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Plant transport

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M
Marthese Azzopardi

Plant transport systems include xylem and phloem. Xylem transports water and minerals upwards from roots to shoots passively, using no energy. Phloem transports food such as sucrose horizontally throughout the plant using energy from ATP. Xylem vessels are located towards the edges of stems to resist bending forces, while located centrally in roots to withstand stretching. Transpiration is the evaporation of water from plant leaves, powered by the transpiration stream which replaces lost water. Transpiration cools plants and transports minerals upwards from roots.

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Plant transport
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
Vascular tissue is composed of:  Xylem  Phloem
Note how the xylem & phloem branch to enter the leaves
Where are the xylem and pholem? In the Leaf mid-rib vein xylem phloem
Direction of flow
What causes the upward flow within the xylem? Mostly, evaporation of water by the sun.
Translocation  is the long-distance transport of food materials within a plant To growing regions to be Glucose produced by used as energy for growth. photosynthesis in leaf is converted to sugars (mainly sucrose) and translocated to different parts 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.
Section through a stem. Section through a root.
Cambium: a region of growth
Let’s discover the reason for the different positioning of the xylem & phloem in the stem & root STEM: at the side ROOT: at the centre
Shoot sways in the wind. What prevents it from snapping?
Stem must be flexible to bend without snapping Sways in the wind Anchors the shoot.
Give a reason for the arrangement of the vascular bundles in the stem. phloem xylem The xylem and phloem are arranged in bundles near the edge of the stem to resist compression and bending forces.
Stem resists: Bending forces
Give a reason for the arrangement of the vascular tissue in the root. phloem xylem The xylem and phloem in the centre of the root to withstand stretching forces.
To show the site of sugar movement in a plant A complete ring of bark (containing phloem tissue) was removed from a woody stem.
Result:  the removal of the phloem prevents transport in the plant
Conclusion:  phloem tissue is the site of sugar transport
To show the site of water movement in a plant
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
Celery stalk in eosin. After 24 h Note red lines.
Celery stem under microscope Xylem stains red
….. if left for many days
Celery leaf veins stain red
Predict what would happen. 1 2 3 4
Predict what would happen.
Which parts become stained red with eosin?
STEM ROOT
What is the function of root hairs? Absorb water and mineral ions.
How are root hairs adapted for absorption? 1. are long and provide a large surface area 2. have a thin cell wall
Question: [SEP, 2005] Plants need mineral ions which they obtain from soil. Explain how the uptake of mineral ions by plants, may be inhibited in waterlogged soils. (3) Ions are taken up by active transport. Active transport needs energy from respiration. There is not enough oxygen for roots to respire in waterlogged soils.
Uptake and transport of water
A root hair cell has an extension
Learn to draw a root hair cell nucleus cytoplasm cell membrane cell wall
How does water from the soil end up in the xylem? The Uptake of Water Up xylem vessels to plant into xylem across Water from soil absorbed into across cortex vessels phloem root hair cell cells
Water moves by osmosis across the root causing root pressure H2O H2O
Transpiration: is the loss of water vapour from the surface of a plant
Water vapour is lost via open stomata
Transpiration stream: the flow of water from root to leaves
Transport Of Water And Mineral Salts Transport 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).
Plant transport
QUESTION: SEP, 2011 Describe the path taken by a water molecule from the root hair to the stomata in a leaf. (3)
Root hair absorbs water by osmosis. Water moves across the root cortex by osmosis. Water enters xylem and moves up towards leaves, mostly due to evaporation. Water evaporates into air spaces between spongy mesophyll cells and diffuses out via stomata.
Let’s study transpiration in detail.
Transpiration: is the loss of water vapour from the surface of a plant
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.
Blue cobalt chloride paper becomes pink
Apparatus to measure the rate of transpiration: Potometer Weight Water potometer potometer balance
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.
Suggest a control for this experiment. CONTROL
To study the effect of wind speed on the rate of transpiration Which graph is for highest fan speed? C
A water potometer
A water potometer measures the rate of water ABSORBED by the plant  it is assumed that: amount of water absorbed = water lost
A water potometer Capillary tubing. Ordinary glass tubing. Why is capillary tubing used rather than ordinary glass tubing?
A water potometer
Precautions
Plant transport
Plant transport
Plant transport
Plant transport
Four factors affecting transpiration 1. Light 2. Temperature 3. Humidity 4. Wind currents
Four factors affecting transpiration 1. Light  stomata open in the light and so more water is lost
Four factors affecting transpiration 2. Temperature  as temperature increases, evaporation increases Water molecules move faster.
3. Humidity  in dry air, the plant loses more water vapour than in humid air
High humidity in air : less transpiration. WHY? A lot of water vapour in air. Not A lot of water much difference vapour inside leaf in concentration
Four factors affecting transpiration 4. Wind currents  moving air removes water vapour from the leaf surfaces
QUESTION: SEP, 2011 Stomata allow transpiration to occur. Explain why if a plant is enclosed in a transparent bag, the rate of transpiration decreases. (4) Air around shoot becomes humid. Difference in concentration of water vapour inside the leaf and in the air around leaf decreases.
Functions of transpiration 1. 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.
What is the picture showing? The plant lost No loss in weight weight as water as the water evaporates in to which the air. evaporated, retur ned to flask. 2 1
QUESTION: MAY, 2012 Comment on the biological significance of the following statement: Transpiration may have some useful effects in plants. (4)
Plant adaptations to reduce water loss
1. Reduced leaf area – e.g. in cacti and pine
2. Hairs on leaves to trap moisture
3. Thick waxy cuticle – reduces transpiration by: i) acting as a barrier to evaporation ii) the shiny surface reflects heat and so lowers temperature Holly
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.
5. Sunken stomata trap still, moist air above the stomata, so reducing transpiration.
Notice the thick cuticle
Adaptations of plants which live in dry habitats
1. Succulent leaves or stems (most cacti) to store water.
2. Shallow, but extensive root systems
What is the advantage of having both shallow and deep roots?
QUESTION: MAY, 2006 Olive trees (Olea europaea) are native to the Mediterranean region and other hot, arid regions. Give TWO adaptations which plants living in this region 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.
THE END

More Related Content

Plant transport

  • 2. 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
  • 3. Vascular tissue is composed of:  Xylem  Phloem
  • 4. Note how the xylem & phloem branch to enter the leaves
  • 5. Where are the xylem and pholem? In the Leaf mid-rib vein xylem phloem
  • 7. What causes the upward flow within the xylem? Mostly, evaporation of water by the sun.
  • 8. Translocation  is the long-distance transport of food materials within a plant To growing regions to be Glucose produced by used as energy for growth. photosynthesis in leaf is converted to sugars (mainly sucrose) and translocated to different parts 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.
  • 9. Section through a stem. Section through a root.
  • 10. Cambium: a region of growth
  • 11. Let’s discover the reason for the different positioning of the xylem & phloem in the stem & root STEM: at the side ROOT: at the centre
  • 12. Shoot sways in the wind. What prevents it from snapping?
  • 13. Stem must be flexible to bend without snapping Sways in the wind Anchors the shoot.
  • 14. Give a reason for the arrangement of the vascular bundles in the stem. phloem xylem The xylem and phloem are arranged in bundles near the edge of the stem to resist compression and bending forces.
  • 16. Give a reason for the arrangement of the vascular tissue in the root. phloem xylem The xylem and phloem in the centre of the root to withstand stretching forces.
  • 17. To show the site of sugar movement in a plant A complete ring of bark (containing phloem tissue) was removed from a woody stem.
  • 18. Result:  the removal of the phloem prevents transport in the plant
  • 19. Conclusion:  phloem tissue is the site of sugar transport
  • 20. To show the site of water movement in a plant
  • 21. 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
  • 22. Celery stalk in eosin. After 24 h Note red lines.
  • 23. Celery stem under microscope Xylem stains red
  • 24. ….. if left for many days
  • 26. Predict what would happen. 1 2 3 4
  • 28. Which parts become stained red with eosin?
  • 29. STEM ROOT
  • 30. What is the function of root hairs? Absorb water and mineral ions.
  • 31. How are root hairs adapted for absorption? 1. are long and provide a large surface area 2. have a thin cell wall
  • 32. Question: [SEP, 2005] Plants need mineral ions which they obtain from soil. Explain how the uptake of mineral ions by plants, may be inhibited in waterlogged soils. (3) Ions are taken up by active transport. Active transport needs energy from respiration. There is not enough oxygen for roots to respire in waterlogged soils.
  • 34. A root hair cell has an extension
  • 35. Learn to draw a root hair cell nucleus cytoplasm cell membrane cell wall
  • 36. How does water from the soil end up in the xylem? The Uptake of Water Up xylem vessels to plant into xylem across Water from soil absorbed into across cortex vessels phloem root hair cell cells
  • 37. Water moves by osmosis across the root causing root pressure H2O H2O
  • 38. Transpiration: is the loss of water vapour from the surface of a plant
  • 39. Water vapour is lost via open stomata
  • 40. Transpiration stream: the flow of water from root to leaves
  • 41. Transport Of Water And Mineral Salts Transport 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).
  • 43. QUESTION: SEP, 2011 Describe the path taken by a water molecule from the root hair to the stomata in a leaf. (3)
  • 44. Root hair absorbs water by osmosis. Water moves across the root cortex by osmosis. Water enters xylem and moves up towards leaves, mostly due to evaporation. Water evaporates into air spaces between spongy mesophyll cells and diffuses out via stomata.
  • 46. Transpiration: is the loss of water vapour from the surface of a plant
  • 47. 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.
  • 48. Blue cobalt chloride paper becomes pink
  • 49. Apparatus to measure the rate of transpiration: Potometer Weight Water potometer potometer balance
  • 50. 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.
  • 51. Suggest a control for this experiment. CONTROL
  • 52. To study the effect of wind speed on the rate of transpiration Which graph is for highest fan speed? C
  • 54. A water potometer measures the rate of water ABSORBED by the plant  it is assumed that: amount of water absorbed = water lost
  • 55. A water potometer Capillary tubing. Ordinary glass tubing. Why is capillary tubing used rather than ordinary glass tubing?
  • 62. Four factors affecting transpiration 1. Light 2. Temperature 3. Humidity 4. Wind currents
  • 63. Four factors affecting transpiration 1. Light  stomata open in the light and so more water is lost
  • 64. Four factors affecting transpiration 2. Temperature  as temperature increases, evaporation increases Water molecules move faster.
  • 65. 3. Humidity  in dry air, the plant loses more water vapour than in humid air
  • 66. High humidity in air : less transpiration. WHY? A lot of water vapour in air. Not A lot of water much difference vapour inside leaf in concentration
  • 67. Four factors affecting transpiration 4. Wind currents  moving air removes water vapour from the leaf surfaces
  • 68. QUESTION: SEP, 2011 Stomata allow transpiration to occur. Explain why if a plant is enclosed in a transparent bag, the rate of transpiration decreases. (4) Air around shoot becomes humid. Difference in concentration of water vapour inside the leaf and in the air around leaf decreases.
  • 69. Functions of transpiration 1. 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.
  • 70. What is the picture showing? The plant lost No loss in weight weight as water as the water evaporates in to which the air. evaporated, retur ned to flask. 2 1
  • 71. QUESTION: MAY, 2012 Comment on the biological significance of the following statement: Transpiration may have some useful effects in plants. (4)
  • 73. 1. Reduced leaf area – e.g. in cacti and pine
  • 74. 2. Hairs on leaves to trap moisture
  • 75. 3. Thick waxy cuticle – reduces transpiration by: i) acting as a barrier to evaporation ii) the shiny surface reflects heat and so lowers temperature Holly
  • 76. 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.
  • 77. 5. Sunken stomata trap still, moist air above the stomata, so reducing transpiration.
  • 78. Notice the thick cuticle
  • 79. Adaptations of plants which live in dry habitats
  • 80. 1. Succulent leaves or stems (most cacti) to store water.
  • 81. 2. Shallow, but extensive root systems
  • 82. What is the advantage of having both shallow and deep roots?
  • 83. QUESTION: MAY, 2006 Olive trees (Olea europaea) are native to the Mediterranean region and other hot, arid regions. Give TWO adaptations which plants living in this region 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.