Download 26 -1 Plant Structure and Function

Rendell/Walz
Chapter 26 Plant Structure, Function, and Growth
26 -1 Plant Structure and Function
Key Words
Body of plants
Roots
Stems
Notes
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Roots
Stems
Leaves
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Anchor plant in ground
Draw water and minerals from soil
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Support body of plant
Carry water and nutrients from one end of plant to the
other.
Stabilize soil
Leaves
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Plant Tissue ( 3 types)
1. Dermal tissue – outer covering of plant; protects plant from
its environment and allows gases (oxygen and carbon
dioxide) to flow between plant and atmosphere.
Main organs of photosynthesis ( process by which plants
convert energy from sunlight into chemical energy)
2. Vascular tissue – makes up the fluid-conducting system of
the organism.
3. Ground tissue – provides most of plant’s supporting
strength and contains most of the cell that are active in
photosynthesis.
Plant Cells
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Parenchyma
 Thin-walled cells form bulk of tissue in roots, stems,
and leaves.
 In leaves – are active in photosynthesis
Collenchyma cells are in ground tissue
Sclerenchyma cells are in ground tissue
 Thick walls of these cells provide strong support for
plant
Xylem – vascular cell carries water
Phloem – carries sugars and other food through out plant.
26 -1 continued
Roots ( see text p. 604)
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Collect nutrients and water
Help provide support for the portion of the plant that is
above ground.
Epidermis – outer covering of root
 Root hairs - tiny thin-walled projections make direct
contact with soil
 Responsible for most of root’s surface area
 Plants absorb water and nutrients directly through
root hairs.
Cortex – spongy cells beneath epidermis
 Parenchyma cells of root cortex - important in
moving water from epidermis to vascular tissue
near center of root.
Vascular cylinder – central region of xylem and phloem
cells – carries water and nutrients
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Osmosis – movement of water across a membrane.
Active transport
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Active transport – brings minerals across cell membrane
of root hair; use ATP to pump mineral ions across
membrane
Casparian Strip
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Casparian Strip – controls the passage of water and
mineral ions into and out of the vascular cylinder of the
root; waxy layer.
Endodermis layer of cells in the inner boundary of cortex
 Form tight layer that separates cortex from vascular
cylinder
How Roots Work
Osmosis
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Stems
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Connect the roots that gather water and nutrients with the
leaves that carry out photosynthesis
Surrounded by layer of epidermal cells
Contain ground tissue and vascular tissue
Monocots – vascular bundles (xylem and phloem) are
scattered through the ground tissue
Dicots – vascular bundles arranged in a ring
Pith – ground tissue inside the ring
Cortex – ground tissue outside the ring
Vascular Cambium
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Layer of rapidly dividing cells in stems
Annual tree rings
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Concentric circles in stem of tree formed as a result of
seasonal variations in the production of xylem
Leaves
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Main organs where plants carry out photosynthesis
Outer covering of epidermal cells
 Covered with waterproof waxy layer called cuticle
 Protects leaf against water loss and insect invasion
Fluid carrying vascular tissue
Ground tissue consisting of parenchyma cells
Attached to stems by thin structure – petiole.
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26 -1 continued
Key Word(s)
Stomata
Mesophyll Tissue
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Leaf Veins – Vascular Tissue
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Fluid Transport
Xylem Transport
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Phloem Transport
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Notes
Small openings on the underside of leaf
Open up during periods of rapid photosynthesis to allow
CO2 to enter leaf
Found in ground tissue of most leaves
Packed with chloroplasts – cells that perform most of
plant’s photosynthesis.
Two types:
1. palisade cells – tall cells
2. spongy cells – have air spaces
xylem cells carry water into leaf
osmosis carries water from cell to cell within leaf
phloem tissue carries the products of photosynthesis from
leaf to rest of plant
xylem and phloem found in vascular bundles – veins
monocots – veins run parallel
dicots – veins form branched network
Capillary action – force that draws upward from roots into
stems of vascular plants.
Transpiration – process by which leaves lose water vapor
Combination of active transport and osmosis – pressure
flow hypothesis- is believed to transport sugars through
plant’s phloem tissue.
26 – 2 Plant Growth
Tropisms
Key Word(s)
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Notes
Plants grow in response to cues from environment
Responses are known as tropisms (to turn).
Geotropism
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Response of an organism to the force of gravity
Roots turn toward force of gravity
Stems grow away from force of gravity
Phototropism
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Ability of plants to grow in response to light
Thigmotropism
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Plants response to touch
Plant hormones
1. Auxins
 stimulate cell grow
 Produced by cells in apical meristem (rapidly
growing region near tip of root or stem)
 Produce phototropism and geotropism
2.
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Cytokinins
Affect rates of plant growth and cell division
Many effects are opposite those of auxins
Produced by cells throughout plant
Like adenine found in bases of DNA and RNA
3. Gibberellin
 Regulates stem elongation
4. Ethylene
 Stimulate ripening process (in response to an auxin)
Plant Life Cycles
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Annuals – live a single year
Biennals – flower and produce seeds in second year of
life
Perennials – plants that live for more than two years
Phytochrome red pigment used by plants to sense day
and night; master timing switch
Abscisic acid – hormone regulated by phytochrome