SUSCEPTIBILITY OF MICROSOMAL-MEMBRANES ISOLATED FROM BELL PEPPER FRUIT TO PEROXIDATIVE CHALLENGE AT DIFFERENT TEMPERATURES

Stress response in plant tissue has been associated with lipid peroxid ation via a free-radical mechanism, but the susceptibility of membrane lipids in microsomal fractions to oxidative stress has not been clear ly delineated. Microsomal membranes isolated from fruit of bell pepper (Capsicum annum L.) were subjected to five challenge conditions [Fe2-ascorbate, xanthine oxidase, LOX with and without PLA(2), and PLA(2)] at three temperatures (6, 21, and 37 degrees C) and analyzed at 30-mi n intervals during a 2-hour incubation to determine the effect of temp erature and treatment on peroxidation as measured by TBA-RS and conjug ated dienes. Higher temperatures resulted in increased peroxidation in the four enzymic systems. The source of free-radical initiation was a greater factor in response of the microsomes to peroxidative stress t han the effect of temperature. The results suggest that different pero xidative mechanisms occur during in vitro challenge of membranes depen ding on the initiating system selected, thus making comparative studie s on susceptibility to peroxidative attack difficult to interpret.