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AP Biology 2006-2007 Transport in Plants AP Biology Transport in plants  H 2 O & minerals  transport in xylem  transpiration  evaporation, adhesion.

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Presentation on theme: "AP Biology 2006-2007 Transport in Plants AP Biology Transport in plants  H 2 O & minerals  transport in xylem  transpiration  evaporation, adhesion."— Presentation transcript:

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2 AP Biology Transport in Plants

3 AP Biology Transport in plants  H 2 O & 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  Gas exchange  photosynthesis  CO 2 in; O 2 out  stomates  respiration  O 2 in; CO 2 out  roots exchange gases within air spaces in soil Why does over-watering kill a plant?

4 AP Biology Ascent of xylem fluid Transpiration pull generated by leaf

5 AP Biology Water & mineral absorption  Water absorption from soil  osmosis  aquaporins  Mineral absorption  active transport  proton pumps  active transport of H + H2OH2O root hair aquaporin proton pumps

6 AP Biology 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 gradient

7 AP Biology 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 strip

8 AP Biology 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 cells Aaaah … Structure – Function yet again!

9 AP Biology Root anatomy dicotmonocot

10 AP Biology 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 plant

11 AP Biology Mycorrhizae

12 AP Biology Transport of sugars in phloem  Loading of sucrose into phloem  flow through cells via plasmodesmata  proton pumps  cotransport of sucrose into cells down proton gradient

13 AP Biology On a plant … What ’ s a source … What ’ s a sink? can flow 1m/hr Pressure flow in phloem  Mass flow hypothesis  “source to sink” flow  direction of transport in phloem is dependent on plant’s needs  phloem loading  active transport of sucrose into phloem  increased sucrose concentration decreases H 2 O potential  water flows in from xylem cells  increase in pressure due to increase in H 2 O causes flow

14 AP Biology Experimentation  Testing pressure flow hypothesis  using aphids to measure sap flow & sugar concentration along plant stem

15 AP Biology Maple sugaring

16 AP Biology Don’t get mad… Get answers!! Ask Questions!

17 AP Biology Endodermis & Casparian strip

18 AP Biology Chloroplasts Epidermal cell Nucleus Guard cell Thickened inner cell wall (rigid) Stoma openStoma closed H2OH2O water moves into guard cells H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O Control of Stomates K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ water moves out of guard cells  Uptake of K + ions by guard cells  proton pumps  water enters by osmosis  guard cells become turgid  Loss of K + ions by guard cells  water leaves by osmosis  guard cells become flaccid

19 AP Biology Control of transpiration  Balancing stomate function  always a compromise between photosynthesis & transpiration  leaf may transpire more than its weight in water in a day…this loss must be balanced with plant’s need for CO 2 for photosynthesis


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