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48-553: A machair ( Scottish Gaelic pronunciation: [ˈmaxɪɾʲ] ; sometimes machar in English) is a fertile low-lying grassy plain found on part of the northwest coastlines of Ireland and Scotland , in particular the Outer Hebrides . The best examples are found on North and South Uist , Harris and Lewis . Machair is a Gaelic word meaning "fertile plain", but the word is now also used in scientific literature to describe

96-464: A carbohydrate energy source. The carbohydrate source can be combinations of discrete sugars or can be derived from other sources such as banana , pineapple , peach , or even tomato puree or coconut water . After the preparation of the agar medium, it is poured into test tubes or jars which are then autoclaved (or cooked in a pressure cooker) to sterilize the medium. After cooking, the medium begins to gel as it cools. The taxonomy of this family

144-428: A gap ). Coastal plains mostly rise from sea level until they run into elevated features such as mountains or plateaus. Plains can be formed from flowing lava ; from deposition of sediment by water, ice, or wind; or formed by erosion by the agents from hills or mountains. Biomes on plains include grassland ( temperate or subtropical ), steppe ( semi-arid ), savannah ( tropical ) or tundra ( polar ). In

192-401: A seta , knocking the pollinator off the flower. After pollination, the sepals and petals fade and wilt, but they usually remain attached to the ovary. In 2011, Bulbophyllum nocturnum was discovered to flower nocturnally. Some species, such as in the genera Phalaenopsis , Dendrobium , and Vanda , produce offshoots or plantlets formed from one of the nodes along the stem , through

240-474: A spur of the labellum ( 8 in the illustration above), or on the point of the sepals, or in the septa of the ovary, the most typical position amongst the Asparagales . In orchids that produce pollinia, pollination happens as some variant of the following sequence: when the pollinator enters into the flower, it touches a viscidium, which promptly sticks to its body, generally on the head or abdomen. While leaving

288-551: A velamen , has the function of absorbing humidity. It is made of dead cells and can have a silvery-grey, white or brown appearance. In some orchids, the velamen includes spongy and fibrous bodies near the passage cells, called tilosomes. The cells of the root epidermis grow at a right angle to the axis of the root to allow them to get a firm grasp on their support. Nutrients for epiphytic orchids mainly come from mineral dust, organic detritus, animal droppings and other substances collecting among on their supporting surfaces. The base of

336-473: A different species of bee, so as to enforce proper cross-pollination. A rare achlorophyllous saprophytic orchid growing entirely underground in Australia, Rhizanthella slateri , is never exposed to light, and depends on ants and other terrestrial insects to pollinate it. Catasetum , a genus discussed briefly by Darwin , actually launches its viscid pollinia with explosive force when an insect touches

384-461: A fertile bed where annual coastal flowers and marram grass will thrive. They can house rare carpet flowers , including orchids such as Irish lady's tresses and the Hebridean spotted orchid and other plants such as the yellow rattle . Bird species including the corn crake , twite , dunlin , common redshank and ringed plover , as well as rare insects such as the northern colletes bee,

432-538: A few instances, deserts and rainforests may also be considered plains. Plains in many areas are important for agriculture because where the soils were deposited as sediments they may be deep and fertile , and the flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for livestock . The types of depositional plains include: Erosional plains have been leveled by various agents of denudation such as running water, rivers, wind and glacier which wear out

480-455: A semiterrestrial or rock-hugging (" lithophyte ") orchid, show a sparkling silver and gold veining on a light green background. The cordate leaves of Psychopsiella limminghei are light brownish-green with maroon-puce markings, created by flower pigments. The attractive mottle of the leaves of lady's slippers from tropical and subtropical Asia ( Paphiopedilum ), is caused by uneven distribution of chlorophyll. Also, Phalaenopsis schilleriana

528-538: A single mass. Each time pollination succeeds, thousands of ovules can be fertilized. Pollinators are often visually attracted by the shape and colours of the labellum. However, some Bulbophyllum species attract male fruit flies ( Bactrocera and Zeugodacus spp.) solely via a floral chemical which simultaneously acts as a floral reward (e.g. methyl eugenol , raspberry ketone , or zingerone ) to perform pollination. The flowers may produce attractive odours. Although absent in most species, nectar may be produced in

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576-628: A sticky disc near the top of the column. Just below the pollinia is a second, larger sticky plate called the stigma . The complex mechanisms that orchids have evolved to achieve cross-pollination were investigated by Charles Darwin and described in Fertilisation of Orchids (1862). Orchids have developed highly specialized pollination systems, thus the chances of being pollinated are often scarce, so orchid flowers usually remain receptive for very long periods, rendering unpollinated flowers long-lasting in cultivation. Most orchids deliver pollen in

624-418: Is a pastel pink orchid with leaves spotted dark green and light green. The jewel orchid ( Ludisia discolor ) is grown more for its colorful leaves than its white flowers. Some orchids, such as Dendrophylax lindenii (ghost orchid), Aphyllorchis and Taeniophyllum depend on their green roots for photosynthesis and lack normally developed leaves, as do all of the heterotrophic species. Orchids of

672-417: Is achieved by removing the pollinia with a small instrument such as a toothpick from the pollen parent and transferring them to the seed parent. Some orchids mainly or totally rely on self-pollination , especially in colder regions where pollinators are particularly rare. The caudicles may dry up if the flower has not been visited by any pollinator, and the pollinia then fall directly on the stigma. Otherwise,

720-551: Is found in the tropics . Orchidaceae is one of the two largest families of flowering plants, along with the Asteraceae . It contains about 28,000 currently accepted species distributed across 763 genera . The Orchidaceae family encompasses about 6–11% of all species of seed plants . The largest genera are Bulbophyllum (2,000 species), Epidendrum (1,500 species), Dendrobium (1,400 species) and Pleurothallis (1,000 species). It also includes Vanilla (the genus of

768-542: Is in constant flux, as new studies continue to clarify the relationships between species and groups of species, allowing more taxa at several ranks to be recognized. The Orchidaceae is currently placed in the order Asparagales by the APG III system of 2009. Five subfamilies are recognised. The cladogram below was made according to the APG system of 1998. It represents the view that most botanists had held up to that time. It

816-464: Is kept short by cattle and sheep , which also add trample and add texture to the sward , forming tussocks that favour a number of bird species. The soil is low in a number of key nutrients , including trace elements such as copper , cobalt and manganese , which makes it necessary to feed cattle supplements or take them to summer pastures elsewhere. The sandy soil does not hold nutrients well, making artificial fertilisers ineffective and limiting

864-592: Is often called a backbulb. Backbulbs still hold nutrition for the plant, but then a pseudobulb usually takes over, exploiting the last reserves accumulated in the backbulb, which eventually dies off, too. A pseudobulb typically lives for about five years. Orchids without noticeable pseudobulbs are also said to have growths, an individual component of a sympodial plant. Like most monocots , orchids generally have simple leaves with parallel veins , although some Vanilloideae have reticulate venation . Leaves may be ovate, lanceolate, or orbiculate, and very variable in size on

912-419: Is used as a food reserve for wintry periods, and provides for the development of the other one, from which visible growth develops. In warm and constantly humid climates, many terrestrial orchids do not need pseudobulbs. Epiphytic orchids, those that grow upon a support, have modified aerial roots that can sometimes be a few meters long. In the older parts of the roots, a modified spongy epidermis , called

960-454: The vanilla plant ), the type genus Orchis , and many commonly cultivated plants such as Phalaenopsis and Cattleya . Moreover, since the introduction of tropical species into cultivation in the 19th century, horticulturists have produced many hybrids and cultivars . Orchids are easily distinguished from other plants, as they share some very evident derived characteristics or synapomorphies . Among these are: bilateral symmetry of

1008-491: The Earth's surface. Orchidaceae Orchids are plants that belong to the family Orchidaceae ( / ˌ ɔːr k ɪ ˈ d eɪ s i . iː , - s i . aɪ / ), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Earth except glaciers . The world's richest diversity of orchid genera and species

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1056-428: The accumulation of growth hormones at that point. These shoots are known as keiki . Epipogium aphyllum exhibits a dual reproductive strategy, engaging in both sexual and asexual seed production. The likelihood of apomixis playing a substantial role in successful reproduction appears minimal. Within certain petite orchid species groups, there is a noteworthy preparation of female gametes for fertilization preceding

1104-499: The act of pollination. The ovary typically develops into a capsule that is dehiscent by three or six longitudinal slits, while remaining closed at both ends. The seeds are generally almost microscopic and very numerous, in some species over a million per capsule. After ripening, they blow off like dust particles or spores. Most orchid species lack endosperm in their seed and must enter symbiotic relationships with various mycorrhizal basidiomyceteous fungi that provide them

1152-427: The amount of grazing taking place in many crofting areas, and led some areas to be undergrazed or abandoned. A lack of native seed increases the need for fertilizers and herbicides. Rising sea levels caused by global warming also pose a threat to low-lying coastal areas, leading to increased erosion . In January 1993, the storm which ran MV Braer aground off Shetland eroded 3 metres (9.8 feet) of machair along

1200-541: The anther may rotate and then enter the stigma cavity of the flower (as in Holcoglossum amesianum ). The slipper orchid Paphiopedilum parishii reproduces by self-fertilization . This occurs when the anther changes from a solid to a liquid state and directly contacts the stigma surface without the aid of any pollinating agent or floral assembly. The labellum of the Cypripedioideae is poke bonnet-shaped , and has

1248-415: The beach to form hillocks, which are then blown inland. Human activity has an important role in the creation of the machair. Archaeological evidence indicates that some trees had been cleared for agriculture by around 6000 BC, but there was still some woodland on the coast of South Uist as late as 1549. Seaweed deposited by early farmers provided a protective cover and added nutrients to the soil. The grass

1296-448: The beaches, and decreasing further away from the shore. The pH of a machair is typically greater than 7, i.e. it is alkaline . The inner side of a machair is often wet or marshy, and may contain lochs. The modern theory of machair formation was first set out by William MacGillivray in 1830. He worked out that shell fragments are rolled by waves towards the shore, where they are broken up further. The small shell fragments are blown up

1344-612: The crops that can be grown to certain strains of oats and rye , and bere barley . Machairs have received considerable ecological and conservational attention, chiefly because of their unique ecosystems . Kelp in the sea next to the machair softens the impact of waves, reducing erosion, and when it is washed ashore by storms, forms a protective barrier on the beach. As the kelp decays it provides home to local sand flies which in turn provide rich feeding for flocks of starlings and other passerines , wintering waders , gulls and others. If covered with sand, kelp will compost to form

1392-416: The dune grassland unique to Western Scotland and north-west Ireland. It had been used by naturalists since 1926, but the term was not adopted by scientists until the 1940s. The word is used in a number of Irish, Scottish and Manx placenames to refer to low-lying fertile ground or fields, even in areas where no machair has ever been supported. In Scotland, some Gaelic speakers use machair as a general term for

1440-466: The entire length of Uist and Barra. On 11/12 January 2005 , a storm blowing consistently in excess of hurricane force 12 destroyed hectares of machair. Plain A plain or flatland is a flat expanse of land with a layer of grass that generally does not change much in elevation , and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains , as coastal plains , and as plateaus or uplands . Plains are one of

1488-537: The flower ( zygomorphism ), many resupinate flowers, a nearly always highly modified petal (labellum), fused stamens and carpels , and extremely small seeds . All orchids are perennial herbs that lack any permanent woody structure. They can grow according to two patterns: Terrestrial orchids may be rhizomatous or form corms or tubers . The root caps of terrestrial orchids are smooth and white. Some sympodial terrestrial orchids, such as Orchis and Ophrys , have two subterranean tuberous roots . One

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1536-536: The flower develops, it undergoes a twisting through 180°, called resupination , so that the labellum lies below the column . The labellum functions to attract insects, and in resupinate flowers, also acts as a landing stage, or sometimes a trap. The reproductive parts of an orchid flower are unique in that the stamens and style are joined to form a single structure, the column . Instead of being released singly, thousands of pollen grains are contained in one or two bundles called pollinia that are attached to

1584-436: The flower, it pulls the pollinium out of the anther, as it is connected to the viscidium by the caudicle or stipe. The caudicle then bends and the pollinium is moved forwards and downwards. When the pollinator enters another flower of the same species, the pollinium has taken such position that it will stick to the stigma of the second flower, just below the rostellum, pollinating it. In horticulture, artificial orchid pollination

1632-409: The flowers to gather volatile chemicals they require to synthesize pheromonal attractants. Males of such species as Euglossa imperialis or Eulaema meriana have been observed to leave their territories periodically to forage for aromatic compounds, such as cineole, to synthesize pheromone for attracting and mating with females. Each type of orchid places the pollinia on a different body part of

1680-510: The function of trapping visiting insects. The only exit leads to the anthers that deposit pollen on the visitor. In some extremely specialized orchids, such as the Eurasian genus Ophrys , the labellum is adapted to have a colour, shape, and odour which attracts male insects via mimicry of a receptive female. Pollination happens as the insect attempts to mate with flowers. Many neotropical orchids are pollinated by male orchid bees , which visit

1728-430: The genus Corallorhiza (coralroot orchids) lack leaves altogether and instead have symbiotic or parasitic associations with fungal mycelium, though which they absorb sugars. Orchid flowers have three sepals , three petals and a three-chambered ovary . The three sepals and two of the petals are often similar to each other but one petal is usually highly modified, forming a "lip" or labellum . In most orchid genera, as

1776-505: The great yellow bumblebee ( Bombus distinguendus ) and the moss carder bee ( Bombus muscorum ), are found there. Arable and fallow machair is threatened by changes to the way the land is managed, where the original system of crofts is under threat from a reduction in the number of crofters and the use of "modern" techniques. Changes to the Common Agricultural Policy , where production was decoupled from subsidies , reduced

1824-459: The habitat was listed on Annex I of the Habitats Directive in 1992, leading to the distinction between "machair grassland" and the "machair system". Machair is distinguished from the links on the east coast of Scotland by a lower mineral content, whereas the links are high in silica . Machair plains are highly calcareous , with calcium carbonate concentrations of between 20% and 80% on

1872-455: The individual plant. Their characteristics are often diagnostic. They are normally alternate on the stem, often folded lengthwise along the centre ("plicate"), and have no stipules . Orchid leaves often have siliceous bodies called stegmata in the vascular bundle sheaths (not present in the Orchidoideae ) and are fibrous. The structure of the leaves corresponds to the specific habitat of

1920-401: The largest orchid in the world, Grammatophyllum speciosum (giant orchid), it can reach three meters. Some Dendrobium species have long, canelike pseudobulbs with short, rounded leaves over the whole length; some other orchids have hidden or extremely small pseudobulbs, completely included inside the leaves. With ageing the pseudobulb sheds its leaves and becomes dormant. At this stage it

1968-402: The major landforms on earth, where they are present on all continents, and cover more than one-third of the world's land area. In a valley, a plain is enclosed on two sides, but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains, or by cliffs . Where a geological region contains more than one plain, they may be connected by a pass (sometimes termed

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2016-418: The necessary nutrients to germinate, so almost all orchid species are mycoheterotrophic during germination and reliant upon fungi to complete their lifecycles. Only a handful of orchid species have seed that can germinate without mycorrhiza , namely the species within the genus Disa with hydrochorous seeds. As the chance for a seed to meet a suitable fungus is very small, only a minute fraction of all

2064-658: The plant. Species that typically bask in sunlight, or grow on sites which can be occasionally very dry, have thick, leathery leaves and the laminae are covered by a waxy cuticle to retain their necessary water supply. Shade-loving species, on the other hand, have long, thin leaves. The leaves of most orchids are perennial, that is, they live for several years, while others, especially those with plicate leaves as in Catasetum , shed them annually and develop new leaves together with new pseudobulbs. The leaves of some orchids are considered ornamental. The leaves of Macodes sanderiana ,

2112-400: The rugged surface and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains (almost plain) while plains formed from wind action are called pediplains . Structural plains are relatively undisturbed horizontal surfaces of the Earth. They are structurally depressed areas of the world that make up some of the most extensive natural lowlands on

2160-417: The seeds released grow into adult plants. In cultivation, germination typically takes weeks. Horticultural techniques have been devised for germinating orchid seeds on an artificial nutrient medium, eliminating the requirement of the fungus for germination and greatly aiding the propagation of ornamental orchids. The usual medium for the sowing of orchids in artificial conditions is agar gel combined with

2208-419: The stem of sympodial epiphytes, or in some species essentially the entire stem, may be thickened to form a pseudobulb that contains nutrients and water for drier periods. The pseudobulb typically has a smooth surface with lengthwise grooves, and can have different shapes, often conical or oblong. Its size is very variable; in some small species of Bulbophyllum , it is no longer than two millimeters, while in

2256-455: The whole dune system, including the dune ridge, while others restrict its use to the extensive flat grasslands inland of the dune ridge. In Ireland, the word has been used only in place-names, and the habitat's existence there was only recently confirmed. In Manx Gaelic, 'magher' is a common term for a field. In 1976, an effort was made to strictly define machair , although a number of systems still evade classification. This proved difficult when

2304-594: Was supported by morphological studies , but never received strong support in molecular phylogenetic studies. Apostasioideae : 2 genera and 16 species, south-eastern Asia Cypripedioideae : 5 genera and 130 species, from the temperate regions of the world, as well as tropical America and tropical Asia Vanilloideae : 15 genera and 180 species, humid tropical and subtropical regions, eastern North America Epidendroideae : more than 500 genera and more or less 20,000 species, cosmopolitan Orchidoideae : 208 genera and 3,630 species, cosmopolitan In 2015,

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