812-UncMtM- Faming, Saturday, January 31,1987
Enzymes Act as 'Chemical Scissors' To Regulate Plant Growth
UNIVERSITY PARK - A Penn
State biologist says plants may
regulate certain aspects of their
growth through enzymes that work
like “chemical scissors.”
Dr. Daniel J. Cosgrove, assistant
professor of biology, said, “If we
can eventually identify these
enzymes, perhaps in the future,
they can be used as chemical
primers, for example, to produce
plants with optimal form, or as
plant accelerators to produce food
or fiber plants more rapidly.”
He bases his conclusion on a
discovery made in his research on
the gravitropism or “heads up
reaction” in cucumber seedlings.
The “heads up” reaction occurs
when a plant is placed on its side.
Within an hour, the plant will have
grown so that is crown or “head” is
once again facing up and away
from the downward pull of gravity.
Scientists used to think that
turgor pressure, the internal water
pressure of the plant, might be a
factor in the process driving the
“heads up’’ reorientation.
However, using an instrument of
his own design, Cosgrove has
gathered the first direct evidence
that turgor pressure is not
Try Novelty Indoor Gardening
For An Educations! Winter Activity
FLEMINGTON, N.J. - Novelty
indoor gardening projects can be
entertaining, even educational, for
children and adults. Here are some
quick and easy ideas.
The simplest, great for children,
is a miniature forest. Spread a
layer of lentils in a shallow dish,
add water so the seeds are not
quite covered and place the dish in
a bright location. In a day the roots
will usually appear and in a few
days a tiny green forest will be
growing. Add water as needed. The
“forest” won’t last very long, but
it’s fun while it does.
Other fast germinating seeds
that make a nice display for a few
weeks in a container of potting mix
are mustard, sesame (untoasted,
of course) or grass seeds. Scatter
the seeds over the damp mix (they
could be sown in various patterns
for fun) and cover lightly with
more mix. Cover the container
with plastic until shoots appear,
then remove plastic and grow in a
bright or sunny window.
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responsible for the “heads up”
growth.
Cosgrove said, “We found that
the initial response in
gravitropism is a large burst of
growth on the lower side and a
complete cessation of growth on
the upper side of the plant’s stem.
Measurements with our pressure
probe show essentially no change
in turgor pressure on the two sides
of the stem, despite a 25 percent
per hour growth rate differential.”
He added, “The change in
growth has to come about by
changes in the cell wall.”
The most likely explanation,
according to Cosgrove, is that
enzymes act like “scissors” to snip
chemical bonds that connect the
molecules making up each plant
cell wall. The molecules can slide
past one another when the
chemical bonds are snipped
enabling the cell wall to stretch
and grow.
“No one yet has got hold of that
pair of molecular scissors,” he
said. But Cosgrove and his
research team are searching for
them with the aid of a McKnight
Foundation Individual Research
Award and a National Science
Most beans sprout very quickly
and impressively. They can simply
be planted in small containers of
potting mix, but the following
technique, described irt a 4-H
manual, makes the entire
sprouting visible. Large lima
beans are excellent to use because
of their size, but it could be fun to
try a variety of beans and even
other seeds.
Line the sides and bottom of a
glass or jar with paper towel; add
water to wet the towel and keep
some water in the bottom at all
times. Stuff the center of the lined
container with more damp
toweling to hold the lining firmly
against the glass. Then “plant” the
seeds by slipping them between the
glass and the towel liner to about
the middle of the container and
place it in a bright warm spot and
watch closely. Keep the towel
moist (the container may or may
not need to be covered) and in a
few days things will start to Pop!
Foundation Presidential Young
Investigator Award.
Cosgrove said, “These results
get us one step closer to identifying
how gravity is influencing growth
and also tells us a bit more about
the normal controls that the plant
has for regulating its own growth.
“Here is a plant that is about one
and a half millimeters in diameter
and growing just fine when you
place it vertically. You put it on its
side and in a few minutes that
upper surface, that was growing at
a good clip, stops growing and even
starts contracting. And the lower
surface doubles its growth rate. All
within the distance of one and a
half millimeters and in 10 minutes
time. To me, that is a rapid
response, in a short distance and
when we fully elucidate what is
going on, it is going to tell us a lot
about normal control of growth.”
Cosgrove has presented his
research results in an abstract in
the Journal of the American
Physiological Society and, most
recently, in October at a meeting
of the American Society for
Gravitational and Space Biology in
Charlottesville, Va. He has been
invited to present his results at the
International Botanical Congress
in Berlin in July, 1987.
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