Browsing by Author "Distelbarth, Heidrun"

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Open Access
Physiological investigations of leaf mucilages. 2, The mucilage of Taxus baccata L. and of Thuja occidentalis L.
(1985) Distelbarth, Heidrun; Kull, Ulrich
Seasonal variations of the content of leaf mucilages of Taxus baccata and Thuja occidentalis were determined. In Taxus the content is highest during the late winter and early spring and lowest in the summer. In Thuja it is highest in the winter, decreasing during spring and low in the summer months. Under the light microscope, Taxus mucilage was located in the vacuoles of mesophyll cells and that of Thuja in mucilage idioblasts. Temperature experiments show that storage of mucilage is not temperature dependent and is not reduced by prolonged darkness. Taxus mucilage consists of the sugars galactose, rhamnose, glucose, arabinose and xylose and contains a low percentage (<5%) of uronic acid. Furthemore, a peptidic component is found and shows annual variations from 6% to 15% of total mucilage. Seasonal variations of the sugar components are pronounced only during the spring in the period of intensive mucilage synthesis. Purified Taxus mucilage could not be separated into different components by gel chromatography. All fractions showed a similar composition of sugars and peptide. These findings, in addition to the IR spectra, lead to the conclusion that the mucilage is a proteoglycan and perhaps a mixture of polymers of similar molecular weights. Isolated and dried mucilage has a high water-binding capacity; at 96% relative humidity it equilibrates to 180%, and at 100% rh to 280-300% of its dry weight. From mucilage content and cell volume the mucilage concentration of the vacuoles can be estimated as being higher than 5-6%, which must give rise to a remarkable matric potential. It is suggested that the water-binding capacity of the mucilage plays an important role in stabilizing the water relations of the needles, thereby increasing frost resistance.
Open Access
Seasonal trends in energy contents of storage substances in evergreen gymnosperms growing under mild climatic conditions in Central Europe
(1984) Distelbarth, Heidrun; Kull, Ulrich; Jeremias, Kurt
From the contents of the soluble sugars, starch, and total lipide measured at monthly intervals during the course of a year in leaves and barks of Taxus baccata, Juniperus communis, Thuja occidentaliis, Picea excelsa and Sequoiadendron giganteum the energy contents of storage substances were calculated and their seasonal trends established. From Taxus and Juniperus the wood was investigated in the same manner. Furtheron, the seasonal trends in total N-contents of leaves and barks of Taxus, Juniperus and Thuja were measured. As energy storing substances the N-compounds are not important. From the seasonal trends of the N-contents a function of the old leaves as an important N-storage pool for the budding may by concluded. In the one year old needles of Picea and Taxus the carbonic acid contents were measured, from an energetic point of view the acids are not important as reserve-substances. From the seasonal trends of the energy contents in the different species a general pattern of storage in gymnosperms growing under mild climatic conditions in Central Europe was deduced. Remarkably, according to this pattern the highest amounts of starch are found in the spring or early summer, the maximum contents of total lipide are reached during autumn or early winter and the highest contents of soluble sugars are found in the winter. This pattern confirms earlier assumptions regarding the functions of different storage substances. The total energy contents decline during the growth period and reach their lowest values in the late spring and early summer. In the winter none of the species showed an extensive diminution of storage energy, but rather sometimes a rise was seen which points to a net production during the winter months. Thus, the highest energy contents in the leaves are often found in the winter. The old needles have an important function as storage sites in the evergreen gymnosperms.
Open Access
Significant role of taxus leaf mucilage in the water-balance : abstract only
(1983) Distelbarth, Heidrun; Kull, Ulrich
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