Exchange of material in plants

UPTAKE OF WATER AND MINERAL IONS IN PLANTS
1. Plant roots are adapted to take water and mineral ions from the soil as efficiently as possible. The roots themselves are thin, divided tubes with a large surface area. The cells on the outside of the roots near the growing tips have special adaptations that increase the surface area. These rootsa hair cells have tiny projections fromt he cells which push out between the soil particles.
2. Water moves into the roots cells across the partially permable membrane. It then has a short distance to move across the root to the xylem.
3. Plant roots are adapted to take in mineral ions using active transport. It has plenty of mitrochondria to supply the energy it needs. They have the advantages of a large surface area and short pathways for movement of water
GAS EXCHANGE IN PLANTS
1. Plants need carbon dioxide and water from photosynthesis to take place. They get the carbon dioxide they need from their leaves.
  1. The flattened shape of the leaves increases the surface area for diffusion.
    1. Most plants have thin leaves which means the distance the carbon dioxide has to diffuse from the air to the cell is kept short
    2. Leaves have many air spaces in their structure which allows CO2 to come into contact with lots of cells and give a large surface area for diffusion
2. Problem: Leaf cells loose water by evaporation . If CO2 could diffuse quickly in and out of the leaves water vapour would be lost quickly .
  1. When it is dark , they don't need CO2 because they are not photosynthesising - but on bright sunny days a lot of CO2 needs to come into the leaves by diffusion
3. Leaves are adapted to allow the CO2 in only when needed. They are covered in a waxy cuticle and it is waterproof and gasproof layer.
  2. All over the leaf surface are small openings - stomata. These can be opened when plant need air for leaves.
    1. CO2 from the atmosphere diffuses into the air spaces and then into the cells along a concentration gradient .
      1. At the same time oxygen produced by photosynthesis is removed from leaf by by diffusion into surrounding air.
        The opening and closing of the stomata is controlled by guard cells. Water is lost from the leaves by diffusion when the stomata are opened.
Plants rely heavily on diffusion to get the carbon dioxide they need for photosynthesis
1. They use osmosis to take water from the soil and active transport to obtain mineral ions from the soil
  1. Plants have adaptations that make these exchanges as efficient as possible.

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Exchange of material in plants

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	Created by eldea010.306 over 10 years ago