Questions.
What if plants turn out to need the same welfare consideration as livestock?
Do plants scream when they are attacked by a vegan?
Plant 'telepathy' breakthrough
23 May, 2013 04:00 AM
MATTHEW CAWOOD
WE can't hear it, but scientists are finding that in the
apparently silent world of plants, a whole lot of communication is going
on.
At the University of Western Australia (UWA),
researchers recently found that seeds recognise "good" or "bad"
neighbouring seeds - even when there is a plastic sheet between them.
And
in the United Kingdom, researchers have found that plants also maintain
sophisticated underground signalling networks through mycorrhizal
fungi.
If a plant is attacked by a pest, the attack is
telegraphed to other plants connected by the fungi. Those "alerted"
plants can then produce repellent compounds ahead of the pests' arrival.
The new information helps explain why the long-established
gardener's practice of companion planting, or the permaculture principle
of planting in plant "guilds", has an effectiveness that goes beyond
visible evidence of competition and community.
Mixed plant
communities compete for resources like water and light, but helpful
interactions also play out: nitrogen fixing, pest control or the
attraction of desirable insects like pollinators.
The interactions we know about are the ones we can see, like the shading effects of taller plants on those below.
Monica
Gagliano and colleagues at UWA looked at whether some other form of
invisible communication was going on. To their interest and bemusement,
it seems there is.
In an exploratory study, the researchers first looked at the interactions between chilli and fennel.
Chilli
doesn’t like fennel: when grown next to each other, the volatile
chemicals of fennel hinders the germination rate of chilli seeds.
But
when the researchers blocked all known light, chemical and touch
signals between the plant seeds - using a sheet of black plastic - the
same suppression of chilli germination occurred.
"This
demonstrated that plants were able to sense their neighbours even when
all known communication channels are blocked, and most importantly,
recognise the potential for the interfering presence of a 'bad
neighbour' and modify their growth accordingly," Dr Gagliano wrote.
The next step was to look at the effect of "good" plant neighbours: in this case, basil and chilli.
Basil,
Dr Gagliano wrote, has the capacity to act as a natural insecticide,
and to produce secondary and organic volatiles inhibiting germination
and root growth of common competitive weeds like barnyard grass and
lambsquarter.
"Besides, gardeners commonly regard it as the ideal
companion to chilli plants by virtue of its ability to keep the soil
moist and act as organic living mulch."
In their experiments,
basil proved to have a positive effect on chilli germination and growth -
and again, it didn't matter whether the plants were in visible contact
or all known sources of communication had been masked.
Dr Gagliano speculated that even at the seed stage, plants have evolved the ability to sense their neighbours in the soil.
"Because
the presence and specific identity of neighbours influence germination
timing and success, the existence of an adaptive mechanism that allows a
plant to detect its neighbours (and potentially its forthcoming
competitive environment), and hence to regulate its developmental
responses accordingly at the very onset of its life (ie. seed stage) is
clearly advantageous."
How this works remains a mystery, although
Dr Gagliano theorises that "nanomechanical oscillations of various
components in the cytoskeleton can produce a spectrum of vibrations" -
basically, seeds produce nano-sounds detectable by other seeds.
Less
mysterious, but of great significance, is the discovery by UK
researchers from several universities of an Avatar-like signalling
network broadcast through mycorrhizae.
These fungi form a
symbiotic relationship with plant roots. In exchange for compounds the
plant makes during photosynthesis, mycorrhizae transports nutrient and
moisture through its vast networks of hyphae to the host plant.
In
this sense, the fungi act as root extenders, often doubling or more the
reach of a plant's roots. Many Australian trees can't thrive in
Australia's poor soils without them.
American mycorrhizae
specialist Dr Jim Trappe, a regular visitor here, speculates that
widespread Australian tree dieback is a result of mycorrhizae networks
being killed off by fertiliser and soil compaction on farmland.
The UK research shows that the fungal networks also form an underground communications network.
The
researchers used plots of broad beans, with each plant covered with a
bag so it wasn't possible for the beans to communicate with chemicals
released into the air.
Some plots were connected through mycorrhizal networks; in others, the fungi wasn't allowed to grow.
When
aphids were introduced to one of the mycorrhizae-connected bean plants,
the levels of defensive chemicals in bean plants on the same fungal
network quickly rose.
In the unconnected beans, introducing aphids to a plant provoked no response in other plants.
John
Pickett of Rothamsted Research told the BBC that one possible use for
this knowledge would be to include particularly aphid-prone sacrificial
plants in a crop. When aphids attacked, the fungal signalling system
could raise the natural defences of more economically valuable plants.
It
could prove a robust method of switching on plant defences when needed -
without demanding the plant produce defensive chemicals all the time -
and reduce development of resistance, Professor Pickett said.
http://www.theland.com.au/news/agriculture/cropping/general-news/plant-telepathy-breakthrough/2658462.aspx
http://www.sciencedaily.com/releases/2013/05/130507060855.htm
