Chapter 3 — Science of Plants – Botany

The word botany comes from the Greek botane, meaning a plant, herb or pasture, and botany is defined as the scientific study of plants. The term biology, the study of living organisms, was coined independently by Lamarck and Treviranus in 1802, and botany and zoology are its two classical halves; today the science is often called plant biology or plant science to emphasise its unity with the rest of biology. A botanist studies what plants are made of, how they grow and function, how they reproduce, how many kinds there are, how they are related, where they live and how they can be used.

The scope of botany is as wide as the plant world. It covers the smallest algae and the tallest trees, plants of the sea, the desert and the mountain top, fossil plants of the coal measures and cultivated plants of the field. Traditionally it also covered the bacteria, fungi and algae, which are still taught in botany departments although modern classification places bacteria and fungi in separate kingdoms. It draws on chemistry and physics to explain photosynthesis and transport, on mathematics for genetics and ecology, on geology for palaeobotany, and on computing for the analysis of DNA sequences.

Why study plants? First, because plants are the producers on which every other organism depends: through photosynthesis they convert the energy of sunlight into the chemical energy of food, and they release the oxygen that animals breathe. Second, because human life rests on plants: cereals, pulses, oils, fruits and vegetables for food; cotton and jute for fibre; timber and bamboo for shelter; fuel wood; rubber, gums, resins and dyes for industry; and thousands of medicines, from quinine to taxol, drawn from plant chemicals. Third, because plants shape the environment: they bind soil, regulate the water cycle, moderate climate, absorb carbon dioxide and provide habitat for animals. Fourth, because plants are beautiful and their study is a pleasure in itself, in gardens, parks and wild places.

Botany is both a pure science, seeking understanding for its own sake, and an applied science, putting that understanding to use in agriculture, forestry, horticulture, medicine and industry. The two are inseparable: Mendel's curiosity about pea flowers became the plant breeding that doubled India's wheat harvest, and the study of a soil fungus gave the world penicillin.

For the Intermediate student this chapter is a map of the territory. Every later chapter, morphology, anatomy, taxonomy, cell biology, physiology, reproduction, is a branch of the tree described here, and the names and definitions given in this chapter recur throughout the two years of the course.

The oldest written references to plants in the world are in the Vedas. The Rig Veda, composed more than three thousand years ago, names some seventy plants and speaks of their uses in ritual, food and healing; the Atharva Veda contains many hymns on medicinal herbs and describes plants by their habit as trees, shrubs, herbs, creepers and grasses, an early classification. The Yajur Veda and the Brahmanas mention the cultivation of barley, rice and sesame, and the Upanishads use the growth of the banyan seed as a metaphor for the unfolding of the universe.

The most remarkable ancient Indian botanical work is the Vrikshayurveda of Parashara, composed in the first centuries before or after the beginning of the common era. Vrikshayurveda means the science of plant life, and it is the first known text to treat plants as objects of scientific study rather than only of use. Parashara described the external morphology of plants, distinguishing roots, stems, leaves, flowers and fruits, and classified flowering plants into families on the basis of floral characters. Several of his families correspond closely to modern ones: Shamiganiyam to the Leguminosae (Fabaceae), Tripushpaganiyam to the Cucurbitaceae, Mallikaganiyam to the Apocynaceae, Kurchapushpaganiyam to the Asteraceae (Compositae). He was also the first to describe the internal structure of plants. He noted that the leaf is made of countless minute compartments filled with sap, which he called rasakosa, a description that anticipates the plant cell by nearly two thousand years, and he named the green colouring matter of the leaf ranjakam, the substance now called chlorophyll, and understood that it was formed in the presence of light. He described the conducting tissues, the process of nutrition from soil water, and the role of the seed and the seedling.

The Ayurvedic medical texts continued this tradition. The Charaka Samhita and the Sushruta Samhita catalogue hundreds of medicinal plants with their properties, preparation and doses, and Sushruta classifies plants by their medicinal action into groups. Later works, the Ashtanga Hridaya of Vagbhata and the Nighantus, are botanical dictionaries of drug plants. Ancient Indian agriculture is recorded in the Krishi Parashara, which deals with soil, seasons, seed selection, manuring and the management of crops; and the Arthashastra of Kautilya lays down rules for forests, gardens and the cultivation of useful plants under state supervision.

This tradition treated plants as living beings with senses: the Mahabharata and the Manusmriti state that plants feel pleasure and pain, an idea that the twentieth-century experiments of Jagadish Chandra Bose would take up in a scientific spirit. The Indian contribution to early botany was thus threefold: an enormous inventory of useful plants, a rational classification by floral characters, and the first glimpse of the internal structure and green pigment of the leaf.

In Greece the study of plants began within philosophy. Aristotle (384–322 BCE), who founded zoology, regarded plants as living things possessing a vegetative soul, capable of nutrition and growth but not of sensation, and placed them below animals in his ladder of nature. His student Theophrastus (about 371–287 BCE) took over Aristotle's school and garden at Athens and devoted himself to plants. His two surviving works, Historia Plantarum (Enquiry into Plants) and De Causis Plantarum (On the Causes of Plants), describe about five hundred species, classify them into trees, shrubs, undershrubs and herbs, distinguish annuals, biennials and perennials, note the difference between flowering and non-flowering plants and between what we now call monocots and dicots (by the structure of the seed), describe plant organs, and treat germination, propagation, cultivation and the geography of plants. For this body of work, which remained the standard for eighteen centuries, Theophrastus is called the father of botany.

The Roman world added practical works. Pliny the Elder's Natural History compiled all that was known about plants and their uses; Dioscorides, a Greek physician in the Roman army in the first century CE, wrote De Materia Medica, describing some six hundred medicinal plants with their identification and preparation. Dioscorides was the authority on drug plants in Europe and the Islamic world for fifteen hundred years.

Through the medieval period the knowledge of plants was preserved and extended by Arab and Persian scholars, notably Ibn Sina (Avicenna), whose Canon of Medicine drew on Indian and Greek sources, and Ibn al-Baitar, whose compendium described over 1,400 plants. In Europe the monastery gardens kept the medicinal plants alive, and in India the Ayurvedic and Unani systems continued to add to the catalogue of drug plants.

The Renaissance of the sixteenth century revived direct observation. The German herbalists, Otto Brunfels, Jerome Bock and Leonhart Fuchs, produced printed herbals with accurate woodcut illustrations drawn from living plants rather than copied from older manuscripts; Fuchs's De Historia Stirpium (1542) with its five hundred figures is a landmark. The Italian Andrea Cesalpino (1583) proposed the first classification based on fruit and seed rather than on use or habit, a step toward a natural system. The first herbaria, collections of pressed plants, were made in Italy at this time by Luca Ghini, and the first botanical gardens for teaching were founded at Pisa (1544) and Padua (1545).

Meanwhile European voyages to Asia, Africa and America brought thousands of new plants to be described. The Hortus Malabaricus, compiled in Kochi between 1678 and 1693 by the Dutch governor Van Rheede with the help of Malayali physicians and Konkani Brahmins, described and illustrated 742 plants of the Malabar coast in twelve volumes, with names in Malayalam, Konkani, Arabic and Latin; it is the first printed flora of any part of India and remains a botanical treasure.

Thus by 1700 the western tradition had accumulated description, medicine, illustration and the beginnings of classification, but it still lacked a theory of plant structure, a universal system of names and any idea of how plants had come to be. The next three centuries supplied all three.

Three instruments and ideas transformed the study of plants between 1650 and 1900: the microscope, the binomial system, and evolution.

The microscope and plant structure. In 1665 Robert Hooke, examining a thin slice of cork under his compound microscope, saw a honeycomb of tiny boxes that he named cells, from their resemblance to the cells of a monastery. In the 1670s the Italian Marcello Malpighi and the Englishman Nehemiah Grew, working independently, published the first systematic plant anatomy, describing the tissues of root, stem and leaf, the vessels, the fibres and the stomata; Grew's Anatomy of Plants (1682) established the subject. Later, in 1838, Matthias Schleiden proposed that all plants are built of cells, and with Theodor Schwann's work on animals this became the cell theory, the foundation of modern biology.

Plant sexuality and physiology. Rudolf Camerarius (1694) proved by experiment that plants reproduce sexually, the stamens being the male and the pistil the female organ, and that pollen is necessary for seed formation. Stephen Hales in Vegetable Staticks (1727) measured the movement of water through plants and founded plant physiology. Joseph Priestley (1772) showed that a green plant restores air made foul by a burning candle, and Jan Ingenhousz (1779) showed that this happens only in light: the discovery of photosynthesis. Julius von Sachs in the nineteenth century showed that starch is made in the chloroplast and gave physiology its experimental methods.

Linnaeus and classification. Carl Linnaeus (1707–1778), a Swede, brought order to the chaos of names. In Species Plantarum (1753) he gave every known plant a two-word Latin name, genus and species, the binomial nomenclature still used today, and he arranged plants in a sexual system of 24 classes by the number and arrangement of stamens. The system was artificial, grouping unrelated plants together, but it was simple and universal and it made the world's flora manageable. Linnaeus is called the father of taxonomy. Later workers built natural systems on many characters: Antoine de Jussieu (1789) grouped genera into families that are still recognised; Bentham and Hooker's Genera Plantarum (1862–1883) described all known seed plant genera in a natural system that Indian herbaria follow to this day.

Darwin and evolution. Charles Darwin's Origin of Species (1859) explained why organisms fall into nested groups: they share ancestors, and natural selection has shaped their differences. Classification became the reconstruction of a family tree, and phylogenetic systems such as those of Engler and Prantl and Hutchinson followed. Darwin himself was a considerable botanist, writing on climbing plants, insectivorous plants, orchid pollination and the power of movement in plants.

Genetics and the twentieth century. Gregor Mendel's experiments on garden peas (1866), rediscovered in 1900, founded genetics on a plant. The twentieth century added plant hormones (Went, 1928), the biochemistry of photosynthesis (Calvin), the structure of DNA (1953) and molecular biology, and finally the sequencing of whole plant genomes, beginning with Arabidopsis thaliana in 2000 and rice in 2002. Modern botany is thus the meeting of the old descriptive tradition with experiment, chemistry and information science.

Botany is divided into branches according to what aspect of the plant is studied. The first group of branches deals with the form and structure of plants at every scale, from the whole plant to the molecule, and with how that structure develops.

Morphology is the study of external form and structure: the shapes of roots, stems, leaves, flowers, fruits and seeds, their arrangement and their modifications. It provides the characters used in identification and classification and is the first botany a student learns. Anatomy is the study of internal structure, the tissues and their arrangement in root, stem and leaf, as seen in sections under the microscope; histology, the study of tissues, is a part of it, and wood anatomy is important in forestry. Cytology, or cell biology, is the study of the cell: its wall, membrane, organelles, nucleus and chromosomes, and its division by mitosis and meiosis. Embryology is the study of the formation of gametes, fertilisation and the development of the embryo and seed; in flowering plants it includes the study of the embryo sac and pollen tube. Palynology is the study of pollen grains and spores, their wall structure and sculpture, which are used in taxonomy, in reconstructing past vegetation from pollen in lake sediments, in honey analysis and in forensic science.

Developmental biology studies how a single cell becomes a whole plant: the differentiation of tissues, the patterning of organs, the control of growth by hormones and genes. It joins anatomy and physiology with genetics. Plant growth and movement are studied under physiology.

Molecular biology studies the structure and function of the large molecules of the cell, DNA, RNA and proteins, and how genes are expressed; plant biochemistry studies the chemical reactions of plant life and the compounds plants make. Both are now central to every other branch.

These structural branches answer the question what is a plant made of and how is it put together? The Intermediate course devotes separate chapters to morphology of flowering plants, cell structure, cell division and the anatomy of flowering plants, so the definitions here should be linked to those chapters. In the examination this material is asked as a list: define five branches of botany, or match the branch with what it studies.

The second group of branches deals with what plants do, how many kinds there are, and how they are related to one another and to their surroundings.

Plant physiology is the study of the life processes and functions of plants: absorption and transport of water and minerals, photosynthesis, respiration, growth, movement, flowering and the action of plant hormones. Plant biochemistry and biophysics are its molecular and physical foundations.

Taxonomy (systematic botany) is the science of identification, nomenclature and classification of plants, as studied in the first chapter. Systematics adds the study of evolutionary relationships. Within taxonomy there are branches for particular groups of organisms traditionally studied by botanists:

• Phycology (algology): the study of algae.
• Mycology: the study of fungi.
• Bacteriology: the study of bacteria.
• Virology: the study of viruses.
• Lichenology: the study of lichens.
• Bryology: the study of bryophytes (mosses and liverworts).
• Pteridology: the study of pteridophytes (ferns and their allies).
• Dendrology: the study of trees and woody plants.
• Agrostology: the study of grasses.

Genetics is the study of heredity and variation: how characters pass from parent to offspring and how they change. Cytogenetics joins it to the study of chromosomes; plant breeding applies it. Evolution studies the origin of species and the descent of plant groups over time.

Ecology is the study of the relationship of plants with their environment, living and non-living: the factors of climate and soil, the adaptation of plants to habitat, the structure of plant communities, succession, and the flow of energy and matter through ecosystems. Phytogeography (plant geography) is the study of the distribution of plants on the earth and the causes of that distribution. Palaeobotany is the study of fossil plants, which tells the history of the plant kingdom and of past climates; it is closely linked to the coal, oil and gas industries. Ethnobotany is the study of the relationship between people, especially traditional communities, and plants: the uses, names and beliefs attached to them, which has led to many new drugs.

These branches together answer the questions how does a plant live, what plants exist, and how did they come to be where they are? Physiology, ecology and genetics are taught in detail in the second year of the Intermediate course; taxonomy and the plant groups are the subject of the first-year chapters that follow.

The applied branches of botany put the knowledge of the pure branches to use in producing food, fibre, timber and other plant products, and in protecting plants and the environment. The three oldest are the sciences of growing plants.

Agriculture is the science and practice of cultivating field crops and raising livestock. Its botanical side includes agronomy, the management of soils and crops: tillage, sowing, irrigation, manuring, weed control and harvesting; soil science; crop physiology; and the selection of varieties suited to a region. Agriculture is the largest occupation in Telangana and India, and the Green Revolution of the 1960s, which more than doubled India's wheat and rice harvests through dwarf high-yielding varieties, fertiliser and irrigation, was applied botany on a national scale. Its architects included Norman Borlaug and, in India, M. S. Swaminathan.

Horticulture, from the Latin hortus (garden), is the science of growing garden plants: fruits (pomology), vegetables (olericulture), flowers and ornamentals (floriculture), and landscape and nursery plants. It includes the techniques of propagation by cuttings, layering, grafting and budding, of pruning and training, of glasshouse and hydroponic culture, and of post-harvest handling. Telangana's mango, citrus, guava, chilli, turmeric and flower crops are horticultural. Tissue culture, the growing of plants from cells in sterile nutrient media, is now a routine horticultural tool for producing thousands of identical disease-free plantlets of banana, orchids, teak and sugarcane.

Forestry (silviculture) is the science of raising, managing and harvesting forests for timber, fuel, pulp, fodder and non-wood products, and of protecting them for their role in soil and water conservation, climate regulation and wildlife habitat. Foresters study dendrology, wood anatomy, forest ecology, nursery technique and fire and pest management. Social forestry and agroforestry bring trees on to farms and village lands, and Haritha Haram, the Telangana plantation programme, is forestry applied to restoring the state's tree cover.

Other applied fields grouped with these are economic botany, the study of plants of commercial value, their products and their trade; pharmacognosy, the study of crude drugs of plant origin, their identification, chemistry and properties, which is the botanical half of pharmacy; sericulture, in which the mulberry plant is grown to feed silkworms; and apiculture, in which bee forage plants are managed for honey.

Each of these fields has its own colleges and research institutes in India, and each begins with the botany of this course: morphology to recognise the plant, physiology to grow it, genetics to improve it and ecology to fit it to its place.

Plant breeding is the applied science of improving crop plants by changing their heredity. Its methods are selection of the best plants from a variable population; hybridisation, crossing two parents to combine their good characters and then selecting among the offspring; mutation breeding, inducing new variation with radiation or chemicals; polyploidy, doubling chromosome numbers to obtain larger and sometimes seedless plants; and, most recently, genetic engineering. The objectives are higher yield, better quality, resistance to diseases, pests and drought, and suitability to machinery and markets. Every variety a farmer sows today is the product of plant breeding: the semi-dwarf rices of IRRI and the Indian institutes, the hybrid maize, sorghum and pearl millet, the Bt cotton of Telangana's fields.

Plant pathology (phytopathology) is the study of plant diseases: their causes (fungi, bacteria, viruses, nematodes, mycoplasma, nutrient deficiency), their symptoms, their spread and their control. It applies mycology, bacteriology, virology and genetics to keep crops healthy. The Irish potato famine of 1845, caused by Phytophthora, and the Bengal famine of 1943, worsened by Helminthosporium on rice, show why. Control measures include resistant varieties, crop rotation, seed treatment, fungicides and biological control, and the field is now joined by plant quarantine, which stops diseases crossing borders. Entomology and nematology deal with the insect and nematode pests of plants; weed science with the plants that compete with crops.

Plant biotechnology uses living plant cells and their molecules to make products and improve plants. Its tools are tissue culture (micropropagation, somatic embryogenesis, production of haploids and of secondary metabolites in cell cultures), protoplast fusion, genetic engineering (the transfer of a gene from any organism into a plant, usually by Agrobacterium or the gene gun, giving transgenic or genetically modified plants), marker-assisted selection using DNA markers, and now genome editing. Transgenic crops include Bt cotton and Bt brinjal with an insecticidal protein from Bacillus thuringiensis, herbicide-tolerant soybean, virus-resistant papaya and Golden Rice with provitamin A. Biotechnology also gives biofertilisers, biopesticides, plant-made vaccines and enzymes, and the DNA barcoding used to identify plants and detect adulteration in herbal drugs.

Pharmacognosy and phytochemistry identify and standardise plant drugs and isolate their active compounds: quinine from cinchona, morphine from opium poppy, reserpine from Rauwolfia, vincristine from periwinkle, artemisinin from Artemisia, taxol from yew. About a quarter of all prescription drugs are derived from plants.

Environmental botany and conservation biology apply ecology to the protection of vegetation and endangered species, to the restoration of degraded land, to pollution monitoring with lichens and mosses, and to the management of protected areas and seed banks. These are among the fastest growing fields of applied botany, as the loss of forests and species becomes a global concern.

Modern botany in India was built by a generation of scientists who worked in the first half of the twentieth century, often in poorly equipped laboratories, and who founded the departments, institutes and journals on which the subject still rests. The Intermediate syllabus asks for their names and contributions.

Sir Jagadish Chandra Bose (1858–1937), physicist and plant physiologist at Presidency College, Kolkata, invented extremely sensitive instruments, the crescograph, which magnified plant growth ten thousand times, and the resonant recorder, and used them to show that plants respond to stimuli such as touch, electric shock, heat and poisons with electrical signals like those of animal tissue, and that growth and movement are affected by the environment in measurable ways. He founded the Bose Institute in Kolkata in 1917 and is regarded as the father of plant physiology in India; his work on the response of plants to stimuli gave scientific form to the ancient Indian view that plants are sentient.

Birbal Sahni (1891–1949), a student of A. C. Seward at Cambridge, was the founder of palaeobotany in India. He studied the fossil plants of the Indian Gondwana rocks and of the Deccan Intertrappean beds, described the fossil gymnosperm group Pentoxyleae from the Rajmahal Hills, and worked on the fossil conifers, cycads and ferns. He was professor of botany at Lucknow University, president of the Indian National Science Academy and the first Indian botanist elected Fellow of the Royal Society. He founded the Institute of Palaeobotany at Lucknow, now the Birbal Sahni Institute of Palaeosciences, whose foundation stone was laid by Jawaharlal Nehru a week before Sahni's death in 1949.

M. O. P. Iyengar (Mandayam Osuri Parthasarathy Iyengar, 1886–1963), professor at the University of Madras, is the father of Indian phycology. He collected and described hundreds of algae from the ponds, tanks, rivers and coasts of India, discovered many new genera and species, and worked out the structure and reproduction of the green algae Volvocales and Chlorococcales and of freshwater and marine forms; he founded the school of algology at Madras that trained most Indian phycologists.

Panchanan Maheshwari (1904–1966), professor at the University of Delhi, was the leading embryologist of flowering plants of his time. His book An Introduction to the Embryology of Angiosperms (1950) became the world's standard text. He pioneered the culture of embryos, ovules and anthers in sterile media, the technique of test-tube fertilisation (intra-ovarian and in-vitro pollination), and the study of the embryo sac; his Delhi school of embryology produced hundreds of research papers and many of India's botanists. He founded the International Society of Plant Morphologists and the journal Phytomorphology.

These four, physiologist, palaeobotanist, phycologist and embryologist, mark the four corners of the science in India, and their institutes, the Bose Institute, the Birbal Sahni Institute, the Madras and Delhi departments, remain centres of research. The examination usually asks for two or three of them with their fields and one contribution each.

The founders were joined by workers who built the other branches of Indian botany.

E. K. Janaki Ammal (1897–1984), from Kerala, was the first Indian woman to earn a doctorate in botany (Michigan, 1931) and a pioneer of cytogenetics and plant breeding. At the Sugarcane Breeding Institute, Coimbatore, she worked out the chromosome numbers of sugarcane and its wild relatives and produced the first hybrids between sugarcane and other grasses, contributing to the sweet, high-yielding Indian canes; at the John Innes Institute and Royal Horticultural Society in England she co-authored the Chromosome Atlas of Cultivated Plants (1945) and studied the cytology of magnolias, roses and rhododendrons, one of which is named after her. Returning to India at Nehru's invitation, she reorganised the Botanical Survey of India, of which she became director-general, and spent her last years on the ethnobotany and cytology of medicinal plants, and in the campaign that saved the Silent Valley rainforest.

K. C. Mehta (Karm Chand Mehta, 1892–1950), professor at Agra College, was the leading plant pathologist of his generation. Over twenty years he worked out the epidemiology of the rusts of wheat in India, showing that the rust cannot survive the plains summer and re-infects the crop each winter from spores blown down from the Himalaya and the Nilgiris, where it survives on self-sown wheat and grasses. This finding, published in his monograph Further Studies on Cereal Rusts in India, made the forecasting and control of rust possible and is the basis of India's rust management to this day.

S. R. Kashyap (Shiv Ram Kashyap, 1882–1934), professor at Government College, Lahore, is the father of Indian bryology. He explored the Himalaya and the western Tibetan plateau, collecting liverworts and mosses at great altitudes, and published Liverworts of the Western Himalayas and the Panjab Plain (1929–1932), the first authoritative account of Indian bryophytes, describing many new genera and species. He was the first president of the Indian Botanical Society (1920).

Taxonomists. The flora of India was first written by British botanists: William Roxburgh, superintendent of the Calcutta garden, is called the father of Indian botany for his Flora Indica (1820–1832) and Plants of the Coast of Coromandel, the latter drawn from what is now Andhra Pradesh and Telangana; Robert Wight illustrated the plants of south India; and J. D. Hooker's Flora of British India (1872–1897) in seven volumes remains the foundation. Among Indians, K. Rangachari and J. S. Gamble produced the Flora of the Presidency of Madras (1915–1936), which covers the Telangana region, and C. E. C. Fischer completed it. Later, M. S. Swaminathan, geneticist and plant breeder, led the Green Revolution in India and founded the research foundation at Chennai that bears his name; and B. P. Pal, director of the Indian Agricultural Research Institute, bred rust-resistant wheats and was the first director-general of the Indian Council of Agricultural Research.

Institutions. The Botanical Survey of India (founded 1890 at Kolkata, with a regional circle at Hyderabad for the Deccan) surveys and records the flora of the country; the Indian Botanical Society (1920) is the professional body; the National Botanical Research Institute at Lucknow, the Central Institute of Medicinal and Aromatic Plants, the Forest Research Institute at Dehradun and the agricultural universities, including Professor Jayashankar Telangana State Agricultural University at Hyderabad, carry the applied work forward.

The value of botany rests on the value of plants to people, which is total: there is no human need that plants do not serve.

Food. Almost all human food comes from plants directly or through animals that eat plants. The cereals (rice, wheat, maize, sorghum, millets) supply starch and energy; the pulses (red gram, green gram, black gram, chickpea, lentil) supply protein; the oilseeds (groundnut, sesame, sunflower, mustard, soybean) supply fats; fruits and vegetables supply vitamins and minerals; sugarcane and sugar beet supply sugar; and tea, coffee, cocoa and spices supply flavour and stimulation. Fodder crops and pasture feed the livestock that give milk and meat.

Fibre and shelter. Cotton, jute, flax, hemp, coir and sisal give textile and cordage fibres; timber from teak, sal, deodar and rosewood gives buildings, furniture and boats; bamboo and thatch roof rural houses; paper and rayon are made from wood pulp.

Medicine. From Charaka to modern pharmacology, plants have been the chief source of drugs. Quinine (malaria), morphine and codeine (pain), digoxin (heart), reserpine (blood pressure), atropine, ephedrine, vincristine and vinblastine (leukaemia), taxol (breast cancer), artemisinin (malaria) and the steroid precursors of contraceptives all come from plants. Ayurveda, Unani and Siddha use thousands of plant drugs, and the herbal industry is a major sector of the Indian economy.

Industry. Rubber, gums, resins, tannins, dyes, waxes, essential oils, perfumes, starch, alcohol, biodiesel and the fossil fuels, coal, oil and gas, which are the remains of ancient plants, are all plant products. Bioethanol from sugarcane and biodiesel from Jatropha and pongamia are renewable plant fuels.

Environment. Plants produce the oxygen of the atmosphere and absorb carbon dioxide, moderating climate; forests regulate rainfall and river flow, prevent soil erosion and floods, and shelter wildlife; plants purify air and water, reduce noise and heat in cities, and reclaim wastelands. Mangroves protect coasts from storms; grasses bind sand dunes; trees on farm bunds hold the soil.

Culture and aesthetics. Gardens, parks, avenues, flowers in worship and ceremony, the peepal and banyan of village squares, the tulasi in the courtyard: plants are woven into Indian life and religion. Ornamental horticulture and the flower trade are large industries.

Threats and conservation. Human pressure is destroying plant diversity: forests are cleared, wetlands drained, grasslands overgrazed, and many species are threatened before they are even named. India is one of the world's twelve megadiversity countries with about 47,000 plant species, of which some 1,500 are endangered. Conservation in situ, in national parks, sanctuaries and biosphere reserves, and ex situ, in botanical gardens, seed banks and tissue culture, is the responsibility of botany in this century. In Telangana the Kawal and Amrabad tiger reserves, the Pocharam and Eturnagaram sanctuaries and the Kasu Brahmananda Reddy park protect the state's forests and their plants.

A student who continues with botany after the Intermediate course finds a wide range of careers, because every field that grows, protects, processes or studies plants needs trained botanists.

Research and teaching. Universities and colleges employ lecturers and professors; research institutes under the Council of Scientific and Industrial Research (the National Botanical Research Institute, Lucknow; the Centre for Cellular and Molecular Biology, Hyderabad; the Indian Institute of Chemical Technology, Hyderabad), the Indian Council of Agricultural Research (the Indian Agricultural Research Institute, New Delhi; the Indian Institute of Rice Research and the Indian Institute of Oilseeds Research, both at Hyderabad; the International Crops Research Institute for the Semi-Arid Tropics at Patancheru), the Department of Biotechnology and the Botanical Survey of India employ scientists in every branch. The Birbal Sahni Institute at Lucknow, the Bose Institute at Kolkata and the Indian Institutes of Science Education and Research offer research careers in palaeobotany, physiology and molecular biology.

Agriculture and allied services. Agricultural universities train agronomists, plant breeders, plant pathologists, entomologists and horticulturists; state departments of agriculture, horticulture and forestry employ officers, extension workers and forest rangers; the seed, fertiliser, pesticide and biotechnology companies of Hyderabad, one of India's seed capitals, employ breeders, molecular biologists and tissue culture specialists.

Industry and health. The pharmaceutical industry, in which Hyderabad is a national centre, employs pharmacognosists and phytochemists; the food, paper, textile, rubber, tea, coffee and sugar industries employ botanists in quality control and raw material development; the Ayurvedic and herbal industry needs plant identification and standardisation.

Environment. Environmental consultancies, pollution control boards, wildlife and forest departments, non-governmental organisations and the growing field of ecological restoration employ ecologists and taxonomists to survey vegetation, assess environmental impact and manage protected areas. Landscape architecture, nursery management and floriculture are business opportunities.

Information and communication. Bioinformatics, the handling of genome data, is now a plant science; herbaria and botanical gardens need curators; museums, publishers, science journalism and botanical illustration need people who know plants.

The future. The challenges of the twenty-first century, feeding ten billion people on less land and water, adapting crops to a warming climate, replacing fossil fuels with plant fuels and plant materials, halting the loss of species and restoring forests, are all botanical problems. The tools for solving them, genome sequencing, gene editing, remote sensing, systems biology and the vast data of digitised herbaria, are new, but the questions are those Theophrastus and Parashara asked: what is this plant, how does it live, and what is it good for? A student who masters the chapters that follow, on morphology, cell structure, the plant groups, reproduction and anatomy, will have the foundation on which any of these careers can be built.