Water movement across the root and up the stem

ACROSS THE ROOT -

• 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…