LeavesLeaves

23.1.1 Describe the organs and tissues of 23.1.1 Describe the organs and tissues of vascular plants.vascular plants.

23.1.2 Identify the specialized cells of 23.1.2 Identify the specialized cells of vascular tissue.vascular tissue.

23.1.3 contrast meristematic tissue with other 23.1.3 contrast meristematic tissue with other plant tissues.plant tissues.

3 principal organs and tissues 3 principal organs and tissues of seed plantsof seed plants

RootsRoots Absorbs water and dissolved nutrients. Anchor plants in the ground Protect plants from harmful soil bacteria and fungi Transport water and nutrients to the rest of the plant

StemsStems Has a: support system- for the plant body, transport

system-carries nutrients, and a defense system-protects the plant against predators and disease.

LeavesLeaves Main photosynthetic systems Help conserve water while letting oxygen and carbon

dioxide enter and exit the leaf.

Dermal tissue

Vascular tissue

Ground tissue

Stem

Root

Leaf

Figure 23–1 Page 580Figure 23–1 Page 580Root, Stem, and Leaf TissuesRoot, Stem, and Leaf Tissues

What are the 3 principal plant organs?

Leaves, stems, and roots

Which tissue is found in the center of a plant stem?

Ground tissue

Three main tissue systems

Concept MapConcept Map

include

includes includes includes

includes includes

Section 23-1

Plant Tissues

Dermaltissue

Meristematictissue

Vasculartissue

Groundtissue

Epidermalcells Xylem Phloem Parenchyma

cellsCollenchyma

cellsSchlerenchyma

cells

Tracheids Vesselelements

Sieve tubeelements

Companioncells

RootsRoots 2 main types2 main types

TaprootsTaproots Primary root that grows thicker and longer than othersPrimary root that grows thicker and longer than others Example: carrots, dandelions, beets, and radishesExample: carrots, dandelions, beets, and radishes

FibrousFibrous Branch to such an extent that no single root grows Branch to such an extent that no single root grows

larger than the restlarger than the rest Example: grassesExample: grasses

How do roots help prevent erosion?How do roots help prevent erosion? Extensive, branching fibrous roots hold soil in place.Extensive, branching fibrous roots hold soil in place.

Section 23-2

Epidermis

Ground tissue(cortex)

VascularCylinder

Cross Section of Plant Root(magnification: 40x)

Ground tissue (cortex)

Epidermis

Endodermis

Vascular cylinder

Root hairs

Phloem

Xylem

Apical meristem

Root cap

Zone of maturation

Zone of elongation

Endodermis

Figure 23–7 The Structure of a Figure 23–7 The Structure of a RootRoot

StemsStems

3 functions3 functions Produce leaves, branches, and flowers Hold leaves up to the sunlight They transport substances between roots and

leaves

LeavesLeaves23-423-4

ObjectiveObjective23.4.1 Describe how the structure of a 23.4.1 Describe how the structure of a

leaf enables it to carry out leaf enables it to carry out photosynthesis.photosynthesis.

23.4.2 Describe how gas exchange 23.4.2 Describe how gas exchange takes place in a leaf.takes place in a leaf.

Read Pages 595-598Read Pages 595-598

What is the main function of a plant’s leaf?What is the main function of a plant’s leaf? The leaves of a plant are its main organs of The leaves of a plant are its main organs of

photosynthesis.photosynthesis. How does the structure of a leaf enable it to How does the structure of a leaf enable it to

carry out photosynthesis?carry out photosynthesis? The structure of a leaf is optimized for The structure of a leaf is optimized for absorbing light and carrying out absorbing light and carrying out photosynthesis.photosynthesis. How does gas exchange take place in a leaf?How does gas exchange take place in a leaf? Plants leaves allow gas exchange by opening Plants leaves allow gas exchange by opening

their stomata.their stomata.

Leaf FunctionsLeaf Functions

PhotosynthesisPhotosynthesis Transpiration Transpiration

the loss of water through its leavesthe loss of water through its leaves Gas ExchangeGas Exchange

Plants keep their stomata open just enough to Plants keep their stomata open just enough to allow photosynthesis to take place but not so much allow photosynthesis to take place but not so much that they lose an excessive amount of water. that they lose an excessive amount of water.

StomataStomata - - Porelike openings in the underside of the leaf that allow carbon dioxide and oxygen to diffuse in and out of the leaf. Each stomata has 2 guard cells.

Guard Cells - epidermal cells found on the underside of leaves that control the opening and closing of the stomata by responding to changes in water pressure. Also, responds to conditions in the environment, such as wind and temperature.

StomataStomata When the guard cells are swollen with When the guard cells are swollen with

water, the stomata is opened.water, the stomata is opened. When the guard cells lose water, the When the guard cells lose water, the

stomata closes.stomata closes. Are open during the daytime, when photosynthesis is Are open during the daytime, when photosynthesis is

active.active. Are closed at night to prevent water loss.Are closed at night to prevent water loss. May be closed during bright sunlight under hot, dry May be closed during bright sunlight under hot, dry

conditions in which the plant needs to conserve water conditions in which the plant needs to conserve water to survive.to survive.

Stoma Open Stoma Closed

Guard cells

Inner cell wall

Stoma

Guard cellsInner cell wall

Function of Guard CellsFunction of Guard Cells

Section 23-4

Stoma Open Stoma Closed

Guard cells

Inner cell wall

Stoma

Guard cells Inner cell wall

Function of Guard CellsFunction of Guard Cells

What factor regulates the opening and closing of stomata? Changes in water pressure

within guard cells