Question

Capillarity theory was proposed by \rule{2cm{0.15mm}}

• A. Bohem
• B. J. Priestley
• C. Dixon and Joly
• D. Levitt

Hint:

Exam trap: Capillarity theory (Boehm) is NOT the correct explanation for ascent of sap. The correct and accepted theory is Cohesion–Tension Theory by Dixon & Joly.

Answer 1

The Correct Option is A

Concept: The ascent of sap (upward movement of water in plants) has been explained by several theories. One of the earliest explanations was the capillarity theory.
• Capillarity refers to the rise of liquid in narrow tubes due to surface tension and adhesion between liquid and tube walls.
• Xylem vessels in plants are narrow and can act like capillary tubes.
• This theory was proposed by Boehm (spelled as Bohem in options). However, capillarity alone cannot explain the movement of water to great heights in tall trees, so it is not the most accepted theory.

Step 1: Understand capillarity theory.
It states that water rises in plant xylem due to capillary action caused by adhesion and cohesion forces.

Step 2: Recall the scientist associated with this theory.
Capillarity theory was proposed by Boehm.

Step 3: Evaluate other options.
• (B) J. Priestley: Known for discovering the role of plants in restoring air (photosynthesis studies).
• (C) Dixon and Joly: Proposed the cohesion-tension theory, which is the widely accepted explanation.
• (D) Levitt: Known for work on plant physiology, especially stress physiology.

Step 4: Conclusion.
Thus, the correct answer is Boehm. Final Answer: Option (A)