BIOL 2080 Chapter Notes - Chapter 4: Symplast, Casparian Strip, Apoplast
1 Apr 2016
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Transpiration- cohesion theory as transpiration occurs in a leaf, it creates a cohesive pull on the whole water column downward to the roots, where water is absorbed from the soil. Transpiration the loss of water vapor from leaves that occurs thru the stomata (mainly) and thru the cuticle (somewhat) Transpiration diffusion of water from high concentration within leaf to lower concentration in atmosphere. When stomata is open, water vapor & oxygen diffuse out of the leaf while, co2 diffuses into leaf. When water loss excceds uptake guards cells lose turgor and close stomata. Pull of transpiration (in xylem) bulk flow. Pull of transpiration in leaf cohesive pull on whole water column downward from the leaf thru the xylem to the root: water uptake occurs in root to replace water lost during transpiration. Organic materials are translocated via sieve tube members of the phloem: sieve tube member = alive + highly specialized cells.
