Plants can communicate
the onset of an attack from aphids by making use of an underground
network of fungi, researchers have found.
Instances of plant communication through the air have been
documented, in which chemicals emitted by a damaged plant can be picked
up by a neighbour.
But below ground, most land plants are connected by fungi called mycorrhizae.
The new study, published in Ecology Letters, is the first to demonstrate these fungi also aid in communication.
Researchers from the University of Aberdeen, the James Hutton
Institute and Rothamsted Research, all in the UK, devised a clever
experiment to isolate the effects of these thread-like networks of
mycorrhizae.
The team concerned themselves with aphids, tiny insects that feed on and damage plants.
Many plants have a chemical armoury that they deploy when
aphids attack, with chemicals that both repel the aphids and attract
parasitic wasps that are aphids' natural predators.
The team grew sets of five broad bean plants, allowing three
in each group to develop mycorrhizal networks, and preventing the
networks' growth in the other two.
To prevent any through-the-air chemical communication, the plants were covered with bags.
As the researchers allowed single plants in the sets to be
infested with aphids, they found that if the infested plant was
connected to another by the mycorrhizae, the un-infested plant began to
mount its chemical defence.
Those unconnected by the networks appeared not to receive the signal of attack, and showed no chemical response.
"Mycorrhizal fungi need to get [products of photosynthesis]
from the plant, and they have to do something for the plant," explained
John Pickett of Rothamsted Research.
"In the past, we thought of them making nutrients available
from the [roots and soil], but now we see another evolutionary role for
them in which they pay the plant back by transmitting the signal
efficiently," he told BBC News.
Prof Pickett expressed his "abject surprise that it was just so powerful - just such a fantastic signalling system".
The finding could be put to use in many crops that suffer
aphid damage, by arranging for a particular, "sacrificial" plant to be
more susceptible to aphid infestation, so that when aphids threaten, the
network can provide advance notice for the rest of the crop.
"Now we've got a chance in a really robust manner of
switching on the defence when it is needed - not straining the plant to
do it all the time - and to reduce the development of resistance (of the
aphids to the plants' defences)," Prof Pickett said.
Sources :
http://www.bbc.co.uk/news/science-environment-22462855
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