Tag: pollen

more on bees and pollination

Bee on flower

NPR helps us continue our bee coverage. Today they summarize these two studies on wild bees and pollination. The first study examines the importance of wild bees in pollinating crops. Wild bees are thought to be better pollinators than honey bees and to help boost crop harvests:

Farmers who grow these crops often rely on honeybees to do the job. But scientists are now reporting that honeybees, while convenient, are not necessarily the best pollinators.

A huge collaboration of bee researchers, from more than a dozen countries, looked at how pollination happens in dozens of different crops, including strawberries, coffee, buckwheat, cherries and watermelons. As they report in the journal Science, even when beekeepers installed plenty of hives in a field, yields usually got a boost when wild, native insects, such as bumblebees or carpenter bees, also showed up.

“The surprising message in all of this is that honeybees cannot carry the load. Honeybees need help from their cousins and relatives, the other wild bees,” says Marla Spivak, a professor of entomology at the University of Minnesota. “So let’s do something to promote it, so that we can keep honeybees healthy and our wild bee populations healthy.”

The second study brings the not so good news that wild bee species might be in decline. From NPR again:

Robertson taught biology and Greek at Blackburn College in Carlinville, Ill., and he was fascinated by the close connection between insects and flowers. He spent years in the forests around Carlinville, carefully noting which insects visited which wild flowers at what time of year.

Burkle and Tiffany Knight, a colleague at Washington University in St. Louis, went back to Carlinville to see how much of the ecosystem that Robertson observed still exists today.

Much of the forested area around the town has been converted into fields of corn and soybeans — or suburbs. In the fragments of forest that remain, Burkle and Knight found all of the flowering plants that Robertson recorded in his notes a century ago. Of the 109 species of bees that Robertson saw, though, just over half seemed to have disappeared from that area.

If you have time you can listen to the NPR story here. Or check out the research papers here and here.

bees, flowers and electric fields

Bee on flower

We all know that flowers attract bees and other pollinators to help them reproduce. And in this week’s Science magazine, we get more insight into how it’s done. As it turns out,  bees use the electric fields around flowers to sense whether it might contain pollen. The bees can also tell by the electric field whether a flower has just recently been visited by another bee.

Plants tend to conduct electricity into the ground. This gives the flowers at the top a slight negative charge compared to the air around them. Bees on the other hand pick up positive charges as they fly around. These charges are caused by friction with the air and between body parts. When bees touch the flowers they attract the negatively charged pollen particles from the flowers. And the electric field of the flower is reduced so that when the next bee flies by it can tell that it has just been visited.

Flower electric field

A computer model of the electric potentials around a flower

Researchers studied this phenomenon setting up electrically charged disks to stand in as flowers. Half of the disks contained sugared water and the other contained quinine, which is the bitter substance that gives tonic water it’s flavor. When the disks weren’t charged, bees landed on the disks at random landing on the bitter flowers just as often as the sweet ones. But when the sweet disk was charged, they visited it with 81% accuracy. They used the electric charge to hone in on the sweet “flowers”.

In addition to this, the plant conducts electricity, as the bee comes in closer proximity and eventually touches the flower. And once the bee leaves, the change in the plants electric field remains changed for about 2 minutes, as it build up negative charge again. During this period, the reduced electric field may serve as an indicator for other bees to know that the flower has just been visited so that they don’t stop by the pollenless plant.

Much more at the link, including how they use the electric field as an aid in determining shapes.

Source: D.Clarke et al. Detection and learning of floral electric fields by bumblebees. Science. Published online February 21, 2012

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