The Effects of the Herbicide Sethoxydim on Transport Processes in Sensitive and Tolerant Grass Species II. Effects on Membrane-Bound Redox Systems in Plant Cells

Angela Weber and Ulrich Lüttge Institut für Botanik, Technische Hochschule Darmstadt, Schnittspahnstraße 3—5, D-6100 Darmstadt, Bundesrepublik Deutschland Z. Naturforsch. 43c, 257-263 (1988); received December 23, 1987 Sethoxydim, Herbicide, Redox Systems, Isolated Organelles, Plasmalemma Leaf slices of sethoxydim-sensitive (Poa pratensis, Festuca ovina) and tolerant (Poa annua, Festuca rubra) grass species were found to be able to reduce extracellular ferricyanide by electron transport across the plasmalemma. This reduction was inhibited by the herbicide sethoxydim, and the sensitive species were much more strongly affected than the tolerant ones. The inhibition was concentration dependent. Sethoxydim affected the electron transport in isolated Poo chloroplasts. Polarographic and photometric measurements of ferricyanide reduction suggested photosystem II to be the site of action. Inhibition occurred only in the sensitive species Poa pratensis and was linearly dependent on concentration. In isolated mitochondria from sensitive Zea mays coleoptiles sethoxydim also acted as an inhibitor of electron transport. Only slight inhibition was measured with mitochondria from tubers of tolerant potato (Solanum tuberosum). It is concluded that sethoxydim generally acts as inhibitor of membrane-bound redox systems. The specific inhibition of the plasmalemma-bound redox system of sethoxydim-sensitive plants could contribute to a selective action of the herbicide.