Water Transport Mechanisms in Plants

Steps:

• Identify key processes: transpiration pull drives water up xylem via cohesion-tension; root pressure aids guttation but not primary ascent.
• Evaluate statement 1: Correct, as transpiration creates negative pressure pulling water upward.
• Evaluate statement 2: Correct, as cohesion between water molecules maintains continuous column in xylem.
• Evaluate statement 3: Incorrect, as water movement is mainly passive via xylem, not active transport against gravity in phloem.

Why B is correct:

• B selects statements 1 and 2, aligning with the cohesion-tension theory, which explains 99% of water ascent in tall plants via evaporation-driven pull.

Why the others are wrong:

• A includes 3, which misstates phloem's role in water transport.
• C pairs 1 with incorrect 3, omitting valid 2 on cohesion.
• D pairs 2 with incorrect 3, excluding transpiration's primary role.

Final answer: B