Science (086) — AI-generated practice question

When stomata close, CO₂ cannot enter the leaf. Without CO₂, photosynthesis slows down, so less carbohydrate is produced for the plant.

Stomatal closure also reduces transpiration. Since the transpiration pull is the main force driving the ascent of water through the xylem, reduced transpiration means less water is pulled up from the roots. Consequently, water movement through the xylem slows down.

Since minerals like nitrogen, phosphorus, and magnesium are dissolved in soil water and carried to the leaves along with this water through the xylem, a reduced water flow means fewer minerals reach the leaves. This further limits processes like protein synthesis that depend on these minerals.

Source: Chapter 5, Section 5.2.1

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• The examiner expects a chain/linked response — each consequence must flow from the previous one.
• Three distinct effects are needed for 3 marks: (1) reduced photosynthesis due to no CO₂, (2) reduced ascent of sap due to less transpiration pull, (3) reduced mineral supply due to slower xylem flow.
• Avoid writing in bullet points for a "explain" question — a short connected paragraph scores better.
• Key terms to use: transpiration pull, xylem, minerals dissolved in water — these are textbook terms examiners look for.