Archive for March 5th, 2013

March 5, 2013

Let’s Rock Down to Electric Avenue

by Melissa Harding

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Pollination is essential to the life cycle of a flowering plant. Plants grow flowers in order to make seeds; this requires pollination, the process by which pollen is transferred either within a single flower or among many for the purpose of sexual reproduction. Pollination is a hard job for a plant to do by itself and many of them rely on external sources for help. While some flowers are pollinated by wind or water, most  are pollinated by critters. This most famously includes bees and butterflies, less famously also hummingbirds, fruit bats, native pollinating wasps and more. There are over 200,000 pollinating species in the world that pollinate 90% of all flowering plants. Suffice it to say that this is an important job, though many of these animals don’t even realize they are doing it.

Their ignorance is due to the fact that while some of these pollinators are actually after pollen, most others are looking for something else entirely. Flowers have spent centuries perfecting just the right incentives to attract just the right pollinators. Brightly colored petals and sepals, strong fragrances, delicious nectar, directive patterns and interesting shapes help plants draw in various pollinators to feed, breed or shelter themselves within a flower. It is often while pollinators are sucking down nectar or mating that pollen adheres to their body; after they leave to visit another flower, the pollen from the previous plant fertilizes the next plant and the next. According to Gregory Sutton at the University of Bristol in the U.K., this is just the beginning. He and his researchers have found that flowers use something totally unknown to humans before: electric fields.

Bumblebees are positively charged. As they fly, the friction of the air and the bee’s body parts together creates a positive charge. In response to this, flowers have a slight negative charge relative to the air around them; at least, they do when bees are near. In the seconds before a bee lands on a flower, there is “electrical activity” in the plant. The flower changes its potential when a bee is in proximity.  This is because when a positively charged bee lands on a flower, the negatively charged pollen grains naturally stick to it, helping along the pollination process. Once the bee leaves, the field stays changed for about 100 seconds as a warning to the next bee that there is no pollen to be found.

Another advantage of this electrical activity is that bees can sense this field and use it to find sweet flowers. Sutton and his researchers gave bees fake flowers filled with both sweet nectar and bitter quinine. Initially, the bees were random in their foraging and didn’t seem to learn which flowers held nectar. When Sutton put a charge on the flowers, the bees quickly learned to avoid the bitter ones; when turned back off, the bees resumed their random patterns. This “electric avenue” allows flowers to attract and keep repeat customers all summer long.

To learn more about Sutton and his research and to see pictures of a flower’s electric field, check out this article in NPR’s Science section. You can also read Sutton’s paper in Science magazine.

The above photo was taken by Julia Petruska.

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