Vascular tissues <ul><li>Xylem  </li></ul><ul><li>Phloem </li></ul>Copyright © 2010 All Rights Reserved
Copyright © 2010 All Rights Reserved
Xylem tissue <ul><li>Function </li></ul><ul><li>transports water and mineral salts from  </li></ul><ul><li>roots  ->   ste...
Xylem Copyright © 2010 All Rights Reserved
Different types of lignin deposits annular rings spiral/helical bands pitted Copyright © 2010 All Rights Reserved
Phloem tissue <ul><li>Transports manufactured food (sucrose and amino acids),  usually  from </li></ul><ul><li>  leaves  -...
Sieve tube  <ul><li>Consists of  sieve tube cells </li></ul><ul><li>Cross walls separating the cells are perforated by min...
Sieve plates Copyright © 2010 All Rights Reserved
Companion cells <ul><li>accompanies sieve tube cells </li></ul><ul><li>helps keep it alive (sieve tubes have  degenerate p...
Structure of phloem Copyright © 2010 All Rights Reserved
Transport of solutes in the phloem <ul><li>Sugars are  actively loaded  into the phloem in the leaves, and  actively remov...
Pressure flow concept Copyright © 2010 All Rights Reserved
<ul><li>Translocation studies </li></ul>Translocation : transport of a substance through a plant from the site of absorpti...
Lesson Objectives <ul><li>Translocation studies </li></ul><ul><li>Structure of roots </li></ul><ul><li>Transport of water ...
1) Use of aphids <ul><li>Proboscis penetrate leaf/stem of plant </li></ul><ul><li>Anaesthetize aphid with CO 2 </li></ul><...
More on aphids…  Copyright © 2010 All Rights Reserved
More on aphids… Copyright © 2010 All Rights Reserved
2) Use of isotopes <ul><li>14 C radioactive carbon isotope  </li></ul><ul><li>Presence detected by X-ray photographic film...
Use of isotopes  (continued…) Copyright © 2010 All Rights Reserved sunlight chlorophyll Carbon dioxide + water  ->  glucos...
Use of isotopes  (continued…) Copyright ©  2010 All Rights Reserved
Transport of water Copyright © 2010 All Rights Reserved
Copyright © 2010 All Rights Reserved
Structure of root Copyright © 2010 All Rights Reserved
Structure of root: Zone of cell division (growing zone):   actively dividing young cells (mitosis) Zone of elongation:   c...
Entry of water into the plant Thin film around particle = dilute solution of mineral salts Copyright © 2010 All Rights Res...
Entry of  water  from soil Plasma membrane of root hair cell Osmosis Copyright © 2010 All Rights Reserved Sap in root hair...
Low water potential High water potential Copyright © 2010 All Rights Reserved
Transport of water from  root hair  ->  xylem Copyright © 2010 All Rights Reserved
Transport of mineral salts Copyright © 2010 All Rights Reserved
Transport of  mineral salts Plasma membrane of root hair cell Diffusion Copyright © 2010 All Rights Reserved Sap in root h...
Why diffusion and not osmosis? Copyright © 2010 All Rights Reserved Movements are over  large   distances The movement is ...
<ul><li>Qn: Can the root hair absorb ions if the concentration is higher in the root hair sap compared to the soil solutio...
High water potential Low water potential Copyright © 2010 All Rights Reserved
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Chapter 9 Transport in Plants Lesson 2 - Xylem and Phloem structure and function

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  • Transport of sugars and dissolved solutes in the phloem is kind of like water movement in the xylem in reverse. Sugars are actively pumped into the phloem sieve tube cells in the leaf. Thus the solute potential increases, making the water potential of the sieve tube cell more negative and water is drawn in from surrounding cells. In the root (and other tissues actively abstracting sugars), sugars are removed, lowering the water potential. This difference in water potential between the leaves which are actively uploading sugars, and the roots and other tissues actively removing them drives a bulk flow of water in the phloem with the sugars and other dissolved solutes. In the leaves, the concentration of sucrose in the sieve tube cells can reach as much a 1molar. This is equivalent to 10 atmospheres of pressure which can drive a bulk flow of water and sugars through the sieve tubes.
  • Chapter 9 Transport in Plants Lesson 2 - Xylem and Phloem structure and function

    1. 1. Vascular tissues <ul><li>Xylem </li></ul><ul><li>Phloem </li></ul>Copyright © 2010 All Rights Reserved
    2. 2. Copyright © 2010 All Rights Reserved
    3. 3. Xylem tissue <ul><li>Function </li></ul><ul><li>transports water and mineral salts from </li></ul><ul><li>roots -> stem -> leaves </li></ul><ul><li>Unidirectional </li></ul><ul><li>composed of hollow, nonliving cells (continuous lumen) </li></ul><ul><li>provides mechanical support to plant because of lignified walls </li></ul>Copyright © 2010 All Rights Reserved
    4. 4. Xylem Copyright © 2010 All Rights Reserved
    5. 5. Different types of lignin deposits annular rings spiral/helical bands pitted Copyright © 2010 All Rights Reserved
    6. 6. Phloem tissue <ul><li>Transports manufactured food (sucrose and amino acids), usually from </li></ul><ul><li> leaves -> other parts of the plant </li></ul><ul><li>Bi-directional </li></ul><ul><li>Consists mainly of </li></ul><ul><ul><li>sieve tubes </li></ul></ul><ul><ul><li>companion cells </li></ul></ul>Copyright © 2010 All Rights Reserved
    7. 7. Sieve tube <ul><li>Consists of sieve tube cells </li></ul><ul><li>Cross walls separating the cells are perforated by minute pores ( sieve plates ) </li></ul><ul><li>Transport occurs through cytoplasm by diffusion and active transport </li></ul>Copyright © 2010 All Rights Reserved Longitudinal Transverse
    8. 8. Sieve plates Copyright © 2010 All Rights Reserved
    9. 9. Companion cells <ul><li>accompanies sieve tube cells </li></ul><ul><li>helps keep it alive (sieve tubes have degenerate protoplasm ) </li></ul><ul><li>assist in transport of manufactured food </li></ul>Copyright © 2010 All Rights Reserved
    10. 10. Structure of phloem Copyright © 2010 All Rights Reserved
    11. 11. Transport of solutes in the phloem <ul><li>Sugars are actively loaded into the phloem in the leaves, and actively removed from the phloem in parts of the plant like the roots that need sugar </li></ul><ul><li>Any sugar that leaks out is pumped back in by the companion cells </li></ul><ul><li>Water follows by osmosis, and the difference in water potential between the leaves (high sucrose, low water potential) and the roots (low sucrose, high water potential) drives a bulk flow of the sugar solution </li></ul>Copyright © 2010 All Rights Reserved
    12. 12. Pressure flow concept Copyright © 2010 All Rights Reserved
    13. 13. <ul><li>Translocation studies </li></ul>Translocation : transport of a substance through a plant from the site of absorption to other parts of the plant Copyright © 2010 All Rights Reserved
    14. 14. Lesson Objectives <ul><li>Translocation studies </li></ul><ul><li>Structure of roots </li></ul><ul><li>Transport of water and mineral salts into roots </li></ul><ul><li>3 mechanisms of xylem transport </li></ul><ul><li>Root pressure </li></ul><ul><li>Capillary action </li></ul><ul><li>Transpiration pull </li></ul>Copyright © 2010 All Rights Reserved
    15. 15. 1) Use of aphids <ul><li>Proboscis penetrate leaf/stem of plant </li></ul><ul><li>Anaesthetize aphid with CO 2 </li></ul><ul><li>Body cut off leaving proboscis in plant tissue </li></ul><ul><li>Liquid exude from proboscis cut end </li></ul><ul><li>Analysis shows liquid </li></ul><ul><li>= sucrose + amino acids </li></ul>Copyright © 2010 All Rights Reserved
    16. 16. More on aphids… Copyright © 2010 All Rights Reserved
    17. 17. More on aphids… Copyright © 2010 All Rights Reserved
    18. 18. 2) Use of isotopes <ul><li>14 C radioactive carbon isotope </li></ul><ul><li>Presence detected by X-ray photographic film </li></ul>Pg. 178 textbook Copyright © 2010 All Rights Reserved
    19. 19. Use of isotopes (continued…) Copyright © 2010 All Rights Reserved sunlight chlorophyll Carbon dioxide + water -> glucose + oxygen + water vapour C O 2 + H 2 O -> C 6 H 12 O 6 + O 2 + H 2 O Sunlight chlorophyll 14 C O 2 + H 2 O -> 14 C 6 H 12 O 6 + O 2 + H 2 O Sunlight chlorophyll
    20. 20. Use of isotopes (continued…) Copyright © 2010 All Rights Reserved
    21. 21. Transport of water Copyright © 2010 All Rights Reserved
    22. 22. Copyright © 2010 All Rights Reserved
    23. 23. Structure of root Copyright © 2010 All Rights Reserved
    24. 24. Structure of root: Zone of cell division (growing zone): actively dividing young cells (mitosis) Zone of elongation: cells elongate -> increase root length Root cap: Covers the root tip -> protects cells from injury Zone of maturation/root hairs: Region where most water + mineral salts absorbed Copyright © 2010 All Rights Reserved
    25. 25. Entry of water into the plant Thin film around particle = dilute solution of mineral salts Copyright © 2010 All Rights Reserved
    26. 26. Entry of water from soil Plasma membrane of root hair cell Osmosis Copyright © 2010 All Rights Reserved Sap in root hair Soil solution Strong solution of sugars and salts Dilute solution of mineral salts Low water potential Higher water potential H 2 O
    27. 27. Low water potential High water potential Copyright © 2010 All Rights Reserved
    28. 28. Transport of water from root hair -> xylem Copyright © 2010 All Rights Reserved
    29. 29. Transport of mineral salts Copyright © 2010 All Rights Reserved
    30. 30. Transport of mineral salts Plasma membrane of root hair cell Diffusion Copyright © 2010 All Rights Reserved Sap in root hair Soil solution Mineral concentration low Mineral concentration high Mineral salts
    31. 31. Why diffusion and not osmosis? Copyright © 2010 All Rights Reserved Movements are over large distances The movement is over a short distance Occurs in liquids as well as gases Occurs only in liquids It is a fast process It is a slow process No such membrane is required It requires partially permeable membrane Flow of either solute or solvent molecules is in both directions It involves flow of solvent molecules in one direction Diffusion Osmosis
    32. 32. <ul><li>Qn: Can the root hair absorb ions if the concentration is higher in the root hair sap compared to the soil solution? </li></ul>Transport of mineral salts Active transport Yes!!! Copyright © 2010 All Rights Reserved Sap in root hair Soil solution Plasma membrane of root hair cell Mineral concentration high Mineral concentration low Mineral salts?
    33. 33. High water potential Low water potential Copyright © 2010 All Rights Reserved

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