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lecture13 - Transpiration is regulated by opening and...

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5/10/09 1 Water in Plants Water, Diffusion, and Osmosis Water Movement in the Xylem Cohesion Tension Theory Sugar Movement in the Phloem Reading: Botany for Gardeners Pages 152-158 Polar molecule Sticks to other molecules - adhesion Cohesion - water sticks to itself Water is a Strange Molecule Osmosis - diffusion of water through a differentially permeable membrane Diffusion is driven by a concentration gradient Diffusion: high concentration to low concentration Diffusion is driven by random movement of molecules. Turgor Pressure Turgor pressure - pressure that is exerted against the cell wall as a result of water entering the cell Transpiration Water loss in leaves occurs by diffusion. Transpiration - the diffusion of water vapor from a leaf to the air
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5/10/09 2 Turgor pressure of guard cells controls stomatal opening
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Unformatted text preview: Transpiration is regulated by opening and closing of stomata The Cohesion-Tension Theory Transpiration and the cohesion of water causes an upward flow of water from soil to roots to leaves The adhesion of water to walls of xylem cells also helps resist gravity Cohesion, Tension, and Adhesion in the Ascent of Water 90 % of dry matter in phloem is sugar (mainly sucrose) Aphid Stylet Aphid Sugars are transported in the phloem Root Pressure- the pressure that develops, due to osmosis, in living cells of a root, forcing water up the xylem Guttation- droplets of water that form on leaf margins in a humid environment as a result of water being pushed up the xylem by root pressure Imbibition- the process of water absorption by a dry substance or structure, causing it to swell...
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This note was uploaded on 02/07/2011 for the course BIO 114 taught by Professor Ritter during the Spring '09 term at Cal Poly.

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lecture13 - Transpiration is regulated by opening and...

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