Leaves

Lifespan:

Deciduous vs Evergreen

Morphology:

• Blade Number
  • simple (+/- lobed)
  • palmately compound
  • pinnately compound
• Juvenile vs Mature
• Determinate - fixed size and shape for species
  (good for Identification)

Arrangement:

• alternate = 1/node
• opposite = 2/node
• whorled = >2/node

Structure/Function:

Cutin = waxy covering prevents water loss

Upper Epidermis = window-like (no chloroplasts) lets light in

Palisade Mesophyll = columns of cells doing most of photosynthesis

Vein

Xylem = water and minerals up from root into leaf

Phloem = sugar from leaf to rest of plant

Gas Spaces = O₂ out and CO₂ in during day, reverse at night

Spongy Mesophyll = loosely packed cells some PS

Lower Epidermis = Controls water loss prevention (cuticle) &

Guard Cells = change shape to open and close stoma

Stoma = hole for gas exchange (CO₂, O₂) and evaporative cooling (H₂O)

Specialized Leaves

• Roadside Charmin = Verbascum thapsis
• Epidermal Hairs and chemical defense against herbivores, Cannabis
• Floating Leaves have stomata in upper epidermis, air chambers beneath for floatation: Victoria Cypress Gardens with plexiglass circle
• Carnivorous Plants, get Nitrogen from digested insects, hairs help trap insect and secrete enzymes: Dionea, Drosera, Sarrascennia, or leaves serve as traps: Utricularia.

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