Monoterpene synthase converting geranyl diphosphate into alpha-terpineol. In vitro, can also have an sesquiterpene synthase activity, converting farnesyl diphosphate into (E)-alpha-bisabolene (33.1%), alpha-bisabolene (18.7%), beta-sesquiphellandrene (15.8%), beta-bergamotene (12.6%), (Z)-alpha-farnesene (10.4%), and (Z)-alpha-bisabolene (9.4%). (2E)-geranyl diphosphate + H2O = (S)-alpha-terpineol + diphosphate (2E)-geranyl diphosphate + H2O = (R)-alpha-terpineol + diphosphate Binds 3 Mg(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. The transit peptide can target GFP to both chloroplasts and mitochondria when transiently expressed in a heterologous system. Expressed in young developing leaves. Barely detected in tepals, carpels and stamens. 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.