Protoporphyrinogen IX-oxidizing activities involved in the mode of action of a new compound N-[4-chloro-2-fluoro-5-{3-(2-fluorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl-methoxy}-phenyl]-3,4,5,6-tetrahydrophthalimide

Abstract

N-[4-Chloro-2-fluoro-5-{3-(2-fluorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl-methoxy}-phenyl]-3,4,5,6-tetrahydrophthalimide (EK-5385) is an experimental substituted bicyclic herbicide. Soil-applied EK-5385 showed good rice selectivity and potent herbicidal activity on barnyardgrass ( Echinochloa crus-galli var. oryzicola) at rates of 3.9–250 g a.i./ha. Barnyardgrass was exhibited normal growth under dark condition, however, the growth of shoot and root was severely inhibited under light condition (14/10 h of light/dark, 50 μmol/m 2/s of photosynthetically active radiation) when treated with EK-5385, oxadiazon, and oxadiargyl. IC 50 of EK-5385 and oxadiargyl to chlorophyll loss in cucumber cotyledons was approximately 0.3 and 0.7 μM, respectively. IC 50 of EK-5385 and oxadiargyl to carotenoids loss in cucumber cotyledons was about 0.26 and 0.1 μM, respectively. IC 50 concentration of EK-5385 and oxadiargyl on Protox activity was approximately 5.5 and 8 nM, respectively. Cellular leakage occurred without lag period from cucumber leaf squares treated with 1 μM of EK-5385 and oxadiargyl under light exposure.