KEY CONCEPT Leaves absorb light and carry out photosynthesis.

KEY CONCEPTLeaves absorb light and carry out photosynthesis.

The blade is usually broad and flat. collects sunlight for photosynthesis connects to the stem by a petiole blade petiole Most leaves share some similar structures.

Mesophyll is between the leaf’s dermal tissue layers. cuticle upper epidermis palisademesophyll spongymesophyll lowerepidermis

Stomata open and close when guard cells change shape. When stomata are open, water evaporates and gas exchanges. Stomata close at night and when plant loses too much water. stoma guard cells • Guard cells surround each stoma.

Leaves may be simple, compound, or double compound. Compound leaf Simple leaf Double compound leaf

Leaf veins may be parallel or pinnate. Parallel veins Pinnate veins

Leaf margins may be toothed, entire, or lobed. Toothed margin Entire margin Lobed margin

cuticle upper epidermis palisademesophyll xylem spongymesophyll phloem lowerepidermis stomata Most leaves are specialized systems for photosynthesis. • There are two types of mesophyll cells. • both types contain chloroplasts • palisade mesophyll absorbs sunlight • spongy mesophyll connects to stomata

Leaves have many adaptations. • for extreme temperatures, ex: pine needles

Leaves have many adaptations. • for extreme temperatures, ex: pine needles • for water loss,ex: cactus spines

for aquatic environments, ex: water lily • Leaves have many adaptations. • for extreme temperatures, ex: pine needles • for water loss,ex: cactus spines

for aquatic environments, ex: water lily • Leaves have many adaptations. • for extreme temperatures, ex: pine needles • for water loss,ex: cactus spines • for getting food,ex: Venus’ flytrap

KEY CONCEPT Leaves absorb light and carry out photosynthesis.