Question

Which one of the following is NOT an objection against capillarity theory of ascent of sap in plants?

• A. Xylem tracheids compared to capillary tube show closed end walls.
• B. The xylem is not in direct contact with soil water.
• C. Because of capillarity, water can be raised to tall trees.
• D. Tall trees have wider xylem vessels which do not support capillarity.

Hint:

Capillarity can lift water only a short height, so a statement saying it lifts water to tall trees is a claim, not an objection.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
The capillarity theory says water rises in xylem like in a thin tube. Objections are the facts that make this unlikely.

Step 2: Real objections
Tracheids are closed at their ends, unlike an open capillary tube.
Xylem is separated from soil water by the root cortex and endodermis.
Wide vessels in tall trees would give very little capillary rise.

Step 3: Find the odd statement
Capillarity can lift water only a short height. The statement that it raises water to tall trees is false and favours the theory, so it is not an objection.

Final Answer:
Capillarity raising water to tall trees is the statement that is not an objection. \[ \boxed{\text{(C) }\text{Because of capillarity, water can be raised to tall trees.}} \]