The Science of Big, Weird Flowers

Science News, Sept 11, 1999 by Susan Milius

Even in the best of circumstances, no Rafflesia species reproduces prodigiously, and spreading human settlements threaten the habitat for lowland species. In Sabah, only half of the patches Nais monitors are protected.

"I used to be very gloomy about saving Rafflesia," Nais says. Even preserving the plant in botanic gardens didn't seem like a promising option, since only the Bogor Botanical Garden in Indonesia has succeeded in growing a Rafflesia--and its last bloom opened in 1929. Now, however, Nais reports that vines inoculated with seeds have sprouted five buds of R. keithii. He estimates that the largest bud could bloom in 5 months.

The Rafflesian past has been as puzzling as its present, according to Claude W. dePamphilis of Pennsylvania State University in State College. The species are such stripped-down parasites--literally just flowers attached to strands that infiltrate a host and steal nutrients--that botanists studying evolution don't have a lot to go on. DePamphilis hopes that DNA analysis will clarify Rafflesia's relationship to other plants.

As part of an effort to place parasitic species in the family tree of flowering plants, dePamphilis' team has sequenced two mitochondrial genes from 161 plant species, including 2 of Rafflesia. The researchers also included a wide range of plants--from water lilies and magnolias, long considered to be of ancient lineages, to newer creatures like tobacco and peas. Parasitism has arisen at least 11 times in the history of flowering plants, dePamphilis reports.

He says that the picture that's taking shape fits "surprisingly well" with the family tree emerging from another big evolutionary analysis, the collaboration called "Deep Green" (SN: 8/7/99, p. 85).

For their analysis, dePamphilis and Penn State colleague Todd J. Barkman visited Nais in Borneo to collect Rafflesia tissue samples. Because they were working with such difficult-to-obtain specimens, the researchers lugged some 80 pounds of equipment into the jungle, including a coffee grinder for pulverizing tissue, and did DNA isolations on the spot.

So far, they've found that the parasitic genus Cytinus, traditionally classified in the same family as Rafflesia, belongs much higher in the branches of the evolutionary tree, near the hibiscus order. As for the genus Rafflesia itself, "we're zeroing in" on its exact branch, dePamphilis says.

Seeing wild Rafflesia plants thrilled dePamphilis. "The buds are as big as a basketball--it's otherworldly," he says. However, he's never caught a bloom during its brief prime. "The bud we were watching didn't open until the day our plane was in the air," he says.

Not all botanical giants are so hard to see. A. titanum will display its huge blooms in captivity. Discovered on Sumatra by 19th-century explorers, it's not a parasite like Rafflesia. The jack-in-the-pulpit relative caused a sensation when a 10-year-old plant at Kew bloomed in 1887. The first bloom in the United States, at the New York Botanical Gardens in 1937, drew thousands of spectators. Paramount Studios sent a camera crew.