A Spark of Floral Love

Whenever I think of pretty flowers, this scene from Shrek always springs into my mind :

I think you would agree with me that the flight of the bonblebee would be incomplete without a post on bumble bee,particularly , the co-evolution of bees and flowers. You could argue that bumblebee is only an interdule in the whole episode of flowers and insects co-evolution, but nevertheless, it plays a striking chord in flower biology.

Bees have got intuitive senses to pick out and detect their ideal flowers. Symmetrical, bright colours and enchanting fragrance are voted as the most desirable partner of bees evolutionary history. Flowers’ bright colour petals are neon sign of attractiveness and their perfect symmetrical bodies captivate more than just bumblebees ; Charles Darwin described them as an “‘abominable mystery”. In February this year , Professor Daniel Robert and his group  from University of Bristol have published a paper on the discovery of  bumblebee’s ability to detect electric field.  Plants were speculated to have an electric field around them ( there is a new field of science of  “plant neurobiology” if you are interested, this is a good place to start )  to communicate signals to other plants under stress.  Flowers can beam out electric signals to their insect pollinators and  make an electrical billboard of their own.

“Pick me! Pick me!”

Bees produce a positive charge on their body as they fly. They are able to change their charges with their antennae to orientate themselves during flight, communicate with other bees and detect the weather. Sadly, this area of biology is rarely pursued after the initial findings but thankfully, Prof. Robert  has started a voyage with his group to explore  the flight of the bumble bee to its final  destination .  Plants produce a weak electric charge around them and as you may have guessed, the opposite attracts. Plants routinely carries charged molecule up and down the plant ( all minerals are carried as charged ions i.e. K+ ,Ca2+ etc) and the positive charge around them creates a negative charge on their petals.

” It’s that way. I can sense it”
Credit : Mark A. Hicks, illustrator.

This novel communication is old news. Back in 1970s, botanists have suggested this “crazy” idea of this electric attractions between flowers and pollinators. Thank you for 21st century technology, the scientists can now use electrodes to detect the electric fields.  As the bee lands on the flower, the charges changes and pollen literally jump onto the bee.  Like Charles Darwin ,the researchers asked more questions , ” does this electric field mean anything to the bees? ”  As a sensory biologist, Prof. Robert is interested in communications between living things and this sparks his interest in creating computer stimulated flowers with different electric field. Bees can use detect and discriminate different voltages of different pattern and shape of petals.  What is more fascinating is the researchers  taught the bees to associate certain patterns with certain electric fields.  For example, they made two artificial flowers ; one with sugary syrup like nectar and another with a bitter liquid . The two flowers were given different charges and over time, the bees have learnt to pick the sugary reward.  In reverse, they messed up the electric charge once they have learnt the trick and the bumble bees were awfully confused and couldn’t tell the flowers apart (awww, bless!).  The researchers also made two artificial flowers with a slightly different shades of green and the clever bees have learnt to distinguish the two with its powerful electrical senses.

Flowers are honest advertisers, they can also beam out dramatic signals when they are out of nectar or been recently visited.  If they are open for business, they would produce a much more static signals .  Flowers advertise themselves accordingly, and bees will learn its lesson and associate them with a certain electric signal . False advertisement would discredit its reputation and flowers would be out of business if bees refuse to shop there for their daily supplies again.

So flowers have evolved to produce signals to advertise its  pretty petals, sweet tasting nectar and appealing smell and bees have evolved to respond to the electric billboards – so now we know, the flower-bee co-evolution may have begin with a spark (not literally)  .



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