KEY CONCEPT Plants have specialized cells and tissue systems.

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KEY CONCEPT Plants have specialized cells and
tissue systems.
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Plant tissues are made of three basic cell types.

• Parenchyma cells are the most common plant cell
  type.
• store starch, oils andwater
• help heal wounds tothe plant
• have thin flexible walls

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• Collenchyma cells provide support to a growing
  plant.

• they are strong and flexible.
• celery strings are strands of collenchyma.
• they have unevenly thick cell walls.

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• Sclerenchyma cells are the strongest plant cell
  type.

• second cell wall hardened by lignin
• die when they reach maturity
• used by humans to make linen and rope

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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

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• Ground tissue is found inside a plant.

• provides support
• stores materials in roots and stems
• most commonly made of parenchyma

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• Vascular tissue transports water, minerals and
  organic compounds.

• two networks of hollow tubes
• xylem transports water and minerals
• phloem transports photosynthetic products

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KEY CONCEPT 20-2 The vascular system allows for
the transport of water, minerals, and sugars.
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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

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• 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.

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• 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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• 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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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

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• The Pressure-flow model explains sugar movement.

• plants actively transport sugar from the source
• sugar flows to the sink due to pressure
  differences

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KEY CONCEPT 21.3 Roots and stems form the
support system of vascular plants.
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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

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• There are several parts of a root.

• root cap covers the tip

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• There are several parts of a root.

• There are several parts of a root.

• root cap covers the tip

• apical meristem is an area of growth

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• There are several parts of a root.

• 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

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• There are two main types of roots.

• Fibrous root systems have fine branches.

• Taproot systems have one main root.

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Stems support plants, transport materials, and
provide storage.

• Stems have many functions.
• support leaves and flowers
• house most of the vascular system
• store water

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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

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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

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• Some stems are herbaceous and conduct
  photosynthesis.

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• Some stems can be woody, and form protective
  bark.

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• Primary growth increases a plants length.

• Secondary growth increases a plants width.

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• Tree rings help determine the age of a tree.

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KEY CONCEPT Leaves absorb light and carry out
photosynthesis.
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Most leaves share some similar structures.

• The blade is usually broad and flat.
• collects sunlight for photosynthesis
• connects to the stem by a petiole

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• Mesophyll is between the leafs dermal tissue
  layers.

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• 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.

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• Leaves may be simple, compound, or double
  compound.

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• Leaf veins may be parallel or pinnate.

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• Leaf margins may be toothed, entire, or lobed.

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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

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• Leaves have many adaptations.

• for extreme temperatures, ex pine needles

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• Leaves have many adaptations.

• for extreme temperatures, ex pine needles

• for water loss,ex cactus spines

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• Leaves have many adaptations.

• for extreme temperatures, ex pine needles
• for water loss,ex cactus spines

• for aquatic environments, ex water lily

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• 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