Leaf structure Leaf Structures N O K C

Leaf structure

Leaf Structures N O K C D I J L E M G F F G

Epidermal cells • Epidermal Cells –produce the waxy cuticle

Cuticle • Cuticle –waxy (non-cellular layer) • Protects against excessive water loss and infection • Restricts gas exchange • Deters herbivores

Palisade Mesophyll • Cells are tightly packed together with lots of chloroplasts • Primary site of photosythesis

Spongy Mesophyll • Cells are loosely arranged with air spaces in between them • Fewer chloroplasts • Promotes rapid gas diffusion (CO 2 and O 2)

Guard Cells • Guard Cells –size is depending on water content of plant • When full of water they push apart • When lacking water they come together • Control opening of stomata

Stomata • Stomata- pores in the epidermis • More located on lower surface • Where gas exchange takes place

Leaf Adaptations

Adaptations to SALT Mangrove Plants • Have special pores that excrete salt • Their leaves can tolerate to store high levels of salt • Restrict the openings of their stomata to preserve freshwater • Turn their leaves to reduce water loss

Adaptation to WATER Underwater plants • Leaves are flexible so they don’t break with currents • Air spaces in the leaf so they float (Hydrophilic) • Chlorophyll is restricted to the top layer

Adaptations to DRY • Hairs on the leaf trap humidity • Waxy leaf surface to reduce water loss • Succulent leaves store water • Spines have less surface area

Extreme heat • Example: Octillo • shed leaves when it gets to hot • lays dormant • lowers metabolism

Adaptations for DROUGHT i. Avoiders • Short lifespan • Wet season • Seeds survive drought • Drought deciduous species – Leaves shed in dry season

Adaptations for DROUGHT ii. Tolerators • Leaves transpire slowly • Change orientation of leaves • Sunken stomata – E. g. pines • More efficient photosynthesis

Adaptations in the RAINFOREST (Moist and shaded) • Waxy surfaces (drip tips) drain water to prevent fungal growth • Large surface area on leaves to absorb more light

Adaptations to BOREAL Cold and Dry • Extracellular freezing to protect cells • NEEDLE LEAVES • compact to protect vascular tissue • waxy cuticle protects the mesophyll & prevents water loss • prevent snow accumulation • Dark to absorb solar heat • Don’t shed = photosynthesis early in spring

Adaptations to the ARCTIC • Dark colours to absorb more solar heat • Covered in small hairs to conserve heat • Small surface area to prevent freezing

Adaptations to avoid BEING EATEN • Chemical Defence: • poison (poison ivy) • aromatic oils (eucalyptus) • alkaloids (tobacco) • Mechanical Defence • Spines / Thorns (ex: raspberry)

Hydrophytic

Mesophytic

xerophytic

Practice • Page 557 21 -23 • Page 559 12 -16