PEROXIDATION OF ISOLATED MICROSOMAL-MEMBRANES FROM NONGREEN PLANT-TISSUE

Lipid peroxidation has been linked to membrane-associated disorders in plant tissue, but proposed mechanisms differ on whether phospholipid hydrolysis in membranes accelerates or inhibits peroxidation. Isolated microsomal fractions from cowpea seeds and cauliflower florets were challenged by hydrolytic (PLA(2)) and oxidative (FeCl2-ADP or FeCl3-ascorbate) conditions simultaneously or in sequence to determine the effect of hydrolysis on peroxidation in plant membranes. Cauliflower microsomes were more susceptible to peroxidative challenge than cowpea microsomes by an order of magnitude. Lipid peroxidation of cowpea microsomes was stimulated by phospholipid hydrolysis even prior to challenge by prooxidants. A slight, but consistent inhibition of lipid peroxidation was observed in cauliflower microsomes preincubated with PLA(2). The results suggest that other factors in plant membranes are more important in the progress of lipid peroxidation than the presence or absence of free fatty acids.