Figure 7.
Effect of different oxidative stress treatments on the photosynthetic rate (A) and the chlorophyll a fluorescence (B) of plants underexpressing PMSR4. Four-week-old plants were exposed to 600 μmol photons m−2 s−1 at 8°C for 48 h (high light), 20 μm methyl viologen (paraquat), or 0.46 μL L−1 O3 for 6 h during 4 d. Photosynthesis was measured in leaves 4 and 5 from the apex of at least 12 plants/treatment. Fv/Fm was determined in the same leaves. The percentage of reduction of photosynthesis (C) and of Fv/Fm (D) in response to the treatments was calculated (see “Materials and Methods”) to show the differences in the basal levels (before treatment) of each set of plants. Each experiment was repeated three times with similar results. sd is presented as an error bar. For each treatment, means with the same letter (above the bar) were not statistically different (P ≤ 0.05). Comparisons among means are shown only for the original values (not for the calculated percent of inhibition) and are not present in case there are no statistical differences among the lines.