Presentation on theme: "Leaves. Above ground plant organ used to capture sunlight for photosynthesis Typically flat and thin to allow light to penetrate fully into the tissues."— Presentation transcript:
Above ground plant organ used to capture sunlight for photosynthesis Typically flat and thin to allow light to penetrate fully into the tissues
Leaf Functions Leaves perform the following functions for the plant: 1) Photosynthesis 2) Storage of starch 3) Contain the majority of sites for gas exchange (stomata)
Leaf Morphology Leaf morphology is important for plant identification. Nodes are the place where leaves attach to the branch. Leaves can be arranged oppositely (paired from a node), whorled (more than 2 leaves from one node) or alternately (one leaf per node) on a branch.
Leaf Morphology Leaves can be simple or compound. Compound leaves can be palmate (having leaflets arranged like fingers in a hand) or pinnate (having leaflets arranged along the main vein).
Leaf Morphology Blade: the actual ‘leaf’, also called the lamina Petiole: the attachment leading from the node to the blade Midrib: the central vein (vascular path) of the blade
Leaf Morphology Margin: the edge of the leaf. The margin can be a key characteristic that helps identify the plant
Leaf Cross-Section A leaf is considered to have 3 distinct sections: 1) An epidermis that covers both the top and bottom of the leaf 2) A mesophyll layer on the inside that does the majority of the photosynthesis 3) Vascular bundles to transport water and sugar to and from the leaf
Leaf Cross-Section The epidermis is covered with a waxy cuticle to help prevent against water loss. The epidermis has tiny pores called stomata with guard cells on either side. They work together to exchange gases and water vapour between the outside environment and the inside of the leaf. Stomata are more common on the underside of the leaf.
Leaf Cross-Section The mesophyll layer contains upright palisade cells that contain many more chloroplasts than the spongy layer below them. Palisade layer is used for photosynthesis and the spongy layer is more spacious to allow for maximum absorption of carbon dioxide for photosynthesis.
Photosynthesis Photosynthesis is the conversion of light energy, water and carbon dioxide into sugar and oxygen. The light energy comes from the Sun and is used by chloroplasts in the leaves of the plant. The water comes from the soil through the roots.
Photosynthesis The carbon dioxide enters the leaf through the stomata Oxygen will leave the stomata as a waste product The other end product, sugar, is moved to different areas of the plant depending on need… this will be in an upcoming lecture…