The Big Bloom—How Flowering Plants Changed the World

 

In 1973, sunflowers grew in my father's vegetable garden. They appeared to sprout spontaneously in a few rows he'd lent to new California neighbors that year. At the moment, just six years old, these garish plants first set me off. Such odd and colorful flowers seemed out of place amid the respectable beans, peppers, spinach, and other vegetables that we've all grown. Yet eventually, sunflowers' beauty won me over. Their fiery halos relieved the lush monotonous garden dominated by late summer. I marveled at birds clinging to shaggy, gold balls, wings fluttering, seed plundering. That summer, Sunflowers identified flowers for me and changed my outlook.

Flowers have a way to do so. They started transforming the way the planet looked nearly as soon as they arrived on Earth about 130 million years ago, during the Cretaceous period. That's comparatively recent in geological time: if all Earth's past were squeezed into an hour, just the last 90 seconds would be flowering plants. But once they took firm root about 100 million years ago, they soon diversified into an abundance of varieties that formed much of modern-day flowering plant families.

Today flowering plant species outnumber twenty to one of ferns and cone-bearing trees or conifers that thrived 200 million years before the first bloom appeared. As a food source, flowering plants provide the nourishment essential to our life to us and the rest of the animal world. In Walter Judd's words, a botanist at Florida University, if not for flowering plants, we humans wouldn't be here.

From oaks and palms to wildflowers and water lilies, to miles of cornfields and citrus orchards to the garden of my aunt, flowering plants have come to dominate the worlds of botany and agriculture. They often rule over an ethereal world pursued by writers, poets, and ordinary people finding inspiration, warmth, or the basic joy of seeing a flower.

Before flowering plants emerged, says Dale Russell, a paleontologist with North Carolina State University and the State Museum of Natural Sciences, the world was like a Japanese garden: populated by birds, tortoises, and dragonflies. The planet looked like an English garden after flowering plants, full of color and abundance, visited by butterflies and honeybees. Flowers of all sizes flourished amid the greenery.

The seismic transition marks one of the planet's biggest moments in human history. What made flowering plants rule the world's flora so fast? What's been their big innovation?

Botanists call angiosperms from the Greek terms for vessel and seed. Unlike conifers in open cones, angiosperms enclose their seeds in berries. Each fruit contains one or more carpels, hollow chambers that cover the seeds. Break a tomato in half, for example, and find carpels. These mechanisms are the distinguishing characteristic of all angiosperms and a key to the success of this vast plant community, which numbers 235,000 species.

Only when did the first flowering plants emerge? Charles Darwin pondered the question, and paleobotanists are still finding answers. Discoveries of fossilized flowers in Asia, Australia, Europe, and North America provided valuable hints in the 1990s. Simultaneously, the genetics field introduced a whole new range of methods to scan. Modern paleobotany has experienced a surge, not unlike the Cretaceous flower eruption itself.

Old-style fossil hunters now compare observations with shovels and microscopes using genetic analysis to map current plant families back to their origins. These two researchers groups don't often arrive at the same birthplace, but both camps agree on why the pursuit is significant.

If we have a clear description of a flowering plant's nature, says Walter Judd, so we will know information about its form and function that will help us address any questions: with what species can it be crossed? What pollinators are effective? This, he claims, moves us towards increasingly sensitive and efficient farming methods, as well as a clearer understanding of the broader evolutionary process.

In recent years, Elizabeth Zimmer, a molecular biologist with the Smithsonian Institution, rethought the process. Zimmer tried to decode the genealogy of flowering plants by analyzing today's species' DNA. Her work intensified in the late 1990s during Deep Green, a federally funded project, designed to promote collaboration among scientists researching plant evolution.

In their pooled results, Zimmer and her colleagues started searching for classes of plants with similar inherited characteristics, aiming finally to find a common ancestor for all flowering plants. Amborellaceae, a genus that comprises only one recognized member, Amborella trichopoda, is the longest living lineage, stretching back at least 130 million years. Sometimes described as a living fossil, this small woody plant grows only in New Caledonia, an island known by botanists for its primeval flora.

But we don't have a 130 million-year-old Amborella, so we can only imagine if it looks like the range of today. We have fossils from various extinct tropical species, the oldest found in 130 million-year-old sediments. These fossils send us our first visible impressions of what looked like early flowers, indicating they were small and unadorned, without petals. These no-frill flowers contradict certain conceptions of what constitutes a flower.

To see what the first primitive angiosperm would look like, I flew to England and met paleobotanist Chris Hill, formerly at London's Natural History Museum. Hill drove me south of London through rolling fields to Smokejacks Brickworks. Smokejacks is a hundred-foot-deep (30-meter-deep) crater in the earth, as wide as many football fields, providing much more than brick raw material. The rust-colored clays contained thousands of fossils from 130 million years ago. We marched down the canyon, got down on our hands and knees, and started digging.

Soon Hill raised some mudstone. He explained it to me, pointing to an illustration of a tiny stem ending in a primitive flower. The fossil resembled a single broccoli-picked sprout. The first flower in the world? More like a flower concept said Hill, who discovered his original fossil in the early 1990s. He formally called it Bevhalstia Abuja, terms paved from his closest colleagues' names.

Via my glass, the Bevhalstia fossil looked tiny and straggly, an unremarkable plant I could see emerging in the water at the edge of a pond where Hill claims it has grown.

Here's why I think it's a wild flowering herb, Hill said. Bevhalstia is distinct and unassigned to any existing plant family. So we start by comparing it to what we know. Any modern aquatic plants' stems follow the same branching patterns as Bevhalstia and grow tiny flower buds at certain branch ends. Bevhalstia also bears a striking similarity to a fossil described by paleobotanists Leo Hickey and Dave Taylor in 1990. The fossil, Australia's diminutive 120 million-year-old herb, grew leaves that are neither fernlike nor needlelike. Instead, they are inlaid with veins like typical flowering plant stems.

More specifically, the specimen of Hickey and Taylor contains fossilized fruits that once contained seeds, which Hill hopes to find in Bevhalstia. Both plants lack established petals. Both are more common than the magnolia, recently disassembled as the oldest tree, though still considered an ancient legacy. And both, along with a recent discovery from China called Archaefructus, backed the theory that the very first flowering plants were plain and unobtrusive.

As other explorers, early angiosperms were overlooked. In a landscape dominated by conifers and ferns, these botanical pioneers succeeded in obtaining a toehold in places of natural disruption, such as floodplains and volcanic zones, adapting rapidly to new conditions. Fossil data leads some botanists to conclude the first flowering plants were herbaceous, suggesting no woody sections grew. (New genetic analysis reveals, however, that most ancient angiosperm lines included both herbaceous and woody plants.) Unlike trees that take years to mature and bear seed, herbaceous angiosperms survive, reproduce, and die in brief life cycles. This helps them to easily seed new land and maybe encourage them to grow quicker than their rivals, advantages that could have improved their diversity.

Although this so-called herbaceous habit may have given them superiority over slow-growing woody plants, the trump card of angiosperms was the flower. A flower is essentially an angiosperm's reproduction system. Both flowers are male and female. Reproduction starts as a flower sheds microscopic genetic material pollen into the air. These grains finally come to rest on another flower's stigma, a tiny pollen receptor. In most instances, the stigma sits atop a stalk-like structure called a style protruding from a flower's middle. The pollen kernel, moisturized, activates proteins that chemically determine whether the new plant is genetically compatible. If so, the pollen grain will germinate and develop a tube down the style and ovary into the ovule where fertilization occurs and seed starts to form.

Wind casting pollen is a hit-or-miss reproductive method. While wind pollination suffices for many plant species, direct insect distribution is much more effective. Undoubtedly, insects started to visit and pollinate angiosperms until new plants appeared on Earth around 130 million years ago. But it will be another 30 to 40 million years before flowering plants attracted insect pollinators' interest by flaunting dazzling petals.

Petals have formed between 90 and 100 million years ago, said Else Marie Friis, head of paleobotany at the Swedish Natural History Museum outside Stockholm. And then, very, very little.

A knowledgeable woman with short brown hair and intense eyes, Friis maintains what many experts say is the most complete collection of fossils found in one location. The delicate flowers survived death, strangely enough, due to the heat of long-ago forest fires that burned them into charcoal.

Friis gave me an 80-million-year-old fossil flower no larger than at the end of this section. Coated in pure gold for optimum detail under an electron microscope, it barely seemed a flower. Many researchers ignored these small, simple flowers, she said, because without the microscope you can't understand their variety.

So we squatted through her strong magnifier and walked figuratively through a cretaceous world of small, colourful angiosperms. Friis' fossilized flowers multiplied hundreds or thousands of times, resemble wrinkled onion bulbs or radishes. Many have clamped their tiny petals, sealing carpels within. Others reach full maturity wide open. Dense bunches of pollen grains cling in gnarled clumps.

Between 70 and 100 million years ago, the number of flowering plant species on Earth erupted, a phenomenon botanists call it the great radiation. The spark igniting the eruption, Friis said, was the petal.

Petals provided more variety. This is now commonly known, Friis said. Once ignored angiosperms were standouts in the field, luring insect pollinators like never before. Reproduction actually began.

Insect-flowering activity influenced the growth of both species, a phenomenon called coevolution. In time, flowers developed arresting patterns, seducing fragrances, and distinctive petals to provide insect pollinators with landing pads. Nutritious fluid flowers have nectar as a form of trade product in return for pollen dispersal in the insect benefit package. Bees, butterflies, and wasps' ancestors became dependent on nectar, and thus become agents of pollen delivery, unwittingly bearing grains hitched on their bodies to tiny hairs. These insects may capture and transfer pollen to new flowers with each visit, enhancing fertilization chances.

Insects were not the only compelled animals to help move flowering plants to any corner of Earth. Dinosaurs, the world's first movers and shakers, bulldozed into ancient trees, unintentionally destroying fertile angiosperm land. They also sowed seeds around land through their digestive tracts.

By the time the first flowering plant emerged, plant-eating dinosaurs had been around for a million years, feeding on a diet of ferns, conifers, and other primordial plants throughout. Dinosaurs lasted for 65 million years and some scientists believe the giant reptiles had plenty of time to adapt to a new diet that included angiosperms.

Just before dinosaurs died, I believe lots of them were chowing down on flowering plants, says Kirk Johnson of Nature & Science Museum Denver. Johnson has discovered several fossils aged 60 to 70 million from locations throughout the Rocky Mountain region. He deduces from them that hadrosaurs or duck-billed dinosaurs lived on large angiosperm leaves that had formed in a warm climatic change just before the Cretaceous period ended. Referring to sediments that only predate dinosaur extinction, he said, I just find a few hundred samples of non-flowering plants there, but I collected 35,000 angiosperm specimens. No way the dinosaurs ate these things.

Early angiosperms were low-growing, which better matched some dinosaurs than others. Brachiosaurs had long necks like giraffes, so they were poorly equipped to eat new vegetation, says Richard Cifelli, University of Oklahoma paleontologist. However, ceratopsians and duck-billed dinosaurs were true mowing devices. Behind those mowers, angiosperms adapted for freshly cutting ground and spreading.

Dinosaurs abruptly died around 65 million years ago, and another group of species took their place — the mammals, which greatly benefited from the variety of angiosperm foods, including seeds, nuts, and many vegetables. Flowering seeds, in particular, benefited from mammals' seed dispersal.

Two kingdoms made a handshake, says David Dilcher, a paleobotanist with Natural History Museum of Florida. I'll feed you and take my genetic material out.

 

Eventually, mankind changed, and the two realms made another handshake. Angiosperms fulfilled our need for food by cultivation. In turn, we took certain species like corn and rice and gave them unprecedented success, cultivating them in vast fields, deliberately pollinating them, gusto consuming them. Virtually all non-meat food we consume begins as a flowering plant, while the foods, milk, and eggs we consume come from grain-fattened animals — flowers. And wearing cotton is angiosperm.

And aesthetically, angiosperms protect and enrich our lives. On Valentine's Day, we've come to admire them for their beauty, their scents, their companionship in a vase, a plant. Some flowers speak an ancient language of short phrases. For these more sparkling players — orchids, roses, lilies — the universe grows smaller, crisscrossed every day by jet-setting flowers in the cargo holds of commercial aircraft.

We aim to supply flowers anywhere in the world within 24 hours of being picked, said Jan Lanning, a senior consultant with the Dutch Wholesale Commission, the world's ornamental flowers turnstile. The company also globalized.

On my way home from Friis's Swedish school, I stopped in the Netherlands, the world's largest exporter of cut flowers. I asked Lanning to try to describe his chosen job. He leaned with a ready response.

 

Flowers intrigued us as long as we lived. That's an emotional commodity. Living objects draw people. Smell, light, charm all in a flower. He grinned at his desk's fragrant lily design. Per Monday a florist brings this office fresh flowers. It's the luxury required.

Later that day, I spied a group of admirers crowded before a painting in Amsterdam's Van Gogh Museum. I went there and pressed in among them. Suddenly I saw Sunflowers, one of van Gogh's most famous works. The flowers hang out of a vase, muddy and disheveled. They took me to my barefoot youth at the edge of my dad's garden on a wet summer evening alive with fireflies and cicadas murmur.

The audience went on, with Sunflowers left. My search came to this surprising end, the first flower I can recall. Would van Gogh raise the flower to an art form, or would van Gogh's flower harness imagination immortalize itself in oils and brushstrokes? Flowering plants occupied more than land. They have profoundly rooted our minds and souls. We know we 're walking into their world like a museum, and they've been here long before we've come and maybe stay long after we've left.