A Garden of Marvels Page 12
We sidestep a few steps farther down the row as David looks for another plant to show me.
“Now take a look at this one. It’s a lot closer to its wheatgrass parent.” When he pulls this flower stalk toward me, I see that its seeds are arranged, not in a dense, three-inch crescent, but stretched out along the top twelve or so inches of a stalk. The seeds are obviously smaller, too, more like sesame seeds.
On the left, seedheads of wild perennial wheatgrass; on the right, seedheads of domesticated annual winter wheat.
“These seeds are a problem because there’s less edible germ and more inedible hull in each one. Another problem is that when they mature, they probably won’t ripen all at once, and when they do, they’ll drop to the ground right away. It’s what we call shattering. From the farmer’s point of view, this is no good at all. He wants to harvest once and capture all the ripe seeds that one time. The ideal seedhead—again, from a farmer’s point of view—is the modern ear of corn. Its seeds always ripen at once and they never fall off.”
While a habit of shattering is bad for farmers, it’s a competitive advantage in the wild. The prairie landscape is dense with perennials; normally, every fertile spot is taken. When the rare vacancy occurs—maybe a tunneling gopher destroys a plant or a herd of bison tramples down a swath of grass—a plant with a shattering seedhead is more likely to have some ripe seeds ready to seize the moment. The smaller size of a perennial’s seeds is also the result of evolutionary selection. Perennials divide their energy and carbon between building the roots that are the source for sending up new stalks in the spring and seeds that might populate a bare spot should one happen to open up. So, perennial plants generally produce shattering seedheads with small seeds. Annuals, whose only hope for survival lies in their seeds, produce big seeds packed with nutritious endosperm.
Crossbreeding is one way to try to perennialize an annual. The other way is to select and propagate the most desirable of the wild perennials, then choose the most desirable among those to propagate, select among the second generation, propagate again, and so on. The Institute’s scientists are pursuing both methods simultaneously. I was thinking that a little gene splicing could make quick work of the problem. But there is no single gene for perenniality, David tells me, any more than there is a single gene for flight in birds. Perenniality involves a complex suite of attributes. You would have to identify and manipulate untold numbers of genes that control for seed size and ripening timing, root growth, seedcoat thickness, and allocation of carbohydrates between roots, shoots, and seeds. Genes for stalks would have to be manipulated, too, for the sake of a mechanical harvester. Wheatgrass stalks are naturally tall, thin, and variable in height. To be fit for the farm field, they must become shorter, stiffer, and more uniform. Old-fashioned breeding techniques are more likely to do the job.
The seeds of wheat, rye, oats, sorghum, barley, and other grass plants store energy in the form of carbohydrates, carbohydrates we snatch and turn into breakfast cereals, bread, and beer before the plants’ embryos and seedlings can use them. The seeds of other plants, like rapeseed and sunflower, fuel their embryos with energy stored primarily as oils. Oilseeds are critical to human health because they contain omega fatty acids that we need for proper metabolism but our bodies cannot manufacture. We have also come to value the oil as a cooking medium: Not only does it impart taste, it transfers heat efficiently. The sunflower (Helianthus), which produces an oil particularly low in saturated fat, is the chief focus of David’s research, and we wend our way to the far end of the greenhouse to see what he has growing.
I find sunflowers creepy. From time to time, Ted grows one in his postage-stamp vegetable garden. With its man-sized head, large and prickly leaves, and a towering stalk that seems too weak to support its heavy flower, the mature plant looks like a freak of nature. (The flower is not one bloom, but rather is made of hundreds of its tiny “disk florets” encircled at the perimeter by far larger, single-petaled “ray flowers.”) At the height of summer, I admit, a sunflower in bloom is a striking sight, the bright yellow petals rimming a burnished, golden disk. By late summer, though, the florets have turned to black seeds and the ray flowers are withered. From our back windows, the flower looks like a dark, protuberant eye rimmed by lashes staring blindly at the house all day. It disturbs me to see birds fly in to peck at its undefended oculus.
I am gratified, therefore, to learn from David that the annual garden sunflower is a freak, not of nature but of man. In the wild, most sunflower species look more like daisies and other charming members of the aster family. The flower’s disk is a modest inch, rather than twelve inches, in diameter. If a wild sunflower finds itself in a good patch of sun-drenched soil, it will branch prolifically, becoming a head-high shrub sporting many dozens or even hundreds of small flowers. One well-situated wild sunflower plant can produce tens of thousands of seeds.
On the left, a wild sunflower; on the right, a domesticated sunflower.
Helianthus evolved in the American Southwest, and later spread across the American plains, courtesy of the great herds of bison. Their matted coats snagged the little hairs at the ends of ripe sunflower seeds and carried them away. When the seeds dropped off, they fell on ground that their chauffeurs had tilled with their hooves as they passed through the high grasses. In a matter of weeks, stems and leaves would rise out of the trampled earth. It was as if the bison left a trail of sunflowers, like bubbles in the wake of a boat. Some ten thousand years ago, Native American tribes began migrating across those same lands, along the bison trails, and gathered the ripe seedheads. The seeds could be hulled and ground into flour or mixed with berries, meat, and fat into a sort of energy bar called pemmican. The hulls, brewed in hot water, made a gorgeous purple dye.
The gatherers inadvertently began to domesticate Helianthus long before anyone deliberately planted it. Picture a midwestern landscape four thousand years ago, lush with wild grasses and wildflowers. A tribe has set up a seasonal camp, and a woman sets off for an afternoon of collecting sunflower seedheads. She has noticed that there are patches of sunflower plants that have somewhat larger heads and seeds, some up to twice the size of others, so she favors those, although there are far fewer of them. Any seedheads that have already dropped a good portion of their seeds or that are still partially in flower, she ignores. She may simply pull the seedheads off or perhaps she cuts them off with a stone blade. Then she drops them in the basket she carries in her hand; when it’s full, she empties it into the much larger basket hanging on her back from a strap across her forehead.
Those attractive patches of Helianthus, the ones with the big flowers and seeds, are annual species. Annuals represent only 10 percent of sunflower species. They pour their energy into reproduction like there’s no tomorrow because, in fact, there is no tomorrow. The only future annuals have is in their offspring. So they rocket their shoots and leaves skyward, make minimal investment in roots, get to reproduction as fast as possible, and channel their energy into lots of large seeds. Naturally, these are the species that draw the eyes of our human seed collector, although she undoubtedly collects perennials’ seeds as well. Back at the camp, she harvests the seeds and tosses the (mostly) empty seedheads onto the camp’s trash heap.
The next year, a few sunflower plants—“volunteers”—spring up on the trash heap or where a gatherer dropped a few seeds elsewhere in camp. The volunteers are more likely to be annual species, both because the gatherers favored them and because annuals flourish in such open, disturbed ground. The trash heap plants tend to have nonshattering seeds because they descended from parents that were harvested for that attribute. Over time, a convenient patch of annuals, cross-pollinated by insects that have visited their similar neighbors, persists.
In the wild, annual patches are crowded out over time by perennial species. Perennials are slower off the mark in the first year or two, but once established, in the spring they send up new shoots from their roots faster than annual seeds can germinate,
and after several seasons shade out the annuals. In the wild, perennials ultimately win the race, which is why 90 percent of Helianthus species are perennials.
Why the first hunter-gatherers bothered to deliberately plant sunflower seeds when they were available in the wild is a matter of debate. Did a tribe move to an area where no convenient patches of the annuals grew? Lazy soul that I am, I think someone simply appreciated the convenience of the camp patch, and sowed some saved seeds or expanded the local patch of volunteers. In any case, roughly four thousand years ago, the sunflower was domesticated somewhere in the region of southern Iowa and western Tennessee.
When it came time for planting each spring, the neophyte farmers naturally selected the biggest of their big seeds to sow. In choosing the biggest seeds, they inadvertently chose other plant traits. The biggest seeds often came from individuals whose genes had directed them to grow fewer branches and devote more energy, therefore, into fewer flower heads. The plants with fewer flower heads had more energy to put into producing bigger seeds. By repeatedly choosing to plant the largest seeds of the fall harvest, Native Americans gradually developed a minimally branching plant with foot-wide flower disks that have large, nonshattering seeds.
The question at the Land Institute is whether modern breeders can go back to the beginning and start the process of domestication over. David is crossing wild perennials and domestic annuals in the greenhouse, but he is particularly enthusiastic about domesticating a wild perennial called Helianthus maximiliani. The maximiliani branches luxuriantly in nature and sports multitudes of small flowers that shatter freely. After only four seasons of selective breeding, David’s maximiliani have already developed a nonshattering trait. He shows me two plants that also have a single, unbranched stalk and a head about twice the size of a wild maximiliani head. He isn’t sure, though, that ultimately a domesticated perennial will have a single head. When farmers harvested by hand, a single huge flower made harvesting easier, but today’s mechanical harvesters don’t care whether they strip one head or a hundred heads off a plant. Besides, there is a downside to the giant heads: They make great perches for marauding birds. In commercial fields along migratory bird routes, farmers can lose up to 40 percent of their sunflower crop.
“I believe,” David says, “domestication is going to be easier than people think. People assume that because it took place thousands of years ago that it took thousands of years, but we don’t actually know how long it took. Now that we know how plants work, about sexual reproduction, about genes, and have sophisticated breeding techniques, we should be able to do it a lot faster than the people who did it accidentally. Now that we have people devoting their whole lives to domesticating these plants, I’m betting it will happen a lot faster.”
Still, the breeders here talk in terms of twenty-five to fifty years. So far, the best of the Institute’s perennial wheat produces about three hundred pounds of grain per acre, a trifling amount for Kansas farmers who currently harvest more than two thousand pounds per acre. David points out, however, that a perennial wheat crop needn’t be quite as productive as the annual it replaces in order to be profitable. Perennial farmers won’t have to buy new seed and will spend less on fertilizer, machinery fuel, and irrigation. Still, he and his colleagues have a long way to go. And it is no sure thing. Skeptics believe that creating perennials with big, calorie-rich seeds may be like having your cake and eating it, too, a logical impossibility. In nature, they argue, species make a trade-off between living a long life and producing many offspring: With the same amount of sunshine-generated carbon, species “choose” between investing it in big perennial root systems or big seeds.
It may be, however, that Land Institute scientists manage to shift that carbon allocation, creating a variety that puts just enough energy into roots to survive the next year while channeling substantial energy into creating seeds that are nearly the size of annuals’. Or, there may be carbon savings to be found elsewhere in a plant, say, in stem height. Wild grasses, having evolved in prairies under natural selection, developed tall stems to beat their neighbors to the sun and avoid being shaded. If breeders select for perennial wheat that is shorter, will they be able to breed plants that redirect that carbon into seed production? David acknowledges that he and his colleagues are taking a gamble. But if they succeed, they will not only revolutionize agriculture but also change the future of our planet.
thirteen
Off to the Races
Let’s say you start a giant pumpkin in your backyard in the spring. Throughout the summer, you tend your patch assiduously, burying the vines’ axils, fortifying the soil, and drenching it with warm water. Now it’s the end of the season and your pumpkin has reached her voluptuous maturity, and you’ve got somewhere between four hundred and twelve hundred pounds of pulchritudinous orange gourd. She’s big all right, but probably not big enough to win any prize money at a regional weigh-off. However, if you happen to live near Damariscotta, Maine, a coastal village an hour north of Portland, you’re in luck. You have an opportunity for fame, if not fortune. Saw off the top of your pumpkin, scoop out the innards, and get you and your mama down to the harbor to the Giant Pumpkin Regatta.
This is where Ted and I are at eight o’clock on a Sunday morning, a morning as fine as Maine can manufacture in mid-October. The sky is a kindergartner’s vision of blue, the temperature is pushing seventy, and the glassy water of the harbor doubles the hulls of colorful skiffs at anchor. We arrived early to find a spot along the riprap where, I was forewarned, a crowd of hundreds would gather. To my right is the town boat ramp, where a shiny green John Deere tractor is grinding its way down to the water’s edge with a giant-pumpkin boat strapped to its front forklift. This pumpkin has been painted a pale gray with a grinning mouth full of big white teeth on its front end. On its back end is a perky Styrofoam whale tail. Standing in the water is a member of the town’s fire department, a well-fed fellow wearing a red drysuit. When the whale floats free of the forklift, he swims it over to the narrow floating dock. There, its owner, a man in a baseball cap, reclaims it.
The whale has company. To its left is a pink pig with a pink bucket for a snout, googly plywood eyes and upright ears, and a curlicue wire tail. Bobbing gently on the right is a pumpkin peacock with a towering Styrofoam head and arcing tail feathers made of blue, pink, and green swimming pool noodles. The whale’s owner jackknifes himself into his craft, takes up a double-bladed kayak paddle, and sets out for a test drive. When he returns, he starts hacking off pieces from the rim of the cockpit. Meanwhile, some official is shouting that everyone who is not a participant in the race has got to get off the “dawk,” which, he correctly points out, is sinking under their weight.
By nine thirty, hundreds of people have indeed gathered on the shore, and an unseen announcer asks us for silence. Hands over hearts, we sing the national anthem. On a yacht at the far end of the dock an American flag is hoisted by members of a Boy Scout troop. Three Marines in crisp blue pants, dark jackets, white belts, and white caps stand at attention as the flag goes up. A minister blesses the pumpkin growers and carvers, the sailors, the festival organizers, the observers, and the Damariscotta fire department. Then, we’re off to the races.
There are two classes of pumpkin boats in the regatta: paddle-powered and motor-driven. First up are the paddlers. I see that the two smallest craft—the pink pig, which is captained by a tanned young woman wearing a pink ball gown and an orange beanie, and a pumpkin painted to resemble a pink-and-white-striped hard candy—ride lower in the water than the others. There’s a bit of jockeying before the start. A particularly plump pumpkin, one that looks like an orange washtub, is drifting away from the dock, and its captain can’t seem to paddle in reverse to return to the starting line. Suddenly, despite the washtub’s two-yard lead, the race begins.
The whale quickly passes the washtub, which doesn’t go forward well, either. The pig is in hot pursuit. The Maine Maritime Museum’s entry, “Smash,” a pumpkin compl
etely hidden by a two-masted, yellow-hulled brigantine complete with flapping sails and an American flag, can’t get away from the dock at all. The candy and the peacock are struggling. (The peacock’s majestic neck prevents the paddler from reaching far enough forward to get a good purchase on the water.) Seventy-five yards into the race, as the boats round the buoy to head home, things get messy. It seems there is no protocol for the turn: Some boats go to the starboard side, others to port, and then the buoy drifts, and there is a general mash-up as a result. The captain of the candy, the only one who executes a quick, neat turn, emerges first from the pack and moves instantly from fourth place to first. The peacock, whose head is loose and swings drunkenly at each stroke, falls to the rear. The candy sprints for home, but is beat out by the whale by a length. The crowd cheers, and I can hardly aim my camera for laughing.
In the second heat, the pig starts taking on water, which, someone with binoculars tells me, is entering through the base of its tail. A little girl behind me gasps, “The princess is swimming!” and indeed she is, dog-paddling away from the swamped pig. Not to worry, though. Two frogmen escort her to shore and push the pig back to the boat ramp. I am soon distracted from this drama, though, by events on, or rather under, the brigantine. This time, the ship did leave the dock, powered with two oars by a young woman dressed in period costume, but she is still on the outgoing leg while the others are on the incoming. Despite the captain’s ardent rowing, her ship is faltering and seems to be settling in the water. Suddenly, an orange blob arises from the deep, next to the ship and just beneath the surface. It is the brigantine’s pumpkin, which has parted company with the superstructure. Once again, the intrepid frogmen swim to the rescue. Meanwhile, the peacock—which, mercifully, has been decapitated between heats—is making a strong showing, but the whale wins again.