Dormancy is a period in an organism's life cycle when growth and physical activity are temporarily stopped. This therefore helps an organism to conserve energy. Dormancy tends to be associated with environmental conditions. Organisms can synchronize entry to a dormant phase with their environment through predictive or consequential means. Predictive dormancy occurs when an organism enters a dormant phase before the onset of adverse conditions. For example and decreasing temperature are used by many plants to predict the onset of winter. Consequential dormancy occurs when organisms enter a dormant phase after adverse conditions have arisen; this is found in areas with an unpredictable climate. While sudden changes in conditions may lead to a high mortality rate among animals relying on consequential dormancy, its use can be advantageous, as organisms remain active longer and are therefore able to make greater use of available resources. Hibernation is a mechanism used by many mammals to reduce energy expenditure and survive food shortage over the winter.
Hibernation may be consequential. An animal prepares for hibernation by building up a thick layer of body fat during late summer and autumn that will provide it with energy during the dormant period. During hibernation, the animal undergoes many physiological changes, including decreased heart rate and decreased body temperature. In addition to shivering, some hibernating animals produce body heat by non-shivering thermogenesis to avoid freezing. Non-shivering thermogenesis is a regulated process in which the proton gradient generated by electron transport in mitochondria is used to produce heat instead of ATP in brown adipose tissue. Animals that hibernate include bats, ground squirrels and other rodents, mouse lemurs, the European hedgehog and other insectivores and marsupials. Although hibernation is exclusively seen in mammals, some birds, such as the common poorwill, may hibernate. Diapause is a predictive strategy, predetermined by an animal's genotype. Diapause is common in insects, allowing them to suspend development between autumn and spring, in mammals such as the roe deer, in which a delay in attachment of the embryo to the uterine lining ensures that offspring are born in spring, when conditions are most favorable.
Aestivation spelled estivation, is an example of consequential dormancy in response to hot or dry conditions. It is common in invertebrates such as the garden snail and worm but occurs in other animals such as lungfish, desert tortoises, crocodiles. Brumation is an example of dormancy in reptiles, similar to hibernation, it differs from hibernation in the metabolic processes involved. Reptiles begin brumation in late autumn, they wake up to drink water and return to "sleep". They can go for months without food. Reptiles may eat more than usual before the brumation time but eat less or refuse food as the temperature drops. However, they do; the brumation period is anywhere from one to eight months depending on the air temperature and the size and health of the reptile. During the first year of life, many small reptiles do not brumate, but rather slow down and eat less often. Brumation is triggered by lack of heat and the decrease in the hours of daylight in winter, similar to hibernation. In plant physiology, dormancy is a period of arrested plant growth.
It is a survival strategy exhibited by many plant species, which enables them to survive in climates where part of the year is unsuitable for growth, such as winter or dry seasons. Many plant species that exhibit dormancy have a biological clock that tells them when to slow activity and to prepare soft tissues for a period of freezing temperatures or water shortage. On the other hand, dormancy can be triggered after a normal growing season by decreasing temperatures, shortened day length, and/or a reduction in rainfall. Chemical treatment on dormant plants has been proven to be an effective method to break dormancy in woody plants such as grapes, apples and kiwis. Hydrogen cyanamide stimulates cell division and growth in dormant plants, causing budbreak when the plant is on the edge of breaking dormancy. Slight injury of cells may play a role in the mechanism of action; the injury is thought to result in increased permeability of cellular membranes. The injury is associated with the inhibition of catalase, which in turn stimulates the pentose phosphate cycle.
Hydrogen cyanamide interacts with the cytokinin metabolic cycle, which results in triggering a new growth cycle. The images below show two widespread dormancy patterns amongst sympodially growing orchids: When a mature and viable seed under a favorable condition fails to germinate, it is said to be dormant. Seed dormancy is referred to as embryo dormancy or internal dormancy and is caused by endogenous characteristics of the embryo that prevent germination. Dormancy should not be confused with seed coat dormancy, external dormancy, or hardseededness, caused by the presence of a hard seed covering or seed coat that prevents water and oxygen from reaching and activating the embryo, it is a physical barrier to germination, not a true form of dormancy. Temperate woody perennial plants require chilling temperatures to overcome winter dormancy; the effect of chilling temperatures depends on species and growth stage. In some species, rest can be broken within hours at
Australia the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the world's sixth-largest country by total area; the neighbouring countries are Papua New Guinea and East Timor to the north. The population of 25 million is urbanised and concentrated on the eastern seaboard. Australia's capital is Canberra, its largest city is Sydney; the country's other major metropolitan areas are Melbourne, Brisbane and Adelaide. Australia was inhabited by indigenous Australians for about 60,000 years before the first British settlement in the late 18th century, it is documented. After the European exploration of the continent by Dutch explorers in 1606, who named it New Holland, Australia's eastern half was claimed by Great Britain in 1770 and settled through penal transportation to the colony of New South Wales from 26 January 1788, a date which became Australia's national day; the population grew in subsequent decades, by the 1850s most of the continent had been explored and an additional five self-governing crown colonies established.
On 1 January 1901, the six colonies federated. Australia has since maintained a stable liberal democratic political system that functions as a federal parliamentary constitutional monarchy, comprising six states and ten territories. Being the oldest and driest inhabited continent, with the least fertile soils, Australia has a landmass of 7,617,930 square kilometres. A megadiverse country, its size gives it a wide variety of landscapes, with deserts in the centre, tropical rainforests in the north-east and mountain ranges in the south-east. A gold rush began in Australia in the early 1850s, its population density, 2.8 inhabitants per square kilometre, remains among the lowest in the world. Australia generates its income from various sources including mining-related exports, telecommunications and manufacturing. Indigenous Australian rock art is the oldest and richest in the world, dating as far back as 60,000 years and spread across hundreds of thousands of sites. Australia is a developed country, with the world's 14th-largest economy.
It has a high-income economy, with the world's tenth-highest per capita income. It is a regional power, has the world's 13th-highest military expenditure. Australia has the world's ninth-largest immigrant population, with immigrants accounting for 26% of the population. Having the third-highest human development index and the eighth-highest ranked democracy globally, the country ranks in quality of life, education, economic freedom, civil liberties and political rights, with all its major cities faring well in global comparative livability surveys. Australia is a member of the United Nations, G20, Commonwealth of Nations, ANZUS, Organisation for Economic Co-operation and Development, World Trade Organization, Asia-Pacific Economic Cooperation, Pacific Islands Forum and the ASEAN Plus Six mechanism; the name Australia is derived from the Latin Terra Australis, a name used for a hypothetical continent in the Southern Hemisphere since ancient times. When Europeans first began visiting and mapping Australia in the 17th century, the name Terra Australis was applied to the new territories.
Until the early 19th century, Australia was best known as "New Holland", a name first applied by the Dutch explorer Abel Tasman in 1644 and subsequently anglicised. Terra Australis still saw occasional usage, such as in scientific texts; the name Australia was popularised by the explorer Matthew Flinders, who said it was "more agreeable to the ear, an assimilation to the names of the other great portions of the earth". The first time that Australia appears to have been used was in April 1817, when Governor Lachlan Macquarie acknowledged the receipt of Flinders' charts of Australia from Lord Bathurst. In December 1817, Macquarie recommended to the Colonial Office. In 1824, the Admiralty agreed that the continent should be known by that name; the first official published use of the new name came with the publication in 1830 of The Australia Directory by the Hydrographic Office. Colloquial names for Australia include "Oz" and "the Land Down Under". Other epithets include "the Great Southern Land", "the Lucky Country", "the Sunburnt Country", "the Wide Brown Land".
The latter two both derive from Dorothea Mackellar's 1908 poem "My Country". Human habitation of the Australian continent is estimated to have begun around 65,000 to 70,000 years ago, with the migration of people by land bridges and short sea-crossings from what is now Southeast Asia; these first inhabitants were the ancestors of modern Indigenous Australians. Aboriginal Australian culture is one of the oldest continual civilisations on earth. At the time of first European contact, most Indigenous Australians were hunter-gatherers with complex economies and societies. Recent archaeological finds suggest. Indigenous Australians have an oral culture with spiritual values based on reverence for the land and a belief in the Dreamtime; the Torres Strait Islanders, ethnically Melanesian, obtained their livelihood from seasonal horticulture and the resources of their reefs and seas. The northern coasts and waters of Australia were visited s
Haworthia is a large genus of small succulent plants endemic to Southern Africa. Like the aloes, they are members of the subfamily Asphodeloideae and they resemble miniature aloes, except in their flowers, which are distinctive in appearance, they are popular container plants. Haworthias are small succulent plants, forming rosettes of leaves from 3 cm to exceptionally 30 cm in diameter, depending on the species; these rosettes are stemless but in some species stems reach up to 50 cm. The inflorescences of some species may exceed 40 cm in height; the plants can be clump-forming. Many species have firm, fleshy leaves dark green in colour, whereas others are softer and contain leaf windows with translucent panels through which sunlight can reach internal photosynthetic tissues, their flowers are small, white. Though they are similar between species, flowers from the species in hexangulares have green striations and those from other species have brown lines in the flowers. However, their leaves show wide variations within one species.
Additionally, when the plants are stressed, their colours can change to purples. Depriving them of nitrogen results in paler leaves. Most species are endemic to South Africa, with the greatest species diversity occurring in the south-western Cape; some species do however extend into neighbouring territories, in Swaziland, southern Namibia and southern Mozambique. Haworthia is a genus within the family Asphodelaceae, subfamily Asphodeloideae; the genus is named after the botanist Adrian Hardy Haworth. B. Bayer recognised 60 species in a review of the genus in 2012, whereas other taxonomists are much less conservative. Related genera are Aloe and Astroloba and intergeneric hybrids are known; the classification of the flowering plant subfamily Asphodeloideae is weak, concepts of the genera are not well substantiated. Haworthia has been a a weakly contrived genus; because of their horticultural interest, its taxonomy has been dominated by amateur collectors, the literature is rife with misunderstanding of what the taxa are or should be.
Recent phylogenetic studies have demonstrated that the traditional divisions of the genus are relatively unrelated. In recognition of the polyphyletic nature of the genus and Tulista have been split off. Botanists had long noticed differences in the flowers the three subgenera, but had considered those differences to be inconsequential, although the differences between species in the same subgenus are; the roots and rosettes do demonstrate some generic differences while wide variations occur within one species. Many species of Haworthia have been moved to Haworthiopsis and Tulista, in particular since the last update of The Plant List, which contains about 150 accepted species of Haworthia; the actual number and identification of the species is not well established. The World Checklist of Selected Plant Families has been updated to exclude the species now in Haworthiopsis and Tulista; the species it accepts as of February 2018 are listed below, excluding Haworthia kingiana and Haworthia minor, placed in Tulista by other sources.
There is widespread special collector interest, some species such as Haworthia cymbiformis are common house and garden plants. All Haworthia species are adapted for semi-shade conditions and they are therefore healthiest in shade or semi-shade; some species like Haworthia pumila and Haworthia truncata can be adapted to tolerate full-sun however. All Haworthia species favour well-drained soil. Watering depends on the species but most of the common species are tolerant of a variety of watering routines. Rarer species may have more specific requirements. Haworthia species reproduce both through budding, or offsets. Certain species or clones may be more successful or rapid in offset production, these pups are removed to yield new plants once a substantial root system has developed on the offshoot. Less reliably, the plants may be propagated through leaf cuttings, in some instances, through tissue culture. Haworthia Haworthia Asphodelaceae Anonymous Haworthia Society Haworthia Updates
In botany, succulent plants known as succulents, are plants that have some parts that are more than thickened and fleshy to retain water in arid climates or soil conditions. The word "succulent" comes from meaning juice, or sap. Succulent plants stems; some definitions include roots, thus geophytes that survive unfavorable periods by dying back to underground storage organs may be regarded as succulents. In horticultural use, the term "succulent" is sometimes used in a way which excludes plants that botanists would regard as succulents, such as cacti. Succulents are grown as ornamental plants because of their striking and unusual appearance. Many plant families have multiple succulents found within them. In some families, such as Aizoaceae and Crassulaceae, most species are succulents; the habitats of these water preserving plants are in areas with high temperatures and low rainfall. Succulents have the ability to thrive on limited water sources, such as mist and dew, which makes them equipped to survive in an ecosystem which contains scarce water sources.
A general definition of succulents is that they are drought resistant plants in which the leaves, stem or roots have become more than fleshy by the development of water-storing tissue. Other sources exclude roots as in the definition "a plant with thick and swollen stems and/or leaves, adapted to dry environments." This difference affects the relationship between succulents and "geophytes" – plants that survive unfavorable seasons as a resting bud on an underground organ. These underground organs, such as bulbs and tubers, are fleshy with water-storing tissues, thus if roots are included in the definition, many geophytes would be classed as succulents. Plants adapted to living in dry environments such as succulents are termed xerophytes. However, not all xerophytes are succulents, since there are other ways of adapting to a shortage of water, e.g. by developing small leaves which may roll up or having leathery rather than succulent leaves. Nor are all succulents xerophytes, since plants like Crassula helmsii are both succulent and aquatic.
Those who grow succulents. In horticultural use, the term succulent excludes cacti. For example, Jacobsen's three volume Handbook of Succulent Plants does not cover cacti, "cacti and succulents" is the title or part of the title of many books covering the cultivation of these plants. However, in botanical terminology, cacti are succulents. Horticulturists may exclude other groups of plants, e.g. bromeliads. A practical, but unscientific, horticultural definition is "a succulent plant is any desert plant that a succulent plant collector wishes to grow." Such plants less include geophytes but do include plants with a caudex, a swollen above-ground organ at soil level, formed from a stem, a root or both. A further difficulty is that plants are not either non-succulent. In many genera and families there is a continuous gradation from plants with thin leaves and normal stems to those with clearly thickened and fleshy leaves or stems, so that deciding what is a succulent is arbitrary. Different sources may classify the same species differently.
The storage of water gives succulent plants a more swollen or fleshy appearance than other plants, a characteristic known as succulence. In addition to succulence, succulent plants variously have other water-saving features; these may include: Crassulacean acid metabolism to minimize water loss absent, reduced, or cylindrical-to-spherical leaves reduction in the number of stomata stems as the main site of photosynthesis, rather than leaves compact, cushion-like, columnar, or spherical growth form ribs enabling rapid increases in plant volume and decreasing surface area exposed to the sun waxy, hairy, or spiny outer surface to create a humid micro-habitat around the plant, which reduces air movement near the surface of the plant, thereby reduces water loss and creates shade roots near the surface of the soil, so they are able to take up moisture from small showers or from heavy dew ability to remain plump and full of water with high internal temperatures impervious outer cuticle mucilaginous substances, which retain water abundantly Other than Antarctica, succulents can be found within each continent.
While it is thought that most succulents come from dry areas such as steppes, semi-desert, desert, the world's driest areas do not make for proper succulent habitats. Australia, the world's driest continent, host few native succulents due to the frequent and prolonged droughts. In Africa, the continent with the most native succulents, does not host many of the plants in its most dry regions. However, while succulents are unable to grow in these harshest of conditions, they are able to grow in conditions that are uninhabitable by other plants. In fact, many succulents are able to thrive in dry conditions, some are able to last up to two years without water depending on their surroundings and adaptations. Succulents may occasionally occur as epiphytes, growing on other plants with limited or no contact with the ground, are dependent on their ability to store water and gain nutrients by other means. Succulents occur as inhabitants of sea coasts and dry lakes, which are exposed to high levels of dissolved minerals that are deadly to many other plant species.
Potted succulents are able to grow in most indoor environments with minimal care. There are sixty di
Tubers are enlarged structures in some plant species used as storage organs for nutrients. They are used for the plant's perennation, to provide energy and nutrients for regrowth during the next growing season, as a means of asexual reproduction. Stem tubers form thickened stolons. Common plant species with stem tubers include yam; some sources treat modified lateral roots under the definition. The term originates from Latin tuber, meaning "lump, swelling"; some sources define the term "tuber" to mean only structures derived from stems. A stem tuber forms from thickened stolons; the top sides of the tuber produce shoots that grow into typical stems and leaves and the under sides produce roots. They tend to form at the sides of the parent plant and are most located near the soil surface; the underground stem tuber is a short-lived storage and regenerative organ developing from a shoot that branches off a mature plant. The offsprings or new tubers are attached to a parent tuber or form at the end of a hypogeogenous rhizome.
In the autumn the plant dies, except for the new offspring stem tubers which have one dominant bud, which in spring regrows a new shoot producing stems and leaves, in summer the tubers decay and new tubers begin to grow. Some plants form smaller tubers and/or tubercules which act like seeds, producing small plants that resemble seedlings; some stem tubers are long-lived, such as those of tuberous begonia, but many plants have tubers that survive only until the plants have leafed out, at which point the tuber is reduced to a shriveled-up husk. Stem tubers start off as enlargements of the hypocotyl section of a seedling but sometimes include the first node or two of the epicotyl and the upper section of the root; the stem tuber has a vertical orientation with one or a few vegetative buds on the top and fibrous roots produced on the bottom from a basal section the stem tuber has an oblong rounded shape. Tuberous begonia and Cyclamen are grown stem tubers. Mignonette vine produces aerial stem tubers on 12-to-25-foot-tall vines, the tubers fall to the ground and grow.
Plectranthus esculentus of the mint family Lamiaceae, produces tuberous under ground organs from the base of the stem, weighing up to 1.8 kg per tuber, forming from axillary buds producing short stolons that grow into tubers. Potatoes are stem tubers. Enlarged stolons thicken to develop into storage organs; the tuber has all the parts including nodes and internodes. The nodes are the eyes and each has a leaf scar; the nodes or eyes are arranged around the tuber in a spiral fashion beginning on the end opposite the attachment point to the stolon. The terminal bud is produced at the farthest point away from the stolon attachment and tubers thus show the same apical dominance as a normal stem. Internally, a tuber is filled with starch stored in enlarged parenchyma like cells; the inside of a tuber has the typical cell structures of any stem, including a pith, vascular zones, a cortex. The tuber is produced in one growing season and used to perennate the plant and as a means of propagation; when fall comes, the above-ground structure of the plant dies, but the tubers survive over winter underground until spring, when they regenerate new shoots that use the stored food in the tuber to grow.
As the main shoot develops from the tuber, the base of the shoot close to the tuber produces adventitious roots and lateral buds on the shoot. The shoot produces stolons that are long etiolated stems; the stolon elongates during long days with the presence of high auxins levels that prevent root growth off of the stolon. Before new tuber formation begins, the stolon must be a certain age; the enzyme lipoxygenase makes a hormone, jasmonic acid, involved in the control of potato tuber development. The stolons are recognized when potato plants are grown from seeds; as the plants grow, stolons are produced around the soil surface from the nodes. The tubers form close to the soil surface and sometimes on top of the ground; when potatoes are cultivated, the tubers are planted much deeper into the soil. Planting the pieces deeper creates more area for the plants to generate the tubers and their size increases; the pieces sprout shoots. These shoots generate short stolons from the nodes while in the ground.
When the shoots reach the soil surface, they produce roots and shoots that grow into the green plant. A tuberous root or storage root, is a modified lateral root, enlarged to function as a storage organ; the enlarged area of the root-tuber, or storage root, can be produced at the end or middle of a root or involve the entire root. It is thus similar in function and appearance to a stem tuber. Examples of plants with notable tuberous roots include the sweet potato and dahlia. Root tubers are perennating organs, thickened roots that store nutrients over periods when the plant cannot grow, thus permitting survival from one year to the next; the massive enlargement of secondary roots represented by sweet potato, have the internal and external cell and tissue structures of a normal root, they produce adventitious roots and stems which again produce adventitious roots. In root-tubers, there are reduced leaves. Root tubers have one end called the proximal end, the end
A caudex of a plant is a stem, but the term is used to mean a rootstock and a basal stem structure from which new growth arises. In the strict sense of the term, meaning a stem, "caudex" is most used with plants that have a different stem morphology from the typical angiosperm dicotyledon stem: examples of this include palms and cycads; the related term caudiciform meaning stem-like, is sometimes used to mean pachycaul, thick-stemmed. The term is from the Latin caudex, a noun meaning "tree trunk". Stipe Bihrmann's Caudiciforms Extensive listing of caudiciforms, images for most species Wayne's Word Caudiciform Plants With An Enlarged Caudex
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