Involved in the biosynthesis of oxygen-containing labdane-type diterpenes that may be implicated in direct and indirect defense mechanisms. No activity with geranyl diphosphate or farnesyl diphosphate as substrate. (2E,6E,10E)-geranylgeranyl diphosphate + H2O = 8-hydroxycopalyl diphosphate Secondary metabolite biosynthesis; terpenoid biosynthesis. Expressed in stems, leaves and trichomes. Not detected in roots and seeds. Higher expression in young leaves than in fully expanded leaves. Up-regulated by wounding. The Asp-Xaa-Asp-Asp (DXDD) motif is important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the terpene synthase family.