Plant transport

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Plant transport

  1. 1. TWO transport systems in plants: XYLEM  transports water and mineral salts  no need for energy as ATP  made of dead cells PHLOEM  transports food e.g. sucrose, amino acids using ATP  made of living cells
  2. 2. Vascular tissueis composed of:  Xylem  Phloem
  3. 3. Note how the xylem & phloem branch to enter the leaves
  4. 4. Where are the xylem and pholem?In the Leaf mid-rib vein xylem phloem
  5. 5. Direction of flow
  6. 6. What causesthe upwardflow withinthe xylem? Mostly,evaporationof water by the sun.
  7. 7. Translocation is the long-distance transport of food materials within a plant To growing regions to beGlucose produced by used as energy for growth.photosynthesis in leaf isconverted to sugars(mainly sucrose) andtranslocated to differentparts of the plant. To storage organ (fruit) to be stored mainly as sugars. To storage organ (tubers in roots) To be stored mainly as starch.
  8. 8. Section through a stem.Section through a root.
  9. 9. Cambium: a region of growth
  10. 10. Let’s discover the reason for thedifferent positioning of the xylem & phloem in the stem & root STEM: at the side ROOT: at the centre
  11. 11. Shoot sways in the wind. What prevents it from snapping?
  12. 12. Stem must be flexible to bend without snapping Sways in the wind Anchors the shoot.
  13. 13. Give a reason for the arrangement of the vascular bundles in the stem. phloem xylemThe xylem and phloem are arranged in bundlesnear the edge of the stem to resist compression and bending forces.
  14. 14. Stem resists:Bending forces
  15. 15. Give a reason for the arrangement of the vascular tissue in the root. phloem xylemThe xylem and phloem in the centre of the root to withstand stretching forces.
  16. 16. To show the site of sugar movement in a plant A complete ring of bark (containing phloem tissue) was removed from a woody stem.
  17. 17. Result: the removal of the phloem prevents transport in the plant
  18. 18. Conclusion: phloem tissue is the site of sugar transport
  19. 19. To show the site of water movement in a plant
  20. 20. To show the site of water movement in a plant plant is left in eosin (red dye) for about one hour cross sections of the stem and root are cut out and examined
  21. 21. Celery stalk in eosin. After 24 h Note red lines.
  22. 22. Celery stem under microscope Xylem stains red
  23. 23. ….. if left formany days
  24. 24. Celery leafveins stain red
  25. 25. Predict what would happen.1 23 4
  26. 26. Predict what would happen.
  27. 27. Which parts become stained red with eosin?
  28. 28. STEM ROOT
  29. 29. What is thefunction of root hairs?Absorb water and mineral ions.
  30. 30. How are root hairs adapted for absorption?1. are long and provide a large surface area2. have a thin cell wall
  31. 31. Question: [SEP, 2005]Plants need mineral ions which they obtain fromsoil. Explain how the uptake of mineral ions byplants, may be inhibited in waterlogged soils. (3)Ions are taken up by active transport.Active transport needs energy fromrespiration.There is not enough oxygen for roots torespire in waterlogged soils.
  32. 32. Uptake and transport of water
  33. 33. A root hair cell has an extension
  34. 34. Learn to draw a root hair cell nucleus cytoplasmcell membrane cell wall
  35. 35. How does water from the soil end up in the xylem? The Uptake of Water Up xylem vessels to plant into xylem acrossWater from soil absorbed into across cortex vessels phloem root hair cell cells
  36. 36. Water moves by osmosis across the root causing root pressure H2O H2O
  37. 37. Transpiration:is the loss of water vapour from thesurface of a plant
  38. 38. Water vapour is lost via open stomata
  39. 39. Transpiration stream:the flow of water from root to leaves
  40. 40. Transport Of Water And Mineral SaltsTransport in the Xylem There are three forces that move the water upwards in the xylem: a) Root pressure - a force that pushes water up the xylem (produced by the continuous movement of water through the root cells. b) Capillary action - a force that pushes water up the narrow xylem vessels. c) Transpirational pull - a force that pulls water up the xylem (produced by evaporation of water from the leaves).
  41. 41. QUESTION: SEP, 2011Describe the path taken by awater molecule from the roothair to the stomata in a leaf. (3)
  42. 42. Root hair absorbs water by osmosis.Water moves across the root cortex by osmosis.Water enters xylem and moves up towardsleaves, mostly due to evaporation.Water evaporates intoair spaces betweenspongy mesophyll cellsand diffuses out viastomata.
  43. 43. Let’s studytranspiration in detail.
  44. 44. Transpiration:is the loss of water vapour from the surface of a plant
  45. 45. How can you show that water is actually lost by transpiration & not another chemical?Leave for 1 hour. Test condensation by a piece of blue cobalt chloride paper.
  46. 46. Blue cobalt chloride paper becomes pink
  47. 47. Apparatus to measure the rate of transpiration: Potometer Weight Water potometer potometer balance
  48. 48. Weight potometer A potted plant is well watered. A plastic bag is wrapped around the pot to prevent water loss from the soil. The apparatus is weighed at intervals and changes in weight indicate water loss.
  49. 49. Suggest a control for this experiment. CONTROL
  50. 50. To study the effect of wind speed on the rate of transpiration Which graph is for highest fan speed? C
  51. 51. A water potometer
  52. 52. A water potometer measures the rate of water ABSORBED by the plant it is assumed that:amount of water absorbed = water lost
  53. 53. A water potometer Capillary tubing. Ordinary glass tubing. Why is capillary tubing used rather than ordinary glass tubing?
  54. 54. A water potometer
  55. 55. Precautions
  56. 56. Four factors affecting transpiration 1. Light 2. Temperature 3. Humidity 4. Wind currents
  57. 57. Four factors affecting transpiration 1. Light  stomata open in the light and so more water is lost
  58. 58. Four factors affecting transpiration2. Temperature as temperature increases, evaporation increases Water molecules move faster.
  59. 59. 3. Humidity in dry air, the plant loses more water vapour than in humid air
  60. 60. High humidity in air : less transpiration. WHY? A lot of water vapour in air. Not A lot of water much differencevapour inside leaf in concentration
  61. 61. Four factors affecting transpiration4. Wind currents moving air removes water vapour from the leaf surfaces
  62. 62. QUESTION: SEP, 2011Stomata allow transpiration to occur.Explain why if a plant is enclosed in atransparent bag, the rate of transpirationdecreases. (4)Air around shoot becomeshumid.Difference in concentrationof water vapour inside theleaf and in the air aroundleaf decreases.
  63. 63. Functions of transpiration1. The plant cools as water evaporates.2. Water is transported up the plant as water is lost from the shoot – keeps cells turgid.3. Dissolved salts move up too.
  64. 64. What is the picture showing? The plant lost No loss in weightweight as water as the waterevaporates in to which the air. evaporated, retur ned to flask. 2 1
  65. 65. QUESTION: MAY, 2012Comment on the biological significance of thefollowing statement:Transpiration may have some useful effects inplants. (4)
  66. 66. Plant adaptationsto reduce water loss
  67. 67. 1. Reduced leaf area – e.g. in cacti and pine
  68. 68. 2. Hairs on leaves to trap moisture
  69. 69. 3. Thick waxy cuticle – reduces transpiration by:i) acting as a barrier to evaporationii) the shiny surface reflects heat and so lowers temperature Holly
  70. 70. 4. Stomata on lower surface of leaves – as more water would be lost if stomata were on the upper epidermis as the sun acts directly on this surface.
  71. 71. 5. Sunken stomata trap still, moist air abovethe stomata, so reducing transpiration.
  72. 72. Notice the thick cuticle
  73. 73. Adaptations of plants which live in dry habitats
  74. 74. 1. Succulent leaves or stems (most cacti) to store water.
  75. 75. 2. Shallow, but extensive root systems
  76. 76. What is the advantage of having both shallow and deep roots?
  77. 77. QUESTION: MAY, 2006Olive trees (Olea europaea) are native to theMediterranean region and other hot, arid regions.Give TWO adaptations which plants living in thisregion show to reduce the rate of transpiration. (2)1. Thick waxy cuticle.2. Dense cover of short hairs on underside of leaves.3. Relatively small leaves.4. Sunken stomata.
  78. 78. THE END

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