Translocation of Water

Estimated time: 3 minutes

Maharashtra State Board: Class 12

Key Points: Translocation of Water

Meaning: Translocation of water is the upward movement of water with dissolved minerals from roots to aerial parts like the stem and leaves against gravity.
Pathway: Water moves through xylem tissues, mainly tracheids and vessels, as proved by the ringing experiment.
Root Pressure Theory: Proposed by J. Priestley, it states that water is pushed upward due to root pressure generated by living root cells (about +1 to +2 bars).
Capillarity Theory: Given by Boehm, it explains the ascent of sap due to capillary action caused by cohesion, adhesion, and surface tension, but it can lift water only a few centimetres.
Cohesion-Tension Theory: Proposed by Dixon and Jolly, it states that water rises due to transpiration pull along with cohesion (between water molecules) and adhesion (with xylem walls).
Most Accepted Theory: The cohesion-tension (transpiration pull) theory is the most widely accepted explanation for the ascent of sap in plants.