Component of the volatile terpenes biosynthesis pathways (PubMed:30187155). Mediates the synthesis of a blend of monoterpenes. Converts mainly geranyl diphosphate to alpha-terpineol. Triggers also the biosynthesis of minor monoterpenes including limonene, gamma-terpinene, beta-myrcene, terpinolene and 4-terpineol (PubMed:18218975). (2E)-geranyl diphosphate + H2O = (S)-alpha-terpineol + diphosphate (2E)-geranyl diphosphate = (4S)-limonene + diphosphate (2E)-geranyl diphosphate = diphosphate + gamma-terpinene (2E)-geranyl diphosphate = beta-myrcene + diphosphate (2E)-geranyl diphosphate = diphosphate + terpinolene (2E)-geranyl diphosphate + H2O = 4-terpineol + diphosphate Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Monomer. Expressed in seedling leaf sheaths and roots. Induced by wounding in roots and leaves sheaths. 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. Tpsb subfamily. Truncated N-terminus.