Ulrich Kull

Prosomes exist in plant cells too

A 19S particle was purified from tobacco (Nicotiana rustica) leaf cells. Its density was determined as 1296 g/cm3 in Cs2SO4-DMSO gradients, indicating the presence of RNA and protein. Polyacrylamide gel electrophoresis (PAGE) revealed eight distinct proteins in the range of 20-30 kD and RNA in the range of 70-80 nucleotides. Electron microscopic examination showed the same raspberry-shaped structure with a central depression as described for prosomes. We conclude that tobacco 19S particles represent small cytoplasmic complexes, possessing biochemical and structural characteristics similar to the hither-to known prosomes of animal cells.

Die fettsäurezusammensetzung der verseifbaren lipide aus rinden von Populus balsamifera im Jahresgang

Summary 1. The fatty acid patterns were investigated qualitatively and quantitatively by gas liquid chromatography in monthly intervals. The contents of fatty acids were evaluated as percentage of total fatty acids (shown in table 1) and as percentage of dry weight of barks (table 2). 2. Seventeen different fatty acids were found, twelve of them could be measured quantitatively during the whole year. The most important compounds are palmitic, oleic, linolic, and linolenic acid; myristic, myristoleic and behenic acid are found in considerable amounts, too. During spring another acid is predominating, which was tentatively identified as margarinic acid. 3. During winter the contents of linolenic and especially of linolic acid are raised, the latter being the predominating acid during this season. The amounts of palmitic acid (in % of dry weight) shows only slight variations in the course of the year. Expressed as % of total fatty acids it has a minimum in winter. 4. The findings are discussed in relation to the influence of temperature on storage of lipids and on biosynthesis of fatty acids.

EFFECT OF CYTOKININS ON THE LIPID FATTY ACIDS OF LEAVES

Kinetin and zeatin were administered to leaves of intact plants of Coleus, Impatiens and Populus in long-term experiments (4 weeks and the variations of the fatty acid content of saponifiable lipids determined. In the same species there are no significant differences between the effects of the two cytokinins. In Impatiens and Populos the content of linolenic acid increases. The behaviour of palmitic and linoleic acids is variable. Coleus plants were treated with zeatin at 15 and 25°. At the higher temperature the hormone causes a distinct rise of palmitic and a diminution of linolenic acid.

Evidence of cyclic-AMP uptake into plant cells.

Reports of investigations on the effects of applied cAMP in higher plants are contradictory. Degradation of cAMP is catalyzed by homogenates from various plant species. However, it has not been convincingly demonstrated that exogenous cAMP penetrates the tissues and enters the cells.

Der Stickstoffhaushalt immergrüner mediterraner Hartlaubblätter

The seasonal variations of major nitrogenous components (total N, protein N) in sclerophyllous leaves of four mediterranean species - Ceratonia siliqua, Olea europaea var. sylvestris, Pistacia lentiscus and Quercus coccifera - were investigated throughout the whole lifetime of the leaves. The leaf-longevity of the first two species mentioned is about two yars, that of the latter two species is somewhat longer than one year. As reference values the raw fibre content and the total chlorophyll content of the leaves were also measured. The raw fibre content increase during leaf-growth, there-after it remains constant. In the leaves having a lifetime of two years, in the spring of the second year an additional increase, although weak, is observed. The chlorophyll content rises during the leaf growth, then remains unchanged for some time, but begins to decrease early. In the leaves of Ceratonia and Olea the shrinkage is recognized already in the spring of the second year. During the period of senescence, the decrease of chlorophyll a is more distinct than that of chlorophyll b. The total N content in all cases decreases during leaf-growth and then remains constant. In Ceratonia leaves it is reasonably high considering that it is an evergreen species. Rather early the N-content begins to decrease; which is intensified during the last months of the lifetime the leaves. This is due to the well-known export of N-compounds from senescent tissues. In Ceratonia leaves the N-content increases during the first winter; obviously they serve as N-storage organs. The content of protein-N in all species shows essentially the same variations as that of total N. Results of tests carried out in the months of January and August revealed that the proline content in the leaves of all species is higher during the drought period than during the cold period. Using the different reference-values, the variations of N-content during leaf longevity of the four species are discussed in connection with reflections on maintenance costs. Bei unseren bisherigen Untersuchungen zur Okophysiologie der Stoffspeicherung in mediterranen Hartlaubpflanzen wurde der Stickstoffhaushalt nicht einbezogen. Erstaunlicherweise gibt es bisher kaum Untersuchungen dazu. Sogar die Lebensdauer der Blatter von Hartlaubpflanzen des Mittelmeergebiets wurde am naturlichen Standort erst neuerdings genau festgestellt. Da der stickstoffhaushalt der Blatter in engem Zusammenhang mit Entwicklungs- und Alterungsvorgangen steht, wurde er nunmehr wahrend der ganzen Lebensdauer der Blatter von 4 mediterranen Hartlaubarten untersucht. Als Bezugsgrosen wurden neben der Trockenmasse auch die Grosen Rohfasergehalt und Chlorophyllgehalt der Blatter herangezogen. Es ist bekannt, das der Stickstoffhaushalt von Blattern durch Wassermangel erheblich beeinflust wird. Von besonderem Interesse war es daher, festzustellen, welche Auswirkungen die Sommertrockenheit am Standort auf den N-Haushalt mediterraner Hartlaubblatter hat.

Wirkungen von abscisinsäure auf den kohlenhydrat- und fettsäurehaushalt von Coleus blumei

Summary Abscisic acid (ABA) was applied in solutions of 10 ppm (38 μM/1) and 100 ppm (380 μM/1) to the apex of young plants of Coleus blumei. The plants showed a weak inhibition of longitudinal growth (significance α = 5 %). Application of the phytohormone in leaves and stalks decreased the content of soluble sugars and especially of starch (fig. 1). The fatty acid patterns of saponifiable lipids were investigated quantitatively by gas liquid chromatography. Expressed as % of total fatty acids the palmitic acid content is raised under the influence of ABA, while the content of linolenic and linoleic acids is diminished (table 1). In % of dry weight especially the latter two show decreased amounts (fig. 2). The findings are discussed in relation to the known effects of ABA on stomatal closure, photosynthesis, on changes of permeability of membranes, and in connection with earlier findings on the effects of cytokinins.

Determination of Phytotoxicity of Several Volatile Organic Compounds by Investigating the Germination Pattern of Tobacco Pollen

Summary Hydrated pollen of Nicotiana tabacum L. (var. xanthi nc) was exposed to different concentrations of several volatile organic compounds. The germination rate of the pollen was determined by applying a modified test procedure originally developed by Kappler and Kristen (1990). A stimulation of pollen germination resulting through a rise in pCO 2 was avoided by using a short exposure period. In the series of chlorinated ethanes, the ED 50 (and ED 25 ) values decrease with increasing number of chlorine atoms, which are correlated to a rise of the octanol-water partition coefficient. For the chlorinated ethenes a similar effect is probable, but less obvious. The toxicity of compounds with the same number of chlorine atoms is higher for ethane derivatives than for derivatives of ethene. The ED 50 and ED 25 values are compared with threshold values of physiological effects obtained after the application of 1,1,1-trichloroethane for 24 h to tobacco leaves. We presume that chlorinated hydrocarbons may cause stress even at lower concentrations than those suggested by the pollen test. Therefore the listed ED values (Table 1) should be considered as maximum tolerable values regarding phytotoxic effects in experimental investigations. For the important solvent 1,1,1-trichloroethane the ED 25 value of phytotoxicity is lower than 4 mg/L; according to literature the concentration supposedly having no effect on man is 1.9 - 5.2 mg/L.

Seasonal trends in energy contents of storage. Substances in evergreen gymnosperms growing under mild climatic conditions in Central Europe

Summary From the contents of the soluble sugars, starch, and total lipids measured at monthly intervals during the course of a year in leaves and barks of Taxus baccata, Juniperus communis, Thuja occidelltalis, Picea excelsa and Sequoiadendrom 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 (Fig. 9). Remarkably, according to this pattern the highest amounts of starch are found in the spring or early summer, the maximum contents of total lipids 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.

Physiologische Untersuchungen über Blattschleime I. Untersuchungen an Verbascum densiflorum

Summary With a modified method for the quantitative determination of mucilages, the content of leafmucilages of Verbascum densiflorum was determined during the biennial ontogenesis. The sugar composition was measured by thin-layer 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 days 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.

Localization of proteasomes in plant cells

SummaryProteasomes, also known as multicatalytic proteinase complexes, were localized in suspension cells of potato (Solanum tuberosum) by direct immunofluorescence using polyclonal antibodies labelled with fluorescein isothiocyanate. The method used allows an estimate of relative amounts of proteasomal antigens in different cell components. Proteasomes are present in the nuclei and the cytoplasm. The nucleoplasm contains small areas of weak fluorescence. The peripheral cytoplasm and possibly elements of the cytoskeleton show higher fluorescence than other parts of the cytoplasm. This indicates a localization of proteasomes similar to that known from animal cells.