{"id":342,"date":"2018-03-18T11:42:58","date_gmt":"2018-03-18T10:42:58","guid":{"rendered":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/?p=342"},"modified":"2020-01-18T22:39:18","modified_gmt":"2020-01-18T21:39:18","slug":"observer-les-stomates-sur-un-fragment-entier-de-feuille-une-alternative-au-prelevement-depiderme","status":"publish","type":"post","link":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/?p=342","title":{"rendered":"Observer les stomates sur un fragment entier de feuille (une alternative au pr\u00e9l\u00e8vement d&rsquo;\u00e9piderme)"},"content":{"rendered":"<div id=\"attachment_343\" style=\"width: 300px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-343\" class=\"wp-image-343 size-medium\" src=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image1-300x240.jpeg\" alt=\"\" width=\"300\" height=\"240\" srcset=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image1-300x240.jpeg 300w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image1-768x615.jpeg 768w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image1-1024x820.jpeg 1024w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image1-375x300.jpeg 375w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image1.jpeg 1386w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><p id=\"caption-attachment-343\" class=\"wp-caption-text\">Mat\u00e9riel n\u00e9cessaire<\/p><\/div>\n<p>L&rsquo;observation des stomates repose g\u00e9n\u00e9ralement sur l&rsquo;une des pr\u00e9parations suivantes :<\/p>\n<ul>\n<li>empreinte de la surface\u00a0foliaire \u00e0 l&rsquo;aide d&rsquo;un vernis<\/li>\n<li>ou pr\u00e9l\u00e8vement de l&rsquo;\u00e9piderme foliaire<\/li>\n<li>ou coupe transversale suffisamment fine pour observer la tranche de\u00a0la feuille<\/li>\n<\/ul>\n<p>Or, il est parfaitement possible d&rsquo;apercevoir ces structures en observant directement la surface d&rsquo;une feuille \u00e0 l&rsquo;aide d&rsquo;un microscope. <!--more--><\/p>\n<p>Afin de ne pas se trouver g\u00ean\u00e9 par la courbure naturelle de la feuille je recommande de d\u00e9couper un fragment d&rsquo;environ 1 cm\u00b2 et de le d\u00e9poser sur une lame sans le recouvrir d&rsquo;une lamelle. Sur la photographie ci-dessous il s&rsquo;agit d&rsquo;une feuille de Pittosporum tobira, un v\u00e9g\u00e9tal couramment utilis\u00e9 pour composer des haies. On prendra garde \u00e0 observer la face inf\u00e9rieure, vert clair, laquelle contient une forte densit\u00e9 de stomates.<\/p>\n<div id=\"attachment_344\" style=\"width: 300px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-344\" class=\"wp-image-344 size-medium\" src=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image2-300x256.jpeg\" alt=\"\" width=\"300\" height=\"256\" srcset=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image2-300x256.jpeg 300w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image2-768x656.jpeg 768w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image2-1024x875.jpeg 1024w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image2-351x300.jpeg 351w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image2.jpeg 1370w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><p id=\"caption-attachment-344\" class=\"wp-caption-text\">Stomates telles qu&rsquo;on les observe avec ce dispositif<\/p><\/div>\n<p>Les stomates apparaissent nettement au grossissement x100 (photographie ci-dessus). Il importe d&rsquo;augmenter au maximum l&rsquo;intensit\u00e9 lumineuse de la lampe du microscope, d&rsquo;ouvrir en grand le diaphragme et de placer le condenseur en position haute.<\/p>\n<p>Par ailleurs, un r\u00e9cent sujet d&rsquo;ECE portait sur le positionnement des stomates du Laurier rose (Nerium oleander) au fond de cryptes pilif\u00e8res. Le protocole fourni \u00e0 l&rsquo;\u00e9l\u00e8ve imposait la r\u00e9alisation\u00a0d&rsquo;une coupe transversale de la feuille puis une observation microscopique.<\/p>\n<p><a href=\"http:\/\/lewebpedagogique.com\/svtbertholon\/files\/2017\/05\/T.TP27.Laurier-rose.pdf\">http:\/\/lewebpedagogique.com\/svtbertholon\/files\/2017\/05\/T.TP27.Laurier-rose.pdf<\/a><\/p>\n<p>Or, il s&rsquo;av\u00e8re que ces cryptes pilif\u00e8res se voient extr\u00eamement bien en observant directement un fragment de feuille au grossissement x100 (photographie ci-dessous). R\u00e9ciproquement, l&rsquo;absence de stomates sur cette image constitue une source d&rsquo;\u00e9tonnement suffisante pour amorcer une d\u00e9marche d&rsquo;investigation.<\/p>\n<div id=\"attachment_345\" style=\"width: 300px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-345\" class=\"wp-image-345 size-medium\" src=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image3-300x259.jpeg\" alt=\"\" width=\"300\" height=\"259\" srcset=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image3-300x259.jpeg 300w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image3-768x662.jpeg 768w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image3-1024x883.jpeg 1024w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image3-348x300.jpeg 348w, https:\/\/www.pedagogie.ac-nice.fr\/svt\/wp-content\/uploads\/sites\/5\/2018\/03\/image3.jpeg 1386w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><p id=\"caption-attachment-345\" class=\"wp-caption-text\">Cryptes pilif\u00e8res telles qu&rsquo;on les observe avec ce dispositif<\/p><\/div>\n<p style=\"text-align: right\"><em>Auteur de l&rsquo;article : Julien Cartier<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>L&rsquo;observation des stomates repose g\u00e9n\u00e9ralement sur l&rsquo;une des pr\u00e9parations suivantes : empreinte de la surface\u00a0foliaire \u00e0 l&rsquo;aide d&rsquo;un vernis ou pr\u00e9l\u00e8vement de l&rsquo;\u00e9piderme foliaire ou coupe transversale suffisamment fine pour observer la tranche de\u00a0la feuille Or, il est parfaitement possible d&rsquo;apercevoir ces structures en observant directement la surface d&rsquo;une feuille \u00e0 l&rsquo;aide d&rsquo;un microscope.<\/p><p><a class=\"more-link btn\" href=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/?p=342\">Lire la suite<\/a><\/p>\n","protected":false},"author":74,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[4,126,127],"tags":[13,14],"class_list":["post-342","post","type-post","status-publish","format-standard","hentry","category-classe","category-en-college","category-en-lycee","tag-microscope","tag-tp","nodate","item-wrap"],"rttpg_featured_image_url":null,"rttpg_author":{"display_name":"Philippe COSENTINO","author_link":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/?author=74"},"rttpg_comment":0,"rttpg_category":"<a href=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/?cat=4\" rel=\"category\">En classe<\/a> <a href=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/?cat=126\" rel=\"category\">En coll\u00e8ge<\/a> <a href=\"https:\/\/www.pedagogie.ac-nice.fr\/svt\/?cat=127\" rel=\"category\">En lyc\u00e9e<\/a>","rttpg_excerpt":"L&rsquo;observation des stomates repose g\u00e9n\u00e9ralement sur l&rsquo;une des pr\u00e9parations suivantes : empreinte de la surface\u00a0foliaire \u00e0 l&rsquo;aide d&rsquo;un vernis ou pr\u00e9l\u00e8vement de l&rsquo;\u00e9piderme foliaire ou coupe transversale suffisamment fine pour observer la tranche de\u00a0la feuille Or, il est parfaitement possible d&rsquo;apercevoir ces structures en observant directement la surface d&rsquo;une feuille \u00e0 l&rsquo;aide d&rsquo;un microscope.","post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=\/wp\/v2\/posts\/342","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=\/wp\/v2\/users\/74"}],"replies":[{"embeddable":true,"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=342"}],"version-history":[{"count":5,"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=\/wp\/v2\/posts\/342\/revisions"}],"predecessor-version":[{"id":488,"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=\/wp\/v2\/posts\/342\/revisions\/488"}],"wp:attachment":[{"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=342"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=342"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.pedagogie.ac-nice.fr\/svt\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=342"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}