A sensitive flower: mechanical stimulation induces rapid flower closure in Drosera spp. (Droseraceae)

Some plants rapidly close their leaves in response to mechanical stimulation, but no case is known in which mechanical stimulation causes rapid petal closure. In this study, we found that Drosera tokaiensis closes petals within 2–10 min after experimental stimulation of the calyx, closed flowers or scapes with a pair of tweezers. Although petal closure was induced more rapidly by touching a position closer to a flower, it was not induced by stimulating stamens and pistils. The habit of petal closure varies among species of Drosera: after experimental stimulations of the calyx or scapes, D. tokaiensis and D. spatulata often closed petals but D. rotundifolia and D. toyoakensis did not close them. The petal closure may function as defense against a specialist florivore.