By Will Dunham
WASHINGTON (Reuters) - It's the world's biggest flower, and maybe the stinkiest, too.
And now scientists have used genetic analysis to solve the
long-standing mystery of the lineage of the rafflesia flower, known for
its blood-red bloom measuring three feet (1 meter) wide and its
nauseating stench of rotting flesh.
Writing in the journal
Science on Thursday, a team of researchers said rafflesia -- discovered
in an 1818 scientific expedition to a Sumatran rain forest -- comes
from an ancient family of plants known not for big flowers, but for
In fact, many of its botanical cousins boast flowers just a few millimeters wide.
This family, called Euphorbiaceae, also includes the poinsettia, Irish
bells and crops such as the rubber tree, castor oil plant and cassava
shrub, the researchers said.
Rafflesia's many odd
characteristics long had tripped up scientists trying to figure out
where it fit on the botanical tree of life. It is sort of a botanical
outlaw -- a parasitic plant that steals nutrients from another plant
while deceiving insects into pollinating it.
"They really are a
funky plant," Harvard University plant biologist Charles Davis, who led
the research, said in an interview.
rah-FLEEZ-ee-ah) lives inside the tissue of a tropical vine related to
the grapevine, with only its flower visible. It is devoid of leaves,
shoots and roots, and does not engage in photosynthesis, the process
plants use to exploit the energy from sunlight.
Its flowers can
weigh 15 pounds (7 kg). They are a blotchy blood red. They smell like
decaying flesh. And they even can emit heat, perhaps mimicking a newly
killed animal in order to entice the carrion flies that pollinate it.
"They really do look and smell like rotting flesh. They are a totally
fetid, stinking, foul kind of flower. It can be totally repulsive to so
many of us. But to the flies that visit these things, it's just
delightful," Davis said.
There are various species of rafflesia
growing on the floor of rain forests in parts of Southeast Asia, with
Borneo the center of its diversity, Davis said.
Davis said its
lineage dates back roughly 100 million years to the Cretaceous Period,
the last act of the Age of Dinosaurs when flowering plants are believed
to have first appeared. The researchers determined that over a span of
46 million years, rafflesia's flowers evolved a 79-fold increase in
size before assuming a slower evolutionary pace.
to nail down plant lineages have relied on molecular markers in genes
relating to photosynthesis, but that was not possible with rafflesia.
The researchers had to scour other parts of its genome for clues.
"These plants are so bizarre that no matter where you put them with any
group of plants, you're going to have a lot of explaining to do," Davis
said. "But what was surprising was that with all of the options
available as close relatives, they are nested within this group of
plants with absolutely tiny flowers."
University plant biologist Daniel Nickrent, who took part in the
research, said this deeper understanding of rafflesia might aid people
keen to develop larger flowers and fruits.
It was discovered on
an expedition led by Sir Thomas Stamford Raffles, who founded the
British colony of Singapore, and naturalist Joseph Arnold, who died of
malaria on the trip.
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