1. 1. Chapter 5: Transport in Plants
2. 2. Learning Objectives Identify positions of xylem and phloem in a dicot leaf, stem and root State the structures of xylem and phloem & relate to their functions
3. 3. Transport of substances How blood gets transported in our body? How water, food and minerals gets transported in Plants?
4. 4. Imagine What transports water from the roots to the furthest leaf? Did You Know That?! - Average of 60 meters in height - A rainforest tree uses ~1200 L of water/day What do plants rely on?
5. 5. The bottle tree plant, Baobab that live 500 years and store up 300 litre of water. BBC Video: http://www.youtube.com/watch?v=M9V9bVEDSVs http://www.youtube.com/watch?v=U2iFl6lvj4c
6. 6. Xylem Continuous long, hollow tube Dead, without protoplasm or cross-walls Walls are deposited with lignin, which is a hard and rigid substance Drawing UndertheMicroscope Describe what you see in the picture
7. 7. In flowering plants, the transport tissue consists of the xylem and the phloem. Xylem
8. 8. Transports & Xylem Function Water Minerals
9. 9. Lignin Walls are strengthened with lignin, which is a hard and rigid substance Xylem Mechanical support
10. 10. Phloem Describe what you see in the picture
11. 11. It is a living structure Made up of sieve tubes and companion cells Transport food manufactured in the leaves to other parts of the plant by translocation Phloem (Sucrose)
12. 12. Food is either transported or diffused through the cytoplasm of the sieve tube cells. Each sieve tube has a companion cell beside it to: keep it alive provide energy for active transport Phloem
13. 13. transportinplantstransportinplantstransportinplantstransportinplantstransportinplantstransportinplantstransportinplantstransportinplantstransportinplantstransportin Function: Adaptations: Transport manufactured food from the leaves to other parts of the plants. Companion cells have lots of mitochondria which provides the energy needed by the sieve tube cells for respiration. Holes in the sieve plates allow transport of manufactured food substances through the sieve tubes. Phloem
14. 14. Translocation (Phloem) How do we know that the phloem transport manufactured food??
15. 15. translocationSTUDIES (pure) Isotopes The plant is grown in the environment containing radioactive carbon dioxide 14CO2. When photosynthesis takes place, the sugar formed will contain radioactive carbon. The cut stem section when exposed onto an X-ray photographic film will turn cloudy. This shows that the radioactive substances are present in the phloem.
16. 16. Aphids Aphids are parasites that feed on plants. Mouthparts (proboscis) of aphids penetrate the leaf or stem during feeding. When the body of the aphid is cut off, leaving behind the proboscis in the plant tissues, the liquid will exude from the cut end of the proboscis. The liquid is found to contain sucrose and amino acids. http://www.youtube.com/watch?v=J7eRGH Vx3p0 translocationSTUDIES (pure)
17. 17. Ringing experiment1. Removing a ring of bark from a woody branch will result in the removal of the phloem tissue in that region. Swelling will be observed in the region above the ring. 2. The swelling above the ring where the phloem is removed will be caused by an accumulation of sugars in the region above the ring. A B region with bark removed translocationSTUDIES (pure)
18. 18. Translocation studies can be carried out using aphids. The diagram below shows a section of a plant stem where the proboscis of a feeding aphid may be found. In which tissue would the proboscis most likely be inserted into? microQUESTION9.4 A D C B
19. 19. Vascular Bundle Xylem vessels + Phloem vessels Vascular Bundle Found in the Root Stem Leaf
20. 20. Magnification: 100X
21. 21. Vascular Bundle of a Sunflower root
22. 22. Vascular bundle Root Xylem Phloem
23. 23. Magnification: 100X
24. 24. Phloem Xylem Vascular Bundle of a Sunflower Stem
25. 25. Vascular bundle Stem
26. 26. vascularBUNDLE(pure) XYLEM PHLOEM CAMBIUM The xylem and the phloem group together to form a vascular bundle (literally a bundle of vessels).
27. 27. Magnification: 400X
28. 28. Vascular bundle Leaf Xylem Phloem
29. 29. Transport in Plants Xylem Phloem Water Mineral Salt Mechanical Support Lignified Walls Manufactured food (Sucrose) Sieve tube Companion cell
30. 30. Uptake of Water 30
31. 31. Uptake of Water by the Roots 31
32. 32. Movement of Water molecules Osmosis is the net movement of water molecules from a solution of higher water potential to a solution of lower water potential through a selectively permeable membrane 32
33. 33. waterTRANSPORT Root Hair Cell
34. 34. Adaptation Function Root hair cell has long & narrow protrusions Increase surface area to volume ratio for faster rate of absorption of water and mineral salts Cell surface membrane prevents leaking of cell sap Maintain low water potential of cell for osmosis Living cell Provides energy from cellular respiration for absorption of mineral salts by active transport Root Hair Cell Structure & Function
35. 35. Taking the train 35
36. 36. Please Consider the following 36
37. 37. Uptake of water by Root Hair Cells Xylem 37
38. 38. How is water transported from the xylem in the roots to the leaves? 38
39. 39. In plants Plants only use about 5 to 10% of the water they uptake for plant growth and cellular use 39
40. 40. Eg. If a huge tree takes in 1200L of water a day and only uses 10%... Where did the other 90% went to? 40
41. 41. Water is loss to the environment mostly through the?.... 42
42. 42. Let take a look at the cross section of a leaf 43
43. 43. A large percentage of water that is absorbed is lost by evaporation through the stomata 44
44. 44. This process of water vapour being lost mainly through the stomata is known as transpiration 45
45. 45. How does transpiration help to bring water in the roots to the leaves? 46
46. 46. Properties of water H HO Cohesive.Attracts to one another Adhesive.Attracts to other substances 47
47. 47. This creates a suction force which pulls water up the xylem vessels This suction force due to transpiration is known as transpiration pull 48 In the stem, water moves up the xylem primarily via transpiration pull
48. 48. Transport in Plants 50
49. 49. 51 Purpose of Transpiration Cools the leaves Transport water & minerals from the roots to the leaves
50. 50. Explain the factors affecting the rate of transpiration Learning Objectives 52
51. 51. Factors Affecting Rate of Transpiration Temperature Humidity Wind Light 53
52. 52. Which of the following correctly states the pathway in which water molecules leave a plant during transpiration? A ) Palisade mesophyll vascular bundle intercellular air spaces stomata B ) Spongy mesophyll intercellular air spaces stomata epidermis cuticle C ) Vascular bundle spongy mesophyll intercellular air spaces stomata D ) Vascular bundle intercellular air spaces stomata epidermis cuticle ( ) microQUESTION9.8
53. 53. Measuring Rate of Transpiration
54. 54. Experiment set-up to measure the rate of transpiration (1) (2) In set-up (1), the loss of water by evaporation is avoided by adding a layer of oil on the surface of the water. Water is lost through the leaves of the plant and will result in the mass of the test tube decreasing. Rate of transpiration = Loss in mass (g) (g/h) Time taken (h) Set-up (2), known as potometer. The suction force generated by transpiration will cause the air bubble in the graduated capillary tube to move to the left to indicate volume of water absorbed to replace water loss. Rate of transpiration = Loss in volume (cm3) (cm3/h) Time taken (h)
55. 55. 57
56. 56. 58
57. 57. 59 Distance moved
58. 58. Adaptation of Marram grass http://www.youtube.com/watch?v=Dv1-NDw49Vw
59. 59. The transpiration rate of a plant varies throughout the day, depending on the environmental conditions. Which of the following sets of environmental conditions would result in the highest transpiration rate? microQUESTION9.9 Temperature Cloud cover Humidity Wind speed A High Maximum High High B Low Minimal Low Low C High Minimal Low High D Low Maximum High Low ( )
60. 60. Wilting
61. 61. Wilting Excessive transpiration causes a plant to wilt. Wilting occurs when a plant loses more water through the leaves, than it absorbs through the roots.
62. 62. Wilting Turgor pressure in the mesophyll cells in the leaf helps to support the leaf and keep the leaf firm and widely spread out to absorb sunlight for photosynthesis. In strong sunlight, excess transpiration causes cells to lose turgor pressure and become flaccid.
63. 63. Wilting Excessive Transpiration Guard cells become flaccid * Rate of photosynthesis decrease Stomata close
64. 64. Wilting- Advantage Less surface area exposed to sunlight Guard cells flaccid Stomata closes Transpiration is reduced
65. 65. Wilting- Disadvantage Guard cells become flaccid Stomata closes Carbon Dioxide intake is reduced Rate of Photosynthesis decreases