The study of plant uses by people is termed economic botany or ethnobotany; some consider economic botany to focus on modern cultivated plants, while ethnobotany focuses on indigenous plants cultivated and used by native peoples. Human cultivation of plants is part of agriculture, which is the basis of human civilization. Plant agriculture is subdivided into agronomy, horticulture and forestry. Foods and beverages Much of human nutrition depends on plants, either directly through foods and beverages consumed by people, or indirectly as feed for animals or the flavoring of foods. The science of agriculture deals with the planting, raising, nutrition, and harvest of food crops, and has played a key role in the history of world civilizations.Human nutrition depends to a large extent on cereals, especially maize (or corn), wheat, rice, oats, and millet. Large areas of many countries are given over to the cultivation of cereals for local consumption or export to other countries. Livestock animals including cows, pigs, sheep, goats and camels are all herbivores; and most feed primarily or entirely on cereal plants. Cereals are staple crops, meaning that they provide calories (in the form of complex carbohydrates such as starch) that are needed to fuel daily activities, and thus form the foundation of a daily diet. Other staple crops include potatoes, cassava, yams, and legumes.Human food also includes vegetables, which consist principally of leaves and stems eaten as food. Vegetables are important for the vitamins, minerals, and dietary fiber they supply. Fruits provide a higher quantity of sugars and have a sweeter taste than vegetables. However, whether a particular food is considered a "vegetable" or a "fruit" will depend on context, since the word fruit has a more precise definition in botany than it does in general use. Nuts and seeds, including foods such as peanuts, almonds, and pistachios, contain unsaturated fats that are also necessary for a healthy diet. As with fruits, the terms nut and seed have stricter definitions in plant science.Many plants are used to flavor foods. Such plants include herbs (e.g. rosemary and mint), which come from the green leafy parts of plants, and spices (e.g. cumin and cinnamon), which come from other plant parts. Some plants produce edible flowers, which may be added to salads or used to decorate foods. Sweeteners such as sugar and honey are derived from plants. Sugar is obtained mainly from sugar cane and sugar beet, and honey comes from flowers. Cooking oils and margarine come from maize, soybean, rapeseed, safflower, sunflower, olive and others. Food additives include gum arabic, guar gum, locust bean gum, starch and pectin.Plants are also the source of beverages produced either by infusion, such as coffee and tea; by fermentation, such as beer and wine; or by distillation, such as whisky, vodka, rum, and other alcoholic spirits. Nonfood productsPlants are the source of many natural products such as essential oils, natural dyes, pigments, waxes, resins, tannins, alkaloids, amber and cork. Products derived from plants include soaps, shampoos, perfumes, cosmetics, paint, varnish, turpentine, rubber, latex, lubricants, linoleum, plastics, inks, and gums. Renewable fuels from plants include firewood, peat and many other biofuels. Coal and petroleum are fossil fuels derived from the remains of plants. Olive oil has been used in lamps for centuries to provide illumination.Structural resources and fibers from plants are used in both the construction of dwellings and the manufacture of clothing. Wood is used not only for buildings, boats, and furniture, but also for smaller items such as musical instruments and sports equipment. Wood also may be pulped for the manufacture of paper and cardboard. Cloth is often made from cotton, flax, rame or synthetic fibers derived from cellulose, such as rayon and acetate. The thread that is used to sew cloth likewise comes from plant fibers. Hemp and jute are grown for their fibers, which may be woven into rope or rough sacking.Plants are also a primary source of basic chemicals, both for their medicinal and physiological effects, as well as for the industrial synthesis of a vast array of organic chemicals. Medicines derived from plants include aspirin, taxol, morphine, quinine, reserpine, colchicine, digitalis and vincristine. There are hundreds of herbal supplements such as ginkgo, Echinacea, feverfew, and Saint John's wort. Pesticides derived from plants include nicotine, rotenone, strychnine and pyrethrins. Certain plants contain psychotropic chemicals which are extracted and ingested, including tobacco, cannabis (marijuana), opium, and cocaine. Poisons from plants include ricin, hemlock and curare. Aesthetic uses
Thousands of plant species are cultivated for aesthetic purposes as well as to provide shade, modify temperatures, reduce wind, abate noise, provide privacy, and prevent soil erosion. Plants are the basis of a multi-billion dollar per year tourism industry which includes travel to historic gardens, national parks, rainforests, forests with colorful autumn leaves, and the National Cherry Blossom Festival.While some gardens are planted with food crops, many are planted for aesthetic, ornametal, or conservational purposes. Arboretums and botanical gardens are public collections of living plants. In private outdoor gardens, lawn grasses, shade trees, ornamental trees, shrubs, vines, herbaceous perennials and bedding plants are used. Gardens may cultivate the plants in a naturalistic state, or may sculpture their growth, as with topiary or espalier. Gardening is the most popular leisure activity in the U.S., and working with plants or horticulture therapy is beneficial for rehabilitating people with disabilities.Plants may also be grown or kept indoors as houseplants, or in specialized buildings such as greenhouses that are designed for the care and cultivation of living plants. Venus Flytrap, sensitive plant and resurrection plant are examples of plants sold as novelties. There are also art forms specilaizing in the arrangement of cut or living plant, such as bonsai, ikebana, and the arrangement of cut or dried flowers. Ornamental plants have sometimes changed the course of history, as in tulipomania.Architectural designs resembling plants appear in the capitals of ancient Egyptian columns, which were carved to resemble either the Egyptian white lotus or the papyrus. Images of plants are often used in painting and photography, as well as on textiles, money, stamps, flags and coats of arms. Scientific and cultural usesBasic biological research has often been done with plants. In genetics, the breeding of pea plants allowed Gregor Mendel to derive the basic laws governing inheritance, and examination of chromosomes in maize allowed Barbara McClintock to demonstrate their connection to inherited traits. The tiny plant Arabidopsis thaliana is used in laboratories as a model organism to understand how genes control the growth and development of plant structures. Space stations or space colonies may one day rely on plants for life support.Ancient trees are revered and many are famous. Tree rings themselves are an important method of dating in archeology, and serve as a record of past climates.Plants figure prominently in mythology, religion and literature. They are used as national and state emblems, including state trees and state flowers. Plants are often used as memorials, gifts and to mark special occasions such as births, deaths, weddings and holidays. The arrangement of flowers may be used to send hidden messages.The field of ethnobotany studies plant use by indigenous cultures which helps to conserve endangered species as well as discover new medicinal plants. Negative effectsWeeds are uncultivated and usually unwanted plants growing in managed environments such as farms, urban areas, gardens, lawns, and parks. People have spread plants beyond their native ranges and some of these introduced plants become invasive, damaging existing ecosystems by displacing native species. Invasive plants cause costly damage in crop losses annually by displacing crop plants, they further increase the cost of production and the use of chemicals to control them, which in turn affects the environment.Plants may cause harm to animals, including people. Plants that produce windblown pollen invoke allergic reactions in people who suffer from hay fever. A wide variety of plants are poisonous. Toxalbumins are plant poisons fatal to most mammals and act as a serious deterrent to consumption. Several plants cause skin irritations when touched, such as poison ivy. Certain plants contain psychotropic chemicals, which are extracted and ingested or smoked, including tobacco, cannabis (marijuana), cocaine and opium. Smoking causes damage to health or even death, while some drugs may also be harmful or fatal to people. Both illegal and legal drugs derived from plants may have negative effects on the economy, affecting worker productivity and law enforcement costs. Some plants cause allergic reactions when ingested, while other plants cause food intolerances that negatively affect health.