Iridescent flowers 'attract bees'
Updated on 01 January 2009
Bees live in a paintbox world in which flowers take on different colours depending on the angle from which they are viewed, new research has shown.
Flower petals use the property, known as iridescence, to attract pollinators, scientists have discovered.
Iridescence has nothing to do with colour pigment but depends on surface structure. Compact discs are an example of a man-made iridescent object.
Scientists already knew that insects, birds, fish and reptiles use iridescence for species recognition and mate selection.
The new research shows for the first time that plants use iridescence as well as colour pigment to make themselves attractive to bees.
British scientists identified iridescence in Hibiscus and Tulip flowers, and showed that bumblebees could separate iridescence and colour. The bees could also use iridescence as a reward signal.
In laboratory experiments, bumblebees were taught to recognise that iridescent discs containing yellow, blue or violet pigments offered a sugary reward. They learned to fly to these discs and avoid others with the same pigments which were not iridescent.
The findings were reported on Friday in the journal Science.
Most petal iridescence is at the ultraviolet end of the light spectrum which is visible to insects but not to humans.
Dr Beverley Glover, from Cambridge University, who led the study, said: "Our initial survey of plants suggests that iridescence may be very widespread. From gardening to agriculture, flowers and their pollinators play an enormously important role in our daily lives, and it is intriguing to realise that they are signalling to each other with flashing multicolours that we simply can't see."
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