PHOSPHORUS CYCLE

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Cards (21)

  • Phosphorus is needed to make phosphate (PO43-)
  • Phosphate is needed to make DNA, ATP, phospholipids, etc
  • Plants take up phosphate via their root hairs by active transport
  • Phosphate is distributed through the food web
  • Saprobionts decompose DNA in dead material, releasing phosphate into the soil
  • Some phosphate is "leached" in solution into water bodies
  • Phosphate is used in aquatic food webs, and dead material sinks
  • Phosphate ultimately ends up in marine sediments, which turn into sedimentary rock at the bottom of the ocean
  • When uplifted to the surface, these rocks weather down to release phosphate
  • Mycorrhizae help to facilitate the uptake of water and inorganic ions by plants
    • A mycorrhiza is an association between a fungus and a plant root.
    • Plural: mycorrhizae.
    • The fungus acts as an extension to the root system, massively increasing the surface area for water and inorganic ion uptake for the plant.
    • This is especially important for phosphate, which is a major limiting factor in plant growth due to the slower nature of the phosphorus cycle.
    • In return, the plant shares some of its carbohydrate with the fungus for respiration: a “mutualistic” relationship where both species benefit.
    • In a natural ecosystem, nutrients can be recycled by saprobiotic decomposition of dead material.
    • On a farm, crops are harvested and livestock are sent for slaughter. This removes nutrients from the area.
    • Fertiliser can be applied to the field to replenish the lost nutrients.
    • Natural “organic” fertilisers include manure (animal faeces). Organic fertilisers have the nitrogen and phosphorus locked up in carbon-containing compounds (organic means carbon-containing).
  • Inorganic nitrate and phosphate fertiliser can also be manufactured artificially
    • Fertilisers increase plant growth by, for example, providing more nitrate for making protein and more phosphate for making DNA.