Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Transport in flowering plants (self created)


Published on

Published in: Education
  • Be the first to comment

Transport in flowering plants (self created)

  1. 1. LESSON OBJECTIVES  To learn about the structure and functions of the xylem  To learn the mechanisms by which water is transported from the roots to the leaves (and other plant parts) in flowering plants  To know the definition of transpiration and the factors that affect the rate of transpiration
  2. 2. VASCULAR BUNDLES  Tissues that are responsible for the transport of materials in plants  Present in all parts of a plant including the roots, stem and leaves  Consist of xylem and phloem Xylem: Transport of water and dissolved mineral salts Phloem: Transport of food substances
  6. 6. XYLEM - STRUCTURE  Long, hollow, dead tubes forming continuous columns from roots to leaves  No cytoplasm in the lumen  Walls are strengthened by deposits of lignin  Pits present in xylem walls – enable transport of water between xylem vessels  Two xylem cell types: tracheids and vessel elements
  7. 7. Tracheid Vessel element
  8. 8. XYLEM - FUNCTIONS  Conducts water and dissolved mineral salts from roots to stems and leaves  Provides mechanical support within the plant
  9. 9. MECHANISMS OF WATER TRANSPORT IN PLANTS  Root pressure  Capillary action  Transpiration pull
  10. 10. ROOT PRESSURE  Force that helps to drive water upward into the xylem  Mainly generated by osmotic pressure in the cells of the roots, which is in turn caused by active transport of mineral ions into the root cells  Usually occurs when transpiration rate is low—at a low transpiration rate, the dissolved mineral ions accumulate in the root xylem and lower the water potential  Water then moves from the root hair cells into the xylem, through the cortical cells and the endodermis, by osmosis
  11. 11. CAPILLARY ACTION  A phenomenon where liquid spontaneously rises in a narrow space such as a thin tube  Since xylem vessels in plants are very narrow tubes, capillary action helps in moving water up the vessels  The forces of cohesion (attractive forces between water molecules) and adhesion (attractive forces between water molecules and the xylem walls) help to move water upward in the xylem  Plays an important part in upward movement of water in small plants
  12. 12. video
  13. 13. TRANSPIRATION  Definition: The loss of water vapour from the aerial parts of a plant, especially through the stomata of the leaves  Water continuously moves out of the mesophyll cells to form a thin film of moisture over their surfaces  From the wet cell walls, water evaporates into the intracellular spaces, and from there diffuses through the stomata to the surrounding air
  14. 14. TRANSPIRATION  As water evaporates from the mesophyll cells, the cell sap becomes more concentrated  Water from cells deeper inside the leaf thus move into the mesophyll cells by osmosis  These cells in turn remove water from the xylem vessels. As they do that, the whole column of water moves up the vessels from the roots to the leavesTRANSPIRATION PULL
  15. 15. TRANSPIRATION PULL  The suction force due to transpiration which pulls water up the xylem vessels  The main force that drives the transport of water and dissolved mineral salts up tall trees  The stream of water up the plant/tree is known as the transpiration stream
  16. 16. FACTORS AFFECTING THE RATE OF TRANSPIRATION  Light  Temperature  Wind  Humidity To be investigated in online activity
  17. 17. SUMMARY  The xylem is responsible for the transport of water and dissolved mineral salts in flowering plants  Root pressure, capillary action and transpiration pull are the three mechanisms of water transport in flowering plants  Transpiration pull is the main mechanism of water transport in tall trees
  18. 18. Before we end, let’s view this animation to remind us of what we have learnt today 