ACCUMULATION OF PROTOPORPHYRINOGEN-IX INDUCED BY ACIFLUORFEN METHYL

Confocal fluorescence microscopic images were used to investigate the accumulation site of protoporphyrin IX (PPIX) within liverwort cells ( Marchantia polymorpha L.) treated with peroxidizing herbicides as acif luorfen methyl (AFM). A high level of PPIX accumulation was observed i n the cells during 12 h to 24 h after the addition of AFM. The results obtained from confocal fluorescence microscopic images gave clear evi dence that the accumulation of PPIX occurred only in the chloroplasts, but was not observed in the cytosol or at the plasma membrane. The pr esence of PPIX in the chloroplasts strongly suggests that protoporphyr inogen (Protogen) accumulates by inhibition of protoporphyrinogen oxid ase (Protox) which is the target enzyme for peroxidizing herbicides. T he plastidic occurrence of PPIX provides evidence of either the presen ce of an additional herbicide-resistant Protox or of a non-enzymatic P rotogen-oxidation system in the Marchantia chloroplast.