Stomata - GCSE Biology Definition

Stomata are tiny pores found mainly on the underside of plant leaves. They are surrounded by guard cells, which control when the stomata open and close. Stomata allow carbon dioxide to enter the leaf for photosynthesis and let oxygen and water vapour leave. This helps the plant make food and also controls water loss through a process called transpiration. By opening and closing, stomata help the plant balance gas exchange and water retention, especially in hot or dry conditions.