source Live Science
By Sara Goudarzi, Special to LiveScience
posted: 08 October 2007
Plants chatter amongst themselves to spread information, a lot like humans and other animals, new research suggests.
A unique internal network apparently allows greens to warn each other against predators and potential enemies.
Many herbal plants such as strawberry, clover, reed and ground elder
naturally form a set of connections to share information with each
other through channels known as runners—horizontal stems that
physically bond the plants like tubes or cables along the soil surface
and underground. Though connected to vertical stems, runners eventually
form new buds at the tips and ultimately form a network of plants.
“Network-like plants do not usually produce vertical stems but their
stems lie flat on the ground and can hence be used as network
infrastructure,” said researcher Josef Stuefer from the Radboud
University in the Netherlands.
Stuefer and his team let loose caterpillars on white clover plants
and watched them eat a single leaf on the network. Then a second set of
caterpillars was allowed to choose between the damaged leaf—one that
has been alerted to up its defense status—and leaves from an undamaged
network.
Over the course of 20 trials, most or all of the approximately 15
caterpillars in each trial preferred the undamaged leaf to the leaf
from a damaged network.
“The feeding caterpillars will be deterred and walk off to feed on
other non-induced plants,” Stuefer told LiveScience. “[They] understand
plant defense language very well as it is directed exactly to them.”
Here is how it works: If one of the network plants is attacked by
caterpillars, the other members of the network are warned via an
internal signal to upgrade their chemical and mechanical
resistance—making their leaves hard to chew on and less desirable. This
system works to spread the information amongst the plants and to ward
off caterpillars.
“This is an early warning system, very much like in military
defense, but then more effective: each member of the network can
receive the external signal of impending herbivore danger and transmit
it to the other members of the network,” Stuefer said. The attacked
leaf is lost. However, the remaining leaves are protected against
predators.
The study is detailed in this month’s issue of the journal Oecologia.
According to the researchers, the principle of network transfer of
substances is known for very many species, including numerous invasive
plants such as bracken and reed and commercial crop species such as
bamboo.
The downside to these connections is that viruses often use the
runner infrastructure to quickly spread. They enter the plant via the
leaves, find their way into the stems and are then passively
transported to all the network members where they cause new infections.
“Many pathogens are host specific, meaning that they can infect only
very specific plant species,” Stuefer said. “Their main challenge for
survival is to find a new host after one has been infected. Such
specialists have an especially big advantage from network infections as
the physical connection between plants enables them to find genetically
identical copies of the original host.”
This, Stuefer explains, is comparable to a computer virus
specialized to infect computers with a certain version of the Windows
operating system. “Such a virus spreads very fast if all terminals on a
network have the correct Windows version while its spread is slowed
down if there is variability in the systems,” he said.
HemuZ Nature
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