Diversification Of Plant Study

Plant anatomy, which is concerned chiefly with the internal structure of plants, was established through the efforts of several scientific pioneers. Early plant anatomists of note included Marcello Malpighi (1628-1694) of Italy, who discovered various tissues in stems and roots, and Nehemiah Grew (1628-1711) of England, who described the structure of wood more precisely than any of his predecessors (Fig. 1.10).

Today, a knowledge of plant anatomy is used to help us find clues to the past, as well as for many practical purposes. For example, the related discipline of dendrochronology deals with determining past climates by examining the width and other features of tree rings. We can also learn much from archaeological sites by matching tree rings found in the wood of ancient buildings to the rings of wood of known age. Plant anatomy is also used to solve crimes. Forensic laboratories may use fragments of plant tissues found on clothing or under fingernails to determine where a crime took place or if certain persons could have been present where the crime was committed. The anatomy of leaves,

Anatomy Flowering Plants Animation
Figure 1.10 A thin section of Magnolia wood as seen through a microscope, x40.

stems, and other plant parts is currently being used to unravel and sort out relationships among plants. A form of plant anatomy, known as paleobotany, involves the study of plant fossils.

Plant physiology, which is concerned with plant function, was established by J. B. van Helmont (1577-1644), a Flemish physician and chemist, who was the first to demonstrate that plants do not have the same nutritional needs as animals. In a classic experiment, van Helmont planted a willow branch weighing 5 pounds in an earthenware tub filled with 74.4 kilograms (200 pounds) of dry soil. He covered the soil to prevent dust settling on it from the air, and after 5 years, he reweighed the willow and the soil. He found that the soil weighed only 56.7 grams (2 ounces) less than it had at the beginning of the experiment but that the willow had gained 164 pounds. He concluded that the tree had added to its bulk and size from the water it had absorbed. We know now that most of the weight came as a result of photosynthetic activity (discussed in Chapter 10), but van Helmont deserves credit for landmark experimentation in plant physiology.

Modern plant physiologists have learned how to isolate and clone genes (units of heredity that are found within the nuclei of cells) and are using the knowledge gained to learn in precise detail much more about plant functions, including how plants conduct materials internally; how temperature, light, and water are involved in growth; why plants flower; and how plant growth regulatory substances are produced, to mention just a few.

European explorers of other continents during past centuries took large numbers of plants back home with them, and it soon became clear to those working with the plants that some sort of formalized system was necessary just to keep the collections straight. Several plant taxonomists

What Is Plant Biology?

(botanists who specialize in the identifying, naming, and classifying of plants) proposed ways of accomplishing this, but we owe our present system of naming and classifying plants to the Swedish botanist Carolus Linnaeus (1707-1778) (see Fig. 16.2).

Plant taxonomy (also called plant systematics), which is the oldest branch of plant study, began in antiquity, but Linnaeus did more for the field than any other person in history. Thousands of plant names in use today are those originally recorded in Linnaeus's book Species Plantarum, published in 1753. An expanded account of Linnaeus and his system of classification is given in Chapter 16.

There are still thousands of plants, fungi, and other organisms that have not yet been described or even discovered. Although it obviously is already too late to identify species that were not described before they became extinct, plant taxonomists around the world have united to try to identify and describe as many new organisms—many with food, medicinal, and other useful potential—before much more of their natural habitat disappears. Other plant taxono-mists, through the use of cladistics (analysis of shared features) and molecular techniques, are refining our knowledge of plant relationships and are contributing to the improvement of many of our food crops.

Plant taxonomists often specialize in certain groups of plants. For example, pteridologists specialize in the study of ferns, while bryologists study mosses and plants with similar life cycles.

The discipline of plant geography, the study of how and why plants are distributed where they are, did not develop until the 19th century (Fig. 1.11). The allied field of plant ecology, which is the study of the interaction of plants with one another and with their environment, also developed in the 19th century.

After the publication in 1962 of a best-seller entitled Silent Spring (authored by Rachel Carson), public awareness of the field of ecology as a whole increased considerably. In this book, based on more than 4 years of literature research, Ms. Carson called attention to the fact that more than 500 new toxic chemicals annually are put to use as pesticides in the United States alone, and she detailed how these chemicals and other pollutants were having an insidious impact on all facets of human life and the environment.

The study of the form and structure of plants, plant morphology, was developed during the 19th century, and during the 20th century, much of our basic knowledge about the form and life cycles of plants was incorporated in the plant sciences as we know them today. During this time, the number of scientists engaged in investigating plants also greatly increased.

Genetics, the science of heredity, was founded by the Austrian monk Gregor Mendel (1822-1884), who performed classic experiments with pea plants. Today, various branches of genetics include plant breeding, which has greatly improved yields and quality of crop plants, and genetic engineering. Genetic engineering includes the introduction of

What Is Plant Biology?

Tropical Plants Science Projects

Figure 1.11 Ecologists, plant geographers, and other biologists recognize large communities of plants and animals that occur in areas with distinctive combinations of environmental features. These areas, called biomes, are represented here by the tropical rain forest, which, although occupying less than 5% of the earth's surface, is home to more than half of the world's species of organisms.

Figure 1.11 Ecologists, plant geographers, and other biologists recognize large communities of plants and animals that occur in areas with distinctive combinations of environmental features. These areas, called biomes, are represented here by the tropical rain forest, which, although occupying less than 5% of the earth's surface, is home to more than half of the world's species of organisms.

genes from one organism to another and has already improved the pest, frost, and disease resistance, as well as yields, of some crop plants. It holds enormous potential for continued development of better agricultural, medicinal, and other useful plants. Future control of human, animal, and plant diseases is also anticipated.

Cell biology (previously called cytology), the science of cell structure and function, received a boost from the discovery of how cells multiply and how their various components perform and integrate a variety of functions, including that of sexual reproduction. The mid-20th-century development of electron microscopes (see Chapter 3) further spurred cell research and led to a vast new insight into cells and new forms of cell research that continues to the present.

Economic Botany and ethnobotany, which involve practical uses of plants and plant products, had their origin in antiquity as humans discovered, used, and eventually cultivated plants for food, fiber, medicines, and other purposes. Today, research is being conducted on the uses of plants by indigenous peoples with an eye to discovering medicines and other useful plant products previously unknown in developed countries.

There is still a vast amount of botanical information to be discovered. For example, 11,000 papers on botanical subjects were published in 1938 alone, and the number per year in recent times is much greater. It also appears probable that at the start of the 21st century, at least one-third of all the organisms regarded in the past as plants (particularly algae and fungi) have yet to be named, let alone thoroughly investigated and understood.

10 Chapter 1

Summary

1. Why do some plants produce poisons while others are edible and useful? Are there large carnivorous plants? How and why do plants respond to their environment? What is the future of tropical rain forests? What can be done about pollution and other environmental problems?

2. Human populations have increased dramatically in the past few centuries, and the disruption of the balance of nature by the activities directly or indirectly associated with the feeding, clothing, and housing of billions of people threatens the survival of not only humans but many other living organisms.

3. We are totally dependent on green organisms because they alone can convert the sun's energy into forms that are usable by, and vital to the very existence of, animal life.

4. We largely take plants and plant products for granted. Animals, animal products, many luxuries and condiments, and other useful substances, such as fibers, lumber, coal, medicines, and drugs, either depend on plants or are produced by them.

5. To ensure human survival, all persons soon may need to acquire some knowledge of plants and how to use them. Plants will undoubtedly play a vital role in space exploration as portable oxygen generators.

6. Teams of scientists are interviewing medical practitioners and herbal healers in the tropics to locate little-known plants used by primitive peoples before the plants become extinct.

7. Botany, the study of plants, apparently began with Stone Age peoples' practical uses of plants. Eventually, botany became a science as intellectual curiosity about plants arose.

8. A science involves observation, recording, organization, and classification of facts. The verifying or discarding of facts is done chiefly from known samples through inductive reasoning. The scientific method involves specifically following a routine series of steps and generally assuming and testing hypotheses.

9. The microscope has had a profound effect on studies in the biological sciences and led to the discovery of cells.

10. Plant anatomy and plant physiology developed during the 17th century. J. B. van Helmont was the first to demonstrate that plants have nutritional needs different from those of animals. During the 17th century, Europeans engaged in botanical exploration on other continents and took plants back to Europe.

11. During the 18th century, Linnaeus produced the elements of our present system of naming and classifying plants.

12. During the 19th century, plant ecology, plant geography, and plant morphology developed, and by the beginning of the 20th century, genetics and cell biology became established. Much remains yet to be discovered and investigated.

Review Questions

1. How and to what extent have humans affected their natural environment?

2. What is meant by the scientific method?

3. To what extent is animal life dependent on green organisms for its existence?

4. In terms of biological experiments, what are hypotheses and controls?

5. What is the oldest branch of botany, and why did it precede other branches?

6. What are the basic features of each of the other branches of botany?

Discussion Questions

1. Since humans survived on wild plants for thousands of years, might it be desirable to return to that practice?

2. What factors are involved in possibly determining if and when humans might not be able to sustain themselves on this planet?

3. How would you guess that Stone Age peoples discovered medicinal uses for plants?

4. Many of the early botanists were also medical doctors. Why do you suppose this is no longer so?

5. Consider the following hypothesis: "The majority of mushrooms that grow in grassy areas are not poisonous." How could you go about testing this hypothesis scientifically?

Learning Online

Visit our webpage at http://www.mhhe.com/botany for interesting case studies, practice quizzes, current articles, and animations within the Online Learning Center to help you understand the material in this chapter. You'll also find active links to these topics:

Introductory Materials and Governmental Sites

General References in Botany

Writing Papers and Study Tips

Glossaries and Dictionaries

Careers in Science

Utility and Organizational Sites

Scientific Method

General References in Botany

Microscopy

Economic and Ecological Importance of Angiosperms Origins of Agriculture

What Is Plant Biology?

Additional Reading

Carson, R. L. 1999. Silent spring. Boston: Houghton Mifflin. Davis, E. B., and D. Schmidt. 1995. Guide to information sources in the botanical sciences, 2d ed. Englewood, CO: Libraries Unlimited.

Ewan, J. (Ed.). 1969. A short history of botany in the United States.

Forestburgh, NY: Lubrecht & Cramer. Johnson, T. 1998. CRC ethnobotany desk reference. Boca Raton, FL: CRC Press.

McCarthy, S. 1993. Ethnobotany and medicinal plants. Upland, PA: Diane Publishing.

Morton, A. G. 1981. History of botanical science: An account of the development of botany from the ancient time to the present. San Diego, CA: Academic Press.

Nordenskiold, E. 1988 reprint of 1935 ed. The history of biology. Irvine, CA: Reprint Services Corp.

Swift, L. H. 1974 reprint of 1970 ed. Botanical bibliographies: A guide to bibliographic materials applicable to botany. Ann Arbor, MI: University Microfilms International.

Roots For Diversification
A flowering head of burdock (Arctium lappa), a weed whose burs catch in clothing and the fur and hide of animals. Burdock is cultivated in Japan for its edible roots.

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