[Effects of ozone stress upon winter wheat photosynthesis, lipid peroxidation and antioxidant systems].

Stress effects of surface increased ozone concentration on winter wheat photosynthesis, lipid peroxidation and antioxidant systems in varied growth stages (jointing stage, booting stage, blooming stage and grain filling stage) were studied, the winter wheat was exposed to open top chambers (OTCs) in an open field conditions to three levels ozone concentrations (CK, 100 nmol x mol(-1), 150 nmol x mol(-1)). The results revealed that within 150 nmol x mol(-1) ozone concentration, as the ozone concentration and time increased,total chlorophyll content,chlorophyll a and b contents of winter wheat leaves were general declined,but compared to CK, the total chlorophyll and chlorophyll a content of T1 treatment groups were a little higher at booting and blooming stage; the conductance of stomatal was affected, the activation of unit leaf area decreased, intercellular CO2 concentration and stomatal limitation value showed a fluctuation change tendency. At the same time, a self-protective mechanism of winter wheat were launched. Concrete expression of SOD activity first increased rapidly and then gradually decreased, the activity of POD showed a decrease firstly and then rapidly increased. From the jointing stage to the blooming stage and from the grain filling stage one to grain filling stage two, the activity of CAT rapidly increased first and then comparatively decreased, but the content of MDA kept steadily rising. The carotenoid content increased first and then decreased, heat dissipation of unit leaf area increased. These results indicate that antioxidant enzymes can not completely eliminate excessive reactive oxygen species in vivo of winter wheat, then lead to accumulation of reactive oxygen species, further exacerbate the lipid peroxidation, that result in the increase of membrane permeability, degradation of chlorophyll, reduction of net photosynthetic rate, imposing on the winter wheat leaves senescence process.