Hydroxylase involved in the biosynthesis of hydroxygeraniol, a precursor of the terpenoid indole alkaloids such as vinblastine and vincristine. Also able to hydroxylate in vitro nerol and to catalyze 3'-hydroxylation of the flavanone naringenin to form eriodictyol. No activity with apigenin, kaempferol, p-coumaric acid and ferulic acid as substrates. (2E)-geraniol + O2 + reduced [NADPH--hemoprotein reductase] = (6E)-8-hydroxygeraniol + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] kcat is 3.15 min(-1) for naringenin. kcat is 7.86 min(-1) for geraniol. The N-terminal transmembrane helix is necessary and sufficient for endoplasmic reticulum targeting. Expressed in roots, stems, leaves and flower buds. Hardly detected in mature flowers and fruits. Expressed in the internal phloem-associated parenchyma. Up-regulated by methyl jasmonate treatment. The recommended numbering of geraniol gives (6E)-8-hydroxygeraniol as the product rather than 10-hydroxygeraniol as used in most publications. Belongs to the cytochrome P450 family.