Preventing Air Entry in Xylem for Accurate Transpiration Measurement

Steps:

• Recall potometer measures water uptake via transpiration; air bubbles in xylem disrupt this.
• Cutting stem under water prevents air from entering exposed vessels, avoiding blockages.
• Connecting to potometer under water seals the system without introducing air.
• Evaluate statements: only one (3) correctly identifies air prevention as key.

Why D is correct:

• Statement 3 aligns with xylem function—air embolisms block cohesion-tension, halting flow (per transpiration theory).

Why the others are wrong:

• A includes incorrect statements 1 and 2, overgeneralizing procedure.
• B pairs 2 (likely irrelevant, e.g., hygiene) with 3, adding inaccuracy.
• C isolates 1 (possibly about plant stress, not air), missing core reason.

Final answer: D