Zur Analyse des CO2-Austausches von Bryophyllum

Summary Starch consumption during the dark period in detached phyllodia of Bryophyllum tubiflorum is inhibited, when the phyllodia are held in an atmosphere free from carbon dioxide during the night. This is true also in other succulent plants with Crassulacean acid metabolism=CAM (examined were Bryophyllum calycinum and Sedum morganianum). This effect seems to indicate that the role of starch in CAM is production of CO₂ acceptors rather than production of carbon dioxide by respiration. If the CO₂ acceptors are not used, starch consumption comes to an end.This hypothesis could also explain results of experiments in which phyllodia were held at different temperatures during the dark period, and net CO₂ fixation, starch loss and malate gain were determined. At 10° CO₂ uptake was at a maximum (the necessary supply of CO₂ acceptors must have therefore been at a maximum, too). Under these conditions there was the greatest amount of starch consumption. At 23° C, CO₂ uptake was clearly lowered, and this was also true for starch consumption. At 35° C net CO₂ uptake was balanced by net CO₂, output (no CO₂ acceptors were needed in CO₂ dark fixation). At this temperature no starch loss could be measured.