Water movement across the root and up the stem



  • Root hair cell absorbs water and mineral ions from soil.
  • Water moves by osmosis across root cortex down WPG to the endodermis of the vascular bundle.
  • Water may move by apoplast pathway as far as the endodermis.
  • Casparian s trip blocks apoplast pathway between cortex and medulla, so water and dissolved ions have to pass through plasma membranes (symplast pathway).
  • Transporter proteins in plasma membranes actively pump mineral ions into medulla and xylem so their water potential decreases. Water moves into the medulla and xylem by osmosis.
  • Water cannot pass back into the cortex…


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