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LEAVES

LEAVES. Photosynthetic organs of plants. Basic Leaf Structure. Axillary bud . Simple – single blade Compound – 2 or more leaflets *Look for petiole & bud 2 kinds: Pinnate Palmate. Leaf Types. Leaf Cross-Section. Leaf Epidermis. Upper and lower surface of leaf covered by epidermis

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LEAVES

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  1. LEAVES Photosynthetic organs of plants

  2. Basic Leaf Structure Axillary bud

  3. Simple – single blade Compound – 2 or more leaflets *Look for petiole & bud 2 kinds: Pinnate Palmate Leaf Types

  4. Leaf Cross-Section

  5. Leaf Epidermis • Upper and lower surface of leaf covered by epidermis • Most cells lack chloroplasts and are transparent • Cells secrete cuticle made of waxy cutin • Many leaves have hairlike trichomes • May reduce water loss • May produce irritants – discourage herbivores

  6. Stomata • Tiny openings flanked by guard cells • Gas exchange; transpiration • Most numerous on lower epidermis of horizontal leaves

  7. Mesophyll • Made of photosynthetic ground tissue • Divided into 2 sublayers: • Palisade mesophyll • Spongy mesophyll

  8. Vascular Bundles • Veins extend throughout the mesophyll • Contains: • Xylem • Phloem • Bundle sheath - 1 or more layers of cells surrounding the larger veins • Made of parenchyma or schlerenchyma cells

  9. MONOCOT Base of leaf wraps around stem in a sheath (lack petiole) Some monocots do not have distinct palisade and spongy layers DICOT Broad flattened blade and petiole Palisade and spongy layer Guard cells shaped like kidney beans Monocot vs. Dicot

  10. LEAF ADAPTATIONS • Cuticle • Placement of stomata • Needles vs. leaves • Length of petioles

  11. Modified Leaves • Spines • Tendrils • Bulbs • Carnivorous

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