The Movement of Water through the Roots

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  • Created by: Jessica
  • Created on: 13-01-13 10:05
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  • The Movement of Water through roots
    • Plants need to conserve water, and so are covered by a waterproof layer.
      • Root hairs are therefore the only part of the plant that can absorb water.
        • The dicotyledonous root contains:
          • Root hair
            • Provide large surface area
            • Thin surface layer across which materials move easily
            • Have a low water potential due to the minerals, sugars and amino acids dissolved inside them.
              • The soil has a high water potential.
                • Water moves by osmosis from the soil solution into the root hair cells DOWN the water potential gradient.
          • Phloem (outside tubes)
          • Xylem (inner "plus")
          • Endodermis surrounding ploem and xylem
            • Casparian strip made up of a waxy, waterproof substance
            • Protoplast
    • The Apoplastic Pathway
      • The water molecules are drawn into the endodermal cells, and become cohesive.
        • The created tension pulls the water along the cell walls of the cortex.
      • Cellulose walls have a mesh-like structure with water filled spaces, so there is no resistance to the pull of water.
    • The Symplastic Pathway
      • Occurs in the cytoplasm of the cells due to osmosis.
      • Water moves through the PLASMODESMATA in the cell walls.
        • Water entering by osmosis increases the water potential of the root hair cell.
        • The water potential gradient is set up across all the cells in the cortex, so water is carried alogn the cytoplasm from the root hair cell to the endodermis.


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