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AP Biology 2011-2012 Chapter 36: Transport in Plants.

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Presentation on theme: "AP Biology 2011-2012 Chapter 36: Transport in Plants."— Presentation transcript:

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2 AP Biology Chapter 36: Transport in Plants

3 AP Biology Overview: Underground Plants Stone plants (Lithops) are adapted to life in the desert Two succulent leaf tips are exposed above ground; the rest of the plant lives below ground

4 AP Biology The success of plants depends on their ability to gather and conserve resources from their environment The transport of materials is central to the integrated functioning of the whole plant Overview: Underground Plants (cont.)

5 AP Biology Plant Evolution Algal ancestors absorbed minerals and CO 2 directly from water Early nonvascular land plants lived in shallow water and had aerial shoots Natural selection favored taller plants with flat appendages, multicellular branching roots, and efficient transport evolution of xylem & phloem made long-distance transport of water, minerals, and products of photosynthesis

6 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?

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

8 AP Biology Apoplast & Symplast The apoplast consists of everything external to the plasma membrane cell walls, extracellular spaces, and the interior of vessel elements and tracheids The symplast consists of the cytosol of the living cells in a plant, as well as the plasmodesmata

9 AP Biology Figure 36.6 Cell wall Cytosol Plasmodesma Plasma membrane Apoplastic route Symplastic route Transmembrane route Key Apoplast Symplast

10 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

11 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

12 AP Biology Figure 36.7 CYTOPLASMEXTRACELLULAR FLUID ATP Proton pump Hydrogen ion H+H+ (a) H + and membrane potential H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H (b) H + and cotransport of neutral solutes H + /sucrose cotransporter Sucrose (neutral solute) H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ S S S S S S (c) H + and cotransport of ions Nitrate H + NO 3 cotransporter H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ NO (d) Ion channels Potassium ion Ion channel K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K

13 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

14 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

15 AP Biology Endodermis & Casparian strip

16 AP Biology Root anatomy dicotmonocot

17 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

18 AP Biology Roots Fungus Figure 36.5

19 AP Biology Mycorrhizae

20 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

21 AP Biology can flow 1m/hr Pressure flow in phloem Mass flow hypothesis source to sink flow direction of transport in phloem is dependent on plants 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

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

23 AP Biology Maple sugaring

24 AP Biology Figure 36.8 Solutes have a negative effect on by binding water molecules. Pure water at equilibrium H2OH2O Adding solutes to the right arm makes lower there, resulting in net movement of water to the right arm: H2OH2O Pure water Membrane Solutes Positive pressure has a positive effect on by pushing water. Pure water at equilibrium H2OH2O H2OH2O Positive pressure Applying positive pressure to the right arm makes higher there, resulting in net movement of water to the left arm: Solutes and positive pressure have opposing effects on water movement. Pure water at equilibrium H2OH2O H2OH2O Positive pressure Solutes In this example, the effect of adding solutes is offset by positive pressure, resulting in no net movement of water: Negative pressure (tension) has a negative effect on by pulling water. Pure water at equilibrium H2OH2O H2OH2O Negative pressure Applying negative pressure to the right arm makes lower there, resulting in net movement of water to the right arm:

25 AP Biology Outside air MPa 7.0 MPa 1.0 MPa 0.8 MPa 0.6 MPa 0.3 MPa Leaf (air spaces) Leaf (cell walls) Trunk xylem Soil Water potential gradient Xylem sap Mesophyll cells Stoma Water molecule Atmosphere Transpiration Xylem cells Adhesion by hydrogen bonding Cell wall Cohesion and adhesion in the xylem Cohesion by hydrogen bonding Water molecule Root hair Soil particle Water Water uptake from soil Figure 36.13

26 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

27 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 plants need for CO 2 for photosynthesis


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