title: Influence of the acetolactate synthase inhibitor metsulfuron-methyl on the operation, regulation and organisation of photosynthesis in Solanum nigrum.
abstract: The influence of the acetolactate synthase inhibitor metsulfuron-methyl on the operation of the photosynthetic apparatus was examined on 4-weeks-old climate chamber-grown Solanum nigrum plant. To have an indication on the relative performance of the photosynthetic apparatus of ALS-treated plants, the level of carbon dioxide (CO(2)) fixation, the relative quantum efficiency of photosystem I (Phi(PSI)) or photosystem II (Phi(PSII)) electron transport and leaf chlorophyll content were assessed for both control and treated plants at 2, 4 and 7 days after application of the herbicide. Results indicated a progressive inhibition of the level of CO(2) fixation, the relative quantum efficiency of photosystem I (Phi(PSI)) and II (Phi(PSII)) electron transport and the leaf chlorophyll content already 2 days after application of the herbicide. The linear relationship between the photosystem I and II was unaltered by herbicidal treatment and was sustained under conditions where large changes in pigment composition of the leaves occurred. It appears that the stress-induced loss of leaf chlorophyll is not a catastrophic process but rather is the consequence of a well-organised breakdown of components. Under photorespiratory and non-photorespiratory conditions, the relationship between the index of electron transport flow through photosystem I and II and the rate of CO(2) fixation is altered so that electron transport becomes less efficient at driving CO(2) fixation.
authors.affiliation: Crop and Weed Ecology Group, Department of Plant Science, Wageningen University and Research Centre, P.O. Box 430, 6700 AA Wageningen, The Netherlands. Ingrid.Haage@wur.nl
authors.forename: Ingrid
authors.initials: I
authors.lastname: Riethmuller-Haage
authors.forename: Lammert
authors.initials: L
authors.lastname: Bastiaans
authors.forename: Jeremy
authors.initials: J
authors.lastname: Harbinson
authors.forename: Corné
authors.initials: C
authors.lastname: Kempenaar
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Kropff
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors*; D001190:Arylsulfonates / Q000494:pharmacology*; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D006540:Herbicides / Q000494:pharmacology; D010788:Photosynthesis / Q000187:drug effects*; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D032324:Solanum nigrum / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D001190:Arylsulfonates; D006540:Herbicides; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C050296:metsulfuron methyl; D000095:Acetolactate Synthase