Roots, Stems and Leaves

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Roots, Stems and Leaves

• Chapter 23
• Biology Miller Levine

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Specialized Tissue in Plants

• The three organs of a plant are the roots, stems
  and leaves
• The three tissue systems of a plant are dermal
  tissue, vascular tissue, and ground tissue
• A special type of tissue called meristematic
  tissue is the only plant tissue that can produce
  new cells by mitosis
• Found in the tips of shoots and roots

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Dermal Tissue

• The outer covering of a plant
• Consists of a single layer of epidermal cells
• Cuticle a waxy layer that often covers the
  epidermis
• Provides protection against water loss injury
• May include specialized structures such as root
  hairs and guard cells

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Vascular Tissue

• Transports water and nutrients throughout the
  plant
• Xylem transports water composed of dead cells
• Phloem transports nutrients composed of living
  cells called sieve tube elements

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Ground Tissue

• Lies between the dermal and vascular tissues
• Parenchyma has thin cell walls and large
  central vacuoles
• Collenchyma has strong, flexible cell walls and
  is found in larger plants
• Sclerenchyma has extremely thick, rigid cells
  walls

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Roots

• Types of roots
• Taproot - A thick primary root that grows long
  and is found mainly in dicots
• Fibrous roots branch extensively and are found
  mainly in monocots

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Root Structure Growth

• Root hairs tiny projections from the epidermis
  that increases the surface area for absorption of
  water
• Cortex layer of ground tissue
• Endodermis layer of tissue that encloses the
  vascular tissue
• Root cap protects the root as it forces its way
  through the soil

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Root Structure Function
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Root Function

• Anchor a plant in the ground
• Absorb water and dissolved nutrients from the soil

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Stem Function Types

• Three important functions
• Produce leaves, branches and flowers
• Hold leaves up in the sunlight
• Transport substances between roots and leaves
• Two types
• Monocot has vascular bundles that contain the
  xylem phloem scattered randomly
• Dicot have vascular bundles organized in a
  ringlike pattern

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Monocots and Dicots
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Stem Structures

• Nodes where leaves are attached
• Internodes regions between the nodes
• Buds contain undeveloped tissue that can
  produce new stems and leaves

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Leaf Structure

• Blade thin, flattened section
• Petiole thin stalk that attaches the leaf to
  the stem
• Veins contain the xylem and phloem

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Leaf Structure

• Palisade mesophyll tightly packed cells that
  absorb light
• Spongy mesophyll loosely packed cells with air
  spaces
• Stomata pore-like openings for taking in CO2
  and releasing O2
• Guard cells cells that open and close the
  stomata

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Leaf Structure
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Leaf Functions

• Photosynthesis takes place in the mesophyll
  cells of the leaf
• Transpiration the loss of water from a plant
  through its leaves (helps to pull water up from
  the roots)
• Gas exchange taking in carbon dioxide and
  releasing oxygen