Plant Structures: Leaves What is a leaf? Leaves are structures produced on stems where photosynthesis 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 photosynthesis of 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 sometimes look 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 plant Parenchyma cells loosely arranged, 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 leaf Double/Doubly compound leaf Leaflet

Compound leaf Simple leaf Doubly compound leaf

Pinnate venation

Alternate Whorled Opposite