Trees that can tolerate soil pollution are also better at defending
themselves against pests and pathogens. "It looks like the very act of
tolerating chemical pollution may give trees an advantage from
biological invasion", says Dr Frederic E. Pitre of the University of
Montreal and one of the researchers behind the discovery.
Unexpectedly,
whilst studying the presence of genetic information (RNA) from fungi
and bacteria in the trees, the researchers found evidence of a very
large amount of RNA from a very common plant pest called the two-spotted
spidermite.
In fact, 99% of spidermite RNA was in higher
abundance in trees without contamination, suggesting that the polluted
plant's defence mechanisms, used to protect itself against chemical
contamination, improves its resistance to a biological invader.
"This
higher spidermite gene expression (RNA) in non-contaminated trees
suggests that tolerating contamination might 'prime' the trees' defence
machinery, allowing them to defend themselves better against pests, such
as spidermites," says Pitre.
While early experiments were
conducted in greenhouses, the researchers are now in the process of
repeating the work on trees grown in real contaminated sites. The have
already identified similar interactions with arachnids and insects, and
the numbers of interacting organisms, especially fungi, are very high
(often in the hundreds) for a given plant tissue when grown outside the
laboratory.
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