Enzymatic activity of protoporphyrinogen-IX oxidase from various plant species: Its sensitivity to peroxidizing herbicides

Enzyme activity of protoporphyrinogen-IX oxidase (Protox) prepared from 34 kinds of plant sources, containing 18 monocotyledons and 16 dicotyledons wa s evaluated. Protox(es) originated in monocotyledonous plants such as Zea m ays cv. Anjou and DK212, Lolium perenne and Poa annua exhibited high enzyme activity, and Protox(es) in dicotyledonous plants such as Agrostemma githa go and Arabidopsis thaliana showed a little higher enzyme activity than tha t of the above monocotyledonous plants. Highly active Protox(es) obtained f rom Zea mays cv. Anjou, Lolium perenne Agrostemma githago and Arabidopsis t haliana were selected for the Protox inhibitory assay of peroxidizing herbi cides. Echinochloa utilis was also selected for control. Protox inhibition by six peroxidizing herbicides such as oxyfluorfen, chlorophthalim, BW-91, pyraflufen-ethyl, DLH-1777 and LS-82556 was investigated using highly activ e Protox from the above monocotyledons and dicotyledons. As a result, six p eroxidizing herbicides exhibited high inhibitory activity to Protox. Pyrafl ufen-ethyl showed the highest inhibition. The order of Protox inhibitory ac tivity was pyraflufen-ethyl > oxyfluorfen> BW-91 > chlorophthalim> DLH-1777 >LS-82556, in experiment using four Protox(es) such as Zea mays cv. Anjou, Echinochloa utilis, Agrostemma githago and Arabidopsis thaliana except Loli um perenne. Oxyfluorfen exhibited the highest inhibitory activity to Protox of Lolium perenne. On the other hand, DLH-1777 showed a little less activi ty to Protox of Zea mays than that of other four weeds. DLH-1777 may become a model compound to find out new selective herbicides. Protox from four we eds will be used for pe herbicides assay, since the Protox showed high sens itivity to structually different peroxidizers. peroxidizing.