Plants: Food, Medicine, and the Green Earth

The Father of Botany

Natural history is the study of plants and animals, with the emphasis on observation rather than experiment. People have always made use of plants, of course, but as means to an end, a resource to be utilized. They gathered plants for food and medicines and later they cultivated them; they constructed their buildings, boats, and many tools and utensils from plant materials; and they wove cotton, linen, hemp, and jute to make cloth. Once writing was invented, people made paper from papyrus (a type of sedge), hemp, and cotton, before turning to wood pulp in modern times; all of these are plant products. Communities had been doing these things for thousands upon thousands of years, but people gathering or cultivating plants and craftspersons converting plant materials into useful articles had no need to understand any more about the plants they used than their properties and how to exploit them.

It was not until the cultural flowering in ancient Greece that scholars began to speculate about the origins of plants, to investigate their growth and structure, and to attempt to catalog the many different kinds of plants. That was the beginning of natural history, and in later centuries it led to the study of botany and eventually to the modern scientific disciplines that are grouped together as the life sciences. This chapter tells of the beginnings of natural history. The story starts in Greece, moves to Rome, and finally arrives in England, where it describes one of the first serious attempts to list every type of plant in the world.

Herbals and Physic Gardens

It was during the course of the 20th century that the expansion of the pharmaceutical industry supplied physicians with factorymade drugs to treat specified illnesses. Until that time remedies had been based either on therapeutic substances obtained almost entirely from plants—although a few remedies were obtained from minerals or animals—or on interventions such as bleeding, applying leeches, sweating, and purging that were more likely to injure the patient than effect a cure. With the rise of modern medicine, the older interventions fell into disuse, and the use of herbal preparations became increasingly marginalized until they disappeared from official medicinal practice, although medical herbalism continued to thrive informally.

Since plants with therapeutic properties were so important, it is hardly surprising that physicians were required to study botany as part of their training and that close to medical schools there were gardens growing medicinal plants. The art of healing was once called physic, which is why medical doctors are called physicians, and the gardens were known as physic gardens. Such gardens were cultivated in most parts of the world, and, although many became neglected when the medical need for them disappeared, in recent years interest in them has revived and new ones are being planted, although for educational rather than medical uses. In 1965 the Royal College of Physicians in London established a new physic garden. Perhaps the most famous surviving physic garden is at Chelsea, London.

This chapter describes some of the most important physic gardens and also developments in the identification and description of medicinal herbs. Before a gardener can begin cultivating herbs there must be a catalog of those the physic garden should contain. A list of such plants is called a herbal.

The story begins in ancient China with the emperor Shennong. It visits Aztec Mexico and the gardens of Europe, and it ends with an explanation of one of the more curious aspects of the theory of herbalism.

Botanical Gardens and Herbaria

Physic gardens grew medicinal plants and as well as supplying the plants they were used to teach botany to apothecaries and physicians. In time botanists came to appreciate the value of growing collections of nonmedicinal plants as well. Plants were arriving in Europe from the New World, Africa, and Asia that European botanists had never seen before. By the middle of the 16th century, physic gardens were expanding to become botanical gardens and, in parallel with that development, lists of useful herbs were becoming lists of all the plants found in a particular area. This chapter traces those changes.

The chapter begins by explaining how the study of herbs expanded to become the study of all plants. It tells of the establishment of botanical gardens and the assembling of the world’s great botanical collections. It was not possible to cultivate every plant species, but it was possible to preserve plants in other ways, and the chapter outlines the rise of the herbarium. Private ornamental gardens were also becoming fashionable, and the chapter describes that development and what it aimed to achieve.

Naming Plants

A plant that grows naturally across a wide geographical region has a name in each of the languages of that region. In many countries it is likely to have more than one local name, and the same name may refer to different plants in different places. Viper’s bugloss, for instance, is known as blueweed in some places. Jewelweed is also called balsam and touch-me-not, but there are about 20 plants with balsam in their names, including balsam apple, balsam bog, Canada balsam, Copaiba balsam, balsam fig, balsam fir, gurjun balsam, Indian balsam, Mecca balsam, balsam of Peru, and Tolu balsam—and they are all different. Cowslip refers to different, unrelated plants in Britain, North America (where there are 14), and South Africa.

Plant names are confusing, and this chapter recounts the story of how the confusion was finally resolved. Today, a botanist in one part of the world is able to discuss any plant with a botanist in a distant country who speaks a different language, and there is no risk of ambiguity because all botanists agree to give each plant its own unique name. For example, Mecca balsam is Commiphora opobalsamum and the 14 North American cowslips are 13 species of Dodecatheon, also called shooting star, and Virginian cowslip is Mertensia virginica, also known as Virginian bluebells. Local names survive, and long may they continue to do so, but botanists have no need or use for them.

Agreeing on a single system for naming plants also involved agreeing on a system for classifying them, and this chapter explains how that system came into being and how it works. Many naturalists had attempted to classify plants, but this chapter confines itself to describing the development of the system that is used today. It ends by telling of the birth of a new branch of the plant sciences: plant geography.

The Plant Hunters

Although most of them traveled extensively, the great botanists such as Linnaeus, Tournefort, and Engler could not explore every corner of the world. Most of the plants that they studied, classified, preserved in their herbaria, and cultivated whenever possible were sent to them by specialist plant collectors. Linnaeus recruited his former students to this task and called them “the Apostles.”

There was also a commercial aspect to plant collecting. Some plants had agricultural potential. Many more could ornament private parks and gardens, and landowners were willing to pay handsomely for the latest exotic plant to arrive from some remote and inaccessible region. Once they arrived, specimens were cultivated in selected sites where they were tended by experienced botanists and growers until they were acclimatized to their new environment. Once acclimatized, they found their way first to the gardens of the wealthy and later, as they became more plentiful and the price fell, to keen amateur gardeners of more modest means.

The great botanical gardens continue to send explorers out into the world in search of new plant species. Nowadays, of course, they work in collaboration with botanists in the countries they visit and must first obtain the permission of the host government. The specimens they collect and remove are for scientific research only. Quite apart from the right of all governments to regulate the exploitation of natural resources within their own borders, the risk of importing plant pests and diseases severely restricts the international movement of plant materials.

This chapter tells the story of a few of the great collectors, the places they visited, and the plants they sent home.

Geography of Plants

During the 18th century, as specimens of exotic plants arrived in Europe from every corner of the world, it became evident that particular types of plant were being found in particular places. Similar types of vegetation occurred in each of the continents apart from Antarctica, but each continent had its own distinctive species making up that vegetation. Tropical forests grow in Central and South America, Africa, Asia, and Oceania, for instance, and the forests appear to be very similar, but the trees, shrubs, and other plants growing in them are not the same. Certain euphorbias growing in arid regions of Africa closely resemble cacti, but they are not related and except for one species (Rhipsalis baccifera found in Africa, Madagascar, and Sri Lanka) cacti occur naturally only in America. Naturalists became interested in mapping the geographic distribution of plant species and the new science of biogeography was born.

This chapter outlines the development of plant geography. It begins with the story of the Prussian aristocrat who became one of the world’s most famous explorers and continues with a brief account of how the map of the world was divided into botanical regions. The chapter ends with the story of the Swedish botanist who was one of the most important plant geographers of the early 20th century.

Plant Cultivation

There is an ancient legend describing the supposed origin of the game of chess. The king of a prosperous country—different versions of the story locate it in various parts of the world—summoned his wisest adviser and asked him to devise a board game in which success would depend entirely on the skill of the players. This game, the king hoped, would prove popular among his people, who were growing addicted to gambling and games of chance. The wise man devised just such a game to be played on a board divided into 64 squares. The king was delighted and asked his adviser to name his own reward. The wise man replied that his needs were modest.

All he asked was one grain of wheat for the first square on the board, two for the second square, four for the third, and so on, doubling the number of grains for each square. The king readily agreed and sent his officials away to count out what he imagined was a very small payment. When they began to do the math, however, they quickly discovered that the wise man had lived up to his reputation by asking for 2 + 4 + 8 + 16 + 32 + 64 + 128 + 256 . . . grains and when they came to the end they must start over taking a different square as the first, so the final score had to be multiplied by 64. It amounted to a total of more than 18 quintillion (18 × 1018) grains of wheat. Not only was this far more wheat than all the granaries in the world could hold when full, it was far more than his country was capable of producing within the adviser’s lifetime, even if he lived to a very old age.

The story has three lessons. The first is that chess has been a popular game of skill for a very long time. The second is that those who make rash but seemingly innocuous promises should first learn to check the math. The third is that wheat is of vital importance. This chapter tells of the origin of a few of the most important food crops. These include wheat, rice, and corn, which are the staple foods over much of the world. Cotton has also been cultivated since very ancient times, and the chapter also tells as much as is known of its origin. The plants yielding these crops were domesticated long before writing was invented. Unraveling their history is one of the most fascinating—and most challenging—branches of science, where archaeology, botany, and genetics intersect.

Tea and coffee are stimulants, and their origins are associated with legends, which the chapter recounts. Finally, the story tells of the way certain plants were transported across the globe, and how some triggered the emergence of large and profitable industries in lands far from where they had originated.

Evolution of Plants

By the early years of the 19th century, natural scientists had come to recognize that the plants they observed and collected differed from those that their geologist colleagues found as impressions in coal and slates. This clearly implied that certain plants had become extinct in the distant past and others had taken their places. The most logical explanation for this was that plants had changed over long periods. In a word, they had evolved.

This chapter tells of some of the steps by which scientists traced the evolution of plants, beginning with the work of the man who is often described as the father of paleobotany—the scientific study of plant fossils and other traces and remains in order to reconstruct past environments and the evolutionary history of plants. It describes the development of the theory of evolution by means of natural selection and explanations for the discontinuous distribution of certain plants. Cultivated plants have also evolved as a consequence of their domestication. The chapter ends by describing the work and life of the Russian biologist who devised a method for identifying the regions of the world where modern crop plants were first cultivated.

Plant Physiology

Physiology is the scientific study of the way plants and animals work. Plant physiologists concern themselves with the ways plants obtain nutrients and energy and how they reproduce. This branch of botany is closely linked to the study of anatomy—the study of the structure of living organisms. While other scientists were devising ways to classify plants, seeking to account for their geographic distribution and unraveling their evolutionary history, the physiologists and anatomists were revealing the innermost details of the plants themselves. This chapter outlines the development of these studies.

The chapter begins with the scientists, one English and the other Italian, whose investigations marked the beginning of the modern study of plant anatomy and physiology. It goes on to tell of the discovery of plant cells, of the way water and nutrients move through plants, and the discovery of oxygen, which was the first step toward explaining respiration. The chapter ends with the introduction of modern cell theory and the internal structure of plant cells.

Ecology of Plants

Plants do not grow in isolation. Even in a semidesert, where large expanses of bare ground separate isolated clumps of plants, there are usually several species growing in those clumps. Plants growing close together exploit the environment in different ways. Some have deeper roots than others, to find water and nutrients at lower levels, while those with shallow roots derive nutrients from organic material decomposing near the surface.

By the second half of the 19th century, botanists had come to recognize that knowledge of the evolutionary history and relationships of plants and understanding of their physiology did not tell the whole story. In 1866 the German zoologist Ernst Heinrich Philipp Haeckel (1834–1919) published a two-volume work entitled Generelle Morphologie der Organismen (General morphology of organisms). Haeckel had read Darwin’s On the Origin of Species and was an enthusiastic supporter of the theory of evolution by natural selection.

Indeed, he had written a popular book expounding it, Natürliche Schöpfungsgeschichte (The natural history of creation). In Generelle Morphologie Haeckel sought to explore the implications of the theory. In doing so he coined a new word, Ökologie, to describe the web of relationships between living organisms and their physical, chemical, and biological surroundings. He applied the term principally to animals, but it applied equally to plants. Ökologie was transliterated into English as oecology, but following the Botanical Congress held in Madison, Wisconsin, in 1893, a group of botanists who had attended the congress agreed to standardize the spelling as ecology, and that is how the word has been spelled ever since. Ecology is the scientific study of the relationships among living organisms and between living organisms and their living and nonliving environment.

This chapter outlines the rise of plant ecology. It describes the way botanists learned to classify plants not by their evolutionary relationships, but according to the way they are adapted to the climatic conditions in which they grow. This led them to develop the concept of plants as communities and to the study of the many different types of plant communities.

Biodiversity and Plant Conservation

In June 1992 the United Nations held a Conference on Environment and Development (UNCED) in Rio de Janeiro, Brazil. Popularly known as the Earth Summit and the Rio Summit, 178 heads of government attended UNCED. The conference agreed on a number of treaties, one of which was a Convention on Protecting Species and Habitats, which was soon renamed the Convention on Biological Diversity. The title is often shortened to the Biodiversity Convention. Its objectives are set out, in the rather stilted language employed in all intergovernmental agreements, in the preamble to the convention:

The objectives of this Convention, to be pursued in accordance with its relevant provisions, are the conservation of biological diversity, the sustainable use of its components and the fair and equitable sharing of the benefits arising out of the utilization of genetic resources, including by appropriate access to genetic resources and by appropriate transfer of relevant technologies, taking into account all rights over those resources and to technologies, and by appropriate funding.

The convention was opened for the signature of government leaders who were present at UNCED on June 5, 1992. By the end of the summit, 150 heads of government had signed, and it came into force on December 29, 1993. By April 2009, 191 nations had joined.

This chapter discusses biodiversity, which is a contraction of biological diversity, with particular reference to plants. It begins by attempting to define the term and to explain why it is thought to be important. It continues by describing the historical effect on natural plant communities of the development of agriculture. The loss of natural vegetation to agricultural expansion and, more visibly though less significantly, to urban development generated a reaction that gave rise to the conservation movement. Areas were afforded legal protection from inappropriate exploitation. The chapter describes the origin and development of national parks and other protected areas in the United States and in other countries throughout the world. Finally, the chapter outlines the situation of the tropical forests.