Science — AI-generated practice question

When the plant does not need carbon dioxide (i.e., photosynthesis is not occurring), keeping stomata open would cause unnecessary water loss through transpiration. Therefore, the plant closes the stomatal pores to conserve water. This closing happens when the guard cells lose water and shrink, causing the pore to close.

Source: Chapter 5, Section 5.2.1 — Autotrophic Nutrition

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• The examiner expects two linked points: (1) open stomata cause water loss, and (2) the mechanism — guard cells shrink → pore closes.
• Do not just say "to prevent water loss" without mentioning the guard cell mechanism; the second mark is for the mechanism.
• The key phrase from the textbook is: "the plant closes these pores when it does not need carbon dioxide for photosynthesis" and "the pore closes if the guard cells shrink."