transport in plants

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  • Created on: 18-03-14 20:10
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  • transport in plants
    • requirements of plants
      • C02- photosynthesising plant cells need a supply of C02 during daylight. They obtain it from the air and aquatic plants from the water
      • Oxygen- All living plant cels need oxygen for respiration. Cells that are actively photosynthesising produce more 02 than necessary.
      • Inorganic ions and water- all plant cells require a range of inorganic ions and also water. These are taken up by the soil and transported all over the plant
    • water transport in plants (process)
      • 1- water  is uptake from near the root tips
      • 2- Water enters the xylem
      • 3- water moves up the xylem
      • 4- water moves from the xylem to leaf cells
      • 5- evaporation of water into leaf air spaces
      • 6- transpiration of water vapour though open stomata into the air
      • As a side note to this as you go up the stem into the leafs the water potential decrease
    • From soil to root hair
      • Roots have very thin single cell extensions called root hairs
        • they are a specialised exchange surface for the uptake of mineral ions and water
      • each root hair is only about 200-250 micrometers across, yet still large enough to be seen with the naked eye
        • however although they are small they are thousands on one tiny branch which creates a huge surface area
      • soil is made of particles of minerals and humus, between these are air spaces, unless the soil is dry, there is a thin layer of water  covering each soil particle
        • the root hairs make contact with this water and transport it using osmosis
          • The water in the soil moves into the root hairs because there is a lower concentration of solutes in the soil than the plant. Therefore the water potential outside is higher so the water moves along its gradient into the cell
    • factors affecting transpiration
      • Humidity- this measure the amount of water vapour in the air. In conditions of low humidity, when the air is dry  there is a steep water potential gradient, transpiration rates are higher in low humidity
      • Temperature- increase in temperature means a rise in kinetic energy meaning an increase in evaporation, an increase in temperature means an increase in transpiration


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