14 JUN 2001
Superb stinkbomb
It stank so much you just had to love it. "It," of course, is the
Amorphophallus titanum, the corpse flower, a rarity from Sumatra's jungle that
just finished blooming in the greenhouse of the University of
Wisconsin-Madison botany department.
Botanist Paul Berry, master of stinkimonies, romances the corpse flower. Or is he taking the wonderful photo of the plant's interior you see on this page? Photos courtesy: University of Wisconsin-Madison department of botany, and their corpse-flower website.
The building seldom hosts anything more exciting than a few skittering birds and a smattering of preoccupied botanists. But for the past two weeks, a traffic-jam's worth of curious plant-lovers has goggled the 8-foot flower structure, sniffed expectantly for its putrid perfume, then shelled out for tee-shirts that memorialized the miasmatic moment.
For the lucky few thousand phytophiles who arrived during the female phase of flowering, the corpse flower delivered wave after wave of nauseating chemicals.
We're not in the scent business, but we'd call it an amazing aroma. A super stench. Eau de odor. The gas chromatograph analysis of air samples that were taken last week may reveal the presence of skatoles and various other
nasty-smelling sulfur compounds.
The spadex emerges from the spathe.
Nasty is as nasty smells
Nasty, after all, is exactly the point. At one point, the strange plant
attracted legions of house flies to the Wisconsin greenhouse.
That's no accident. Corpse flowers evolved to take advantage of their own style of insect pollination. (You remember pollen -- the male's contribution to the plant mating game? Pollen + egg = fertile seed.)
The corpse flower is a gregarious type, and dislikes self-pollination. So the female flowers open first, as shown above. Then, a couple of days later, the guy flowers follow. In both cases, the stench attracts beetles or houseflies, which deposit eggs in decaying flesh.
Prime suspect for amorphophallus pollination? Some scientists suspect that carrion beetles may be an important pollinator of the odorous arum titan. Maybe, but then again, maybe not, according to beetle authority Wilbert Hetterscheid. He told The Why Files that the primary pollinator of our smelly plant could just as well be another critter such as this Hybosorid beetle.
Attracted by that stench -- parfum de polecat, effluvium of excrement -- the pollinators play an essential role in moving pollen to receptive female flowers.
The plant does not just sit there and emit its sour stench, which insect pollinators are said to detect for miles. Instead, it heats itself by metabolizing sugars to hasten vaporization. During the female flowering, the top of the inflorescence was 10° warmer than air temperature.
Ferociously fetid flower
Although many visitors called the tall object a flower, it was, technically,
an inflorescence, a structure containing a few thousand small, male and female
flowers. And yes, this species makes the largest unbranched inflorescence in
the world.
For such a ponderous plant, change happens quickly. At 11 a.m. on June 7, the
day of female flowering, there was no odor and no flies. By 1:30, says Thomas
Sharkey, a University of Wisconsin-Madison professor of botany, a funky
stench, redolent of dung and death, had attracted "tons of flies."
With its spathe flared open like an upside-down hula skirt, the corpse flower emits its pungent aroma.
Stinking to attract pollinators is a common plant tactic, Sharkey points out, that is also used by the skunk cabbage, a relative of the corpse flower. And roses, lilies of the valley and peonies use more pleasant scents to attract bees and other pollinators.
The sour stench attracts insects that lay eggs in dead flesh. These natural recycling agents travel long distances carrying pollen between corpse flowers.
Size matters
But why does the A. titanum need such a giant inflorescence? "That's the
biggest, unanswered question," says Thomas Givnish, another UW-Madison botany
professor who flew like a beetle to the stinky scene. He points out that the
inflorescence of A. titanum is 100 times as tall -- and could be 1 million
times as massive -- as the inflorescence of some other members of the same
genus, Amorphophallus.
Givnish says these titanic inflorescences apparently evolved because the
reproductive advantage of a titanic blossom outweighs the metabolic cost of
making it. "Gigantic inflorescences may act as chimneys to belch hot,
foul-smelling compounds high into the air, attracting pollinators over long
distances and allowing them to move pollen among the few, distantly spaced
individuals of this rare species."
And why would an old-world corpse flower attract New-World flies? Because, Givnish opines, death smells the same the world over...
-- David Tenenbaum
Bibliography
Inflorescence Odours of Amorphophallus and Pseudodracontium (Araceae),
Geoffrey Kite et al, Phytochemistry, 46:71-75, 1997.
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