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 c hallenged by hydrolytic (PLA(2)) and oxidative (FeCl2-ADP or FeCl3-asc orbate) conditions simultaneously or in sequence to determine the effe ct of hydrolysis on peroxidation in plant membranes. Cauliflower micro somes were more susceptible to peroxidative challenge than cowpea micr osomes by an order of magnitude. Lipid peroxidation of cowpea microsom es was stimulated by phospholipid hydrolysis even prior to challenge b y prooxidants. A slight, but consistent inhibition of lipid peroxidati on was observed in cauliflower microsomes preincubated with PLA(2). Th e results suggest that other factors in plant membranes are more impor tant in the progress of lipid peroxidation than the presence or absenc e of free fatty acids.