Can Plants Hear Bees?

Whenever I encounter evening primrose plants in bloom, I watch them for a while. These native plants attract a variety of bees and other pollinators. At night, evening primrose is highly attractive to large moths. In the early hours of the morning, fast flying blue orchard bees visit the yellow flowers. Later in the day, butterflies, honey bees, flies, and other insects actively forage evening primrose. In today’s photo a honey bee collects nectar from evening primrose.

Honey bees can detect differences in nectar sugar concentrations of one to three percent, and foraging worker bees seek those nectar sources with the greatest concentrations of sugars. Lilach Hadany, a researcher at Tel Aviv University, questioned whether plants could hear sounds similarly to animals, https://www.nationalgeographic.com/science/2019/01/flowers-can-hear-bees-and-make-their-nectar-sweeter/. Hadany’s findings reveal that at least one plant, evening primrose, responds to the vibrations of pollinators’ wings. Within minutes of exposure to vibrations in the range of honey bee wing beats (0.2 to 0.5 kilohertz), evening primrose increased the concentration of sugars in its nectar. Hadany’s lab found that within three minutes of exposure to honey bee wing-beat-frequency vibrations the plants increased the nectar sugar concentrations from between 12 and 17 percent to 20 percent. In field observations, her researchers found pollinators around evening primrose plants nine times more frequently after the plants were visited within the past six minutes. The resulting sweeter nectar is naturally more attractive to bees and other pollinators. Since flowering plants, such as evening primrose, depend upon insect pollination for reproduction, any plant that attracts more pollinators has a reproductive advantage. Evening primrose flower petals are shaped like an open bowl. Such shapes concentrate and increase vibrations. The researchers at the Tel Aviv lab found that evening primrose flowers concentrated vibrations of the frequency range of honey bees. The ability of a flowering plant to increase its nectar’s sugar concentration would make it more attractive to pollinators and more likely to be pollinated, the first step in the plant’s reproduction.

--Richard