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Leaves (Morphology and Anatomy of Other Leaf Types (Leaves of Conifers…
Leaves
Morphology and Anatomy of Other Leaf Types
Spines
Protective tactic
To keep animals away
Mesophyll
Consists of closely packed fibers
Tendrils
Form of modified leaf
They grow indefinetely
Contain cells that can:
Sense contact with an object
Bud Scales
Evolutionary conversion
Role is protection
Form a tight layer around the stem tip
Small, compound
Wind damage is not a risk
Leaves of Conifers
Leaves are sclerophylls
Thick cuticle
Epidermis and hypodermis cells have thick walls
Simple, never compound
Leaves with Kranz Anatomy
Occurs in leaves that have C4 photosynthesis
Special metabolism
These leaves lack palisade & spongy
Sclerophyllous Foliage Leaves
Produce more sugars by photosynthesis more than used
Leaves tend to be:
Soft
Flexible
Edible
Insect Traps
Ability to trap & digest insects
Traps
Active
Move during captrue
Passive
Incapable of movement
Succulent Leaves
Thick and fleshy
Shape reduces surface-to-volume ratio
Favors water conservation
Internal Structure of Foliage Leaves
Vascular Tissues
Between palisade and spongy
Bundle sheath
Fibers arranged in a sheath
Bundle sheath extension
Larger bundle sheaths
Have a mass of fibers below or both
Mesophyll
Ground tissues interior to leaf epidermis
Palisade parenchyma
Upper surface of most leaves
Main photosynthetic tissue of most plants
Spongy mesophyll
Lower portion of the leaf
aerenchyma that permits CO2 to diffuse rapidly
Epidermis
Reasonably waterproof
Must allow entry of CO2
Transpiration
Water loss through the epidermis
Petiole
Tiny, but massive in certain plants
Transition between stem and lamina
Stipules
Serve many functions
Protect apical meristem when the leaf is young & small
Contribute photosynthesis
Die early
External Structure of Foliage Leaves
Must NOT lose excess amount of water
Leaf blade
Flat, light harvesting portion
Dorsal surface
Blade's lower side
Ventral surface
Upper side
Petiole
Stalk that holds blade out into light
Initiation and Development of leaves
Basal Angiosperms and Eudicots
Leaf primordium formed
Extends upward &grows rapidly
Consists of leaf protoderm & leaf ground meristem
As it grows upward
Increases in thickness
Monocots
Initiated by expansion of some shoot apical meristem cells
To form a leaf primordium
In some:
Lamina becomes broad & expanded
And others:
Have strap-shaped leaves that grow continuously
