A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Leaves are collectively referred to as foliage, as in "autumn foliage". A leaf is a thin, dorsiventrally flattened organ borne above ground and specialized for photosynthesis. In most leaves, the primary photosynthetic tissue, the palisade mesophyll, is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus, palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves have distinct upper surface and lower surface that differ in colour, the number of stomata, the amount and structure of epicuticular wax and other features. Leaves can have many different shapes and textures; the broad, flat leaves with complex venation of flowering plants are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants. In the clubmosses, with different evolutionary origins, the leaves are simple and are known as microphylls.
Some leaves, such as bulb scales, are not above ground. In many aquatic species the leaves are submerged in water. Succulent plants have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines. Furthermore, several kinds of leaf-like structures found in vascular plants are not homologous with them. Examples include flattened plant stems called phylloclades and cladodes, flattened leaf stems called phyllodes which differ from leaves both in their structure and origin; some structures of non-vascular plants function much like leaves. Examples include the phyllids of liverworts. Leaves are the most important organs of most vascular plants. Green plants are autotrophic, meaning that they do not obtain food from other living things but instead create their own food by photosynthesis, they capture the energy in sunlight and use it to make simple sugars, such as glucose and sucrose, from carbon dioxide and water. The sugars are stored as starch, further processed by chemical synthesis into more complex organic molecules such as proteins or cellulose, the basic structural material in plant cell walls, or metabolised by cellular respiration to provide chemical energy to run cellular processes.
The leaves draw water from the ground in the transpiration stream through a vascular conducting system known as xylem and obtain carbon dioxide from the atmosphere by diffusion through openings called stomata in the outer covering layer of the leaf, while leaves are orientated to maximise their exposure to sunlight. Once sugar has been synthesized, it needs to be transported to areas of active growth such as the plant shoots and roots. Vascular plants transport sucrose in a special tissue called the phloem; the phloem and xylem are parallel to each other but the transport of materials is in opposite directions. Within the leaf these vascular systems branch to form veins which supply as much of the leaf as possible, ensuring that cells carrying out photosynthesis are close to the transportation system. Leaves are broad and thin, thereby maximising the surface area directly exposed to light and enabling the light to penetrate the tissues and reach the chloroplasts, thus promoting photosynthesis.
They are arranged on the plant so as to expose their surfaces to light as efficiently as possible without shading each other, but there are many exceptions and complications. For instance plants adapted to windy conditions may have pendent leaves, such as in many willows and eucalyptss; the flat, or laminar, shape maximises thermal contact with the surrounding air, promoting cooling. Functionally, in addition to carrying out photosynthesis, the leaf is the principal site of transpiration, providing the energy required to draw the transpiration stream up from the roots, guttation. Many gymnosperms have thin needle-like or scale-like leaves that can be advantageous in cold climates with frequent snow and frost; these are interpreted as reduced from megaphyllous leaves of their Devonian ancestors. Some leaf forms are adapted to modulate the amount of light they absorb to avoid or mitigate excessive heat, ultraviolet damage, or desiccation, or to sacrifice light-absorption efficiency in favour of protection from herbivory.
For xerophytes the major constraint drought. Some window plants such as Fenestraria species and some Haworthia species such as Haworthia tesselata and Haworthia truncata are examples of xerophytes. and Bulbine mesembryanthemoides. Leaves function to store chemical energy and water and may become specialised organs serving other functions, such as tendrils of peas and other legumes, the protective spines of cacti and the insect traps in carnivorous plants such as Nepenthes and Sarracenia. Leaves are the fundamental structural units from which cones are constructed in gymnosperms and from which flowers are constructed in flowering plants; the internal organisation of most kinds of leaves has evolved to maximise exposure of the photosynthetic organelles, the chloroplasts, to light and to increase the absorption of carbon dioxide while at the same time controlling water loss. Their surfaces are waterproofed by the plant cuticle and gas exchange between the mesophyll cells and the atmosphere is controlled by minute openings called stomata which open or close to regulate the rate exchange of carbon dioxide and water vapour into
Flora is the plant life occurring in a particular region or time the occurring or indigenous—native plant life. The corresponding term for animal life is fauna. Flora and other forms of life such as fungi are collectively referred to as biota. Sometimes bacteria and fungi are referred to as flora, as in the terms gut flora or skin flora; the word "flora" comes from the Latin name of Flora, the goddess of plants and fertility in Roman mythology. The technical term "flora" is derived from a metonymy of this goddess at the end of the sixteenth century, it was first used in poetry to denote the natural vegetation of an area, but soon assumed the meaning of a work cataloguing such vegetation. Moreover, "Flora" was used to refer to the flowers of an artificial garden in the seventeenth century; the distinction between vegetation and flora was first made by Jules Thurmann. Prior to this, the two terms were used indiscriminately. Plants are grouped into floras based on region, special environment, or climate.
Regions can be distinct habitats like mountain vs. flatland. Floras can mean plant life of a historic era as in fossil flora. Lastly, floras may be subdivided by special environments: Native flora; the native and indigenous flora of an area. Agricultural and horticultural flora; the plants that are deliberately grown by humans. Weed flora. Traditionally this classification was applied to plants regarded as undesirable, studied in efforts to control or eradicate them. Today the designation is less used as a classification of plant life, since it includes three different types of plants: weedy species, invasive species, native and introduced non-weedy species that are agriculturally undesirable. Many native plants considered weeds have been shown to be beneficial or necessary to various ecosystems; the flora of a particular area or time period can be documented in a publication known as a "flora". Floras may require specialist botanical knowledge to use with any effectiveness. Traditionally they are books.
Simon Paulli's Flora Danica of 1648 is the first book titled "Flora" to refer to the plant world of a certain region. It describes medicinal plants growing in Denmark; the Flora Sinensis by the Polish Jesuit Michał Boym is another early example of a book titled "Flora". However, despite its title it covered not only plants, but some animals of the region, China and India. A published flora contains diagnostic keys; these are dichotomous keys, which require the user to examine a plant, decide which one of two alternatives given best applies to the plant. Biome — a major regional group of distinctive plant and animal communities Fauna Fauna and Flora Preservation Society Herbal Horticultural flora Megaflora Pharmacopoeia The Plant List Vegetation — a general term for the plant life of a regionCategoriesFlora by continent Flora by country Flora by region eFloras — a collection of on-line floras Chilebosque — checklist of Chilean native flora Flora of NW Europe with descriptions and a quiz to test your knowledge Flora of Australia Online Flora of New Zealand Series Online
A pulvinus is a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. Pulvini are common, for example, in members of the bean family Fabaceae and the prayer plant family Marantaceae. Pulvini may be present at the base or apex of the petiole or where the leaflets of a compound leaf are inserted into the rachis, they consist of a core of vascular tissue within a flexible, bulky cylinder of thin-walled parenchyma cells. A pulvinus is sometimes called a geniculum. Pulvinar movement is caused by changes in turgor pressure leading to a contraction or expansion of the parenchyma tissue; the response is initiated. The increased sugar concentration in the apoplast decreases the water potential and triggers the efflux of potassium ions from the surrounding cells; this is followed by an efflux of water, resulting in a sudden change of turgor pressure in the cells of the pulvinus. Aquaporins on the vacuole membrane of pulvini allow for the efflux of water that contributes to the change in turgor pressure.
The process is similar to the mechanism of stomatal closure. Common examples for pulvinar movements include the night closure movement of legume leaves and the touch response of the sensitive plant. Nyctinastic movements are controlled by the circadian clock and light signal transduction through phytochrome. Thigmonastic movements appear to be regulated through electrical and chemical signal transduction spreading the stimulus throughout the plant. In Mimosa pudica, the internal biological clock mediates the closing of leaflets at night and opening during day. Seismonastic or rapid movement of leaves is triggered in response temperature; the pulvinus is located at the base of each leaflet of the plant. Mechanical stimulation via touch is perceived and is translated to electrical stimulation causing the flow of ions out of the pulvinus cells. An upregulation of aquaporin and H+ - ATPase allows for the rapid flux of water out of these motor cells. Water flux out of the cells results in a decrease in turgor pressure, the characteristic closing of the leaves of Mimosa pudica.
The drop in turgor pressure is slow. Leaves open to their initial position after 20 minutes of lack of stimulation, it has been demonstrated. Using nuclear magnetic resonance, upward movement of water within the pulvinus joint in response to electrical stimulation was observed in the pulvinus at the base of the petiole. Movement of water to the upper or lower part of the pulvinus causes asymmetric swelling therefore causing the petiole to either droop or rise and contributing to the characteristic displacement of the petioles; the transmittance of internal electrical and chemical signals cause changes in the pulvinus which allows M. pudica to respond accordingly to touch stimuli. P. H. Raven, R. F. Evert, S. E. Eichhorn: Biology of Plants, 7th Edition, W. H. Freeman and Company Publishers, New York, ISBN 0-7167-1007-2
International Standard Book Number
The International Standard Book Number is a numeric commercial book identifier, intended to be unique. Publishers purchase ISBNs from an affiliate of the International ISBN Agency. An ISBN is assigned to each variation of a book. For example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN; the ISBN is 13 digits long if assigned on or after 1 January 2007, 10 digits long if assigned before 2007. The method of assigning an ISBN is nation-based and varies from country to country depending on how large the publishing industry is within a country; the initial ISBN identification format was devised in 1967, based upon the 9-digit Standard Book Numbering created in 1966. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO 2108. Published books sometimes appear without an ISBN; the International ISBN agency sometimes assigns such books ISBNs on its own initiative.
Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines and newspapers. The International Standard Music Number covers musical scores; the Standard Book Numbering code is a 9-digit commercial book identifier system created by Gordon Foster, Emeritus Professor of Statistics at Trinity College, for the booksellers and stationers WHSmith and others in 1965. The ISBN identification format was conceived in 1967 in the United Kingdom by David Whitaker and in 1968 in the United States by Emery Koltay; the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO 2108. The United Kingdom continued to use the 9-digit SBN code until 1974. ISO has appointed the International ISBN Agency as the registration authority for ISBN worldwide and the ISBN Standard is developed under the control of ISO Technical Committee 46/Subcommittee 9 TC 46/SC 9; the ISO on-line facility only refers back to 1978.
An SBN may be converted to an ISBN by prefixing the digit "0". For example, the second edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has "SBN 340 01381 8" – 340 indicating the publisher, 01381 their serial number, 8 being the check digit; this can be converted to ISBN 0-340-01381-8. Since 1 January 2007, ISBNs have contained 13 digits, a format, compatible with "Bookland" European Article Number EAN-13s. An ISBN is assigned to each variation of a book. For example, an ebook, a paperback, a hardcover edition of the same book would each have a different ISBN; the ISBN is 13 digits long if assigned on or after 1 January 2007, 10 digits long if assigned before 2007. An International Standard Book Number consists of 4 parts or 5 parts: for a 13-digit ISBN, a prefix element – a GS1 prefix: so far 978 or 979 have been made available by GS1, the registration group element, the registrant element, the publication element, a checksum character or check digit. A 13-digit ISBN can be separated into its parts, when this is done it is customary to separate the parts with hyphens or spaces.
Separating the parts of a 10-digit ISBN is done with either hyphens or spaces. Figuring out how to separate a given ISBN is complicated, because most of the parts do not use a fixed number of digits. ISBN is most used among others special identifiers to describe references in Wikipedia and can help to find the same sources with different description in various language versions. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency, responsible for that country or territory regardless of the publication language; the ranges of ISBNs assigned to any particular country are based on the publishing profile of the country concerned, so the ranges will vary depending on the number of books and the number and size of publishers that are active. Some ISBN registration agencies are based in national libraries or within ministries of culture and thus may receive direct funding from government to support their services. In other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded.
A full directory of ISBN agencies is available on the International ISBN Agency website. Partial listing: Australia: the commercial library services agency Thorpe-Bowker.
Botany called plant science, plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist; the term "botany" comes from the Ancient Greek word βοτάνη meaning "pasture", "grass", or "fodder". Traditionally, botany has included the study of fungi and algae by mycologists and phycologists with the study of these three groups of organisms remaining within the sphere of interest of the International Botanical Congress. Nowadays, botanists study 410,000 species of land plants of which some 391,000 species are vascular plants, 20,000 are bryophytes. Botany originated in prehistory as herbalism with the efforts of early humans to identify – and cultivate – edible and poisonous plants, making it one of the oldest branches of science. Medieval physic gardens attached to monasteries, contained plants of medical importance, they were forerunners of the first botanical gardens attached to universities, founded from the 1540s onwards.
One of the earliest was the Padua botanical garden. These gardens facilitated the academic study of plants. Efforts to catalogue and describe their collections were the beginnings of plant taxonomy, led in 1753 to the binomial system of Carl Linnaeus that remains in use to this day. In the 19th and 20th centuries, new techniques were developed for the study of plants, including methods of optical microscopy and live cell imaging, electron microscopy, analysis of chromosome number, plant chemistry and the structure and function of enzymes and other proteins. In the last two decades of the 20th century, botanists exploited the techniques of molecular genetic analysis, including genomics and proteomics and DNA sequences to classify plants more accurately. Modern botany is a broad, multidisciplinary subject with inputs from most other areas of science and technology. Research topics include the study of plant structure and differentiation, reproduction and primary metabolism, chemical products, diseases, evolutionary relationships and plant taxonomy.
Dominant themes in 21st century plant science are molecular genetics and epigenetics, which are the mechanisms and control of gene expression during differentiation of plant cells and tissues. Botanical research has diverse applications in providing staple foods, materials such as timber, rubber and drugs, in modern horticulture and forestry, plant propagation and genetic modification, in the synthesis of chemicals and raw materials for construction and energy production, in environmental management, the maintenance of biodiversity. Botany originated as the study and use of plants for their medicinal properties. Many records of the Holocene period date early botanical knowledge as far back as 10,000 years ago; this early unrecorded knowledge of plants was discovered in ancient sites of human occupation within Tennessee, which make up much of the Cherokee land today. The early recorded history of botany includes many ancient writings and plant classifications. Examples of early botanical works have been found in ancient texts from India dating back to before 1100 BC, in archaic Avestan writings, in works from China before it was unified in 221 BC.
Modern botany traces its roots back to Ancient Greece to Theophrastus, a student of Aristotle who invented and described many of its principles and is regarded in the scientific community as the "Father of Botany". His major works, Enquiry into Plants and On the Causes of Plants, constitute the most important contributions to botanical science until the Middle Ages seventeen centuries later. Another work from Ancient Greece that made an early impact on botany is De Materia Medica, a five-volume encyclopedia about herbal medicine written in the middle of the first century by Greek physician and pharmacologist Pedanius Dioscorides. De Materia Medica was read for more than 1,500 years. Important contributions from the medieval Muslim world include Ibn Wahshiyya's Nabatean Agriculture, Abū Ḥanīfa Dīnawarī's the Book of Plants, Ibn Bassal's The Classification of Soils. In the early 13th century, Abu al-Abbas al-Nabati, Ibn al-Baitar wrote on botany in a systematic and scientific manner. In the mid-16th century, "botanical gardens" were founded in a number of Italian universities – the Padua botanical garden in 1545 is considered to be the first, still in its original location.
These gardens continued the practical value of earlier "physic gardens" associated with monasteries, in which plants were cultivated for medical use. They supported the growth of botany as an academic subject. Lectures were given about the plants grown in the gardens and their medical uses demonstrated. Botanical gardens came much to northern Europe. Throughout this period, botany remained subordinate to medicine. German physician Leonhart Fuchs was one of "the three German fathers of botany", along with theologian Otto Brunfels and physician Hieronymus Bock. Fuchs and Brunfels broke away from the tradition of copying earlier works to make original observations of their own. Bock created his own system of plant classification. Physician Valerius Cordus authored a botanically and pharmacologically important herbal Historia Plantarum in 1544 and a pharmacopoeia of lasting importance, the Dispensatorium
The Fabaceae or Leguminosae known as the legume, pea, or bean family, are a large and economically important family of flowering plants. It includes trees and perennial or annual herbaceous plants, which are recognized by their fruit and their compound, stipulate leaves. Many legumes have characteristic fruits; the family is distributed, is the third-largest land plant family in terms of number of species, behind only the Orchidaceae and Asteraceae, with about 751 genera and about 19,000 known species. The five largest of the genera are Astragalus, Indigofera and Mimosa, which constitute about a quarter of all legume species; the ca. 19,000 known legume species amount to about 7% of flowering plant species. Fabaceae is the most common family found in tropical rainforests and in dry forests in the Americas and Africa. Recent molecular and morphological evidence supports the fact that the Fabaceae is a single monophyletic family; this conclusion has been supported not only by the degree of interrelation shown by different groups within the family compared with that found among the Leguminosae and their closest relations, but by all the recent phylogenetic studies based on DNA sequences.
These studies confirm that the Fabaceae are a monophyletic group, related to the Polygalaceae and Quillajaceae families and that they belong to the order Fabales. Along with the cereals, some fruits and tropical roots, a number of Leguminosae have been a staple human food for millennia and their use is related to human evolution; the Fabaceae family includes a number of important agricultural and food plants, including Glycine max, Pisum sativum, Cicer arietinum, Medicago sativa, Arachis hypogaea, Ceratonia siliqua, Glycyrrhiza glabra. A number of species are weedy pests in different parts of the world, including: Cytisus scoparius, Robinia pseudoacacia, Ulex europaeus, Pueraria lobata, a number of Lupinus species; the name'Fabaceae' comes from the defunct genus Faba, now included in Vicia. The term "faba" comes from Latin, appears to mean "bean". Leguminosae is an older name still considered valid, refers to the fruit of these plants, which are called legumes. Fabaceae range in habit from giant trees to small annual herbs, with the majority being herbaceous perennials.
Plants have indeterminate inflorescences. The flowers have a short hypanthium and a single carpel with a short gynophore, after fertilization produce fruits that are legumes; the Leguminosae have a wide variety of growth forms, including trees, herbaceous plants, vines or lianas. The herbaceous plants can be annuals, biennials, or perennials, without basal or terminal leaf aggregations. Many Legumes have tendrils, they are epiphytes, or vines. The latter support themselves by means of shoots that twist around a support or through cauline or foliar tendrils. Plants can be mesophytes, or xerophytes; the leaves are alternate and compound. Most they are even- or odd-pinnately compound trifoliate and palmately compound, in the Mimosoideae and the Caesalpinioideae bipinnate, they always have stipules, which can be rather inconspicuous. Leaf margins are entire or serrate. Both the leaves and the leaflets have wrinkled pulvini to permit nastic movements. In some species, leaflets have evolved into tendrils.
Many species have leaves with structures that attract ants that protect the plant from herbivore insects. Extrafloral nectaries are common among the Mimosoideae and the Caesalpinioideae, are found in some Faboideae. In some Acacia, the modified hollow stipules are known as domatia. Many Fabaceae host bacteria in their roots within structures called root nodules; these bacteria, known as rhizobia, have the ability to take nitrogen gas out of the air and convert it to a form of nitrogen, usable to the host plant. This process is called nitrogen fixation; the legume, acting as a host, rhizobia, acting as a provider of usable nitrate, form a symbiotic relationship. The flowers have five fused sepals and five free petals, they are hermaphrodite, have a short hypanthium cup shaped. There are ten stamens and one elongated superior ovary, with a curved style, they are arranged in indeterminate inflorescences. Fabaceae are entomophilous plants, the flowers are showy to attract pollinators. In the Caesalpinioideae, the flowers are zygomorphic, as in Cercis, or nearly symmetrical with five equal petals in Bauhinia.
The upper petal is the innermost one, unlike in the Faboideae. Some species, like some in the genus Senna, have asymmetric flowers, with one of the lower petals larger than the opposing one, the style bent to one side; the calyx, corolla, or stamens can be showy in this group. In the Mimosoideae, the flowers are actinomorphic and arranged in globose inflorescences; the petals are small and the stamens, which can be more than just 10, have long, coloured filaments, which are the showiest part of the flower. All of the flowers in an inflorescence open at once. In the Faboideae, the flowers are zygom