Here Come the Whirlybirds!

© iStockphoto.com/Olga Lis
© Jupiterimages Corp.
p r e s e n t e d b y Science a-z a d i v i s i o n o f L e a r n i n g A - Z
Here Come the
Whirlybirds!
By Ron Fridell
© iStockphoto.com/Zhang Bo
Seeds that travel by air have some ingenious strategies
for getting around. Maple seeds create lift to keep them
aloft, like helicopters. Dandelion and sunflower seeds
act like parachutes, floating through the air beneath a
puffy hat of hairs woven together in a rounded shape.
The slightest breath of wind from below takes them
aloft and propels them along. Then there is the plant
seed that looks and behaves like a kite or a glider. The
seed of the Asian gourd named Alsomitra macrocarpa
has a pair of wings that measure 13 centimeters
(5 in) from tip
to tip. The seed
rises, swoops,
and glides
through the
rainforest.
wing rotate. Seeds that catch a
breeze just right can fly a mile
or more before landing. Some
will produce new maple trees
one day.
See Whirlybirds on page 2
Chances are you’ll see
dozens of seeds that
resemble mini-helicopters,
or whirlybirds, spinning
through the air. Each
seed consists of a light,
papery wing with a heavy
seedpod attached. It’s
this pod that makes the
by Cend
eH
ill
www.sciencea-z.com
Scientists have discovered
that some plants and animals
share the same vital skill. You
can see this skill in action on
a breezy spring day. Just lie
down beneath a maple tree
and watch.
tion
stra
Illu
4
© iStockphoto.com/Vasiliy Koval
Seeds travel through the air. But what
about an entire plant that’s blown
along by the wind? The Russian
thistle, more commonly known as
the tumbleweed, breaks off from its
roots on the ground and rolls with
the wind, sometimes for dozens of
miles. On the way, it scatters tens
of thousands of seeds. Tumbleweeds
are big plants—so big that in the
American Southwest, people make
snowpeople out of them in winter.
© Learning A–Z All rights reserved.
© Jupiterimages Corp.
Ride the Wind
Maple seeds often grow
in pairs and “fly” so
that young plants don’t
compete for resources.
1
Whirlybirds
Write About This!
Continued from page 1
2
© Jupiterimages Corp.
How teeny can plant seeds get? Wolffia are the
smallest flowering plants with the smallest seeds
in the world. These aquatic plants, which look like
bits of cornmeal, are less than a millimeter long. They grow
on the surface of bodies of fresh water, where they
float freely, without roots. Wolffia seeds travel by both
wind and water, and they really get around. They have
been known to journey all the way from one continent to
another, sometimes
carried by tornadoes.
Wolffia seeds have
even been found
in the water from
melted hailstones.
© Tamu.edu
© Learning A–Z All rights reserved.
© iStockphoto.com/
Devon Stephens/
Nathan Shelton
Whirlybird is an informal word
for a helicopter, named after the
aircraft’s whirling blades. Other
helicopter nicknames include
chopper, lifter, and eggbeater.
Teeny S e e d s o n t h e M o v e
© Jupiterimages Corp.
© Vladimir Blinov/123RF
They discovered that a spinning
maple seed does just what the
wings of hummingbirds, bats,
and moths do. It generates
a vortex—a mini-tornado—
above the wing. This vortex
sucks air up from under
the wing, which pulls
the wing upward with
a force called lift—the
same force that keeps
flying animals and
helicopters airborne.
© iStockphoto.com/Artem Podobedov/Stocksnapper
Velcro™ was invented
in 1941 by engineer
George de Mestral,
who lived in Switzerland.
The idea came to him
one day after finding
burrs (seeds) that kept
sticking to his clothes
and his dog’s fur
with tiny hooks.
Maybe you remember Jack and the Beanstalk from
when you were younger—the story about a plant
that grew so tall that it climbed clear through the
clouds to a giant’s castle. Write your own fantasy
story for kids about a fantastic plant. Maybe you
have a little brother or sister you could read it
to, or a class of young children in your school.
© iStockphoto.com/Benzo
A team of scientists wondered:
How could these whirlybirds
stay in the air for so long and fly
so far? To find out, they made
an oversized plastic model of
a maple seed and attached
it to a robotic arm. Then they
observed the model as it spun.
Each green spec is a whole plant.
3
www.sciencea-z.com