Browsing by Author "Hoffmann, Franz"
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Item Open Access Effects of abscisic acid on photosynthesis of protoplasts from Petunia hybrida(1974) Hoffmann, Franz; Kull, UlrichProtoplasts from plants are suitable experimental objects for investigations in which substances are taken up by cells, since chemicals can reach the cell surface directly. Therefore, it is convenient to use them for experiments concerned with effects of phytohormones on metabolism. So far, some work on the application of auxins 1-3 has been described, and recently we have made some investigations on the influence of zeatin on photosynthesis and respiration of isolated mesophyll protoplasts from Petunia.Item Open Access Einfluß von Zeatin auf Atmung und Photosynthese der Mesophyll-Protoplasten von Petunia(1975) Kull, Ulrich; Hoffmann, FranzApplication of 1 ppm zeatin raises the respiration rate (measured by the Warburg method) of leaf mesophyll protoplasts of Petunia hybrida by about 50% after 4 h; afterwards there is a rapid decrease. While the rate of respiration in the controls rises after 5 to 6 h, 1 ppm zeatin has a strong inhibitory effect. When the protoplasts are incubated with 0.1 ppm zeatin, the rise in the rate is much slower, and after 7 h the rate is 30 % higher than in the controls. Abscisic acid (10 ppm) decreases the respiration rate so that after 5h it is less than half that of the controls. Later on there is a rise in the controls, perhaps caused by senescence promoting effects of abscisic acid. The photosynthetic rate of the mesophyll protoplasts measured by 14CO2 fixation decreases with increasing age of the preparation. The protoplasts previously incubated with zeatin for 1 to 3 h show an increase in photosynthesis: with 0.1 ppm zeatin the 14C-fixation rate is higher the longer the hormone could operate. With 1 ppm zeatin we get a typical optimum curve similar to that for respiration. These optimum curves indicate the inhibitory effect of high concentrations of zeatin on respiration and photosynthesis.Item Open Access Manometrische Atmungsmessungen an Protoplasten von Petunia(1975) Hoffmann, Franz; Kull, Ulrich; Potrykus, IngoIsolierte Protoplasten höherer Pflanzen scheinen so manchen experimentellen Vorteil für die Beantwortung unterschiedlichster Fragestellungen der Botanik zu bieten. Während sich die überragende Mehrzahl der vorliegenden als auch ein immer noch hoher Prozentsatz der neu erscheinenden Protoplasten-Publikationen mit Problemen der Isolierung und Feinstruktur beschäftigt, liegen über das Verhalten der Protoplasten an sich nur wenige Arbeiten vor. Über die Atmung von Protoplasten fanden wir keine Angaben. Zur Charakterisierung der Protoplasten von Petunia haben wir daher die Atmungsraten untersucht.Item Open Access Markierung von Kohlenhydraten in Blättern nach Fütterung von 14C-Galaktose(1971) Hoffmann, Franz; Kull, Ulrich; Jeremias, KurtIn vorliegender Untersuchung wurden nun Blätter einer Raffinosezucker-führenden Art (Lamium album) und einer Art, deren Blätter keine Galaktoside der Saccharose enthalten (Phaseolus vulgaris), in Parallelversuchen mit 14C-Galaktose gefüttert und die Markierung der Kohlenhydrate untersucht.