Most of us grew up learning about how pollen sticks to bees as they go from flower to flower, collecting nectar and pollinating many common food crops. But that’s not how it works for your tomatoes and peppers. Instead, they use buzz pollination.
Most flowering plants (angiosperms) have male parts, called anthers, that have pollen on the outside, available to all takers. This pollen held in place by its extreme stickiness. [That stickiness is why you need to use soap and water to get pollen off your face and eyelashes, for those of you who are prone to allergies.] This pollen can be knocked loose by busy pollinators and then carried on the wind, or the pollinators find themselves covered with the sticky stuff, as they move from flower to flower, feeding on nectar and collecting pollen.
Dry, dusty pollen
Some flowers don’t have sticky pollen. Instead, they have pollen that is dry and dusty. If that pollen was exposed, it would all be gone with the first breeze, most of it never making it to another flower. Instead, these plants have evolved a specialized type of anther, known as a poricidal anther. Poricidal anthers are tubes with tiny openings at one end, but these openings are too small for bees to use. To make matters worse, these plants generally do not offer nectar, so how do they get pollinated?
Pollination by vibration
Approximately 8% of the world’s flowers are only pollinated when the correct sound wave frequency occurs nearby. When it does, the flower explodes a small dose of pollen into the air, coating whatever is at hand with genetic information and protein-rich food. This is called buzz pollination, or sonication. It gets those names because certain insects that have learned how to buzz at just the right frequency to trigger these plants to share their bounty.
Buzz pollination video courtesy of Anne Leonard, Associate Professor, Biology, University of Nevada, Reno, et al
These flowers release pollen at frequencies between 40 to 1000 Hz, depending on the species [You can use a tuning fork or an electric toothbrush to try this for yourself.] Scientists believe this arrangement evolved as a means to ensure that each visiting pollinator carries away a smaller portion of pollen (which they are less likely to drop on their way to the next flower) and that those portions are spread out over a greater number of pollinators, and over a wider time frame, for better odds of procreation. How’s that for evolution?
Not honey bees
Honey bees do not use sonication to get at pollen, but several other bees do. Sweat bees, carpenter bees, and bumblebees all use buzz pollination to get at the pollen held in poricidal anthers. They do this by disconnecting their wings from their flight muscles [I have no idea how they do this!] and vibrating those muscles at just the right frequency. In most cases, this frequency is close to middle C. The force generated during sonication can reach 30 Gs, which is almost more than a human can tolerate!
Which plants use sonication?
You may be surprised to learn that many common garden plants use sonication. Members of the legume and nightshade plant families frequently use buzz pollination to generate the fruits and vegetables we love. In addition to tomatoes and peppers, other edible plants that use buzz pollination include eggplants, potatoes, peas, blueberries, tomatillos, and kiwifruit.
How are your flowers being pollinated?
You can grow a surprising amount of food in your own yard. Ask me how!
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