Photoautotrophic Chenopodium rubrum Cell Suspension Cultures Resistant against Photosynthesis-Inhibiting Herbicides II. Physiological and Biochemical Properties

Jutta Thiemann and W olfgang Barz Institut für Biochemie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität, Hindenburgplatz 55, D-48143 Münster, Bundesrepublik Deutschland Dedicated to Professor Rolf Wiermann on the occasion o f his 60th birthday Z. Naturforsch. 49c, 791-801 (1994); received May 30/July 11, 1994 Chenopodium rubrum, Photoautotrophic Cell Cultures, Herbicide Resistance, Photosynthesis Eight photoautotrophic cell cultures of Chenopodium rubrum, which are resistant against the photosystem II inhibitor metribuzin, were characterized for their growth parameters, chlorophyll content and photosynthetic capacity. Herbicide resistance of the eight lines results from different mutations in the D 1 protein of photosystem II, which is the target for different photosystem II inhibitors. In the presence of 10~5 m metribuzin the eight lines showed substantial growth reduction depending on the degree of resistance, and this effect is explained by a reduced electron transport in photosystem II. The impaired photosynthetic capacity of the green cells in the presence of high metribuzin concentrations, leads to com­ pensation effects similar to shade accommodation of plants. Adaptation includes an increase of the chlorophyll content, a decrease of the chlorophyll a/b ratios as well as an increase of thylakoid stacking and cell number per unit fresh weight. In the absence of the herbicide photosynthetic electron transport is not impaired, as indicated by measurements of electron transfer rates in photosystem II and flash-induced reduction kinetics of P-700+. In summary the alterations of the D 1 protein of the eight cell lines do not result in a reduced electron transport in photosystem II.