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Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
Chapter 36 - Plant Transport
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Chapter 36 - Plant Transport

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  • 1. Transport in PlantsAP Biology 2006-2007
  • 2. Review: Transport proteins  Facilitate diffusion via carrier or selective channel formation  Carrier proteins  Selective to solute molecule  Produces conformational change of protein  Releases molecule to opposite side  Selective channel  Passageways for certain solutes  May be gated - open/closeAP Biology
  • 3. Transport in plants  H2O & minerals  transport in xylem  transpiration  evaporation, adhesion & cohesion  negative pressure  Sugars  transport in phloem  bulk flow  Calvin cycle in leaves loads sucrose into phloem  positive pressure Why does over-watering  Gas exchange kill a plant?  photosynthesis  CO2 in; O2 out  stomates  respiration  O2 in; CO2 out  roots exchange gases within air spaces in soilAP Biology
  • 4. Ascent of xylem fluid Transpiration pull generated by leafAP Biology
  • 5. Water & mineral absorption  Water absorption from soil  osmosis  aquaporins  Mineral absorption  active transport  proton pumps aquaporin  active transport of H+ root hair AP Biology H2Oproton pumps
  • 6. Mineral absorption  Proton pumps  active transport of H+ ions out of cell  chemiosmosis  H+ gradient  creates membrane potential  difference in charge  drives cation uptake  creates gradient  cotransport of other solutes against their gradientAP Biology
  • 7. Water flow through root  Porous cell wall  water can flow through cell wall route & not enter cells  plant needs to force water into cells Casparian stripAP Biology
  • 8. Controlling the route of water in root  Endodermis  cell layer surrounding vascular cylinder of root  lined with impermeable Casparian strip  forces fluid through selective cell membrane  filtered & forced into xylem cellsAP Biology
  • 9. Mycorrhizae increase absorption  Symbiotic relationship between fungi & plant  symbiotic fungi greatly increases surface area for absorption of water & minerals  increases volume of soil reached by plant  increases transport to host plantAP Biology
  • 10. MycorrhizaeAP Biology
  • 11. Control of Stomates Epidermal cell Nucleus Guard cell Chloroplasts  Uptake of K+ ions K+ K+ by guard cells H2O H2O H2O H2O  proton pumps K+ K+  water enters by K+ K+ osmosis H2O H2O H2O H2O  guard cells K+ K+ become turgid Thickened inner  Loss of K+ ions cell wall (rigid) by guard cells  water leaves by osmosis H2O H2O H2O H2O K+ K+ K+ K+  guard cells become flaccid Stoma open Stoma closed water moves water moves out into guard cells of guard cellsAP Biology
  • 12. Water potential and osmosis  Osmosis  Net absorption or loss of water  Water potential ()  Combined effects of solute concentration and pressure  Determines direction of water movement  Water moves from areas of high water potential to areas of low water potential  0 Mpa = pure water open at sea level &AP Biology room temp
  • 13. Water potential ()  Solute potential (s)  Proportional to number of dissolved solutes  Osmotic potential  s = 0 in pure water  s = -0.23 in 0.1M solution of sugar  Addition of solutes lowers the   Pressure Potential (P)  Physical pressure on a solution  Can be + or –  Water in xylem is often negative  Water in cell is often positive  Additional pressure raises the AP Biology
  • 14.  = p + s  p - pressure potential  s - solute potential = osmotic potential  Flaccid cell (P = 0) placed in hypertonic solution will lose water via osmosis  Plasmolysis - protoplast pulls away from cell walls  Same cell placed within a hypotonic solution will gain water via osmosis = turgidAP Biology
  • 15. Transport of sugars in phloem  Loading of sucrose into phloem  flow through cells via plasmodesmata  proton pumps  cotransport of sucrose into cells down proton gradientAP Biology
  • 16. Pressure flow in phloem  Mass flow hypothesis  “source to sink” flow  direction of transport in phloem is dependent on plant’s needs can flow  phloem loading 1m/hr  active transport of sucrose into phloem  increased sucrose concentration decreases H2O potential  water flows in from xylem cells  increase in pressure due to increase in H2O causes flowAP Biology
  • 17. Experimentation  Testing pressure flow hypothesis  using aphids to measure sap flow & sugar concentration along plant stemAP Biology

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