Chapter 24 Seed Plant Structure and...
Transcript of Chapter 24 Seed Plant Structure and...
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Biology II
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Vascular plants have 3 tissue systems:
Dermal
Protective outer layer of plant
Vascular
Forms strands that conduct water, minerals, and
organic compounds
Ground
Much of the inside of nonwoody parts of plants
Includes roots, stems, and leaves
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Green – Ground
Purple – Vascular
Tan - Dermal
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Covers outside of plant’s body
Forms “skin” called epidermis
Made up of single layer of flat cells in most
plants
Often have hair-like extensions to slow water
loss by trapping moisture
Called root hairs – help increase water
absorption
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Waxy cuticle protects epidermis of stems and leaves
Also prevents water loss
Made it possible for plants to live in drier
environments
Water lilies also have cuticle – protects leaves and repel
water
Cork – on woody stems and roots
Several layers of dead cells
Contains a waterproof material – not covered by cuticle
Functions in gas exchange and absorption of mineral
nutrients in addition to protection
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Stomata, singular stoma permits plants to exchange
oxygen and carbon dioxide (since the cuticle does not)
Extend through cuticle and outer layer of cells
Found on at least some parts of most plants
Guard cells border each stoma
Stomata open to gain CO2 from air – also loses water
this way
When closed, plant conserves water, but photosynthesis
slows (shortage of CO2)
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Why does photosynthesis
slow down when stomata
are closed?
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Two kinds of vascular tissue
Xylem
Phloem
Composed of cells that are stacked end to
end like sections of pipe
Allow most vascular plants to grow much
larger than nonvascular plants
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Composed of thick-walled cells that conduct water and mineral
nutrients from a plant’s roots through its stems to its leaves
At maturity, cells are dead – still has strong cell walls
Conducting cells
Tracheids
Water flows from one to the next through pits, or thin
areas in cell walls
Vessel elements
Link to form vessels
Have large perforation in ends that allow water to flow
quickly between elements
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Made up of cells that conduct sugars and nutrients throughout a
plant’s body
Cells have cell wall, cell membrane, and cytoplasm
Lack organelles or have modified organelles
Conducting cells
Sieve-tube members
Link to form sieve tubes
Pores in walls connect the cytoplasms and allow
substances to pass from cell to cell
Companion cells
Contain organelles
Carry out cellular respiration, protein synthesis, and
other metabolic functions
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Makes up much of the inside of nonwoody plants
Surrounds and supports vascular tissue
Most consists of thin-walled cells that remain alive and keep
their nucleus after maturity
Also contains some that do the opposite (die, thick-walled cells)
Contain many specialized structures
In leaves – packed with chloroplasts
In stems and roots – vacuoles (water storage)
In angiosperms, makes up flesh of fruits
Largely absent in woody parts of plants
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Roots, stems, and leaves contain all
three tissue types
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Anchor plants
Absorb water and nutrient minerals
Can function in storage of sugar and starch (organic)
Monocots – highly branched, fibrous roots
Dicots – central root, called taproot system
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Has central core of vascular tissue surrounded by ground tissue
Ground tissue surrounding vascular tissue called cortex
Roots covered by dermal tissue
Epidermis covers all of root except root tip
Epidermal cells behind root tip often produce root hairs
Increase surface area
Roots hairs = extensions of epidermal cells
Mass of calls called root cap covers and protects root tip
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Stems support leaves and house vascular tissue
Can be specialized for other functions
Stems of cacti store water
Potatoes stores nutrients
Leaves attach to stems at nodes
Internode – space between two nodes
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Herbaceous plants – have stems that are flexible and usually
green
Vascular bundles – bundles of xylem and phloem
Surrounded by ground tissue
In dicots, bundles are in a ring
Ground tissue outside of bundles is called cortex
Pith = ground tissue inside bundles
Covered by epidermis
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Stiff and nongreen
Buds produce new growth, are found at the tips of nodes
Young has central core of pith and a ring of vascular bundles
Fuse into solid cylinders as stem matures
Layers of xylem form innermost cylinder – major component of wood
Phloem lies outside cylinder of xylem
Covered by cork – protect from damage and water loss
Cork and phloem make of layers(bark) of woody stem
Wood in center is called heartwood
Provides support but no longer conducts water
Sapwood outside heartwood
Contain vessel elements that can conduct water
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Primary photosynthetic organs of plants
Most have flattened portion called blade
Attached to stem by a stalk, called petiole
can be divided into 2+ sections called leaflets
Undivided leaves are simple leaves
2+ leaflets are compound leaves
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Leaf is mass of ground tissue covered by epidermis
Cuticle coats upper and lower
Xylem and phloem found in veins of leaves
Veins are extensions of vascular bundles that run from tips of roots to
edges of leaves
In leaves, ground tissue is called mesophyll
Packed with chloroplasts
Most plants have 2 layers of mesophyll
Palisade layer – closely packed, columnar cells
Spongy layer – loosely packed cells
Stomata usually located in lower epidermis of leaf
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Water lily – specialized for floating
Stomata on upper surface
Cactus – modified as spines
Protect plant from herbivores
Garden pea – form tendrils that climb
Venus flytrap – can catch insects
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Seed develops from ovule and contains a plant embryo
Embryo contains embryonic root and embryonic shoot
Cotyledons, or seed leaves are attached to embryonic shoot
Gymnosperm embryos =2+ cotyledons
Angiosperms = monocot 1, dicot 2
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Embryo within seed is in dormancy
Can remain in dormancy for thousands of years
Germination – process of plant embryo resuming growth
1st sign – emergence of root
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Sprout in response to certain changes in environment
Rising temp, soil moisture, sometimes cold, fire, passing through
digestive system of animal, falling onto a rock
Must have water and oxygen penetrate seed coat
Allows seed to swell and breaks seed coat
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Part of plant’s body that grows mostly
upward is shoot
Part that grows down = root
Meristems – active regions of growth
Made of undifferentiated cells, develop
into specialized tissues
Primary growth – increases length of
height
Result in primary tissues
Secondary growth – increases width of
stems and roots
Result in secondary tissues
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Apical meristems – located at the tips of stems and roots
Produce primary growth via cell division
Differentiate into roots, stems, and leaves
Each plant has 2 – one at the tip of the embryonic root, and one at tip of
embryonic shoot
Makes stems and roots get longer, not wider
Primary growth would end if all cells in apical meristem
differentiated
Undifferentiated cells are left behind to produce new meristems
New meristems found at buds at base of leaves and within roots
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Some undifferentiated cells left behind as stems and roots
lengthen to produce lateral meristems
Responsible for increase in width of stems and roots
Called secondary growth
Most dramatic in woody plants
Produced by cell division in two lateral meristems
Form thin cylinders near outside of woody stems and roots
Cork cambium – lies within the bark and produces cork cells
Vascular cambium
Lies just under bark and produces secondary xylem and
secondary phloem