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Chapter focus Plant structure and growth Warning – many terms or vocabulary words Warning – many diagrams Focus – structure, function, located next to …. Question ? What heading can be given to the following groups of words? --------Lettuce Peas Beans ---------Rhubarb Apples Oranges Question ? What is a vegetable? What is a fruit? Vegetables Lettuce Rhubarb Fruits Peas Beans Apples Oranges Point Plants have organs too, just like animals. Asexual organs (vegetables) Sexual organs (fruits) Asexual Organs 1. Stem 2. Leaf 3. Root Stem The main body of the portion above ground of a tree, shrub or herb. The ascending plant axis. Stem Functions Support of other plant organs. Ps. Storage (water and food). Leaf Lateral outgrowths of the stem axis. Primary photosynthetic organs. Function: Photosynthesis Storage Root The descending axis of a plant, normally below ground. Functions: Anchorage. Absorption Storage. of water and minerals. Sexual Organs 1. Flowers 2. Fruits 3. Seeds Flowers Modified leaves grouped together on a stem. Sexual reproductive organs. Function: Sexual Reproduction Fruit A mature ovary, sometimes including other floral parts. Function: Seed dispersal Seed protection Seed Mature ovule containing the embryo and nutrient tissues. Function: Dispersal unit in sexual reproduction. Plant Cell Types Differentiated by the type and thickness of the cell wall. 1. Parenchyma (soft tissue) 2. Collenchyma (glue tissue) 3. Sclerenchyma (hard tissue) Parenchyma Cells Primary wall only. Thin cell wall. Alive when mature, “typical" plant cell. Functions Ps Storage "Filler" cells Cell division (mitosis) Collenchyma Primary wall only. Wall is thickened, especially in the corners. Alive when mature. Function Support of non-woody plant parts. Ex: veins, stems. Sclerenchyma Secondary wall present. Wall strengthened with lignin. Dead when mature. Sclerenchyma Types 1. Fibers 2. Sclereids 3. Tracheids 4. Vessel Elements Fibers Elongated thin cells used for support. Ex: Hemp fibers Sclereids Used for hard dense areas and support. Ex: Nut shells, seed coats Tracheids Spindle shaped cells with pits in the cell walls. Used for water transportation. Vessel Fiber Vessel Elements Wide stocky cells with pits in the side walls; lack end walls. Used for water transportation. Plant Tissues Can be named by several methods: Ex: Cell Location Cell Origin Cell Function Point The same cell can have several tissue names depending on the criteria for naming. Main Tissue Systems 1. Dermal 2. Vascular 3. Ground Dermal Tissue Epidermis or "skin" of the plant. Often has a cuticle, a waxy coating to prevent water loss. Functions: Prevent water loss. Water absorption (root hairs). Vascular Tissue Made of Xylem and Phloem. Functions: Transport and support Xylem - Water Phloem - Food Xylem Phloem Phloem Cell – alive when functioning, but lacks a nucleus. Companion Cell – alive, controls itself and the sieve cell. Sieve Ground Tissue Tissue between the dermal and the vascular tissues. Functions: "Filler" tissue Ps storage support Question ? How does plant growth and animal growth differ ? Animals Whole organism increases in size. Determinant Growth: grow to a certain size, then stop. Plants Growth in specialized areas only. Indeterminant Growth: grow as long as they live because the specialized areas remain embryonic. Plant Meristems Perpetual embryonic regions. Zones for cell division. Meristem Types 1. Apical growth in length. Primary growth. 2. Lateral/Cambiums growth in diameter. Secondary growth. Comment Some tissues like Xylem may be Primary or Secondary depending on which meristem produced the cell. Ex: Primary xylem Secondary xylem Apical Meristem Types 1. RAM – Root Apical Meristem: primary growth of roots. 2. SAM – Shoot Apical Meristem: primary growth of shoots. RAM Located at the tip of each growing root. Protected from the soil by the Root Cap. RAM Root Cap Protects RAM. Secrets a polysaccharide lubricant for root growth. Primary Root Zones 1. Cell Division - cells small and embryonic. 2. Cell Elongation - cells elongate and start to mature. 3. Cell Differentiation - cells mature into final cell types. Root Hairs Extensions of the epidermis to increase surface area for water absorption. Not a true tissue. Comment - root hairs are very delicate and must be continually replaced. Root Hairs RAM - Primary Tissues 1. Protoderm 2. Procambium 3. Ground Meristem Protoderm Will mature into the epidermis and root hairs. Procambium Stele Matures into the vascular tissues of the stele: Xylem Phloem Pericycle – site of branch roots Ground Meristem Matures into the ground tissues: – storage tissue Endodermis – second skin around the stele that controls the movement of materials into the stele. Cortex Epidermis Cortex Stele Endodermis Pericycle Xylem Phloem Branch Roots Originate from the pericycle. Burst their way to the outside. Root Types Taproot Ex: - one main root. carrot Fibrous Roots - many small roots of equal size. Ex: grass roots Adventitious Roots Roots that develop from other plant parts. Ex: roots on stem cuttings climbing roots SAM Produces 1. Protoderm 2. Procambium 3. Ground Meristem Comment – these tissues mature into the same things as seen in RAM. SAM Differences No "root" cap. Produces leaves as stem out-growths at the nodes. Has buds. Buds Apical Meristems protected by modified leaves or bud scales. Axillary Buds Branch Stems Develop from axillary meristems or axillary buds. "External" development. Modified Stems 1. Rhizomes 2. Stolons 3. Tubers 4. Tendrils Rhizome An elongated underground horizontal stem. Ex: Iris, many grasses Stolon An elongated above-ground horizontal stem. Ex: Strawberries Airplane Plant Tuber A muchenlarged, short, fleshy underground stem tip. Ex: Dahlia, Potato Tendril A slender coiling stem. Ex: Clematis and other climbing vines. Leaves Stem outgrowths for Ps. Leaf Morphology: 1. Gross 2. Fine Gross Morphology Blade - the flattened portion of a leaf. Petiole - stalk of a leaf. Axillary Buds Blade Petiole Blade/Leaf Types Simple - 1 blade. Compound - Several blades. Nodes and Internodes Node - stem area where a leaf and bud are attached. Internode - stem area between nodes. Nodes } Internode Fine Morphology The tissues within a leaf. 1. Upper Epidermis 2. Mesophyll 3. Lower Epidermis 4. Veins Upper Epidermis Cuticle present. Usually 1 cell layer thick. Cells w/o chloroplasts . Function: protects the mesophyll. Mesophyll 1. Palisade upright cells. 2. Spongy loosely organized cells with air spaces. Function: major sites for Ps. Epidermis Epidermis Lower Epidermis Cuticle present. Usually 1 cell layer. Cells w/o chloroplasts. Stomata present for gas exchange. Stomata (mouth) Regulated by Guard Cells which have chloroplasts. Vein Structure Xylem: dorsal Phloem: ventral Often surrounded by bundle sheath cells for support. Xylem Phloem Bundle Sheath Cells Collenchyma Homework Read Chapter 35, 37 No lab broadcast 3/27 Chapter 35 – Fri. 3/28 Leaf Modifications 1. Tendrils: for support Ex: Peas 2. Bulbs: for food storage Ex: Onion 3. Insect Catching Ex: Carnivorous Plants 4. Flowers: thought to be modified leaves. Other Modifications of Leaves Tendrils Succulent Leaves Spines Bracts Stem Vascular Tissue – vascular bundles join together to make a ring. Often have secondary growth. Monocots – vascular bundles are scattered. No true secondary growth. Dicots Secondary Growth Growth in diameter. Growth from lateral meristems or cambiums. Cambium Types 1. Vascular – produces xylem and phloem. 2. Cork – produces “cork”. Vascular Cambium Location: between primary xylem and phloem. Produces: secondary xylem and phloem. Fibers Phloem Vascular Cambium Xylem Fibers Vascular Cambium: Cell Maturation xylem External phloem The VC pushes the xylem and phloem apart from each other. Internal Result Newest xylem is next to the cambium. Oldest xylem is in the center of stem. Result Newest phloem is next to cambium. Oldest phloem is under the epidermis. Result Xylem accumulates over time. Phloem is destroyed by the outward growth and must be replaced yearly. Cork Cambium Location: Cortex (external to the VC). Produces: Cork Comment – commercial cork is harvested from a Cork Oak. Cork Cells Produced "outwardly" only. Covered with suberin and are dead when mature. Function – insulation and protection. Epidermis Cork Cambium Cortex Phloem Vascular Cambium Xylem Fibers Bark All tissues external to the VC. Includes: Phloem (1 degree and 2 degree) Cork Cortex Epidermis Fiber cells Wood Xylem tissue of a dicot stem. Comment – monocots don’t have VC and technically don’t produce true “wood”. Xylem Growth Springwood - Large cells Rapid growth Summerwood - Small cells Slow growth Annual Rings Formed by the growth difference between springwood and summerwood. Usually one produced per year. Comment Ring size varies by climate and growing conditions. Rings can be used to date wooden structures. Summer Wood Spring Wood One Year’s Growth Angiosperms Divided into two main types: 1. Dicotyledons or Dicots 2. Monocotyledons or Monocots Cotyledons = seed leaves Monocots vs. Dicots 1. Seeds and embryos 2. Leaves 3. Stems 4. Roots 5. Flowers Seeds and Embryos Dicots - no endosperm. - 2 cotyledons. Monocots - endosperm - 1 cotyledon Leaves – netted veins. Monocots - parallel veins. Dicots Stems Dicots - ring pattern - vascular cambium Monocots - scattered pattern - no vascular cambium Roots Dicots - taproot. - xylem centermost tissue. Monocots - fibrous roots. - pith centermost tissue. Flowers – parts in 4's or 5's. Monocots – parts in 3's. Dicots Summary Know the main organs of plants and their functions. Know the main cell types or tissues in plants and their functions. Summary Know the structural organization of stems, roots, and leaves. Know the differences between dicots and monocots.