This deep dive covers Stomata: The Control Valves within Transpiration for GCSE Biology. Transpiration process, stomatal control, factors affecting rate, plant adaptations, measuring transpiration, and practical investigations It is section 4 of 20 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 4 of 20
Practice
20 questions
Recall
25 flashcards
Stomata: The Control Valves
Structure and Function
Stomata (singular: stoma) are pores in the leaf epidermis controlled by pairs of guard cells. These kidney-shaped cells regulate gas exchange and water loss.
Opening Mechanism
Guard cells control stomatal opening through changes in turgor pressure:
- Light triggers: Blue light receptors activate potassium pumps
- Ion movement: K⁺ ions actively pumped into guard cells
- Water influx: Water follows by osmosis, increasing turgor
- Shape change: Guard cells become turgid and curved
- Pore opens: Inner walls pulled apart creating opening
Closing Mechanism
- K⁺ ions pumped out of guard cells
- Water follows by osmosis
- Guard cells become flaccid
- Pore closes as cells straighten
