Ch. 25 – Plant Structure & Organization

Name: Ch. 25 – Plant Structure & Organization
Uploaded: 2017-08-27T15:29:45+00:00
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Description: Ch. 25 – Plant Structure & Organization

Ch. 25 – Plant Structure & Organization
Biology, 9th ed, Sylvia Mader Ch. 25 – Plant Structure & Organization Chapter 25 Structure and Organization of Plants

Biology, 9th ed, Sylvia Mader
Plant Organs Chapter 25 Structure and Organization of Plants Plants possess two types of systems: Root System Simply consists of roots Shoot System Consists of stems & leaves Vegetative Organs Roots, stems & leaves Reproductive Organs Flowers, seeds & fruits

Plant Organs Chapter 25 Structure and Organization of Plants Roots Generally, the root system is at least equivalent in size and extent to the shoot system Anchors plant in soil; gives support Absorbs water and minerals Produces hormones that stimulate growth of stems Root hairs: Projections from epidermal root hair cells Greatly increase absorptive capacity of root

Plant Organs Chapter 25 Structure and Organization of Plants Roots (cont’d) Perennial plants Vegetative structures live year to year Herbaceous Perennial plants Upper parts die back in winter Store energy in roots Examples: carrots, sweet potatoes

Organization of Plant Body
Biology, 9th ed, Sylvia Mader Organization of Plant Body Chapter 25 Structure and Organization of Plants

Vegetative Organs of Several Eudicots
Biology, 9th ed, Sylvia Mader Chapter 25 Vegetative Organs of Several Eudicots Structure and Organization of Plants

Stems Chapter 25 Structure and Organization of Plants Shoot system of a plant is composed of the stem, branches, and leaves Stem is the main axis of a plant that elongates and produces leaves Nodes occur where leaves are attached to the stem Internode is region between nodes Stem also has vascular tissue that transports water and minerals from roots through stem to leaves & transports products of photosynthesis

Stems Chapter 25 Structure and Organization of Plants Other functions of stems: Primary photosynthetic organ in cactus Water reservoir in succulents Store nutrients Tubers are horizontal or underground stems i.e. Potatoes

Leaves Chapter 25 Structure and Organization of Plants Leaves are the major part of the plant that carries on photosynthesis - Size, shape, color & texture of leaves vary. - Used for identification of plants Two main types of plants based on leaves: - Evergreens – retain leaves for 2-7 years - Deciduous – lose leaves every year

Leaves Chapter 25 Structure and Organization of Plants Foliage leaves are usually broad and thin for maximum surface area for absorption Blade - Wide portion of foliage leaf Petiole - Stalk attaches blade to stem Leaf Axil is the upper acute angle where axillary bud originates. May become leaf or flower. Tendrils - Leaves that attach to objects Bulbs - Leaves that store food

Monocots versus Eudicots
Biology, 9th ed, Sylvia Mader Monocots versus Eudicots Chapter 25 Structure and Organization of Plants Flowering plants are divided into 2 groups depending on number of cotyledons, or seed leaves in the embryonic plant. Monocots - One cotyledon Eudicots - Two cotyledons

Flowering Plants: Monocots or Eudicots
Biology, 9th ed, Sylvia Mader Flowering Plants: Monocots or Eudicots Chapter 25 Structure and Organization of Plants

Monocot vs. Eudicot Chapter 25 Structure and Organization of Plants Monocots (grasses, palm trees, rice, wheat, corn) Cotyledons act as transfer tissue; nutrients are derived from endosperm prior to the development of true leaves Root vascular tissue occurs in a ring Leaf veins are vascular bundles Parallel leaf venation Flower parts arranged in multiples of three

Monocot vs. Eudicot Chapter 25 Structure and Organization of Plants Eudicots (dandelions to oak trees) Cotyledons supply nutrients to seedlings Root phloem located between xylem arms - Pattern looks like a star Netted leaf venation - Pinnate – major veins originate from central vein - Palmate – major veins originate from point of attachment of blade to petiole

Plant Tissues Chapter 25 Structure and Organization of Plants Plants have ability to grow during entire lives because they possess meristematic tissue. Apical meristems - located at or near tips of stems & roots - increase the length of stems & roots - Increase in length is called primary growth - produce 3 types of tissues: epidermal, ground & vascular

Plant Tissues Chapter 25 Structure and Organization of Plants Epidermal Tissues Form protective outer covering called epidermis Contain closely packed epidermal cells Walls of epidermal cells exposed to air are covered with a waxy cuticle to minimize water loss Cuticle also protects against bacteria & disease Roots contain root hairs Leaves can have trichomes (hairs) to protect from sun & to conserve water. These can inject toxins into animals. Lower leaf surface contain stomata surrounded by guard cells. These regulate gas exchange & water loss.

Plant Tissues Chapter 25 Structure and Organization of Plants Epidermal tissues (cont’d) In woody plants, the epidermis of stem is replaced by periderm. - Major component is cork - Mature cork cells can be sloughed off - New cork cells are made by a meristem called the cork cambium

Modifications of Epidermal Tissue
Biology, 9th ed, Sylvia Mader Chapter 25 Structure and Organization of Plants Modifications of Epidermal Tissue

Ground Tissue Chapter 25 Structure and Organization of Plants Ground tissue forms bulk of interior of plant Formed of three types of cells: parenchyma, collenchyma & sclerenchyma Parenchyma cells: Most abundant & alive at maturity Least specialized and are found in all organs of plant. Can divide and give rise to more specialized cells Functions: photosynthesis, food storage, respiration

Chapter 25 Structure and Organization of Plants Ground Tissue Cells

Ground Tissue Chapter 25 Structure and Organization of Plants ●Collenchyma cells: Alive at maturity Have thicker primary walls Form bundles underneath epidermis Flexible support to immature regions of the plant Strands of celery are composed of these cells

Ground Tissue Chapter 25 Structure and Organization of Plants Sclerenchyma cells: Have thick secondary walls impregnated with lignin, a highly resistant substance that makes walls tough and hard Most are nonliving; dead at maturity Primary function is to support mature regions of the plant Two types of cells: fibers & sclereids

Vascular Tissue Chapter 25 Structure and Organization of Plants There are two types of vascular tissues: Xylem Transports water & minerals from roots to leaves Phloem Transports sucrose & other organic compounds, including hormones, usually from leaves to roots

Vascular Tissue Chapter 25 Structure and Organization of Plants Both xylem & phloem are considered complex tissues (those made of 2 or more kinds of cells) Xylem is made of: Tracheids (hollow non-living cells) Long, with tapered ends Pits in end walls help water move Vessel Elements (hollow non-living cells) Larger, with perforated plates in their end walls

Chapter 25 Structure and Organization of Plants Xylem Structure

Vascular Tissue - Phloem
Biology, 9th ed, Sylvia Mader Vascular Tissue - Phloem Chapter 25 Structure and Organization of Plants Phloem is composed of living cells: Sieve-tube members are conducting cells Form a continuous sieve tube; have pores in end walls Contain cytoplasm but no nuclei ●Companion cells attached to each sieve-tube Plasmodesmata extend between 2 types of cells. Companion cell’s nucleus might control sieve-tube.

Chapter 25 Phloem Structure Structure and Organization of Plants

Organization of Roots - Longitudinal section
Biology, 9th ed, Sylvia Mader Organization of Roots - Longitudinal section Chapter 25 Structure and Organization of Plants Apical meristem Located in the root tip Protected by root cap Zones of Root: Zone of cell division - primary meristems Zone of elongation - cells lengthen Zone of maturation - contains fully differentiated (specialized)cells. Cells on epidermis have root hairs.

Chapter 25 Eudicot Roots Structure and Organization of Plants

Tissues of Eudicot Root - Cross Section
Biology, 9th ed, Sylvia Mader Tissues of Eudicot Root - Cross Section Chapter 25 Structure and Organization of Plants Epidermis - single layer of cells Cortex - Large thin-walled parenchyma cells - Loosely packed - Possible for water to move without entering cells - Functions in food storage.

Biology, 9th ed, Sylvia Mader Tissues of Eudicot Root - Cross Section Chapter 25 Structure and Organization of Plants Endodermis - - Single layer of rectangular cells - Between cortex and inner vascular cylinder - Bordered on four sides by Casparian Strip. • This is a layer of impermeable lignin & suberin. • Prevents passage of water & mineral ions between adjacent cell walls.  access to vascular cylinder is through endodermal cells themselves

Biology, 9th ed, Sylvia Mader Tissues of Eudicot Root - Cross Section Chapter 25 Structure and Organization of Plants Vascular Tissue Pericycle - First layer of cells within vascular cylinder - Retains capacity to divide to start development of branch, or lateral, roots. •Xylem - Appears star-shaped in eudicots •Phloem - found between arms of xylem

Branching of Eudicot Root
Biology, 9th ed, Sylvia Mader Branching of Eudicot Root Chapter 25 Structure and Organization of Plants

Organization of Monocots Roots
Biology, 9th ed, Sylvia Mader Organization of Monocots Roots Chapter 25 Structure and Organization of Plants Monocot roots have same growth zones as eudicot roots, but do not undergo secondary growth. Ground tissue of root’s pith is surrounded by vascular ring - Ring composed of alternating bundles of xylem and phloem Have pericycle, endodermis, cortex & epidermis

Chapter 25 Monocot Root Structure and Organization of Plants

Root Diversity Chapter 25 Structure and Organization of Plants Primary root (taproot) - Fleshy, long single root, that grows straight down Often stores food Examples: carrots, beets, turnips, radishes Fibrous root system - Large # of slender roots and lateral branches Anchors plant to soil Found in grasses

Root Specializations Chapter 25 Structure and Organization of Plants Adventitous roots - Roots that develop from organs of the shoot system instead of root system Prop roots - emerge above soil line & function to help anchor the plant Others are found on horizontal stems or at nodes & help vines to climb (English Ivy)

Root Specializations Chapter 25 Structure and Organization of Plants Haustoria: Parasitic rootlike projections that grow into host plant Make contact with vascular tissue and extract water and nutrients Mycorrhizae: Associations between roots and fungi Extract water and minerals from soil better than roots alone • Example of mutualism (plants/fungus benefit)

Root Specializations Chapter 25 Structure and Organization of Plants Root nodules - Contain nitrogen-fixing bacteria • Found in peas, beans, and other legumes • Bacteria can take up atmospheric nitrogen & make it available to plants • Thus, plants aren’t dependent on supplies of nitrogen in the soil • Legumes often planted to bolster N supply of soil.

Chapter 25 Root Diversity Structure and Organization of Plants

Organization of Stems Chapter 25 Structure and Organization of Plants Shoot apical meristem Produces new cells that elongate and increase length of stem Protected by terminal bud Enveloped by leaf primordia (immature leaves)

Chapter 25 Structure and Organization of Plants Woody Twig

Shoot tip and Primary Meristems
Biology, 9th ed, Sylvia Mader Shoot tip and Primary Meristems Chapter 25 Structure and Organization of Plants

Organization of Stems Chapter 25 Structure and Organization of Plants ● Specialized primary meristems Protoderm – gives rise to epidermis Ground Meristem – produces 2 tissues composed of parenchyma cells: - pith (center of stem) - cortex (between epidermis & vascular tissue)

Shoot tip and Primary Meristems
Biology, 9th ed, Sylvia Mader Shoot tip and Primary Meristems Chapter 25 Structure and Organization of Plants

Organization of Stems Chapter 25 Structure and Organization of Plants ●Procambium Produces first xylem cells, primary xylem & first phloem cells, primary phloem. Differentiation occurs which produces mature xylem, phloem and a lateral meristem called vascular cambium. This tissue will lead to secondary growth (growth in width)

Herbaceous Stems Chapter 25 Structure and Organization of Plants Mature nonwoody stems that exhibit only primary growth Outermost tissue is epidermis covered with waxy cuticle Stems have distinctive vascular bundles Herbaceous eudicots - Vascular bundles arranged in distinct ring Monocots - Vascular bundles scattered throughout stem

Herbaceous Eudicot Stem
Biology, 9th ed, Sylvia Mader Herbaceous Eudicot Stem Chapter 25 Structure and Organization of Plants

Chapter 25 Monocot Stem Structure and Organization of Plants

Woody Stems Chapter 25 Structure and Organization of Plants Woody plants have both primary and secondary tissues Primary tissues formed each year from primary meristems Secondary tissues develop during first and subsequent years from lateral meristems

Woody Stems Chapter 25 Structure and Organization of Plants Woody stems have no distinct vascular bundles, and instead have three distinct regions: ●Bark Wood Pith Vascular cambium occurs between the bark and the wood

Secondary Growth Chapter 25 Structure and Organization of Plants Secondary growth adds cells on either side of the vascular cambium: ● Secondary xylem – inner side ● Secondary phloem – outer side Each year new phloem is added to the outside of the trunk of a tree. This creates bark. Each year new xylem is added to the inside of the trunk of the tree. This creates wood.

Secondary Growth of Stems
Biology, 9th ed, Sylvia Mader Secondary Growth of Stems Chapter 25 Structure and Organization of Plants

Wood Chapter 25 Structure and Organization of Plants Wood is secondary xylem that builds up year after year In trees that have a growing season, vascular cambium is dormant during winter - In spring, when moisture is plentiful secondary xylem contains wide vessel elements with thin walls. - This creates the spring wood. - Later in season, moisture is scarce, vessels are small and are many thick-walled tracheids - This creates the summer wood.

Wood Chapter 25 Structure and Organization of Plants When the trunk of a tree has spring wood followed by summer wood, the two together make up one year’s growth, or an annual ring. You can tell the age of a tree by counting the annual rings. Two Types of Wood: The outer annual rings, where transport occurs, are called sapwood. In older trees, inner annual rings, heartwood, no longer function in water transport.

Bark Chapter 25 Structure and Organization of Plants Bark of a tree contains periderm (cork & cork cambium) and phloem. Phloem does not build up season to season like wood. Instead it dies and is shed over time. Bark can be removed, but it is harmful to the plant due to lack of organic nutrient transport Cork cells are impregnated with suberin, a waxy layer that makes them waterproof but causes them to die. This makes them harder and less edible & thus protects the tree.

Three-year-old Woody Twig
Biology, 9th ed, Sylvia Mader Three-year-old Woody Twig Chapter 25 Structure and Organization of Plants

Chapter 25 Tree Trunk Structure and Organization of Plants

Stem Diversity Chapter 25 Structure and Organization of Plants Stolons: Above-ground horizontal stems Produce new plants where nodes touch the ground. This is called vegetative reproduction. Example: strawberry plants Other Modifications: •Succulent stems on cacti store water •Stems that become tendrils to climb

Stem Diversity Chapter 25 Structure and Organization of Plants Rhizomes: Underground horizontal stems Contribute to asexual reproduction because each node bears a bud. Variations: Tubers - Enlarged portions functioning in food storage Example: potato eyes are buds Corms - Underground stems that produce new plants during the next season Example: gladiolus “bulbs”

Chapter 25 Stem Diversity Structure and Organization of Plants

Chapter 25 Leaf Structure Structure and Organization of Plants

Leaf Structure Chapter 25 Structure and Organization of Plants Parts of a leaf: •Epidermis •Outer waxy cuticle •Stomata & guard cells •Body of leaf composed of mesophyll tissue in two types: - palisade mesophyll - elongated cells - spongy mesophyll - irregular cells bounded by air spaces

Leaf Diversity Chapter 25 Structure and Organization of Plants Blade of a leaf can be simple or compound: • Simple leaf - single blade • Compound leaf - divided into leaflets - Pinnately compound leaves have leaflets occurring in pairs - Palmately compound leaves have all of the leaflets attached to a single point - Bipinnately compound leaves have leaflets subdivided into even smaller leaflets

Classification of Leaves
Biology, 9th ed, Sylvia Mader Chapter 25 Classification of Leaves Structure and Organization of Plants

Leaf Diversity Chapter 25 Structure and Organization of Plants Leaves can be arranged in stem in 3 ways: • Alternate • Opposite • Whorled Leaves are adapted to environmental conditions. Shade plants - broad, wide leaves Desert plants have reduced leaves, sunken stomata. Cactus spines are leaves.

Leaf Diversity Chapter 25 Structure and Organization of Plants Other specialized leaves: • Onion bulbs • Head of cabbage • Large petiole (celery & rhubarb) • Tendrils • Specialized for catching insects: - Sundews, Venus flytrap, pitcher plants - These plants commonly live in marshy regions with low supply of soil nitrogen.

Chapter 25 Leaf Diversity Structure and Organization of Plants Pitcher plant Sundew

Ch. 25 – Plant Structure & Organization

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