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Chapter 6: Leaves, Cross Connection: Both Initiated by Expansion of Shoot…
Chapter 6: Leaves
Morphology and Anatomy of Other Leaf Types
Serphyllous Foliage Leaves
Sclerenchyma Present Below Epidermis
More Resistant
Cuticle Usually Very Thick
Succulent Leaves
Thick and Fleshy
Reduces the Surface-to-Volume ratio
Favors Water Conservation
Reduced Capacity for Carbon Dioxide Uptake
Mesophyll Contain Very Few Spaces
Photosynthesis Occurs More Deeply
Leaves of Conifers
Sclerophylls
Thick Cuticle
Thick Cell Walls in
Epidermis
Hypodermis
Always Simple
Forms
Needles
Scale-like Leaves
Mostly Perennial
Bud Scales
Primarily Protection
Form Tight Layer Around Stem Tip
Small and Rarely Compound
Petiole Short or Absent
Frequently Produce Thin Layer of Corky Wax
Spines
Modified Leaves of Axillary Buds
Protective
No blade
Needle Shaped
Not Present
Vascular Tissue
Mesophyll Parenchyma
Inhibit Lamina Formation
Mesophyll Consists of Tightly Packed Fibers
Deposit Lignin On Walls
Cells Die and Dry Out
Hard and Resistant to Decay
Tendrils
Grow Indefinitely
Contain Cells That Can Sense Contact
Side That Touches Object Stops Growing
No Lamina
Leaves with Kranz Anatomy
Occurs in C4 Plants
Lack
Palisade Parenchyma
Spongy Mesophyll
Contain Prominent Bundle Sheaths
Composed of Large Chlorophyllous Cells
Surrounded by Ring of Mesophyll
Insect Traps
Ability to Trap and Digest Insects
Trap Leaves Can Be Classified As
Active Traps
Trichomes Secrete Sticky Digestive Liquid
Blade Curls Around Insect
Trigger Hairs Control Motor Cells
Passive Traps
Lamina is Tubular and Secretes Digestive Fluid
Epidermis is Permeable
Throat of Pitcher Contain Numerous Trichomes
Concepts
Numerous Types of Leaves
Selectively Advantageous Modifications
Stems and Leaves Must Work Together
Foliage Leaves Most Familiar
Internal Structure of Foliage Leaves
Epidermis
Water Loss is Through This Called Transpiration
Must Be
Reasonably Waterproof
Translucent
Able to Allow Entry Of Carbon Dioxide
Contain
Epidermal Cells
Guard Cells
Trichomes
Coating of Cutin
Usually Wax
Upper and Lower Portions
Vascular Tissue
Between Palisade Parenchyma and Spongy Mesophyll
Eudicot
Usually One Large Mid-rib or Midvein
Lateral Veins Emerge From Midvein
Lateral Veins Branch Into Minor Veins
Bundle Sheath
Fiber Arranged As Sheath Around Vascular Tissue
Bundle Sheath Extensions
Mass of Fibers Above and or Below Veins
Help Give Rigidity To The Blade
Mesophyll
Ground Tissues Interior to Epidermis
Palisade Parenchyma
Along Upper Surface of Most Leaves
Main Photosynthetic Tissue in Most Plants
Separated Slightly
Spongy Mesophyll
Open, Lose Aerenchyma
Allows Rapid Diffusion Of Carbon Dioxide
Petiole
Considered Part of Leaf
Transition Between Stem and Lamina
Leaf Traces
Vascular Tissues
Branch From Stem Vascular Bundles
Diverge Toward Petiole
Stipules
Two Small Flaps of Tissue at Base
May Protect Shoot Apical Meristem
External Structure of Foliage Leaves
Functions
Photosynthesis
Waterproof
Pathogen Resistance
Leaf Blade
#
AKA Lamina
Flat, Light Harvesting Portion
Lower Side
Dorsal Surface
Abaxial Side
Larger Veins
Upper Side
Ventral Surface
Adaxial Side
Usually Smooth
Simple
#
Has a Blade of Just One Part
Compound
Blade Divided Into Several Parts
Many Small Blades (Leaflets)
Leaflets Attached by Petiolule
Leaflets Attached to Rachis
Veins
Bundles of Vascular Tissues
Distribute Water From Stem to Leaves
Carry Sugars From Leaves to Stem
Patterns
Reticulate Venation
Netted Pattern
In Basal Angiosperms and Eudicots
Parallel Venation
Veins Run Side by Side
In Monocots with Long Star-Shaped Leaves
Abscission Zone
At Leaf Base
Usually in Petiole
Perpendicular to Petiole
Involved in Cutting Off Leaves That Aren't Useful
Creates Leaf Scar
Petiole
Hold Leaf Blade in Light
Prevents Shading From Other Leaf Blades
In Absence Leaf is Called Sessile Leaf
Leaf is called Petiolate
Sheathing Leaf Base Can Take Place of Petiole
Initiation and Development of Leaves
Basal Angiosperms and Eudicots
Leaf Primordium
At Base of Meristem
Consists of
Leaf Protoderm
Leaf Ground Meristem
Grows Upward and Increases Thickness
Establishes Bulk of Mid-rib
Row of Cells Grow Outward
Initiates Lamina
Lamina Expansion
Differentiation of
Stomata
Trichomes
Vascular Bundles
Petiole Becomes Distinct From Mid-rib
Monocots
#
Leaf Primordium
Adjacent Apical Meristem Cells
Grow Upward
Become Part of Primordium
Give a Hood-Like Shape
Becomes a Cylinder
Encircles Shoot Apical Meristem
Grows Upward As Sheathing Leaf Base
Original Conical Primordium Gives Rise To Lamina
Outer Surface Is Abaxial Epidermis
Inner Surface is Adaxial Epidermis
Lamina
Some Become Broad and Expanded
Some Are Linear, Strap-Shaped
Grows by Meristem
Meristematic Cells Remain Active Mitotically
Basal Expansion
Protoxylem and Protophloem Constantly Stretched and Disrupted
Rapid Differentiation of
Vessel Elements
Sieve Tube Members
Region Above Basal Meristem
Tissues Differentiate
Initiates
Primary Xylem
Primary Phloem
Stomata
Other Features
Even Higher Above
Tissues Mature
Cross Connection: Both Initiated by Expansion of Shoot Apical Meristem Cells
Cross Connection: Conifer Leaves Are Always Simple Leaves
Cross Connection: Leave Blade is Absent in Spines
