Figure 4.

Production of singlet oxygen in wild-type, ΔpsbA2, flv4-2/OE, and Δflv4 strains in the presence of 5 mm His upon illumination of the cells at 2,300 μmol photon m⁻² s⁻¹. The cultures were adjusted to a chlorophyll concentration of 5 µg mL⁻¹. To demonstrate that the O₂ uptake signal indeed arises from ¹O₂, 10 mm sodium azide, which is specific quencher of ¹O₂, was also applied. Because sodium azide inhibits O₂ evolution, its ¹O₂ quenching effect was tested in the presence of DCMU in which the artifact that would arise from the decreased of O₂ evolution rate could be avoided. The results are a mean ± sd of three independent experiments. NaN₃, sodium azide; WT, wild type.