[Pollinator] Blowing in the wind: how hidden flower features are crucial for bees

[Ladadams at aol.com]

University of  Bristol
Blowing in the wind: how hidden flower features are crucial for bees
Press  release issued 29 May 2012 
As gardeners get busy filling tubs and borders with colourful bedding 
plants,  scientists at the Universities of Bristol and Cambridge have discovered 
more  about what makes flowers attractive to bees rather than humans. 
Published today  in the _British Ecological  Society's_ 
(http://www.britishecologicalsociety.org/)  journal _Functional  Ecology_ 
(http://www.functionalecology.org/view/0/index.html) , their research reveals that Velcro-like cells on 
plant petals  play a crucial role in helping bees grip flowers – especially 
when the wind gets  up. 
The study focuses on special cells found on the surface of petals, whose  
stunning structure is best seen under an electron microscope. According to 
lead  author, Dr Beverley Glover: “Many of our common garden flowers have 
beautiful  conical cells if you look closely – roses have rounded conical petal 
cells while  petunias have really long cells, giving petunia flowers an 
almost velvety  appearance, particularly visible in the dark-coloured varieties.”
 
Glover's group previously discovered that when offered snapdragons with  
conical cells and a mutant variety without these cells, bees prefer the former 
 because the conical cells help them grip the flower. “It's a bit like 
Velcro,  with the bee claws locking into the gaps between the cells,” she 
explains. 
Compared with many garden flowers, however, snapdragons have very 
complicated  flowers; bees have to land on a vertical face and pull open a heavy lip 
to reach  the nectar so Glover was not surprised that grip helps. But she 
wanted to  discover how conical cells help bees visiting much simpler flowers. 
“Many of our garden flowers like petunias, roses and poppies are very 
simple  saucers with nectar in the bottom, so we wanted to find out why having 
conical  cells to provide grip would be useful for bees landing on these 
flowers. We  hypothesised that maybe the grip helped when the flowers blow in the 
wind.” 
Using two types of petunia, one with conical cells and a mutant line with  
flat cells, Glover let a group of bumblebees that had never seen petunias 
before  forage in a large box containing both types of flower, and discovered 
they too  preferred the conical-celled flowers. 
They then devised a way of mimicking the way flowers move in the wind. “We  
used a lab shaking platform that we normally use to mix liquids, and put 
the  flowers on that. As we increased the speed of shaking, mimicking 
increased wind  speed, the bees increased their preference for the conical-celled 
flowers,” she  says. 
Dr Heather Whitney from the University of Bristol, and one of the 
co-authors  on the paper, says that new ways of looking at the interactions between 
plants  and pollinators are showing the ways in which plants can enhance 
their own  chances of being pollinated by helping their pollinators forage more  
successfully. "Having to land on a moving surface will increase how 
difficult it  is for bees to forage. By giving their pollinators a surface that 
increases  their grip, flowers are helping both their pollinators and in the 
long-run also  themselves." 
Katrina Alcorn, _Heather  Whitney_ 
(http://www.bristol.ac.uk/biology/people/heather-m-whitney/index.html)  and Beverley Glover (2012). 'Flower movement 
increases pollinator  preference for flowers with better grip', doi: 
10.1111/j.1365-2435.2012.02009.x  is published in Functional Ecology on Tuesday 29 
May 2012. 
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