Chap. 29 : Leaves

1
Chap. 29 Leaves
2
Primary Function of Leaf

• Photosynthesis depends on light, temp., and
  supply of water and carbon dioxide.
• 6 CO2 12 H2O light
  C6H12O6 6H2O 6O2
• 
  (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.

3
II. Leaf Structure
blade
vein
petiole
stipules
4
A. Types of vein patterns (venation)

• 1. Parallel monocots (1 seed leaf) ex. Corn
• 
  -- veins all run the same way

5

• 2. Palmate no main vein (like palm of hand)
  Ex. Maples
• 3. Pinnate one main vein. Ex. Locust

Dicots 2 seed leaves.
6
B. Simple vs. Compound Leaves

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

Bud
Pinnately compound
bud
Palmately compound
7
Bud new leaf -- simple leaf
Bud enclosed compound leaf.
8
2. Simple leaflet is blade

• 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.

9
1. Alternate 2. Opposite

• DAMB dogwoods, ashes, maples, and buckeyes.
  Only ones around here with opposite arrangement.
  Most trees have alternate arrangements.

10
D. Leaf Margin (edge)

• Toothed 2. Smooth or Entire
• 3. Lobed

11
III. Leaf Tissues
A
B
C
D
K
E
F
L
I
J
G
H
12

• A Epidermal hair reduces water loss, secretes
  oil
• B. Cuticle waxy layer prevents water loss
• C. Upper epidermis protection
• D. Palisade cells parenchyma tissue used for
  photosynthesis.
• E. Spongy mesophyll storage tissue stores
  food,water,waste
• F. Lower epidermis protection
• G. Xylem Phloem tissues that conduct (move)
  things
• (water) (food)
• H. Fibrovascular bundle (vein) contains
  conducting tissues
• I. Stomata opening for gas exchange
• J. Guard cell regulates the opening and closing
  of stomata
• K. Chloroplast move in counter clockwise circle
  to absorb as much light as possible.
• L. Air spaces contain gases CO2 and O2

13
Actual Leaf Cross-Section
14
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).

15
V. Leaf Coloration

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

16
Carotene orange

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

17
VI. Falling Leaves

• 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.

18
VII. Leaf Modifications - change in leaf
structure to better suit it to its environment.

• 1. Succulent leaves fleshy holds water.
• ex. Cactus, desert plants, aloe,conifers
• 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.
• ex. Venus flytrap

19
VIII. Plant Cells

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

20
IX. Plant Tissue Systems

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

21
X. Plant Growth

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