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Publication - Professor Daniel Robert

    Mechanism for rapid passive-dynamic prey capture in a pitcher plant


    Bauer, U, Paulin, M, Robert, D & Sutton, GP, 2015, ‘Mechanism for rapid passive-dynamic prey capture in a pitcher plant’. Proceedings of the National Academy of Sciences of the United States of America, vol 112., pp. 11384-11389


    Plants use rapid movements to disperse seed, spores, or pollen and catch
    animal prey. Most rapid-release mechanisms only work
    once and, if repeatable, regaining the
    prerelease state is a slow and costly process. We present an
    encompassing mechanism
    for a rapid, repeatable, passive-dynamic
    motion used by a carnivorous pitcher plant to catch prey. Nepenthes gracilis
    uses the impact of rain drops to catapult insects from the underside of
    the canopy-like pitcher lid into the fluid-filled
    trap below. High-speed video and laser
    vibrometry revealed that the lid acts as a torsional spring system,
    driven by rain
    drops. During the initial downstroke, the
    tip of the lid reached peak velocities similar to fast animal motions
    and an order
    of magnitude faster than the snap traps of
    Venus flytraps and catapulting tentacles of the sundew Drosera glanduligera. In contrast to these active movements, the N. gracilis
    lid oscillation requires neither mechanical preloading nor metabolic
    energy, and its repeatability is only limited by the
    intensity and duration of rainfall. The
    underside of the lid is coated with friction-reducing wax crystals,
    making insects
    more vulnerable to perturbations. We show
    that the trapping success of N. gracilis relies on the combination of material stiffness adapted for momentum transfer and the antiadhesive properties of the wax
    crystal surface. The impact-driven oscillation of the N. gracilis lid represents a new kind of rapid plant movement with adaptive function. Our findings establish the existence of a continuum
    between active and passive trapping mechanisms in carnivorous plants.

    Full details in the University publications repository