the samples were collected (5). If leaves are taken in the afternoon at a time of low acidity and low protein content, there is a prompt increase both in acids and in protein and a corresponding decrease in the high starch content. Alternatively, if the leaves are collected in the morning at a time of high acidity and protein content, both acids and protein fall and the starch increases. These changes take place within the first 24 hours and appear to be expressions of the normal metabolism of this species. After 24 hours, certain other changes begin to make their appearance; in particular, for leaves collected in the afternoon, the acids and the protein, after reaching maxima, begin to fall and the starch may increase during the second day of the culture period. It seems possible that this reversal in the direction of the chemical changes represents the initiation of the catabolic changes that inevitably follow excision of a leaf. Accordingly, in order to study this possibility further, an experiment was carried out in which the culture period at 200 C. was prolonged to 6 days and, in addition, parallel cultures were carried out at 90 C. and at 10 C. in the hope that, at the lower temperatures, the reactions might proceed more slowly and certain of the details might be revealed more clearly. The present paper gives a report of this experiment.

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

“…In 1938, Wolf (14) presented data to show that, at a temperature of 7 to 50 C, the production of acid and the utilization of starch were apparently both stimulated as compared to the behavior of these substances in leaves cultured at about 220 C, and similar observations have been reported in a previous paper from this laboratory (4). Additional evidence with respect to the favorable effect of low temperature on the formation of acid has recently been given by Thomas and Ranson (5).…”

“…If it may be assumed that the metabolic reactions observed in the present lot of leaves wvere fundamentally the same as those seen in previous sets of samples studied in this laboratory (4,9), citric acid behaved in a similar manner although with this substance the reactions that led to synthesis were slower than those by which malic acid was produced. Furthermore, the reverse reactions which lead to the loss of citric acid do not become effective until after the lapse of many hours.…”

“…Nevertheless, the maximum which citric acid may reach (4) was greater at low than at high temperature ancl the general behavior was thus closelv analogous to that of malic acid, only the time scale is different.…”

“…However, an earlier experiment carried out in this laboratory (4) showed that, if culture is greatly prolonged, the quantity of citric acid formed at 90 C ultimately exceededl that formed at 200 C. The data suggested that, after 66 hours at 200 C, reactions which led to the utilization of citric acid gradually assumed dominance, although little evidence of such reactions was noted in the experiment at 90 C. Accordingly the general behavior of citric acid is fundamentally identical with that of malic acid; the differences observed merely represent differences in the rates of the reactions which affect malic acid on the one handl and citric acid on the other and in the effect of temperature upon these rates.…”

Respiration Studies on Chlorella. I. Growth Experiments With Acid Intermediates

“…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.…”