Clodinafop changes the chlorophyll fluorescence induction curve

Clodionafop, an aceryl-coenzyme A carboxylase (ACCase) inhibitor. changed the shape of the chlorophyll fluorescence induction curve (Kautsky curve) in barley and oat in greenhouse experiments. Biomass ED50. based on log-logistic dose-response curves, for barley was considerably higher than that for oat in all experiments. Biomass ED50 and relative potency (ED50 [barley]/ED50 [oat]) were consistent among experiments when sprayed at the same phenological stage of plant development. Especially at high doses, clodinafop changed The shape of the Kaursky curve more , for oat than for barley. From The numerous parameters that can be derived from the OJIP steps of the Kautsky curve. we found that (1) F-vj, the relative changes at the J step [F-vj (F-m - F-j)/F-m] (2) area between Kautsky curve and maximum fluorescence F., maximum quantum efficiency of Photosystem II [F-v] F-m = (F-m - F-0)/F-m], were closely linked to the biomass dose-response relationships for both species. The linkage between biomass and the fluorescence parameters may be used to shorten the screening period for ACCase inhibitors.