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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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- Spring '09
- Plants, phloem, Xylem, Ascent of Water