Plant transport ppt

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Plant transport ppt

  1. 2. Recall <ul><li>Transport Mechanism </li></ul><ul><ul><li>Passive vs. Active </li></ul></ul><ul><li>Plant Transport Tissues </li></ul><ul><ul><li>Xylem </li></ul></ul><ul><ul><li>Phloem </li></ul></ul>
  2. 3. Transport Mechanisms <ul><li>Passive transport </li></ul><ul><ul><li>Passive Diffusion </li></ul></ul><ul><ul><li>Facilitated Diffusion </li></ul></ul><ul><ul><li>Osmosis </li></ul></ul><ul><li>Active transport </li></ul><ul><li>Bulk transport </li></ul>
  3. 4. Plant Transport Tissues <ul><li>Xylem </li></ul><ul><ul><li>Vessel elements </li></ul></ul><ul><ul><li>Tracheids </li></ul></ul><ul><li>Phloem </li></ul><ul><ul><li>Sieve tube member </li></ul></ul><ul><ul><li>Companion cells </li></ul></ul>
  4. 5. Problem of Terrestrial Plants <ul><li>Ancestral plants: transport is through diffusion </li></ul><ul><li>Modern plants: transport from roots to shoots </li></ul><ul><ul><li>Long distance transport </li></ul></ul>Figure 36.1
  5. 6. Transport in Plants <ul><li>Three scales of plant transport </li></ul><ul><ul><li>Intracellular </li></ul></ul><ul><ul><ul><li>Epidermal cells </li></ul></ul></ul><ul><ul><li>Short distance: cell-to-cell </li></ul></ul><ul><ul><ul><li>At the levels of tissues and organs </li></ul></ul></ul><ul><ul><li>Long distance: xylem and phloem </li></ul></ul>
  6. 7. <ul><li>A variety of physical processes </li></ul><ul><ul><li>Are involved in the different types of transport </li></ul></ul>Minerals H 2 O CO 2 O 2 CO 2 O 2 H 2 O Sugar Light Sugars are transported as phloem sap to roots and other parts of the plant. Figure 36.2 Sugars are produced by photosynthesis in the leaves. 5 6 Through stomata, leaves take in CO 2 and expel O 2 . The CO 2 provides carbon for photosynthesis. Some O 2 produced by photosynthesis is used in cellular respiration. 4 Transpiration, the loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upward. 3 Water and minerals are transported upward from roots to shoots as xylem sap. 2 Roots absorb water and dissolved minerals from the soil. 1 Roots exchange gases with the air spaces of soil, taking in O 2 and discharging CO 2 . In cellular respiration, O 2 supports the breakdown of sugars. 7
  7. 8. Effects of Differences in Water Potential <ul><li>To survive </li></ul><ul><ul><li>Plants must balance water uptake and loss </li></ul></ul><ul><li>Osmosis </li></ul><ul><ul><li>Determines the net uptake or water loss by a cell </li></ul></ul><ul><ul><li>Is affected by solute concentration and pressure </li></ul></ul>
  8. 9. <ul><li>Water potential </li></ul><ul><ul><li>Is a measurement that combines the effects of solute concentration and pressure </li></ul></ul><ul><ul><li>Determines the direction of movement of water </li></ul></ul><ul><li>Water </li></ul><ul><ul><li>Flows from regions of high water potential to regions of low water potential </li></ul></ul><ul><ul><li>Both pressure and solute concentrations affect water potential </li></ul></ul>
  9. 10. <ul><li>Water potential </li></ul><ul><ul><li>Affects uptake and loss of water by plant cells </li></ul></ul><ul><li>If a flaccid cell is placed in an environment with a higher solute concentration </li></ul><ul><ul><li>The cell will lose water and become plasmolyzed </li></ul></ul>Figure 36.6a 0.4 M sucrose solution: Initial flaccid cell: Plasmolyzed cell at osmotic equilibrium with its surroundings  P = 0  S = 0.7  P = 0  S = 0.9  P = 0  S = 0.9  =  0.9 MPa  = 0.7 MPa  =  0.9 MPa
  10. 11. <ul><li>If the same flaccid cell is placed in a solution with a lower solute concentration </li></ul><ul><ul><li>The cell will gain water and become turgid </li></ul></ul>Distilled water: Initial flaccid cell: Turgid cell at osmotic equilibrium with its surroundings  P = 0  S = 0.7  P = 0  S = 0  P = 0.7  S = 0.7 Figure 36.6b  = 0.7 MPa  = 0 MPa  = 0 MPa
  11. 12. How water moves <ul><li>Plasmodesmata </li></ul><ul><li>Symplast </li></ul><ul><li>apoplast </li></ul>
  12. 13. Bulk Flow in Long-Distance Transport <ul><li>In bulk flow </li></ul><ul><ul><li>Movement of fluid in the xylem and phloem is driven by pressure differences at opposite ends of the xylem vessels and sieve tubes </li></ul></ul>
  13. 14. The xylem sap and phloem sap <ul><li>Xylem sap </li></ul><ul><ul><li>Root pressure </li></ul></ul><ul><ul><li>Transpiration-cohesion-tension mechanism </li></ul></ul><ul><li>Phloem sap </li></ul><ul><ul><li>Pressure Flow Theory </li></ul></ul><ul><ul><ul><li>Translocation </li></ul></ul></ul>

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