Leaves

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Leaves

• Horticulture 1

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What are the functions of leaves?

• Capture light
• Exchange gases
• Provide a site for photosynthesis
• Some leaves store food and water
• Some form new plants and provide support

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Why does a plant need photosynthesis?

• PHOTO means light
• SYNTHESIS means to make or form something from
• SO.Photosynthesis is a plant making something
  (food) from light.

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Photosynthesis definition

• a process by which plants combine water and
  carbon dioxide in the presence of chlorophyll and
  sunlight and produce carbohydrates and release
  oxygen.

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Why is photosynthesis important?

• Light is the most important source of energy for
  living things. Photosynthesis converts light
  into nutrients that can be used by plants and
  animals.
• Releases oxygen

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Recipe for Photosynthesis

• 6CO2 12H2O sunlight gt
• 6O 2 C6 H12O 6 6H2 OOr in English
• Carbon Dioxide Water in Sunlight gt
• Oxygen Sugars/Food Water

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There are two parts of photosynthesis--the light
and dark reactions.

• The light reactions produce chemical energy from
  light.
• The dark reactions convert carbon dioxide into
  carbohydrates.

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Leaves gas exchange

• Oxygen, Carbon Dioxide, and Water exchanged from
  Stomata
• Pores (stomata) open in day to transpire H2O and
  allow gases to enter
• Close during dry conditions to prevent H2O loss.

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1. Leaves External Parts
A. Petiole- leaf stalk or part that connects leaf
to stem.
Petiole
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B. Blade- the large, flat part of a leaf.
C. Midrib- the large center vein.
Midrib
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D. Veins- the structural framework of leaf. Act
like pipes to carry water nutrients
Veins
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E. Margin- the edge of leaf.
Margin (edge of the leaf)
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• F. Cutin fatty (waxy) substance in many plant
  cell walls on outer surface of epidermal cell
  walls
• - forming a Cuticle a protective covering on
  a green leaf that helps hold in moisture
• (this gives the leaf a glossy appearance)

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G. Stipule tiny leaf-like structures at the
base of a petioleH. Axil the angle made by
the petiole and the stem of the plant.
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Leaves Internal Parts
A. Upper and lower epidermis- skin of the leaf
that prevents the loss of too much moisture.
B. Stomates- small openings under the leaf for
breathing or transpiration (also called stoma or
stomata)
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(Internal Parts-continued)
C. Guard cells- open and close stomates
D. Chloroplasts- small green particles that
contain chlorophyll, give leaves their green
color and are necessary for photosynthesis