Practical: The Xylem (SQA National 5 Biology): Revision Note

Demonstrating water movement in the xylem

• Water moves through a plant in a continuous system of xylem vessels

• It is possible to show the pathway taken by water through the xylem using a coloured dye

  • As the dye travels upward, it stains the xylem vessels, allowing their position within the stem to be seen clearly when a cross-section is cut

Apparatus

• Fresh celery stalk (or other suitable plant stem)

• Beaker

• Water

• Coloured dye or stain, e.g. food colouring or eosin solution

• Scalpel or sharp knife

• Cutting tile

• Microscope or hand lens

• Paper towel

Method

1. Pour water into a beaker and add a few drops of coloured dye or stain, mixing gently

2. Cut the end of the celery stalk at an angle to ensure a large surface area for liquid uptake

3. Place the cut end of the celery stalk into the beaker containing the dyed water

4. Leave the celery in the beaker until the leaves or veins show signs of the dye’s colour

5. Remove the celery from the beaker and gently blot off any excess liquid

6. Using a knife or scalpel, cut a thin cross-section from the dyed part of the stem on a cutting tile

7. Place the section on a microscope slide or observe directly using a hand lens

8. Identify the position of the coloured dye within the section; this shows where the xylem vessels are located