Lesson Plan

• Describe the structure of a stomatal complex and its function in gas exchange.
• Explain the osmotic mechanism that drives stomatal opening and closing.
• Analyze the typical circadian pattern of stomatal aperture throughout a 24‑hour period.
• Evaluate how light, temperature, humidity and water status modify the stomatal rhythm.
• Interpret stomatal conductance data to infer plant water‑use efficiency.

• Projector and slide deck
• Handout with stomatal diagram and data table
• Microscopes and prepared leaf slides
• Portable porometer (or video demonstration)
• Graph paper / digital spreadsheet for plotting
• Kahoot or similar quiz platform

Show a short sunrise video and ask students how plants “know” when to open their pores. Recall previous learning about guard cells and the role of stomata in photosynthesis. State that today’s success criteria are to describe the daily rhythm of stomata and predict how environmental cues alter it.

1. Do‑now (5'): Label parts of a stomatal complex on the worksheet.
2. Mini‑lecture (10'): Explain osmotic mechanisms and present the typical 24 h stomatal pattern using slides.
3. Interactive simulation (10'): Students manipulate light, temperature and humidity in an online model and observe predicted gₛ changes.
4. Data analysis activity (15'): Provide sample porometer data; students plot gₛ vs. time and identify opening/closing phases.
5. Think‑pair‑share (5'): Discuss how drought or ABA would shift the rhythm.
6. Formative check (5'): Quick Kahoot quiz on key concepts.

Summarise how the circadian rhythm balances CO₂ uptake with water loss and how external cues can override it. Have students write one‑sentence exit tickets predicting stomatal behaviour under a new condition. Assign homework: read a case study on drought‑induced stomatal closure and prepare a brief reflection.