Transcript Leaves 23-4 - SCHOOLinSITES

Leaves
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23.1.1 Describe the organs and tissues of
vascular plants.
23.1.2 Identify the specialized cells of
vascular tissue.
23.1.3 contrast meristematic tissue with other
plant tissues.
3 principal organs and tissues
of seed plants
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Roots
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Stems
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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
Has a: support system- for the plant body, transport systemcarries nutrients, and a defense system-protects the plant
against predators and disease.
Leaves
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Main photosynthetic systems
Help conserve water while letting oxygen and carbon
dioxide enter and exit the leaf.
Figure 23–1 Page 580
Root, Stem, and Leaf Tissues
What are the 3
principal plant
organs?
Leaves, stems,
and roots
Leaf
Stem
Which tissue is
found in the center
of a plant stem?
Ground tissue
Root
Dermal tissue
Vascular tissue
Ground tissue
Three main tissue systems
Concept Map
Section 23-1
Plant Tissues
include
Dermal
tissue
Meristematic
tissue
includes
Epidermal
cells
Ground
tissue
includes
Xylem
includes
Tracheids
Vascular
tissue
Vessel
elements
includes
Phloem
Parenchyma
cells
includes
Sieve tube
elements
Companion
cells
Collenchyma
cells
Schlerenchyma
cells
Roots
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2 main types
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Taproots
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Fibrous
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Primary root that grows thicker and longer than others
Example: carrots, dandelions, beets, and radishes
Branch to such an extent that no single root grows larger
than the rest
Example: grasses
How do roots help prevent erosion?
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Extensive, branching fibrous roots hold soil in place.
Figure 23–7 The Structure of a
Root
Section 23-2
Epidermis
Endodermis
Root hairs
Ground tissue
(cortex)
Phloem
Xylem
Vascular
Cylinder
Ground tissue (cortex)
Epidermis
Endodermis
Vascular cylinder
Zone of
maturation
Zone of
elongation
Apical meristem
Cross Section of Plant Root
(magnification: 40x)
Root cap
Stems
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3 functions
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Produce leaves, branches, and flowers
Hold leaves up to the sunlight
They transport substances between roots and
leaves
Leaves
23-4
Objective
23.4.1 Describe how the structure of a leaf
enables it to carry out photosynthesis.
23.4.2 Describe how gas exchange takes
place in a leaf.
Read Pages 595-598
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What is the main function of a plant’s leaf?
The leaves of a plant are its main organs of
photosynthesis.
How does the structure of a leaf enable it to
carry out photosynthesis?
The structure of a leaf is optimized for
absorbing light and carrying out
photosynthesis.
How does gas exchange take place in a leaf?
Plants leaves allow gas exchange by opening
their stomata.
Leaf Functions
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Photosynthesis
Transpiration
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the loss of water through its leaves
Gas Exchange
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Plants keep their stomata open just enough to
allow photosynthesis to take place but not so much
that they lose an excessive amount of water.
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Stomata - Porelike openings in the underside
of the leaf that allow carbon dioxide and
oxygen to diffuse in and out of the leaf.
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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.
Stomata
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When the guard cells are swollen with water, the
stomata is opened.
When the guard cells lose water, the stomata
closes.
Are open during the daytime, when photosynthesis is
active.
Are closed at night to prevent water loss.
May be closed during bright sunlight under hot, dry
conditions in which the plant needs to conserve water
to survive.
Function of Guard Cells
Guard cells
Guard cells
Inner cell wall
Inner cell wall
Stoma
Stoma Open
Stoma Closed
Function of Guard Cells
Section 23-4
Guard cells
Guard cells
Inner cell wall
Stoma
Stoma Open
Stoma Closed
What factor regulates the opening
and closing of stomata?
Changes in water pressure
within guard cells
Inner cell wall