IGCSE Biology glossary
Stomata
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
Small pores found mainly on the lower surface of leaves, each surrounded by a pair of guard cells that control opening and closing. When open, stomata allow carbon dioxide in and oxygen and water vapour out. The singular form is stoma.
What to include in an exam answer
Stomata open during the day (for photosynthesis) and close at night or during water stress. Know that guard cells become turgid to open stomata and flaccid to close them.
Example in context
Explain why stomata are mainly found on the lower epidermis of a leaf (2 marks): The lower surface receives less direct sunlight, which reduces water loss by evaporation from the stomata while still allowing gas exchange.
Related syllabus topic
Plant nutrition