Effects of ozone on membrane lipid peroxidation and antioxidant system of rice leaves

Rice plants were used to investigate effects of ozone on membrane lipid peroxidation and antioxidant system of rice leaves in varied growth stage. The plants were exposed in open top chambers (OTCs) in field conditions to four levels of O3 concentration (charcoal filtered air, 50 nl·L-1, 100 nl·L-1, 200 nl·L-1) from 1999-07-04 to 1999-10-01. With O3 concentration increasing, chlorophyll content and chlorophyll a/b in rice leaves were significantly declined; membrane permeability and the level of lipid peroxidation (MDA) content were significantly increased; the activity of CAT, SOD increased first and decreased afterward; the activity of POD gradually increased. Chlorophyll content was negatively correlated with MDA content and membrane permeability was positively correlated with MDA content. Those observations indicated the O3 stress induce in vivo oxidative injury and affect the activities of antioxidant enzymes. The effects resulted in imbalance of activated oxygen produce and scavenge, accelerated process of lipid peroxidation, imposed on the rice leaves detrimentally.