Ch35_Lecture-Spr11

Ch35_Lecture-Spr11 - Transport in Plants 35 Transport in...

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Transport in Plants
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35 Transport in Plants • 35.1 How Do Plants Take Up Water and Solutes? • 35.2 How Are Water and Minerals Transported in the Xylem? • 35.3 How Do Stomata Control the Loss of Water and the Uptake of CO 2 ? • 35.4 How Are Substances Translocated in the Phloem? www.biologie.uni-hamburg.de/b-online/fo06 Scanning EM of pumpkin xylem
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35.1 How Do Plant Cells Take Up Water and Solutes? Terrestrial plants obtain water and mineral nutrients from soil Water needed for… photosynthesis essential for transporting solutes up and down cooling plant internal pressure to support plant Plants lose large quantities of water to evaporation, which must be replaced www.eurekalert.org/features/kids/images
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Plants usually obtain water & minerals from soil via roots Water uptake requires water to enter through cell membranes via osmosis Mineral uptake requires transport proteins Roots obtain carbohydrates and other materials from leaves. 35.1 How Do Plant Cells Take Up Water and Solutes?
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35.1 How Do Plant Cells Take Up Water and Solutes? Osmosis movement of water through a membrane in accordance with laws of diffusion Osmosis is passive : no input of energy is required
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35.1 How Do Plant Cells Take Up Water and Solutes? Solute potential (aka. osmotic potential ) Determines direction of water movement across membrane The greater the solute concentration of a solution, the more negative the solute potential , and… the greater the tendency for water to move into it from another solution of lower solute concentration i.e. water moves from low solute concentration to higher solute conc.
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Osmosis Modifies the Shapes of Cells
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35.1 How Do Plant Cells Take Up Water and Solutes? For osmosis to occur, two solutions must be separated by selectively permeable membrane permeable to water, but not to solute
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35.1 How Do Plant Cells Take Up Water and Solutes? Plants have rigid cell walls As water enters cell due to its negative solute potential,… entry of more water is resisted by an opposing pressure potential ( turgor pressure ). www.botany.hawaii.edu/faculty/webb/BOT311/BOT311-00/Water
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35.1 How Do Plant Cells Take Up Water and Solutes? Water enters plant cells until pressure potential exactly balances solute potential At this point the cell is turgid – It has significant positive pressure potential (but balanced by turgor pressure) www.botany.hawaii.edu/faculty/webb/BOT311/BOT311-00/Water
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35.1 How Do Plant Cells Take Up Water and Solutes? Water potential ( ψ ) overall tendency of solution to take up water from pure water across a membrane Water potential = sum of its negative solute potential ( ψ s ) + positive pressure potential ( ψ p ) ψ = ψ s + ψ p
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Figure 35.2 Water Potential, Solute Potential, and Pressure Potential Re: ψ = ψ s + ψ p (see Fig. 36.2) Salt solution inside tube has negative ψ thus its not at equilibrium with pure water outside membrane
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This note was uploaded on 06/06/2011 for the course BSC 2011 taught by Professor Presley during the Spring '11 term at FAU.

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Ch35_Lecture-Spr11 - Transport in Plants 35 Transport in...

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