Treeline | The Canadian Encyclopedia

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and access the interactive map.</p> <a href="https://www.thecanadianencyclopedia.ca/en/members/register" class="b b-md b-primary">Create Account </a> </div> </div> </div> </div> <div class="sidebar-layout"> <div class="sidebar js-sidebar" id="article-sidebar"> <article-sidebar initial-article-data="{"article":{"id":"77320","author_text":"J. Stan Rowe And Serge Payette","revisor":null,"major_update":null,"trigger_warning":0,"views":0,"shares":0,"type":"article","itunes_songs":null,"indigo":null,"itunes_title_en":null,"itunes_title_fr":null,"indigo_title_en":null,"indigo_title_fr":null,"status":"published","schedule_from":null,"schedule_until":null,"created_at":"2007-01-30T00:00:00.000000Z","updated_at":"2015-06-19T19:55:46.000000Z","deleted_at":null,"title":"Treeline","slug":"treeline","alt_slug":null,"summary":"The treeline is controlled by CLIMATE in interaction with SOIL. In the North, it is correlated generally with the modal (most common) position of the southern edge of the arctic front in summer, and with such temperature indices as the July 10\u00b0C isotherm.","body":"<div><img src=\"https:\/\/d3d0lqu00lnqvz.cloudfront.net\/media\/media\/thumbnails\/e2366ba0-9f18-4eec-968d-6f1076b512b0.jpg\" title='Snow-covered Evergreen' alt='Snow-covered Evergreen' \/><figcaption>Most conifers are evergreens, retaining their needlelike leaves for several years (Corel Professional Photos).<\/figcaption><\/div>\r\n<h3>Treeline<\/h3>\r\n<p>\r\n\t<a href=\"javascript:DisplayMedia('1995', '1995', '1995', 400, 268, 0, 0, 0);\" name=\"1995\"><\/a> The treeline marks the limit of <a href=\"\/article\/trees\/\">trees<\/a> latitudinally on continental plains and altitudinally on highlands and mountains (where it is sometimes called the timberline). Tree species still occur beyond this limit, but in shrub form, extending to the \"tree-species line.\"\r\n<\/p>\r\n<h3>Controlling Factors<\/h3>\r\n<p>\r\n\tThe treeline is controlled by <a href=\"\/article\/climate\/\">climate<\/a> in interaction with <a href=\"\/article\/soil\/\">soil<\/a>. In the North, it is correlated generally with the modal (most common) position of the southern edge of the arctic front in summer, and with such temperature indices as the July 10\u00b0C isotherm. But wherever soils are deeper and warmer than normal, as in river valleys (eg, the <a href=\"\/article\/thelon-river\/\">Thelon<\/a>) or on upland, sandy <a href=\"\/article\/esker\/\">eskers<\/a>, ribbons of trees extend the treeline far into the tundra.\r\n<\/p>\r\n<p>\r\n\t<strong>Trees of the Treeline<\/strong><br>\r\n\tCharacteristic treeline species are alpine fir, whitebark pine and alpine larch in the Rocky Mountains; in Alaska and northern Canada, co-existing black spruce, white spruce and larch. Similar species of spruce and larch, with pine and birch, continue the circumpolar treeline across Eurasia.\r\n<\/p>\r\n<p>\r\n\t<strong>Non-static Limit<\/strong><br>\r\n\tThe pollen record (<em>see <\/em><a href=\"\/article\/palynology\/\">palynology<\/a>) and preserved wood show that treelines on this continent have fluctuated greatly in the past, advancing hundreds of kilometres during warm phases and retreating southward when the climate has deteriorated. Three major movements have been identified; the first during the Tertiary (65 to 1.65 million years ago), reaching Ellesmere Island; later in the Pleistocene (1.65 million to 10 000 years ago), reaching northernmost Greenland and Meighen and Banks islands; and most recently in the early Holocene (some 10 000 years ago), reaching the Mackenzie Valley and Tuktoyaktuk, NWT. Such movements take hundreds of years.\r\n<\/p>\r\n<p>\r\n\tClimatic changes can cause abrupt shifts in the treeline, because seed production and survival of seedlings are precarious near the limit of trees. The conifers are also susceptible to fire during dry periods, and this and cutting by humans make today's treeline a diffuse and unstable boundary. The dotted lines and the label \"Approximate Limit of Trees\" that indicate the treeline on northern National Topographic Survey maps are appropriately vague, partly because of a lack of field surveys.\r\n<\/p>","twitter_summary":null,"translations":[{"id":"c8c4b6d8-56db-45e0-bce2-953b52422389","article_id":"77320","title":"Treeline","summary":"The treeline is controlled by CLIMATE in interaction with SOIL. In the North, it is correlated generally with the modal (most common) position of the southern edge of the arctic front in summer, and with such temperature indices as the July 10\u00b0C isotherm.","body":"<div><img src=\"https:\/\/d3d0lqu00lnqvz.cloudfront.net\/media\/media\/thumbnails\/e2366ba0-9f18-4eec-968d-6f1076b512b0.jpg\" title='Snow-covered Evergreen' alt='Snow-covered Evergreen' \/><figcaption>Most conifers are evergreens, retaining their needlelike leaves for several years (Corel Professional Photos).<\/figcaption><\/div>\r\n<h3>Treeline<\/h3>\r\n<p>\r\n\t<a href=\"javascript:DisplayMedia('1995', '1995', '1995', 400, 268, 0, 0, 0);\" name=\"1995\"><\/a> The treeline marks the limit of <a href=\"\/article\/trees\/\">trees<\/a> latitudinally on continental plains and altitudinally on highlands and mountains (where it is sometimes called the timberline). Tree species still occur beyond this limit, but in shrub form, extending to the \"tree-species line.\"\r\n<\/p>\r\n<h3>Controlling Factors<\/h3>\r\n<p>\r\n\tThe treeline is controlled by <a href=\"\/article\/climate\/\">climate<\/a> in interaction with <a href=\"\/article\/soil\/\">soil<\/a>. In the North, it is correlated generally with the modal (most common) position of the southern edge of the arctic front in summer, and with such temperature indices as the July 10\u00b0C isotherm. But wherever soils are deeper and warmer than normal, as in river valleys (eg, the <a href=\"\/article\/thelon-river\/\">Thelon<\/a>) or on upland, sandy <a href=\"\/article\/esker\/\">eskers<\/a>, ribbons of trees extend the treeline far into the tundra.\r\n<\/p>\r\n<p>\r\n\t<strong>Trees of the Treeline<\/strong><br>\r\n\tCharacteristic treeline species are alpine fir, whitebark pine and alpine larch in the Rocky Mountains; in Alaska and northern Canada, co-existing black spruce, white spruce and larch. Similar species of spruce and larch, with pine and birch, continue the circumpolar treeline across Eurasia.\r\n<\/p>\r\n<p>\r\n\t<strong>Non-static Limit<\/strong><br>\r\n\tThe pollen record (<em>see <\/em><a href=\"\/article\/palynology\/\">palynology<\/a>) and preserved wood show that treelines on this continent have fluctuated greatly in the past, advancing hundreds of kilometres during warm phases and retreating southward when the climate has deteriorated. Three major movements have been identified; the first during the Tertiary (65 to 1.65 million years ago), reaching Ellesmere Island; later in the Pleistocene (1.65 million to 10 000 years ago), reaching northernmost Greenland and Meighen and Banks islands; and most recently in the early Holocene (some 10 000 years ago), reaching the Mackenzie Valley and Tuktoyaktuk, NWT. Such movements take hundreds of years.\r\n<\/p>\r\n<p>\r\n\tClimatic changes can cause abrupt shifts in the treeline, because seed production and survival of seedlings are precarious near the limit of trees. The conifers are also susceptible to fire during dry periods, and this and cutting by humans make today's treeline a diffuse and unstable boundary. The dotted lines and the label \"Approximate Limit of Trees\" that indicate the treeline on northern National Topographic Survey maps are appropriately vague, partly because of a lack of field surveys.\r\n<\/p>","slug":"treeline","alt_slug":null,"twitter_summary":null,"locale":"en","automated":false,"hidden":0,"views":0,"created_at":"2007-01-30T00:00:00.000000Z","updated_at":"2015-06-19T19:55:46.000000Z"},{"id":"a4c7513f-066d-4a60-bfff-fce7881f8b78","article_id":"77320","title":"Limite foresti\u00e8re","summary":"La limite des arbres est fonction du CLIMAT du SOL. Dans le Nord, elle correspond habituellement \u00e0 la position modale (la plus courante) de la limite Sud du front arctique en \u00e9t\u00e9, et \u00e0 la ligne isotherme moyenne de 10\u00a0\u00b0C en juillet.","body":"<div><img src=\"https:\/\/d3d0lqu00lnqvz.cloudfront.net\/media\/media\/thumbnails\/e2366ba0-9f18-4eec-968d-6f1076b512b0.jpg\" title='Conif\\u00e8res sous la neige' alt='Conif\\u00e8res sous la neige' \/><figcaption>Les feuilles des conif\\u00e8res sont adapt\u00e9es pour \u00e9viter la perte d'eau (Corel Professional Photos).<\/figcaption><\/div>\r\n<h3>Limite foresti\u00e8re<\/h3>\r\n<p>\r\n\t<a href=\"javascript:DisplayMedia('1995', '1995', '1995', 400, 268, 0, 0, 0);\" name=\"1995\"><\/a> La limite foresti\u00e8re (<em>voir <\/em><a href=\"\/article\/trees\/\">ARBRES<\/a>) atteint les plaines continentales en latitude, les hautes terres et les montagnes en altitude. Certaines essences poussent au-del\u00e0 de cette limite, mais sous forme d'arbustes, jusqu'\u00e0 la \u00ab limite des essences foresti\u00e8res \u00bb.\r\n<\/p>\r\n<h3>Facteurs d'influence<\/h3>\r\n<p>\r\n\tLa limite des arbres est fonction du <a href=\"\/article\/climate\/\">CLIMAT<\/a> du <a href=\"\/article\/soil\/\">SOL<\/a>. Dans le Nord, elle correspond habituellement \u00e0 la position modale (la plus courante) de la limite Sud du front arctique en \u00e9t\u00e9, et \u00e0 la ligne isotherme moyenne de 10 \u00b0C en juillet. Cependant, dans les endroits o\u00f9 le sol est plus profond et la temp\u00e9rature plus chaude que la normale, comme dans les vall\u00e9es fluviales (celle de la <a href=\"\/article\/thelon-river\/\">RIVI\u00c8RE THELON<\/a>, entre autres) ou sur les <a href=\"\/article\/esker\/\">ESKERS<\/a> sablonneux des hautes terres, des rubans d'arbres p\u00e9n\u00e8trent profond\u00e9ment dans la toundra.\r\n<\/p>\r\n<p>\r\n\t<strong>Essences de la limite des arbres<\/strong><br>\r\n\tLes essences de la limite des arbres sont le sapin subalpin, le pin albicaule (ou \u00e0 \u00e9corce blanche) et le m\u00e9l\u00e8ze subalpin dans les montagnes rocheuses; l'\u00e9pinette noire, l'\u00e9pinette blanche et le m\u00e9l\u00e8ze, en Alaska et dans le Nord du Canada. Des esp\u00e8ces apparent\u00e9es d'\u00e9pinette et de m\u00e9l\u00e8ze m\u00eal\u00e9es au bouleau et au pin blanc prolongent la limite des arbres dans toute l'Eurasie.\r\n<\/p>\r\n<p>\r\n\t<strong>Limite instable<\/strong><br>\r\n\tLes donn\u00e9es sur le pollen (<em>voir <\/em><a href=\"\/article\/palynology\/\">PALYNOLOGIE<\/a>) et le bois fossile r\u00e9v\u00e8lent que la limite des arbres de ce continent a beaucoup vari\u00e9 dans le pass\u00e9, avan\u00e7ant sur centaines de kilom\u00e8tres durant les p\u00e9riodes de r\u00e9chauffement et reculant vers le sud au cours des p\u00e9riodes de refroidissement. On conna\u00eet trois mouvements importants. Le premier a eu lieu durant l'\u00e8re tertiaire (il y a entre 65 et 1,65 million d'ann\u00e9es) et a atteint l'\u00eele Ellesmere; plus tard, au cours de l'\u00e8re pl\u00e9istoc\u00e8ne (il y a entre 1,65 million \u00e0 10 000 ans), il a atteint la partie la plus septentrionale du Groenland, de m\u00eame que l'\u00eele Meighen et l'\u00eele Banks; plus r\u00e9cemment, pendant l'\u00e8re holoc\u00e8ne (il y a environ 10 000 ans), il a atteint la vall\u00e9e du Mackenzie et Tuktoyaktuk (T.N-O.). Ces mouvements durent plusieurs centaines d'ann\u00e9es.\r\n<\/p>\r\n<p>\r\n\tLes changements climatiques peuvent provoquer des d\u00e9placements brusques de la limite des arbres, parce que la production de graines et la survie des jeunes plants y sont pr\u00e9caires. Le risque d'incendie, particuli\u00e8rement grand dans les for\u00eats de conif\u00e8res durant les p\u00e9riodes s\u00e8ches, ajout\u00e9 aux coupes faites par l'homme, font qu'aujourd'hui la limite des arbres est diffuse et instable. Les lignes pointill\u00e9es et la l\u00e9gende \u00ab Limite approximative des arbres \u00bb que l'on voit sur les cartes nationales de lev\u00e9s topographiques sont d\u00e9lib\u00e9r\u00e9ment impr\u00e9cises, en partie faute d'\u00e9tudes suffisantes sur le terrain.\r\n<\/p>","slug":"limite-forestiere","alt_slug":null,"twitter_summary":null,"locale":"fr","automated":false,"hidden":0,"views":0,"created_at":"2007-01-30T00:00:00.000000Z","updated_at":"2015-06-19T19:55:46.000000Z"}],"widgets":[{"id":"582","user_id":"450","status":"published","schedule_from":null,"schedule_until":null,"created_at":"2014-05-13T14:25:58.000000Z","updated_at":"2018-01-25T19:21:43.000000Z","title":"Interested in plants?","body":"<p>\r\n\t<a href=\"http:\/\/www.thecanadianencyclopedia.ca\/en\/collection\/botany\/\"><img src=\"https:\/\/d3d0lqu00lnqvz.cloudfront.net\/media\/widgets_collections\/Botany%20Collection%20EN.jpg\" style=\"opacity: 1;\" alt=\"\"><\/a>\r\n<\/p>","pivot":{"article_id":"77320","widget_id":"582","position":0},"translations":[{"id":"49232cb2-1acd-416d-a2e6-7e0834e0c023","widget_id":"582","title":"Interested in plants?","body":"<p>\r\n\t<a href=\"http:\/\/www.thecanadianencyclopedia.ca\/en\/collection\/botany\/\"><img src=\"https:\/\/d3d0lqu00lnqvz.cloudfront.net\/media\/widgets_collections\/Botany%20Collection%20EN.jpg\" style=\"opacity: 1;\" alt=\"\"><\/a>\r\n<\/p>","locale":"en"},{"id":"7bb6f336-e8ee-4059-8244-da8f9bdfb5a2","widget_id":"582","title":"En savoir plus","body":"<p>\r\n\t<a href=\"http:\/\/www.thecanadianencyclopedia.ca\/fr\/collection\/botany\/\"><img src=\"https:\/\/d3d0lqu00lnqvz.cloudfront.net\/media\/widgets_collections\/Botany%20Collection%20FR.jpg\" style=\"opacity: 1;\" alt=\"\"><\/a>\r\n<\/p>","locale":"fr"}]}],"links":[],"recommended_readings":[],"tags":[],"sponsors":[],"translation":{"id":"c8c4b6d8-56db-45e0-bce2-953b52422389","article_id":"77320","title":"Treeline","summary":"The treeline is controlled by CLIMATE in interaction with SOIL. In the North, it is correlated generally with the modal (most common) position of the southern edge of the arctic front in summer, and with such temperature indices as the July 10\u00b0C isotherm.","body":"<div><img src=\"https:\/\/d3d0lqu00lnqvz.cloudfront.net\/media\/media\/thumbnails\/e2366ba0-9f18-4eec-968d-6f1076b512b0.jpg\" title='Snow-covered Evergreen' alt='Snow-covered Evergreen' \/><figcaption>Most conifers are evergreens, retaining their needlelike leaves for several years (Corel Professional Photos).<\/figcaption><\/div>\r\n<h3>Treeline<\/h3>\r\n<p>\r\n\t<a href=\"javascript:DisplayMedia('1995', '1995', '1995', 400, 268, 0, 0, 0);\" name=\"1995\"><\/a> The treeline marks the limit of <a href=\"\/article\/trees\/\">trees<\/a> latitudinally on continental plains and altitudinally on highlands and mountains (where it is sometimes called the timberline). Tree species still occur beyond this limit, but in shrub form, extending to the \"tree-species line.\"\r\n<\/p>\r\n<h3>Controlling Factors<\/h3>\r\n<p>\r\n\tThe treeline is controlled by <a href=\"\/article\/climate\/\">climate<\/a> in interaction with <a href=\"\/article\/soil\/\">soil<\/a>. In the North, it is correlated generally with the modal (most common) position of the southern edge of the arctic front in summer, and with such temperature indices as the July 10\u00b0C isotherm. But wherever soils are deeper and warmer than normal, as in river valleys (eg, the <a href=\"\/article\/thelon-river\/\">Thelon<\/a>) or on upland, sandy <a href=\"\/article\/esker\/\">eskers<\/a>, ribbons of trees extend the treeline far into the tundra.\r\n<\/p>\r\n<p>\r\n\t<strong>Trees of the Treeline<\/strong><br>\r\n\tCharacteristic treeline species are alpine fir, whitebark pine and alpine larch in the Rocky Mountains; in Alaska and northern Canada, co-existing black spruce, white spruce and larch. Similar species of spruce and larch, with pine and birch, continue the circumpolar treeline across Eurasia.\r\n<\/p>\r\n<p>\r\n\t<strong>Non-static Limit<\/strong><br>\r\n\tThe pollen record (<em>see <\/em><a href=\"\/article\/palynology\/\">palynology<\/a>) and preserved wood show that treelines on this continent have fluctuated greatly in the past, advancing hundreds of kilometres during warm phases and retreating southward when the climate has deteriorated. Three major movements have been identified; the first during the Tertiary (65 to 1.65 million years ago), reaching Ellesmere Island; later in the Pleistocene (1.65 million to 10 000 years ago), reaching northernmost Greenland and Meighen and Banks islands; and most recently in the early Holocene (some 10 000 years ago), reaching the Mackenzie Valley and Tuktoyaktuk, NWT. Such movements take hundreds of years.\r\n<\/p>\r\n<p>\r\n\tClimatic changes can cause abrupt shifts in the treeline, because seed production and survival of seedlings are precarious near the limit of trees. The conifers are also susceptible to fire during dry periods, and this and cutting by humans make today's treeline a diffuse and unstable boundary. The dotted lines and the label \"Approximate Limit of Trees\" that indicate the treeline on northern National Topographic Survey maps are appropriately vague, partly because of a lack of field surveys.\r\n<\/p>","slug":"treeline","alt_slug":null,"twitter_summary":null,"locale":"en","automated":false,"hidden":0,"views":0,"created_at":"2007-01-30T00:00:00.000000Z","updated_at":"2015-06-19T19:55:46.000000Z"},"media":[],"related_collections":[]},"related_articles":[{"id":"80643","author_text":"K.r. Rozee","revisor":"","major_update":null,"trigger_warning":0,"views":0,"shares":0,"type":"article","itunes_songs":"","indigo":"","itunes_title_en":"","itunes_title_fr":"","indigo_title_en":"","indigo_title_fr":"","status":"published","schedule_from":null,"schedule_until":null,"created_at":"2006-02-08T00:00:00.000000Z","updated_at":"2019-10-16T20:34:44.000000Z","deleted_at":null,"title":"Virus","slug":"virus","alt_slug":"","summary":"Virus, the smallest form of life (20-300 nanometres), is structurally and functionally unique. Their size is such that they do not contain enough genetic material to code for the proteins they require for reproduction, nor do they have ribosomes needed to synthesize these proteins.","body":"<h3>Virus<\/h3>\r\n<p>\r\n\tVirus, the smallest form of life (20-300 nanometres), is structurally and functionally unique.\r\n\t<update>Their size is such that they do not contain enough genetic material to code for the proteins they require for reproduction, nor do they have ribosomes needed to synthesize these proteins.<\/update> Therefore, being obliged to enter permissive host cells\r\n\tthat assist them to reproduce, they are obligate intracellular parasites implicated in <a href=\"\/article\/disease\/\">diseases<\/a> of humans, other animals and plants.\r\n<\/p>\r\n<p>\r\n\t<update>Specialists in microbiology, <a href=\"\/article\/molecular-biology\/\">molecular biology<\/a>, <a href=\"\/article\/biochemistry\/\">biochemistry<\/a>, <a href=\"\/article\/immunology\/\">immunology<\/a> and other biological sciences are engaged in interdisciplinary\r\n\t\tresearch to identify, describe and control disease-causing viruses. In Canada, research into human viral disease is carried out primarily in the universities and hospitals, and is funded largely by federal and provincial grants and frequently by targeted\r\n\t\tphilanthropic agencies. Agriculture Canada and certain universities have extensive programs on viral diseases of animals. Work on plant viruses is done in Agriculture Canada <a href=\"\/article\/agricultural-research-stations\/\">Research Stations<\/a> and\r\n\t\tin plant pathology laboratories connected to university departments of botany or biology.<\/update>\r\n<\/p>\r\n<h3>Structure and Function<\/h3>\r\n<p>\r\n\tThe mature virus organism (virion) consists of viral genes contained in a protective protein shell (a capsid). Viral genes may be deoxyribonucleic acid (DNA) or ribonucleic acid (RNA); genetic RNA is unique to viruses. RNA viruses include enteroviruses\r\n\t(eg, causing poliomyelitis), rhinoviruses (common cold), rhabdoviruses (rabies), paramyxoviruses (measles), orthomyxoviruses (influenza) and almost all plant viruses.\r\n<\/p>\r\n<p>\r\n\tDNA viruses include papavoviruses (warts), adenoviruses (acute respiratory disease), herpesviruses (cold sore, infectious mononucleosis, chicken pox), poxviruses (smallpox, cowpox), hepatitis B, and many viruses that infect bacteria (bacteriophages) and\r\n\tinsects.\r\n\t<update>Virions have very limited functions and serve mainly to protect the viral genetic material (genome) from adverse environmental factors outside a host cell and to facilitate the entry of the genome into compatible host cells.<\/update> Specific types of\r\n\tviruses take advantage of the resources of particular host cells. Bacteriophages (bacteria eaters), named by Canadian virologist Felix d'Herelle in 1917, prey only on bacteria and have specific preferences for particular bacterial species.\r\n<\/p><iframe width=\"580\" height=\"315\" src=\"https:\/\/www.youtube.com\/embed\/LJjUu_NAreo?rel=0\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen=\"\"><\/iframe><br>\r\n<p>\r\n\tSimilarly, plant-specific viruses (discovered by Russian botanist Dimitri Ivanovsky in 1892) and animal-specific viruses (discovered by Friedrich Loeffler and Paul Frosch in 1898) have preferred host cells. Such preferences may stem from the origins of\r\n\tviruses, which are thought by some theorists to be degenerate, subcellular, self-replicating particles.\r\n<\/p>\r\n<p>\r\n\tViruses infect cells by fusion, endocytosis or injection. In viruses of a certain structure, the viral envelope fuses with the cell membrane of a host cell and the virus genome it contains is introduced into the cell. In endocytosis the host cell engulfs\r\n\tthe virus, engulfment being triggered by contact with a viral particle, and the nucleic material is released from the capsid.\r\n\t<update>Injection, a technique copied in laboratory <a href=\"\/article\/genetic-engineering\/\">genetic engineering<\/a>, is used only when bacteriophages infect bacteria. The bacteriophages (virus) attaches itself to the bacterial cell wall and injects its nucleic\r\n\t\tacid, leaving the capsid outside the wall. Once inside the host cell, the viral nucleic acid participates in replicative activity. <\/update>\r\n<\/p>\r\n<p>\r\n\t<update>Once inside a permissive host cell the viral DNA or RNA may integrate itself into the genome of the host cell or may immediately initiate replication through a cytolytic (eg, cell-degenerating) infection, depending on the type of virus. In the case of\r\n\t\tintegration, the host cell undergoes changes during which it acquires many of the properties of <a href=\"\/article\/cancer\/\">cancer<\/a> cells. <\/update>\r\n<\/p>\r\n<p>\r\n\t<update>The virus genome, being integrated, is conserved and replicated along with the host genome. The virus or cell may, however, initiate a \"lytic\" infection replicating the mature virion which is then capable of infecting another host cell. The association\r\n\t\tbetween viruses and some cancers in humans is well documented, and viruses are known to cause many cancers in other <a href=\"\/article\/vertebrate\/\">vertebrate<\/a> species. <\/update>\r\n<\/p>\r\n<p>\r\n\tCells undergoing a lytic virus infection frequently have their own synthetic processes inhibited but produce hundreds of identical copies of the infecting virion. The replicative strategies employed by RNA viruses are diverse and complex, depending upon\r\n\twhether the virus genome can function directly as messenger RNA, which instructs host cell ribosomes (cell organelles through which protein synthesis occurs) to make viral enzymes and proteins, or whether messenger RNA must be synthesized on the viral\r\n\tgenetic template, before protein and enzyme synthesis can proceed.\r\n<\/p>\r\n<p>\r\n\t<update>Most DNA viruses replicate in the nucleus of the host cell, using host-cell enzymes to synthesize messenger RNA on the virus's DNA template. Assembly of the virus is a complex and still poorly understood process. As examples, RNA viruses may assume a\r\n\t\tsimple spherical form, complicated forms with enveloping membranes, and other special structures.<\/update> DNA viruses may assemble in \"factories\" in the host-cell cytoplasm or be \"budded off\" from the host-cell membranes. Viruses that acquire outer\r\n\tmembranes from the membrane of the cell's nucleus or cytoplasm incorporate virus-coded glycoproteins into these membranes, before the final assembly of the mature virion.\r\n<\/p>\r\n<p>\r\n\tViruses cause major diseases in plants and animals, but there are few effective methods for cure. Plant breeding may yield strains resistant to viruses, but this avenue of approach is unavailable to humans.\r\n\t<update>Recently, some antiviral chemicals have shown promise as antibiotics; however, this control technique is still limited to a few virus diseases such as the use of acyclovir for herpesvirus infections.<\/update>\r\n<\/p>\r\n<p>\r\n\tMore successful efforts have been directed towards the development of vaccines for preventing viral disease. Properly administered, such vaccines have resulted in the worldwide eradication of smallpox and the virtual disappearance of poliomyelitis, measles\r\n\tand rubella from specific populations.\r\n\t<update>In all Canadian provinces, <a href=\"\/article\/public-health\/\">Public Health<\/a> authorities maintain vaccination programs directed especially at small children. Some viruses, notably Human Immunodeficiency Virus (HIV), the cause of Acquired Immune Deficiency\r\n\t\tSyndrome or AIDS, have been, to date, refractory to either approach and innovative therapeutic methods are actively being pursued.<\/update>\r\n<\/p>\r\n<p>\r\n\t<update>Finally virologists today are deeply concerned about the appearance of new and the resurgence of known pathogenic viruses such as HIV and the ability of the <a href=\"\/article\/public-health\/\">Public Health<\/a> system to treat and control these organisms.<\/update><em> See also<\/em>\t<a href=\"\/article\/biological-product\/\">Biological Products Industry<\/a>; <a href=\"\/article\/pharmacy\/\">Pharmacy<\/a>; <a href=\"\/article\/veterinary-medicine\/\">Veterinary Medicine<\/a>.\r\n<\/p>","twitter_summary":null,"pivot":{"model_id":"77320","relatable_id":"80643","relatable_type":"App\\Models\\Article","position":0},"translations":[{"id":"517960bb-1ad6-4ad5-a13c-e6574342fe60","article_id":"80643","title":"Virus","summary":"Virus, the smallest form of life (20-300 nanometres), is structurally and functionally unique. Their size is such that they do not contain enough genetic material to code for the proteins they require for reproduction, nor do they have ribosomes needed to synthesize these proteins.","body":"<h3>Virus<\/h3>\r\n<p>\r\n\tVirus, the smallest form of life (20-300 nanometres), is structurally and functionally unique.\r\n\t<update>Their size is such that they do not contain enough genetic material to code for the proteins they require for reproduction, nor do they have ribosomes needed to synthesize these proteins.<\/update> Therefore, being obliged to enter permissive host cells\r\n\tthat assist them to reproduce, they are obligate intracellular parasites implicated in <a href=\"\/article\/disease\/\">diseases<\/a> of humans, other animals and plants.\r\n<\/p>\r\n<p>\r\n\t<update>Specialists in microbiology, <a href=\"\/article\/molecular-biology\/\">molecular biology<\/a>, <a href=\"\/article\/biochemistry\/\">biochemistry<\/a>, <a href=\"\/article\/immunology\/\">immunology<\/a> and other biological sciences are engaged in interdisciplinary\r\n\t\tresearch to identify, describe and control disease-causing viruses. In Canada, research into human viral disease is carried out primarily in the universities and hospitals, and is funded largely by federal and provincial grants and frequently by targeted\r\n\t\tphilanthropic agencies. Agriculture Canada and certain universities have extensive programs on viral diseases of animals. Work on plant viruses is done in Agriculture Canada <a href=\"\/article\/agricultural-research-stations\/\">Research Stations<\/a> and\r\n\t\tin plant pathology laboratories connected to university departments of botany or biology.<\/update>\r\n<\/p>\r\n<h3>Structure and Function<\/h3>\r\n<p>\r\n\tThe mature virus organism (virion) consists of viral genes contained in a protective protein shell (a capsid). Viral genes may be deoxyribonucleic acid (DNA) or ribonucleic acid (RNA); genetic RNA is unique to viruses. RNA viruses include enteroviruses\r\n\t(eg, causing poliomyelitis), rhinoviruses (common cold), rhabdoviruses (rabies), paramyxoviruses (measles), orthomyxoviruses (influenza) and almost all plant viruses.\r\n<\/p>\r\n<p>\r\n\tDNA viruses include papavoviruses (warts), adenoviruses (acute respiratory disease), herpesviruses (cold sore, infectious mononucleosis, chicken pox), poxviruses (smallpox, cowpox), hepatitis B, and many viruses that infect bacteria (bacteriophages) and\r\n\tinsects.\r\n\t<update>Virions have very limited functions and serve mainly to protect the viral genetic material (genome) from adverse environmental factors outside a host cell and to facilitate the entry of the genome into compatible host cells.<\/update> Specific types of\r\n\tviruses take advantage of the resources of particular host cells. Bacteriophages (bacteria eaters), named by Canadian virologist Felix d'Herelle in 1917, prey only on bacteria and have specific preferences for particular bacterial species.\r\n<\/p><iframe width=\"580\" height=\"315\" src=\"https:\/\/www.youtube.com\/embed\/LJjUu_NAreo?rel=0\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen=\"\"><\/iframe><br>\r\n<p>\r\n\tSimilarly, plant-specific viruses (discovered by Russian botanist Dimitri Ivanovsky in 1892) and animal-specific viruses (discovered by Friedrich Loeffler and Paul Frosch in 1898) have preferred host cells. Such preferences may stem from the origins of\r\n\tviruses, which are thought by some theorists to be degenerate, subcellular, self-replicating particles.\r\n<\/p>\r\n<p>\r\n\tViruses infect cells by fusion, endocytosis or injection. In viruses of a certain structure, the viral envelope fuses with the cell membrane of a host cell and the virus genome it contains is introduced into the cell. In endocytosis the host cell engulfs\r\n\tthe virus, engulfment being triggered by contact with a viral particle, and the nucleic material is released from the capsid.\r\n\t<update>Injection, a technique copied in laboratory <a href=\"\/article\/genetic-engineering\/\">genetic engineering<\/a>, is used only when bacteriophages infect bacteria. The bacteriophages (virus) attaches itself to the bacterial cell wall and injects its nucleic\r\n\t\tacid, leaving the capsid outside the wall. Once inside the host cell, the viral nucleic acid participates in replicative activity. <\/update>\r\n<\/p>\r\n<p>\r\n\t<update>Once inside a permissive host cell the viral DNA or RNA may integrate itself into the genome of the host cell or may immediately initiate replication through a cytolytic (eg, cell-degenerating) infection, depending on the type of virus. In the case of\r\n\t\tintegration, the host cell undergoes changes during which it acquires many of the properties of <a href=\"\/article\/cancer\/\">cancer<\/a> cells. <\/update>\r\n<\/p>\r\n<p>\r\n\t<update>The virus genome, being integrated, is conserved and replicated along with the host genome. The virus or cell may, however, initiate a \"lytic\" infection replicating the mature virion which is then capable of infecting another host cell. The association\r\n\t\tbetween viruses and some cancers in humans is well documented, and viruses are known to cause many cancers in other <a href=\"\/article\/vertebrate\/\">vertebrate<\/a> species. <\/update>\r\n<\/p>\r\n<p>\r\n\tCells undergoing a lytic virus infection frequently have their own synthetic processes inhibited but produce hundreds of identical copies of the infecting virion. The replicative strategies employed by RNA viruses are diverse and complex, depending upon\r\n\twhether the virus genome can function directly as messenger RNA, which instructs host cell ribosomes (cell organelles through which protein synthesis occurs) to make viral enzymes and proteins, or whether messenger RNA must be synthesized on the viral\r\n\tgenetic template, before protein and enzyme synthesis can proceed.\r\n<\/p>\r\n<p>\r\n\t<update>Most DNA viruses replicate in the nucleus of the host cell, using host-cell enzymes to synthesize messenger RNA on the virus's DNA template. Assembly of the virus is a complex and still poorly understood process. As examples, RNA viruses may assume a\r\n\t\tsimple spherical form, complicated forms with enveloping membranes, and other special structures.<\/update> DNA viruses may assemble in \"factories\" in the host-cell cytoplasm or be \"budded off\" from the host-cell membranes. Viruses that acquire outer\r\n\tmembranes from the membrane of the cell's nucleus or cytoplasm incorporate virus-coded glycoproteins into these membranes, before the final assembly of the mature virion.\r\n<\/p>\r\n<p>\r\n\tViruses cause major diseases in plants and animals, but there are few effective methods for cure. Plant breeding may yield strains resistant to viruses, but this avenue of approach is unavailable to humans.\r\n\t<update>Recently, some antiviral chemicals have shown promise as antibiotics; however, this control technique is still limited to a few virus diseases such as the use of acyclovir for herpesvirus infections.<\/update>\r\n<\/p>\r\n<p>\r\n\tMore successful efforts have been directed towards the development of vaccines for preventing viral disease. Properly administered, such vaccines have resulted in the worldwide eradication of smallpox and the virtual disappearance of poliomyelitis, measles\r\n\tand rubella from specific populations.\r\n\t<update>In all Canadian provinces, <a href=\"\/article\/public-health\/\">Public Health<\/a> authorities maintain vaccination programs directed especially at small children. Some viruses, notably Human Immunodeficiency Virus (HIV), the cause of Acquired Immune Deficiency\r\n\t\tSyndrome or AIDS, have been, to date, refractory to either approach and innovative therapeutic methods are actively being pursued.<\/update>\r\n<\/p>\r\n<p>\r\n\t<update>Finally virologists today are deeply concerned about the appearance of new and the resurgence of known pathogenic viruses such as HIV and the ability of the <a href=\"\/article\/public-health\/\">Public Health<\/a> system to treat and control these organisms.<\/update><em> See also<\/em>\t<a href=\"\/article\/biological-product\/\">Biological Products Industry<\/a>; <a href=\"\/article\/pharmacy\/\">Pharmacy<\/a>; <a href=\"\/article\/veterinary-medicine\/\">Veterinary Medicine<\/a>.\r\n<\/p>","slug":"virus","alt_slug":"","twitter_summary":null,"locale":"en","automated":false,"hidden":0,"views":0,"created_at":"2006-02-08T00:00:00.000000Z","updated_at":"2019-10-16T20:34:44.000000Z"},{"id":"c34f5172-d61b-4ae4-9bf1-a13d3e6caaed","article_id":"80643","title":"Virus","summary":"Les virus, plus petites formes de vie (de 20 \u00e0 300 nanom\u00e8tres), forment un groupe unique, tant par leur mode de reproduction que par leur structure. Le virus est si petit qu'il ne contient pas tout le mat\u00e9riel g\u00e9n\u00e9tique n\u00e9cessaire \u00e0 la synth\u00e8se des prot\u00e9ines requises pour sa reproduction.","body":"<h3>Virus<\/h3>\r\n<p>\r\n\tLes virus, plus petites formes de vie (de 20 \u00e0 300 nanom\u00e8tres), forment un groupe unique, tant par leur mode de reproduction que par leur structure. Le virus est si petit qu'il ne contient pas tout le mat\u00e9riel g\u00e9n\u00e9tique n\u00e9cessaire \u00e0 la synth\u00e8se des prot\u00e9ines\r\n\trequises pour sa reproduction. Il est \u00e9galement d\u00e9pourvu des ribosomes n\u00e9cessaires \u00e0 la synth\u00e8se de ses prot\u00e9ines. Il est donc oblig\u00e9 de p\u00e9n\u00e9trer dans des cellules h\u00f4tes, qui l'aident \u00e0 se reproduire. C'est un parasite intracellulaire qui provoque in\u00e9vitablement\r\n\tdes <a href=\"\/article\/disease\/\">MALADIES<\/a> chez l'homme, les animaux et les plantes.\r\n<\/p>\r\n<p>\r\n\t<update>Des sp\u00e9cialistes en microbiologie, en <a href=\"\/article\/molecular-biology\/\">BIOLOGIE MOL\u00c9CULAIRE<\/a>, en <a href=\"\/article\/biochemistry\/\">BIOCHIMIE<\/a>, en <a href=\"\/article\/immunology\/\">IMMUNOLOGIE<\/a> et en d'autres sciences biologiques participent\r\n\t\t\u00e0 des recherches interdisciplinaires afin d'identifier, de d\u00e9crire et de limiter l'action des virus responsables des maladies. Au Canada, la recherche sur les maladies virales chez l'homme s'effectue principalement dans les universit\u00e9s et les h\u00f4pitaux.\r\n\t\tElle est financ\u00e9e en grande partie par des subventions f\u00e9d\u00e9rales ou provinciales et, bien souvent, aid\u00e9e par des organismes philanthropiques. Le minist\u00e8re de l'Agriculture et de l'Agroalimentaire du Canada ainsi que certaines universit\u00e9s poss\u00e8dent des\r\n\t\tprogrammes complets traitant des maladies virales chez les animaux. Les recherches sur les virus s'attaquant aux plantes sont effectu\u00e9es dans les <a href=\"\/article\/agricultural-research-stations\/\">STATIONS DE RECHERCHE EN AGRICULTURE<\/a> et dans les\r\n\t\tlaboratoires de pathologie v\u00e9g\u00e9tale rattach\u00e9s \u00e0 des d\u00e9partements universitaires de botanique ou de biologie.<\/update>\r\n<\/p>\r\n<h3>Structure et fonction<\/h3>\r\n<p>\r\n\tLa particule virale compl\u00e8te (virion) se compose de g\u00e8nes viraux entour\u00e9s d'une enveloppe protectrice faite de prot\u00e9ines appel\u00e9e capside. Les g\u00e8nes viraux sont constitu\u00e9s d'acide d\u00e9soxyribonucl\u00e9ique (ADN) ou d'acide ribonucl\u00e9ique (ARN). Seuls les virus\r\n\tposs\u00e8dent du mat\u00e9riel g\u00e9n\u00e9tique sous forme d'ARN. Les virus \u00e0 ARN comprennent les ent\u00e9rovirus (comme celui causant la poliomy\u00e9lite), les rhinovirus (rhume banal), les rhabdovirus (rage), les paramyxovirus (rougeole), les orthomyxovirus (grippe) ainsi\r\n\tque presque tous les virus affectant les plantes.\r\n<\/p>\r\n<p>\r\n\tLes virus \u00e0 ADN comprennent les papavovirus (verrues), les ad\u00e9novirus (atteinte respiratoire aigu\u00eb), les virus herp\u00e9tiques (boutons de fi\u00e8vre, mononucl\u00e9ose infectieuse, varicelle), les orthopoxvirus (variole, vaccine), le virus de l'h\u00e9patite B, ainsi\r\n\tque de nombreux autres virus qui infectent les bact\u00e9ries (bact\u00e9riophages) et les insectes. La capside joue un r\u00f4le mineur. Elle sert essentiellement \u00e0 prot\u00e9ger le mat\u00e9riel g\u00e9n\u00e9tique (g\u00e9nome) contre des facteurs adverses hors de la cellule h\u00f4te et \u00e0 en\r\n\tfaciliter l'entr\u00e9e dans la cellule h\u00f4te. Chaque type de virus est sp\u00e9cifique \u00e0 un type de cellule h\u00f4te particuli\u00e8re. C'est le virologiste canadien Felix d'Herelle qui a donn\u00e9 leur nom aux bact\u00e9riophages en 1917. Ceux-ci d\u00e9truisent les bact\u00e9ries et s'attaquent\r\n\tuniquement \u00e0 elles. Chaque type de bact\u00e9riophage est caract\u00e9ris\u00e9 par les esp\u00e8ces sp\u00e9cifiques de bact\u00e9ries qu'il peut attaquer.\r\n<\/p><iframe width=\"580\" height=\"315\" src=\"https:\/\/www.youtube.com\/embed\/vJFflwwk0s4?rel=0\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen=\"\"><\/iframe>\r\n<br>\r\n<p>\r\n\tEn 1892, le botaniste russe Dimitri Ivanovsky d\u00e9couvre les virus s'attaquant sp\u00e9cifiquement aux plantes et, en 1898, Friedrich Loeffler et Paul Frosch d\u00e9couvrent les virus s'attaquant sp\u00e9cifiquement aux animaux. Tout comme les bact\u00e9riophages, ces deux\r\n\tcat\u00e9gories de virus pr\u00e9sentent une pr\u00e9f\u00e9rence marqu\u00e9e pour certaines cellules h\u00f4tes bien pr\u00e9cises. Il est possible que ces pr\u00e9f\u00e9rences d\u00e9coulent de l'origine des virus. Certains th\u00e9oriciens croient que ces derniers seraient des particules infracellulaires\r\n\tet autoreproductrices provenant de cellules d\u00e9g\u00e9n\u00e9r\u00e9es.\r\n<\/p>\r\n<p>\r\n\tLes virus infectent les cellules par fusion, endocytose ou injection de leur mat\u00e9riel g\u00e9n\u00e9tique. Chez certains virus, l'enveloppe virale fusionne avec la membrane cellulaire d'une cellule h\u00f4te et le g\u00e9nome du virus p\u00e9n\u00e8tre dans la cellule. Dans le cas\r\n\tde l'endocytose, la cellule h\u00f4te phagocyte (ing\u00e8re) le virus. L'ingestion est d\u00e9clench\u00e9e par le contact de la cellule avec une particule virale. Dans la cellule, le mat\u00e9riel g\u00e9n\u00e9tique se s\u00e9pare de la capside.\r\n\t<update>L'injection, une technique reproduite dans les laboratoires de <a href=\"\/article\/genetic-engineering\/\">G\u00c9NIE G\u00c9N\u00c9TIQUE<\/a>, est un processus propre aux bact\u00e9riophages. Le bact\u00e9riophage (virus) s'attache \u00e0 la paroi cellulaire de la bact\u00e9rie et injecte\r\n\t\tson acide nucl\u00e9ique, la capside demeurant \u00e0 l'ext\u00e9rieur de la paroi. Une fois \u00e0 l'int\u00e9rieur de la cellule h\u00f4te, l'acide nucl\u00e9ique viral sera reproduit.<\/update>\r\n<\/p>\r\n<p>\r\n\t<update>Selon le type de virus, une fois \u00e0 l'int\u00e9rieur d'une cellule h\u00f4te, l'ADN ou l'ARN viral peut s'int\u00e9grer au g\u00e9nome de la cellule ou imm\u00e9diatement \u00eatre reproduit jusqu'\u00e0 la lyse (d\u00e9g\u00e9n\u00e9rescence) de la cellule. Dans le cas de l'int\u00e9gration, la cellule h\u00f4te\r\n\t\tsubit des modifications au cours desquelles elle acquiert plusieurs caract\u00e9ristiques propres aux cellules canc\u00e9reuses (<em>voir <\/em><a href=\"\/article\/cancer\/\">CANCER<\/a>).<\/update>\r\n<\/p>\r\n<p>\r\n\t<update>Le g\u00e9nome du virus, qui est int\u00e9gr\u00e9, est conserv\u00e9 et se reproduit en m\u00eame temps que celui de la cellule h\u00f4te. Le g\u00e9nome peut, par la suite, se r\u00e9activer et la cellule entre alors dans un cycle lytique au cours duquel elle produit et lib\u00e8re de nombreux\r\n\t\texemplaires des virions qui peuvent ensuite infecter d'autres cellules. On conna\u00eet bien la relation entre les virus et certains cancers chez l'homme et on sait que les virus peuvent aussi causer de nombreux cancers chez d'autres esp\u00e8ces de <a href=\"\/article\/vertebrate\/\">VERT\u00c9BR\u00c9S<\/a>.<\/update>\r\n<\/p>\r\n<p>\r\n\tLorsqu'une cellule est parasit\u00e9e par un virus lytique, ses propres facult\u00e9s de synth\u00e8se sont souvent inhib\u00e9es, mais elle produit des centaines de copies conformes du virion qui l'infecte. Les processus de reproduction employ\u00e9s par les virus \u00e0 ARN sont\r\n\tvari\u00e9s et complexes. Dans certains cas, l'ARN viral sert directement d'ARN messager. Celui-ci ordonne aux ribosomes de la cellule h\u00f4te (organites cellulaires qui permettent la synth\u00e8se des prot\u00e9ines) de produire des prot\u00e9ines et enzymes viraux. Dans\r\n\td'autres cas, avant que la synth\u00e8se des prot\u00e9ines virales ne commence, de nombreuses copies d'ARN messager sont produites \u00e0 partir de l'ARN du virus.\r\n<\/p>\r\n<p>\r\n\tLa majorit\u00e9 des virus \u00e0 ADN se reproduisent dans le noyau de la cellule h\u00f4te, se servant des enzymes de celle-ci pour synth\u00e9tiser l'ARN messager \u00e0 partir de l'ADN viral. L'assemblage des virus dans la cellule h\u00f4te est un processus complexe et encore mal\r\n\tcompris. Les virus \u00e0 ARN, par exemple, peuvent pr\u00e9senter une forme sph\u00e9rique simple ou des formes complexes poss\u00e9dant une enveloppe membranaire ou encore d'autres structures. Les virus \u00e0 ADN peuvent se former en \u00ab usine \u00bb dans le cytoplasme de la cellule\r\n\th\u00f4te ou bourgeonner au niveau de la membrane de celle-ci. Certains virus, avant d'\u00eatre assembl\u00e9s en virions matures, s'entourent d'une membrane form\u00e9e \u00e0 partir de la membrane nucl\u00e9aire ou cytoplasmique de la cellule h\u00f4te. Cette membrane incorpore des\r\n\tglycoprot\u00e9ines cod\u00e9es par le mat\u00e9riel g\u00e9n\u00e9tique du virus.\r\n<\/p>\r\n<p>\r\n\tLes virus provoquent de graves maladies chez les plantes et les animaux. On ne conna\u00eet cependant pas de traitements efficaces pour gu\u00e9rir ces maladies. La s\u00e9lection g\u00e9n\u00e9tique permet de produire des souches de plantes r\u00e9sistantes aux virus, mais cette\r\n\tapproche ne s'applique pas \u00e0 l'homme. On a r\u00e9cemment mis au point certains m\u00e9dicaments antiviraux prometteurs. Ces substances (p. ex. l'acyclovir, qui est utilis\u00e9 pour traiter les infections herp\u00e9tiques) n'agissent toutefois que sur un nombre limit\u00e9\r\n\tde virus.\r\n<\/p>\r\n<p>\r\n\tLe d\u00e9veloppement de vaccins contre les maladies virales a connu plus de succ\u00e8s. Ces vaccins, lorsque d\u00fbment administr\u00e9s, ont contribu\u00e9 \u00e0 l'\u00e9radication de la variole au niveau mondial, ainsi qu'\u00e0 la quasi-disparition de la poliomy\u00e9lite, de la rougeole\r\n\tet de la rub\u00e9ole chez certaines populations.\r\n\t<update>Au Canada, les autorit\u00e9s de la <a href=\"\/article\/public-health\/\">SANT\u00c9 PUBLIQUE<\/a> de chaque province maintiennent un programme de vaccination, particuli\u00e8rement aupr\u00e8s des jeunes enfants. Certains virus, sp\u00e9cialement le virus de l'immunod\u00e9ficience humaine\r\n\t\t(VIH) qui cause le syndrome d'immunod\u00e9ficience acquise ou SIDA, sont toujours r\u00e9fractaires aux deux approches. On tente activement d'\u00e9laborer des m\u00e9thodes de traitement innovatrices.<\/update>\r\n<\/p>\r\n<p>\r\n\tDe nos jours, les virologistes s'inqui\u00e8tent \u00e9norm\u00e9ment de l'apparition de nouveaux virus ou de la r\u00e9apparition de virus pathog\u00e8nes connus, comme le VIH, et de la capacit\u00e9 du r\u00e9seau de la sant\u00e9 publique \u00e0 soigner et limiter l'effet de ces organismes.<em>Voir aussi <\/em>\r\n\t<a href=\"\/article\/biological-product\/\">PRODUIT BIOLOGIQUE<\/a>; <a href=\"\/article\/pharmacy\/\">PHARMACIE<\/a>; <a href=\"\/article\/veterinary-medicine\/\">M\u00c9DECINE V\u00c9T\u00c9RINAIRE<\/a>.\r\n<\/p>","slug":"virus","alt_slug":"","twitter_summary":null,"locale":"fr","automated":false,"hidden":0,"views":0,"created_at":"2006-02-08T00:00:00.000000Z","updated_at":"2019-10-16T20:34:44.000000Z"}]},{"id":"80652","author_text":"C\u00c9line Arseneault","revisor":null,"major_update":null,"trigger_warning":0,"views":0,"shares":0,"type":"article","itunes_songs":null,"indigo":null,"itunes_title_en":null,"itunes_title_fr":null,"indigo_title_en":null,"indigo_title_fr":null,"status":"published","schedule_from":null,"schedule_until":null,"created_at":"2006-02-08T00:00:00.000000Z","updated_at":"2015-02-10T14:28:45.000000Z","deleted_at":null,"title":"Violet","slug":"violet","alt_slug":null,"summary":"The Violet is a family (Violaceae) of annual or perennial herbaceous plants widely distributed throughout temperate and tropical regions. Tropical species may reach tree size. Roughly 500 species of genera Viola (violets, pansies) and Hybanthus (green violets) alone occur worldwide.","body":"<h3>Violet<\/h3>\r\n<p>\r\n\t The Violet is a family (Violaceae) of annual or perennial herbaceous plants widely distributed throughout temperate and tropical regions. Tropical species may reach tree size. Roughly 500 species of genera <em>Viola<\/em> (violets, pansies) and <em>Hybanthus<\/em> (green violets) alone occur worldwide. The 35 species of <em>Viola<\/em> native to Canada are found in abundance in woods, prairies and marshes from the Atlantic to the Pacific and north to the treeline. One green violet species (<em>H. concolor<\/em>) occurs in southern Ontario. Some violets produce 2 kinds of flowers. In spring, colourful flowers (eg, purple, blue, white) are produced for pollination by insects. Green, petalless, self-pollinating flowers are produced in summer. These are more fruitful and ensure seed set if earlier flowers were affected by cold. Many species are popular as <a href=\"\/article\/ornamentals\/\">ornamentals<\/a>, mainly for rock gardens and shaded areas, where they prefer moist, rich soil. The hooded or purple violet (<em>V. cucullata<\/em>) has a rich purple flower and a rosette of heart-shaped leaves. It has been the <a href=\"\/article\/provincial-floral-emblems\/\">Provincial Floral Emblem<\/a> of New Brunswick since 1936.\r\n<\/p>","twitter_summary":null,"pivot":{"model_id":"77320","relatable_id":"80652","relatable_type":"App\\Models\\Article","position":0},"translations":[{"id":"31abf29f-1a1a-4058-8812-676a116e66da","article_id":"80652","title":"Violet","summary":"The Violet is a family (Violaceae) of annual or perennial herbaceous plants widely distributed throughout temperate and tropical regions. Tropical species may reach tree size. Roughly 500 species of genera Viola (violets, pansies) and Hybanthus (green violets) alone occur worldwide.","body":"<h3>Violet<\/h3>\r\n<p>\r\n\t The Violet is a family (Violaceae) of annual or perennial herbaceous plants widely distributed throughout temperate and tropical regions. Tropical species may reach tree size. Roughly 500 species of genera <em>Viola<\/em> (violets, pansies) and <em>Hybanthus<\/em> (green violets) alone occur worldwide. The 35 species of <em>Viola<\/em> native to Canada are found in abundance in woods, prairies and marshes from the Atlantic to the Pacific and north to the treeline. One green violet species (<em>H. concolor<\/em>) occurs in southern Ontario. Some violets produce 2 kinds of flowers. In spring, colourful flowers (eg, purple, blue, white) are produced for pollination by insects. Green, petalless, self-pollinating flowers are produced in summer. These are more fruitful and ensure seed set if earlier flowers were affected by cold. Many species are popular as <a href=\"\/article\/ornamentals\/\">ornamentals<\/a>, mainly for rock gardens and shaded areas, where they prefer moist, rich soil. The hooded or purple violet (<em>V. cucullata<\/em>) has a rich purple flower and a rosette of heart-shaped leaves. It has been the <a href=\"\/article\/provincial-floral-emblems\/\">Provincial Floral Emblem<\/a> of New Brunswick since 1936.\r\n<\/p>","slug":"violet","alt_slug":null,"twitter_summary":null,"locale":"en","automated":false,"hidden":0,"views":0,"created_at":"2006-02-08T00:00:00.000000Z","updated_at":"2015-02-10T14:28:45.000000Z"},{"id":"5b445492-f4a8-46b3-9e84-06dc64dcbc98","article_id":"80652","title":"Violette","summary":"La familles des violettes (Violac\u00e9es) est compos\u00e9e de plantes herbac\u00e9es annuelles ou vivaces largement r\u00e9parties dans les r\u00e9gions temp\u00e9r\u00e9es et tropicales. Les esp\u00e8ces tropicales ont parfois les dimensions d'un arbre.","body":"<h3>Violette<\/h3>\r\n<p>\r\n\t La familles des violettes (Violac\u00e9es) est compos\u00e9e de plantes herbac\u00e9es annuelles ou vivaces largement r\u00e9parties dans les r\u00e9gions temp\u00e9r\u00e9es et tropicales. Les esp\u00e8ces tropicales ont parfois les dimensions d'un arbre. Les genres <em>Viola<\/em> (violettes, pens\u00e9es) et <em>Hybanthus<\/em> (hybanthes) comptent \u00e0 eux seuls environ 500 esp\u00e8ces dans le monde. Les 35 esp\u00e8ces de <em>Viola<\/em> indig\u00e8nes du Canada sont abondantes dans les for\u00eats, les prairies et les marais d'un oc\u00e9an \u00e0 l'autre et vers le Nord jusqu'\u00e0 la limite foresti\u00e8re. Une esp\u00e8ce d'hybanthes (<em>H. concolor<\/em>) se rencontre dans le Sud de l'Ontario. Certaines esp\u00e8ces de violettes produisent deux sortes de fleurs : des fleurs printani\u00e8res color\u00e9es (par exemple pourpres, bleues, blanches), qui se reproduisent gr\u00e2ce \u00e0 la pollinisation par les insectes, et des fleurs estivales vertes sans p\u00e9tales, qui se reproduisent par autopollinisation. Ces derni\u00e8res produisent plus de fruits et assurent la production de graines si les fleurs printani\u00e8res sont touch\u00e9es par le froid. Plusieurs esp\u00e8ces sont recherch\u00e9es comme <a href=\"\/article\/ornamentals\/\">PLANTES ORNEMENTALES<\/a>, surtout pour les rocailles de jardins et les endroits ombrag\u00e9s, o\u00f9 elles croissent bien dans un sol riche et humide. La violette cucull\u00e9e (<em>V. cucullata<\/em>) a une fleur d'un pourpre profond et ses feuilles cordiformes sont dispos\u00e9es en rosette. Cette fleur est l'embl\u00e8me floral provincial du Nouveau-Brunswick (<em>voir <\/em><a href=\"\/article\/provincial-floral-emblems\/\">EMBL\u00c8MES FLORAUX DES PROVINCES<\/a>) depuis 1936.\r\n<\/p>","slug":"violette","alt_slug":null,"twitter_summary":null,"locale":"fr","automated":false,"hidden":0,"views":0,"created_at":"2006-02-08T00:00:00.000000Z","updated_at":"2015-02-10T14:28:45.000000Z"}]},{"id":"80690","author_text":"Gillian Ford","revisor":null,"major_update":null,"trigger_warning":0,"views":0,"shares":0,"type":"article","itunes_songs":null,"indigo":null,"itunes_title_en":null,"itunes_title_fr":null,"indigo_title_en":null,"indigo_title_fr":null,"status":"published","schedule_from":null,"schedule_until":null,"created_at":"2007-01-30T00:00:00.000000Z","updated_at":"2015-12-17T19:16:22.000000Z","deleted_at":null,"title":"Water Lily","slug":"water-lily","alt_slug":null,"summary":"A large family of freshwater plants known as the water lily (Nymphaeaceae) is characterized by large, shield-shaped leaves and showy blossoms. They are mostly tropical or subtropical. Four genera and 9 species are native to Canada, of which 3 species are important.","body":"<h3>Water Lily<\/h3>\r\n<p>\r\n\tA large family of freshwater plants known as the water lily (Nymphaeaceae) is characterized by large, shield-shaped leaves and showy blossoms. They are mostly tropical or subtropical. Four genera and 9 species are native to Canada, of which 3 species are important. Yellow pond lily, cow lily or spatterdock (<em>Nuphar variegatum<\/em>) has yellow, globular flowers. It occurs as far north as the Yukon Territory and is widespread throughout Canada. White or pygmy water lily (<em>Nymphaea tetragona<\/em>) is found in northern Canada. Sweet or fragrant water lily (<em>Nymphaea odorata<\/em>), the most beautiful of the 3, has waxy, white flowers, 10-15 cm across. It is found in ponds and quiet streams from southeastern Canada to Florida.\r\n<\/p>\r\n<p>\r\n\t<strong>Medicinal Uses<\/strong><br>\r\n\tAll are edible and were an important emergency food for Aboriginal peoples, the rhizome being boiled, baked or dried, and the seeds roasted and ground into a highly nutritious flour. The root, because of its astringent, antiseptic and demulcent properties, was used externally for healing sores and internally for inflammation and dysentery.\r\n<\/p>","twitter_summary":null,"pivot":{"model_id":"77320","relatable_id":"80690","relatable_type":"App\\Models\\Article","position":0},"translations":[{"id":"3187943a-da6f-415d-b60a-1e5d310a2537","article_id":"80690","title":"Water Lily","summary":"A large family of freshwater plants known as the water lily (Nymphaeaceae) is characterized by large, shield-shaped leaves and showy blossoms. They are mostly tropical or subtropical. Four genera and 9 species are native to Canada, of which 3 species are important.","body":"<h3>Water Lily<\/h3>\r\n<p>\r\n\tA large family of freshwater plants known as the water lily (Nymphaeaceae) is characterized by large, shield-shaped leaves and showy blossoms. They are mostly tropical or subtropical. Four genera and 9 species are native to Canada, of which 3 species are important. Yellow pond lily, cow lily or spatterdock (<em>Nuphar variegatum<\/em>) has yellow, globular flowers. It occurs as far north as the Yukon Territory and is widespread throughout Canada. White or pygmy water lily (<em>Nymphaea tetragona<\/em>) is found in northern Canada. Sweet or fragrant water lily (<em>Nymphaea odorata<\/em>), the most beautiful of the 3, has waxy, white flowers, 10-15 cm across. It is found in ponds and quiet streams from southeastern Canada to Florida.\r\n<\/p>\r\n<p>\r\n\t<strong>Medicinal Uses<\/strong><br>\r\n\tAll are edible and were an important emergency food for Aboriginal peoples, the rhizome being boiled, baked or dried, and the seeds roasted and ground into a highly nutritious flour. The root, because of its astringent, antiseptic and demulcent properties, was used externally for healing sores and internally for inflammation and dysentery.\r\n<\/p>","slug":"water-lily","alt_slug":null,"twitter_summary":null,"locale":"en","automated":false,"hidden":0,"views":0,"created_at":"2007-01-30T00:00:00.000000Z","updated_at":"2015-12-17T19:16:22.000000Z"},{"id":"66b3105d-21c0-444b-b29d-ffb3c375ce69","article_id":"80690","title":"Nymph\u00e9a","summary":"Nymph\u00e9a, genre important faisant partie d'une famille de plantes aquatiques (Nymph\u00e9ac\u00e9es), se caract\u00e9rise par de grandes feuilles en forme de bouclier et des fleurs remarquables. La plupart des esp\u00e8ces sont tropicales ou subtropicales.","body":"<h3>Nymph\u00e9a<\/h3>\r\n<p>\r\n\tNymph\u00e9a, genre important faisant partie d'une famille de plantes aquatiques (Nymph\u00e9ac\u00e9es), se caract\u00e9rise par de grandes feuilles en forme de bouclier et des fleurs remarquables. La plupart des esp\u00e8ces sont tropicales ou subtropicales. Au Canada, quatre genres et neuf esp\u00e8ces sont indig\u00e8nes; trois esp\u00e8ces sont importantes. Le grand n\u00e9nuphar jaune, pied-de-cheval ou n\u00e9nuphar \u00e0 fleurs panach\u00e9es (<em>Nuphar variegatum<\/em>) poss\u00e8de des fleurs globulaires jaunes. On le trouve aussi loin au nord que le Yukon et il est tr\u00e8s r\u00e9pandu partout au Canada. Le n\u00e9nuphar blanc (<em>Nymphaea tetragona<\/em>) se trouve dans le nord du Canada. Le nymph\u00e9a odorant ou n\u00e9nuphar blanc (<em>Nymphaea odorata<\/em>), le plus beau des trois, poss\u00e8de des fleurs blanches brillantes de 10 \u00e0 15 cm de diam\u00e8tre. On le trouve dans les \u00e9tangs et les cours d'eau calmes du sud-est du Canada jusqu'en Floride.\r\n<\/p>\r\n<p>\r\n\t<strong>Usages m\u00e9dicinaux<\/strong><br>\r\n\tToutes ces esp\u00e8ces sont comestibles et constituaient une importante aide alimentaire d'urgence pour les autochtones. Le rhizome \u00e9tait soit bouilli, soit cuit, soit s\u00e9ch\u00e9 et les graines \u00e9taient r\u00f4ties et moulues pour faire une farine tr\u00e8s nourrissante. En raison de ses propri\u00e9t\u00e9s adoucissantes, antiseptiques et astringentes, le rhizome \u00e9tait utilis\u00e9 en application externe pour soulager les douleurs et de fa\u00e7on interne pour soigner l'inflammation et la dysenterie.\r\n<\/p>","slug":"nymphea","alt_slug":null,"twitter_summary":null,"locale":"fr","automated":false,"hidden":0,"views":0,"created_at":"2007-01-30T00:00:00.000000Z","updated_at":"2015-12-17T19:16:22.000000Z"}]}],"associated_collections":[]}" header="Content" ></article-sidebar> </div> <div class="main-content"> <input class="js-picture-information" type="hidden" value="[{"filename":"e2366ba0-9f18-4eec-968d-6f1076b512b0","title":null,"alt":null,"source":null,"creator":null,"caption":null}]"> <main class="main-grid"> <article class="article main-grid__content"> <input type="hidden" id="isUserLogin" name="loginuser" value=""> <aside id="articlewidgets" class="article-widgets"> <input type="checkbox" class="menu-open" name="menu-open" id="menu-open"/> <label class="widget-open-button" for="menu-open"> <span class="dot--1"></span> <span class="dot--2"></span> <span class="dot--3"></span> </label> <button data-target="popup-citation" data-toggle="modal" class="widget-item articleNavPopupEvent"> <div class="widget-item__icon--citation"></div> <span class="widget-item__title">Citation</span> </button> <button data-toggle="modal" class="widget-item articleNavPopupEvent js-edit-submit"> <div class="widget-item__icon--edit"></div> <span class="widget-item__title">Suggest an Edit</span> </button> <button data-target="popup-translation" data-toggle="modal" class="widget-item articleNavPopupEvent js-translation"> <div class="widget-item__icon--translate"></div> <span class="widget-item__title">Request translation</span> </button> <button id="popup-translation__original" class="widget-item hide-widget"> <div class="widget-item__icon--revert"></div> <span class="widget-item__title">Revert to English</span> </button> </aside> <div id="popup-translation" class="modal"> <div class="popup-wrapper"> <div class="popup-content"> <div class="popup-title"> <div role="heading">Request a Translation</div> <div> <a class="popup-close" data-dismiss="modal"></a> </div> </div> <div class="g-recaptcha" data-sitekey="'6LeIWwglAAAAANriZBXJ8HgScx2u6jGAx0gY0GKm'" data-callback="onSubmit" data-size="invisible"> </div> <div class="popup-body"> <div id="translation-language-picker"> <translation-select recaptcha-site-key="6LeIWwglAAAAANriZBXJ8HgScx2u6jGAx0gY0GKm" slug=treeline locale=en></translation-select> </div> </div> </div> </div> </div> <div id="translation-rating-snackbar"> <translation-rating show-rating=0 slug=treeline></translation-rating> </div> <div id="popup-edit" class="modal"> <div class="popup-wrapper"> <div class="popup-content"> <div class="popup-title"> <div>Suggest an Edit</div> <div> <a class="popup-close" data-dismiss="modal"></a> </div> </div> <div class="popup-body"> <div class="contact-form edit-form"> <div class="form-error-list"> <ul></ul> </div> <form method="POST" action="https://www.thecanadianencyclopedia.ca/en/submitArticle" accept-charset="UTF-8" class="form form-submit-edit form-main"><input name="_token" type="hidden" value="Vyu2xDiFKELFopbyUZojOc0Swq7CjMM1DrV3R9hO"> <input name="aid" type="hidden" value="77320"> <input name="edit" type="hidden" value="true"> <div class="input-group "> <label for="description">Enter your suggested edit(s) to this article in the form field below</label> <textarea id="text-editor" class="form-control input input-fullSpan" placeholder="Write your message here..." name="description" cols="50" rows="10"></textarea> </div> <div class="btn-container"> <div> <input class="disabled js-submitedit-submit b b-md b-invert" type="submit" value="Submit"> </div> <div> <a href="#" data-dismiss="modal" class="js-popup-close b-link">Cancel</a> </div> </div> </form> </div> </div> </div> </div> </div> <div id="popup-citation" class="modal"> <div class="popup-wrapper"> <div class="popup-content"> <div class="popup-title"> <div> Citation </div> <div> <a class="popup-close" data-dismiss="modal"></a> </div> </div> <div class="popup-body"> <ul class="list"> <li> <ul class="citation-reference"> <input id="copy1" type="text" value="MLA 8TH EDITION |聽Rowe, J. Stan and Serge Payette. "Treeline". <em>The Canadian Encyclopedia</em>, 19 June 2015, <em>Historica Canada</em>. www.thecanadianencyclopedia.ca/en/article/treeline. Accessed 06 March 2025."> <li class="title">MLA 8TH EDITION</li> <li class="description">Rowe, J. Stan and Serge Payette. "Treeline". <em>The Canadian Encyclopedia</em>, 19 June 2015, <em>Historica Canada</em>. www.thecanadianencyclopedia.ca/en/article/treeline. Accessed 06 March 2025.</li> <li class="link"><a data-text="Rowe, J. Stan and Serge Payette. "Treeline". <em>The Canadian Encyclopedia</em>, 19 June 2015, <em>Historica Canada</em>. www.thecanadianencyclopedia.ca/en/article/treeline. Accessed 06 March 2025." href="#" class="js-copy-clipboard b b-md b-invert b-modal-copy">Copy</a></li> </ul> </li> <li> <ul class="citation-reference"> <input id="copy2" type="text" value="APA 6TH EDITION |聽Rowe, J., & Payette, S. (2015). Treeline. In <em>The Canadian Encyclopedia</em>. Retrieved from https://www.thecanadianencyclopedia.ca/en/article/treeline"> <li class="title">APA 6TH EDITION</li> <li class="description">Rowe, J., & Payette, S. (2015). Treeline. In <em>The Canadian Encyclopedia</em>. Retrieved from https://www.thecanadianencyclopedia.ca/en/article/treeline</li> <li class="link"><a data-text="Rowe, J., & Payette, S. (2015). Treeline. In <em>The Canadian Encyclopedia</em>. Retrieved from https://www.thecanadianencyclopedia.ca/en/article/treeline" href="#" class="js-copy-clipboard b b-md b-invert b-modal-copy">Copy</a></li> </ul> </li> <li> <ul class="citation-reference"> <input id="copy3" type="text" value="CHICAGO 17TH EDITION | Rowe, J. Stan , and Serge Payette. "Treeline." <em>The Canadian Encyclopedia</em>. Historica Canada. Article published January 29, 2007; Last Edited June 19, 2015."> <li class="title">CHICAGO 17TH EDITION</li> <li class="description">Rowe, J. Stan , and Serge Payette. "Treeline." <em>The Canadian Encyclopedia</em>. 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Stan Rowe</a>, <a href='https://www.thecanadianencyclopedia.ca/en/author/serge-payette' class='b-link'>Serge Payette</a> </span> </p> </div> <div class="article-info__column--dates"> <p class="info-text">Published Online <span class="info-text__value--date"> January 29, 2007 </span> </p> <p class="info-text">Last Edited <span class="info-text__value--date"> June 19, 2015 </span> </p> </div> </div> <div class="article-toolbar"> <button data-target="popup-share" data-toggle="modal" class="article-toolbar__item articleNavPopupEvent"> <div class="article-toolbar__item__icon--share"></div> <span class="article-toolbar__item__title">Share</span> </button> <button id="js-print" class="article-toolbar__item"> <div class="article-toolbar__item__icon--print"></div> <span class="article-toolbar__item__title">Print</span> </button> </div> <div class="article-content"> <div class="article-content__summary"> The treeline is controlled by CLIMATE in interaction with SOIL. In the North, it is correlated generally with the modal (most common) position of the southern edge of the arctic front in summer, and with such temperature indices as the July 10掳C isotherm. </div> <div class="article-content-body"> <div id="article-content-def"> <div><img src="https://d3d0lqu00lnqvz.cloudfront.net/media/media/thumbnails/e2366ba0-9f18-4eec-968d-6f1076b512b0.jpg" title='Snow-covered Evergreen' alt='Snow-covered Evergreen' /><figcaption>Most conifers are evergreens, retaining their needlelike leaves for several years (Corel Professional Photos).</figcaption></div> <h3>Treeline</h3> <p> <a href="javascript:DisplayMedia('1995', '1995', '1995', 400, 268, 0, 0, 0);" name="1995"></a> The treeline marks the limit of <a href="/article/trees/">trees</a> latitudinally on continental plains and altitudinally on highlands and mountains (where it is sometimes called the timberline). Tree species still occur beyond this limit, but in shrub form, extending to the "tree-species line." </p> <h3>Controlling Factors</h3> <p> The treeline is controlled by <a href="/article/climate/">climate</a> in interaction with <a href="/article/soil/">soil</a>. In the North, it is correlated generally with the modal (most common) position of the southern edge of the arctic front in summer, and with such temperature indices as the July 10掳C isotherm. But wherever soils are deeper and warmer than normal, as in river valleys (eg, the <a href="/article/thelon-river/">Thelon</a>) or on upland, sandy <a href="/article/esker/">eskers</a>, ribbons of trees extend the treeline far into the tundra. </p> <p> <strong>Trees of the Treeline</strong><br> Characteristic treeline species are alpine fir, whitebark pine and alpine larch in the Rocky Mountains; in Alaska and northern Canada, co-existing black spruce, white spruce and larch. Similar species of spruce and larch, with pine and birch, continue the circumpolar treeline across Eurasia. </p> <p> <strong>Non-static Limit</strong><br> The pollen record (<em>see </em><a href="/article/palynology/">palynology</a>) and preserved wood show that treelines on this continent have fluctuated greatly in the past, advancing hundreds of kilometres during warm phases and retreating southward when the climate has deteriorated. Three major movements have been identified; the first during the Tertiary (65 to 1.65 million years ago), reaching Ellesmere Island; later in the Pleistocene (1.65 million to 10 000 years ago), reaching northernmost Greenland and Meighen and Banks islands; and most recently in the early Holocene (some 10 000 years ago), reaching the Mackenzie Valley and Tuktoyaktuk, NWT. Such movements take hundreds of years. </p> <p> Climatic changes can cause abrupt shifts in the treeline, because seed production and survival of seedlings are precarious near the limit of trees. The conifers are also susceptible to fire during dry periods, and this and cutting by humans make today's treeline a diffuse and unstable boundary. The dotted lines and the label "Approximate Limit of Trees" that indicate the treeline on northern National Topographic Survey maps are appropriately vague, partly because of a lack of field surveys. </p> </div> </div> <div id="def" class="article-content-body hide"></div> </div> <div id="article-definitions"> <definitions route="https://www.thecanadianencyclopedia.ca/en/json/define" id="treeline"></definitions> </div> <div class="article-widget widget-adsense"> <script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script> <ins class="adsbygoogle" style="display:inline-block;width:468px;height:60px" data-ad-client="ca-pub-3964766461879185" data-ad-slot="1946780682"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div> <h3 class="article-widget-title">Interested in plants?</h3> <p> <a href="http://www.thecanadianencyclopedia.ca/en/collection/botany/"><img src="https://d3d0lqu00lnqvz.cloudfront.net/media/widgets_collections/Botany%20Collection%20EN.jpg" style="opacity: 1;" alt=""></a> </p> </article> </main> <div id="modal-overlay" class="overlay"></div> <div id="article-image" class="article-img-modal" role="dialog" aria-labelledby="article-modal-title"> <button class="article-img-modal__close" aria-label="close image modal"></button> <div id="js-article-modal-image" class="article-img-modal__container"> <div class="image-container"> <img class="article-img-modal__img" src="" alt=""> </div> <div class="text-container"> <span role="heading" aria-level="3" id="article-modal-title" class="article-img-modal__title"></span> <span class="article-img-modal__description"></span> <span class="article-img-modal__creator"></span> </div> </div> </div> </div> </div> <div class="main-grid article-related">   <div class="callouts-layout main-grid__content--full"> <h3 id="recommended" class="callouts-layout__title">Recommended</h3> <div class="callouts-layout__grid"> <div class="callout-item"> <div class="callout-item__container"> <h6 class="callout-item__title"> <a class="callout-item__link" href="https://www.thecanadianencyclopedia.ca/en/article/virus" > Virus </a> </h6> <span class="callout-item__category">Article</span> </div> <div class="image-container"> <img loading="lazy" src="https://www.thecanadianencyclopedia.ca/images/tce_placeholder.jpg?v=e9dca980c9bdb3aa11e832e7ea94f5d9" alt="" class="image-container__image" /> </div> </div> <div class="callout-item"> <div class="callout-item__container"> <h6 class="callout-item__title"> <a class="callout-item__link" href="https://www.thecanadianencyclopedia.ca/en/article/violet" > Violet </a> </h6> <span class="callout-item__category">Article</span> </div> <div class="image-container"> <img loading="lazy" src="https://www.thecanadianencyclopedia.ca/images/tce_placeholder.jpg?v=e9dca980c9bdb3aa11e832e7ea94f5d9" alt="" class="image-container__image" /> </div> </div> <div class="callout-item"> <div class="callout-item__container"> <h6 class="callout-item__title"> <a class="callout-item__link" href="https://www.thecanadianencyclopedia.ca/en/article/water-lily" > Water Lily </a> </h6> <span class="callout-item__category">Article</span> </div> <div class="image-container"> <img loading="lazy" src="https://www.thecanadianencyclopedia.ca/images/tce_placeholder.jpg?v=e9dca980c9bdb3aa11e832e7ea94f5d9" alt="" class="image-container__image" /> </div> </div> </div> </div> </div> </div> </div> <footer id="footer"> <div class="full-width footer-first-part"> <div class="wrap--narrow"> <div class="footer-information grid--col2"> <div class="divider"> <h6>Updates? 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