Sesquiterpene synthase involved in the biosynthesis of volatile compounds (PubMed:21818683). No activity detected with geranyl diphosphate (GPP) and farnesyl diphosphate (FPP) as substrates (PubMed:21818683). Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Expressed in leaves, trichomes and flowers. 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. Tpsa subfamily.