CBP PP6 Plant Transport

CBP PP6 Plant Transport - CBP PP6 Plant Transport

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LR/CC/CBP Water relations Plants need water for L Photosynthesis L Maintaining cell environment L Transport But only 5% of water uptake is used for growth
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LR/CC/CBP Transpiration Loss of water as vapour > 90% from leaves < 10% from stem through lenticels In the leaf L 90% of transpiration is stomatal L >10% cuticular
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LR/CC/CBP
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LR/CC/CBP Factors affecting transpiration Stomatal resistance Boundary layer thickness Vapour pressure gradient External L Humidity L Temperature L Wind
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LR/CC/CBP What use is transpiration? Uses enormous amounts of water Substrate for photosynthesis Evaporative cooling of leaves Transport from the root Inevitable consequence of leaf gas- exchange
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LR/CC/CBP
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LR/CC/CBP Control of Transpiration Stomata open when guard cells turgid L Proton pump H + /ATPase pumps protons out L K + ions migrate in, water enters by osmosis L If pump stops, K + migrates out, guard cells lose water and close L Pump Control L +ve from blue light L -ve leaf [CO 2 ] L -ve Abscisic acid, from wilting cells
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LR/CC/CBP Water transport Occurs along xylem vessels To reach the top of a tall tree (100m high) L Hydrostatic pressure = 1MPa L Resistance to flow = 1MPa L Total force required = 2 MPa
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CBP PP6 Plant Transport - CBP PP6 Plant Transport

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