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BOT 200 Dr. Meiers Chapter 5 Notes

by: Keely Egelhoff

BOT 200 Dr. Meiers Chapter 5 Notes 200

Marketplace > Western Illinois University > Botany > 200 > BOT 200 Dr Meiers Chapter 5 Notes
Keely Egelhoff
GPA 3.6

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About this Document

These notes cover the book material for chapter 5.
Introduction to Botany
Dr. Meiers
Class Notes
botany, Dr.Meiers, apicalmeristem, Primary, growth
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This 7 page Class Notes was uploaded by Keely Egelhoff on Tuesday September 20, 2016. The Class Notes belongs to 200 at Western Illinois University taught by Dr. Meiers in Fall 2016. Since its upload, it has received 12 views. For similar materials see Introduction to Botany in Botany at Western Illinois University.


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Date Created: 09/20/16
Chapter 5  Tissues and the Primary Growth of Stems - Body of herbs contains just three basic parts: leaves, stems, and roots - Primitive plants stem functioned primarily as transport and support structures - Stems of many species are a means of dispersal - Some parts of the plant can be microscopic or they are temporary - Plants absorb moisture through leaves made wet by fog - The derive minerals from wind- blown dust that dissolves on moist leaf surface - Angiosperms- flowering plants in the division of Manholiphyta, a plant that has flowers and produces seeds enclosed within a carpel. The angiosperms are a  large group and include herbaceous plants, shrubs, grasses, and most trees. - are the largest division in the plant kingdom? - Basal angiosperms- probably will not be familiar to you except for waterlilies, magnolias, and laurels - Eudicots- are broadleaf plants such as roses, asters, maples, and others - Monocots- are grasses, lilies, cattails, palms, philodendrons, bromeliads, and several others - Primary Plant Body- herbaceous body - Secondary Plant body- woody body - Herb- is a plant that never becomes woody and covered with bark often lives for less than a single year (snapdragons, petunias, beans, corn and wheat) - Herb Tissues are primary - Woody plants such as trees and shrubs (oaks, maples, magnolias, roses and boxwood) the wood and bark are secondary tissues - Few plants are surprising: palm trees are large, perennial and very hard buy they do not actually have wood thus they are giant herbs not woody plants  Basic Types of Cells and Tissues - All cells are customarily grouped into just three classes based on the nature of their walls: parenchyma, collenchyma, and sclerenchyma  Parenchyma - Parenchyma cells have only primary walls that remain thin - Parenchyma tissue- is a mass of parenchyma cells this is the most common type of cell and tissue constituting all soft parts of a plant - Soft leaves petals fruits and seeds are composed almost completely of parenchyma - Chlorenchyma cells are parenchyma cells involved in photosynthesis they have numerous chloroplasts and their thin walls allow light and carbon dioxide to pass through to the chloroplasts - Other types of pigmented cells as in flower petals and fruits also must be parenchyma cells with thin walls that permit the pigments in the protoplasm to be seen - Glandular cells that secrete nectar fragrances mucilage resins and oils are also parenchyma cells typically contain few chloroplasts buy have elevated amounts of dictyosomes and endoplasmic reticulum - Transfer cells- are parenchyma cells that mediate short- distance transport of material by means of a large extensive plasma membrane capable of holding numerous molecular pumps - Transfer cells increase their surface area by having extensive knobs ridges and other ingrowths on their inner surface of their walls this allows large scale molecular pumping - Some parenchyma cells function by dying at maturity - Some stamens and fruits must open and release pollen or seeds the opening may be formed by the parenchyma cells that die and break down or are torn apart - Large holes in plant are needed to diffuse gasses - Created when middle lamella decomposes and cells are released from neighbors or degeneration of parenchyma cells - Parenchyma tissue that conducts nutrients over long distances is phloem  Collenchyma - Collenchyma cells have a primary wall that remains thin in some areas but becomes thickened in other areas most often in the corners - The wall of collenchyma exhibits plasticity and the ability to be deformed by pressure or tension and to retain the new shape even if the pressure or tension ceases - Present in elongating shoot tips that must be long and flexible like in vining grape plants - Located right under epidermis or next to vascular bundles - Parenchyma cells are needed in the inner tissues for support - Collenchyma and turgid parenchyma work together like air pressure and a tire - Thick cell walls require more glucose for collenchyma - Usually only produced in shoot tips and young petioles  Sclerenchyma - Sclerenchyma- has both a primary wall and a thick secondary wall that is almost always lignified - Walls are elastic they can be deformed but they return to their original size and shape when the pressure or tension is released - Sclerenchyma cells develop from parenchyma cells in mature organs after they have stopped growing and have achieved their proper size and shape - While growing and elongating a young leaf must be supported by collenchyma if it is to continue to grow but after it has achieved its mature size and shape some cells of the leaf can mature into sclerenchyma and provide elastic support that maintains the leaf’s shape - Sclerenchyma supports the plant by its strength alone - Sclerenchyma cell walls are strong enough to prevent the protoplast from expanding - Sclerenchyma two parts conducting and mechanical - Mechanical is subdivided into long fibers and short sclereids both of which have elastic secondary walls - Fibers are found where strength and flexibility are important - Sclereids are short and more or less isodiametric (cuboidal) - They are brittle and inflexible - Strength or resistance is the only selective advantage of sclerenchyma the protoplast usually dies after the secondary wall has been deposited - Secondary walls become impregnated with lignin making them waterproof so nutrients can enter the cell only through plastmodesmata - Pits-areas around low depressions in the developing secondary wall - Pit-pair is where two pits meet - Conducting sclerenchyma transports water and is one of the types of vascular cells  External organization of stems - stem is an axis and shoot is the stem plus any leaves, flowers, or buds that maybe present - nodes- are where leaves attach - internodes- the regions between nodes - leaf axil- stem area just above the point where a leaf attaches - axillary bud- a miniature shoot with a dormant apical meristem and several young leaves it is either a vegetative bud if it will grow into a branch or a floral bud if it will grow into a flower or group of flowers - bud scales- small corky scales that protect the delicate organs inside - terminal bud- at the tip of each stem - leaf scars occur where leaves were attached - Phyllotaxy- arrangement of leaves on the stem and is important in positioning leaves so that they do not shade each other - If only one leaf is present at each node the stem has alternate phyllotaxy - Two leaves per node is opposite phyllotaxy - Three or more per node is whorled - In distichous phyllotazy leaves are arranged in only two (di) rows (- stichies) as in corn and irises - In decussate phyllotaxy leaves are arranged in four rows - this occurs in only some species with opposite leaves - Spiral phyllotaxy each leaf is located slightly to the side of the ones immediately above and below it and leaves form a spiral up the stem - All flowering plant shoots are based on this simple arrangement of nodes and internodes - Internodes can be wide (asparagus) intermediate or narrow (alfalfa sprouts) - Stolons- called runners are able to explore the soil to find optimal places for growth - Internodes are especially long and thin and their leaves do not expand thus stolons extend greatly without using much of the plant’s nutrients reserves - Bulbs- are short shoots that have thick fleshy leaves - Corms- vertical thick stems that have thin papery leaves (crocus and gladiolus) - Rhizomes- are fleshy horizontal stems that allow a plant to spread underground (bamboo, irises and canna lilies) - Tubers- are horizontal like rhizomes but they grow for only a short period and are mainly a means of storing nutrients (potatoes) - Only perennial plants that go through a dormant period need storage capacity - In order to produce new twigs leaves and roots in the favorable season they must draw on stored carbohydrates protection of their nutrient reserves corms bulbs rhizomes and tubers is most easily accomplished by buying them at depths that do not freeze or dry out - The axil of every leaf contains a bud only a few buds ever develop into a branch the others remain dormant or produce flowers - Trunk- the main shoot allowing the plant to reach brighter light in the top of the forest canopy - As long as the apical meristem is alive not all axillary buds are needed, if the meristem dies then the axillary buds become active and replace it allowing the growth of the shoot to continue  Internal Organization of stems  Arrangement of primary tissues - Epidermis - Epidermis- the outermost surface of an herbaceous stem it is a single layer of living parenchyma cells - Epidermis helps prevent water loss to the air - Acts as a barrier against invasion by bacteria and fungi as well as small insects - Thin walled parenchyma cells - Cutin- fatty substance that makes the wall impermeable to water - can be used for water retention but in most plants cutin builds up as a more or less pure layer called the cuticle - sometimes even wax will build up on top of the cutin - both resist digestive enzymes and provide defense against pathogens like fungi and bacteria - can also inhibit the entry of carbon dioxide needed for photosynthesis a totally impermeable epidermis would lead to a plants starvation - guard cells- prevent too much water loss - stomatal pores- a whole within the guard cells - guard cells and stomatal pores together constitute a stoma - guard cells swell by absorbing water and then the back wall allows them to open and allow CO in an2 O out 2 - most guard cells close at night - Trichomes/ hairs- elongated epidermal cells - They shade underlying tissues by blocking some incoming sunlight - Most die shortly after maturity but can stay alive as small secretory glands  Cortex - Cotex- interior to the epidermis - Composed of photosynthetic parenchyma and sometimes collenchyma - Mainly fit together but in certain plants they are large intercellular air spaces  Vascular tissues - Xylem- conducts water and mineral - Phloem- distributes sugars and minerals - Water and minerals enter xylem in the roots and are conducted upward to leaves and stems xylem sap travels through dead hollow cells not through tubes composed of living cells like our blood does - Phloem cells are living they pick up sugar from areas where it is abundant usually leaves during summer and tubers or rhizomes in spring and transport it to areas where sugar is needed especially growing tips of shoots roots young leaves and flowers - Later months phloem carries sugar into developing fruits and into the storage organs of perennial plants  Xylem - Tracheids and vessel elements are types of sclerenchyma - Tracheary element refers to either type of cell - New cells go into cell cycle arrest and stop dividing - Starts with a small parenchyma cell with only a thin primary wall but the cell becomes long and narrow and then deposits a secondary wall that reinforces the primary wall - Secondary wall is impermeable to water parts of wall are uncovered to allow water to enter and exit - Annular thickenings- simplest type of tracheary element organized as a set of rings - Provides a large surface area for water movement into and out of the cell but not much strength - Helical thickening- secondary wall exists as one to three helices interior to the primary wall - Scalariform thickening- provides much more strength because the secondary wall underlines most of the inner surface of the primary wall and is fairly extensive - Reticulate thickening- secondary wall is deposited in the shape of a net as the name suggests - Circular bordered pits- the most derived and strongest tracheary elements - Tracheary elements with annular thickenings are weak but a large percentage of their primary wall is free of secondary wall and available for water movement - Pitted elements are the opposite - Pit membrane is very permeable to water and is a set of primary walls that offers slight resistance - Vessel elements provide a way to move water with less friction than tracheids - Perforation is digested through a particular site of the primary wall often removing the entire end wall - Vessel- is a stack of vessel elements - Must absorb water from parenchyma cells tracheids and other vessels and must pass it on - Vessel elements have perforations complete holes in their walls were as tracheids only have pits - Water must move across pit membranes every time they enter or leave a tracheid or vessel  Phloem - Sieve cells and sieve tube members= sieve element - Parenchyma cells have only primary walls and must remain alive in order to conduct - Sieve pores- immature sieve elements that have enlarged plasmodesmata - Sieve areas- cluster of sieve pores - Sieve elements remain alive during differentiation and the plasma membrane that lined the plasmodesma continues to line the sieve pore - The amount of cytoplasm increase - The two types different shape and placement of sieve areas - Sieve cells are older and found in fossils, most efficient for sieve areas on the two ends of the cell to be especially large - Smaller cells are called sieve tube members they are stacked end to end with their large sieve areas aligned for sieve tubes - Sieve plates are end wall sieve areas with large sieve pores - Their nuclei degenerate but the cells remain alive - Abluminous cells and sieve tube members are controlled by companion cells they are smaller and have a prominent nucleus and dense cytoplasm filled with rhizomes  Vascular Bundles - Xylem and phloem together located just interior to the cortex - In basal angiosperms and eudicots vascular bundles are arranged in one ring surrounding the pith - Pith- a region of parenchyma similar to the cortex - In monocots vascular bundles are distributed as a complex network throughout the inner part of the stem - Collateral- all vascular bundles that is each contains both xylem and phloem strands running parallel to each other - Primary xylem- xylem of a vascular bundle it is part of the primary plant body - Vascular bundle phloem is primary phloem mixed with sieve elements and companion cells or albuminois cell may store parenchyma and mechanical sclerenchyma - Primary xylem is bigger than phloem and the inner bundles are smaller than the outer ones  Stem Growth and differentiation - Apical meristem- stems grow longer by creating new cells that their tips - Subapical meristem- cells expand and automatically push the meristem upward the lower cells are left behind as part of the young stem the region below is the subapical meristem - Visible differentiation begins certain cells stop dividing and star elongating and differentiation in to the first tracheids or vessel elements of the vascular bundles - Protoxylem- the first xylem to appear - Turned into tracheary elements that are even larger than the first this continues until the last cells mature - Metaxylem is the longest and largest growth time for xylem cells - Protoxylem must have either annular or helical secondary walls they are dead a maturity but they stretch due to glued to middle lamellas - Metaxylem does not have this problem because its cells differentiate only after all surrounding stem tissues have stopped elongating secondary wall is feasible - Protophloem- exterior mature cells closest to the metaxylem become metaphloem - Both walls are identical sieve elements are extremely sensitive to being stretched and die when stressed too much - Protophloem cells are extremely short lived - Never become well differentiated and many do not have companion cells - Sieve elements of metaphloem do not differentiate until later - Very small cells - In xylem cells stop dividing so each cell becomes larger photoxylem cells by being stretched and metaxylem by their own growth, protophloem cells stop dividing and differentiate however other phloem cells continue to divide and they therefore remain small - Protoderm- epidermal cells that are in the early stages of differentiation - Provascular tissues- young cells of xylem and phloem - Ground meristem- equivalent stages of pith and cortex - Subapical meristem= protoderm, ground meristem, provascular tissue, and ground meristem - Primary tissues- are the tissues produced by apical meristem - Primary growth- is the growth and tissue formation that results from apical meristem activity


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