In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more they represent problematic species concepts. For example, the boundaries between related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, in a ring species. Among organisms that reproduce only asexually, the concept of a reproductive species breaks down, each clone is a microspecies. All species are given a two-part name, a "binomial"; the first part of a binomial is the genus.
The second part is called the specific epithet. For example, Boa constrictor is one of four species of the genus Boa. None of these is satisfactory definitions, but scientists and conservationists need a species definition which allows them to work, regardless of the theoretical difficulties. If species were fixed and distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, to grade into one another. Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped. Charles Darwin's 1859 book The Origin of Species explained how species could arise by natural selection; that understanding was extended in the 20th century through genetics and population ecology. Genetic variability arises from mutations and recombination, while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures.
Genes can sometimes be exchanged between species by horizontal gene transfer. Viruses are a special case, driven by a balance of mutation and selection, can be treated as quasispecies. Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics. Early taxonomists such as Linnaeus had no option but to describe what they saw: this was formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts, is hard or impossible to test. Biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: agamospecies for asexual organisms biospecies for reproductively isolated sexual organisms ecospecies based on ecological niches evolutionary species based on lineage genetic species based on gene pool morphospecies based on form or phenotype and taxonomic species, a species as determined by a taxonomist.
A typological species is a group of organisms in which individuals conform to certain fixed properties, so that pre-literate people recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens would differentiate the species; this method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, different phenotypes are not different species. Species named in this manner are called morphospecies. In the 1970s, Robert R. Sokal, Theodore J. Crovello and Peter Sneath proposed a variation on this, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms, it differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species is a group of sexually reproducing organisms that recognize one another as potential mates.
Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms. A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology, genes can move even between distantly related bacteria extending to the whole bacterial domain; as a rule of thumb, microbiologists have assumed that kinds of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA-DNA hybridisation to decide if they belong to the same species or not. This concept was narrowed in 2006 to a similarity of 98.7%. DNA-DNA hybri
Herbaceous plants are plants that have no persistent woody stem above ground. The term is applied to perennials, but in botany it may refer to annuals or biennials, include both forbs and graminoids. Annual herbaceous plants die at the end of the growing season or when they have flowered and fruited, they grow again from seed. Herbaceous perennial and biennial plants may have stems that die at the end of the growing season, but parts of the plant survive under or close to the ground from season to season. New growth develops from living tissues remaining on or under the ground, including roots, a caudex or various types of underground stems, such as bulbs, stolons and tubers. Examples of herbaceous biennials include carrot and common ragwort. By contrast, non-herbaceous perennial plants are woody plants which have stems above ground that remain alive during the dormant season and grow shoots the next year from the above-ground parts – these include trees and vines; some fast-growing herbaceous plants are pioneers, or early-successional species.
Others form the main vegetation of many stable habitats, occurring for example in the ground layer of forests, or in open habitats such as meadow, salt marsh or desert. Some herbaceous plants can grow rather large, such as the genus Musa; the age of some herbaceous perennial plants can be determined by herbchronology, the analysis of annual growth rings in the secondary root xylem
Plant propagation is the process of growing new plants from a variety of sources: seeds and other plant parts. Plant propagation can refer to the artificial or natural dispersal of plants. Seeds and spores can be used for reproduction. Seeds are produced from sexual reproduction within a species, because genetic recombination has occurred. A plant grown from seeds may have different characteristics from its parents; some species produce seeds, such as cold treatment. The seeds of many Australian plants and plants from southern Africa and the American west require smoke or fire to germinate; some plant species, including many trees, do not produce seeds until they reach maturity, which may take many years. Seeds can be difficult to acquire and some plants do not produce seed at all; some plants may produce not fertile seed. In certain cases, this is done to prevent the accidental spreading of these plants, for example by birds and other animals. Plants have a number of mechanisms for vegetative reproduction.
Some of these have been taken advantage of by horticulturists and gardeners to multiply or clone plants rapidly. Humans may utilize these processes as propagation methods, such as tissue grafting. Plants are produced using material from a single parent and as such there is no exchange of genetic material, therefore vegetative propagation methods always produce plants that are identical to the parent. Vegetative reproduction uses plants parts such as roots and leaves. In some plants seeds can be produced without fertilization and the seeds contain only the genetic material of the parent plant. Therefore, propagation via asexual seeds or apomixis is asexual reproduction but not vegetative propagation. Techniques for vegetative propagation include: Air or ground layering Division Grafting and bud grafting used in fruit tree propagation Micropropagation Stolons or runners Storage organs such as bulbs, corms and rhizomes Striking or cuttings Twin-scaling Offsets A heated propagator is a horticultural device to maintain a warm and damp environment for seeds and cuttings to grow in.
This can be in the form of a clear enclosed bin sitting over a hotpad, or a portable heater pointed at the bin. The key is to keep the moisture in the clear bin, while keeping lighting over the top of it, usually. An electric seed-propagation mat is a heated rubber mat covered by a metal cage, used in gardening; the mats are made so that planters containing seedlings can be placed on top of the metal cage without the risk of starting a fire. In extreme cold, gardeners place a loose plastic cover over the planters/mats which creates a sort of miniature greenhouse; the constant and predictable heat allows people to garden in the winter months when the weather is too cold for seedlings to survive naturally. When combined with a lighting system, many plants can be grown indoors using these mats. Adventitious Clonal colony Fruit tree propagation Orthodox seed Recalcitrant seed Selection methods in plant breeding based on mode of reproduction Propagation of grapevines Weeping willow is an ornamental tree (Salix babylonica and related hybrids.
<http://aggie-horticulture.tamu.edu/ornamental/a-reference-guide-to-plant-care-handling-and-merchandising/propagating-foliage-flowering-plants/>. Charles W. Heuser; the Complete Book of Plant Propagation, Taunton Press, 1997. ISBN 1561582344
Award of Garden Merit
The Award of Garden Merit is a long-established annual award for plants by the British Royal Horticultural Society. It is based on assessment of the plants' performance under UK growing conditions; the Award of Garden Merit is a mark of quality awarded, since 1922, to garden plants by the United Kingdom, Royal Horticultural Society. Awards are made annually after plant trials intended to judge the plants' performance under UK growing conditions. Trials may last for one or more years, depending on the type of plant being tried out, may be performed at Royal Horticulture Society Garden in Wisley and other gardens or after observation of plants in specialist collections. Trial reports are made available on the website. Awards are reviewed annually in case plants have become unavailable horticulturally, or have been superseded by better cultivars; the award should not be confused with the Royal Horticulture Society's Award of Merit, given to plants deemed'of great merit for exhibition' i.e. for show, not garden, plants.
Since 1989, France has had similar awards called the Mérites de Courson, but these are drawn from a limited number of plants submitted by nurserymen to juries at the twice-yearly Journées des Plantes de Courson and awards are based on the opinions of the jury members as to the plants' performance in French gardens, rather than on extensive trials. The Award of Garden Merit was reviewed in 1992, to increase its prestige. Field trial results gained weight in the assessments and existing AGM plants were reviewed in the light of more recent experience; the AGMs were to be reviewed at 10 year intervals from 1992, but this frequency has been increased to annually. The 2012/13 review, with advice from experts such as Royal Horticultural Society's plant committees, specialist societies, Plant Heritage National Collection holders and others, resulted in many changes. Nearly 1,900 plants lost more than 1,400 plants gained awards. Plants may be added to the Royal Horticultural Society'Sunset List' for rescission for several reasons, including unavailability to gardeners, better plants becoming available, affliction by pests or diseases, or insufficient uniformity.
To qualify for an Award of Garden Merit, a plant must be available horticulturally must be of outstanding excellence for garden decoration or use must be of good constitution must not require specialist growing conditions or care must not be susceptible to any pest or disease must not be subject to an unreasonable degree of reversion. The "Award of Garden Merit" symbol represents a cup-shaped trophy with handles, it is cited together with a hardiness rating as follows: H1 Requires a heated glasshouse H1a Warmer than 15C/59F: tropical plants for indoors and heated greenhouses H1b 10C/50F to 15C/59F: subtropical plants for indoors and heated greenhouses H1c 5C/41F to 10C/50F: warm temperate plants that can go outdoors in summer H2 1C/34F to 5C/41F: plants that need a frost-free greenhouse in winter H3 -5C/23F to 1C/34F: hardy outside in some regions or situations, or which - while grown outside in summer - need frost protection in winter H4 -10C/14F to -5C/23F: plants hardy outside in most of the UK in an average winter H5 -15C/5F to -10C/14F: plants hardy outside in most of the UK in severe winters H6 -20C/-4F to -15C/5F: plants hardy outside in the UK and northern Europe H7 Colder than -20C/-4F: plants hardy outside in the severest European climates List of Award of Garden Merit flowering cherries List of Award of Garden Merit magnolias List of Award of Garden Merit roses List of Award of Garden Merit sweet peas RHS Plant Finder 2005–2006, Dorling Kindersley ISBN 1-4053-0736-6 The Royal Horticultural Society's website - Search facility for AGM plants RHS AGM Plant Awards RHS Plant Committees Search for AGM plants The Royal Horticultural Society Complete AGM lists
A perennial plant or perennial is a plant that lives more than two years. Some sources cite perennial plants being plants; the term is used to differentiate a plant from shorter-lived annuals and biennials. The term is widely used to distinguish plants with little or no woody growth from trees and shrubs, which are technically perennials. Perennials small flowering plants, that grow and bloom over the spring and summer, die back every autumn and winter, return in the spring from their rootstock, are known as herbaceous perennials. However, depending on the rigors of local climate, a plant, a perennial in its native habitat, or in a milder garden, may be treated by a gardener as an annual and planted out every year, from seed, from cuttings or from divisions. Tomato vines, for example, live several years in their natural tropical/subtropical habitat but are grown as annuals in temperate regions because they don't survive the winter. There is a class of evergreen, or non-herbaceous, including plants like Bergenia which retain a mantle of leaves throughout the year.
An intermediate class of plants is known as subshrubs, which retain a vestigial woody structure in winter, e.g. Penstemon; the local climate may dictate whether plants are treated as perennials. For instance, many varieties of Fuchsia are shrubs in warm regions, but in colder temperate climates may be cut to the ground every year as a result of winter frosts; the symbol for a perennial plant, based on Species Plantarum by Linnaeus, is, the astronomical symbol for the planet Jupiter. Perennial plants can be short-lived or they can be long-lived, as are some woody plants like trees, they include a wide assortment of plant groups from ferns and liverworts to the diverse flowering plants like orchids and grasses. Plants that flower and fruit only once and die are termed monocarpic or semelparous. However, most perennials are polycarpic. Perennials grow structures that allow them to adapt to living from one year to the next through a form of vegetative reproduction rather than seeding; these structures include bulbs, woody crowns, rhizomes plus others.
They might have specialized stems or crowns that allow them to survive periods of dormancy over cold or dry seasons during the year. Annuals produce seeds to continue the species as a new generation while the growing season is suitable, the seeds survive over the cold or dry period to begin growth when the conditions are again suitable. Many perennials have developed specialized features that allow them to survive extreme climatic and environmental conditions; some have adapted to survive cold temperatures. Those plants tend to invest a lot of resource into their adaptations and do not flower and set seed until after a few years of growth. Many perennials produce large seeds, which can have an advantage, with larger seedlings produced after germination that can better compete with other plants; some annuals produce many more seeds per plant in one season, while some perennials are not under the same pressure to produce large numbers of seeds but can produce seeds over many years. Dividing perennial plants is something that gardeners do around the months of October.
The point of doing the division at this time is to allow 6 weeks for adequate root growth prior to the ground reaching a freezing temperature. Due to the leaves falling from trees, as well as the excessive amount of rain received in most places during the fall weeks, the ground has adequate moisture for rapid growth; each type of plant must be separated differently. However, plants such as Irises have a root system known as a Rhizomes, these root systems should be planted with the bulb of the plant just above ground level, with leaves from the following year showing; the point of dividing perennials is to increase the amount of a single breed of plant in your garden. The more you divide your perennial plants every year, the more vast your garden will grow. In warmer and more favorable climates, perennials grow continuously. In seasonal climates, their growth is limited to the growing season. In some species, perennials retain their foliage all year round. Other plants are deciduous perennials, for example, in temperate regions a perennial plant may grow and bloom during the warm part of the year, with the foliage dying back in the winter.
In many parts of the world, seasonality is expressed as wet and dry periods rather than warm and cold periods, deciduous perennials lose their leaves in the dry season. With their roots protected below ground in the soil layer, perennial plants are notably tolerant of wildfire. Herbaceous perennials are able to tolerate the extremes of cold in temperate and Arctic winters, with less sensitivity than trees or shrubs. Perennial plants can be differentiated from annuals and biennials in that perennials have the ability to remain dormant over long periods of time and continue growth and reproduction; the meristem of perennial plants communicates with the hormones produced due to environmental situations and stage of development to begin and halt the ability to grow or flower. There is a distinction between the ability to grow and actual task of growth. For example, most trees regain the ability to grow in the midst of winter but do not initiate physical growth until the spring and summer months.
The start of dormancy can be seen in perennials pla
The flowering plants known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 64 orders, 416 families 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, the production of fruits that contain the seeds. Etymologically, angiosperm means a plant; the term comes from the Greek words sperma. The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago, the first flowering plants are known from 160 mya, they diversified extensively during the Early Cretaceous, became widespread by 120 mya, replaced conifers as the dominant trees from 100 to 60 mya. Angiosperms differ from other seed plants in several ways, described in the table below; these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.
Angiosperm stems are made up of seven layers. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms; the vascular bundles of the stem are arranged such that the phloem form concentric rings. In the dicotyledons, the bundles in the young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles, a complete ring is formed, a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside; the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.
Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They once formed the stem increases in diameter only in exceptional cases; the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, provide the most trustworthy external characteristics for establishing relationships among angiosperm species; the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally from the axil of a leaf; as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More the flower-bearing portion of the plant is distinguished from the foliage-bearing or vegetative portion, forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens.
The "female" cells called megaspores, which will divide to become the egg cell, are contained in the ovule and enclosed in the carpel. The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators; the individual members of these surrounding structures are known as petals. The outer series is green and leaf-like, functions to protect the rest of the flower the bud; the inner series is, in general, white or brightly colored, is more delicate in structure. It functions to attract bird pollinators. Attraction is effected by color and nectar, which may be secreted in some part of the flower; the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite, flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.
Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot transfer pollen to the pistil. Homomorphic flowers may employ a biochemical mechanism called self-incompatibility to discriminate between self and non-self pollen grains. In other species, the male and female parts are morphologically separated, developing on different flowers; the botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon and σπέρμα, was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked; the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any
Carl Linnaeus known after his ennoblement as Carl von Linné, was a Swedish botanist and zoologist who formalised binomial nomenclature, the modern system of naming organisms. He is known as the "father of modern taxonomy". Many of his writings were in Latin, his name is rendered in Latin as Carolus Linnæus. Linnaeus was born in the countryside of Småland in southern Sweden, he received most of his higher education at Uppsala University and began giving lectures in botany there in 1730. He lived abroad between 1735 and 1738, where he studied and published the first edition of his Systema Naturae in the Netherlands, he returned to Sweden where he became professor of medicine and botany at Uppsala. In the 1740s, he was sent on several journeys through Sweden to find and classify plants and animals. In the 1750s and 1760s, he continued to collect and classify animals and minerals, while publishing several volumes, he was one of the most acclaimed scientists in Europe at the time of his death. Philosopher Jean-Jacques Rousseau sent him the message: "Tell him I know no greater man on earth."
Johann Wolfgang von Goethe wrote: "With the exception of Shakespeare and Spinoza, I know no one among the no longer living who has influenced me more strongly." Swedish author August Strindberg wrote: "Linnaeus was in reality a poet who happened to become a naturalist." Linnaeus has been called Princeps botanicorum and "The Pliny of the North". He is considered as one of the founders of modern ecology. In botany and zoology, the abbreviation L. is used to indicate Linnaeus as the authority for a species' name. In older publications, the abbreviation "Linn." is found. Linnaeus's remains comprise the type specimen for the species Homo sapiens following the International Code of Zoological Nomenclature, since the sole specimen that he is known to have examined was himself. Linnaeus was born in the village of Råshult in Småland, Sweden, on 23 May 1707, he was the first child of Christina Brodersonia. His siblings were Anna Maria Linnæa, Sofia Juliana Linnæa, Samuel Linnæus, Emerentia Linnæa, his father taught him Latin as a small child.
One of a long line of peasants and priests, Nils was an amateur botanist, a Lutheran minister, the curate of the small village of Stenbrohult in Småland. Christina was the daughter of the rector of Samuel Brodersonius. A year after Linnaeus's birth, his grandfather Samuel Brodersonius died, his father Nils became the rector of Stenbrohult; the family moved into the rectory from the curate's house. In his early years, Linnaeus seemed to have a liking for plants, flowers in particular. Whenever he was upset, he was given a flower, which calmed him. Nils spent much time in his garden and showed flowers to Linnaeus and told him their names. Soon Linnaeus was given his own patch of earth. Carl's father was the first in his ancestry to adopt a permanent surname. Before that, ancestors had used the patronymic naming system of Scandinavian countries: his father was named Ingemarsson after his father Ingemar Bengtsson; when Nils was admitted to the University of Lund, he had to take on a family name. He adopted the Latinate name Linnæus after a giant linden tree, lind in Swedish, that grew on the family homestead.
This name was spelled with the æ ligature. When Carl was born, he was named Carl Linnæus, with his father's family name; the son always spelled it with the æ ligature, both in handwritten documents and in publications. Carl's patronymic would have been Nilsson, as in Carl Nilsson Linnæus. Linnaeus's father began teaching him basic Latin and geography at an early age; when Linnaeus was seven, Nils decided to hire a tutor for him. The parents picked a son of a local yeoman. Linnaeus did not like him, writing in his autobiography that Telander "was better calculated to extinguish a child's talents than develop them". Two years after his tutoring had begun, he was sent to the Lower Grammar School at Växjö in 1717. Linnaeus studied going to the countryside to look for plants, he reached the last year of the Lower School when he was fifteen, taught by the headmaster, Daniel Lannerus, interested in botany. Lannerus gave him the run of his garden, he introduced him to Johan Rothman, the state doctor of Småland and a teacher at Katedralskolan in Växjö.
A botanist, Rothman broadened Linnaeus's interest in botany and helped him develop an interest in medicine. By the age of 17, Linnaeus had become well acquainted with the existing botanical literature, he remarks in his journal that he "read day and night, knowing like the back of my hand, Arvidh Månsson's Rydaholm Book of Herbs, Tillandz's Flora Åboensis, Palmberg's Serta Florea Suecana, Bromelii Chloros Gothica and Rudbeckii Hortus Upsaliensis...."Linnaeus entered the Växjö Katedralskola in 1724, where he studied Greek, Hebrew and mathematics, a curriculum designed for boys preparing for the priesthood. In the last year at the gymnasium, Linnaeus's father visited to ask the professors how his son's studies were progressing. Rothman believed otherwise; the doctor offered to have Linnaeus live with his family in Växjö and to teach him physiology and botany. Nils accepted this offer. Rothman showed Linnaeus that botany was a serious sub