Änderungen des Chloroplastenpigment-Spiegels bei Sphagnum magellanicum im Verlauf der Synthese von Sphagnorubin und anderer membranochromer Pigmente

Abstract

A method is described for the determination of the relative content of the red wall pigments synthesized by Sphagnum mag. and other Sphagna cooled to + 0.5°C during a dark period (12 h), when the threshold of light intensity in the following light period (12 h) does not fall short of approximately 2000 lx. The synthesis of sphagnorubin and other wall pigments in the capitulum is linked with characteristic changes in the content of the chloroplast pigments. The content of chlorophyll a decreases comparatively more quickly than that of chlorophyll b; considerably more distinct are the variations in the carotenoid/chlorophyll quotients. It thus becomes evident that the relative content of carotenoids increases during the synthesis of red wall pigments. No significant influence on the content of chloroplast pigments in the 4–5 cm long subapical stem segments cart normally be demonstrated in such an experiment. In agreement with the knowledge that no synthesis of wall pigments takes place without analogous changes in the content of the chloroplast pigments, no sphagnorubin synthesis takes place in this region under the described conditions. That this is merely the consequence of insufficient illumination can be proved by inducing changes in the chloroplast pigment content and synthesis of wall pigments, which then take place when the capitula have been removed prior to the start of the chilling experiment. The colouring produced by a chilling experiment is reversible in so far as it does not involve an especially strong disturbance of metabolic processes. Within a few days after the end of a chilling period which has led to complete colour change of the sphagna capitula, an essential amount of the red pigments in the cell walls will again be mobilized and metabolized. The synthesis of chloroplast pigments is first manifested by the chlorophylls, whereas the synthesis of carotenoids initially retarded. This is especially true of the pigments of the «xanthophyll-cycle».