Lecture6

Lecture6 - Summary of path and driving force of water and...

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Summary of path and driving force of water and mineral movement • Water and minerals move in transpiration stream: roots -> leaves -> air • Massive water flux (Ex. 15m tall tree transpires 220 liters/hr) • Driving force for movement is water potential ( Ψ ) gradient • Water column is (usually) under tension • Flow rate (up to 45 m/hr) determined by gradient strength and resistance • Majority of movement is apoplastic, but all must enter symplast at endodermal layer • Entry into symplast is opportunity for selectivity, involves active transport of ions • Stomata = on/off switch for transpiration stream, depends on osmotically driven turgor changes Action potentials = sudden, transient major changes in membrane potential Do plants have action potentials? Membrane potential=charge difference between inside and outside of cell, due to asymmetric distribution of ions Pumping H+ out of cell results in negative resting potential Changes in pump activity alter membrane potential Uptake of K+ reduces negative charge inside of cell: depolarization K+ efflux or anion uptake increases negative charge inside of cell: hyperpolarization Action potentials = sudden, transient major changes in membrane potential Venus flytrap “Sensitive plant” Pea Goat Giant alga fungus Time scale: 0.5 sec 5 sec 50 sec Duration of depolarization in plants is 2-100x longer than in animals and involves different ions, but is conceptually equivalent Do plants have action potentials? Membrane potential
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This note was uploaded on 04/07/2008 for the course MCDB 1B taught by Professor Weimbs during the Winter '08 term at UCSB.

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Lecture6 - Summary of path and driving force of water and...

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