Sonication Dispensing of Pollen from Solanum laciniatum Flowers

Abstract

1. Sonication is a seemingly effective method for foraging insects to extract pollen rapidly from poricidal anthers. However, without a dispensing mechanism to limit the pollen extraction a single forager might be able to glean all of the pollen from a flower in a single visit. 2. The vibratory release mechanism of a buzz-pollinated flower species, Solanum laciniatum, and its relationship with time was investigated. 3. The sonication vibration magnitude required to eject pollen from the anthers increased with frequency ; vibrations at frequencies below 180 Hz were particularly effective owing to the low (124 Hz) natural frequency of the stamens and the good transmission of low-frequency vibration by the anthers. The natural frequency of stamens was low compared with the sonication frequencies of bumble-bees and did not change significantly when sonicated. 4. Large amounts of pollen (72 000 grains) were released in initial sonications, but this was a small percentage (18%) of the total available pollen ; pollen release continued in metered quantities over time. 5. The stamen vibration mode created centrifugal forces, which forced pollen out of the apical pores, and the gradual dehydration of the tapetal fluid remaining in lower regions of dehiscent poricidal anthers produced a timed release mechanism. 6. The frequency increase from the flight wing-beat frequency to the sonication buzz enables bumble-bees to generate high accelerations, which are able to release pollen from the anthers, using thoracic vibrations, which are limited by the maximum possible displacement of the indirect flight muscles.