Question

Contact exchange theory was put forward by :

• A. Jenny and Overstreet
• B. Hylmo and Kramer
• C. Bennet and Clark
• D. De Vries and Curtis

Answer 1

The correct option is A Jenny and Overstreet

Contact exchange theory: This was put forward by Jenny and Overstreet. According to this theory, the ions adsorbed on the surface of root cells and clay particles (or clay micelles) are not held tightly but oscillate within a small volume of space. If the roots and clay particles are in close contact with each other, the oscillation volume of ions adsorbed on root-surface may overlap the oscillation volume of ions adsorbed on clay particles, and the ions adsorbed on clay particle may be exchanged with the ions adsorbed on root-surface di­rectly without first being dissolved in soil solution.

So, the correct option is A.