Illuminated chloroplasts isolated from SO2-fumigated spinach leaves accumulated more H2O2 than those from non-fumigated ones. This H2O2 formation was dependent on light and was inhibited by DCMU. It also was depressed by cytochrome c and superoxide dismutase (EC 1.15.1.1). The addition of sulfite to ruptured chloroplasts isolated from non-fumigated leaves caused an H2O2 accumulation that accompanied O2 uptake. Spinach leaves lost their catalase (EC 1.11.1.6), ascorbate peroxidase and glutathione reductase (EC 1.6.4.2) activities at the beginning of SO2 fumigation, when H2O2 was accumulated. These results suggest that the accumulation of H2O2 in SO2-fumigated spinach leaves is caused by the increase in O2−production, the precursor for H2O2, with a sulfite-mediated chain reaction at the reducing site of photosystem I, and by inactivation of the H2O2 scavenging system.
No takes yet. Share an insight, caveat, or question.
Tanaka et al. (1982) studied this question.