Sclerenchyma, xylem and phloem (Edexcel Int. A-level Biology)

This lesson describes the similarities and differences between the structure, position and function of the xylem, phloem and the sclerenchyma fibres. The engaging and detailed PowerPoint and accompanying resources have been designed to cover point 4.5 in unit 2 of the Edexcel International A-level Biology specification.

The lessons begins by challenging the students to identify the substances that a plant needs for the cellular reactions, where they are absorbed and where these reactions occur in a plant. The aim of this task is to get the students to recognise that water and mineral ions are absorbed in the roots and needed in the leaves whilst the products of photosynthesis are in the leaves and need to be used all over the plant. Students will be reminded that the xylem and phloem are part of the vascular system responsible for transporting these substances and then the rest of the lesson focuses on linking structure to function. A range of tasks which include discussion points, exam-style questions and quick quiz rounds are used to describe how lignification results in the xylem as a hollow tube of xylem cells to allow water to move as a complete column. They will also learn that the narrow diameter of this vessel allows capillary action to move water molecules up the sides of the vessel. The same process is used to enable students to understand how the structures of the companion cells allows assimilates to be loaded before being moved to the sieve tube elements through the plasmodesmata.

The final part of the lesson introduces the sclerenchyma tissue as part of the vascular bundle and along with the structure and function, the students will observe where this tissue is found in the stem in comparison to the xylem and phloem.

It is estimated that it will take in excess of 2 hours of A-level teaching time to cover the detail which has been written into this lesson