OXIDATIVE DEFENSE SYSTEMS IN LEAVES OF 3 EDIBLE HERB SPECIES IN RELATION TO THEIR SENESCENCE RATES

Correlation studies between leaf senescence rates of three edible herb species, watercress (Rorippa nasturtium-aquaticum), parsley (Petroselium crispum), and sage (Salvia officinalis L.), and their oxidative defense systems were conducted with detached leaves under simulated shelf-life storage conditions. The relative order of leaf senescence rate, based on their rate of chlorophyll (Chl) degradation and malondialdehyde accumulation, was watercress > parsley > sage. However, all three herb species showed high proteolysis rates from the first day of incubation. Of five oxidative defense systems examined in the three herb species, only the system of total reducing capacity correlated well with their relative order of Chl degradation and could therefore predict their storage potential. The results indicate that each herb species has developed specific oxidative defense systems, which may also prevent rapid Chl loss but do not affect proteolysis. It seems, therefore, that among the various components of the senescence syndrome, Chl breakdown is closely linked to lipid oxidation, while proteolysis seems to proceed independently of these two senescence-associated processes.