Exercise 6 Leaves

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Exercise 6 Leaves
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Introductory Notes

• (copy these notes on your exercise)
• Leaves are the major food making parts of plants
  but they can be used for many other purposes.
• Tree leaves come in a wide variety of shapes and
  sizes and can be used to identify the tree.

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Skip to page 56

• Internal Structure of Leaves

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Internal Structure of LeavesDicot

• Highlight or underline 3 major tissue types
  present epidermis (upper lower) mesophyll
  veins.
• Answer question 1.

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Use this diagram to answer questions 2,3,45.
Chloroplasts
Photosynthesis
Air space
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Answer question 6
Mid rib
Xylem
Phloem
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Cuticle
U. Epidermis
Palisade Mesophyll
Stoma
Spongy Mesophyll
L. Epidermis
Air Space
Guard Cells
Figure 6.7
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Internal StructureMonocot Leaf

• Highlight or underline
• The epidermis contains enlarged bulliform cells.
  It is thought that these cells lose water more
  rapidlycauses the leaf to curl during dry
  conditions, possibly preventing excessive water
  loss.
• Answer question 7.

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Bulliform cells
Bundle sheath extension
U. Epidermis
Mesophyll
L. Epidermis
Figure 6.8
Xylem
Phloem
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Leaf Modifications

• Highlight or underline plants that grow in
  neither dry or wet environments are mesophytes.
  Plants that grow in arid conditions are
  xerophytes, while plants that grow in water are
  hydrophytes.

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Xerophyte Features

• Highlight or underline the top of the leaf has
  a very thick cuticle.
• Larger cells comprise the hypodermis a water
  storing tissue
• Guard cells and stomata are located only on the
  lower surface and are sunken in stomatal crypts

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Figure 6.9
Cuticle
Upper Epidermis
Hypodermis
Palisade mesophyll
Spongy mesophyll
Stomatal Crypt
Lower Epidermis
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Hydrophyte Features

• Highlight or underline stomata located only in
  the upper epidermis. There is no cuticle and the
  epidermal cells are thin walled.
• Answer question 8

Air spaces
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Figure 6.10
Upper epidermis
Palisade Mesophyll
Spongy Mesophyll
Air chambers
Astrosclereids
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Nerium oleander
Answer questions 9 10
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Leaf Abscission

• Highlight or underline
• most woody dicots in temperate regions produce
  new leaves each spring and lose them in the fall.
  Leaf fall is associated with the development of a
  special layer called the abscission zone.
• This layer has two layers. The separation layer
  has parenchyma cells that are easily broken.
• The cork layer protects against water loss when
  the leaf falls off

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Figure 6.12
Lateral bud
Leaf petiole
Separation layer
Cork layer of Abscission layer
Bundle scar (developing
Vein
Pith
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Stop

• This concludes this portion Exercise 6

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External Morphology of Leaves

• Highlight or underline
• Leaves of plants show considerable variation in
  form, size, structure and arrangement on the
  twig.
• This leaf consists of a broad flat blade, a leaf
  stalk or petiole, and a pair of small leaf like
  structures stipules found at the base.

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External Morphology of Leaves

• Highlight or underline
• A leaf having all three of these structures is
  said to be complete.
• If one or more is missing the leaf is incomplete.

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Figure 6.1 Make a Diagram and Label
Blade
Petiole
Stipule
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Leaf Venation

• Highlight or underline
• Monocots characteristically have a venation
  pattern parallel to each other.

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Figure 6.2 Monocot Leaf
Veins
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Highlight or underline

• Dicots Have Netted Venation- two variations may
  be found
• Pinnate venation one main vein with lateral veins
  branching from it
• Palmate venation have several main veins from one
  single point (like a hand)

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Types of Leaves

• Highlight or underline
• Leaves may be categorized by the type of leaf
  blade. A single leaf blade is simple, if it is
  separated into several smaller units it is
  compound. Each unit is a leaflet.

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Types of Leaves
Types of Leaves

• Highlight or underline
• Palmately compound leaves have all leaflets
  arising from a common point
• Pinnately compound leaves have leaflets arising
  at intervals along a main axis or rachis-an
  extension of the petiole

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Types of Leaves

• Look at the next slides sketch and label as
  simple or compound and pinnate or palmate under
  the sketch

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Pinnate Veins
Pinnate Veins
Simple
Compound
Figure 6.3
Figure 6.4
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Palmate Veins
Palmate Veins
Compound
Simple
Figure 6.6
Figure 6.5
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Carnivorous Plants
Highlight or underline Among the most
interesting leaf adaptations are those of
carnivorous plants. These include the pitcher
plant and Venuss fly trap
Venuss Flytrap
Pitcher plant
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Bladder
Highlight or underline A less known plant with
this adaptation is the bladderwort. Draw and
label 6.11
Bladderwort
Figure 6.11
Sensitive Hairs
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Questions

• Answer questions on page 61

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Leaflet no stipule or thick petiole base
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Monocot no palisade layer
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Xerophytes

• Very thick cuticle
• Thick epidermis
• Sunken stomata

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Monocot/Dicot Roots
ClueNote location of vascular tissue and pith in
each
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Monocot/Dicot Stems


ClueNote location of vascular tissue and pith in
each
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Monocot/Dicot Leaves
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The End
Created by R.E. Lynn