Buzz pollination

Buzz pollination or sonication is a technique used by some bees, such as the Bombus morio and many other bumble bees, to release pollen which is more or less firmly held by the anthers. The anther of buzz-pollinated species of plants is typically tubular, with an opening at only one end, and the pollen inside is smooth-grained and firmly attached. With self-fertile plants such as tomatoes, wind may be sufficient to shake loose the pollen through pores in the anther and accomplish pollination. Visits by bees may also shake loose some pollen, but more efficient pollination of those plants is accomplished by a few insect species who specialize in sonication or buzz pollination.

In order to release the pollen, bumblebees and some species of solitary bees are able to grab onto the flower and move their flight muscles rapidly, causing the flower and anthers to vibrate, dislodging pollen. This resonant vibration is called buzz pollination. The honeybee cannot perform buzz pollination. About 8% of the flowers of the world are primarily pollinated using buzz pollination.

Plants that rely on buzz pollination have a unique anther shape compared to other flora. The anthers of a flower are where sperm is produced and develops into pollen. This pollen leaves the plant to pollinate a stigma, or female reproductive structure, of another flower, either by wind or animal pollinators. Eventually a pollen tube grows down the stigma to fertilize the ovule. In buzz pollinated plants, this process can only happen if pollinators visit the flowers to extract pollen. However, only a select few insect species are able to pollinate these plants.The flower morphology of buzz pollinated plants is different from other flora that do not use this type of pollination. The anthers are completely sealed except for a small pore at the top or have very small slits that open along the sides. The pores and slits are small enough that insects cannot easily enter the anther, but large enough pollen can exit. Because of this shape, they are often referred to as poricidal anthers. These poricidal anthers are only able to release pollen when vibrated at a specific frequency. The stigmas of these flowers are often located below the anthers. This is could be an evolutionary strategy to prevent self-fertilization, also known as selfing, by creating distance between the stigma.

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