Physiologische Untersuchungen über Blattschleime. 1, Untersuchungen an Verbascum densiflorum

Abstract

Pflanzenschleime sind als Bestandteile zahlreicher Drogen in der Pharmakognosie seit langem bekannt. Die meisten Arbeiten über Schleime beschäftigen sich mit der Strukturaufklärung dieser oft sehr komplexen Heteropolysaccharide. Dagegen gibt es nur wenige Untersuchungen zur Physiologie, und die Ansichten über mögliche Funktionen gehen weit auseinander. In der vorliegenden Arbeit wurden das Verhalten der Blattschleime und ihrer Monosaccharid-Bausteine von Verbascurn densitiorum im Verlauf der Entwicklung untersucht. Tagesgänge, Dürre-, Hunger- und Temperaturversuche sollen Aussagen über die physiologische Bedeutung dieser Pflanzenstoffe ermöglichen.

With a modified method for the quantitative determination of mucilages, the content of leaf-mucilages of Verbascum densiflorum was determined during the biennial ontogenesis. The sugar composition was measured by thin-Iayer chromatography after hydrolysis. The mucilage consists of galactose, rhamnose, glucose, arabinose and xylose; in most cases ribose was also found in small amounts. Furthermore, 0.5% peptidic N could not be separated from the mucilage. The content and the composition of the mucilage depend on the ontogenetic status of the plants. The highest content is reached during blossom-time, the lowest in the summer of the first year. During ontogenesis an increase in mucilage content is correlated with a decrease in water content of the leaves. The changes in mucilage content, which were observed during ontogenesis, during a day's course in summer and in winter and in plants kept under dark conditions lead to the conclusion that the mucilage has no function as a storage substance. Plants held under different soil water conditions show varying mucilage contents. During ontogenesis and in plants subjected to warm temperatures during winter, a good correlation between sugar components of the mucilage and leaf water content is observed. The percentages of galactose and arabinose show changes which correspond to the fluctuations in leaf water content; on the other hand, the percentages of rhamnose and glucose show opposite changes. Taking into consideration the known water-holding capacity of mucilages the above findings suggest that these substances play a role in the regulation of water relationships in Verbascum leaves.