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

• 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