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WHY PLANT-BIOLOGY RESEARCH TODAY?

Throughout human history, plants have been the object of pervasive and at times dominant artistic and intellectual interest. Plants were important subjects from the earliest study of life processes, and they were central to scientific study in the nineteenth and early twentieth centuries.

Good reasons remain to study the basic life processes of plants. Research on plants enriches our intellectual life and adds to our knowledge about other life processes. The results of research on plant systems also can teach us how to approach problems in agriculture, health, and the environment.

PLANTS, HUMAN HEALTH, AND CIVILIZATION

Our understanding of plant life underpins a vast range of activities and touches virtually every aspect of human life. From their origins, human civilizations have depended for their development and prosperity on their ability to manage plants and have sometimes fallen because of their failure to do so. Throughout history, plants have been collected, traded, selectively adapted for new environments, and bred for new combinations of traits. Plants have been manipulated for use as food and fiber, and for many other, particularly aesthetic, purposes.

Modern civilization rests on the successful and sustained cultivation of plants and on the wise use of the biologic and physical resource base on which their cultivation depends. Our knowledge about the world around us is incomplete if we do not include plants in our discoveries, and it is distorted if we do not place sufficient emphasis on plant life. There are many compelling practical reasons also for society to invest in



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Plant Biology Research and Training for the 21st Century 1 WHY PLANT-BIOLOGY RESEARCH TODAY? Throughout human history, plants have been the object of pervasive and at times dominant artistic and intellectual interest. Plants were important subjects from the earliest study of life processes, and they were central to scientific study in the nineteenth and early twentieth centuries. Good reasons remain to study the basic life processes of plants. Research on plants enriches our intellectual life and adds to our knowledge about other life processes. The results of research on plant systems also can teach us how to approach problems in agriculture, health, and the environment. PLANTS, HUMAN HEALTH, AND CIVILIZATION Our understanding of plant life underpins a vast range of activities and touches virtually every aspect of human life. From their origins, human civilizations have depended for their development and prosperity on their ability to manage plants and have sometimes fallen because of their failure to do so. Throughout history, plants have been collected, traded, selectively adapted for new environments, and bred for new combinations of traits. Plants have been manipulated for use as food and fiber, and for many other, particularly aesthetic, purposes. Modern civilization rests on the successful and sustained cultivation of plants and on the wise use of the biologic and physical resource base on which their cultivation depends. Our knowledge about the world around us is incomplete if we do not include plants in our discoveries, and it is distorted if we do not place sufficient emphasis on plant life. There are many compelling practical reasons also for society to invest in

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Plant Biology Research and Training for the 21st Century research about plants and to educate its citizens for careers in which knowledge about plants is important. From fundamental discoveries about plant life arise technologies and capabilities in a wide range of practical applications (Figure 2). Figure 2Potential applications of plan-biology research.

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Plant Biology Research and Training for the 21st Century PLANTS AND THE ENVIRONMENT Only higher plants and a few microorganisms can convert light energy from the sun into chemical energy. Photosynthetic organisms are at the center of the earth's hospitality to other life. Plants and photosynthetic bacteria gave rise to the earth's atmosphere. They are important in regulating climate and the chemical and biologic conditions of the soil and water. Photosynthetic plants are the source of the fossil fuels we are depleting today, and they provide the most readily harvested source of renewable energy for tomorrow. The primary atmospheric gas incorporated by plants in photosynthesis, carbon dioxide, is one of the major ''greenhouse'' gases. Plants regulate the carbon cycle of the biosphere. Plants, in part through their unique symbiotic relationships with microorganisms, also play a major role in regulating the partitioning of nitrogen between atmospheric and life processes. We will never fully understand the global environment—or have a serious hope of successfully managing it in the face of explosive population growth—until we have a much more comprehensive understanding of plants, their cellular processes, and their ecology and population biology. Plants are important in maintaining a healthy environment, for example, by controlling erosion and water pollution, and by helping to reduce air pollution. They improve the environment for human activities everywhere—from indoor spaces to vast wilderness areas. The role of terrestrial plants and marine phytoplankton in maintaining an environment suitable for human habitation is inadequately appreciated, but there is a growing recognition of the urgent need to illuminate the role of plants. The accumulated effects of more than a century of industrial activity, explosive population growth, severe shifts in land use,

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Plant Biology Research and Training for the 21st Century Unique and Scientifically Interesting Properties of Plants Plants differ from animals in several important ways. Development. The growth of a plant from an undifferentiated cell into a complete and mature organism requires only a few hormones. Moreover, plant cells are totipotent: It is possible to regenerate a whole plant from a single leaf or root cell. In contrast, specific cells (the germ line) of an animal in early development form the germ cells. Plants have no germ line in this sense and produce sexual organs and gametes from somatic tissue late in their development. Biochemistry. Plants are virtually the sole source of new oxygen and carbohydrates on the planet. Light is harvested by unique organelles, the chloroplasts. Plants synthesize the 20 amino acids required for proteins, including the 10 amino acids that humans are unable to produce. Moreover, in a unique symbiotic relationship with some plants, microorganisms can fix atmospheric nitrogen for plant use in the synthesis of amino acids, proteins, and other compounds. Physiology. Plants lack the major organ systems present in animals. Yet, their physiology permits them to respond to their environment. Instead of an immune system, they have inducible disease resistance mechanisms that enable them to make natural toxins against fungal and bacterial pathogens. Instead of a nervous system, they have a repertoire of receptors and pigments that allow them to respond to their environment. Instead of a muscular and skeletal system, they have a novel set of fibers for support. They are attached to their substrates, and they can move only by growing or by gaining or losing water.

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Plant Biology Research and Training for the 21st Century Plants and Global Warming Atmospheric modelers are trying to evaluate the effects of changes in carbon dioxide concentration on global weather patterns and temperature. Models that predict carbon dioxide uptake and water loss by leaves grown under different environmental conditions can make an important contribution to elucidating global climate change. Other plant research is needed to develop sensitive ways to determine how much of the light energy absorbed by a leaf is used for photosynthesis (for metabolism and growth) and how much is simply reradiated as heat. The efficiency with which plants use light can vary enormously in response to environmental variables, such as water stress, temperature, disease or insect damage, or fluctuations in the supply of nitrogen or phosphorus. Theoretical models are being rigorously tested, with a fair degree of success. In addition, remote-sensing techniques are being developed to evaluate the photosynthetic performance of whole plant communities in response to stress. Modeling and experimental studies promise the quantitative information required to put predictions of atmospheric change (or lack of it) on a sound basis. and other effects of human use of the earth show that human activities can overpower the buffering effects of the natural processes that regulate global climate. The health and wellbeing of the human race could well rest on our achieving a better understanding on which to base a more reasoned exploitation of plant life.

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Plant Biology Research and Training for the 21st Century PLANTS IN AGRICULTURE, MEDICINE, AND INDUSTRY Macroscopic and microscopic plants form the first link in the terrestrial and aquatic food chains. Plants are thus at the heart of agriculture. Together with microorganisms and domesticated animals, plants provide the raw materials for our food and drink. Plants also provide many of the materials used in clothing and buildings. The application of basic knowledge about plants has made modern agriculture possible. For example, studies of the nutrient requirements of plants led to soil fertility management. The Green Revolution was founded on fundamental knowledge gleaned from research in genetics and plant nutrition. Genetic manipulation is a powerful, proven method for improving the productivity, quality, and disease resistance of plants. Basic knowledge of genetic inheritance, defense responses, pathogen genetics, and population genetics will continue to yield improvements in the technology needed to secure a stable food supply. Plants are critical to human health. They are the sole source of some of the essential amino acids, vitamins, and other nutrients in our diet. Research with plants was central to elucidating the role of vitamins in human health and disease: Plants high in ascorbic acid, such as peppers and citrus, prevent scurvy. Grains in the diet provide B vitamins. Many drugs were first discovered as plant products before methods for their synthesis were developed. Research on plants yielded cardiac glycosides (such as digitalis), a wide range of useful alkaloids (such as scopolamine, atropine, quinine, and ephedrine), dicoumarol, and many other drugs. Research on lower plants and agricultural soils yielded many antibiotics. Even today, more than 20 percent of all prescription drugs are derived from plants.

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Plant Biology Research and Training for the 21st Century The chemical industry developed from the work of German scientists who learned to synthesize dyes from coal tar, a derivative of fossil plants, to replace the commonly used dyes derived from wild and cultivated plants. Now, the search has been reversed and plant-derived products are sought to replace harmful coal tar dyes. Modern industry and society continue to depend in many ways on chemical products derived from plants, such as soaps, detergents, rubber, paints, resins, plastics, adsorbents, and adhesives. PLANTS AND THE ORIGINS OF MODERN BIOLOGY Research with plants has strongly influenced the development of biology and has contributed to many important scientific advances. It was research with plants that led to the discovery of the rules of genetic inheritance (Gregor Mendel's peas), of the role of light in regulating the physiologic responses of higher organisms (phytochromes), of transposition of genetic elements (controlling elements in maize), and of the protein nature of enzymes (urease). Research with a plant virus contributed to the elucidation of the structure of DNA itself (X-ray diffraction with tobacco mosaic virus) and of the role of nucleic acids in the genetic material of all life forms. These examples illustrate how the study of plants has affected biologic research for several generations. But how well equipped are we to deal with the opportunities and challenges that lie ahead? The techniques of modern biology, and in particular modern genetics, make many difficult problems in plant biology approachable. Before the era of recombinant DNA, the tools available for genetic studies of plants' development, metabolism, and environmental responsiveness were relatively crude. Now modern genetics offers new promise to the plant sciences. In some fields of modern biology, plants offer the preferred model system for

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Plant Biology Research and Training for the 21st Century fundamental and exploratory science through application of molecular genetic techniques. Scientists now can transfer genes easily among plant species, and because the genomes of some plant species are quite small they can be studied readily. Plants can be used to answer many general questions in biology in such diverse subdisciplines as development, metabolism, gene regulation, symbiosis, and chromosome structure. It is not within the scope of this report to describe a research agenda for plant sciences. Other National Research Council reports have contained pertinent research agendas, for example, Investing in Research (NRC, 1989a), Opportunities in Biology (NRC, 1989b), and Forestry Research: A Mandate for Change (NRC, 1990). In recent years, the scientific community has shown significantly increased interest in research with plants. The power of modern methods to answer important questions in plant biology has stimulated the interest of scientists in leading universities and other research institutions in the United States and abroad. Well-funded plant-biology laboratories here and elsewhere are making research contributions at the cutting edge of biology. This heightened interest has generated more worthy research proposals than public agencies can fund. An informal survey of the private sector in agricultural biotechnology indicates that in the late 1980s about $250 million (exclusive of development costs) each year was being spent on basic plant-biology research by companies whose work was primarily or exclusively with plants. The fertility of modern plant-biology research is demonstrated in special issues of Science (November 16, 1990) and Cell (January 27, 1989). Developmental biology, cell-to-cell recognition, signal transduction, the molecular basis of disease, plant-microbe interactions, gene regulation, transposition, and photosynthesis are some of the areas covered in these issues. Several new plant journals have been launched recently; three leading examples are: The Plant Cell, The Plant Journal, and Plant Molecular Biology.