Plant Structures: Leaves

What is a leaf?• Leaves are structures produced on stems wherephotosynthesis primarily takes place.Functions:• Photosynthesis• Evapotranspiration (loss of water vapor from the stomata) moves water and nutrients up from the roots.• Small openings in the leaf (stomata) regulate moisture and gas exchange and temperature in the plant.• Used for feed and food.• Habitat for some organisms• Used for plant identification• Used for asexual reproduction (cuttings)

External structure:

Blade = Broad and flat part of the leaf where most of the photosynthesisof the plant takes place.

Petiole = The thin stalk that connects the leaf to the stem.

Stipule = An outgrowth at the base of the petiole – can be in pairs; can vary and be in the form of glands, scales, hairs, spines and sometimeslook leaf-like.

Internal structure:

Waxy coating – prevents water loss – can be thicker in desert plants

Tightly packed parenchyma cells filled with chloroplasts

Vascular bundle/ leaf veins - moves water and nurients through the plantParenchyma cells

looselyarranged, help with movement of O2, CO2 and water vapor. May contain chloroplasts

Openings that allow for gas exchange (water vapor, O2, CO2)

Specialized kidney shaped cells that open and close the stomata

Epidermis – Upper – Protect underlying tissues, could have a waxy coating to prevent water loss.Lower – Contains stomata

Blade

Leaflets

Simple leaf

Compound leafDouble/Doubly compound leaf

Leaflet

Compound leaf

Simple leaf

Doubly compoundleaf

Pinnatevenation

Alternate

Whorled

Opposite