Chapter 7 Lecture Outline Leaves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Outline  Introduction Leaf Development Leaf Parts Leaf Complexity Leaf Vein & Leaflet Pattern Functions of Leaves  Leaf Arrangements and Types  Internal Structure of Leaves  Specialized Leaves  Autumnal Changes in Leaf Color  Human and Ecological Relevance of Leaves

INTRODUCTION  LEAF DEVELOPMENT: All leaves originate as primordia in buds.  LEAF PARTS (Gross Anatomy) At maturity, most leaves have: Petiole (rachis) = _________________ – Leaves that are sessile lack a petiole Lamina = _______________________ Veins = ________________________  Leaves of flowering plants at nodes also usually have axillary buds at base.

 LEAF COMPLEXITY SIMPLE LEAVES = ___________ COMPOUND LEAVES = _______  LEAF VEIN & LEAFLET PATTERN PINNATE: ______________ – Simple Pinnate – Compound Pinnate o 1 st level o 2 nd level PALMATE: ______________ – Simple Palmate – Compound Palmate 2 nd level Compound Pinnate Palmately compound

 LEAF VEINATION … PARALLEL:  Monocots - Parallel venation  Dicots - Pinnate or Palmate. Parallel venation

 FUNCTIONS OF LEAVES = _______________________________________ OrganellE: ___________________ Cell: ___________________ Need: – _________________ Produce: Stomata function. – Guard Cells

Other functions of leaves: – Wastes disposed of when leaves shed. – Water movement o Transpiration =__________________.

Leaf Arrangements and Types  Leaves at nodes – Opposite – Alternate – Whorled Opposite Whorled Alternate

INTERNAL STRUCTURE OF LEAVES  3 regions: Epidermis, Mesophyll, Veins  Epidermis, Herbaceous & Woody plants Surface coated with __________ Functions: 1)____________ 2) Water:___________________ 3) Glands Stomata

Internal Structure of Leaves … Stomata – Location: ___________ – Bordered by two _____________ Cells. o Have a thickened inner wall – Functions: _____________________ « Gas exchange « Evaporation of water

How Stomata open & close : Changes in water content cause them to inflate or deflate. Rigid inner surface remains stiff Inflate - Stomata open Deflate - Stomata close

 MESOPHYLL: Region between upper and lower epidermis, excluding the veins. FUNCTION: __________________________________ EUDICOTS: TWO SUB-REGIONS – Location: _____ – Shape of cells: ______________ - # Contains chloroplasts 2) Spongy Mesophyll – Location: _______ – Shape of cells: ____________ – Air spaces NOT IN MONOCOTS 1) Palisade Mesophyll

Microscopic View of a EUDICOT Mesophyll MONOCOT Mesophyll

Chlorencyma Cells Vein

 VEINS (vascular bundles) Location: _________________________ Tissue & Cells: ____________________ – Surrounded by bundle sheath of thicker-walled parenchyma

MONOCOT: Zea (Corn) Leaf Guard Cells Vein Sieve-Tube Cells Companion Cells ZEA VEIN

Eudicot Vein Vessels Sieve-Tube Cells Companion Cells

Mesophyll and Veins  Differences found in Monocots Flowering plants Mesophyll noy differentiated into palisade & spongy layers Stomata on upper & lower epidermis BULLIFORM CELLS on either side of main central vein Function: Causes leaf to fold or roll, reducing transpiration Monocot leaf cross section

SPECIALIZED LEAVES  Shade Leaves Amount light: – Overall Size: _________ – Thickness: ____ – Have fewer hairs Sun Shade

Sun leaf Shade leaf

 LEAVES OF ARID REGIONS Problems for plant: – Water: ________________ – Temperatures: ______________ – Light Intensities: _______________ Leaves reduce loss of water by: – Cuticle: – Thickness: – # Stomata o or sunken stomata – Dense, hairy coverings, often silver  LEAVES OF AQUATIC AREAS Less xylem and phloem Mesophyll not differentiated into palisade and spongy layers. Large air spaces

 TENDRILS Shape: __________ Function: _________ Examples: Garden peas  SPINES Shape: Function: Also reduce leaf surface and water loss, – Cacti o Leaf tissue replaced with sclerenchyma. o Photosynthesis occurs in stems. Tendrils Spine

Specialized Leaves  Thorns - Modified stems in axils of woody plants  Prickles - Outgrowths from epidermis or cortex Prickle Thorn

 Storage leaves Succulent leaves: Store ______________ – parenchyma cells with large vacuoles – Many desert plants

Fleshy leaves store ____________. – Onions, lily

 Flower-Pot Leaves urn-like pouches: Ants bring soil & Nit. Wastes: Flower-pot leaf sliced lengthwise

 Window leaves Succulent, Africa Leaves buried in ground. – End is transparent – Function:

 Reproductive Leaves Walking fern - New plants at leaf tips Air plant - Tiny plantlets along leaf margins Air Plant

 Floral Leaves (bracts) bases of flowers/flower stalks Poinsettia - brightly colored bracts surround flowers. Clary’s sage - Colorful bracts are at top of flowering stalks. Poinsettia Clary’s sage

 Insect-Trapping Leaves swampy areas and bogs – Nitrogen is: o Specialized leaves trap and digest insects. Pitcher Plants – cone-shaped leaves. Pitcher plant

 Insect-Trapping Leaves Sundews – leaves covered with glandular hairs have sticky digestive enzymes – Venus’s Flytraps – North Carolina and South Carolina – Mechanically trap insects. Venus’s Flytraps Sundew

 Insect-Trapping Leaves Bladderworts – floating in shallow water – bladders have trap doors trap insects inside Bladder of bladderwort

Autumnal Changes in Leaf Color  Chloroplasts and pigments: Chlorophylls - Green Carotenoids - Yellows In fall, chlorophylls break down and other colors are revealed. anthocyanins (red or blue) and betacyanins (red) may present in vacuole.

Human and Ecological Relevance of Leaves  STUDENTS READ ON YOUR OWN IN TEXT

Review