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Leaves (External Structure of Foliage Leaves (Compound leaf (several…
Leaves
External Structure of Foliage Leaves
Compound leaf (several parts)
Leaflets
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Petiolules on each leaflet
Petiolules attached to Rachis
Palmate
Attached at individual points
Pinnate
Attached at same point
Arranged in 2 rows
Simple leaf (one leaf)
No leaflets
Numerous leaf shapes
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Cordiform
Hastiform
Peltiform
Sagittiform
Sessile leaf (lacks petiole)
Petiolate (has petiole)
Abscision zone
Veins
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Parallel venation
Reticulate venation
Morphology and Anatomy
Succulent leaves
Thick and fleshy
Favor H2O conservation
No air spaces
Sclerophyllous leaves
Produce sugar by photosynthesis
Soft, flexible, edible
Sclerenchyma makes leaves resistant
Bud Scales
Protection
Spines
Modified axillary buds
Provide protection
Decay resistant
Tendrils
Provide support
Maximize photosynthesis
Insect traps
Digest insects
Evolved in plants
Poor soil quality
Internal Structure of Foliage
Vascular tissues
Lateral veins
Conduction
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Primary xylem upper side
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Primary phloem lower isde
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Support leaf blade
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Mid-rib
Minor veins
Release H2O from xylem
Load sugar into phloem
Mesophyll
Palisade parenchyma
Main photosynthetic tissue
Intercellular spaces
Occurs along upper surface
Spongy mesophyll
Loose aerenchyma
Occurs in the center
Petiole
Transition between stem and lamina
Epidermis contains few stomata
Petiole mesophyll like cortex
Leaf traces
Can remain distinct
Fuse into single trace
Vascular bundles
Plate
Ring
Stipules
Protect shoot apical meristem
Epidermis
Transpiration
Waterproof
Epidermal cells
Guard cells
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Trichomes
Provide shade
Prevent rapid air movemnet
Slow water loss
Prevent leaf consumption
Stomata
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Allow H2O and CO2 to enter
Lower epidermis
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Upper epidermis
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Wax on outer walls
Initiation and Development of Leaves
Basal Angiosperms and Eudicots
Growth at shoot apical meristem
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Leaf primordium
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Leaf protoderm
Leaf ground meristem
Bulk of mid-rib
Monocots
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Lamina
Allow regeneration
Basal expansion
