The Stench of Death, brought to you by the Forests of Sumatra

Common Name: Giant Rafflesia

A.K.A.: Rafflesia arnoldii

Vital Stats:

• One of about 28 species of Rafflesia, all parasites native to southeast Asia
• Dioecious: produces male and female flowers on separate plants
• Flowers last only a few days

Found: In the rainforests of Sumatra, Western Indonesia

It Does What?!

In my very first post here on Questionable Evolution, I discussed the Titan Arum, a.k.a. Corpse Plant, known for its pungent aroma and generally phallic appearance. This rare oddity is confined to the ever-shrinking rainforests of the western Indonesian island of Sumatra. Now meet its neighbour and fellow rotting flesh imitator, the Giant Rafflesia. Like the Titan Arum, this species is found only in the Sumatran rainforest and uses its odour to attract carrion flies for pollination. (With all the plants pretending to be dead animals on this island, it’s a wonder the flies ever actually find themselves any real carcasses.)

Rafflesia’s claim to fame in the plant world is that it produces the largest flower on Earth. A single bloom from Rafflesia arnoldii can reach a diameter of 1m (3.3’) and a mass of up to 7kg (15lbs.). In other words, one flower weighs about as much as your overweight cat. Impressive, sure, but what’s more interesting about this plant is that the flower’s the only part of it you’re ever likely to see.

Much like dodder, rafflesia is a holoparasite, depending entirely on a host plant (in this case, a vine of genus Tetrastigma, part of the grape family) for its water and nutrients. Unlike dodder, however, rafflesia doesn’t grow up and over its victim, eventually smothering it- no, this plant grows inside its host. Over the course of its evolution, the leaves, roots, and stems of rafflesia have been reduced to nothing but miniscule threads that grow, fungus-like, through the intercellular spaces of another plant, absorbing whatever they require. The giant flower arises directly from the roots or stem of the host vine, pushed out through the host’s tissues. Think chestbursters from Alien. Beyond the juvenile phase when a new seedling searches for its host, this is the only part of rafflesia that will ever see the light of day.

Interestingly, botanists have found that rafflesia’s giant flowers evolved over a very short period of time (relatively speaking), with flower diameter increases of, on average, 20cm per million years. Blindingly fast, as plant evolution goes. The reason for this, they speculate, may have been a preference on the part of certain carrion flies to feed on larger animal carcasses. The range of flower sizes seen in different species of genus Rafflesia probably functions to attract different sets of fly species with varying tastes – some want wee little dead mice, some want dead rhinoceros, judging from the size of these things.

Plants: give ‘em a few million years, and they can mimic almost anything.

Says Who?

• Barkman et al. (2008) Current Biology 18: 1508-1513
• Beaman et al. (1988) American Journal of Botany 75(8): 1148-1162
• Patifino et al. (2002) New Phytologist 154: 429-437