After all, bees and flies aren’t as dumb as we thought, nor flowers naive. Did
you know that the flower petal is like a touch screen? Only,
we don’t know how to decode the responses. But bees and flies are much smarter and they know how to carry out small talk with flowers.
In brief such electrical interactions facilitate communication between flowers and their pollinators.
As
early as 1900’s Jagadish Chandra Bose had detected the electrical activity in
plants. Compilation of his findings could be found in his book RESPONSE IN THE LIVING AND NON-LIVING written in 1902 ( currently
available on line , thanks to gutenberg projectt ). Plant electrophysiology has since
then developed into a very interesting and active area of research. April 8th issue of Science carries a paper by Clarke et al which
describes how bumble bees can detect, read and respond to floral electric fields. In combination with color, texture, scent and nectar, the electrical impulses are powerful signals which
greatly influence the bee behavior.
Normally bees carry a slight positive charge and the flower
petals complement with a mild negative charge.
With very sensitive and specialized
instruments Clarke and his team
measured the charge carried by the bees. Of the 51
bees 94% of bees were positively
charged as expected but 6% proved to be rebels, they carried a negative charge.( I am certain, experiments are
on way to understand more about this rebel group). An equally delicate set up was used to
monitor the electrical signature of the flowers. For field trials the conformists were let out into a field of petunias.
Averaged over about 50 bee touch downs, the team registered a maximum value of 25mV
which lasted for roughly 100 seconds in a flower. In addition the team was amazed at the
quickness of the petal response which occurred within seconds. Perhaps an instant signal
to other visitors that they are
not welcome?.
The researchers tried to tempt and confuse the bees with artificial flowers, which had steel stems and plastic petals. Two sets were considered. One set carried the minimal biologically
relevant electric field and also sucrose solution as substitute for
nectar. The other set was dummy, no
electrical signal and the sugar solution was replaced with bitter quinine
solution. Naturally bees flocked to
the charged plastic
flowers. But when both sets were grounded bereft of a " come, hither" signal the bees strayed away .
Well that is not the end of the story. While reading this
paper I was reminded of another one which had appeared a month ago on how clever
and crafty the dainty flowers could be. Wright leading a team comprising of members from both sides of
Atlantic was intrigued by the presence
of minute amounts of caffeine in the nectar of citrus and coffee
flowers. Copious secretion of such
bitter alkaloids is an evolutionary
trick perfected by plants to ward of herbivores. But why traces of it in the nectar? Within the citrus family Wright
and team focused on grapefruit, pomelo, and orange blossoms and among the coffee family Arabica, liberica and canephora. They
began with the assumption that by providing nectar laced with caffeine, the
flowers might be enticing the bees to
return to them, in other words
ensuring their fidelity. Seems like
stretching a bit too much, isn’t it ? Well not at all. Their carefully controlled experiments proved precisely
the same assumption. I suggest
you read the whole paper to fully appreciate
the very logical and time consuming experiments.
Tailpiece
Did you know fruit flies
immunize their off springs at
larval stage against possible parasites?.
When mother flies suspect such
a possibility, they lay their eggs in an
alcohol enriched medium. Prof Prof Schlenke is a pioneer in this field
1. Detection and Learning of Floral Electric Fields by Bumblebees D. Clarke et al Science 5 April 2013: Vol. 340 no. 6128 pp. 66-69
2.Caffeine in Floral Nectar Enhances a Pollinator's Memory of Reward: G. A. Wright et al Science 8 March 2013: Vol. 339 no. 6124 pp. 1202-1204
3. Fruit flies medicate offspring after seeing parasites
Kacsoh
etal Science 22 February 2013 Vol.339, 6122, pp 947-950
