Response of Spinach Leaves (Spinacia oleraceaL.) to Ozone Measured by Gas Exchange, Chlorophyll aFluorescence, Antioxidant Systems, and Lipid Peroxidation

Spinach (Spinacia oleraceaL. cv. Clermont) leaves grown in open-top chambers and exposed to three different concentrations of ozone were measured for gas exchange, chlorophyll afluorescence, antioxidant systems, and lipid peroxidation at the end of growing season. High O3concentration reduced Fv/Fm, indicating that the efficiency in the energy conversion of photosystem 2 (PS2) was altered. The rate of non-cyclic electron transport rate and the capacity to reduce the quinone pool were also affected. The development of non-photochemical quenching was not high enough to decrease the photon excess in the PS2. The limitation of photosynthetic activity was probably correlated with stomata closure and with an increase in intercellular CO2concentration. Under oxidative stress, superoxide dismutase (SOD) activity was stimulated in parallel with lipid peroxidation. We did not find any differences in the ascorbate (AsA) pool and ascorbate peroxidase (APX) or glutathione reductase (GR) activities between air qualities. Small, but similar responses were observed in spinach leaves exposed to ambient ozone concentration.