Transpiration

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  • Created by: Steff06
  • Created on: 01-05-16 13:11
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  • Transpiration:
    • The loss of water vapour by evaporation from the leaves of the plant.
    • The water enters the leaves in the xylem and passes into the mesophyll cells by osmosis. Water evaporates from the surface of the mesophyll cells to form water vapour.
    • Spongy mesophyll cells have large air spaces between them that help water vapour to diffuse through the leaf tissue.
    • Water vapour collects in these air spaces and the water vapour potential rises. When the water vapour potential in the leaf is higher than outside, water will diffuse out of the leaf through stomata.
    • Osmosis from xylem to mesophyll cells -->
      • Evaporation from surface of mesophyll cells to inter cellular spaces -->
        • Diffusion of water vapour from inter cellular spaces out through stomata.
    • Movement of water up stem is useful as:
      • Water required in leaves for photosynthesis.
      • Water required to enable cells to grow and elongate.
      • Water keeps cells turgid and can carry minerals up the plant.
      • Evaporation of water can keep the plant cool.
    • Measure transpiration with a podometer. Measures rate of water uptake by a cut shoot.

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