(AQA GCSE B3.1.2) Exchange Systems and Water Loss in Plants

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  • Created by: Em
  • Created on: 17-04-13 18:43
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  • Exchange Systems in Plants
    • Carbon dioxide (CO2) diffuses in, required for photosynthesis
      • Oxygen (O2) diffuses out of the leaf as a byproduct of photosynthesis
      • At night, more respiration occurs than photosynthesis and therefore CO2 diffuses out
    • Water and mineral ions diffuse through the roots. Roots increase surface area with root hair cells.
    • Leaves are flat and thin which shortens the diffusion distance. Inside the leaf, mesophyll cells are loosely packed which means there is a lot of surface area for substances to diffuse through and for oxygen to diffuse out.
  • Water Loss in Plants
    • Water travels from roots to leaves where a large proportion is used for photosynthesis.
    • Transpiration, water evaporates from the leaves. Varies depending on environment e.g. dry, windy, and hot climates, more evaporation (heat energy, water particles moved away, and concentration gradient).
    • Guard cells around stomata (which let CO2 in) open and close depending on conditions, for example if it is hot they will shut to a certain degree to reduce water loss.


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