Question

Trees and other plants move water and minerals from their roots upward into the tree through a process involving:
A. Cohesion only.
B. Adhesion only.
C. Surface tension only.
D. A combination of cohesion, adhesion, and surface tension called capillary action.

Answer 1

Option 'D' is the Correct Choice for Answer.

Explanation:

Water and minerals are able to rise high giant redwood because of cohesion tension and transpiration pull. This theory given by Dixon and Joly is known as transpiration pull theory. This is also known as ascent of sap theory.

This theory is based on two different aspects;

1. Cohesive force between water molecules and adhesive force between water and xylem;

2. Transpiration pull.

Cohesive force is force between molecules of same substance (here water molecules) and adhesive force is between molecules of different substances (here water and xylem). These forces play a crucial role in maintaining the continuity of water column from roots to leaves.

Transpiration from leaves creates a sort of suction force which pulls the water column from top resulting in ascent of water and minerals in tall tress. Thus pull is created from leaves and not from roots for lifting the water up. Earlier theories like root pressure theory failed as the force created from roots is not sufficient enough to move water in tall tress which are many metres high.

Thus in nutshell, water and minerals rise from root to shoot in giant redwood tree by cohesion-tension and transpiration pull. The name of this phenomenon is transpiration pull theory or ascent of sap theory.

The ability of water molecules to show cohesive and adhesive forces are the special properties that allow this to occur.

From the above discussion it is clear that, Minerals and water through the roots of a plant move by a combination of cohesion, adhesion and surface tension called Capillary Action.

Hence Option 'D' is the Correct Choice for Answer.