First FlowerPBS Airdate: April 17, 2007 NARRATOR: Flowering plants delight our senses; we love them in our gardens. Yet it is little appreciated that they are the basis of our food. In fact, humans would not have evolved without them. But, for the plant, flowers are an enormous drain on limited resources, so why even have flowers? DAVID DILCHER (Paleobotanist, University of Florida): Flowers are all about sex, that's for sure. NARRATOR: The origin of flowers is one of botany's most enduring mysteries. Darwin called the mystery "abominable." Now two teams of scientists have set out across China to solve that mystery. YIN KAIPU (Botanist, Chengdu Institute of Biology): Lily sargentiae. NARRATOR: One team is searching for the clues that are held by living plants. DANIEL J. HINKLEY (Horticulturist and Plant Explorer): Oh, my gosh! There's a lot of people that would love to be here right this moment. NARRATOR: The other believes it has found an extraordinary fossil that could be the world's first flower. DAVID DILCHER: That's history right there. NARRATOR: Together, can they solve this evolutionary mystery? Tonight on NOVA, The First Flower. Major funding for NOVA is provided by the Howard Hughes Medical Institute, serving society through biomedical research and science education: HHMI. And by the Corporation for Public Broadcasting, and by contributions to your PBS station by viewers like you. Thank you. NARRATOR: Flowers hold a special place in the natural world and in the human heart. But flowering plants are not just fragrant, decorative objects, they are essential to human life. Almost all our food, including wheat, corn and rice, is derived from them, as are many medicines, old and new. But where did flowers themselves come from? Professor Sun Ge, from China's Jilin University, is certain that early flowers evolved here, in northern China, and he is determined to find the world's first. Not far from the border of Inner Mongolia, there is a remarkable fossil site that is revealing what the Earth looked like more than 100,000,000 years ago. SUN GE (Paleobotanist, Jilin University): Fossils form in between the layers of sediment. Searching for fossils is like opening the pages of a book. We look page by page by page.
NARRATOR: Sun Ge searched for more than a decade, through these layers of rock, without success. One day a student dropped off three new fossils at his office. The first two were plants Sun Ge had seen before. SUN GE: Then I looked at the third one. I was surprised. It was a very strange fossil. I was very excited. NARRATOR: The fossil was unlike anything Sun Ge had ever seen before. At the top of two simple branches were structures that appeared to enclose seeds. An enclosed seed is a defining feature of a flower, today. Could this be an early flower? After months of analysis, Sun Ge decided to share it with a fellow botanist in the United States. This priceless fossil, that had been buried deep in the earth for more than a hundred million years, had to endure one more burial in another kind of tomb. Sun Ge brought the fossil to his longtime friend and colleague David Dilcher, of the University of Florida, for another opinion. DAVID DILCHER: Yeah, it could be. It really...I think maybe you're right, that it could be. NARRATOR: Dilcher is one of the world's leading paleobotanists, which is the study of ancient plants and their fossils. His passion is trying to understand the origin of flowers. DAVID DILCHER: I've been looking for the earliest flowering plant in the world for, probably, 35 years. NARRATOR: Before flowers, the Earth was covered with green plants like ferns, pines, and the now-extinct seed ferns. Their reproduction was relatively slow and inefficient. Pollination was mostly carried out by the wind. Eventually, the fossil record shows that flowering plants came to dominate the globe. They, clearly, were the winning evolutionary strategy. DAVID DILCHER: In numbers of species, I would guess that 95 percent of the plants that we are in contact with are flowering plants. NARRATOR: Flowers take enormous energy for a plant to produce. They may be beautiful, but that beauty is, in one sense, a burden. So why have flowers at all? When and how flowering plants began has long been one of botany's biggest and most beautiful mysteries. Could this strange new fossil from northern China solve that enduring mystery? One of the best places on Earth to see the results of the evolution of flowering plants is the Hengduan Mountains in southwestern China, which span the regions of Sichuan, Hunan and Tibet. This is the most biodiverse temperate forest in the world. But to a plant lover it feels strangely familiar, because this is where many of the flowers in your garden came from. Professor Yin Kaipu, a botanist from Chengdu, has spent his life studying the diversity of plants in the Hengduan Mountains. YIN KAIPU: Everyone who comes here falls in love with this place. The scenery is sublime, it's beautiful. The biodiversity is so rich. It's why most of the world botanists feel that this is a living museum of plant evolution. NARRATOR: While Sun Ge and Dilcher are studying evolution from the ancient fossil record, Yin is taking a different path. He is documenting the outcome of that evolution through a catalogue of living plants. How did such an astonishing array of colors, patterns, shapes and sizes evolve? And how are they related? Finding and cataloguing plants is essential to answering that question. As part of that effort, Professor Yin has been joined by Dan Hinkley, an American plant explorer. DAN HINKLEY: China's the mother of all gardens. Whether it be the ferns, whether it be the maples, the rhododendrons, camellias, the lilies, the iris, we're in their place of origin. Right here is where they came from. NARRATOR: Their first stop is an alpine meadow at 14,000 feet. Hinkley barely gets of the car before he sees what makes the Hengduan Mountains so special. YIN KAIPU: Look! Lilium lophophorum. DAN HINKLEY: Ah, Lilium lophophorum. Oh, my gosh, the first time I've ever seen this in blossom. It's fantastic. And corydalis here. Curviflora. And alium, geranium. Look at that. Should we come up? Oh, my gosh, that's just extraordinary. Lilium lophophorum—it's the first time I've seen it in flower. The petals don't completely dis-attach which makes it so exquisite. So, we have hardy geraniums, lilies, gentians, euphorbias. There is even an edelweiss here, Leontopodium—which in mostly associated with the Alps in Europe—a spruce, picea; Potentilla; primulas; anemones. It is absolutely staggering the number of genera that we are familiar with in the garden setting that is in this small little piece of land in front of me, that has been grazed by yak and cut for the roadway. Ligularia, botrychium, which is a fern, and arenaria, it's…spirea. It goes on and on. It's absolutely staggering. This little anenome is quite exquisite, I think, particularly so for that blue staining on the undersurface of each sepal. YIN KAIPU: A lily; there's a lily. DAN HINKLEY: I'm not sure, but I think that, unless you are looking at something else, I think this is another lily. The same lily. Yeah, it's lily and… Oh jeez! I just saw it. Oh, god, that is unbelievable. Oh my god, this is extraordinary. NARRATOR: Cypripedium tibeticum is a rare species of the much sought after lady slipper orchids, named after the unusual pouch created by a modified petal. DAN HINKLEY: Professor Yin, unbelievable! There's a lot of people that would love to be here, at this moment, sitting in yak dung. It is just amazing to see this. NARRATOR: Whether it be finding one rare flower or one unique fossil, they are both essential parts of understanding the evolution of flowering plants. One of the things that make the Hengduan Mountains such a rich breeding ground for plant life is the variety of climates. They like to say, here, that you can experience all four seasons in one day. Within a few hours you can drive from mountains, where the air is damp and cold, to valleys, where it's summer and there are cacti at the side of the road. DAN HINKLEY: It is incredibly hot. NARRATOR: The unique conditions allowed many of the flowers here to survive the last Ice Age. In other countries around the globe thousands of species of plants were stripped clean by the glaciers. The Hengduan Mountains have, in effect, served as a safety deposit box of temperate diversity. Half a world away there is another kind of safety deposit box of plant diversity, David Dilcher's fossil collection at the Florida Museum of Natural History. These drawers hold over a quarter million fossils and document the evolution of plant life on Earth. DAVID DILCHER: This would be a little over 300,000,000 years old. It's a totally extinct group of plants today, but it's what made up the coal age forests. NARRATOR: The fossil record shows that, while flowering plants evolved rather late, they came to dominate the Earth. DAVID DILCHER: The origin of flowers is a very important phenomenon in the history of the Earth. Humans are a result of this evolutionary event. We would not be here if we didn't have the products of flowering plants to eat. NARRATOR: But clarifying the steps of flowering plant evolution has been difficult, in part because most plants decompose before they ever become a fossil. Usually only fragments remain, which is one of the things that makes this strange new fossil from China so extraordinary. The details of the plant are beautifully preserved. Sun Ge named it Archaefructus, which refers to the fossil's ancient fruits. But how ancient is Archaefructus? SUN GE: This is typical Jurassic rocks with the red color. From this formation we have found a lot of dinosaurs. NARRATOR: Some of the rock layers here in northwestern China date back 150 million years to the Jurassic Period, the heyday of dinosaurs. If Archaefructus could be proven to be a Jurassic flowering plant, it would surely be one of the world's very first. In the months following the initial discovery, Sun Ge and his team turned up several more Archaefructus fossils in the same location. Each new discovery added important details to what this plant looked like. DAVID DILCHER: It's nice to see this is an axillary shoot coming out. The first flowering plants didn't resemble any flowers we know today. They didn't have petals, they didn't have fragrance, they weren't beautiful. They simply were functional. NARRATOR: To understand why this fossil that looks nothing like a flower could be one of the world's first, you have to understand what the function of flowers is. DAVID DILCHER: They are all about sex. Yeah, yeah, flowers are all about sex, that's for sure. They're managing the reproductive biology for the plant, and the reproductive biology happens to be a sexual process. To illustrate the basic sex life of a flower, we can use a lily. There are, of course, the recognizable petals, but at its center are the real stars: the stamens are the male parts that produce pollen; the pistil is the female part that contains the ovaries. Plants have elaborate strategies to avoid self-pollination, like the female part ripening at a different time than the male pollen. When the pollen from another flower lands on the pistil—usually deposited by a passing insect—a pollen tube grows down, carrying the sperm to the egg, and reproduction takes place, producing seeds inside of a fruit. The pretty flower, therefore, with those recognizable petals and scent, is really just good packaging. DAVID DILCHER: Flowering plants were the first advertisers in the world. They put out beautiful petals, colorful patterns, they put out fragrances, and they gave a reward, such as nectar or pollen, for any insect that would come and visit them. And what were they advertising? They were advertising the sexual organs, the female parts and the male parts that were hidden or positioned within the center of this flower. So if they could attract these mobile pollinators to come and mess around, crawl around, feed in this flower, pick up pollen on the legs, pick up pollen on the body, and then fly to another flower some distance away and repeat this process, they could effectively carry their male genetic material in the pollen grain to another flower. DAN HINKLEY: It's so tempting to believe that this palate of color and form and texture is actually here for the benefit of our own eyes. But in truth, what we're looking at is simply an unfolding of the story of the survival of their own species. NARRATOR: The story of flower evolution is integrally linked with that of its pollinators, like insects and birds. This co-evolution has been largely responsible for their remarkable diversity. It is believed that there may be as many as 400,000 different species of flowering plants, including things as different as roses, wheat and even apple trees.
DAN HINKLEY: Oh, my god. I can't believe it. I have been wanting to see this. This is mandragora—made famous by Harry Potter—and here it's already setting fruit…absolutely fantastic. All flowering plants flower, all flowering plant that flower fruit. The fruit is the new generation, whether it's an apple or whether it's a pumpkin, whether it's this poisonous berry, it's the point of flowering. It is the renewal of the species, the enhancement of the species as well. This seed possesses that little bit of difference that may allow it to adapt, down the road, to a different set of circumstances that it might encounter. NARRATOR: Dilcher believes that this fossil from China, while not beautiful, is the first plant to have the basic pollen- and seed-producing organs of a modern flower. This fossil shows Archaefructus, like a modern lily, had male pollen-producing organs and the female organs, called carpels, which are similar to pistils. Inside the carpels are the eggs that, when fertilized, become seeds. But unlike the lily, these organs are spread out along a stem. Dilcher believes that over the long course of evolution this stem would have shrunk, pulling the organs together for efficient pollination, and changing the leaves to colorful, attractive petals, creating what we think of as a flower. DAVID DILCHER: We saw the carpals, we saw the seeds enclosed by the carpals, and Sun Ge and I knew that this, in fact, was the first flower in the world. It was a thrilling experience. NARRATOR: Right or wrong, Sun Ge and Dilcher are in for a contentious fight if they want to prove that this is the world's first flower. Flowers have always aroused passions, and the hunt to find new flowers or their fossils has long driven botanist to extremes. Professor Yin and Dan Hinkley are retracing the footsteps of the famous British plant explorer, Ernest H. Wilson, who traveled to China in the early 1900s. Wilson is one of the greats of plant exploration. He led four expeditions here in search of plants for English and American gardens. By any standard he was phenomenally successful. He introduced to the west some 1,500 plants, including new species of rhododendrons, dogwoods, clematis, forsythia, poppies, primulas and roses. But flower hunting in the 1900s was a very risky business, and Wilson's obsession with this flower nearly cost him his life. The regal lily is a very common flower around the world today, yet its only natural habitat is clinging to the rocky cliffs in a 60-mile stretch in this narrow valley in western China. In 1910, just after locating thousands of lily bulbs, Wilson's caravan was hit by a landslide. A rock shattered Wilson's leg in two places. YIN KAIPU: Wilson bore with the pain and used his tripod to splint his leg. Then, from the direction of Dujiangyan came 40 or 50 mules on the way to Songpan. Wilson couldn't retreat; the mules couldn't retreat. So he just lay on the ground to let the 50 mules step over him. NARRATOR: Wilson contracted gangrene but managed to fight off amputation of his leg. He was left with a severe limp that he nicknamed his "lily limp." But Wilson's legacy, and that of the regal lily, lives on, literally, in your garden. Wilson's legacy also lives on at the Royal Botanic Gardens at Kew, outside of London. Here is one of the world's largest herbariums, or library of dried plants. Peter Crane is a leading paleobotanist and the former director at Kew. SIR PETER CRANE (Paleobotanist, University of Chicago): Inside this building we have somewhere between seven- and eight million herbarium specimens that represent the diversity of life, botanical life, on this planet. NARRATOR: And among those specimens is the very one collected by E. H. Wilson in that narrow valley in China: Lilium regale. PETER CRANE: It's a beautiful and fascinating plant and one of the great introductions into horticulture that Wilson made. NARRATOR: The study of plants has been essential to man throughout human history because of their importance to food, medicines and economies. Understanding them requires figuring out how they are interrelated, which is done in part by classifying—sorting and trying to arrange them into a family tree of plants. At the heart of this collection are the type specimens, the first plant collected of a type, the example that defines the species. PETER CRANE: This one, in particular, is a fantastic one, because it was especially collected by Darwin on the voyage of the Beagle. And it's actually a species of gentian. It would probably have had a nice blue flower when it was fresh. Even though it looks a good deal less inspiring than it did the day when Darwin picked it, under the microscope all the fine details are still there, and you would be able to study it, right down to the individual little pollen grains. Darwin showed that the whole diversity of life was interconnected. What that left unsolved was exactly how did the diversity of plant life or, indeed animal life, for that matter, how did it fit together? Who was related to who? What exactly did the family tree look like? Darwin knew that the family tree was out there. What he didn't have any means of addressing was exactly how all of these different forms were interrelated. DAVID DILCHER: At the time of Darwin, when he examined the record of the earliest flowering plants, he found there was a time when there were no flowering plants, and then suddenly there was a time when flowering plants were there, and they were full-formed. And he expressed it as an "abominable mystery." PETER CRANE: It's a nice Victorian word. And I think "abominable" because it, sort of, defied his understanding. He wanted to go deeper. He knew there was something there that needed to be understood. And I think it was sort of gnawing away at him, maybe annoying him. DAVID DILCHER: Well, it's exciting to be back. NARRATOR: Solving that abominable mystery is what Dilcher and Sun Ge are trying to do. They've returned to the site of Sun's original discovery in Beipiao, China, to learn more about the fossil's original habitat. DAVID DILCHER: It's important, to…oh, look at that. NARRATOR: Is the Archaefructus one of those early evolutionary stages of flowering plants that Darwin looked for? A prototype, or early test model, for the flower? SUN GE: From this specimen, we can see the root system is very weak or underdeveloped. This is typical of aquatic plants. DAVID DILCHER: You've got to break a lot or rock to find anything. Oh, yeah, here's some plant material, yeah. SUN GE: Look at this one. Looks like the fish, this one. NARRATOR: At the time Archaefructus was living, this area was a large inland lake, and Dilcher and Sun Ge believe Archaefructus evolved at the edge of the lake. But ancient fossils can be interpreted in different ways. ELSE MARIE FRIIS (Swedish Museum of Natural History): Archaefructus is not the first flower. It's a very interesting fossil, but it's not the oldest. NARRATOR: Else Marie Friis, a leading paleobotanist in Stockholm, has analyzed Archaefructus, as well, and disagrees with Dilcher and Sun Ge. ELSE MARIE FRIIS: We still have a long way to go before we know the truth about the roots of the flowering plants. NARRATOR: Friis believes that Archaefructus shows signs of having adapted to live in the water, which would mean that it is a more evolved plant, and not the first flower. She, too, is looking for the world's oldest flower but has taken a different route. Instead of breaking open rocks, she started sifting through ancient sediments, looking for bits of leaves and seeds. ELSE MARIE FRIIS: We used rather coarse sieves, but then we found out that there was a lot of small things also floating away, and we then started using finer sieves. NARRATOR: Hour after hour, Friis would sort through the fragments of plants. Then one day she saw something that startled even her. By looking piece by piece at these bits of plants, she discovered that some of them were tiny, whole flowers. ELSE MARIE FRIIS: It was very exciting to see, of course. It was fantastic. There were so many details preserved. NARRATOR: Here were flowers, millions of years old, that are, in effect, still in bloom. In very special sediments, these tiny flowers had turned into charcoal and were preserved intact. ELSE MARIE FRIIS: Here you can see the petals, in white, and being three-dimensionally preserved, they keep their original shape, so you can see the position of the various organs. NARRATOR: The oldest of these tiny flowers has been found to be 120 million years old. For Archaefructus to be the first flower, it must be older. That kept the pressure on Sun Ge and Dilcher to prove just how old Archaefructus really was, and the doubts were growing. PETER CRANE: There are a number of problems in claiming that anything is the first flower. One is you've got to be absolutely sure on the timing, that it really is the first. And that's not an easy question to resolve. And then you've got to assume at the same time there was nothing else out there. So you have to assume that what you found is the only thing that is around at that time. Which, of course, is, in a way, an absurd assumption because we know in the fossil record, wherever you look, that there's more that we don't know than that we actually know about. NARRATOR: Sun Ge and Dilcher dated Archaefructus at just over 140 million years old, based on the other fossils found in this area. This put it in the Jurassic period, the age of dinosaurs. No one had ever found a flowering plant from the Jurassic period. It was the botanical equivalent of breaking the sound barrier, and it led to its own kind of explosion. Archaefructus graced the cover of Science magazine and the pages of the New York Times. This ancient plant had a very modern "15 minutes of fame." LEO HICKEY (Paleobotanist, Yale University): Archaefructus surprised me because it was a little too advanced to have been…at least to fit my model of the earliest flowering plant. So I was quite skeptical of the age, of the date. And I went back and began to investigate. NARRATOR: Leo Hickey, at Yale University, has taken another approach to tracing the first flower: a kind of scientific reading of the tea leaves. LEO HICKEY: Leaves can actually tell us surprising amount about evolution. A leaf is the principle way in which a plant engages its environment. That's its light-capturing device, and small changes in the orientation of the leaf or the vein pattern will make a big difference in the yield of sugar for the plant. NARRATOR: Hickey discovered that leaves have very different patterns in their veins, and understanding those patterns was a clue to their evolution. LEO HICKEY: This is a very primitive and disorganized pattern. There is very little regularity to the veins that lie in between these thicker veins. The thicker veins themselves sort of wander around a bit. This is a much more advanced leaf. You'll notice the veins are very straight. NARRATOR: The most advanced leaves have veins that are straighter and efficient, like good plumbing. LEO HICKEY: Modern leaves are just better engineered. Evolution works on an economic model. Those that can make it cheaper and quicker and more efficiently are the ones that probably are going to survive. NARRATOR: But leaves can only take you so far in this analysis. The electron microscope brought into focus previously unseen detail of plant pollen. Pollen is far more common in the fossil record than are leaves. LEO HICKEY: Leaves are found here and there. Pollen can be found in many, many sediments. The pollen evidence was the nice dating tool. NARRATOR: Seeing the intricate details of individual pollen grains allowed scientists to identify the distinctive pollen from flowering plants and then figure out when that pollen began showing up on Earth. Their answer? LEO HICKEY: The very earliest flowering plant pollen shows up in rocks, which are of cretaceous age, which is about 134 million years in this case. NARRATOR: This was a startling discovery. It could help answer Darwin's question about when flowering plants began, but it puts into doubt the age of Archaefructus. How could Archaefructus be almost 10 million years older than any known flowering plant pollen? The only sure way to find out was to date the earth that encased Archaefructus. A team from Berkeley, California, and China measured the radioactive decay in minerals from the fossil site. The results were not what Sun Ge and Dilcher had hoped for. The new evidence moved the fossil's age from 144 million years old to 124.6 million, which was more in line with the pollen evidence. This still means that Archaefructus is the oldest known complete flowering plant fossil, but it moved it from the Jurassic period to the early Cretaceous, something of a paleontologic demotion. DAVID DILCHER: The focus changed suddenly to the fact that, "Oh, this is a paleobotanical mistake, here is an incorrect age." And that disappointed me quite a bit because I was interested in the excitement of the early flowering plants. And even the fact that it was 14, 16 million years younger than we initially reported it, it still was the most complete, earliest record of flowering plants that we have available. NARRATOR: In the spectacular Hengduan Mountains, the scientific controversy about Archaefructus seems much less heated. But what is happening here is revealing new clues to what these arguments are all about. The way the family tree was sorted out for centuries was by comparing various features of plants, like their leaves or pollen. Differences in these structures were indicators of evolutionary change, and the basis for figuring out where it belonged on the family tree. A beautiful example of how to classify different looking plants into related species can be seen in the flowers that carpet these mountains in spring: the rhododendron. There are less than 30 wild species in North America, yet more than 500 in China. The rhododendron has thrived here because of its ability to adapt and develop new species. YIN KAIPU: Look how small these leaves are. As the Qingzang plateau rose, these plants adapted to the higher altitude. Their leaves became smaller, thicker and grew hair. This is an adaptation to prevent moisture loss in the cold climate and strong winds of high altitude. DAN HINKLEY: Look at this rhododendron…absolutely amazing foliage. NARRATOR: Their lower altitude cousins have evolved quite differently. DAN HINKLEY: Fifteen inches…it must be 50 feet tall. NARRATOR: Different as these rhododendrons may at first appear, their basic features, like leaves, are quite similar in structure. YIN KAIPU: There's a Sorbus. NARRATOR: In the last 40 years, Professor Yin and the Chengdu Institute of Biology have catalogued thousands of different species of plants in the Hengduan Mountains. DAN HINKLEY: All right, Professor, if there are any snakes, you scare them away from the trail, all right? Before I get there. YIN KAIPU: No snakes here—leeches. DAN HINKLEY: Leeches? Great! NARRATOR: Finding the relationships of similar looking rhododendrons is relatively easy, but classifying the hundreds of thousands of known plant species quickly becomes overwhelming. DAN HINKLEY: There's Polygonatum here, Smilacina, actinidia—a kiwi, there's a viburnum. And then there's impatiens growing around the base, not to mention the grasses. It's staggering. PETER CRANE: Getting this classification straight is really very, very important. It matters a lot, where they came from and what they are related to. That tells you a lot about why they are the way they are today. NARRATOR: Just a few blocks away from the fabled herbarium at Kew Gardens, scientists have a new tool to sort this all out. Today, genetic material, or DNA, from living plants is helping to build a more accurate family tree. MARK CHASE (Evolutionary Botanist, Kew Gardens): Getting DNA from a plant is one of the easiest things to do. You can actually do it in your kitchen. It doesn't look like anything when you can see it, of course. You are looking at millions and millions of base pairs of DNA. NARRATOR: This slimy glob is the plant's DNA and is made up of the four familiar bases, A, C, T, and G. Mark Chase, the head of the laboratory, translated that DNA evidence into a massive computer matrix. Thousands of base pairs of DNA for each plant are put into the matrix, and then compared with other plants. The color coding of the base pairs helps to identify differences. It is the multi-species plant equivalent of the human genome project. MARK CHASE: There were 43 co-authors on the paper. This was a mammoth undertaking. NARRATOR: The computer analysis was so complex it required a consortium of scientists, including Doug and Pam Soltis of the University of Florida. PAM SOLTIS (Molecular Botanist, University of Florida): The same sort of analysis is done in the animal kingdom. For example, humans and chimps have DNA sequences that are 99-point-something percent the same. And by inference then, the chimps are the closest relatives to the humans. NARRATOR: The closer the DNA sequence, the closer the evolutionary relationship of two plants, which then allows them to group similar plants into related families. The results aren't so easy to get your hands around. PAM SOLTIS: This part is not-flowering plants, and this part is not-flowering plants, and everything in the middle is flowering plants. DOUG SOLTIS (Molecular Botanist, University of Florida): So we have many, many hundreds…thousands of plants that are representing the diversity of green life. You can see each line is a different plant. And what we can see on this tree is that some come out very close together. And those are close relatives. Those are what we call a closely related group or clade. So here is one small clade, here's a larger group or cluster of clades, and then so on and so on and so on, down through the green plant tree of life. NARRATOR: Now with the assurance of DNA insight, the family tree of living flowering plants has largely been written. The old family tree was now in for a major pruning. Roses were found to be closely related to squash, strawberries to marijuana, this meat-eating pitcher plant to China's famous rhododendrons. For centuries water lilies were thought to be nearly twins with the lotus—no longer. MARK CHASE: This, believe it or not, is the closest living relative of the lotus. This is the London plane tree or sycamore. As you can see, this is not a little water plant, this is a big tree. ANDREW DARRAGH (Horticulturist, Kew Gardens): …driving me nuts! NARRATOR: Andy Darragh is in charge of tending to a garden at Kew that is organized by the old family tree of plants, it's called the Order Beds. He's got the somewhat overwhelming job of trying to bring order to the new order. ANDY DARRAGH: We're in this weird limbo period. I'm trying to not only do a job of gardening, mowing, edging, and weeding constantly, but I've also got to keep myself up to date. And I've also got to try and understand plant science and botany. I wish it was simpler, but it's not. NARRATOR: Perhaps the biggest surprise from the DNA evidence is that when all the number crunching was done, one plant showed up at the very bottom of the family tree of living flowering plants, Amborella, the oldest branch of the family tree—a plant so rare that it is only found in the remote Pacific island nation of New Caledonia. So is Amborella the world's oldest flowering plant? Not the fossil Archaefructus that Sun Ge discovered? Not necessarily. PETER CRANE: The molecular evidence allows us to really understand living plants in enormous detail. What it doesn't allow us to do is to account for all the diversity that's extinct. NARRATOR: Archaefructus is an example of this. We don't know where it would fit in the new molecular tree because we do not have its DNA. PETER CRANE: So we've got a difficult problem as to how to integrate these two lines of evidence. But they're both equally important in helping us to understand the complete picture. NARRATOR: Dilcher and Sun Ge are working on that complete picture. They have compared the leaves, pollen and other visible structures of Archaefructus with Amborella. Their analysis claims that Archaefructus looks more primitive and therefore evolved first. That is why they call it the oldest flowering plant, the first flower that we know of. DAVID DILCHER: I don't really know that there weren't other flowering plants living in other parts of the world, in other environments in the world. But you cannot deny the fossil record. It's there. It's hard evidence that these ancient flowering plants did exist. NARRATOR: Today Archaefructus can be seen in its proper environment, in this visiting exhibit at the California Academy of Science. Here they have a diorama that recreates life in northern China more than 100,000,000 years ago. Growing at the side of the lake is a model of Archaefructus. BOY (Looking at exhibit): It's called arby-fruitus. WOMAN (Looking at exhibit): It's one of the earliest known flowering plants. NARRATOR: By being here, it is a reminder that by giving us food and medicine, fragile flowering plants did far more to change the future of our world than any of these powerful monsters. DAVID DILCHER: The steps between the first flowers, such as Archaefructus, and the beautiful flowers in my garden are really giant steps in the evolution of flowering plants. But in my mind, I can visualize the relationship that I see in the flowers in my garden with what I find in the fossil record. NARRATOR: Meanwhile, who knows what clues to the evolution of flowers may be growing in this vast safety deposit box of plant diversity in Western China and elsewhere around the world? Or how long those clues will last? The United Nations has declared the Hengduan Mountains to be under ecological threat from growing urbanization. YIN KAIPU: Species have been disappearing fast. If we don't protect them, many will be lost. NARRATOR: Several international organizations have called for an increased effort to protect this region before its diversity is lost forever to the modern day glacier of environmental destruction. Dilcher and Sun Ge know that there are other fossils out there, that will illuminate the mystery of the first flower. They are both determined to find them. The full mystery of how flowering plants began has not been solved, but as one leading botanist says, "it is a mystery, but no longer an abominable one." On NOVA's First Flower Web site, see a slideshow of spectacular garden plants and watch video extras of 21st century plant hunter Dan Hinkley, as he explores the wilds of western China. Find it on PBS.org. To order this show or other NOVA programs, for 19.95 plus shipping and handling, call WGBH Boston Video at 1-800-255-9424. NOVA is a production of WGBH Boston. Major funding for NOVA is provided by the Howard Hughes Medical Institute, serving society through biomedical research and science education: HHMI. And by the Corporation for Public Broadcasting and by contributions to your PBS station from viewers like you. Thank you. PRODUCTION CREDITSFirst Flower Narrated by Associate Producers Edited by Camera Sound Recordists Music Composition Production Advisor, China Animation Consultant HD Designer and Animator Animation Coordinator Graphics Online
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Editors Archival Material Special Thanks For Bang Singapore Pte. Ltd. Executive Producer Executive in Charge of Production Production
Manager For Arte France Discovery and Knowledge Unit Commissioning Editor NOVA Series Graphics NOVA Theme Music Additional NOVA Theme Music Post Production Online Editor Closed Captioning NOVA Administrator Publicity Researcher Production Coordinator Unit Manager Paralegal Legal Counsel Assistant Editor Associate
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Production Post Production Supervisor Post Production Editor Post Production Manager Supervising Producer Business Manager Producers, Special Projects Coordinating Producer Senior Science Editor Senior Series Producer Managing Director Senior Executive Producer A NOVA Production by Hamilton Land & Cattle, Inc. for WGBH in association with the Media Development Authority of Singapore, Bang Singapore Pte. Ltd. and ARTE France. © 2007 WGBH Educational Foundation All rights reserved |
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