Stomatal Closure Reduces Transpiration in Peak Light

Steps:

• Transpiration rate peaks when stomata are open, allowing water vapor escape.
• Graph likely shows time on x-axis (daylight hours) and rate on y-axis, with midday as brightest.
• Plant X maintains high midday rate, indicating open stomata.
• Plant Y shows midday rate drop, signaling stomatal closure.

Why B is correct:

• Stomata close in bright light to conserve water (per plant physiology: abscisic acid triggers closure under high evaporation stress).

Why the others are wrong:

• A: Plant X's steady high rate shows open stomata midday.
• C: Only Plant Y dips; Plant X does not.
• D: Plant Y transpires earlier, proving stomata presence.

Final answer: B