BIOL 1010 Lecture Notes - Lecture 69: Transpiration, Guard Cell, Phloem
Document Summary
Transpiration exerts a pull on a tense, unbroken chain or water molecules that is held together by cohesion and helped upward by adhesion. Transpiration is an efficient means of moving large volumes of water upward from roots to shoots. In fact, via transpiration, xylem sap can move up a tree at speeds approaching. 80km/hr. no energy expenditure required to transport xylem sap by the plant. Physical properties cohesion, adhesion and evaporation, move water and dissolved minerals from a plants roots to its shoots. Describe the roles of cohesion and adhesion in the ascent of. Cohesion causes water molecules to stick together in a continuous string; adhesion helps xylem sap stick to the inside walls of the xylem cells. A plant must take a trade-off between its tremendous need for water and its need to make food by photosynthesis. As long as water moves up from the soil fast enough to replace the water that is lost, transpiration presents no problem.