Leaves are a Source of Biogenic Persistent Free Radicals

Nonsenescent andsenescent leaves of selected coniferous and broadleafplants contained substantial levels of naturally occurring persistentfree radicals (PFRs). These biogenic PFRs (BPFRs) were stable andpersistent despite multiple wetting and drying cycles, implying thatBPFRs can leach and sorb on soil particles. Results suggest that endogenouschemicals in plants and their transformation byproducts can stabilizeunpaired electrons in leaves under ambient conditions. Thus, the vastamount and perpetual supply of leaf litter is an unaccounted naturalsource of BPFRs. If toxic, inhaling and accidentally ingesting finesoil dust and powder from degraded leaf litter may increase our environmentaland health burdens to PFRs. We expect that this finding will generatemore studies on natural sources of PFRs, establish their properties,and distinguish them from those formed from combustion and thermalprocesses.