72-545: Vanda sanderiana is a species of orchid . It is commonly called Waling-waling in the Philippines and is also called Sander's Vanda , after Henry Frederick Conrad Sander , a noted orchidologist . The orchid is considered to be the "Queen of Philippine flowers" and is worshiped as a diwata by the indigenous Bagobo people. Heinrich Gustav Reichenbach named it as Vanda sanderiana . It has two forms, pink and white, also referred to as alba . M. Roebelin discovered
144-464: 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
216-540: A phylogenetic study showed strong statistical support for the following topology of the orchid tree , using 9 kb of plastid and nuclear DNA from 7 genes , a topology that was confirmed by a phylogenomic study in the same year. Apostasioideae Vanilloideae Symmetry (biology)#Bilateral symmetry Symmetry in biology refers to the symmetry observed in organisms , including plants, animals, fungi , and bacteria . External symmetry can be easily seen by just looking at an organism. For example,
288-401: 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
360-474: 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
432-605: A streamlined body. Many flowers are also radially symmetric, or " actinomorphic ". Roughly identical floral structures – petals , sepals , and stamens – occur at regular intervals around the axis of the flower, which is often the female reproductive organ containing the carpel , style and stigma . Three-fold triradial symmetry was present in Trilobozoa from the Late Ediacaran period. Four-fold tetramerism appears in some jellyfish, such as Aurelia marginalis . This
504-551: 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
576-406: A bottom surface, or a front and a back. George Cuvier classified animals with radial symmetry in the taxon Radiata ( Zoophytes ), which is now generally accepted to be an assemblage of different animal phyla that do not share a single common ancestor (a polyphyletic group). Most radially symmetric animals are symmetrical about an axis extending from the center of the oral surface, which contains
648-473: 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
720-447: A distinct head and tail) is called cephalization . It is also argued that the development of an AP axis is important in locomotion – bilateral symmetry gives the body an intrinsic direction and allows streamlining to reduce drag . In addition to animals, the flowers of some plants also show bilateral symmetry. Such plants are referred to as zygomorphic and include the orchid ( Orchidaceae ) and pea ( Fabaceae ) families, and most of
792-532: A number of species of Radiolaria , some of whose skeletons are shaped like various regular polyhedra. Examples include Circoporus octahedrus , Circogonia icosahedra , Lithocubus geometricus and Circorrhegma dodecahedra . The shapes of these creatures should be obvious from their names. Tetrahedral symmetry is not present in Callimitra agnesae . Spherical symmetry is characterised by the ability to draw an endless, or great but finite, number of symmetry axes through
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#1732901676080864-487: A particular direction. This creates a unidirectional flow of signalling molecules causing these signals to accumulate on one side of the embryo and not the other. This results in the activation of different developmental pathways on each side, and subsequent asymmetry. Much of the investigation of the genetic basis of symmetry breaking has been done on chick embryos. In chick embryos the left side expresses genes called NODAL and LEFTY2 that activate PITX2 to signal
936-400: A repeating pattern around a central axis such that they can be separated into several identical pieces when cut through the central point, much like pieces of a pie. Typically, this involves repeating a body part 4, 5, 6 or 8 times around the axis – referred to as tetramerism, pentamerism, hexamerism and octamerism, respectively. Such organisms exhibit no left or right sides but do have a top and
1008-455: 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
1080-538: 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
1152-628: 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
1224-418: 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
1296-447: Is a severe over-simplification as bacterial cells can be curved, bent, flattened, oblong spheroids and many more shapes. Due to the huge number of bacteria considered to be cocci (coccus if a single cell), it is unlikely that all of these show true spherical symmetry. It is important to distinguish between the generalized use of the word 'spherical' to describe organisms at ease, and the true meaning of spherical symmetry. The same situation
1368-417: 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,
1440-495: Is an anterior – posterior (AP) axis which can be visualised as an imaginary axis running from the head or mouth to the tail or other end of an organism. The second is the dorsal – ventral (DV) axis which runs perpendicular to the AP axis. During development the AP axis is always specified before the DV axis, which is known as the second embryonic axis . The AP axis is essential in defining
1512-533: Is due to the expression of CYCLOIDEA genes. Evidence for the role of the CYCLOIDEA gene family comes from mutations in these genes which cause a reversion to radial symmetry. The CYCLOIDEA genes encode transcription factors , proteins which control the expression of other genes. This allows their expression to influence developmental pathways relating to symmetry. For example, in Antirrhinum majus , CYCLOIDEA
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#17329016760801584-407: Is expressed during early development in the dorsal domain of the flower meristem and continues to be expressed later on in the dorsal petals to control their size and shape. It is believed that the evolution of specialized pollinators may play a part in the transition of radially symmetrical flowers to bilaterally symmetrical flowers. Symmetry is often selected for in the evolution of animals. This
1656-551: 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
1728-429: Is illustrated by the fact that groups of animals have traditionally been defined by this feature in taxonomic groupings. The Radiata , animals with radial symmetry, formed one of the four branches of Georges Cuvier 's classification of the animal kingdom . Meanwhile, Bilateria is a taxonomic grouping still used today to represent organisms with embryonic bilateral symmetry. Organisms with radial symmetry show
1800-400: Is immediately obvious when looking at the jellyfish due to the presence of four gonads , visible through its translucent body. This radial symmetry is ecologically important in allowing the jellyfish to detect and respond to stimuli (mainly food and danger) from all directions. Flowering plants show five-fold pentamerism, in many of their flowers and fruits. This is easily seen through
1872-542: 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
1944-430: Is known to be under selection, the evolutionary history of different types of symmetry in animals is an area of extensive debate. Traditionally it has been suggested that bilateral animals evolved from a radial ancestor . Cnidarians , a phylum containing animals with radial symmetry, are the most closely related group to the bilaterians. Cnidarians are one of two groups of early animals considered to have defined structure,
2016-442: Is more common than originally accounted for. Like all the traits of organisms, symmetry (or indeed asymmetry) evolves due to an advantage to the organism – a process of natural selection . This involves changes in the frequency of symmetry-related genes throughout time. Early flowering plants had radially symmetric flowers but since then many plants have evolved bilaterally symmetrical flowers. The evolution of bilateral symmetry
2088-592: 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
2160-415: Is seen in the description of viruses – 'spherical' viruses do not necessarily show spherical symmetry, being usually icosahedral. Organisms with bilateral symmetry contain a single plane of symmetry, the sagittal plane , which divides the organism into two roughly mirror image left and right halves – approximate reflectional symmetry. Animals with bilateral symmetry are classified into a large group called
2232-503: Is that an ancestral animal had no symmetry (was asymmetric) before cnidarians and bilaterians separated into different evolutionary lineages . Radial symmetry could have then evolved in cnidarians and bilateral symmetry in bilaterians. Alternatively, the second suggestion is that an ancestor of cnidarians and bilaterians had bilateral symmetry before the cnidarians evolved and became different by having radial symmetry. Both potential explanations are being explored and evidence continues to fuel
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2304-427: Is unsurprising since asymmetry is often an indication of unfitness – either defects during development or injuries throughout a lifetime. This is most apparent during mating during which females of some species select males with highly symmetrical features. Additionally, female barn swallows , a species where adults have long tail streamers, prefer to mate with males that have the most symmetrical tails. While symmetry
2376-419: 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
2448-708: The Sampaguita . In 2013, a bill was passed by the Philippine Senate declaring the Waling-waling as a national flower alongside the Sampaguita. However, the House Bill 5655 was vetoed by President Benigno Aquino III citing that other means were available to promote the protection and preservation of the orchid without declaring it a second national flower. The Philippine Orchid Society, which incorporates an image of
2520-450: The bilateria , which contains 99% of all animals (comprising over 32 phyla and 1 million described species). All bilaterians have some asymmetrical features; for example, the human heart and liver are positioned asymmetrically despite the body having external bilateral symmetry. The bilateral symmetry of bilaterians is a complex trait which develops due to the expression of many genes . The bilateria have two axes of polarity . The first
2592-419: The body plans of most multicellular organisms exhibit, and are defined by, some form of symmetry. There are only a few types of symmetry which are possible in body plans. These are radial (cylindrical) symmetry, bilateral , biradial and spherical symmetry. While the classification of viruses as an "organism" remains controversial, viruses also contain icosahedral symmetry . The importance of symmetry
2664-655: The corals and sea anemones (class Anthozoa ), which are divided into two groups based on their symmetry. The most common corals in the subclass Hexacorallia have a hexameric body plan; their polyps have six-fold internal symmetry and a number of tentacles that is a multiple of six. Octamerism is found in corals of the subclass Octocorallia . These have polyps with eight tentacles and octameric radial symmetry. The octopus , however, has bilateral symmetry, despite its eight arms. Icosahedral symmetry occurs in an organism which contains 60 subunits generated by 20 faces, each an equilateral triangle , and 12 corners. Within
2736-402: The icosahedron there is 2-fold, 3-fold and 5-fold symmetry . Many viruses, including canine parvovirus , show this form of symmetry due to the presence of an icosahedral viral shell . Such symmetry has evolved because it allows the viral particle to be built up of repetitive subunits consisting of a limited number of structural proteins (encoded by viral genes ), thereby saving space in
2808-454: 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
2880-428: 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
2952-499: 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
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3024-434: The anatomical asymmetry which we observe. These levels include asymmetric gene expression, protein expression, and activity of cells. For example, left–right asymmetry in mammals has been investigated extensively in the embryos of mice. Such studies have led to support for the nodal flow hypothesis. In a region of the embryo referred to as the node there are small hair-like structures ( monocilia ) that all rotate together in
3096-541: 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
3168-403: The arrangement of five carpels (seed pockets) in an apple when cut transversely . Among animals, only the echinoderms such as sea stars , sea urchins , and sea lilies are pentamerous as adults, with five arms arranged around the mouth. Being bilaterian animals, however, they initially develop with mirror symmetry as larvae, then gain pentaradial symmetry later. Hexamerism is found in
3240-471: The body of an organism. Importantly, unlike in mathematics, symmetry in biology is always approximate. For example, plant leaves – while considered symmetrical – rarely match up exactly when folded in half. Symmetry is one class of patterns in nature whereby there is near-repetition of the pattern element, either by reflection or rotation . While sponges and placozoans represent two groups of animals which do not show any symmetry (i.e. are asymmetrical),
3312-567: The body. This means that spherical symmetry occurs in an organism if it is able to be cut into two identical halves through any cut that runs through the organism's center. True spherical symmetry is not found in animal body plans. Organisms which show approximate spherical symmetry include the freshwater green alga Volvox . Bacteria are often referred to as having a 'spherical' shape. Bacteria are categorized based on their shapes into three classes: cocci (spherical-shaped), bacillus (rod-shaped) and spirochetes (spiral-shaped) cells. In reality, this
3384-458: The debate. Although asymmetry is typically associated with being unfit, some species have evolved to be asymmetrical as an important adaptation . Many members of the phylum Porifera (sponges) have no symmetry, though some are radially symmetric. The presence of these asymmetrical features requires a process of symmetry breaking during development, both in plants and animals. Symmetry breaking occurs at several different levels in order to generate
3456-464: The development of left side structures. Whereas, the right side does not express PITX2 and consequently develops right side structures. A more complete pathway is shown in the image at the side of the page. For more information about symmetry breaking in animals please refer to the left–right asymmetry page. Plants also show asymmetry. For example the direction of helical growth in Arabidopsis ,
3528-496: The evolution of bilateral symmetry from a radially symmetric ancestor. The animal group with the most obvious biradial symmetry is the ctenophores . In ctenophores the two planes of symmetry are (1) the plane of the tentacles and (2) the plane of the pharynx. In addition to this group, evidence for biradial symmetry has even been found in the 'perfectly radial' freshwater polyp Hydra (a cnidarian). Biradial symmetry, especially when considering both internal and external features,
3600-449: The face of a human being has a plane of symmetry down its centre, or a pine cone displays a clear symmetrical spiral pattern. Internal features can also show symmetry, for example the tubes in the human body (responsible for transporting gases , nutrients , and waste products) which are cylindrical and have several planes of symmetry. Biological symmetry can be thought of as a balanced distribution of duplicate body parts or shapes within
3672-447: The figwort family ( Scrophulariaceae ). The leaves of plants also commonly show approximate bilateral symmetry. Biradial symmetry is found in organisms which show morphological features (internal or external) of both bilateral and radial symmetry. Unlike radially symmetrical organisms which can be divided equally along many planes, biradial organisms can only be cut equally along two planes. This could represent an intermediate stage in
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#17329016760803744-537: 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
3816-536: 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
3888-490: The flower in its logo , states that the species has three varieties: 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
3960-436: 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
4032-409: 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
4104-510: 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
4176-430: 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
4248-455: 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
4320-401: 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
4392-608: The most commonly studied model plant, shows left-handedness. Interestingly, the genes involved in this asymmetry are similar (closely related) to those in animal asymmetry – both LEFTY1 and LEFTY2 play a role. In the same way as animals, symmetry breaking in plants can occur at a molecular (genes/proteins), subcellular, cellular, tissue and organ level. Fluctuating asymmetry (FA), is a form of biological asymmetry , along with anti-symmetry and direction asymmetry. Fluctuating asymmetry refers to small, random deviations away from perfect bilateral symmetry. This deviation from perfection
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#17329016760804464-566: The mouth, to the center of the opposite (aboral) end. Animals in the phyla Cnidaria and Echinodermata generally show radial symmetry, although many sea anemones and some corals within the Cnidaria have bilateral symmetry defined by a single structure, the siphonoglyph . Radial symmetry is especially suitable for sessile animals such as the sea anemone, floating animals such as jellyfish , and slow moving organisms such as starfish ; whereas bilateral symmetry favours locomotion by generating
4536-418: 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
4608-531: The original pink variety in the Philippines in 1881 or 1882. Rudolf Schlechter separated Euanthe from Vanda in 1914 due to structural differences in the flowers. For breeding purposes and registration by the Royal Horticultural Society , however, it is still treated as a Vanda. Vanda sanderiana is endemic to Mindanao in the provinces of Davao , Cotabato , and Zamboanga where it is found on
4680-658: 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 ,
4752-475: The polarity of bilateria and allowing the development of a front and back to give the organism direction. The front end encounters the environment before the rest of the body so sensory organs such as eyes tend to be clustered there. This is also the site where a mouth develops since it is the first part of the body to encounter food. Therefore, a distinct head, with sense organs connected to a central nervous system, tends to develop. This pattern of development (with
4824-418: The second being the ctenophores . Ctenophores show biradial symmetry leading to the suggestion that they represent an intermediate step in the evolution of bilateral symmetry from radial symmetry. Interpretations based only on morphology are not sufficient to explain the evolution of symmetry. Two different explanations are proposed for the different symmetries in cnidarians and bilateria. The first suggestion
4896-417: 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
4968-419: 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
5040-455: The trunks of dipterocarp trees at elevations below 500 meters. Over-collected, the plant is considered rare in nature. It is often used in hybridization . Studies have shown that when raised at high altitude , the plant bears flowers early. In 2004, a motion was filed in the House of Representatives of the Philippines to declare the Waling-waling as the country's national flower, replacing
5112-488: The viral genome . The icosahedral symmetry can still be maintained with more than 60 subunits, but only in multiples of 60. For example, the T=3 Tomato bushy stunt virus has 60x3 protein subunits (180 copies of the same structural protein). Although these viruses are often referred to as 'spherical', they do not show true mathematical spherical symmetry. In the early 20th century, Ernst Haeckel described (Haeckel, 1904)
5184-594: 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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