Plant Structure and Growth

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Chapter 35 Plant Structure and Growth
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Question ?

• What heading can be given to the following groups
  of words?

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• ---------
• Lettuce
• Peas
• Beans

• ----------
• Rhubarb
• Apples
• Oranges

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Question ?

• What is a vegetable?
• What is a fruit?

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• Vegetables
• Lettuce
• Rhubarb

• Fruits
• Peas
• Beans
• Apples
• Oranges

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Point

• Plants have organs too, just like animals.
• Asexual organs (vegetables)
• Sexual organs (fruits)

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Asexual Organs

• 1. Stem
• 2. Leaf
• 3. Root

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Stem

• The main body of the portion above ground of a
  tree, shrub or herb.
• The ascending plant axis.

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Stem Functions

• Support of other plant organs.
• Ps.
• Storage (water and food).

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Leaf

• Lateral outgrowths of the stem axis.
• Primary photosynthetic organs.
• Function
• Photosynthesis
• Storage

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Root

• The descending axis of a plant, normally below
  ground.
• Functions
• Anchorage.
• Absorption of water and minerals.
• Storage.

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Sexual Organs

• 1. Flowers
• 2. Fruits
• 3. Seeds

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Flowers

• Modified leaves grouped together on a stem.
• Sexual reproductive organs.
• Function
• Sexual Reproduction

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Fruit

• A mature ovary, sometimes including other floral
  parts.
• Function
• Seed dispersal
• Seed protection

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Seed

• Mature ovule containing the embryo and nutrient
  tissues.
• Function
• Dispersal unit in sexual reproduction.

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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)

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Parenchyma Cells

• Primary wall only.
• Thin cell wall.
• Alive when mature,
• typical" plant cell.

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Functions

• Ps
• Storage
• "Filler" cells
• Cell division (mitosis)

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Collenchyma

• Primary wall only.
• Wall is thickened, especially in the corners.
• Alive when mature.

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Function

• Support of non-woody plant parts.
• Ex veins, stems.

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Sclerenchyma

• Secondary wall present.
• Wall strengthened with lignin.
• Dead when mature.

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Sclerenchyma Types

• 1. Fibers
• 2. Sclereids
• 3. Tracheids
• 4. Vessel Elements

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Fibers

• Elongated thin cells used for support.
• Ex Hemp fibers

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Sclereids

• Used for hard dense areas and support.
• Ex Nut shells, seed coats

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Tracheids

• Spindle - shaped cells with pits in the cell
  walls.
• Used for water transportation.

Vessel
Fiber
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Vessel Elements

• Wide stocky cells with pits in the side walls
  lack end walls.
• Used for water transportation.

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Plant Tissues

• Can be named by several methods
• Ex Cell Location Cell Origin
  Cell Function

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Point

• The same cell can have several tissue names
  depending on the criteria for naming.

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Main Tissue Systems

• 1. Dermal
• 2. Vascular
• 3. Ground

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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).

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Vascular Tissue

• Made of Xylem and Phloem.
• Functions
• Transport and support
• Xylem - Water
• Phloem - Food

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Xylem
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Phloem
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Phloem

• Sieve Cell alive when functioning, but lacks a
  nucleus.
• Companion Cell alive, controls itself and the
  sieve cell.

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Ground Tissue

• Tissue between the dermal and the vascular
  tissues.
• Functions
• "Filler" tissue
• Ps
• storage
• support

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Question ?

• How does plant growth and animal growth differ ?

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Animals

• Whole organism increases in size.
• Determinant Growth grow to a certain size, then
  stop.

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Plants

• Growth in specialized areas only.
• Indeterminant Growth grow as long as they live
  because the specialized areas remain embryonic.

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Plant Meristems

• Perpetual embryonic regions.
• Zones for cell division.

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Meristem Types

• 1. Apical growth in length. Primary growth.
• 2. Lateral/Cambiums growth in diameter. Secondary
  growth.

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Comment

• Some tissues like Xylem may be Primary or
  Secondary depending on which meristem produced
  the cell.
• Ex
• Primary xylem
• Secondary xylem

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Apical Meristem Types

• 1. RAM Root Apical Meristem primary growth of
  roots.
• 2. SAM Shoot Apical Meristem primary growth of
  shoots.

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RAM

• Located at the tip of each growing root.
• Protected from the soil by the Root Cap.

RAM
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Root Cap

• Protects RAM.
• Secrets a polysaccharide lubricant for root
  growth.

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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.

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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.

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Root Hairs
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RAM - Primary Tissues

• 1. Protoderm
• 2. Procambium
• 3. Ground Meristem

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Protoderm

• Will mature into the epidermis and root hairs.

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Procambium Stele

• Matures into the vascular tissues of the stele
• Xylem
• Phloem
• Pericycle site of branch roots

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Ground Meristem

• Matures into the ground tissues
• Cortex storage tissue
• Endodermis second skin around the stele that
  controls the movement of materials into the
  stele.

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Epidermis
Cortex
Stele
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Endodermis
Pericycle
Xylem
Phloem
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Branch Roots

• Originate from the pericycle.
• Burst their way to the outside.

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Root Types

• Taproot - one main root.
• Ex carrot
• Fibrous Roots - many small roots of equal size.
• Ex grass roots

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Adventitious Roots

• Roots that develop from other plant parts.
• Ex roots on stem cuttings climbing roots

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SAM Produces

• 1. Protoderm
• 2. Procambium
• 3. Ground Meristem
• Comment these tissues mature into the same
  things as seen in RAM.

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SAM Differences

• No "root" cap.
• Produces leaves as stem out-growths at the
  nodes.
• Has buds.

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Buds

• Apical Meristems protected by modified leaves
  or bud scales.
• Axillary Buds

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Branch Stems

• Develop from axillary meristems or axillary buds.
• "External" development.

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Modified Stems

• 1. Rhizomes
• 2. Stolons
• 3. Tubers
• 4. Tendrils

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Rhizome

• An elongated underground horizontal stem.
• Ex Iris, many grasses

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Stolon

• An elongated above-ground horizontal stem.
• Ex Strawberries Airplane Plant

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Tuber

• A much-enlarged, short, fleshy underground stem
  tip.
• Ex Dahlia, Potato

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Tendril

• A slender coiling stem.
• Ex Clematis and other climbing vines.

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Leaves

• Stem outgrowths for Ps.
• Leaf Morphology
• 1. Gross
• 2. Fine

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Gross Morphology

• Blade - the flattened portion of a leaf.
• Petiole - stalk of a leaf.

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Axillary Buds
Blade
Petiole
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Blade/Leaf Types

• Simple - 1 blade.
• Compound - Several blades.

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Nodes and Internodes

• Node - stem area where a leaf and bud are
  attached.
• Internode - stem area between nodes.

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Nodes

Internode
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Fine Morphology

• The tissues within a leaf.
• 1. Upper Epidermis
• 2. Mesophyll
• 3. Lower Epidermis
• 4. Veins

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Upper Epidermis

• Cuticle present.
• Usually 1 cell layer thick.
• Cells w/o chloroplasts .
• Function protects the mesophyll.

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Mesophyll

• 1. Palisade upright cells.
• 2. Spongy loosely organized cells with air
  spaces.
• Function major sites for Ps.

Epidermis
Epidermis
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Lower Epidermis

• Cuticle present.
• Usually 1 cell layer.
• Cells w/o chloroplasts.
• Stomata present for gas exchange.

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Stomata (mouth)

• Regulated by Guard Cells which have chloroplasts.

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Vein Structure

• Xylem dorsal
• Phloem ventral
• Often surrounded by bundle sheath cells for
  support.

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Xylem
Phloem
Bundle Sheath Cells
Collenchyma
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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.

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Other Modifications of Leaves
Tendrils
Spines
Succulent Leaves
Bracts
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Stem Vascular Tissue

• Dicots vascular bundles join together to make a
  ring. Often have secondary growth.
• Monocots vascular bundles are scattered. No
  true secondary growth.

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Secondary Growth

• Growth in diameter.
• Growth from lateral meristems or cambiums.

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Cambium Types

• 1. Vascular produces xylem and phloem.
• 2. Cork produces cork.

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Vascular Cambium

• Location between primary xylem and phloem.
• Produces secondary xylem and phloem.

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Fibers
Phloem
Vascular Cambium
Xylem
Fibers
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Vascular Cambium Cell Maturation

• Internal ? xylem
• External ? phloem
• The VC pushes the xylem and phloem apart from
  each other.

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Result

• Newest xylem is next to the cambium.
• Oldest xylem is in the center of stem.

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Result

• Newest phloem is next to cambium.
• Oldest phloem is under the epidermis.

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Result

• Xylem accumulates over time.
• Phloem is destroyed by the outward growth and
  must be replaced yearly.

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Cork Cambium

• Location Cortex (external to the VC).
• Produces Cork
• Comment commercial cork is harvested from a
  Cork Oak.

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Cork Cells

• Produced "outwardly" only.
• Covered with suberin and are dead when mature.
• Function insulation and protection.

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Epidermis
Cork Cambium
Fibers
Cortex
Phloem
Vascular Cambium
Xylem
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Bark

• All tissues external to the VC.
• Includes
• Phloem (1 degree and 2 degree)
• Cork
• Cortex
• Epidermis
• Fiber cells

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Wood

• Xylem tissue of a dicot stem.
• Comment monocots dont have VC and technically
  dont produce true wood.

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Xylem Growth

• Springwood - Large cells
  Rapid growth
• Summerwood - Small cells
  Slow growth

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Annual Rings

• Formed by the growth difference between
  springwood and summerwood.
• Usually one produced per year.

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Comment

• Ring size varies by climate and growing
  conditions.
• Rings can be used to date wooden structures.

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Summer Wood
Spring Wood
One Years Growth
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Angiosperms

• Divided into two main types
• 1. Dicotyledons or Dicots
• 2. Monocotyledons or Monocots
• Cotyledons seed leaves

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Monocots vs. Dicots

• 1. Seeds and embryos
• 2. Leaves
• 3. Stems
• 4. Roots
• 5. Flowers

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Seeds and Embryos

• Dicots - no endosperm. - 2
  cotyledons.
• Monocots - endosperm - 1
  cotyledon

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Leaves

• Dicots netted veins.
• Monocots - parallel veins.

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Stems

• Dicots - ring pattern - vascular
  cambium
• Monocots - scattered pattern -
  no vascular cambium

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Roots

• Dicots - taproot. -
  xylem centermost tissue.
• Monocots - fibrous roots.
  - pith centermost tissue.

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Flowers

• Dicots parts in 4's or 5's.
• Monocots parts in 3's.

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Summary

• Know the main organs of plants and their
  functions.
• Know the main cell types or tissues in plants and
  their functions.

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Summary

• Know the structural organization of stems, roots,
  and leaves.
• Know the differences between dicots and monocots.