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Leaves

Leaves. Function of leaves:. Primary site of photosynthesis. Site of transpiration. Site of gas exchange. Leaf Structures: Wide variety of shapes and sizes - important feature in plant identification. Blade : Broad, flat portion of leaf. - Site of most photosynthesis.

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Leaves

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  1. Leaves

  2. Function of leaves: • Primary site of photosynthesis • Site of transpiration • Site of gas exchange Leaf Structures: Wide variety of shapes and sizes - important feature in plant identification • Blade: Broad, flat portion of leaf - Site of most photosynthesis • Petiole:Stalk like region on leaf where it is attached to stem

  3. Three Tissue Layers: **Label Your Leaf CS** • Epidermis layer: usually 1 cell layer thick - On top and bottom of leaf - impermeable cuticle (top & bottom) - H2O, O2, & CO2 enter & exit through stomata (bottom) Upper Epidermis LEAF CS Lower Epidermis CO2 O2

  4. Mesophyll Layer: Organized into two layers a. Palisade Mesophyll - Lays directly beneath upper epidermis - Site of most photosynthesis - Made up of columnar cells & are tightly packed into one or two layers LEAF CS Palisade Mesophyll Mesophyll

  5. b. Spongy Mesophyll: - Beneath palisade layer - Irregularly shaped cells (balloons) -surrounded by large air spaces for diffusion: O2, CO2, and H2O All the Black Space is AIR!!! LEAF CS Spongy Mesophyll Mesophyll

  6. 3. Vascular Layer: - Consists of vascular bundles called veins (circular) - Continuous with vascular bundles in stem & petiole - Veins branch repeatedly so each cell is less than 1mm from a vein. Xylem (top) LEAF CS Phloem

  7. Venation in Monocots and Dictos:Arrangements of veins in a leaf - Monocots: Parallel venation - Dicots: Net Venation - Ex: grasses - Ex: maple

  8. Leaf Processes: **Write Small!!!** • Transpiration: Evaporation of water in plant through stomata which increases absorption at roots • Gas Exchange: Exchange of CO2 and O2 through stomata • Stomata: Bordered by 2 kidney shaped guard cells -Modified epidermis cells that regulate H2O and gas exchange - Contain chloroplasts • - Open during day, closed during night • - Found in lower epidermis

  9. Stomata in monocot and dicot leaves: Monocots: Parallel Dicots: Random LEAF CS Stomata

  10. Photosynthesis: Process by which chlorophyll and enzymes in leaves convert certain wave lengths of light to chemical energy

  11. Simple equation of photosynthesis:Sunlight + CO2 + H2O Carbohydrates + O2

  12. Chloroplasts: Sacks that contain photosynthetic pigments - Site of photosynthesis Thylakoids: Series of flattened sacks - Acts like solar panels to collect sun energy Grana: Stacks of thylakoids Stroma: Liquid solution which contains 4 pigments - Surrounds grana

  13. Chlorophyll: 1) Chlorophyll A = 95% 2) Chlorophyll B = 5% 2 Other Pigments: Xanthophylls YELLOWS CarotenesORANGES Spring/Summer: only green is reflected = SEE all other colors hidden Fall Colors: Chlorophyll is all used up, see other reflected pigments Chromatography: technique used to separate a mixture into its different components

  14. 700nm 400nm ROYGBIV ed range el low reen ndigo iolet lue =White Light (prism)

  15. Uses of Leaves in Plant Identification • 1. Arrangement of leaves on stem • 2. Divisions in a leaf • 3. Shape • 4. Character of leaf margin • 5. Veins

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