BIOL 1010 Lecture Notes - Lecture 68: Root Pressure, Transpiration, Stoma
14 May 2017
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Document Summary
As a plant grows upward toward sunlight, it needs to extract an increasing supply of water and dissolved mineral ions from the soil. Xylem tissue of angiosperms includes two types of conducting cells: tracheid s and vessel elements. Xylem sap, a solution of water and inorganic nutrients flows through the long, thin conduits formed by these dead cells from the roots to the tips of the leaves. The roots of the plants do exert a slight upward push on xylem sap. The root cells actively pump inorganic ions into the xylem, and the roots endodermis holds the ions there. Xylem, water tends to enter by osmosis, pushing xylem sap upward ahead of it. This force is called root pressure, can push xylem sap up a few meters. The pulling force is transpiration, which is loss of water from the leaves and other aerial parts of a plant by evaporation. Transpiration and its effect on water movement in a tree.
