At a recent bridal shower, we played “What’s in your purse?” where participants gain or lose points depending on funny items they do or don’t have in their handbag. I missed out on points for lipstick and underwear, which I don’t carry, but I was thrilled to receive extra points for my toothbrush. I chose not to enlighten the party on the reason why I carry a bristle-less electric toothbrush (not for the highly respectable goal of better tooth care). I carry a toothbrush for the same reason that I also carry a tuning fork (even though I don’t tune anything but the radio). Why do I carry an electric toothbrush and a tuning fork? Because they both buzz!
Buzzing devices like toothbrushes and tuning forks are a fun way to introduce concepts of pollination to students. Tuning forks and electric toothbrushes have been used for years by farmers and scientists for artificial pollination, and I am certainly not the first to use these tools this way. For one especially neat example of the use of tuning forks by citizen scientists, see this video by the Urban Pollination Project. The Urban Pollination Project conducted a study comparing several experimental treatments of urban tomato plants, and one treatment involved tuning-fork assisted pollination. With the help of tuning-fork equipped citizen scientists, their study provided published evidence that wild urban bees support and enhance the productivity of urban agriculture.
The buzzing and whining sounds of wild bees and flies are attributable to their rapidly contracting flight muscles and/or wings, and those buzzing sounds help release pollen by shaking the pollen out of the sac-like male reproductive structures called anthers. Anthers break open or rupture to release their pollen in a process called “dehiscence”. Anthers most commonly rupture along a long slit (“longitudinal dehiscence”) and the pollen spills out, ready to be smeared on any insects that visit the flower. In a smaller subset of plants such as tomatoes and the lovely prairie flower shooting star, the pollen leaves through small pores or very tiny slits (“poricidal anthers”). Flowers with poricidal anthers frequently display “Buzz Pollination”, and these flowers rely on the vibration of a visiting insect to disperse their pollen grains. Buzz pollinated plants shower their flower visitors with pollen that is vibrated out of the small holes in the anthers (see this PBS video on “Buzz Pollination”). Flowers release more or less pollen depending on the frequency of the buzzing sounds. In contrast, plants with longitudinal dehiscence probably rely more on tactile contact than vibration frequency to powder their pollinators.
The buzzing and whining sounds of wild bees and flies are attributable to their rapidly contracting flight muscles and/or wings, and those buzzing sounds help release pollen by shaking the pollen out of the sac-like male reproductive structures called anthers. Anthers break open or rupture to release their pollen in a process called “dehiscence”. Anthers most commonly rupture along a long slit (“longitudinal dehiscence”) and the pollen spills out, ready to be smeared on any insects that visit the flower. In a smaller subset of plants such as tomatoes and the lovely prairie flower shooting star, the pollen leaves through small pores or very tiny slits (“poricidal anthers”). Flowers with poricidal anthers frequently display “Buzz Pollination”, and these flowers rely on the vibration of a visiting insect to disperse their pollen grains. Buzz pollinated plants shower their flower visitors with pollen that is vibrated out of the small holes in the anthers (see this PBS video on “Buzz Pollination”). Flowers release more or less pollen depending on the frequency of the buzzing sounds. In contrast, plants with longitudinal dehiscence probably rely more on tactile contact than vibration frequency to powder their pollinators.
Plants have not only evolved traits that attract pollinating insects, but they have also evolved floral traits that protect their flowers from insects that might take too much of their pollen or nectar and from insects that steal nectar and pollen without providing any pollinating benefit. In the case of buzz pollination, bees are unlikely to waste excessive energy buzzing for an extended time at one flower, and that means that a single bee won’t take all the pollen out of an anther in one visit. By saving some pollen for the next visiting insect, the plant obtains yet another chance to pass along its pollen genes. Buzz pollination also prevents tiny insects that can’t carry much pollen from stealing pollen because these insects are just too small to make the right buzz sounds. The story of the evolution of floral morphology may be as much about the “bad guys” (for example, thieving ants and beetles that steal flower rewards without ever moving pollen to another plant) as it is about the “good guys” (such as bumble bees that are often quite successful at distributing pollen). Most of us know at least a little bit about the good guys in pollination (the birds and bees), but less about the bad guys. As a graduate student, David Inouye’s article “The Terminology of Flower Larceny” helped to enlighten me on the diverse array of flower enemies that have probably influenced floral evolution. When I discovered buzz pollination, I knew I had found a system that is ideal for discussions with students on the delicate balance between being a good pollinator that helps with seed production versus a flower enemy that exploits a flower reward and steals excessive pollen. When I discovered that tuning forks and electric toothbrushes can mimic buzz-pollination, I was excited to take these tools to the classroom.
Demonstrating pollen leaping out of the anthers of a flower when touched with a vibrating device can sometimes catch the attention of animal-centric students. Arming students with their own tuning fork and sending them to a field to buzz their own flowers provides students with an engaging and hands-on botany learning experience. You can buy sets of 9 or more tuning forks from chiropractic and scientific suppliers or even amazon.com. Which turning fork is best? The Urban Pollination Citizen Science Project had participants use middle C (C261.6 Hz) tuning forks, but other tuning forks will also work. Teachers can even construct artificial anthers out of talcum powder, toothpicks, and tiny hand-made envelopes or packets with pin holes that allow students to simulate buzz pollination on rainy days when collecting pollen-ready flowers outside may be inconvenient or impossible.
Adding a tuning fork or battery operated toothbrush to your handbag or backpack may not help you win the bridal shower door prize, but these are great tools to have handy for a fast and easy botany demonstration and associated fun conversations about mutualisms with your students.
References
Galen, C. 1999. Flowers and enemies: predation by nectar-thieving ants in relation to variation in floral form of an alpine wildflower, Polemonium viscosum. Oikos 85(3), 426-434.
Harder, L.D. and R. M. R. Barclay. 1994. The functional significance of poricidal anthers and buzz pollination: controlled pollen removal from Dodecatheon. Functional Ecology 8: 509-517.
Inouye, D.W., 1980. The terminology of floral larceny. Ecology 61, 1251–1253.
Pearson, G. 2015. Bees are great pollinating flowers – but so are vibrators. Wired Magazine https://www.wired.com/2015/05/bees-great-pollinating-flowers-vibrators/
Potter A. and G. LeBuhn. 2015. Pollination service to urban agriculture in San Francisco, CA. Urban Ecosystems. 18: 885–893
Puterbaugh, M. 1998. The roles of ants as flower visitors: experimental analysis in three alpine plant species. Oikos 83(1), 36-46.
Stranden, A. 2016. This vibrating bumblebee unlocks a flower's hidden treasure. Prod. Josh Cassidy. Perf. Amy Standen. Deep Look. PBS, Accessed 23 June 2017. https://youtu.be/SZrTndD1H10 .
