Transcript 21.1 Plant Cells and Tissues TEKS 5B, 10B, 10C

21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
KEY CONCEPT
Plants have specialized cells and tissue systems.
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
Plant organs are made of three tissue systems.
• Dermal tissue covers the outside of a plant.
– protects the plant
– secretes cuticle of leaves
– forms outer bark of trees
21.1 Plant Cells and Tissues
• Ground tissue is found inside a plant.
– provides support
– stores materials in roots and stems
– most commonly made of parenchyma
TEKS 5B, 10B, 10C
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
• Vascular tissue transports water, minerals and organic
compounds.
– two networks of hollow
tubes
– xylem transports water
and minerals
– phloem transports
photosynthetic products
stem
leaf
root
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
Water and dissolved minerals move through xylem.
• Xylem contains specialized cells.
– vessel elements are short and wide
– tracheid cells are long and narrow
– xylem cells die at maturity
tracheid
vessel
element
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
• The cohesion-tension theory explains water movement.
– Plants passively transport water through the xylem.
– Cohesion is the tendency of water molecules to bond
with each other.
– Adhesion is the
tendency of water
molecules to bond
with other
substances.
21.1 Plant Cells and Tissues
• Water travels from roots to the top of trees.
– absorption occurs at roots
– cohesion and adhesion in xylem
– transpiration at leaves
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21.1 Plant Cells and Tissues
• Transpiration is the loss of water
vapor through leaves.
– water vapor exits leaf stomata
– helps pull water to the top
branches
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21.1 Plant Cells and Tissues
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Phloem carries sugars from photosynthesis throughout
the plant.
• Phloem contains specialized cells.
– sieve tube elements have
holes at ends
– companion cells help sieve
tube elements
– unlike xylem, phloem tissue is
alive
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
• The Pressure-flow model explains sugar movement.
– plants actively transport sugar from the source
– sugar flows to the sink due to pressure differences
phloem
xylem
sugars
1 Sugars move from their
source, such as
photosynthesizing
leaves, into the phloem.
3 The sugars move into
the sink, such as root
or fruit, where the are
stored.
water
2 Water moves from
the xylem into the
phloem by osmosis,
due to the higher
concentration of the
sugars in the phloem.
The water flow helps
move sugars through
the phloem.
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
Most leaves share some similar structures.
• The blade is usually broad and
flat.
– collects sunlight for
photosynthesis
– connects to the stem by a
petiole
blade
petiole
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
• Mesophyll is between the leaf’s dermal tissue layers.
cuticle
upper
epidermis
palisade
mesophyll
spongy
mesophyll
lower
epidermis
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
• Guard cells surround each stoma.
– Stomata open and close when guard cells change
shape.
– When stomata are open, water evaporates and gas
exchanges.
– Stomata close at night and when plant loses too much
water.
guard cells
stoma
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
• Leaves may be simple, compound, or double compound.
Simple leaf
Compound leaf
Double compound leaf
21.1 Plant Cells and Tissues
• Leaf veins may be parallel or pinnate.
Parallel veins
Pinnate veins
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21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
• Leaf margins may be toothed, entire, or lobed.
Toothed margin
Entire margin
Lobed margin
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
Most leaves are specialized systems for photosynthesis.
• There are two types of mesophyll cells.
– both types contain chloroplasts
– palisade mesophyll absorbs sunlight
– spongy mesophyll connects to stomata
cuticle
upper
epidermis
palisade
mesophyll
xylem
spongy
mesophyll
phloem
lower
epidermis
stomata
21.1 Plant Cells and Tissues
• Leaves have many adaptations.
– for extreme temperatures,
ex: pine needles
TEKS 5B, 10B, 10C
21.1 Plant Cells and Tissues
• Leaves have many adaptations.
– for extreme temperatures,
ex: pine needles
– for water loss,
ex: cactus spines
TEKS 5B, 10B, 10C
21.1 Plant Cells and Tissues
• Leaves have many adaptations.
– for extreme temperatures,
ex: pine needles
– for water loss,
ex: cactus spines
– for aquatic environments,
ex: water lily
TEKS 5B, 10B, 10C
21.1 Plant Cells and Tissues
• Leaves have many adaptations.
– for extreme temperatures,
ex: pine needles
– for water loss,
ex: cactus spines
– for aquatic environments,
ex: water lily
– for getting food,
ex: Venus’ flytrap
TEKS 5B, 10B, 10C
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
Roots anchor plants and absorb mineral nutrients from
soil.
• Roots provide many
functions.
– support the plant
– absorb, transport,
and store nutrients
– root hairs help
absorption
21.1 Plant Cells and Tissues
• There are several parts of a root.
– root cap covers the tip
root
cap
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21.1 Plant Cells and Tissues
• There are several parts of a root.
– root cap covers the tip
– apical meristem is an area
of growth
apical
meristem
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21.1 Plant Cells and Tissues
• There are several parts of a root.
– root cap covers the tip
– apical meristem is an area
of growth
– vascular cylinder contains
xylem and phloem
vascular
cylinder
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21.1 Plant Cells and Tissues
• There are two main types of roots.
– Fibrous root systems have fine branches.
– Taproot systems have one main root.
Fibrous
root
Taproot
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21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
Stems support plants, transport materials, and provide
storage.
• Stems have many functions.
– support leaves and flowers
– house most of the vascular system
– store water
Baobab
Cactus
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
Stems support plants, transport materials, and provide
storage.
• Stems have many functions.
– support leaves and flowers
– house most of the vascular system
– store water
– grow underground for storage
Ginger
Potato
21.1 Plant Cells and Tissues
TEKS 5B, 10B, 10C
Stems support plants, transport materials, and provide
storage.
• Stems have many functions.
– support leaves and flowers
– house most of the vascular system
– store water
– grow underground for storage
– form new plants
Straw
berry
21.1 Plant Cells and Tissues
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• Some stems are herbaceous and conduct photosynthesis.
21.1 Plant Cells and Tissues
• Some stems can be woody,
and form protective bark.
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21.1 Plant Cells and Tissues
• Primary growth increases a plant’s length.
• Secondary growth increases a plant’s width.
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21.1 Plant Cells and Tissues
• Tree rings help determine the age of a tree.
bark
bands
heartwood
one
year
of
growh
sapwood
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