Transport system in plants

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Biology GCE O level syllabus: Transport system in Plants

Include: Xylem, Phloem, Entry of water into plant and so forth...

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Transport system in plants

  1. 1. + Transport System in Plants Prepared By: Faiz Abdullah
  2. 2. + Transport System in Flowering plants Flowering plants have a system of vessels that runs up and down the plants carrying materials.  These vessels are called transport or vascular tissues.  YOU SHOULD KNOW TWO TYPES OF TRANSPORT TISSUES: ① Xylem ② Phloem
  3. 3. + O Level question: WHAT IS THE DIFFERENCE BETWEEN XYLEM AND PHLOEM TISSUES?
  4. 4. + XYLEM 1) FUNCTION 2) STRUCTURE 3) ADAPTATION
  5. 5. + XYLEM -- Function salts FROM roots to stems to leaves. II. Provide for the stem.
  6. 6. + XYLEM – STRUCTURE & ADAPTATION  Consists mainly of xylem vessels (long hollow tube)  Made up of many DEAD CELLS  Inner walls of the xylem vessels are STRENGTHENED by LIGNIN  structural or mechanical support  Has empty lumen without protoplasm or cross walls.  Narrow lumen for capillary action (not the same as transpirational pull) Structure ADAPTATION
  7. 7. + PHLOEM FUNCTION: Transports manufactured food (sucrose+amino acid) from leaves to other parts of plant. STRUCTURE:  Consists of sieve tubes and companion cells. Sieve tube consists of columns of elongated, thin walled living cells called sieve tube cells/elements. They have cross walls with many holes or pores  sieve plates Each sieve tube has a companion cell ADAPTATIONS:  Companion cells have many mitochondria provide energy needed to load sugars from mesophyll cells into sieve tubes by active transport.  Sieve pores allow rapid flow of manufactured food through sieve tubes
  8. 8. + Phloem Check out the: 1. Sieve tubes 2. Sieve pores 3. Companion cell 4. Sieve plates
  9. 9. + ROOT The root is divided into several regions:  The root cap: located at the tip of the root. root during growth through the soil.  Zone of cell multiplication/division: zone  Zone of elongation: The region where newly divided cells elongate of root.  Zone of maturation: consists of root hairs, which increases surface area for rapid and efficient uptake of water and salts
  10. 10. + Transverse section of the root Take note of the labels
  11. 11. + Vascular tissue in stem: USEFUL TERMS In dicotyledonous stem: - Xylem and Phloem grouped together vascular bundle - Vascular bundles are arranged in a ring around a central region pith - Phloem lies outside the xylem with a tissue in between cambium - Region between vascular bundles and the epidermis cortex - Stem is covered by a layer of cells  epidermis
  12. 12. + Vascular tissues in a stem • Cambium cells can divide and differentiate to form new xylem and phloem tissues thickening the stem • Cortex and pith serve to store up food substances such as starch • Epidermal cells are covered by a waxy, waterproof cuticle that greatly reduces evaporation of water from the stem
  13. 13. + ENTRY OF WATER INTO PLANT FROM ROOT  STEM  LEAVES
  14. 14. + To understand the movement of water: We need to know how WATER BEHAVES?
  15. 15. + PROPERTIES OF WATER COHESION Water molecules are attracted to one another by a force  cohesion ADHESION Water tends to stick to the inner surface of the walls of xylem vessels  adhesion
  16. 16. + Analogy
  17. 17. + 1) Movement of water into root hair cells
  18. 18. + 1) Movement of water into root hairs: Movement of substances Water:  OSMOSIS  water from the soil move into the root hairs via osmosis. Mineral Ions:  Diffusion: Ions diffuse from a high concentration to a low concentration.  Active transport: minerals, such as Mg and N, which are in LOWER concentrations in SOIL, enter the root cell via active transport OSMOSIS FOR WATER ONLY FOLLOWS CONCENTRATION GRADIENT NO NEED ENERGY DIFFUSION FOLLOWS CONCENTRATION GRADIENT ACTIVE TRANSPORT NEEDS ENERGY (ATP) AGAINST CONCENTRATION GRADIENT
  19. 19. + 1) Movement of water into root hairs: Adaptations a) Root hair is long and narrow  increase surface area to absorb more water and mineral salts by root hair cell b) Cell surface membrane prevents cell sap (vacuole) from leaking out. Also, Cell sap has lower water potential. c) Root hair is living  can provide energy for active transport
  20. 20. + 1) Movement of water into root hairs Once water has entered a root hair, it passes from one cell to another by Osmosis. This goes on and on and on……..and on….until the water reaches the xylem At the same time, ions diffuse inwards through the cells of the root until they reach the xylem
  21. 21. + 2) Movement of water UP the stem
  22. 22. + 2) Movement of water up the stem 1) Transpiration pull Other forces involved: 2) Root pressure (Guttation) 3) Capillarity 4) Adhesion and cohesion of water molecules
  23. 23. + Transpiration
  24. 24. + 2) Root pressure (Guttation)  At night, mineral ions are actively transported into the xylem vessel.  This lowers the water potential in the xylem vessel.  Therefore, water passes from the living cells into the xylem by osmosis and flows upwards root pressure  Guttation stops when transpiration begins
  25. 25. + 3) Capillary action When water reaches the xylem vessel, Its NARROW LUMEN allows water to move up the stem  process known as capillarity
  26. 26. + 3) MOVEMENT OF WATER THROUGH THE LEAVES
  27. 27. + 3) Movement of water through the leaves  Mesophyll cells evaporate large quantities of water into the intercellular air spaces  Water vapor diffuses out of the leaves through the STOMATA  Small amount of water is lost through the waxy CUTICLE
  28. 28. + What is happening inside leaves..
  29. 29. + TRANSPIRATION IMPORTANCE AND ITS FACTORS
  30. 30. + TRANSPIRATION IS INEVITABLE/UNAVOIDABLE
  31. 31. + IMPORTANCE OF TRANSPIRATION  Enables water to move up the stem to the plants: water can be used for photosynthesis and keep the cells turgid (help leaves spread out widely to trap more light)  Evaporation of water cools the plant.  Enables plant to obtain mineral salts. Why do you think transpiration can help the plant?
  32. 32. + Transpiration- features that facilitate water loss (a) Mesophyll cells with wet surfaces and large total surface area (b) Large intercellular spaces in the leaf Other factors: a) Greater number in stomata b) Stomata exposed directly to sunlight or remain open
  33. 33. + Environmental factors that affect transpiration ① Temperature ② Air Humidity ③ Wind ④ Light intensity ⑤ Carbon dioxide concentration Guess!!! Guess!!! Guess!!! Guess!!! Guess!!!
  34. 34. + Pictures for transpiration factors
  35. 35. + WILTING 
  36. 36. + Wilting
  37. 37. + WHEN? And WHY? Wilting occurs when: RATE OF TRANSPIRATION EXCEEDS RATE OF ABSORBTION OF WATER  Cells lose their turgidity  Cells become flaccid  Plant wilts
  38. 38. + WHY wilting?  Water becomes a limiting factor.  Wilting causes a decrease in the rate of photosynthesis Water is getting less  Wilting makes the leaves fold less area exposed to sunlight  The greater the size of stomatal opening, the greater the water loss
  39. 39. + The transport or movement of food substances in the phloemTRANSLOCATION
  40. 40. +
  41. 41. + EXPERIMENT Investigation: to show water travels up the stem in the xylem Procedure: 1. Set up the apparatus as shown. 2. Allow the plant to stand immersed in the red food dye for 3-4 hours 3. Observe the color change in the stem 4. Cut thin transverse section of the stem 5. Observe under a microscope
  42. 42. + Observation The red dye will appear in the stem and leaves. Xylem tissue has been stained red

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