Chap. 29 : LeavesChap. 29 : Leaves

I.I. Primary Function of Leaf Primary Function of Leaf

PhotosynthesisPhotosynthesis – depends on light, temp., and – depends on light, temp., and supply of water and carbon dioxide.supply of water and carbon dioxide.

6 CO6 CO22 + 12 H + 12 H22O + light CO + light C66HH1212OO66 + 6H + 6H22O + 6OO + 6O22

(sugar)(sugar)

-- Going from left to right is -- Going from left to right is photosynthesisphotosynthesis

-- Going from right to left is -- Going from right to left is respirationrespiration. Instead of light, energy . Instead of light, energy in the form of heat is produced.in the form of heat is produced.

II. Leaf StructureII. Leaf Structure

vein

petiole

stipules

blade

A. Types of vein patterns (venation)A. Types of vein patterns (venation)

1. Parallel – monocots (1 seed leaf) – ex. Corn1. 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. Maples2. Palmate – no main vein (like palm of hand) Ex. Maples

3. Pinnate – one main vein. Ex. Locust 3. Pinnate – one main vein. Ex. Locust

Dicots – 2 seed leaves.

B. Simple vs. Compound LeavesB. Simple vs. Compound Leaves

1. Compound – blade made up of leaflets. One 1. Compound – blade made up of leaflets. One bud for the whole leaf.bud for the whole leaf.

Pinnately compound

Bud

Palmately compound bud

Bud – new leaf -- simple leaf

Bud – enclosed – compound leaf.

2. Simple – leaflet is blade2. Simple – leaflet is blade

Most trees around here. Ex. Maples, oaks, Most trees around here. Ex. Maples, oaks, dogwoods ( 1 bud per leaf)dogwoods ( 1 bud per leaf)

C. Leaf Arrangement – arrangement of eachC. Leaf Arrangement – arrangement of each leaf leaf on the branch in relation to the other leaves.on the branch in relation to the other leaves.

1. Alternate 2. Opposite1. Alternate 2. Opposite

DAMBDAMB – dogwoods, ashes, maples, and – dogwoods, ashes, maples, and buckeyes. Only ones around here with buckeyes. Only ones around here with opposite arrangement. opposite arrangement. Most trees haveMost trees have alternate arrangementsalternate arrangements..

D. Leaf Margin (edge)D. Leaf Margin (edge)

1.1. ToothedToothed 2. Smooth or Entire 2. Smooth or Entire

3. Lobed3. Lobed

III. Leaf TissuesIII. Leaf Tissues

AB

C

D

E

F

GHIJ

K

L

A A Epidermal hairEpidermal hair – reduces water loss, secretes oil – reduces water loss, secretes oil B. B. CuticleCuticle – waxy layer – prevents water loss – waxy layer – prevents water loss C. C. Upper epidermisUpper epidermis – protection – protection D. D. Palisade cellsPalisade cells – parenchyma tissue – used for photosynthesis. – parenchyma tissue – used for photosynthesis. E. E. Spongy mesophyllSpongy mesophyll – storage tissue – stores food,water,waste – storage tissue – stores food,water,waste F. F. Lower epidermisLower epidermis – protection – protection G. G. Xylem & PhloemXylem & Phloem – tissues that conduct (move) things – tissues that conduct (move) things

(water) (food)(water) (food) H. H. Fibrovascular bundleFibrovascular bundle (vein) – contains conducting tissues (vein) – contains conducting tissues

I. I. StomataStomata – opening for gas exchange – opening for gas exchange J. J. Guard cellGuard cell – regulates the opening and closing of stomata – regulates the opening and closing of stomata K. K. ChloroplastChloroplast – move in counter clockwise circle to absorb as – move in counter clockwise circle to absorb as

much light as possible.much light as possible. L. L. Air spacesAir spaces – contain gases – CO – contain gases – CO2 2 and Oand O22

Actual Leaf Cross-SectionActual Leaf Cross-Section

IV. Water LossIV. Water Loss

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

V. Leaf ColorationV. Leaf Coloration

A. Spring and SummerA. Spring and Summer

-- -- chlorophyllchlorophyll is produced and makes leaves is produced and makes leaves green.green.

B. FallB. Fall

drop in temp. and daylight hrs. causes drop in temp. and daylight hrs. causes chlorophyll to stop being produced so other chlorophyll to stop being produced so other pigments can be seen :pigments can be seen :

xanthophyll – yellowxanthophyll – yellow

-Carotene – orangeCarotene – orange

-- -- anthocyanin – redanthocyanin – red

-- chromoplast – blue-- chromoplast – blue

C. WinterC. Winter

-- leaves turn -- leaves turn brownbrown from the death of tissue and the releasing from the death of tissue and the releasing of of tannic acid.tannic acid.

VI. Falling LeavesVI. Falling Leaves

Called Called abscissionabscission

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

VII. Leaf ModificationsVII. Leaf Modifications - change in leaf structure to better suit it - change in leaf structure to better suit it

to its environmentto its environment.. 1. Succulent leaves – fleshy – holds water.1. Succulent leaves – fleshy – holds water. ex. Cactus, desert plants, aloe,conifersex. Cactus, desert plants, aloe,conifers

2. Tendrils – used for anchorage. Ex. Vines2. Tendrils – used for anchorage. Ex. Vines 3. Insectivorous – leaves designed to capture 3. Insectivorous – leaves designed to capture

insects. Still photosynthesis but need insects insects. Still photosynthesis but need insects because the soil lacks necessary nutrients.because the soil lacks necessary nutrients.

ex. Venus flytrapex. Venus flytrap

VIII. Plant CellsVIII. Plant Cells

3 types :3 types : 1. 1. ParenchymaParenchyma – loosely packed, flexible. – loosely packed, flexible.

Used for photosynthesis, metabolism, and Used for photosynthesis, metabolism, and storage.storage.

2. 2. CollenchymaCollenchyma – thicker cell walls. Support. – thicker cell walls. Support. Ex. CeleryEx. Celery

3. 3. SclerenchymaSclerenchyma- thicker, rigid cell walls. - thicker, rigid cell walls. Support and strengthen nongrowing parts. Ex. Support and strengthen nongrowing parts. Ex. Covering of nuts Covering of nuts

IX. Plant Tissue SystemsIX. Plant Tissue Systems

3 types :3 types : 1. 1. Dermal TissueDermal Tissue – forms outside layer(s) of – forms outside layer(s) of

plants. In woody plants also becomes the barkplants. In woody plants also becomes the bark 2. 2. Ground TissueGround Tissue – middle layer. Made up of – middle layer. Made up of

all 3 plant cell types. Support, metabolism, and all 3 plant cell types. Support, metabolism, and storage.storage.

3. 3. Vascular TissueVascular Tissue – innermost layer. Function – innermost layer. Function in transport and support. Xylem (water (also in transport and support. Xylem (water (also forms wood)) and phloem (food)forms wood)) and phloem (food)

X. Plant GrowthX. Plant Growth

2 kinds :2 kinds :

1. 1. Primary growthPrimary growth – plant grows in length or – plant grows in length or height. Done by apical(fast growing tissue in height. Done by apical(fast growing tissue in roots) and intercalary (in stems and leaves) roots) and intercalary (in stems and leaves) meristems.meristems.

2. 2. Secondary growthSecondary growth – grow in diameter or – grow in diameter or thickness. Done by lateral meristems (adds thickness. Done by lateral meristems (adds more tissue and wood to roots and stems)more tissue and wood to roots and stems)