Botanical research has long had relevance to the understanding of fundamental biological processes other than just botany. Fundamental life processes such as cell division and protein synthesis can be studied using plants without the moral issues that come with conducting studies upon animals or humans. Gregor Mendel discovered the genetic laws of inheritance in this fashion by studying Pisum sativum (pea) inherited traits such as shape. What Mendel learned from studying plants has had far reaching benefits outside of botany. Similarly, 'jumping genes' were discovered by Barbara McClintockwhile she was studying maize.
Medicine and materials
Many medicinal and recreational drugs, like tetrahydrocannabinol, caffeine, and nicotine come directly from the plant kingdom. Others are simplederivatives of botanical natural products; for example, the pain killer aspirin is derived from salicylic acid which originally came from the bark of willowtrees. As well, the narcotic analgesics such as morphine are derived from the opium poppy. There may be many novel cures for diseases provided by plants, waiting to be discovered. Popular stimulants like coffee, chocolate, tobacco, and tea also come from plants. Most alcoholic beverages come from fermenting plants such as barley (beer), rice (sake) and grapes (wine).
Hemp, cotton, wood, paper, linen, vegetable oils, some types of rope, and rubber are examples of materials made from plants. Silk can only be made by using the mulberry plant. Sugarcane,rapeseed, soy are some of the plants with a highly fermentable sugar or oil content which have recently been put to use as sources of biofuels, which are important alternatives to fossil fuels (seebiodiesel).
The biology of a population is greater than the collective biologies of its individuals. Multiple members of the same species in close proximity constitute a population. Different populations in proximity constitute a community, which in conjunction with its nonliving environment constitute an ecosystem. The relation of each organism to all other organisms and factors in its habitat and environment make up its ecology. This includes structure, genetics and mutations, metabolism, diversity, fitness, adaptation, climate, water, and soil condition. The conditions that constitute an organisms life cycle is its habitat. Both negative and beneficial interactions with other organisms are parts of a plant's ecology. Herbivores eat plants, but plants can also defend themselves. Some other organisms form beneficial relationships with plants, called mutualisms, for example with mycorrhizal fungi that provide nutrients, and honey bees that pollinate flowers. A biome is a large part of the earth that has very similar abiotic and biotic factors, climate, and geography, creating a typical ecosystem over that area that is characterized by its dominant plants. Examples include tundra and tropical rainforest.
DNA provides the information for a plant's structure, metabolism, and biology. Genetics is the science of inheritance and the gene is its chemical unit. The same basic laws of genetics apply to both plants and animals. In sexual reproduction, offspring are often more fit than either parent since the stronger genes tend to be passed on to the next generation. Mutations and natural selection result in a species acquiring new traits and eventually evolving into one or more new species. Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. Changes can also be caused by natural events such as a large meteor hitting Earth and selective breeding (artificial selection) of plants by humans for specific traits.
Since the mid-20th century, there has been considerable debate over how the earliest forms of life evolved and how to classify them, especially at the kingdom and domain levels and organisms that are or have been considered bacteria. For example, the three-domain system separates Archaea and Bacteria, previously grouped into the single kingdom Monera (bacteria). Archaea was separated because it was shown to have a different evolutionary history. However, Thomas Cavalier-Smith rejects the three-domain system and places the Archaea as a subkingdom of Bacteria. Cyanobacteria were once believed to be related to algae and hence studied by botanists. Even now they are studied by both botanists and bacteriologists. Similarly, the Fungi (or Myceteae) were once considered plants but there is now uncertainty about how to classify them.
The various divisions of algae are also taxonomically problematic as some are more clearly linked to plants than others. Their many differences in features such as biochemistry, pigmentation, and nutrient reserves show that they diverged very early in evolutionary time. The division Chlorophyta (green algae) is considered the ancestor of true plants.
Nonvascular plants are embryophytes that do not have vascular tissue: mosses, liverworts, and hornworts. Many plants that are called "moss" are not true mosses. For example, Spanish moss(Tillandsia usneoides) is actually in the Bromeliaceae (pineapple) family. Nonvascular plants do not have xylem nor phloem. After the development of xylem and phloem, vascualar plants developed along two lines: cryptogams which reproduce by spores and which developed first, and spermatophytes, which reproduce by seed. The spermatophytes further developed intogymnosperms, plants that produce seeds not enclosed in an ovary. Modern gymnosperms include conifers, cycads, Ginkgo, and Gnetales. Gymnosperms are the ancestors of the Angiospermsor flowering plants which produce a seed encased in a structure such as a carpel.
Plant physiology encompasses all the internal chemical and physical activities of plants associated with life. Sunlight, either through photosynthesis or cellular respiration, is the basis of all life. Photoautotrophs gather energy directly from sunlight. This includes all green plants,cyanobacteria and other bacteria that can photosynthesize. Heterotrophs take in organic molecules and respire them. This includes all animals, all fungi, all completely parasitic plants, and non-photosynthetic bacteria. Respiration is the oxidation of carbon whereby it is broken down into simpler structures; essentially the opposite of photosynthesis.
Transport processes are those by which molecules are moved within the organism, such as: membranes transporting material across themselves and enzymes moving electrons. This is how minerals and water get from roots to other parts of the plant. Diffusion, osmosis, and active transport are different ways transport can occur. Examples of elements that plants need are: nitrogen, phosphorus, calcium, magnesium, and sulphur. Chemicals from the air, soil, and water in combination with sunlight form the basis of plant metabolism. Most of these elements come from minerals in a process called mineral nutrition. Few plants live in stable unchanging environments. Most plants must adapt to a variety of environmental factors, including changes in temperature, light and moisture. The better a plant can cope with these changing conditions, the more likely it is to be able to survive over both the short and long term as well as establish itself over a wider geographic range.
Plant anatomy is the study of the internal cells and tissues of a plant; whereas plant morphology is the study of their general and external form.
Understanding the structure and function of cells is fundamental to all of the biological sciences. All organisms have cells, the cell types are unique and their nuclei store most of the DNA. Cell biology studies their structural and physiological properties. This includes responses to stimuli, reproduction, and development on themacroscopic scale, microscopic scale, and molecular level. The similarities and differences between the function of a cell are quite varied. Plant cells are eukaryotic, i.e., have a membrane-encased nucleus that carries genetic material. With rare exceptions, plant cells also have a central vacuole, cytoplasm, cytosol, dictyosomes,endoplasmic reticulum, microbodies, microfilaments, microtubules, mitochondria, plasma membrane, plastids, protoplasm, ribosomes, storage products, and a cell wall. Cells divide by processes known as karyokinesis and cytokinesis.
The body of a plant contains three basic parts: roots, stems, and leaves. Roots anchor it to the ground, gather water and mineral nutrients from the soil, and produce hormones. Roots which spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. Fleshy taproots, such as those of beets and carrots, store carbohydrates. Stems provide support to the leaves and store nutrients. Leaves gather sunlight and begin photosynthesis. Large, flat, flexible, green leaves are called foliage leaves. Gymnosperms are seed-producing plants which have open seeds, such as conifers, cycads, Ginkgo, andgnetophyta. Angiosperms are seed-producing plants that produce flowers, having enclosed seeds. Some of the gymnosperms became the ancestors of the angiosperms. Woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues: wood (secondary xylem) and bark (secondary phloem and cork). All gymnosperms and many angiosperms are woody plants. Some plants reproduce sexually, some asexually, and some via both means.
Scientific classification in botany is a method by which botanists group and categorize organisms by biological type, such as genus or species. Biological classification is a form of scientific taxonomy. Modern taxonomy is rooted in the work of Carolus Linnaeus, who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the Darwinian principle of common descent. While scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses DNA sequences as data, has driven many recent revisions along more efficient, evolutionary lines and is likely to continue to do so. Botanical classification belongs to the science of plant systematics. The dominant classification system is called the Linnaean taxonomy. It includes ranks and binomial nomenclature. The classification,taxonomy, and nomenclature of botanical organisms is administered by the International Code of Nomenclature for algae, fungi, and plants (ICN).
The five-kingdom system has largely been superseded by modern alternative classification systems. Textbooks generally begin with the three-domain system: Archaea (originally Archaebacteria); Bacteria (originally Eubacteria); Eukaryota (including protists, fungi, plants, and animals). These domains reflect whether the cells have nuclei or not, as well as differences in the chemical composition of the cell exteriors and ribosomes.
Further, each kingdom is broken down recursively until each species is separately classified. The order is: Domain; Kingdom; Phylum; Class; Order;Family; Genus; Species. The scientific name of an organism is generated from its genus and species, resulting in a single world-wide name for each organism. For example, the Tiger Lily is listed as Lilium columbianum. Lilium is the genus, and columbianum the specific epithet. When writing the scientific name of an organism, it is proper to capitalize the first letter in the genus and put all of the specific epithet in lowercase. Additionally, the entire term is ordinarily italicized or underlined.Phylogenetics is the study of similarities among different species.