Lesson Plan

• Describe how abscisic acid (ABA) initiates stomatal closure during water stress.
• Explain the function of calcium ions as a second messenger in the ABA signalling cascade.
• Identify key molecular components (PYR/PYL/RCAR, PP2C, SnRK2, SLAC1, GORK, NADPH oxidase) and their roles.
• Analyse how ion fluxes lead to loss of guard‑cell turgor and stomatal closure.
• Apply this knowledge to predict plant responses to drought conditions.

• Projector and screen
• PowerPoint slides with ABA pathway diagram
• Printed handouts of a blank signalling diagram
• Leaf samples for microscope observation (optional)
• Clicker/online quiz platform
• Whiteboard and markers

Begin with a striking image of a wilted plant to highlight the importance of water conservation. Ask students what they already know about stomata and how plants cope with drought. Explain that by the end of the lesson they will be able to describe the ABA‑driven signalling cascade and the specific role of calcium ions.

1. Do‑now (5') – Quick recall quiz on stomatal function and water potential.
2. Mini‑lecture (10') – Present ABA synthesis, perception, and the overall signalling pathway using slides.
3. Guided diagram activity (12') – In pairs, students label a blank ABA‑signalling diagram, emphasizing calcium influx.
4. Interactive simulation (8') – Use an online model to manipulate ABA levels and observe ion channel responses.
5. Think‑pair‑share (5') – Discuss how calcium‑dependent protein kinases amplify the signal.
6. Formative check (5') – Exit ticket: write one concise sentence describing calcium’s role as a second messenger.

Summarise the cascade from water stress to stomatal closure, highlighting the pivotal step where calcium acts as a second messenger. Collect the exit tickets to gauge understanding, and assign a short homework task: students create a one‑page infographic summarising the pathway.