Absorption &structure&functions of xylem

• Absorption of water by root hair


  1. More water is drawn into root hair cell

  2. Root hair cell becomes more concentrated than adjacent cells

  3. Water moves from root hair cell into cells of cortex

  4. Cells of cortex become more dilute than cells in endodermis

  5. Water molecules move into endodermis by osmosis

  6. Content of endodermis becomes more dilute compared to adjacent cells of pericycle

  7. Water moves into pericycle by osmosis

  8. Content of pericycle becomes more dilute than adjacent xylem vessels

  9. Water then moves to xylem which conducts water to the leaves
• The concentration of cell sap in root hair is greater than in the soil
• Mineral ions enter root hair cell against concentration gradient by active transport
• Mineral ions where concentration is higher in the soil than in root hair cell are taken by diffusion
• After absorbing more through the root cells, mineral ions move into xylem vessels of vascular bundle in the root where they are conducted then into stem
• Xylem tissue


  • Consists of two main components: tracheids and xylem vessels
• Tracheids


  Long, shallow tubes made up of dead, lignified cells where the protoplasm and cross walls have disintegrated, resulting in a continuous hollow tube
• Xylem vessels


  • Provide passage for the vertical movement of substances through their lumen
  • Xylem walls are strengthened by deposits of lignin that prevent collapsing
• Types of xylem wall thickening

  • Annular
  • Reticulate
  • Pitted