Water & ions in plants (Edexcel Int.)

This lesson describes the importance of water and inorganic ions in plants. The PowerPoint and accompanying resources have been designed to cover the content of point 4.8 of the Edexcel International A-level biology specification, and includes details of the roles of nitrate, calcium and magnesium ions.

In an earlier lesson, the students explored the relationship between the structure and function of the xylem vessel, so this lesson describes how the properties of water allow movement through the tissue. The students will understand how hydrogen bonds between water molecules leads to cohesion and this coupled with tension, causes the column of water to be pulled towards the leaves by the transpiration pull. Their knowledge and understanding of the role of water in hydrolysis and condensation reactions is challenged, before the role of water as a transport medium for multiple substances, including inorganic ions, is discussed.

The rest of the lesson describes the role of magnesium in the production of chlorophyll, nitrates to make DNA and amino acids and calcium ions to form calcium pectate in the middle lamellae. There are multiple understanding checks and also prior knowledge checks, where the students recall of the structure and function of the vacuole and haemoglobin are challenged.