It represents another method "by which bees perceive the world around them and it adds another wonderful story that continues to deepen our understanding the co-evolved relationship between bees and flowers," he says.
For 30 years, some researchers have posited that electrostatic charges that can build up on bees play a role in the bees taking up and transporting pollen – a kind of small-scale static cling. They also found that the voltage associated with a flower changes as it's pollinated.
But the experiments by Dr. Robert and colleagues suggest that electricity represents a medium for conveying information between flower and bee before the bee lands.
Previous studies had indicated that bees carry a positive electrical charge with voltages that in some cases can reach as high as 200 volts. They build up the charge as they fly. With their roots in the earth, plants tend to carry a negative charge.
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.)
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.