04 Fakultät Energie-, Verfahrens- und Biotechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5
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Item Open Access Cytokinins in different cell compartments after treatment with [8-14C]-kinetin : [abstract](1985) Graf, Josef A.; Dietz, B.; Kull, Ulrich-Item Open Access Altered lipid matrix changes energy distribution in thylakoids(1987) Graf, Josef A.; Strasser, Reto J.; Kull, UlrichPhotosynthetic membranes differ from other cellular rnembranes in that they have a thylakoid specific lipid composition and a high degree of polyunsaturated fatty acids. The typical acyl lipid complement of thylakoids seems to have two functions: the organization of the membrane matrix in which the pigment protein complexes are embedded and the indirect structure-function relationships between lipid matrix and pigment protein complexes which influence energy distribution behaviour. The role of high amounts of polyunsaturated fatty acids and indirect structure-function rclationships can be studied by inhibiting fatty acid desaturation sequence with pyridazinone herbicides.Item Open Access Structure-function-relationship in thylakoids influenced by the pyridazinone BAS 13-338 (SAN 9785)(1987) Graf, Josef A.; Strasser, Reto J.; Kull, UlrichThe pyridazinone SAS 13-338 (SAN 9785) inhibits the desaturation sequence leading to polyunsaturated fatty acids, mainly of glycolipids. Parallel to the inhibition of fatty acid desaturation in the presence of the pyridazinone. changes in energy-distribution parameters have been observed. These data indicate that the amount of polyunsaturated fatty acids in glycolipids is strongly correlated with excitation, trapping, grouping and dissipation, but not with spillover. Functional changes in energy distribution induced by SAS 13-338 are interpreted as a consequence of structural changes in the lipid matrix, which may imply a structure-function relationship between pigment protein complexes and the surrounding lipid environment in thylakoids.Item Open Access Influence of calcium and calcium and calmodulin antagonists on the cytokinin-induced amaranthin accumulation in Amaranthus tricolor(1989) Vallon, Ulrike; Graf, Josef A.; Kull, UlrichThe concentration of kinetin and kinetinriboside plays an essential role in the induction of amaranthin accumulation in cotyledons of Amaranthus tricolor during germination. The dose/effect ratio shows that kinetin induced 3- to 3.5-fold more amaranthin than kinetinriboside at the same molecular concentration. Various concentrations of exogenous Ca2+ did not influence the effects of kinetin on the betacyanin synthesis. However, when Ca2+ was applied together with kinetinriboside, the amaranthin production was stimulated. Time-course experiments show a lag phase of 16 h starting from the incubation with kinetin and a distinct increase of amaranthin thereafter. If the seedlings were treated simultaneously with kinetin and Ca2+, the increase of amaranthin started after 12 h. At 16 h of incubation in kinetin/Ca2+, the amount of amaranthin increased significantly compared to controls incubated with kinetin alone. If Ca2+ ions (16 h kinetin/Ca2+ incubation) were removed from the medium after 2 h, 4 h, and up to 14 h, the amaranthin content was enhanced compared to controls without Ca2+. The stimulating effect was highest in the presence of Ca2+ for 8 h. These data show that exogenous Ca2+ stimulated the amaranthin synthesis mainly during the first 12 h of incubation. The Ca2+ antagonists EGTA, chlorotetracycline, and CoCl2 reduced the amaranthin content up to 80%. The calmodulin antagonists chloropromazine and trifluoperazine inhibited the betacyanin accumulation up to 97% when applied at the beginning of the incubation. Neither Co2+ nor trifluoperazine after 12 h of preincubation in kinetin had inhibiting effects on the amaranthin production. Therefore, we presume that a specific period of competence is required for calmodulin-mediated Ca2+ effects on the accumulation of amaranthin induced by cytokinins in the seedlings of Amaranthus tricolor.Item Open Access State-1 state-2 transition influenced by herbicides which modify fatty acid composition in leaves(1984) Graf, Josef A.; Strasser, Reto J.; Kull, UlrichInteractions of herbicides with photosynthetic membranes are still not solved in many respects. Three different modes of action have been reported for pyridazinone herbicides : inhibition of (1) photosynthetic electron transport (2) carotenoid biosynthesis and (3) fatty acid desaturation in the galactolipid fraction of chloroplasts. The pyridazinone BASF 13-338 (=SAN 9785) used in our investigations has no effect on pigmentsynthesis and photosynthetic activity but affects fatty acid desaturation in leaves. Cerulenin an antibiotic from the fungus Cephalosporium caerulens inhibits fatty acid synthesis generally. Both herbicides act indirectly on photosynthesis because they alter the mobility of photosynthetic units in the membrane.Item Open Access Changes of the membrane matrix rearrange pigment complexes : abstract only(1984) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich-Item Open Access Pyridazinone/cytokinin antagonism regulates energy distribution : [abstract](1986) Graf, Josef A.; Strasser, Reto J.; Kull, Ulrich-