thumbnail|A female [[Augochloropsis using buzz pollination]]

thumb|Bumble bee buzz-pollinates [[Solanum dulcamara]]

Buzz pollination or sonication is a technique used by some bees, such as solitary bees and bumblebees, to release pollen which is more or less firmly held by the anthers. The anthers of buzz-pollinated plant species are 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, solitary bees are able to grab onto the flower and move their flight muscles rapidly, causing the flower and anthers to vibrate, dislodging pollen. Pollination involving vibrations is called buzz pollination. Honeybees cannot perform buzz pollination. About 9% of the flowers of the world are primarily pollinated using buzz pollination.

thumb|[[Senna (plant)|Sennas poricidal anthers.]]

Flower morphology

Plants that rely on buzz pollination have a unique anther shape compared to other flora. In buzz pollinated plants, this process can only happen if pollinators visit the flowers to extract pollen. Only a few insect species are able to pollinate these plants. The flower morphology of buzz pollinated plants is different from that of 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.

  • Bombus terrestris
  • Euglossa sp.
  • Melipona sp. Also, some extant flora such as members of the family Myrtaceae show a spectrum of anther shapes including poricidal anthers and are thought to resemble some morphological aspects of ancestral buzz pollinated flowers.

Although pollination results from the bees visiting these flowers, this is not the primary reason they visit plants with poricidal anthers. Pollen contains a substantial amount of protein compared to nectar, the sugary liquid the majority of plants produce as a reward for their animal pollinators.

One of the most common plants that are assisted by buzz pollination is the tomato (Solanum lycopersicum). In greenhouses worldwide, up to 50 bumblebee colonies are used per hectare during growing season, bringing in values of approximately €13 million a year for a 40,000 hectare globally. Due to competition between producers and an increase in success rate of rearing, the total costs for the bumblebee colonies have diminished severely. This common practice has led to producers branching out and selling not only bumblebees but other insects who may have mutualistic relationships with plants. The total profit of this industry has been recorded to produce over €111 million a year, with €61 million coming in from bumblebees alone.

Environmental impacts

Some conservation organisations expressed concerns about the potential environmental impacts of introducing bumblebees around the world to aid in pollination. In Australia, as bumblebees are not native, and Australia has a number of widely publicised environmental disasters caused by escaped introduced species ("feral species"), research is under way to adapt the use of the Australian native Amegilla cingulata (blue banded bees) for the same task.

Alternative means of pollination

Greenhouse grown tomatoes are unproductive without aid in pollination. Traditionally, pollination has been done by shaking using electric vibrators (one brand name was "Electric Bee"), however, it has been found to be less expensive in human labor and plant breakage to use bumblebees within the greenhouses. Home growers and amateurs can be seen on YouTube using electric toothbrushes to pollinate their flowers.

References

  • Buzz Pollination, Anne Leonard Lab.
  • Carl Zimmer, Unraveling the Pollinating Secrets of a Bee’s Buzz, New York Times, July 11, 2013.
  • Sue Rosenthal, Buzz Pollination, Bay Nature, June 11, 2008.
  • Buzz pollination and bee learning, Vallejo-Marin Lab