An anonymous reader writes:
The latest experiments in this niche but increasingly vocal field come from Lilach Hadany and Yossi Yovel at Tel Aviv University. In one set, they showed that some plants can hear the sounds of animal pollinators and react by rapidly sweetening their nectar. In a second set, they found that other plants make high-pitched noises that lie beyond the scope of human hearing but can nonetheless be detected some distance away. After the team released early copies of two papers describing their work, not yet published in a scientific journal, I ran them past several independent researchers. Some of these researchers have argued that plants are surprisingly communicative; others have doubted the idea. Their views on the new studies, however, didn’t fall along obvious partisan lines. Almost unanimously, they loved the paper asserting that plants can hear and were skeptical about the one reporting that plants make noise. Those opposite responses to work done by the same team underscore how controversial this line of research still is, and how hard it is to study the sensory worlds of organisms that are so different from us.
First, two team members, Marine Veits and Itzhak Khait, checked whether beach evening primroses could hear. In both lab experiments and outdoor trials, they found that the plants would react to recordings of a bee’s wingbeats by increasing the concentration of sugar in their nectar by about 20 percent. They did so in response only to the wingbeats and low frequency, pollinator-like sounds, not to those of higher pitch. And they reacted very quickly, sweetening their nectar in less than three minutes. That’s probably fast enough to affect a visiting bee, but even if that insect flies away too quickly, the plant is ready to better entice the next visitor. After all, the presence of one pollinator almost always means that there are more around. But if plants can hear, what are their ears? The team’s answer is surprising, yet tidy: It’s the flowers themselves. They used lasers to show that the primrose’s petals vibrate when hit by the sounds of a bee’s wingbeats. If they covered the blooms with glass jars, those vibrations never happened, and the nectar never sweetened. The flower, then, could act like the fleshy folds of our outer ears, channeling sound further into the plant. (Where? No one knows yet!)
