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9 (c) When the lights are on in the glasshouse, the stomata on the lettuce leaves open. This allows carbon dioxide to enter the leaves. Describe how stomata open. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [2] (d) Lettuce leaves contain xylem vessels. Describe the structure of xylem vessels. ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [2] [Total: 8]

Section B begins on page 10

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B4 question 3 (2)