Involved in defense response and tolerance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). Plays an important role in hydrogen peroxide removal during infection by Xoo. Involved in response to abiotic stress. Plays a role in hydrogen peroxide removal durings salt stress. H2O2 + L-ascorbate = 2 H2O + L-dehydroascorbate Binds 1 heme b (iron(II)-protoporphyrin IX) group. Interacts with SWEET11/OS8N3. Expressed in roots, leaves, stems and flowers (PubMed:16397796). Expressed in leaves, shoots and panicles. Expressed at low levels in roots (PubMed:27185545). Induced by salt stress, abscisic acid (ABA), sodium nitrate and hydrogen peroxide in roots (PubMed:17916638). Induced by infection with the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo) (PubMed:27185545). Down-regulated by salt stress in leaves (PubMed:16397796). Down-regulated by hydrogen peroxide in leaves (PubMed:25546583). Binds one cation per subunit; probably K(+), but might also be Ca(2+) (By similarity). Plants over-expressing APX8 exhibit increased tolerance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). Plants silencing APX8 show increased sensitivity to Xoo (PubMed:27185545). Belongs to the peroxidase family. Ascorbate peroxidase subfamily.