Movement of water from root to leaf (WJEC A-level Biology)

This lesson describes the movement of water from the root to the leaf and includes the transpiration stream and the cohesion-tension theory. The PowerPoint and accompanying resources have been designed to cover point (n) of topic 3 in AS unit 2 of the WJEC A-level Biology specification

This lesson has been written to follow on from a previous lesson, which finished with the description of the transport of the water and mineral ions from the endodermis to the xylem. Students are immediately challenged to use this knowledge to understand root pressure and the movement by mass flow down the pressure gradient. Moving forwards, time is taken to study the details of transpiration pull and the interaction between cohesion, tension and adhesion in capillary action is explained. Understanding is constantly checked through a range of tasks and prior knowledge checks are also written into the lesson to challenge the students to make links to previously covered topics such as the structure of the transport tissues. The final part of the lesson considers the journey of water through the leaf and ultimately out of the stomata in transpiration. A step by step guide using questions to discuss and answer as a class is used to support the students before the final task challenges them to summarise this movement out of the leaf.