Chapter 23 Plant Structure and Function

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Chapter 23 Plant Structure and Function
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Plant Tissue

• Vascular Plants have four basic types of tissue
• Vascular tissue
• Ground tissue
• Epidermis
• Meristematic Tissue

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Plant Tissue

• Vascular Tissue
• Xylem transports water and minerals
• Phloem transports sugars
• Ground tissue surrounds the vascular tissue
  some store water or sugars, others lend support
  to the plant

• Epidermis layer of flattened cells secrete the
  waxy cuticle
• Meristems regions of actively dividing cells
  found in ares that are growing

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ROOTS

• Roots - anchor plant to the ground and absorb
  water and minerals. Make up 1/3 of weight of a
  plant.
• Absorption actually takes place in the root
  hairs. Increases the surface area of a root.
• Growth of a root takes place in a root cap by
  cell division.
• Some roots have specialized functions like food
  or water storage.

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STEMS

• Shoots - made up of the stem and leaves. In some
  cases, it also includes the flowers and fruits.
• Stems support the leaves so they can capture
  sunlight.
• Stems also connect the roots to the leaves and
  contain the vascular tissue needed for transport
  of water and minerals.
• Stems can be modified for storage.

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LEAVES

• Leaves are the main sites for photosynthesis.
• Leaves contain chloroplasts which contain the
  chlorophyll needed for photosynthesis.

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LEAVES

• Thin and Flat advantageous for photosynthesis
• Cuticle - leaves contain a waxy outer layer that
  prevents it from losing too much water.
• Stomata tiny pores that allow carbon dioxide to
  enter and water and oxygen to exit

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LEAVES

• Inside a leaf are
• layers of photosynthetic cells
• Bundles of vascular tissue (veins in leaves)
• Xylem
• Phloem

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How Plants Function

• Transpiration - Water Movement in Plants
• occurs in Xylem
• Translocation - Food Movement in Plants
• Occurs in phloem
• Growth and Plants Hormones
• Other (Sunlight, Temperature, and Gravity)

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Water Movement in Plants

• Water travels from
• roots ? trunk/stem ? leaves
• Travels to all the parts of the plant through the
  xylem.
• Direct result of Transpiration in Plants

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Transpiration

• The loss of water vapor from a plant through its
  stomata
• More than 90 of water entering plant passes
  through plant and evaporates through the stomata

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Stomata and Transpiration

• Stomata - Specialized pores located in plant
  cuticle that enables plant to exchange gases with
  the atmosphere

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Stomata and Transpiration

• Two guard cells surround the stomatal pore and
  control the opening and closing of the stomata.

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The Role of Stomata

• Gas Exchange
• The plant must open stomatal pore during
  photosynthesis to allow CO2 inside the plant and
  O2 out.

• Evaporation
• Helps cool the plant but sometimes the
  transpiration is so rapid that the loss of water
  begins to exceed the intake and the stomata may
  close to prevent wilting.

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Transpirational Pull

• As transpiration takes place, it creates a pull
  or tension drawing water from the xylem and
  ultimately from the soil

• When plants transpire, the water potential in
  cells adjacent to the stomata drop because they
  lose water into the atmosphere. This cause a
  chain reaction which pulls water from other cells
  eventually pulling water from the xylem, root,
  and soil.

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Translocation

• The transport of nutrients (food) formed during
  photosynthesis within the phloem to all parts of
  the plant.

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Flow of Materials in Plants
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Plant Growth

• Primary Growth Growth that lengthens
• Meristems region where plants grow using cell
  division, this growth occurs in the tips of roots
  and shoots and enable the plant to grow in length
• Secondary Growth - Growth that thickens
• Woody plants (trees and shrubs) thicken by
  producing xylem and phloem. Rings of a tree are
  layers of xylem and phloem

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Plant Hormones

• Auxin - produced in the tips of stems, causes
  cell walls to become more flexible
• If a stimulus causes auxin to concentrate more on
  one side of a stem, the cells on that side will
  elongate. Thus, the stem grows toward light.

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Plant Hormones

• Gibberellin
• Stimulate cell division, elongation, and the
  sprouting of seeds.
• Ethylene
• Stimulates fruit ripening. Also promotes the
  dropping of leaves, flowers, and fruits.

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Other Factors - Tropism

• Photoperiodism the response of plants to
  periods of light and dark
• Geotropism response of plant to gravity
• Helps plant determine which way to grow roots.
• Thigmotropism response of plants to touch
• Helps climbing plants find support structures