Leaves
• Purpose – photosynthesis
• Sunlight passes through the
cuticle and epidermis into the
photosynthetic tissue beneath
the leaf surface
Leaf structure/Function
• Mesophyll-photosynthetic tissue.
• 2 kinds of parenchyma
–Palisade mesophyll – column-shaped
cells photosynthesis takes place
–Spongy mesophyll - irregularly
shaped cells surrounded by open
space good for gas exchange
Functions/Structure
• Transpiration - loss of water through
the stomata
• Regulated by the guard cells
• Water in the surrounding cells
determines if the guard cells are open
or closed.
Leaf modifications
Modified for purposes other than
photosynthesis
• produce toxins to offer protection
• Cactus spines – prevent water loss and
provide protection
• Carnivorous plants have leaves that trap
insects
Leaf modification
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More modifications
Sweet pea tendrils for climbing
Overlapping scales to protect buds
Colorful bracts of poinsettias
Aloe leaves store water
Bulb – shortened stem, a flower bud, and
immature leaves with food stored in the base