Water transport

• Plants need water for:

  • Photosynthesis
  • Transport minerals
  • Maintain structural rigidity (turgidity of cells)
  • Regulate temperature
• Water is absorbed from the soil by osmosis and moves up the stem of the plant from the roots to the leaves
• Water is absorbed by the roots through extensions called root hairs
• Mineral ions absorbed by active transport from the soil (including nitrates and phosphates) are dissolved in the water
• Plants need nitrates to produce:

  • DNA
  • Amino acids (proteins)
  • Chlorophyll
• Phosphates are also required in plants to make DNA and ATP
• Without these essential minerals (nitrates and phosphates), plants would not be able to grow, produce fruits or seeds
• Transpiration is the loss of water vapour from the stomata

  • This is evaporation and it mainly occurs on the leaves, as this is where stomata are located
• Rate of transpiration is affected by:

  • Temperature
  • Light intensity
  • Humidity
  • Air movement (wind)
• Cohesion between water molecules creates a continuous water column in the xylem
• Adhesion is the sticking of water molecules to the xylem wall