transport in plants

  • Created by: Lois
  • Created on: 08-01-13 11:47
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  • Transport in plants
    • why plants need a transport system
      • every cell of a multicellu;ar plant needs a regular supply of water and nutrients
        • there are many cells in the plant that would not recieve enough of what they need simply by diffusion
          • roots cannot absorb sugars from the soil, the leaves can produce sugars but not obtain enough water from the air
      • the transport system in plants moves water in vascualar tissues
    • xylem and phloem in root
      • central core of xylem in X shape, phloem found in between arms of X shape - this arrangement provides strength to withstand pulling forces which roots are exposed
        • around vascular bundle is sheath of cells called endodermis - key role in getting water into xylem vessels
          • just inside endodermis layer of meristem cells called pericycle
    • xylem and phloem in stem
      • vascular bundles found near outer edge, in non-woody plants bundles are seperate and discrete. in woody plant bundles seperate in young stems but become more continuous in older stems
        • so complete ring of vascular tissue under bark of tree, arrangement provides strength and flexability to withstand bending forces that stem and branches are exposed
          • xylem inside vascular bundle, phloem towards outside but not completely, layer of cambium in between them - which is layer of meristem cells that divide to produce new x and p
    • xylem and phloem in leaf
      • vascular bundles form midrib and veins of leaf. 2 major groups of f;lowering plants: dicotyledons and monocotyledones - names based on no of leaves
        • these 2 goups have different patterns of veins. dicotyledon has branching netword that get smaller away from medrib.
          • within each vein xylem on top of phloem


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