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Leaves (Morphology and Anatomy of Other Leaf Types (Succulent Leave…
Leaves
Morphology and Anatomy of Other Leaf Types
Succulent Leave
Commonly found in desert habitats
Thick and fleshy
Very adaptive
A shape that reuces the surface-to-volume ratio
Favors water conservation
Typically cylindrical or spherical in shape
Contains very few air spaces inside the plant
Sclerophyllous Foliage Leaves
Must produce more sugars by photosynthesis
Limited amount of sclerenchyma
Most leaves are soft, flexible, and edible
More resistant to specific things
Animals
Fungi
Freezing temperatures
Ultraviolet light
Leaves of Conifers
Leaves are sclerophylls
Thick cuticle
Epidermis and hypodermis have thick cell walls
Leaves are always simple
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Never compound leaves
Needles
Occur in
All firs
All pines
All spruces
Either short or long
Bud Scales
In perennial plants
dormant shoot apical meristem protected
From low temperatures
drying action of the wind during winter
Primary role is protection
Not photosynthesis
Small and rarely compound
Petiole is short or absent
Produce a thin layer of corky bark
On exposed portions
greater protection than simple epidermis
Spines
Cacti
Two types of leaves
Green cactus body
Clusters of spines
Modified leaves of axillary buds
No mesophyll parenchyma or vascular tissue
Photosynthesis occurs in stem cortex
Tendrils
Can be found on
Peas
Cucumbers
Squash
Another form of modified leaf
Grow indefinitely
cells are capable of sensing contact with object
Vines
Leaves with Kranz Anatomy
Distinct in C4 metabolism
Photosynthesis
Lack palisade parenchyma
Lack spongy mesophyll
Have prominent bundle sheaths
Ring of mesophyll surrounds each sheath
Large chlorophyll cells
Insect Traps
Passive Trap
incapable of movement
Pitcher leaves of
Nepenthes
Active Trap
Move during capture
Leaves of sundew (
Drosera
)
Habitats with poor nitrates and ammonia
External Structures of Foliage Leaves
Simple leaf
Blade of just one part
Numerous shapes
Some may be deeply lobed
Compound leaf
Blade divided into several individual parts
Sessile leaf
When leaves are small or very long and narrow
Do not self-shade
Instead of petiolate
Abscission zone
Found in the petiole
oriented perpendicular to petiole
Cells involved in cutting off the leaf when life is over
Petiole
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Also known as stalk
holds the blade out into the light
Prevents shading of lead blades by those above
Vein
bundles of vascular tissue
Reticulate venation
In basal angiosperms
In eudicots
Netted pattern
Parallel venation
In monocots
With long, strap-shaped leaves
Larger veins run side by side
Few obvious interconnections
Distribute water from the stem to leaf
Collect sugars produced by photosynthesis
Leaf blade
Dorsal Surface
Also known as abaxial side
Lower side
Ventral surface
Also known as adaxial
Upperside
Flat, light-harvesting portion
In a thick layer of chlorenchyma
Internal Structure of Foliage Leaves
Epidermis
Flat, thin foliage leaves
Large surface area where water can be lost
Optimal for light interception
Transpiration
Water loss through the epidermis
is a serious problem
Skin
Waterproofing due to keratin
Simultaneously translucent
Allow entry of CO2
Mesophyll
Palisade parenchyma
Also known as Palisade Mesophyll
Along upper surface of most leaves
Main photosynthetic tissue of plant cells
Separated slight
Each cell have most surface exposure
To intercellular space
Spongy mesophyll
Lower portion of the leaf
open, loose aerenchyma
permits CO2 to diffuse
Rapidly from stomata to interior parts of plant
Vascular Tissues
Bundle sheath
Around vascular tissues
Difficult for insects to chew into vascular tissue
Many fibers arranged as sheaths
Function as support
Bundle sheath extension
Located above, below, or in both places in the veins
Rigidity
Additional means of water transportation
Eudicot leaf
Mid rib
Also known as Midvein
Conduction
Minor veins
Emerge from midrib/lateral vein
Narrow
Most important for releasing water
From xylem
loading sugar into phloem
Lateral veins
Conduction
contain both primary xylem and primary phloem
Xylem on upper side
Phloem on lower side
Emerges from the Midrib
Petiole
Stipules
Two small flaps of tissue at base
Serve various functions
Protect shoot apical meristem in young
If large may contribute large amount of photosynthesis
Leaf traces
Occur in 1,3,5 or more vascular bundles
branch from stem vascular bundles
diverge towards the petiole
Part of leaf
Transition between stem and lamina
Massive in stalky plants
Concepts
Different types of of leaves have different purposes
Leaves are apart of the shoot system
Most commonly known as foliage
Involved in photosynthesis
Initiation and Development of Leaves
Basal Angiosperms and Eudicots
Leaf primordium
Cells just interior to protoderm
Grow outwards
Form a protrusion
Extends upward as narrow cone
Growing so fast it out grows shoot apical meristem
Leaves produced only through activity of shoot
Eudicot
Initiated by expansion
Monocots
Initiated by expansion
Can be a compound leaf
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Rubbery leaf formation
Protected
Leaves of conifers are simple never compound
Petiole occurs in the Internal and external plant
Monocot can be compound leaf
