Plant

• properties of water:

  metabolite

  solvent

  high latent heat of vaporisation

  high specific heat capacity
• xylem and phloem: vascular bundle
• xylem: water and mineral ions
• phloem: organic substances e.g sucrose
• the water surrounding the root contains mineral ions which the root hair cell pumps

  in by active transport
• the water potential in the root hair cell is lower than the surrounding soil solution

  water then moves into root by osmosis
• xylem

  long cell with no end walls

  to allow unrestricted and continuous flow of water

  hollow tubes with no organelles

  to provide strength and resist tension and waterproof to prevent water loss

  walls contain thick lignin

  to allow continuous water column

  pits in walls

  to allow water to get around blocked vessels
• • Explain how xylem tissue is adapted for its function. (4)
  • long cells / tubes with no end walls;
  • continuous water columns;
  • no cytoplasm / no organelles / named organelle;
  • to impede / obstruct flow / allows easier water flow;
  • thickening / lignin;
  • support / withstand tension / waterproof / keeps water in cells;
  • pits in walls;
  • allow lateral movement / get round blocked vessels;
• Cohesion Tension Theory

  transpiration is water evaporation through stomata in leaf cells

  water loss reduces water potential in leaf cells

  water moves down the water potential gradient by osmosis, and is pulled up by the xylem, creating tension

  cohesion is when hydrogen bonds cause water molecules to “stick” together

  cohesion pulls water up the xylem into a continuous water column

  adhesion between water molecules and the xylem walls maintains the column being pulled up by the xylem
• rate of transpiration is lower with still air because there is less evaporation meaning the air around the plant is wetter , therefore it doesn't evaporate as much
• rate of transpiration is higher in moving air because there is more evaporation, the air around the plant is more dry because the plant is moving therefore more evaporation
• the rate of transpiration is higher at a higher temperature because there is more evaporation, there is more kinetic energy so more movement
• transpiration in lower temps is lower because there is less evaporation, less kinetic energy so less movement