Protein Kinase C-like activity was established in Marchantia polymorpha. Different concentrations were detected in young and old tissue extracts from untreated and spermine-treated thalli after agarose gel electrophoresis in the presence of a PKC-specific fluorescent tags. Cytosolic putative PKC concentrations (nmol/g tissue) in untreated young thalli were higher than concentrations in old tissue. Old spermine-treated tissue possessed higher cytosolic putative PKC concentrations than young untreated thalli. Both young and old spermine-treated tissue extracts possessed higher total protein levels than young and old untreated tissue extracts. The data suggest that spermine-treatment evoked a qualitative and quantitative decrease in senescence.