The term cultivar most refers to an assemblage of plants selected for desirable characters that are maintained during propagation. More cultivar refers to the most basic classification category of cultivated plants in the International Code of Nomenclature for Cultivated Plants. Most cultivars arose in cultivation. Popular ornamental garden plants like roses, daffodils and azaleas are cultivars produced by careful breeding and selection for floral colour and form; the world's agricultural food crops are exclusively cultivars that have been selected for characters such as improved yield and resistance to disease, few wild plants are now used as food sources. Trees used in forestry are special selections grown for their enhanced quality and yield of timber. Cultivars form a major part of Liberty Hyde Bailey's broader group, the cultigen, defined as a plant whose origin or selection is due to intentional human activity. A cultivar is not the same as a botanical variety, a taxonomic rank below subspecies, there are differences in the rules for creating and using the names of botanical varieties and cultivars.
In recent times, the naming of cultivars has been complicated by the use of statutory patents for plants and recognition of plant breeders' rights. The International Union for the Protection of New Varieties of Plants offers legal protection of plant cultivars to persons or organisations that introduce new cultivars to commerce. UPOV requires that a cultivar be "distinct, uniform", "stable". To be "distinct", it must have characters that distinguish it from any other known cultivar. To be "uniform" and "stable", the cultivar must retain these characters in repeated propagation; the naming of cultivars is an important aspect of cultivated plant taxonomy, the correct naming of a cultivar is prescribed by the Rules and Recommendations of the International Code of Nomenclature for Cultivated Plants. A cultivar is given a cultivar name, which consists of the scientific Latin botanical name followed by a cultivar epithet; the cultivar epithet is in a vernacular language. For example, the full cultivar name of the King Edward potato is Solanum tuberosum'King Edward'.'King Edward' is the cultivar epithet, according to the Rules of the Cultivated Plant Code, is bounded by single quotation marks.
The word cultivar originated from the need to distinguish between wild plants and those with characteristics that arose in cultivation, presently denominated cultigens. This distinction dates to the Greek philosopher Theophrastus, the "Father of Botany", keenly aware of this difference. Botanical historian Alan Morton noted that Theophrastus in his Historia Plantarum "had an inkling of the limits of culturally induced changes and of the importance of genetic constitution"; the International Code of Nomenclature for algae and plants uses as its starting point for modern botanical nomenclature the Latin names in Linnaeus' Species Plantarum and Genera Plantarum. In Species Plantarum, Linnaeus enumerated all plants known to him, either directly or from his extensive reading, he recognised the rank of varietas and he indicated these varieties with letters of the Greek alphabet, such as α, β, λ, before the varietal name, rather than using the abbreviation "var." as is the present convention. Most of the varieties that Linnaeus enumerated were of "garden" origin rather than being wild plants.
In time the need to distinguish between wild plants and those with variations, cultivated increased. In the nineteenth century many "garden-derived" plants were given horticultural names, sometimes in Latin and sometimes in a vernacular language. From circa the 1900s, cultivated plants in Europe were recognised in the Scandinavian and Slavic literature as stamm or sorte, but these words could not be used internationally because, by international agreement, any new denominations had to be in Latin. In the twentieth century an improved international nomenclature was proposed for cultivated plants. Liberty Hyde Bailey of Cornell University in New York, United States created the word cultivar in 1923 when he wrote that: The cultigen is a species, or its equivalent, that has appeared under domestication – the plant is cultigenous. I now propose another name, for a botanical variety, or for a race subordinate to species, that has originated under cultivation, it is the equivalent of the botanical variety except in respect to its origin.
In that essay, Bailey used only the rank of species for the cultigen, but it was obvious to him that many domesticated plants were more like botanical varieties than species, that realization appears to have motivated the suggestion of the new category of cultivar. Bailey created the word cultivar, assumed to be a portmanteau of cultivated and variety. Bailey never explicitly stated the etymology of cultivar, it has been suggested that it is instead a contraction of cultigen and variety, which seems correct; the neologism cultivar was promoted as "euphonious" and "free from ambiguity". The first Cultivated Plant Code of 1953 subsequently commended its use, by 1960 it had achieved common international acceptance; the words cultigen and cultivar may be confused with
Oomycota or oomycetes form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms. They are filamentous, absorptive organisms that reproduce both sexually and asexually. Sexual reproduction of an oospore is the result of contact between hyphae of a male antheridia and female oogonia. Asexual reproduction is the formation of sporangia producing zoospores. Oomycetes occupy both saprophytic and pathogenic lifestyles, include some of the most notorious pathogens of plants, causing devastating diseases such as late blight of potato and sudden oak death. One oomycete, the mycoparasite Pythium oligandrum, is used for biocontrol, attacking plant pathogenic fungi; the oomycetes are often referred to as water molds, although the water-preferring nature which led to that name is not true of most species, which are terrestrial pathogens. The Oomycota have a sparse fossil record. A possible oomycete has been described from Cretaceous amber. "Oomycota" means "egg fungi", referring to the large round oogonia, structures containing the female gametes, that are characteristic of the oomycetes.
The name "water mold" refers to their earlier classification as fungi and their preference for conditions of high humidity and running surface water, characteristic for the basal taxa of the oomycetes. The oomycetes have septa, if they do, they are scarce, appearing at the bases of sporangia, sometimes in older parts of the filaments; some are unicellular, while others are branching. The group was arranged into six orders; the Saprolegniales are the most widespread. Many break down decaying matter; the Leptomitales have wall thickenings that give their continuous cell body the appearance of septation. They bear chitin and reproduce asexually; the Rhipidiales use rhizoids to attach their thallus to the bed of stagnant or polluted water bodies. The Albuginales are considered by some authors to be a family within the Peronosporales, although it has been shown that they are phylogenetically distinct from this order; the Peronosporales too are saprophytic or parasitic on plants, have an aseptate, branching form.
Many of the most damaging agricultural parasites belong to this order. The Lagenidiales are the most primitive; however more this has been expanded considerably. Anisolpidiales Dick 2001 Anisolpidiaceae Karling 1943 Lagenismatales Dick 2001 Lagenismataceae Dick 1995 Salilagenidiales Dick 2001 Salilagenidiaceae Dick 1995 Rozellopsidales Dick 2001 Rozellopsidaceae Dick 1995 Pseudosphaeritaceae Dick 1995 Ectrogellales Ectrogellaceae Haptoglossales Haptoglossaceae Eurychasmales Eurychasmataceae Petersen 1905 Haliphthorales Haliphthoraceae Vishniac 1958 Olpidiopsidales Sirolpidiaceae Cejp 1959 Pontismataceae Petersen 1909 Olpidiopsidaceae Cejp 1959 Atkinsiellales Atkinisellaceae Crypticolaceae Dick 1995 Saprolegniales Achlyaceae Verrucalvaceae Dick 1984 Saprolegniaceae Warm. 1884 Leptomitales Leptomitaceae Kuetz. 1843 Leptolegniellaceae Dick 1971 Rhipidiales Rhipidiaceae Cejp 1959 Albuginales Albuginaceae Schroet. 1893 Peronosporales Salisapiliaceae Pythiaceae Schroet. 1893 Peronosporaceae Warm. 1884 This group was classified among the fungi and treated as protists, based on general morphology and lifestyle.
A cladistic analysis based on modern discoveries about the biology of these organisms supports a close relationship with some photosynthetic organisms, such as brown algae and diatoms. A common taxonomic classification based on these data, places the class Oomycota along with other classes such as Phaeophyceae within the phylum Heterokonta; this relationship is supported by a number of observed differences between the characteristics of oomycetes and fungi. For instance, the cell walls of oomycetes are composed of cellulose rather than chitin and do not have septations. In the vegetative state they have diploid nuclei, whereas fungi have haploid nuclei. Most oomycetes produce self-motile zoospores with two flagella. One flagellum has a "whiplash" morphology, the other a branched "tinsel" morphology; the "tinsel" flagellum is unique to the Kingdom Heterokonta. Spores of the few fungal groups which retain flagella have only one whiplash flagellum. Oomycota and fungi have different metabolic pathways for synthesizing lysine and have a number of enzymes that differ.
The ultrastructure is different, with oomycota having tubular mitochondrial cristae and fungi having flattened cristae. In spite of this evidence to the contrary, many species of oomycetes are still described or listed as types of fungi and may sometimes be referred to as pseudofungi, or lower fungi. Most of the oomycetes produce two distinct types of spores; the main dispersive spores are asexual, self-motile spores called zoospores, which are capable of chemotaxis in surface water. A few oomycetes produce aerial asexual spores, they produce sexual spores, called oospores, that are translucent, double-walled, spherical structures used to survive adverse environmental conditions. Many oomycetes species are economically important, aggressive plant pathogens; some sp
Rhododendron ponticum, called common rhododendron or pontic rhododendron, is a species of Rhododendron native to southern Europe and southwest Asia. R. ponticum is a dense, suckering shrub or small tree growing to 5 m tall 8 m. The leaves are 6 to 18 cm long and 2 to 5 cm wide; the flowers are 3.5 to 5 cm in diameter, violet-purple with small greenish-yellow spots or streaks. The fruit is a dry capsule 1.5 to 2.5 cm long. The two subspecies are: R. p. ponticum, found from Bulgaria east to Georgia R. p. baeticum Hand.-Mazz. Found in Spain and Portugal In Europe, its range includes Spain, northern Portugal, Great Britain and southeast Bulgaria, the last surviving European Tertiary habitat. In Asia it occurs in Turkey, Georgia, the Krasnodar area of southern Russia, the Himalayas, Tajikistan, Northern Pakistan, parts of Kashmir into the northern Republic of India, it is the state flower of Kashmir. Though it had been present in Great Britain before the last Ice Age, it did not recolonise afterwards and the ecology of the island grew up without it.
Its presence today is due to humans introducing it, it naturalises and becomes a pest in some situations covering whole hillsides. In the British Isles, it colonises moorlands, shady woodlands and in areas of acid soils in shaded areas. Fossil evidence shows it had a much wider range across most of southern and western Europe before the Late Glacial Maximum, or until about 20,000 years ago, it was noted by the botanist Joseph Pitton de Tournefort during his travels in the Near East in 1700–02, so received its name from Linnaeus to identify the ancient kingdom on the south shores of the Black Sea, Pontus, in which it grew. At the other end of its range, in southern Spain, Linnaeus' friend and correspondent Clas Alströmer found it growing with oleander, it was introduced to Britain as an ornamental shrub in 1763, planted as cover for game birds. It is now considered to be an invasive species. Rhododendron ponticum subsp. Baeticum is one of the most extensively cultivated rhododendrons in western Europe.
It is used as an ornamental plant in its own right, more as a rootstock onto which other more attractive rhododendrons are grafted. The plants were first grown in Britain in the 1760s, supplied by Conrad Loddiges, became distributed through the commercial nursery trade in the late 18th and early 19th centuries; the roots send up suckers from below the graft allowing it to overtake the intended grafted rhododendron. Honey produced with pollen from the flowers of this plant can be quite poisonous, causing severe hypotension and bradycardia in humans if consumed in sufficient quantities, due to toxic diterpenes. In some parts of the world, a controlled dosage of the honey can be taken to induce hallucinations for spiritual or psychological purposes; such areas include Nepal. Suckering of the root, together with its abundant seed production, has led to it becoming an invasive species over much of western Europe and in parts of New Zealand. Rhododendron control is a key element in nature conservation in those areas.
Conservation organisations in Britain now believe R. ponticum has become "a severe problem" in the native Atlantic oakwoods of the west highlands of Scotland and in Wales, on heathlands in southern England, crowding out the native flora. Clearance strategies have been developed, including the flailing and cutting down of plants with follow-up herbicide spraying. Injection of herbicide into individual plants has been found to be more effective. A recent study in the journal Functional Ecology showed that invasive Rhododendron nectar was toxic to European honeybees, killing individuals within hours of consumption, it paralyzed bees of the species Andrena carantonica, a solitary mining bee. Bees became paralysed and exhibited excessive grooming or other distress behaviours after feeding on Rhododendron nectar, ate less food than bees fed a control nectar. In contrast the buff-tailed bumblebee was not affected by the rhododendron nectar. Catawbiense hybrid – hybrid with R.ponticum Flora Europaea: Rhododendron ponticum Rhododendron Ponticum is the emblem and symbol of Bulgaria's most exotic National Park – The Strandja mountains "Rhododendron ponticum".
Germplasm Resources Information Network. Agricultural Research Service, United States Department of Agriculture. Centre for Conservation Strategy: Rhododendron ponticum in Britain Danish Rhododendron Society: Rhododendron ponticum in Europe Milne, R. I. & Abbott, R. J.. Origin and evolution of invasive naturalized material of Rhododendron ponticum L. in the British Isles. Molecular Ecology 9: 541–556 Abstract
Azaleas are flowering shrubs in the genus Rhododendron the former sections Tsutsuji and Pentanthera. Azaleas bloom in the spring, their flowers lasting several weeks. Shade tolerant, they prefer living under trees, they are part of the family Ericaceae. Plant enthusiasts have selectively bred azaleas for hundreds of years; this human selection has produced over 10,000 different cultivars. Azalea seeds can be collected and germinated. Azaleas are slow-growing and do best in well-drained acidic soil. Fertilizer needs are low; some species need regular pruning. Azaleas are native to several continents including Asia and North America, they are planted abundantly as ornamentals in the southeastern US, southern Asia, parts of southwest Europe. According to azalea historian Fred Galle, in the United States, Azalea indica was first introduced to the outdoor landscape in the 1830s at the rice plantation Magnolia-on-the-Ashley in Charleston, South Carolina. From Philadelphia, where they were grown only in greenhouses, John Grimke Drayton imported the plants for use in his estate garden.
With encouragement from Charles Sprague Sargent from Harvard's Arnold Arboretum, Magnolia Gardens was opened to the public in 1871, following the American Civil War. Magnolia is one of the oldest public gardens in America. Since the late 19th century, in late March and early April, thousands visit to see the azaleas bloom in their full glory. Azalea leafy gall can be destructive to azalea leaves during the early spring. Hand picking infected leaves is the recommended method of control, they can be subject to phytophthora root rot in moist, hot conditions. In Chinese culture, the azalea is known as "thinking of home bush", is immortalized in the poetry of Du Fu; the azalea is one of the symbols of the city of São Paulo, Brazil. Azaleas and rhododendrons were once so infamous for their toxicity that to receive a bouquet of their flowers in a black vase was a well-known death threat. In addition to being renowned for its beauty, the azalea is highly toxic—it contains andromedotoxins in both its leaves and nectar, including honey from the nectar.
Bees are deliberately fed on Azalea/Rhododendron nectar in some parts of Turkey, producing a mind-altering medicinal, lethal honey known as "mad honey". According to the ancient Roman historian Pliny the Elder in his Natural History, an army invading Pontus in Turkey was poisoned with such honey, resulting in their defeat. Motoyama, Kōchi has a flower festival in which the blooming of Tsutsuji is celebrated and Tatebayashi, Gunma is famous for its Azalea Hill Park, Tsutsuji-ga-oka. Nezu Shrine in Bunkyo, holds a Tsutsuji Matsuri from early April until early May. Higashi Village has hosted an azalea festival each year since 1976; the village's 50,000 azalea plants draw an estimated 60,000 to 80,000 visitors each year. Sobaeksan, one of the 12 well-known Sobaek Mountains, lying on the border between Chungbuk Province and Gyeongbuk has a royal azalea festival held on May every year. Sobaeksan has an azalea colony dotted around Biro mountaintop and Yonwha early in May; when royal azaleas have turned pink in the end of May, it looks.
The Ma On Shan Azalea Festival is held in Ma On Shan, where six native species are found in the area. The festival has been held since 2004. Many cities in the United States have festivals in the spring celebrating the blooms of the azalea, including Summerville, South Carolina; the Azalea Trail is a designated path, planted with azaleas in private gardens, through Mobile, Alabama. The Azalea Trail Run is an annual road running event held there in late March. Mobile, Alabama is home to the Azalea Trail Maids, fifty women chosen to serve as ambassadors of the city while wearing antebellum dresses, who participated in a three-day festival, but now operate throughout the year; the Azalea Society of America designated Houston, Texas, an "azalea city". The River Oaks Garden Club has conducted the Houston Azalea Trail every spring since 1935. List of Award of Garden Merit rhododendrons List of plants poisonous to equines "Azalea". Encyclopædia Britannica. 1911. Azalea Society of America American Rhododendron Society: What is an Azalea?
Azalea Collection of the U. S. National Arboretum Azalea Collection of Botany garten Pruhonice CZ
Thuja is a genus of coniferous trees in the Cupressaceae. There are two native to North America and three native to eastern Asia; the genus is sister to Thujopsis. Members are known as arborvitaes, thujas or cedars. Thuja are evergreen trees growing from 10 to 200 feet tall, with stringy-textured reddish-brown bark; the shoots are flat, with side shoots only in a single plane. The leaves are scale-like 1–10 mm long, except young seedlings in their first year, which have needle-like leaves; the scale leaves are arranged in alternating decussate pairs in four rows along the twigs. The male cones are small and are located at the tips of the twigs; the female cones start out inconspicuous, but grow to about 1–2 cm long at maturity when 6–8 months old. The five species in the genus Thuja are small to large evergreen trees with flattened branchlets; the leaves are arranged in flattened fan shaped groupings with resin-glands, oppositely grouped in 4 ranks. The mature leaves are different from younger leaves, with those on larger branchlets having sharp, free apices.
The leaves on flattened lateral branchlets are crowded into appressed groups and scale-like and the lateral pairs are keeled. With the exception of T. plicata, the lateral leaves are shorter than the facial leaves. The solitary flowers are produced terminally. Pollen cones with 2-6 pairs of 2-4 pollen sacked sporophylls. Seed cones ellipsoid 9-14mm long, they mature and open the first year; the thin woody cone scales number from 4-6 pairs and are persistent and overlapping, with an oblong shape, they are basifixed. The central 2-3 pairs of cone scales are fertile; the seed cones produce 1 to 3 seeds per scale, the seeds are lenticular in shape and 2 winged. Seedlings produce 2 cotyledons. A hybrid between T. standishi and T. plicata has been named as the cultivar Thuja'Green Giant'. Another distinct and only distantly related species treated as Thuja orientalis, is now treated in a genus of its own, as Platycladus orientalis; the closest relatives of Thuja are Thujopsis dolabrata, distinct in its thicker foliage and stouter cones, Tetraclinis articulata, distinct in its quadrangular foliage and cones with four thick, woody scales.
The genus Thuja, like many other forms of conifers, is represented by ancestral forms in Cretaceous rocks of northern Europe, with the advance of time is found to migrate from northerly to more southerly regions, until during Pliocene time it disappeared from Europe. Thuja is known in the Miocene beds of the Dakotas; the five extant species are: Thuja koraiensis Nakai – Korean thuja - Jilin, Korea Thuja occidentalis L. – eastern arborvitae, northern whitecedar - E Canada, E United States Thuja plicata Donn ex D. Don – western redcedar - from Alaska to Mendocino County in California Thuja standishii Carrière – Japanese thuja - Honshu, Shikoku Thuja sutchuenensis Carrière – Sichuan thuja - Sichuan, Chongqing China extinct in the wildSpecies placed in Thuja include: Austrocedrus chilensis Pic. Serm. & Bizzarri Callitris rhomboidea R. Br. Ex Rich. Cupressus nootkatensis D. Don Dacrycarpus imbricatus de Laub Glyptostrobus pensilis K. Koch Libocedrus plumosa Sarg. Platycladus orientalis Franco Tamarix aphylla H.
Karst. Tetraclinis articulata Mast. Thujopsis dolabrata Siebold & Zucc. Widdringtonia nodiflora Powrie and many more Thuja species are used as food plants by the larvae of some Lepidoptera species including autumnal moth, the engrailed and juniper pug; the foliage is readily eaten by deer, where deer population density is high, can adversely affect the growth of young trees and the establishment of seedlings. They are grown as ornamental trees, extensively used for hedges. A number of cultivars are used in landscapes. Homeowners will sometimes plant them as privacy trees; the cultivar'Green Giant' is popular as a vigorous hedging plant, growing up to 80 cm/year when young. The wood is light and aromatic, it can be split and resists decay. The wood has been used for many applications from making chests. Thuja poles are often used to make fence posts and rails; the wood of Thuja plicata is used for guitar sound boards. Its combination of light weight and resistance to decay has led to T. plicata being used for the construction of bee hives.
Oil of thuja contains the terpene thujone, studied for its GABA receptor antagonizing effects, with lethal properties. Cedarwood oil and cedar leaf oil, which are derived from Thuja occidentalis, have different properties and uses; the natives of Canada used the scaled leaves of Thuja occidentalis to make a tea, shown to contain 50 mg of vitamin C per 100 grams. In the 19th century Thuja was used as an externally applied tincture or ointment for the treatment of warts and thrush, a local injection of the tincture was used for t
Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Depending on taxonomic viewpoint, between 50 and 67 species of junipers are distributed throughout the Northern Hemisphere, from the Arctic, south to tropical Africa, from Ziarat, east to eastern Tibet in the Old World, in the mountains of Central America; the highest-known juniper forest occurs at an altitude of 16,000 ft in southeastern Tibet and the northern Himalayas, creating one of the highest tree-lines on earth. Junipers vary in size and shape from tall trees, 20–40 m tall, to columnar or low-spreading shrubs with long, trailing branches, they are evergreen with needle-like and/or scale-like leaves. They can be either dioecious; the female seed cones are distinctive, with fleshy, fruit-like coalescing scales which fuse together to form a "berry"-like structure, 4–27 mm long, with one to 12 unwinged, hard-shelled seeds. In some species, these "berries" are red-brown or orange; the seed maturation time varies between species from 6 to 18 months after pollination.
The male cones are similar to those of other Cupressaceae, with six to 20 scales. In zones 7 through 10, junipers can release pollen several times each year. A few species of junipers bloom in autumn, while most species pollinate from early winter until late spring. Many junipers have two types of leaves; when juvenile foliage occurs on mature plants, it is most found on shaded shoots, with adult foliage in full sunlight. Leaves on fast-growing'whip' shoots are intermediate between juvenile and adult. In some species, all the foliage is with no scale leaves. In some of these, the needles are jointed at the base, in others, the needles merge smoothly with the stem, not jointed; the needle-leaves of junipers are hard and sharp, making the juvenile foliage prickly to handle. This can be a valuable identification feature in seedlings, as the otherwise similar juvenile foliage of cypresses and other related genera is soft and not prickly. Juniper is the exclusive food plant of the larvae of some Lepidoptera species, including Bucculatrix inusitata and juniper carpet, is eaten by the larvae of other Lepidoptera species such as Chionodes electella, Chionodes viduella, juniper pug, pine beauty.
Junipers are gymnosperms, which means they have no flowers or fruits. Depending on the species, the seeds they produce take 1 -- 3 years; the impermeable coat of the seed keeps water from getting in and protects the embryo when being dispersed. It can result in a long dormancy, broken by physically damaging the seed coat. Dispersal can occur from being swallowed whole by mammals; the resistance of the seed coat allows it to be passed down through the digestive system and out without being destroyed along the way. These seeds last a long time, as they can be dispersed long distances over the course of a few years; the number of juniper species is in dispute, with two recent studies giving different totals, Farjon accepting 52 species, Adams accepting 67 species. The junipers are divided into several sections, though which species belong to which sections is still far from clear, with research still on-going; the section Juniperus is an obvious monophyletic group though. Juniperus sect. Juniperus: Needle-leaf junipers.
The adult leaves are needle-like, in whorls of three, jointed at the base. Juniperus sect. Juniperus subsect. Juniperus: Cones with 3 separate seeds. Juniperus communis – Common juniper Juniperus communis subsp. Alpina – Alpine juniper Juniperus conferta – Shore juniper Juniperus rigida – Temple juniper or needle juniper Juniperus sect. Juniperus subsect. Oxycedrus: Cones with 3 separate seeds. Juniperus brevifolia – Azores juniper Juniperus cedrus – Canary Islands juniper Juniperus deltoides – Eastern prickly juniper Juniperus formosana – Chinese prickly juniper Juniperus lutchuensis – Ryukyu juniper Juniperus navicularis – Portuguese prickly juniper Juniperus oxycedrus – Western prickly juniper or cade juniper Juniperus macrocarpa – Large-berry juniper Juniperus sect. Juniperus subsect. Caryocedrus: Cones with 3 seeds fused together. Juniperus drupacea – Syrian juniperJuniperus sect. Sabina: Scale-leaf junipers; the adult leaves are scale-like, similar to those of Cupressus species, in opposite pairs or whorls of three, the juvenile needle-like leaves are not jointed at the base.
Provisionally, all the other junipers are included here. Old World species Juniperus chinensis – Chinese juniper Juniperus convallium – Mekong juniper Juniperus excelsa – Greek juniper Juniperus excelsa polycarpos – Persian juniper Juniperus foetidissima – Stinking juniper Juniperus indica – Black juniper Juniperus komarovii – Komarov's juniper Juniperus phoenicea – Phoenicean juniper Juniperus pingii – Ping juniper Juniperus procera – East African juniper Juniperus procumbens – Ibuki juniper Juniperu
The heterokonts or stramenopiles are a major line of eukaryotes containing more than 25,000 known species. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which are a primary component of plankton. Other notable members of the Stramenopiles include the parasitic oomycetes, including Phytophthora of Irish potato famine infamy and Pythium which causes seed rot and damping off; the name "heterokont" refers to the type of motile life cycle stage, in which the flagellated cells possess two differently shaped flagella. In 1899, Luther created "Heterokontae" for some algae with unequal flagella, today called Xanthophyceae; some authors would include other groups in Heterokonta, expanding its sense. The origin of the other name of the group, "stramenopile", is explained by David and Adl et al.: Regarding the spelling of stramenopile, it was spelled stramenopile. The Latin word for straw is strāmĭnĕus, -a, -um, adj. made of straw—thus, it should have been spelled straminopile or straminipile.
However, Patterson stated that this is a common name and, as a common name, it can be spelled as Patterson chooses. If he had stipulated that the name was a formal name, governed by rules of nomenclature his spelling would have been an orthogonal mutation and one would correct the spelling in subsequent publications. But, it was not Patterson’s desire to use the term in a formal sense. Thus, if we use it in a formal sense, it must be formally described. However, here is the strange part of this, many people liked the name, but wanted it to be used formally. So they capitalized the first letter, made it Stramenopiles. Many heterokonts are unicellular flagellates, most others produce flagellated cells at some point in their lifecycles, for instance as gametes or zoospores; the name heterokont refers to the characteristic form of these cells, which have two unequal flagella. The anterior straminipilous flagellum is covered with one or two rows of lateral bristles or mastigonemes, which are tripartite, while the posterior flagellum is whiplike and shorter, or sometimes reduced to a basal body.
The flagella are inserted subapically or laterally, are supported by four microtubule roots in a distinctive pattern. Mastigonemes are manufactured from glycoproteins in the cell's endoplasmic reticulum before being transported to the anterior flagella's surface; when the straminipilous flagellum moves, the mastigonemes create a retrograde current, pulling the cell through the water or bringing in food. The mastigonemes have a peculiar tripartite structure, which may be taken as the defining characteristic of the heterokonts, thereby including a few protists that do not produce cells with the typical heterokont form. Mastigonemes have been lost in a few heterkont lines, most notably the diatoms. Many heterokonts are algae with chloroplasts surrounded by four membranes, which are counted from the outermost to the innermost membrane; the first membrane is continuous with the host's chloroplast endoplasmic reticulum, or cER. The second membrane presents a barrier between the lumen of the cER and the primary endosymbiont or chloroplast, which represents the next two membranes, within which the thylakoid membranes are found.
This arrangement of membranes suggests that heterokont chloroplasts were obtained from the reduction of a symbiotic red algal eukaryote, which had arisen by evolutionary divergence from the monophyletic primary endosymbiotic ancestor, thought to have given rise to all eukaryotic photoautotrophs. The chloroplasts characteristically contain chlorophyll a and chlorophyll c, the accessory pigment fucoxanthin, giving them a golden-brown or brownish-green color. Most basal heterokonts are colorless; this suggests. However, fucoxanthin-containing chloroplasts are found among the haptophytes; these two groups may have a common ancestry, also a common phylogenetic history with cryptomonads, being grouped by some authors in the Chromista. This may be interpreted as suggesting that the ancestral heterokont was an alga, all colorless groups arose through loss of the secondary endosymbiont and its chloroplast; as noted above, classification varies considerably. The heterokont algae were treated as two divisions, first within the kingdom Plantae and the Protista: Division Chrysophyta Class Chrysophyceae Class Bacillariophyceae Division Phaeophyta In this scheme, the Chrysophyceae is paraphyletic to both other groups.
As a result, various members have been given their own classes and divisions. Recent systems treat these as classes within a single division, called the Heterokontophyta, Chromophyta, or Ochrophyta; this is not universal, however. The discovery that oomycetes and hyphochytrids are related to these algae, rather than fungi, as thought, has led many authors to include these two groups among the heterokonts. Should it turn out that they evolved from colored ancestors, the heterokont group would be paraphyletic in their absence. Once again, howe