{"id":167,"date":"2017-09-04T05:15:43","date_gmt":"2017-09-04T05:15:43","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/general-science\/?page_id=167"},"modified":"2017-10-20T10:56:35","modified_gmt":"2017-10-20T10:56:35","slug":"plants","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/general-science\/plants\/","title":{"rendered":"Plants"},"content":{"rendered":"<div class=\"twelve columns\" style=\"margin-top: 10%;\">\n<div class=\"advance\"><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/general-science\/organ-systems-ii\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/general-science\/genetics-and-physiology\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/general-science\/plant-growth\">Next Lesson \u27a1<\/a><\/div>\n<p><!-- CONTENT BEGINS HERE --><\/p>\n<h1 id=\"title\">Genetics &amp; Physiology: Plants<\/h1>\n<h4>Lesson Objective<\/h4>\n<p>We will now cover some of the important aspects of plant biology, culminating in an in depth look at plant physiology.<\/p>\n<h4>Previously we covered&#8230;<\/h4>\n<p>We have reviewed the physiology of animals in depth, going over animal organization and function from cell to tissue to organ to organ system. We will now turn our attention to plants.<\/p>\n<h4>Classification<\/h4>\n<p>Plants have the following characteristics:<\/p>\n<ul>\n<li>eukaryotic<\/li>\n<li>multicellular<\/li>\n<li>cell walls made of cellulose<\/li>\n<li>roots and shoots<\/li>\n<li>autotrophic<\/li>\n<li>reproduce sexually and asexually<\/li>\n<\/ul>\n<p>Plants are divided into two groups: nonvascular and vascular. Nonvascular plants, which include mosses and liverworts, have simple conducting tissue that does not differentiate into roots, stems, and leaves. Vascular plants have tissue that is differentiated into <strong>roots, stems<\/strong>, and <strong>leaves<\/strong> to facilitate the movement of water and other materials throughout the body of the plant.<\/p>\n<p>Vascular plants are divided into seedless plants and seed plants. Seedless plants include ferns, horsetails, whisk ferns, and club mosses. These plants live close to water. Over time, as plants developed farther away from water sources, they developed <strong>seeds.<\/strong> Seeds permit an embryo to survive long periods of time in unfavorable conditions and to disperse an embryo from its parent plant. Seed plants are further divided into gymnosperms and angiosperms. Most living gymnosperms are conifers, producing their seeds in cones. Some examples are: pine, cedar, cypress, redwood, spruce, and fir trees. Angiosperms, such as roses, daisies, grasses, and sunflowers, reproduce with flowers. The flowers promote pollination. Finally, angiosperms are divided into monocots and <strong>dicots<\/strong>. This distinction is based on the number of <strong>cotyledons<\/strong>, or seed leaves on the plant embryo. Monocots evolved later than dicots.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/monocotdicot.jpg\" width=\"336\" height=\"240\" \/><\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>The first land plants, still alive today, are<\/p>\n<ol>\n<li>gymnosperms.<\/li>\n<li>angiosperms.<\/li>\n<li>algae.<\/li>\n<li>ferns.<\/li>\n<\/ol>\n<p><a class=\"button button-primary q-answer\"> Reveal Answer <\/a><\/p>\n<p class=\"q-reveal\">The correct answer is C, because A and B are seed plants, which came much later. Choice D is also incorrect because ferns also came much later, but between algae and seed plants. The first land plants were algae.<\/p>\n<\/section>\n<h4>Flowering Plants: Seeds<\/h4>\n<p>A seed is a sporophyte plant embryo surrounded by a protective coat. The parts of the embryo are named according to their point of attachment to the cotyledons. The epicotyl is the stem above the cotyledon, and develops into the plant stem. Below the cotyledon is the hypocotyl, which has a region, called the radicle, at its base. The radicle develops into the plant&#8217;s roots. The rest of the embryo consists of the food supply.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/seed.jpg\" width=\"350\" height=\"243\" \/><\/p>\n<h4>Flowering Plants: Roots<\/h4>\n<p>Roots have a simple structure. They lack external features and pith. The vascular bundles are at the center of the root. Epidermal cells cover the end of the root and those near the root tip produce slender projections called root hairs. Root hairs increase the surface area of the root and absorb water and minerals from the soil. There are three types of root systems:<\/p>\n<p>A taproot system has a large central root called a taproot. The roots that branch from the taproot are usually much smaller. Most dicots have a taproot system. This root system can store sugars or starches. Some examples include carrots, radishes, beets, dandelions, oak trees, and hickory trees.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/taproot.jpg\" width=\"135\" height=\"268\" \/><\/p>\n<p>A fibrous root system is highly branched with roots that are about the same size. Most monocots have fibrous root systems. These systems are important in holding topsoil so that rain does not wash it away. Some examples include grasses and onions.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/fibrousroots.jpg\" width=\"377\" height=\"599\" \/><\/p>\n<p>Adventitious roots grow above ground and provide support, as well as absorbing water. Two types of this root system are prop roots and aerial roots. Some examples include corn, mangroves, and orchids.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/adventitiousroots.jpg\" width=\"730\" height=\"530\" \/><\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>A primary root that grows longer and thicker is<\/p>\n<ol>\n<li>root hair.<\/li>\n<li>a tap root.<\/li>\n<li>a fibrous root.<\/li>\n<li>an adventitious root.<\/li>\n<\/ol>\n<p><a class=\"button button-primary q-answer\"> Reveal Answer <\/a><\/p>\n<p class=\"q-reveal\">The correct answer is B. A taproot is long and thick with shorter roots that branch off it. Choice A refers to the slender projections off root tips. Choice C and D are types of root systems.<\/p>\n<\/section>\n<h4>Flowering Plants: Stems<\/h4>\n<p>Stems vary in size and shape from one plant species to another but all stems have two basic functions: holding leaves up in the sunlight and conducting various substances between roots and leaves. In addition, some stems store water and nutrients.<\/p>\n<p>Stems have four basic types of tissue:<\/p>\n<ul>\n<li>parenchyma (pith)<\/li>\n<li>vascular tissue (<strong>xylem<\/strong> and <strong>phloem<\/strong>)<\/li>\n<li><strong>cambium <\/strong>tissue (vascular <strong>cambium<\/strong> and cork cambium)<\/li>\n<li>cork tissue (outer bark).<\/li>\n<\/ul>\n<p>Vascular tissue in stems conducts water, nutrients, and other materials throughout the plant. The arrangement of this tissue in the stem differs in monocots and dicots. In monocots vascular tissue is scattered in bundles throughout the stem. In dicots it is arranged in a ring.<\/p>\n<p>The places where leaves attach to a stem are called nodes. Internodes are the areas of stem between the nodes. Also at the nodes are lateral buds that grow into branches of the stem. There are two main types of stems: <strong>herbaceous<\/strong> and <strong>woody.<\/strong><\/p>\n<p>Herbaceous stems are flexible, relatively soft, and usually green in color.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/herbstem.jpg\" width=\"267\" height=\"598\" \/><\/p>\n<p>Woody stems are stiff, contain layers of wood, and usually are not green in color.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/woodystem.jpg\" width=\"396\" height=\"599\" \/><\/p>\n<p>Some stems are modified for other functions and include rhizomes, tubers, and bulbs.<\/p>\n<p>Rhizomes are thick, fleshy, creeping stems that grow either alongside or beneath the surface of the ground. When winter frost kills the above-ground parts of plants, the rhizomes survive to grow again the following springs. Examples of plants with rhizomes are irises, canna lilies and some species of grasses.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/rhizome.jpg\" width=\"253\" height=\"158\" \/><\/p>\n<p>Tubers are modified underground stems that are swollen with stored food, usually starch. The most common example of a tuber is the potato.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/tuber.jpg\" width=\"252\" height=\"168\" \/><\/p>\n<p>Bulbs have underground stems. The stem at the center is small. Most of the food stored is located in layers of leaves that wrap around and protect the stem. Examples of plants with bulbs include daffodils and tulips.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/bulb.jpg\" width=\"349\" height=\"599\" \/><\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Which of the following is a modified stem?<\/p>\n<ol>\n<li>Cactus spine<\/li>\n<li>Pine needle<\/li>\n<li>Irish potato<\/li>\n<li>Carrot<\/li>\n<\/ol>\n<p><a class=\"button button-primary q-answer\"> Reveal Answer <\/a><\/p>\n<p class=\"q-reveal\">C is the correct answer, because the potato has a modified stem called a tuber. Choices A and B are modified leaves. Choice D is a modified root.<\/p>\n<\/section>\n<h4>Flowering Plants: Leaves<\/h4>\n<p>The leaves of a plant are the world&#8217;s most important manufacturers of food. Most leaves have a basic structure of a large, flattened surface called the blade that is attached to the stem by a petiole.<\/p>\n<p>Leaves with a single blade and petiole are simple leaves. Compound leaves have several blades, or leaflets.<\/p>\n<p>Veins, which are strands of xylem and phloem tissue, run along the leaves.<\/p>\n<p>Leaves are covered by a layer of tough epidermal cells and a waxy cuticle. Within the epidermis are small openings called stomata, which are formed by two specialized epidermal cells called guard cells. Gas exchange takes place through the stomata.<\/p>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/leafcross.jpg\" width=\"344\" height=\"248\" \/><\/p>\n<p>Most leaf tissue is composed of specialized cells called <strong>mesophyll<\/strong>. This tissue contains chloroplasts and performs most of the plant&#8217;s photosynthesis. The mesophyll is divided into two layers. The top layer consists of rows of closely packed, columnar cells and is called the <strong>palisade layer<\/strong>. The lower layer has loosely packed, spherical cells and is called the <strong>spongy layer<\/strong>.<\/p>\n<p>Some plants have modified leaves specialized for protection, water conservation, climbing, and reproduction. Remember that most plant parts are basically modified leaves.<\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Openings that permit gases to enter and leave the leaf are called<\/p>\n<ol>\n<li>cuticles.<\/li>\n<li>stomata.<\/li>\n<li>palisade cells.<\/li>\n<li>chloroplasts.<\/li>\n<\/ol>\n<p><a class=\"button button-primary q-answer\"> Reveal Answer <\/a><\/p>\n<p class=\"q-reveal\">The correct answer is B. Stomata are formed from guard cells and control gas exchange in leaves.<\/p>\n<\/section>\n<h4>Flowering Plants: Flowers<\/h4>\n<p>Flowers are the reproductive organs of angiosperms and usually produce both male and female gametes. Flowers are actually miniature stems that produce four kinds of specialized leaves: sepals, petals, stamens, and carpels. These leaves are arranged in circles and have been modified to serve different purposes.<\/p>\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li><strong>Sepals<\/strong> are the outermost circle of flower parts. They are green and actually resemble leaves. Sepals enclose a flower bud before it opens and protect the developing flower. The sepals held together form the <strong>calyx<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li><strong>Petals<\/strong> are the second circle of flower parts. They are inside the sepals and are usually brightly colored. The petals together form the corolla. The corolla often produces bright pigments and fragrances to attract pollinators.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li><strong>Stamens<\/strong> are the first circle of fertile leaves. Each stamen has a long, thin filament that supports an<strong> anther<\/strong>. The anthers contain pollen grains, which are the male gametes.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ul>\n<li><strong>Carpels<\/strong> are the centermost circle of flower parts and are produced from fertile leaves that are rolled up. One or more carpels form the <strong>pistil<\/strong>, which consists of a base called the <strong>ovary<\/strong>, a slender stalk called the <strong>style<\/strong>, and a swollen, sticky tip called the <strong>stigma<\/strong>. The ovaries contain<strong> ovules<\/strong>, which are the female gametes. The thickened part of the ovary wall that holds the seeds is called the fruit.<\/li>\n<\/ul>\n<p align=\"center\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/flower.jpg\" width=\"409\" height=\"250\" \/><\/p>\n<p>Flowers may or may not have all four parts, which classifies flowers into one of four categories:<\/p>\n<p><strong><em>Complete flowers<\/em><\/strong> have all four whorls of leaves. <img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/completeflower.jpg\" width=\"292\" height=\"241\" \/><\/p>\n<p><strong><em>Complete flowers<\/em><\/strong> have all four whorls of leaves. <img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/completeflower.jpg\" width=\"292\" height=\"241\" \/><\/p>\n<p><strong><em>Perfect flowers<\/em><\/strong> have both stamens and pistils. <img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/perfectflower.jpg\" width=\"190\" height=\"237\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/Images\/gensci\/7\/images\/imperfectflower.jpg\" width=\"312\" height=\"231\" \/><strong><em>Imperfect flowers<\/em><\/strong> lack either stamens or pistils.<\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Flower parts most involved with attracting pollinators are the<\/p>\n<ol>\n<li>pistils.<\/li>\n<li>seeds.<\/li>\n<li>anthers.<\/li>\n<li>petals.<\/li>\n<\/ol>\n<p><a class=\"button button-primary q-answer\"> Reveal Answer <\/a><\/p>\n<p class=\"q-reveal\">The correct answer is D, because the petals are usually brightly colored and have a fragrance to attract pollinators. Choice A is a female flower part and choice C is a male flower part, both of which have no qualities for attracting pollinators. Choice B, seeds, is the product of fertilization \u2014 long after pollinators are gone.<\/p>\n<\/section>\n<p><!-- CONTENT ENDS HERE --><\/p>\n<div class=\"advance\"><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/general-science\/organ-systems-ii\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/general-science\/genetics-and-physiology\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/general-science\/plant-growth\">Next Lesson \u27a1<\/a><\/div>\n<p><a class=\"backtotop\" href=\"#title\">Back to Top<\/a><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u2b05 Previous Lesson\u00a0Workshop Index\u00a0Next Lesson \u27a1 Genetics &amp; Physiology: Plants Lesson Objective We will now cover some of the important aspects of plant biology, culminating in an in depth look at plant physiology. Previously we covered&#8230; We have reviewed the physiology of animals in depth, going over animal organization and function from cell to tissue [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-167","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/pages\/167","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/comments?post=167"}],"version-history":[{"count":6,"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/pages\/167\/revisions"}],"predecessor-version":[{"id":729,"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/pages\/167\/revisions\/729"}],"wp:attachment":[{"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/media?parent=167"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}