The Capacity of Leaves of Bryophyllum calycinum to Recover from Prolonged Exposure to Darkness or to Light.

Effect of Light upon the Behaviour of Citric Acid in Leaves of Bryophyllum Calycinum Salisb.

“…The important point, however, is that the relationship between the quantities of malic acid and starch, and that between citric acid and starch are almost equally close; the coefficients of correlation are almost identical with those for the organic acids versus pH. Furthermore, this relationship holds for both sets of samples, and similarly high coefficients have been found for the data obtained from many other sets treated in various ways (9,10 The conditions in the greenhouse during Experimlent E Xvere quite different froml those of Experiment A. During the 1st few hours, the temperature was low, and the rate of loss of malic acid was correspondingly slowv.…”

“…It presumably increased a little during the 1st few hours, but it has long been known that, after Bryophyllum leaves have been in darkness for about 12 hours, a slow loss of malic acid begins. A curve which shows this behavior in some detail is given in figure 2 of reference (10). The The enzyme mechanisms concerned with the metabolism of starch in these samples were thus also normally active.…”

“…An analogous case is the observation of a decrease in malic acid in the control experiments after 11 (or 10) hours in darkness in addition to the 9-hour night period (table II). MIany previous experiments (10) have shown that the content of malic acid passes through a maximum and then decreases after from 12 to 16 hours exposure of the leaves to darkness.…”

“…whlen all leaves were in position in the culture troughs and the initial control sample was placedl in the drying oven. The general technique of such culture experiments has been described in previous papers (9,10) in hich the methods of preparing the sanmples for analysis and references to the analytical methods used are also given.…”

Metabolism of Threo-Ds-Isocitric Acid in Detached Leaves of Bryophyllum calycinum

“…Bradbeer et al (3) explained this pattern of distribution by proposing that half the phosphoenolpyruvate, the main suggested CO2 acceptor in dark acidification, is already labeled. The labeled phosphoenolpyruvate could be formed from 3-P glycer- (10,12,13 The problem of distribution of materials within the leaf after uptake through the petiole w-as raised by the finding of a steep acropetal gradient of radioactivity in the leaf after the adminstration of glucose in the preliminary experiments. The question arises whether such a distribution is the rule wvith most leaves or whether it is limited to succulents or perhaps to Bryophyllum.…”