Torn to Ribbons in the Desert

Botanists puzzle over one of Earth's oddest plants

Judy Jernstedt admits that the plant she went almost halfway around the world to see looks “like a pile of trash.”

A Welwitschia blooms by growing an array of cones, male only on one plant and female on another. Donoghue

Tests of the carbon in this Welwitschia mirabilis show that it’s survived some 15 centuries, and it’s still going strong. von Willert

In just a few places, Welwitschia breaks the rules and sprouts an extra leaf (above) or two from the center of the regular pair. Jernstedt

That’s part of its charm. And to be fair about it, that’s not the only way that Jernstedt describes the remarkable Welwitschias of southwestern Africa. “They look like giant spiders creeping over the hills,” she says.

The stem of an adult plant–Jernstedt compares it to an upside-down traffic cone–typically has just two long, straplike leaves. They never fall off, and a plant can live for 1,500 years. In the plant’s native Namib and Mossamedes deserts, wind thrashes the leaves into ribbons. The strips get pretty tangled as the centuries go by.

Now a plant morphologist at the University of California, Davis, Jernstedt first heard about Welwitschia during her student days. “We were told how peculiar they are,” she reminisces. Some 140 years after the discovery of Welwitschia, taxonomists haven’t been able to agree on where to place this species in the tree of life.

Botanic gardens around the world now grow specimens, but they barely amount to toddlers in terms of the species’ life span. “I’ve always wanted to see Welwitschia in the wild,” says Jernstedt. Two years ago, when planning a trip to Africa, she decided to do something about this goal.

She described the results of her adventures to the annual meeting of the Botanical Society of America in Albuquerque, N.M., last August.

A dazzling plant

Jernstedt isn’t the first botanist to be bedazzled by Welwitschia. “It is out of the question the most wonderful plant ever brought to this country and one of the ugliest,” a curator at the Royal Botanic Gardens in Kew, England, commented in 1863. Two plant explorers independently discovered the species in the early 1860s. One was trekking in what’s now Namibia, and the other, in Angola. The genus name Welwitschia comes from the explorer of Angola, Friedrich Welwitsch, and taxonomists have institutionalized the astonishment of the Welwitschia discoverers by settling on the species epithet mirabilis.

The adult plant’s stem ends in a shallow bowl that can reach the size of a hubcap. From the bowl’s rim sprout the leaves that the desert winds eventually convert into a shoulder-high mass of snarled curlicues. An African name for the plant has been translated “long-haired thing.”

The plants bear arrays of small cones instead of flowers. Unlike many plant species in which male and female organs arise in the same individual, Welwitschia separates the genders. An individual’s cones carry either male reproductive parts or female ones. Droplets of sweet liquid draw flies to pollinate the plant.

The cones led botanists to first place the species with the gymnosperms, the broad group that includes conifers, ginkgoes, and seed ferns. However, cellular details of Welwitschia‘s reproduction echo processes observed within flowers. Also, the female cones sport small, leaflike bracts that might be considered a distant relative of flower parts.

Could Welwitschia represent a relic of some lineage between gymnosperms and flowering plants? Until recently, the reigning theory was that Welwitschia and its next of kin are the closest living relatives of the flowering plants, says Michael J. Donoghue of Yale University. Some molecular data, however, now suggest that Welwitschia nests within the conifers.

Michael Frohlich’s research team at the University of Michigan in Ann Arbor, for example, is working to clarify the plant’s history by comparing several genes in Welwitschia with some in other oddball cone bearers and flowering plants.

“At the moment, I would just say that there is great uncertainty, which enhances the great mystery that has always surrounded these plants,” Donoghue concludes.

Puzzling leaf formation

Part of Welwitschia‘s fascination, Jernstedt says, comes from the puzzle of its leaf formation. Carbon-14 dating has put the age of two of the plants out in the Namib Desert at roughly 1,500 years and counting. Even over centuries, the plants don’t shed their leaves. The single pair per plant endures by growing much as hair does. The tips may split and break away, but new tissue arises from the base.

Such perpetually growing leaves are rare, explains one of Jernstedt’s UC-Davis colleagues, molecular biologist Neelima Sinha. Most plants sprout leaves that can extend only to a predetermined limit. Just the tip of the plant keeps generating new tissue.

Welwitschia plants start out with a growing tip, too, but it dies off. To find the genes that control such growth patterns, Sinha and one of her students, Thinh Pham, have been studying Welwitschia seedlings in a laboratory at UC-Davis.

Jernstedt wanted to see the centuries-old Welwitschia leaves in all their tattered glory. She started her quest by searching the scientific literature and soon discovered that Dieter J. von Willert of the University of Muenster in Germany has been publishing research papers on the plant for decades.

One of von Willert’s papers particularly intrigued Jernstedt. In 1993, he reported that contrary to what Western botanists have believed for more than a century, Welwitschia in the wild sometimes grows one or two extra leaves. Seeing a wild Welwitschia would be exciting, but the chance of observing an extra-leafy one was irresistible to Jernstedt as a plant morphologist. It would be the botanical equivalent of finding mice with six legs.

Getting in touch with von Willert turned out to be easier than Jernstedt expected. The first person she consulted, a German botany researcher at UC-Davis, knew of him and quickly found his E-mail address.

Von Willert’s cordial response to Jernstedt’s inquiry contained “off-putting” cautions, she remembers. The two populations in which he had seen the extra leaves are very hard to get to. He advised finding a four-wheel-drive vehicle and a guide. “He said, ‘There are just a lot jeep tracks. A person could get pretty lost back there,'” she recalls.

When Jernstedt asked if he had used the Global Positioning System to mark the spot, he warned that his records came from the era before civilians could register coordinates with the highest resolution.

Finding the more common form of Welwitschia shouldn’t be too difficult, however. The Namibian government advertises a scenic Welwitschia drive where many plants dot the plain. “You get the impression of a forest,” says von Willert. In other areas, 10 kilometers may separate individual plants.

An extreme environment

To call von Willert the world’s foremost authority on the ecology of Welwitschia may not do him justice. He’s pretty much the only authority in that field. The research teams that he’s led to the Namib since the 1970s have provided all that’s known about how the plants cope with their extreme environment.

One of his current preoccupations grew out of an extraordinary storm that trapped his team in the Namib last year. “I got stuck in the desert–in water!” Von Willert told Science News. In just 2 days, some 10 centimeters of rain sluiced the region, which typically receives less than 25 millimeters of rain annually.

The Namib downpour set von Willert thinking about how Welwitschia start a new generation. He had noticed that many of the Welwitschia plants in the desert seem to be the same age. Maybe clustering of the ages relates to the long gaps between rains.

A female plant produces some 20,000 seeds annually. When he’s tested samples in greenhouses, “they germinate fantastically,” von Willert says. However, in the desert, he’s found that up to 90 percent of a plant’s seeds don’t germinate. Mostly, they mold. Even in a desert, a ferocious relative of the fuzz that attacks sandwiches abandoned in desk drawers claims many of a Welwitschia‘s offspring.

A Welwitschia seed that avoids mold germinates by sending a taproot down rapidly, drilling perhaps a meter in just a few weeks. It’s a life-and-death struggle to find moisture.

Von Willert proposes that rare, wet years keep the population going. In most years, drought and heat kill the seedlings. But the adults keep on producing seeds, and their long lives stretch to include years in which their offspring can win the race to moisture.

The latest dousing of the Namib was in April 2000. Starting a few days after the rain, says Von Willett, “the desert was covered by grass. It was hard to see the Welwitschias. It looked pretty, absolutely pretty.” The lush green lasted a few weeks, but Von Willert could detect the effects on some plants months later.

He has been scouring the area for new signs of Welwitschia. The number of seedlings peaked in December, he reports.

A surprise twist

Another Welwitschia matter took a surprise twist last year after puzzling von Willert off and on for decades.

The shortage of water is the main challenge for desert plants. They can’t seal their tissues completely to hold water because they need to take in carbon dioxide (CO2) for photosynthesis. Many desert plants have no leaves or tiny ones, an economy reducing vulnerable surface areas. But the square meter or so of a Welwitschia plant’s leaf surface gives up about a liter of water a day under the intense desert sun, von Willert says. That large amount of water must be coming from the plant’s exhaustive collection of soil moisture, he notes.

In the late 1970s, a colleague who was studying metabolic tricks that plants use in harsh environments proposed to von Willert that Welwitschia can conserve water by a process called crassulacean acid metabolism, or CAM. A Swiss scientist named N.T. de Saussure proposed the basics of this dodge in 1804.

He bit into a succulent, drought-tolerant plant one morning–just why we don’t know, says von Willert–and found his mouth puckering from the sourness. De Saussure tasted another nibble at the end of the day and found that the sourness was gone. Might some kind of acid have built up in the plant’s leaves during the night and then been expended during the day?

The notion was “absolutely forgotten,” von Willert says. In the mid-20th century though, physiologists realized that in tough times, some plants follow this strategy of building up acid overnight. They open their breathing pores at night, when cooler temperatures cause less of a plant’s precious moisture to escape than it does during the full heat of the day. Vital CO2 wafts into the inner cells of the leaves, but the plant can’t fully process the carbon without light.

The plant solves the dilemma by storing the carbon for photosynthesis after the sun comes up. During the dark hours, plant cells snag the CO2 gas and convert it into crassulacean acid, each molecule of which contains four carbon atoms. This acid builds up in little pockets within cells. When day comes, the breathing pores squeeze shut, and the caches of acid break down, releasing their CO2 for photosynthesis.

Plants can switch to and from the CAM water-saving mode. About half of cactus species can use CAM, and so can many of the orchids and bromeliads that cluster in tree canopies a long way from soil moisture.

To see whether Welwitschia employs CAM, Von Willert monitored day and night acidity in the leaves of a wild Welwitschia. He found no daily cycling in leaf acidity. Later, his research team took a different approach, looking for CO2 uptake during the night. Again, nothing.

A decade ago, Von Willert and his students spent 9 months in the desert monitoring gas exchange and water use by the plants. Again, the data indicated that Welwitschia don’t utilize CAM.

However, a logistical fluke brought von Willert back to the Namib last January, a month during which he’d never before done gas-exchange measurements on the plants. This time, he detected CO2 uptake during the night. The plants took up some 4 percent of their total carbon requirements through CAM, he told the Third World Conference on CAM in Cairns, Australia last August. He also noted that the shift to CAM mode came at a time of year when the plants needed extra carbon because they were pumping resources into their seeds.

Von Willert sounds remarkably good-natured about reversing a contention he’s made for decades. “Many times, I have visited Welwitschia and posed a question, and she gave me different answers, always pulling my leg,” he says.

Desert quest

Jernstedt chuckles at the question of what dramas she endured during her quest in the desert for the elusive Welwitschia. As much fun as it would be to tell of hardships and hairbreadth escapes, she confesses, “It was so easy.”

In 2000, she spent a month at the University of Botswana teaching and examining local plants. At the end of her stay, she and a biologist friend with a brand-new Global Positioning System receiver headed out with von Willert’s instructions. They rented a Toyota Corolla and, in a single day, drove 1,000 km on the Trans-Kalahari highway. They stopped at each of the three gas stations along the way.

“You have to make it one day,” Jernstedt says. At nightfall, the danger rises of hitting some of the abundant animals–kudos, warthogs, sheep, goats–bounding across the road or just basking in its warmth. Even daytime driving required intense vigilance. “One person was driving and the other one sat peering out, eyes out on stalks, watching for animals,” Jernstedt remembers.

They made it to Windhoek just after dark, but without a complete sense of relief. “If you’ve driven across the Kalahari once, that’s all you need. But we were going to have to get that rental car back,” Jernstedt says.

Colleagues had put them in touch with a driver and tracker who often took tourists to find desert rhinos and elephants.

The driver spotted the first Welwitschia plant. “[The other biologist] took a picture of me with it, and I took a picture of her and the Welwitschia, and then the guide took a picture of both of us with it. It was a thrill,” Jernstedt says.

As the party set out at sunrise in the guide’s van, a desert elephant appeared amidst some boulders. The tracker assured the visitors that just a little effort would probably give them excellent views of more elephants nearby. “We had a hard time getting the guide back focused on Welwitschias,” Jernstedt says. “He must have thought we were nuts.”

They still had some 20 kilometers to go to reach rocky Brandberg Massif, where von Willert had identified the extraleafy plants. The trip through such exotic territory did not go quickly. They stopped every kilometer or so to look at something intriguing, Jernstedt says.

As they neared the massif, cliffs and rocks often stymied their approach to von Willert’s coordinates and forced them to detour. When the van could proceed no farther, the visitors walked, finding some Welwitschias but not an anomalous one. They became uncertain that they could recognize the extra leaves among the tangles. “Everyone was asking, ‘Is this one? Is this one?'” she recalls.

After an hour of walking from plant to plant, Jernstedt spotted one with a single new leaf poking out of the center of the stem. “Here’s one,” she whooped.

“Everyone came thundering over,” she remembers. “Then, everybody could find them.”

On a later excursion into the desert, Jernstedt spotted a classic fog rolling in from the sea and asked the driver to stop so she could take a picture. They happened to pull over near more Welwitschias, and Jernstedt suddenly noticed, “My gosh, they’re weird here, too.” She had discovered a new anomalous population.

Just what the discovery means, Jernstedt hesitates to say. If the oddity is becoming more common, it might indicate some change in the environment. Or perhaps the original description of the species was too restrictive.

Or, what was that again about the plant pulling a botanist’s leg?

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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