Question

Transpirational pull theory was given by

• A. Henry H. Dixon.
• B. John H. Jolly.
• C. J.C. Bose.
• D. Both A and B.

Answer 1

The correct option is D Both A and B.

Most acceptable theory for the ascent of sap is the 'Physical force theory', called as 'Cohesion-Transpiration pull theory'. This theory was put forward by Dixon and Joly. According to this theory, the ascent of sap in plants is a physical process, the lifting force for which is provided by the pulling force generated by transpiration. The cohesion forces between the water molecules help in maintaining a continuous water column and the adhesion forces between water molecules and the tracheary elements help in sticking to water to the xylary elements. Both of these forces help in maintaining a continuous water column in the xylary elements.

Thus, the correct answer is option D.