A Garden of Marvels Read online

  Nothing happened for three weeks, and while the patient remained perfectly calm, her nurse fretted daily. Then my mother called one morning to report that, just as Dr. Spann had promised, the axillary buds along the upright portions of the arched branches were opening. Dorothy, she said, was sporting pin feathers. My mother sent photos, and after a month, we agreed that it was time cut the twine and trim the upside-down branch ends. By August, when I visited again, Dorothy had regained her full plumage and even sported some purple flower buds.

  My mother continued to send photos regularly—I felt like a devoted but distant grandparent—as the tree bloomed and began to fruit. At my Christmas visit, she proudly showed me Dorothy decked out in bright yellow Meyer and green-and-yellow-striped Eureka lemons, dark green limes, two orange Cara Caras, and a single Minneola. Even if the citrus regulations change, I think Dorothy has found her permanent home.

  twenty-nine

  Afterward

  During the second half of the twentieth century, the focus of botanical research gradually shifted away from physiology and into molecular biology, which is the study of DNA, proteins, and other molecules involved in cell function. Now we are seeing a synthesis of those two disciplines, a synthesis spurred by advances in genomics (the identification and sequencing of genes) and genetic engineering. Bioengineers’ ability to transfer genes into and out of chromosomes in order to change the functionality of plant tissues and organs is opening new worlds in botany. Should we convince ourselves of the safety of genetically engineered plants or that any risks are outweighed by benefits, there will be lifesaving—and Earth-saving—opportunities in store.

  For example, more than a decade ago, Igor Potrykus and Peter Beyer, plant scientists working in Switzerland and Germany, respectively, transferred three genes—two from a daffodil and one from a bacterium—into the genome of rice. The added genes express a group of molecules that when ingested by humans becomes vitamin A. They also impart a yellow hue to the rice, giving it its popular name, “golden rice.” Golden rice has the potential to correct vitamin A deficiency, a health problem that, according to the World Health Organization, harms 250 million preschool children in developing countries and blinds as many as 500,000 each year. The rights to the rice are now held by the Golden Rice Humanitarian Board, and any farmer in a developing country who makes less than ten thousand dollars a year can, hypothetically, get free seeds. However, the high cost of meeting regulatory requirements and concerns about whether consumers in poor countries will accept a nonwhite rice means golden rice as yet grows only in test fields.

  Abscisic acid (ABA) is a phytohormone that helps plants cope with the stress of dehydration. When drought strikes, the hormone turns on receptors that cause stomata to close, and slows or stops growth so a plant needs less water. In 2009, Dr. Sean Cutler and his colleagues at the University of California, Riverside succeeded in engineering the ABA genes of Arabidopsis thaliana, another white mouse of botany labs, so that they can be turned on at will. Their work may lead to crops better able to survive and produce in regions where drought already limits—or will soon limit—harvests.

  Sixty percent of the world’s population lives in Asia, and many Asians depend on rice to survive. An average hectare of land in Asia devoted to rice, according to the International Rice Research Institute (IRRI), feeds twenty-seven people. By 2050, population growth will mean that each hectare will need to feed forty-three people. Relying on increases in rice yield to make up the difference is problematic. The annual rate of yield increases has fallen by half since the 1990s, as efficient farmers approach the fundamental limits of how much sunlight rice, which uses C3 photosynthesis, can convert to sugars. In fact, the productivity of rice plants will likely decline because the C3 pathway becomes less efficient the warmer the climate becomes.

  To raise the theoretical limit on rice productivity, IRRI scientists, funded in part by the Bill & Melinda Gates Foundation, are working to develop varieties that use the more productive C4 pathway. With traditional breeding techniques, they are trying to activate certain C4 cell structures and enzymes currently quiescent in the rice genome. Not every capability is available, however, and they may need to transfer genes from species like maize and sugarcane. IRRI estimates that a C4 rice could produce about 50 percent more carbohydrates than today’s varieties.

  Eukaryotic algae manufacture oils as well as sugars that they use to grow and function. Some algal species are theoretically capable of producing more oil than oilseed crops like sunflower and soy. That oil can be used for transportation fuel. A number of companies, including joint ventures involving major U.S. oil companies, are making progress in producing algae oil for human energy use, and a few airlines and the American military have incorporated it in jet fuel. Unlike farming corn to make ethanol, growing an algae-oil crop doesn’t use up arable land that would otherwise be used for growing food. (Even better, while growing corn requires large quantities of freshwater, many algal species thrive in brackish or salt water, of which the Earth has no shortage.) However, making the fuel at a large scale and in a profitable way is still a challenge. For one, getting the oil out of algae is surprisingly difficult and expensive.

  Perhaps a more promising path lies in genetically engineering cyanobacteria. The genomes of cyanobacteria, like that of other prokaryotes, are organized in a simple loop rather than the helices, which means it is relatively easy to add foreign DNA to their genomes. Bioengineers are genetically modifying cyanobacteria so that they produce ethanol, butanol, alkanes, and other fuels. Even better, the cyanobacteria secrete rather than store these products, so collecting them is far easier. No one has yet to prove the commercial viability of cyanobacteria fuel, but companies like Algenol and Joule Unlimited and others are betting hundreds of millions of dollars that it can be done.

  It doesn’t take such advanced techniques, fortunately, to put the science of plants to work in the garden. Those two, tree-size dracaenas I have, whose roots had snaked out of the drainage holes of the pots to circle the saucer? Once I understood that woody roots have little to do with absorbing nutrients and water, I clipped them off, and then repotted the plants in Air-Pots. A British invention, an Air-Pot looks as though it has been formed from a black plastic egg carton. On the inside of the pot are inward-pointing, closed cones. When a root touches one of these cones, its growth is directed toward a proximate, outward-facing cone. The outward-facing cones have holes, and when a root tip grows through the hole and hits the air, it desiccates and dies. This “air-pruning” kills the apical meristem of the root tip and, in a manner similar to pruning branch ends, stimulates new lateral roots to sprout. More lateral roots mean more root tips that access more water and nutrients. After I repotted my rootbound dracaenas in Air-Pots, they stopped shedding leaves, and now look healthier. Better living through plant physiology.

  I recently ordered a new kumquat tree, a Meiwa, billed as the easiest kumquat to grow and the sweetest to taste. It came, bare-rooted, from California, and I planted it in a five-gallon Air-Pot. Of course, I added mycorrhizae to the potting mixture, as well as a slow-release fertilizer with all the essential macro- and micro-nutrients. A pH meter tells me if the soil is in the range where minerals can be effectively passed by membrane transporters toward the xylem. I no longer wait for leaves to wilt as the sign for me to water. When many of the pea-sized, green kumquats drop from the tree in spring, I don’t worry: It’s just the tree balancing the energy it spends on building fruit versus its other metabolic needs. I’m quick to prune the branches (no more than a third at a time) to avoid that gangly look. I’m quicker to attack the spider mites, especially when my tree is indoors, where marauding mites are safe from natural predators. I used to think the mites were just an unsightly nuisance, but I understand now. Their thefts, unchecked, mean the tree has fewer resources to repair damaged cells or build new ones. My new kumquat is doing well, thank you, and produced dozens of kumquats last winter, just when my spirits needed a boost.

>   So, I can say that I am a better, less lethal gardener for having begun the study of botany. Now at least most of my mistakes are due to inattention, and fewer are the result of ignorance. But best of all, I have had the pleasure of an invigorating intellectual journey. I now see night-blooming jasmine in a new way: Its highly scented, white flowers are appropriate attire and perfume for a hookup with a nocturnal moth. I understand why I’ve never noticed the flowers of oak trees: Why would they spend their hard-earned savings on high fashion when no one comes to call? I’m tickled to know how pollen tubes drill through a flower’s pistil, awed by the complexity of flower color, and not surprised to find a yellow-striped bloom on my Black Velvet petunia. But the greatest marvel of the garden, I feel, lies in leaves. Gaze at a single blade of grass and you are witnessing tens of millions of microscopic green engines, capturing photons, splitting water, and manufacturing sugars with carbon snatched from air. These engines create 99 percent of the biomass on Earth; all of us oxygen-breathers constitute just 1 percent. Every day, in the improbably complex process of photosynthesis, chloroplasts turn hundreds of millions of tons of carbon dioxide into oils, carbohydrates, and, by incorporating nitrogen and sometimes sulfur, proteins. Simultaneously, they release oxygen, almost all of which is used up by respiring humans and other animals, fungi, and bacteria.

  Who hasn’t looked at the stars in the night’s black sky and been humbled by their own smallness and insignificance? But now when I look out over my leafy neighborhood from the window of my third-floor office, I think of this. There are vastly more chloroplasts on Earth than stars in the universe. All these chloroplasts owe their lives to that one eukaryote that engulfed an indigestible cyanobacterium that lived 1.6 billion years ago. That single creature’s descendants turned the rocky continents into our leafy, green world, without which none of us could exist. Our garden is more than a marvel. It’s as close to a miracle as there is on Earth.

  Acknowledgments

  I had so much help in writing this book. Thanks to all of the individuals who appear in these pages who spoke with me about the subject of their research, their hobbies, and their businesses, and gave me the benefit of their expertise. In addition, I owe thanks to Dr. Pam Soltis, Dr. William Castle, and Dr. Loren Weiseberg for their insights.

  Eva Ruhl produced these spectacular drawings with, what seemed to me, magical ease. She lives down the street, but at the opposite side of the bell curve of dexterity from where I dwell. We have had a wonderful time exploring together the way plants work and the way they look. I admire her work and her insights tremendously.

  I have had the privilege of working with Jennifer Brehl twice now, and her enthusiasm for this book has meant much to me. I am grateful to Emily Krump and Rebecca Lucash at William Morrow, and to Tom Pitoniak for copy editing. Michelle Tessler has been my stalwart advocate and an excellent advisor. I thank Dr. Thomas Colquhoun at the University of Florida for bringing his scientific eye to bear on the manuscript and Alan Bateman for help on calculations; whatever errors remain, however, are mine alone. Kenny Greif, my mentor of more than forty years, has once again given me invaluable editorial input. Ellen Roberts has given me the benefit of her highly honed editorial skills. Thanks to my mother, Alice Good, for being such a good sport about appearing in these pages, and to Jim Howard and Kate Mendeloff for their reminiscences. My daughters, Anna, Austen, and Alice, have been a great support in this long endeavor, and I couldn’t have written about Botanicalls without Danny and Rosie Edelson. Without Ted’s encouragement, this book certainly would not have been written.

  Notes and Sources

  For the history of plant physiology, Morton’s History of Botanical Science was essential reading for me, and his early chapters can be read without any knowledge of botany. Later chapters require Botany 101. Morton’s work built on Julius von Sachs’s two-volume History of Botany, but keep in mind Sachs is biased in favor of German scientists. Nature’s Second Kingdom, by Francois Delaporte, was also useful as historical background, especially on the tradition of understanding plants by analogizing from animals.

  For the basic science of plants, I relied on Linda R. Berg’s Introductory Botany, Martin Rowland’s Biology, and Peter Scott’s Physiology and Behaviour of Plants. A useful primer for botany is Brian Capon’s Botany for Gardeners. I also recommend khanacademy.org for its blackboard lectures on photosynthesis.

  PART I: INSIDE A PLANT

  The Birth and Long Life of the Vegetable Lamb

  Henry Lee’s book The Vegetable Lamb of Tartary; A Curious Fable of the Cotton Plant (1887) collects the stories about the borametz. Robert Carrubba’s article “Englebert Kaempfer and the Myth of the Scythian Lamb” is also interesting.

  Erasmus Darwin, grandfather of Charles and a poet and a botanist, wrote fancifully of the borametz in “The Botanic Garden” (1791), a two-part poem he hoped would “induce the ingenious to cultivate the knowledge of Botany”:

  E’en round the Pole the flames of love aspire,

  And the icy bosoms feel the secret fire,

  Cradled in snow, and fanned by Arctic air,

  Shines, gentle Borametz, thy golden hair;

  Rooted in earth, each cloven foot descends,

  And round and round her flexile neck she bends,

  Crops the grey coral moss, and hoary thyme,

  Or laps with rosy tongue the melting rime;

  Eyes with mute tenderness her distant dam,

  And seems to bleat—a “vegetable lamb.”

  Darwin wrote a note on this stanza:

  Polypodium Barometz. . . . This species of Fern is a native of China, with a decumbent root, thick, and every where covered with the most soft and dense wool, intensely yellow. . . . This curious stem is sometimes pushed out of the ground in its horizontal situation by some of the inferior branches of the root, so as to give it some resemblance to a Lamb standing on four legs. . . . The down is used in India externally for stopping hemorrhages, and is called golden moss.

  Despite the fact that England was importing huge quantities of raw Indian cotton for its textile industry, he failed to connect the borametz to Gossypium and the fluffy fibers that surround the seeds and help disperse them.

  Through a Glass, However Darkly

  Although Robert Hooke was not much interested in exploring the inner structure of plants, he was curious about what makes the nettle sting. He saw “sharp needles,” which he found “by many tryals” to be “hollow from top to bottom.” By putting a magnifying glass in a frame and attaching it to earpieces, he made magnifying eyeglasses and freed his hands to manipulate the nettle. Pushing one of its needles into his skin, he observed that his action caused the bottom of the needle to depress a small bag at its base. A fluid flowed out of the bag, up through the needle, and into his skin, and he correctly concluded that it is the fluid, not the prick, that causes the sting. We now know that the liquid contains a mix of neurotransmitters, including acetylcholine and histamines.

  Hooke experimented on his own body in search of substances that would allow him a clearer, less depressed, more imaginative mind to handle all the work he had taken on. He systematically and almost daily swallowed substances, most of which we now know to be toxins, and noted their effects in his diary. Iron compounds, ammonium chloride, antimony, absinthe (which is made from various Artemisia species), and other “remedies” went down his throat at night, often on a tide of small beer or ale. Not surprisingly, he often vomited, had horrendous diarrhea, suffered cloudy vision, felt lightheaded and feverish, and had numb extremities, but often also reported that he felt “refresht” or “strangely refresht” in the morning. As his body acclimated to the poisons, he needed to take larger doses to achieve an elevated mental state.

  Hooke became involved in many rancorous disputes with his colleagues over who ought to get credit for inventions and discoveries. Most notably, he argued with Isaac Newton over who first expressed the theory of universal gravitation and elliptical orbits, and with Christia
n Huygens over the invention of the spring-regulated watch. (Good, but not definitive, arguments can be made for Hooke.) He had a rich social life into middle age, visiting and dining with friends and colleagues in their homes and coffeehouses and taverns. He had sexual relationships with several of his servants and his niece, but never married. In his later years, he alienated many of his former friends and colleagues, and it may well be, as Lisa Jardine suggests in The Curious Life of Robert Hooke: The Man Who Measured London, that the toxins to which he became addicted heightened his anxieties, his irritability, and his fears of being slighted. His emotional and physical suffering, as well as his self-medication experiments, no doubt hastened his death in 1703.

  It is well worth looking at a copy of Micrographia. Not only are the drawings beautiful, but Hooke’s text is quite readable and revealing of his searching mind. Bradbury provides the basic history of the microscope in The Evolution of the Microscope. He also passes along Henry Power’s 1664 poem, “In commendation of Ye Microscope,” which captures the self-consciousness of the early Enlightenment philosophers and their awe:

  Of all the Invention none there is Surpasses

  The Noble Florentine’s Dioptrick Glasses

  For what a better, fitter guift Could bee

  In this World’s Aged Luciosity.

  To help our Blindnesse so as to devize

  A paire of new & Artificial eyes

  By whose augmenting power wee now see more

  Than all the world Has ever doun Before.