Structural dynamics of real and modelled Solanum stamens: implications for pollen ejection by buzzing bees |
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Authors: | Mark Jankauski Riggs Ferguson Avery Russell Stephen Buchmann |
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Affiliation: | 1. Department of Mechanical and Industrial Engineering, Montana State University, Bozeman, MT, USA ; 2. Department of Biology, Missouri State University, Springfield, MO, USA ; 3. Department of Ecology and Evolutionary Biology,, University of Arizona, Tucson, AZ, USA ; 4. Department of Entomology, University of Arizona, Tucson, AZ, USA |
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Abstract: | An estimated 10% of flowering plant species conceal their pollen within tube-like anthers that dehisce through small apical pores (poricidal anthers). Bees extract pollen from poricidal anthers through a complex motor routine called floral buzzing, whereby the bee applies vibratory forces to the flower stamen by rapidly contracting its flight muscles. The resulting deformation depends on the stamen''s natural frequencies and vibration mode shapes, yet for most poricidal species, these properties have not been sufficiently characterized. We performed experimental modal analysis on Solanum elaeagnifolium stamens to quantify their natural frequencies and vibration modes. Based on morphometric and dynamic measurements, we developed a finite-element model of the stamen to identify how variable material properties, geometry and bee weight could affect its dynamics. In general, stamen natural frequencies fell outside the reported floral buzzing range, and variations in stamen geometry and material properties were unlikely to bring natural frequencies within this range. However, inclusion of bee mass reduced natural frequencies to within the floral buzzing frequency range and gave rise to an axial-bending vibration mode. We hypothesize that floral buzzing bees exploit the large vibration amplification factor of this mode to increase anther deformation, which may facilitate pollen ejection. |
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Keywords: | buzz pollination floral sonication floral buzzing poricidal anthers structural dynamics computational modelling |
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