Chap. 29 : Leaves

I.Primary Function of Leaf Photosynthesis – depends on light, temp., and supply of water and carbon dioxide. Photosynthesis – depends on light, temp., and supply of water and carbon dioxide. 6 CO H 2 O + light C 6 H 12 O 6 + 6H 2 O + 6O 2 6 CO H 2 O + light C 6 H 12 O 6 + 6H 2 O + 6O 2 (sugar) (sugar) -- Going from left to right is photosynthesis -- Going from right to left is respiration. Instead of light, energy in the form of heat is produced.

II. Leaf Structure vein petiole stipules blade

A. Types of vein patterns (venation) 1. Parallel – monocots (1 seed leaf) – ex. Corn 1. Parallel – monocots (1 seed leaf) – ex. Corn -- veins all run the same way -- veins all run the same way

2. Palmate – no main vein (like palm of hand) Ex. Maples 2. Palmate – no main vein (like palm of hand) Ex. Maples 3. Pinnate – one main vein. Ex. Locust Dicots – 2 seed leaves.

B. Simple vs. Compound Leaves 1. Compound – blade made up of leaflets. One bud for the whole leaf. 1. Compound – blade made up of leaflets. One bud for the whole leaf. Pinnately compound Bud Palmately compound bud

Bud – new leaf -- simple leaf Bud – enclosed – compound leaf.

2. Simple – leaflet is blade Most trees around here. Ex. Maples, oaks, dogwoods ( 1 bud per leaf) Most trees around here. Ex. Maples, oaks, dogwoods ( 1 bud per leaf) C. Leaf Arrangement – arrangement of each leaf on the branch in relation to the other leaves.

1. Alternate 2. Opposite DAMB – dogwoods, ashes, maples, and buckeyes. Only ones around here with opposite arrangement. Most trees have alternate arrangements.

D. Leaf Margin (edge) 1. Toothed 2. Smooth or Entire 3. Lobed

III. Leaf Tissues A B C D E F G H IJ K L

A Epidermal hair – reduces water loss, secretes oil A Epidermal hair – reduces water loss, secretes oil B. Cuticle – waxy layer – prevents water loss B. Cuticle – waxy layer – prevents water loss C. Upper epidermis – protection C. Upper epidermis – protection D. Palisade cells – parenchyma tissue – used for photosynthesis. D. Palisade cells – parenchyma tissue – used for photosynthesis. E. Spongy mesophyll – storage tissue – stores food,water,waste E. Spongy mesophyll – storage tissue – stores food,water,waste F. Lower epidermis – protection F. Lower epidermis – protection G. Xylem & Phloem – tissues that conduct (move) things G. Xylem & Phloem – tissues that conduct (move) things (water) (food) (water) (food) H. Fibrovascular bundle (vein) – contains conducting tissues H. Fibrovascular bundle (vein) – contains conducting tissues I. Stomata – opening for gas exchange I. Stomata – opening for gas exchange J. Guard cell – regulates the opening and closing of stomata J. Guard cell – regulates the opening and closing of stomata K. Chloroplast – move in counter clockwise circle to absorb as much light as possible. K. Chloroplast – move in counter clockwise circle to absorb as much light as possible. L. Air spaces – contain gases – CO 2 and O 2 L. Air spaces – contain gases – CO 2 and O 2

Actual Leaf Cross-Section

IV. Water Loss -- Transpiration – the losing of water through the stomata on the leaf surface to create a difference in turgor pressure (keeps plants stiff) which causes water to be drawn up the stem (capillarity). -- Transpiration – the losing of water through the stomata on the leaf surface to create a difference in turgor pressure (keeps plants stiff) which causes water to be drawn up the stem (capillarity).

V. Leaf Coloration A. Spring and Summer A. Spring and Summer -- chlorophyll is produced and makes leaves green. -- chlorophyll is produced and makes leaves green. B. Fall B. Fall drop in temp. and daylight hrs. causes chlorophyll to stop being produced so other pigments can be seen : drop in temp. and daylight hrs. causes chlorophyll to stop being produced so other pigments can be seen : xanthophyll – yellow xanthophyll – yellow

-Carotene – orange -- anthocyanin – red -- chromoplast – blue C. Winter -- leaves turn brown from the death of tissue and the releasing of tannic acid. -- leaves turn brown from the death of tissue and the releasing of tannic acid.

VI. Falling Leaves Called abscission Called abscission -- weak zone forms where petiole attaches. Pectin (jelly) attaching petiole dissolves. Slightest wind or pressure jars leaf. Once fallen, a layer of cork seals the hole left by the leaf. -- weak zone forms where petiole attaches. Pectin (jelly) attaching petiole dissolves. Slightest wind or pressure jars leaf. Once fallen, a layer of cork seals the hole left by the leaf.

VII. Leaf Modifications - change in leaf structure to better suit it to its environment. 1. Succulent leaves – fleshy – holds water. 1. Succulent leaves – fleshy – holds water. ex. Cactus, desert plants, aloe,conifers ex. Cactus, desert plants, aloe,conifers 2. Tendrils – used for anchorage. Ex. Vines 2. Tendrils – used for anchorage. Ex. Vines 3. Insectivorous – leaves designed to capture insects. Still photosynthesis but need insects because the soil lacks necessary nutrients. 3. Insectivorous – leaves designed to capture insects. Still photosynthesis but need insects because the soil lacks necessary nutrients. ex. Venus flytrap ex. Venus flytrap

VIII. Plant Cells 3 types : 3 types : 1. Parenchyma – loosely packed, flexible. Used for photosynthesis, metabolism, and storage. 1. Parenchyma – loosely packed, flexible. Used for photosynthesis, metabolism, and storage. 2. Collenchyma – thicker cell walls. Support. Ex. Celery 2. Collenchyma – thicker cell walls. Support. Ex. Celery 3. Sclerenchyma- thicker, rigid cell walls. Support and strengthen nongrowing parts. Ex. Covering of nuts 3. Sclerenchyma- thicker, rigid cell walls. Support and strengthen nongrowing parts. Ex. Covering of nuts

IX. Plant Tissue Systems 3 types : 3 types : 1. Dermal Tissue – forms outside layer(s) of plants. In woody plants also becomes the bark 1. Dermal Tissue – forms outside layer(s) of plants. In woody plants also becomes the bark 2. Ground Tissue – middle layer. Made up of all 3 plant cell types. Support, metabolism, and storage. 2. Ground Tissue – middle layer. Made up of all 3 plant cell types. Support, metabolism, and storage. 3. Vascular Tissue – innermost layer. Function in transport and support. Xylem (water (also forms wood)) and phloem (food) 3. Vascular Tissue – innermost layer. Function in transport and support. Xylem (water (also forms wood)) and phloem (food)

X. Plant Growth 2 kinds : 2 kinds : 1. Primary growth – plant grows in length or height. Done by apical(fast growing tissue in roots) and intercalary (in stems and leaves) meristems. 1. Primary growth – plant grows in length or height. Done by apical(fast growing tissue in roots) and intercalary (in stems and leaves) meristems. 2. Secondary growth – grow in diameter or thickness. Done by lateral meristems (adds more tissue and wood to roots and stems) 2. Secondary growth – grow in diameter or thickness. Done by lateral meristems (adds more tissue and wood to roots and stems)