Plants: Leaves

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Plants Leaves
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Leaves

• Play role in photosynthesis, gas exchange,
  storage, and protection from predators.
• Leaf cells absorb energy from sunlight in a
  chloroplast which contains photopigments.
• Photopigments are chemicals that absorb
  particular wavelengths of red and blue light and
  reflect green light.

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Leaf Structure

• Make sugar and supplies all living organisms with
  food and oxygen
• Designed so they can capture the most amount of
  sunlight.
• Covered with a waxy cuticle that is produced by
  the epidermis. Both provide protection.
• Stomata are little passages on the underside of
  leaves that allow for gas and water vapour
  exchange. Woody plants have no stomata on the
  upperside, herbaceous plants do have stomata on
  the upperside.
• Stomata are open during the day and closed at
  night

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• Carbon dioxide is used by chloroplasts to perform
  photosynthesis
• Carbon dioxide is brought into the plant through
  the stoma, while oxygen and water are released
  into the atmosphere.
• Photosynthesis cannot happen at night, so the
  stomata are closed.
• Each stoma is surrounded by two guard cells that
  are kidney-shaped, specialized epidermal cells
  with chloroplasts
• Water moves into the guard cells during the day
  because of all the ions that move into the cells.
• The inside is thicker, so the outside can expand
  more, creating a hole between the two cells.

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• Cells within the leaf are the mesophyll cells
  that have a lot of chloroplasts and have two
  layers
• Palisade layer that are densely packed and have
  more chloroplasts
• Spongy layer that are loosely spaced so air can
  come in contact with the cells.
• Water loss from the leaves through evaporation is
  called transpiration
• The xylem and phloem continue from the stems into
  the leaves in special vascular bundles called
  veins.
• Monocot veins run parallel to each other
• Dicot veins run in a branching network

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Leaf Specializations

• Dry climate thicker cuticle, stomata on
  underside.
• Cactus leaves are modified into spines
• Aquatic plants have stomata on the upperside for
  gas exchange.
• Onion bulb stores water and carbs

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Leaf Uses

• Provide important nutrients and food energy in
  the diets of humans.
• Use them for herbs and spices
• Teas
• They are nutritious (calcium, potassium, iron,
  magnesium, vitamins B, C, E, K)
• Use waxy cuticle for polishes, cosmetics,
  candies.

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Leaves and Chemicals

• Leaves produce chemicals that humans have used in
  the past and present as medicinal.
• Research one medicinal plant and report on what
  it is used for as homework tonight