A student places a healthy oak tree seedling in a dark cupboard for several days. When the seedling is returned to a sunny windowsill, new leaf growth resumes. Explain why the seedling was unable to produce new growth whilst in the dark cupboard, referring to the role of photosynthesis in the plant.

Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose from CO₂ and H₂O in the chloroplasts.

1. Light energy is required to drive the light‑dependent reactions.
2. In the dark cupboard the seedling receives no light, so the light reactions cannot occur.
3. Without the light reactions, the plant cannot produce ATP and NADPH, and the Calvin cycle cannot fix CO₂ into glucose.
4. Glucose is the main source of energy and carbon skeletons for cell division and leaf expansion.
5. When the seedling is moved to sunlight, light energy again powers photosynthesis, glucose is synthesised, and growth can resume.

Examiner_tips:
- Mention light energy, chloroplasts, CO₂, H₂O, glucose, and growth.
- Show the causal link: light → photosynthesis → glucose → growth.
- Keep the answer concise and use the exact terminology.

common_mistakes:
- Forgetting that photosynthesis is light‑dependent.
- Saying the plant simply “needs light” without linking to glucose production.
- Mixing up the roles of chlorophyll and chloroplasts.