Involved in the biosynthesis of phenolic sesquiterpenes natural products (Ref.2). Sesquiterpene synthase converting (2E,6E)-farnesyl diphosphate (FPP) to alloaromadendrene and bicyclo-germacrene. The product formation is dependent on the metal ions present and in presence of manganese, bicyclo-germacrene is greatly favored while both alloaromadendrene and bicyclo-germacrene are produced in equivalent amounts in the presence of magnesium. Can also convert geranyl diphosphate (GPP) to terpinolene, limonene and geraniol, and this conversion is not affected by the presence of magnesium or manganese. (2E,6E)-farnesyl diphosphate = bicyclogermacrene + diphosphate (2E)-geranyl diphosphate = diphosphate + terpinolene (2E)-geranyl diphosphate = (4R)-limonene + diphosphate (2E)-geranyl diphosphate + H2O = (2E)-geraniol + diphosphate (2E,6E)-farnesyl diphosphate = allo-aromadendrene + diphosphate Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Homodimer. Expressed in peltate glandular trichomes (PubMed:20419468). Present at low levels in flowers, leaves and stems (Ref.3). The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the terpene synthase family.