you think plants can't tell you're touching them, you may want to think
again. In fact, a gentle tap or squeeze may trigger a kind of "911"
call to all of the plant's cells, placing it on red alert.
the leaves probably gives the plant the feeling that it's already in the jaws
of an insect," says Frank J. Turano, a molecular
A group of students from Eleanor
Roosevelt High School
in Greenbelt, Md., helped
Turano show that even a gentle pat can send a plant's stress levels off the
To a plant, these gentle taps may
seem like the soft steps of an approaching insect, sneaking in for a bite to
eat. Turano credits the students with helping set the stage for learning
how plants make their 911 calls.
Talking, and even singing, to
plants to see how they respond is a common science fair project, he notes. But
results have been mixed.
Turano's studies suggest maybe it's
because students just aren't using the right form
of communication. Maybe, the trick is to stop talking and just reach out and
touch the plant.
Then, let it do the talking back.
happened when Turano asked the Greenbelt high schoolers to touch the plants at
1-, 2-, 5- and 15-minute intervals. The object of this touchy-feely experiment
was a type of wild mustard plant called Arabidopsis thaliana
(Uh-rab-ih-DOP-sis thal-ee-ANN-uh). By the way, the picture at left is a
test-tube grown plant, not the one used in Turano's
Turano found that the students' touching set off high levels of
two substances called amino acids. They signal that the plant is really
It may happen something like this:
touching triggers the amino acids' release. They in turn set off a chain
reaction that unlocks a gate-like area on cell walls, called receptors.
Through this receptor gate flows a stream of
electrically charged molecules called ions. They become part of the
911 call that rapidly alerts other cells--from the plant's top down to its
roots. It's probably a long distance call, but one that Ma Nature doesn't
charge for (after all, the plant is stressed enough as it is).
Turano says it's possible the
plant's long distance calling may send messages a bit like that of our own
More research is needed to prove this is what actually happens
in plants. For now, it's a hypothesis, he
says. Instead of electrical, for example, the plant's SOS signals may turn out
to be chemical.
So why worry about plant SOS signals anyway?
At ARS' Climate Stress Laboratory in
Beltsville, Turano's job was to find out how plants handle--or don't
handle--stress. This can result from severe heat or cold, dryness or
flooding or damage from chewing insects, says Turano (he's now a professor at
George Washington University in Washington, D.C.).
Eventually, the findings may help
plant breeders find ways to breed crop plants that don't get so stressed out.
For the farmer,
that could mean more crop to sell as food, fiber or livestock feed and less to
The stress research could also mean
better-adapted trees, beautiful shrubs, flowers and
Hopefully, they won't mind being
touched--or maybe it's the singing that really bugs them.
Don Comis, Information Staff,
Agricultural Research Service.