# Explain why a mineral ion deficiency in the soil can reduce the rate of photosynthesis in a plant.

> Pearson Edexcel International GCSE Biology (4BI1) — 2.5 Nutrition: flowering plants · Explain · 4 marks

> Plants absorb mineral ions from the soil through their roots. One essential mineral ion is magnesium, which is needed to make chlorophyll. Without sufficient magnesium, the leaves of a plant turn yellow.

## Mark scheme (4 marks)

1. Magnesium is needed to make chlorophyll
2. A deficiency of magnesium means less / no chlorophyll is produced
3. Less chlorophyll means less light energy is absorbed / captured
4. Therefore less / no photosynthesis can occur, reducing the rate

## Key terms

- [photosynthesis](https://www.gradenine.co.uk/glossary/photosynthesis)

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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