Explain why germinating seeds produce large amounts of carbon dioxide in the first few days after germination, even before the seedling leaves emerge above the soil.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Germinating seeds respire rapidly as they begin to grow. During the first few days, the seedling is entirely underground and receives no light.
Model answer (4 marks)
Germinating seeds carry out aerobic respiration, which uses glucose and oxygen to release energy.
The reaction produces carbon dioxide as a waste product.
During the first few days the seedling is underground and has no photosynthesis, so it relies entirely on stored reserves.
Large amounts of energy are required for rapid cell division and growth, so the rate of respiration – and therefore CO₂ production – is high.
The reaction produces carbon dioxide as a waste product.
During the first few days the seedling is underground and has no photosynthesis, so it relies entirely on stored reserves.
Large amounts of energy are required for rapid cell division and growth, so the rate of respiration – and therefore CO₂ production – is high.
Examiner tips
- Use the term "aerobic respiration" and mention glucose and oxygen. State that CO₂ is a product of this process. Explain that the seed needs energy for rapid growth. Keep the answer short and to the point.
Common mistakes
- Confusing anaerobic respiration with aerobic. Forgetting to mention that the seed is underground and cannot photosynthesize. Over‑expanding the answer with irrelevant details.
Mark scheme (4 marks)
- Germinating seeds carry out aerobic respiration
- Aerobic respiration uses glucose (and oxygen) to release energy
- Carbon dioxide is a product of aerobic respiration
- Large amounts of energy are needed for rapid cell division / growth of the seedling, so the rate of respiration is high
Key terms in this question
Related
- All Pearson Edexcel International GCSE Biology (4BI1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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