# A farmer grows two varieties of tomato plant in the same field. Variety A has broad, flat leaves and Variety B has narrow, upright leaves. The farmer notices that Variety A produces a greater mass of tomatoes per plant than Variety B when grown in full sunlight, but Variety B produces a similar mass to Variety A when grown in partial shade. Explain why Variety A produces a greater mass of tomatoes than Variety B in full sunlight, and suggest why the difference between the two varieties is much smaller in partial shade.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 3.1 Photosynthesis · Explain · 5 marks

> Photosynthesis is the process by which plants convert light energy, carbon dioxide and water into glucose and oxygen. The glucose produced can be used in respiration or converted into other organic molecules, including those used to build new cells and tissues. The rate of photosynthesis depends on the availability of raw materials and light energy.

## Mark scheme (5 marks)

1. Broad, flat leaves have a greater surface area (than narrow leaves)
2. Greater surface area allows more light energy to be absorbed / captured for photosynthesis
3. Higher rate of photosynthesis in Variety A (in full sunlight) so more glucose is produced
4. More glucose is available to be used for growth / building new cells / making organic molecules, leading to greater mass of tomatoes
5. In partial shade, light is the limiting factor for both varieties so the advantage of broad leaves is reduced / both varieties are limited by the same lack of light, not leaf shape

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-farmer-grows-two-varieties-of-c20b67d1) · Published by Druglandscape Ltd.