Plays a key role in hydrogen peroxide removal. Constitutes a central component of the reactive oxygen gene network. H2O2 + L-ascorbate = 2 H2O + L-dehydroascorbate Binds 1 heme b (iron(II)-protoporphyrin IX) group per subunit. A number of isoforms are produced. According to EST sequences. Predominantly expressed in flowers. By ethylene, ozone, sulfur dioxide, Fe exposure, oxidative and heat-shock stresses, and by excess light treatment. Induced by cadmium (PubMed:16502469). Binds one cation per subunit; probably K(+), but might also be Ca(2+). Belongs to the peroxidase family. Ascorbate peroxidase subfamily.