Petals are modified leaves that surround the reproductive parts of flowers. They are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are accompanied by another set of special leaves called sepals, that collectively form the calyx and lie just beneath the corolla; the calyx and the corolla together make up the perianth. When the petals and sepals of a flower are difficult to distinguish, they are collectively called tepals. Examples of plants in which the term tepal is appropriate include genera such as Tulipa. Conversely, genera such as Rosa and Phaseolus have well-distinguished petals; when the undifferentiated tepals resemble petals, they are referred to as "petaloid", as in petaloid monocots, orders of monocots with brightly coloured tepals. Since they include Liliales, an alternative name is lilioid monocots. Although petals are the most conspicuous parts of animal-pollinated flowers, wind-pollinated species, such as the grasses, either have small petals or lack them entirely.
The role of the corolla in plant evolution has been studied extensively since Charles Darwin postulated a theory of the origin of elongated corollae and corolla tubes. A corolla of separate tepals is apopetalous. If the petals are free from one another in the corolla, the plant is choripetalous. In the case of fused tepals, the term is syntepalous; the corolla in some plants forms a tube. Petals can differ in different species; the number of petals in a flower may hold clues to a plant's classification. For example, flowers on eudicots most have four or five petals while flowers on monocots have three or six petals, although there are many exceptions to this rule; the petal whorl or corolla may be bilaterally symmetrical. If all of the petals are identical in size and shape, the flower is said to be regular or actinomorphic. Many flowers are termed irregular or zygomorphic. In irregular flowers, other floral parts may be modified from the regular form, but the petals show the greatest deviation from radial symmetry.
Examples of zygomorphic flowers may be seen in members of the pea family. In many plants of the aster family such as the sunflower, Helianthus annuus, the circumference of the flower head is composed of ray florets; each ray floret is anatomically an individual flower with a single large petal. Florets in the centre of the disc have no or reduced petals. In some plants such as Narcissus the lower part of the petals or tepals are fused to form a floral cup above the ovary, from which the petals proper extend. Petal consists of two parts: the upper, broad part, similar to leaf blade called the blade and the lower part, similar to leaf petiole, called the claw, separated from each other at the limb. Claws are developed in petals of some flowers such as Erysimum cheiri; the inception and further development of petals shows a great variety of patterns. Petals of different species of plants vary in colour or colour pattern, both in visible light and in ultraviolet; such patterns function as guides to pollinators, are variously known as nectar guides, pollen guides, floral guides.
The genetics behind the formation of petals, in accordance with the ABC model of flower development, are that sepals, petals and carpels are modified versions of each other. It appears that the mechanisms to form petals evolved few times, rather than evolving from stamens. Pollination is an important step in the sexual reproduction of higher plants. Pollen is produced by the male organs of hermaphroditic flowers. Pollen does not move on its own and thus requires wind or animal pollinators to disperse the pollen to the stigma of the same or nearby flowers. However, pollinators are rather selective in determining the flowers; this develops competition between flowers and as a result flowers must provide incentives to appeal to pollinators. Petals play a major role in competing to attract pollinators. Henceforth pollination dispersal could occur and the survival of many species of flowers could prolong. Petals have various purposes depending on the type of plant. In general, petals operate to protect some parts of the flower and attract/repel specific pollinators.
This is where the positioning of the flower petals are located on the flower is the corolla e.g. the buttercup having shiny yellow flower petals which contain guidelines amongst the petals in aiding the pollinator towards the nectar. Pollinators have the ability to determine specific flowers. Using incentives flowers draw pollinators and set up a mutual relation between each other in which case the pollinators will remember to always guard and pollinate these flowers; the petals could produce different scents to allure desirable pollinators or repel undesirable pollinators. Some flowers will mimic the scents produced by materials such as decaying meat, to attract pollinators to them. Various colour traits are used by different petals that could attract pollinators that have poor smelling abilities, or that only come out at certain parts of the day; some flowers are able to change the colour
In the APG IV system for the classification of flowering plants, the name asterids denotes a clade. Common examples include the forget-me-nots, the common sunflower, morning glory and sweet potato, lavender, olive, honeysuckle, ash tree, snapdragon, psyllium, garden sage, table herbs such as mint and rosemary, rainforest trees such as Brazil nut. Most of the taxa belonging to this clade had been referred to the Asteridae in the Cronquist system and to the Sympetalae in earlier systems; the name asterids resembles the earlier botanical name but is intended to be the name of a clade rather than a formal ranked name, in the sense of the ICBN. The phylogenetic tree presented hereafter has been proposed by the APG IV project. Genetic analysis carried out after APG II maintains that the sister to all other asterids are the Cornales. A second order that split from the base of the asterids are the Ericales; the remaining orders cluster into two clades, the lamiids and the campanulids. The structure of both of these clades has changed in APG III.
In APG III system, the following clades were renamed: euasterids I → lamiids euasterids II → campanulids Asterids in Stevens, P. F.. Angiosperm Phylogeny Website. Version 7, May 2006
Rauvolfioideae is a subfamily of the flowering plant family Apocynaceae. Many species are woody lianas, others are perennial herbs. Media related to Rauvolfioideae at Wikimedia Commons
In scientific nomenclature, a synonym is a scientific name that applies to a taxon that goes by a different scientific name, although the term is used somewhat differently in the zoological code of nomenclature. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies; this name is no longer in use: it is now a synonym of the current scientific name, Picea abies. Unlike synonyms in other contexts, in taxonomy a synonym is not interchangeable with the name of which it is a synonym. In taxonomy, synonyms have a different status. For any taxon with a particular circumscription and rank, only one scientific name is considered to be the correct one at any given time. A synonym cannot exist in isolation: it is always an alternative to a different scientific name. Given that the correct name of a taxon depends on the taxonomic viewpoint used a name, one taxonomist's synonym may be another taxonomist's correct name. Synonyms may arise whenever the same taxon is named more than once, independently.
They may arise when existing taxa are changed, as when two taxa are joined to become one, a species is moved to a different genus, a variety is moved to a different species, etc. Synonyms come about when the codes of nomenclature change, so that older names are no longer acceptable. To the general user of scientific names, in fields such as agriculture, ecology, general science, etc. A synonym is a name, used as the correct scientific name but, displaced by another scientific name, now regarded as correct, thus Oxford Dictionaries Online defines the term as "a taxonomic name which has the same application as another one, superseded and is no longer valid." In handbooks and general texts, it is useful to have synonyms mentioned as such after the current scientific name, so as to avoid confusion. For example, if the much advertised name change should go through and the scientific name of the fruit fly were changed to Sophophora melanogaster, it would be helpful if any mention of this name was accompanied by "".
Synonyms used in this way may not always meet the strict definitions of the term "synonym" in the formal rules of nomenclature which govern scientific names. Changes of scientific name have two causes: they may be taxonomic or nomenclatural. A name change may be caused by changes in the circumscription, position or rank of a taxon, representing a change in taxonomic, scientific insight. A name change may be due to purely nomenclatural reasons, that is, based on the rules of nomenclature. Speaking in general, name changes for nomenclatural reasons have become less frequent over time as the rules of nomenclature allow for names to be conserved, so as to promote stability of scientific names. In zoological nomenclature, codified in the International Code of Zoological Nomenclature, synonyms are different scientific names of the same taxonomic rank that pertain to that same taxon. For example, a particular species could, over time, have had two or more species-rank names published for it, while the same is applicable at higher ranks such as genera, orders, etc.
In each case, the earliest published name is called the senior synonym, while the name is the junior synonym. In the case where two names for the same taxon have been published the valid name is selected accorded to the principle of the first reviser such that, for example, of the names Strix scandiaca and Strix noctua, both published by Linnaeus in the same work at the same date for the taxon now determined to be the snowy owl, the epithet scandiaca has been selected as the valid name, with noctua becoming the junior synonym. One basic principle of zoological nomenclature is that the earliest published name, the senior synonym, by default takes precedence in naming rights and therefore, unless other restrictions interfere, must be used for the taxon. However, junior synonyms are still important to document, because if the earliest name cannot be used the next available junior synonym must be used for the taxon. For other purposes, if a researcher is interested in consulting or compiling all known information regarding a taxon, some of this may well have been published under names now regarded as outdated and so it is again useful to know a list of historic synonyms which may have been used for a given current taxon name.
Objective synonyms refer to taxa with same rank. This may be species-group taxa of the same rank with the same type specimen, genus-group taxa of the same rank with the same type species or if their type species are themselves objective synonyms, of family-group taxa with the same type genus, etc. In the case of subjective synonyms, there is no such shared type, so the synonymy is open to taxonomic judgement, meaning that th
In biology, poisons are substances that cause disturbances in organisms by chemical reaction or other activity on the molecular scale, when an organism absorbs a sufficient quantity. The fields of medicine and zoology distinguish a poison from a toxin, from a venom. Toxins are poisons produced by organisms in nature, venoms are toxins injected by a bite or sting; the difference between venom and other poisons is the delivery method. Industry and other sectors employ poisonous substances for reasons other than their toxicity. Most poisonous industrial compounds have associated material safety data sheets and are classed as hazardous substances. Hazardous substances are subject to extensive regulation on production and use in overlapping domains of occupational safety and health, public health, drinking water quality standards, air pollution and environmental protection. Due to the mechanics of molecular diffusion, many poisonous compounds diffuse into biological tissues, water, or soil on a molecular scale.
By the principle of entropy, chemical contamination is costly or infeasible to reverse, unless specific chelating agents or micro-filtration processes are available. Chelating agents are broader in scope than the acute target, therefore their ingestion necessitates careful medical or veterinarian supervision. Pesticides are one group of substances whose toxicity to various insects and other animals deemed to be pests is their prime purpose. Natural pesticides have been used for this purpose for thousands of years. Bioaccumulation of chemically-prepared agricultural insecticides is a matter of concern for the many species birds, which consume insects as a primary food source. Selective toxicity, controlled application, controlled biodegradation are major challenges in herbicide and pesticide development and in chemical engineering as all lifeforms on earth share an underlying biochemistry. A poison which enters the food chain—whether of industrial, agricultural, or natural origin—might not be toxic to the first organism that ingests the toxin, but can become further concentrated in predatory organisms further up the food chain carnivores and omnivores concerning fat soluble poisons which tend to become stored in biological tissue rather than excreted in urine or other water-based effluents.
Two common cases of acute natural poisoning are theobromine poisoning of dogs and cats, mushroom poisoning in humans. Dogs and cats are not natural herbivores, but a chemical defense developed by Theobroma cacao can be incidentally fatal nevertheless. Many omnivores, including humans consume edible fungi, thus many fungi have evolved to become decisively inedible, in this case as a direct defense. Apart from food, many poisons enter the body through the skin and lungs. Hydrofluoric acid is a notorious contact poison, in addition to its corrosive damage. Occurring sour gas is a notorious, fast-acting atmospheric poison. Plant-based contact irritants, such as that possessed by poison ivy or poison oak, are classed as allergens rather than poisons. Poison can enter the body through the teeth, faulty medical implants, or by injection. In 2013, 3.3 million cases of unintentional human poisonings occurred. This resulted in 98,000 deaths worldwide, down from 120,000 deaths in 1990. In modern society, cases of suspicious death elicit the attention of the Coroner's office and forensic investigators.
While arsenic is a occurring environmental poison, its artificial concentrate was once nicknamed inheritance powder. In Medieval Europe, it was common for monarchs to employ personal food tasters to thwart royal assassination, in the dawning age of the Apothecary. Of increasing concern since the isolation of natural radium by Marie and Pierre Curie in 1898—and the subsequent advent of nuclear physics and nuclear technologies—are radiological poisons; these are associated with ionizing radiation, a mode of toxicity quite distinct from chemically active poisons. In mammals, chemical poisons are passed from mother to offspring through the placenta during gestation, or through breast milk during nursing. In contrast, radiological damage can be passed from mother or father to offspring through genetic mutation, which—if not fatal in miscarriage or childhood, or a direct cause of infertility—can be passed along again to a subsequent generation. Atmospheric radon is a natural radiological poison of increasing impact since humans moved from hunter-gatherer lifestyles though cave dwelling to enclosed structures able to contain radon in dangerous concentrations.
The 2006 poisoning of Alexander Litvinenko was a novel use of radiological assassination meant to evade the normal investigation of chemical poisons. Poisons dispersed into the environment are known as pollution; these are of human origin, but pollution can include unwanted biological processes such as toxic red tide, or acute changes to the natural chemical environment attributed to invasive species, which are toxic or detrimental to the prior ecology (especially if the prior ecology was associated with human economic valu
A shrub or bush is a small- to medium-sized woody plant. Unlike herbaceous plants, shrubs have persistent woody, they are distinguished from trees by their multiple stems and shorter height, are under 6 m tall. Plants of many species may grow either depending on their growing conditions. Small, low shrubs less than 2 m tall, such as lavender and most small garden varieties of rose, are termed "subshrubs". An area of cultivated shrubs in a park or a garden is known as a shrubbery; when clipped as topiary, suitable species or varieties of shrubs develop dense foliage and many small leafy branches growing close together. Many shrubs respond well to renewal pruning, in which hard cutting back to a "stool" results in long new stems known as "canes". Other shrubs respond better to selective pruning to reveal their character. Shrubs in common garden practice are considered broad-leaved plants, though some smaller conifers such as mountain pine and common juniper are shrubby in structure. Species that grow into a shrubby habit may be either evergreen.
In botany and ecology, a shrub is more used to describe the particular physical structural or plant life-form of woody plants which are less than 8 metres high and have many stems arising at or near the base. For example, a descriptive system adopted in Australia is based on structural characteristics based on life-form, plus the height and amount of foliage cover of the tallest layer or dominant species. For shrubs 2–8 metres high the following structural forms are categorized: dense foliage cover — closed-shrub mid-dense foliage cover — open-shrub sparse foliage cover — tall shrubland sparse foliage cover — tall open shrublandFor shrubs less than 2 metres high the following structural forms are categorized: dense foliage cover — closed-heath or closed low shrubland— mid-dense foliage cover — open-heath or mid-dense low shrubland— sparse foliage cover — low shrubland sparse foliage cover — low open shrubland Those marked with * can develop into tree form
Plants are multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. Plants were treated as one of two kingdoms including all living things that were not animals, all algae and fungi were treated as plants. However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes. By one definition, plants form the clade Viridiplantae, a group that includes the flowering plants and other gymnosperms and their allies, liverworts and the green algae, but excludes the red and brown algae. Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria, their chloroplasts contain b, which gives them their green color. Some plants are parasitic or mycotrophic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is common.
There are about 320 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants. Green plants provide a substantial proportion of the world's molecular oxygen and are the basis of most of Earth's ecosystems on land. Plants that produce grain and vegetables form humankind's basic foods, have been domesticated for millennia. Plants have many cultural and other uses, as ornaments, building materials, writing material and, in great variety, they have been the source of medicines and psychoactive drugs; the scientific study of plants is known as a branch of biology. All living things were traditionally placed into one of two groups and animals; this classification may date from Aristotle, who made the distincton between plants, which do not move, animals, which are mobile to catch their food. Much when Linnaeus created the basis of the modern system of scientific classification, these two groups became the kingdoms Vegetabilia and Animalia. Since it has become clear that the plant kingdom as defined included several unrelated groups, the fungi and several groups of algae were removed to new kingdoms.
However, these organisms are still considered plants in popular contexts. The term "plant" implies the possession of the following traits multicellularity, possession of cell walls containing cellulose and the ability to carry out photosynthesis with primary chloroplasts; when the name Plantae or plant is applied to a specific group of organisms or taxon, it refers to one of four concepts. From least to most inclusive, these four groupings are: Another way of looking at the relationships between the different groups that have been called "plants" is through a cladogram, which shows their evolutionary relationships; these are not yet settled, but one accepted relationship between the three groups described above is shown below. Those which have been called "plants" are in bold; the way in which the groups of green algae are combined and named varies between authors. Algae comprise several different groups of organisms which produce food by photosynthesis and thus have traditionally been included in the plant kingdom.
The seaweeds range from large multicellular algae to single-celled organisms and are classified into three groups, the green algae, red algae and brown algae. There is good evidence that the brown algae evolved independently from the others, from non-photosynthetic ancestors that formed endosymbiotic relationships with red algae rather than from cyanobacteria, they are no longer classified as plants as defined here; the Viridiplantae, the green plants – green algae and land plants – form a clade, a group consisting of all the descendants of a common ancestor. With a few exceptions, the green plants have the following features in common, they undergo closed mitosis without centrioles, have mitochondria with flat cristae. The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. Two additional groups, the Rhodophyta and Glaucophyta have primary chloroplasts that appear to be derived directly from endosymbiotic cyanobacteria, although they differ from Viridiplantae in the pigments which are used in photosynthesis and so are different in colour.
These groups differ from green plants in that the storage polysaccharide is floridean starch and is stored in the cytoplasm rather than in the plastids. They appear to have had a common origin with Viridiplantae and the three groups form the clade Archaeplastida, whose name implies that their chloroplasts were derived from a single ancient endosymbiotic event; this is the broadest modern definition of the term'plant'. In contrast, most other algae not only have different pigments but have chloroplasts with three or four surrounding membranes, they are not close relatives of the Archaeplastida having acquired chloroplasts separately from ingested or symbiotic green and red algae. They are thus not included in the broadest modern definition of the plant kingdom, although they were in the past; the green plants or Viridiplantae were traditionally divided into the green algae (including