Bees use the 'force' to choose the best flowers, study finds
Bees can alter the electrical charge of the flowers they touch. A new study finds that bees use these electrical cues to help them choose flowers with the most nectar and pollen.
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The team's experiments confirmed those earlier results, as well as the effect an arriving bee can have on a plant's electrical traits. Essentially, as the bee approached and landed on the flower, the bee transferred some of its charge to the plant stem, driving the plant's charge positive for up to nearly two minutes. (By contrast, the changes a bee can trigger to a flower's scent, shape, color, or even humidity, last from several minutes to hours, the researchers note.)Skip to next paragraph
In Pictures Busy bees
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Wanting to push further, the researchers conducted a series of tests.
First, they wanted to see to see if bees actually use these electrical changes to help them learn more quickly which flowers to target. To do this, they turned bees loose on identically colored steel disks used as stand-ins for flowers. Some disks carried a liquid bees find distasteful. The others had a nectar-like liquid.
When the scientists added a 30-volt charge to the disk with the nectar, the bees accurately picked out the nectar-bearing flowers 81 percent of the time during the final 10 visits of the 50-visit training session. When there was no electrical difference, the bees did little better than a coin toss in picking out the flowers offering the nectar-like reward.
**Next, the team wanted to see if bees responded to patterns in voltage distribution across a flower. So some faux flowers were given a bull's-eye pattern in which the outer ring received the highest positive voltage, while the center was held at a negative voltage. A single voltage was applied to the other flowers. The bull's-eyes also held the nectar-like reward, while the uniformly-charged flowers got the bitter vetch.
Here, 70 percent of the bees went to the bull's-eye flowers by the end of the training session. When the bull's-eyes were removed and same voltage was applied equally across both the sweet and the sour flowers, a smaller group of bees culled from the larger group couldn't tell the difference at the end of a 50-visit training session until they took a sip. They moved more randomly among the flowers.
Finally, the team conducted a test to see if color and electrical cues worked in concert to aim bees at the nectar-laden flowers. Using color alone, it took 35 visits to the flowers for the bees to hit the 80-percent success mark by the end of the training visits. For bees using color and electrical cues, it took only 24 visits.
Taken together, the team says its results show that electrical fields play a "thus-far under-appreciated role in plant-insect interactions."
Simon Fraser University's Dr. Winston suggests a broader lesson.
"We really underestimate the number and diversity of sensory modes" that humans use to communicate with one another, he says. "One of the great advantages of doing this kind of research with bees is that you can do the kind of experiments and you can measure the kinds of subtle modalities in a fairly simple system compared to people."
"It reminds us that we likely have things going on like this as well that we use and we process, but that we really don't understand and can't really define," he says
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