Investigating Nettle Stings

Stinging nettles have developed stinging cells as an adaptation to deter herbivores from eating them. The plants contain long, thin, hollow hairs that cover the majority of the stem and the underside of the leaves. These hairs contain stinging chemicals.

Stinging hairs on a nettle leaf

Equipment

·         gloves

·         microscope

·         slides

·         plastic cover slips (small pieces of clear plastic such as acetate can be used if plastic cover slips are not available)

·         Universal Indicator solution

·         Universal Indicator paper

·         nettle leaves

·         dock leaves

Method

1.      Look at a piece of a nettle leaf under the microscope – you should be able to see the stings as hollow hairs containing a colourless liquid.

2.      Put a drop of Universal Indicator solution onto the piece of nettle leaf on the slide and lay another slide on top.

3.      Press the slides together to break open some of the stings. 

4.      You should see a pink colour developing around the spines after you press down on the top slide. What does this tell you about the liquid inside the spines?

5.      Take a fresh piece of nettle leaf and place it with the underside against a piece of damp Universal Indicator paper.

6.      Place a plastic cover slip on the leaf and press down to break some of the stings. 

7.      You should see yellow spots on the paper where stings broke open. What does this tell you about the liquid inside the stings?

A piece of damp universal indicator paper that has been pressed against a nettle leaf. Yellow spots show where acid has been released from the stings.

From these experiments we can see that the stings contain acid.