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Leaf TypesLeaf Types
Simple – single bladeSimple – single blade
Compound – 2 or Compound – 2 or more leafletsmore leaflets *Look for petiole & *Look for petiole &
budbud 2 kinds:2 kinds:
PinnatePinnate PalmatePalmate
Leaf EpidermisLeaf Epidermis
Upper and lower surface of leaf covered by Upper and lower surface of leaf covered by epidermisepidermis
Most cells lack chloroplasts and are transparentMost cells lack chloroplasts and are transparent
Cells secrete cuticle made of waxy cutinCells secrete cuticle made of waxy cutin
Many leaves have hairlike trichomesMany leaves have hairlike trichomes May reduce water lossMay reduce water loss May produce irritants – discourage herbivoresMay produce irritants – discourage herbivores
StomataStomata
Tiny openings for gas exchangeTiny openings for gas exchange
Flanked by guard cellsFlanked by guard cells
Most numerous on lower epidermis of Most numerous on lower epidermis of horizontal leaveshorizontal leaves
Mesophyll:Mesophyll:The middle layerThe middle layer
Made of photosynthetic ground tissueMade of photosynthetic ground tissue
Divided into 2 sublayers:Divided into 2 sublayers:
Palisade mesophyllPalisade mesophyll
Spongy mesophyllSpongy mesophyll
Vascular BundlesVascular Bundles
Veins extend throughout the mesophyllVeins extend throughout the mesophyll
Contains:Contains: Xylem – toward the top of veinXylem – toward the top of vein Phloem – toward the bottom of veinPhloem – toward the bottom of vein
Bundle sheath - 1 or more layers of cells Bundle sheath - 1 or more layers of cells surrounding the larger veinssurrounding the larger veins Made of parenchyma or schlerenchyma cellsMade of parenchyma or schlerenchyma cells
Monocot vs. DicotMonocot vs. Dicot
MONOCOTMONOCOT Base of leaf wraps Base of leaf wraps
around stem in a sheath around stem in a sheath (lack petiole)(lack petiole)
Some monocots do not Some monocots do not have distinct palisade have distinct palisade and spongy layersand spongy layers
DICOTDICOT Broad flattened blade Broad flattened blade
and petioleand petiole Palisade and spongy Palisade and spongy
layerlayer Guard cells shaped like Guard cells shaped like
kidney beanskidney beans
LEAF ADAPTATIONSLEAF ADAPTATIONS
CuticleCuticle
Placement of stomataPlacement of stomata
Needles vs. leavesNeedles vs. leaves
Length of petiolesLength of petioles