PLANTS

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Chapter 22-25
KINGDOM PLANTAE
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Plant Characteristics

• Multicellular
• Eukaryotic
• Cell walls made of cellulose
• Autotrophic
• Carries out photosynthesis using green pigment
  called chlorophyll
• Usually have large central vacuoles

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Non Vascular Plants Mosses (Bryophytes)

• Require damp environment
• Require water for reproduction
• Do not have true roots (have rhizoids instead)

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Vascular Seedless Plants Ferns (Pteridophytes)

• Largest group
• Usually live in moist environment
• Need water for fertilization
• Have true leaves, stems, and roots

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Vascular Seed Plants- GYMNOSPERMS

• Conifers do not require water for fertilization
• Wind carries the pollen from male cones to female
  cone where egg is fertilized.
• Zygote becomes embryo and ovule becomes seed
• Seeds produced in cones

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EXAMPLES
Fir
White Pine
Spruce
Cypress
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The giant redwoods (Notice the person in the
tree to your right.)
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Ancient GynmnospermWelwitschia spp.
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Other types of Gymnosperms
Gnetae
Ginko
Cycad
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While some gymnosperms lose their leaves, most
have needle-like leaves that they keep all year.
This is why they are referred to as evergreens.
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Vascular Seed Plants- ANGIOSPERMS
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• The most abundant and recent type of plants on
  Earth
• Have seeds that are protected by a fruit.

Passion flower and fruit
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• Divided into two groups monocots and dicots.
• Monocot seeds have one cotyledon (seed leaf).
  These are seeds that cannot be split in half,
  like a piece of corn.
• Dicots have two cotyledons. These seeds can be
  split in half like peanuts and beans.

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Monocots vs. Dicots
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EXAMPLES OF MONOCOTS
Lily
Flower parts usually in groups of three
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EXAMPLES OF DICOTS
Chrysanthemum
Petunia
Sunflower
Flower parts usually in groups of four or five
Trenia
Rose
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Vascular Tissue

• Xylem carries water and minerals upward in a
  plant.
• Water always moves in only one direction from
  the roots to the stems and leaves.
• Water evaporates from the plant through
  structures on the leaves called stomata (singular
  stoma).

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• Phloem carries the food of the plant.
• A plants food is sugar dissolved in a solution
  called sap.
• It carries sugars in two directions.
• Sugar can be carried from where it is made
  (usually the leaves) to where it is stored
  (usually stems and roots).

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ROOTSThere are two kinds of roots

• Taproots - a large, main, primary root.
• Example carrot

• Fibrous - branching, secondary roots.
• Example grasses

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• Water is absorbed into the plant by the process
  of osmosis.
• Water enters the root through the root hairs.
• Root hairs give the root more surface area so
  that it can absorb more water.
• The amount of
• water that is absorbed is dependent upon the
  amount of water in the soil.

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STEMS

• Stems typically have two main functions
• Supporting leaves and flowers
• Transporting water and food
• Some plant stems have the additional job of food
  storage. EX The potato is a special stem that
  stores starch.

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• Secondary growth is when the plant grows wider. .
  
• Cambium is the meristem tissue that allows plants
  to get wider.
• This secondary growth creates a layer of dead
  cells called wood.

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• The secondary phloem, cork cambium and the cork
  combine to form the bark of a tree.

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Trunk of an Oak Tree Notice the splits in the bark
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• As the xylem gets older, it becomes clogged and
  can no longer carry water. These dark-colored
  layers are known as heartwood. Heartwood is
  stronger and more resistant to decay than sapwood.

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• The alternation of spring and summer wood is what
  forms the trees growth rings.
• The wider the rings, the more favorable the
  conditions were for growth.
• The more narrow the rings, the poorer the
  conditions.

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Summer Wood
Spring Wood
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Annual Rings
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LEAVES

• The blade is the actual leaf.
• It attached to the stem by a thin structure
  called a petiole.
• The vascular tissue enters the leaf through the
  petiole and forms the veins of the leaf.

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• The top and the bottom of the leaf is covered by
  epidermis.
• The upper layer usually has a waxy layer known
  as a cuticle to prevent water loss.

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• Guard cells in the lower epidermis take in water
  and swell unevenly.
• This causes an opening to form between the guard
  cells.
• This opening is called the stoma.
• Stomata allow carbon dioxide to enter the leaf
  and oxygen and water vapor to diffuse out.

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• The mesophyll (middle layer) is where most of the
  photosynthesis takes place.

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Leaf Cross-Section
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Flowers

• The most common sexual reproductive structure is
  the flower. A perfect flower contains both male
  and female parts.

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• The male part of a flower is called the stamen.
• Formed by a filament which holds anther.
• The anther produces the pollen, which in flowers
  is the male gamete or sperm.

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• The female flower parts form the pistil, which is
  composed of a sticky top called the stigma, a
  neck called the style and a base called the
  ovary.
• The ovary contains the female gametes - egg or
  ovules.

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• The petals are usually colorful to attract
  pollinators.
• The sepals are protective green leaves at the
  base of a flower. They protect the bud before the
  flower blooms.

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• During pollination, pollen is transferred from
  the anther to the stigma. When a pollen grain
  lands on a stigma, it sends out a pollen tube
  that grows through the style to the ovary. Ovule
  fertilized by sperm.

Pollen Tube
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• The ovary will eventually develop into a fruit.
• The ovules will develop into seeds.

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• The job of a fruit is to protect the seeds and to
  sometimes help them be spread.
• The spreading of seeds is known as seed
  dispersal.
• Seeds can also be dispersed by wind, water,
  animals, and being carried away on fur or
  clothes.

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Modes of Seed Dispersal
Gravity              Animals              Force               Wind              Water
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PLANT RESPONSES

• Phototropism is the response of plants toward
  light.

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• Gravitropism is a plants response to gravity.
  This assures that roots grow down and stems grow
  up.

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• Thigmotropism is a response to touch. This allows
  a plant to grow on a surface that can support it.
  Whenever the stem touches the support, the cells
  on the opposite side of the stem grow longer,
  causing the stem to coil around or grasp a hold
  of the support.

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• The response of a plant to daylight length is
  called photoperiodism. It is actually a response
  to the hours of continuous darkness. A single
  flash of light during darkness can upset the
  cycle of some plants.

Long Night Short Night Long
Night Short Night
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Importance of plants?

• Food
• Fiber
• Fuel
• Construction
• Transport
• Medicine

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THE END