Essential Oils Against Fungi
Pupils are introduced to the volatile substances in plants that act against mould. Pupils work in groups to test whether the use of essential oil (or another natural fungicide) will stop the growth of mould in a Petri dish.
Age Group: 9-12 years
Duration: Experiment set-up 20 minutes; observation and evaluation of the experiment 15 minutes.
Biomimicry Connection:
The antifungal properties of oregano inspired scientists from the nanotechnology company Nanomic to create an innovative product, capsules that containing natural fungicides that only work against fungi when the plant is attacked by a disease (accompanied by a drop in pH on the surface of the fruit).
Activity Details:
Tools and Materials
- Petri dishes
- Agar
- Source of mould (for example, a mouldy apple or bread)
- Essential oil or other substance containing thymol or carvacrol
- Worksheet - observation protocol
Preparations
- Pictures of herbs (wild thyme = Thymus serpyllum, oregano/thyme, eucalyptus, rosemary) and/or dried herbs
- Petri dishes with agar
- Establish a place where the petri dishes will be placed during the experiment and where it will be possible to observe the activity in the petri dishes
Description
- Start by asking pupils to identify the plants they will be working with from pictures (wild thyme, common thyme, eucalyptus, rosemary). Alternatively, they could smell dried herbs - identifying plants by smell - what makes the plants smell that way?
- Introduce the experiment, offering a hypothesis. For example, there will be less mould growth on petri dishes treated with natural fungicide than on petri dishes without the application of natural fungicide.Explain any key words pupils might be unfamiliar with (mould, fungicide, active substances from herbs - thymol, carvacrol).
- Divide pupils in to groups and each group is assigned two petri dishes with a prepared layer of cooled solidified agar and a source of mould (a mouldy apple, for example). Ask pupils to label their petri dishes so they can identify them later, and assign them the number 1 or 2.
- Ask groups to apply a small amount of mould on to the surface of the agar in both dishes using a clean spatula.
- Pupils then add 1 drop of essential oil containing thymol or carvacrol into one of the dishes.
- Pupils prepare to observe their experiment. Ask them to make a prediction as to what they think might happen. Then prepare a recording sheet to note down what happens each time they observe their experiment.
- Pupils observe and record what is happening in their trays every 2-3 days (e.g. in tray 1 a mould culture is observed - a dot about 2 mm in diameter).
- After 2 weeks, conclude the monitoring with a final assessment of the observations and evaluate the hypothesis; was it confirmed that the mould grew more slowly in the dish with the natural fungicide applied?
- Record the results of each group's observations on the board in a prepared table (see example below), and ask pupils to compare their results with those of the other groups and discuss the results of the experiment.
- Summarise the results of the groups and invite pupils to discuss where they have encountered the use of plants containing fungicidal active substances in their everyday life, or where and how such substances could be used in the protection against moulds.
- If relevant, present this video which shows how one company is developing capsules against fungal diseases that are 100% nature based, and plants do not become resistant after their use, compared to harmful synthetic pesticide.
