Tendril – modified leaf found in many vines (peas,
pumpkins)
Carnivorous plants – modified leaves that trap insects
Spines – protect plant
Blade – broad, flat portion; is the site of most
photosynthesis
Petiole – attaches most blades to stems
Simple leaf – one blade
Compound leaves – blade is divided into leaflets
In some species, the leaflets themselves are divided
Leaves consist of three tissue systems
Dermal – epidermis (single layer with waxy cuticle)
with openings called stomata for gas exchange (the
number varies by species)
Ground – mesophyll (chloroplast-rich parenchyma
cells
palisade mesophyll – site of photosynthesis,
located directly below epidermis
spongy mesophyll – irregularly spaced cells
surrounded by large air spaces
Vascular – in bundles called veins (xylem and phloem)
Venation is the arrangement of veins in a leaf
Monocots – parallel
Dicots – netted
palmate
pinnate
Primary site for photosynthesis in most plants
Leaves that develop in full sun are thicker, have a smaller
area per leaf, and have more chloroplasts per leaf
Dense coating of hairs prevent the absorption of too
much sunlight
Stoma – opening in cuticle to allow gas exchange
Guard cells – two kidney-shaped cells that regulate the
stoma
Most plants – stoma open during the day and closed at
night
Stomata will close if water is scarce
If stomata are closed, virtually no photosynthesis takes
place