Home   eXtreme botany   Fascination with smelly plants!

Fascination with smelly plants!

Fascination of Plants Day is an International celebration of plants, it is a whole series of events all about plants which happens every second year.  The aim is to get as many people as possible around the world fascinated by plants and enthused about the importance of plant science for agriculture, horticulture, forestry and the production of plant-based non-food products such as paper, timber, chemicals, energy and pharmaceuticals. The role of plants in environmental and biodiversity conservation is also a key message.

Fascination of Plants day is always 18th May but in 2019 this falls on a Saturday and so, at the University of Reading, we are celebrating on Wednesday 15th May as this is easier for the schools that we want to invite.   So we have invited local schools* to visit the Biological Sciences laboratories and the beautiful Harris Garden all at the University of Reading to join us in investigating the question: “Why are plants smelly?!”

There will be three activities lead by Mr Alex, Dr M and Mr Oli and we will be asking the following questions:

  1. Which plant families are smelly?
  2. Why do some plants smell nice & others gross & stinky?
  3. Can smelly plants kill germs?

The following gives a short description of each activity to get you thinking about the issues surrounding smelly plants.  There will be another post after FoPD with details of what we found out on the day.  We will also be making a short video on the subject and this will be published on YouTube in due course.

ACTIVITY #1: Let’s talk about smelly plant families!

Mr Alex is running this session in the biology laboratory and he says:

This activity gives you hands on experience with plants that emit a wide variety of smells, scents and aromas from their flowers, leaves, stems and roots. These smells have a variety of roles both for attracting pollinators, as well as preventing damage from insect herbivores or infection by fungi and microbes.

In this session participants will explore the plant scents that are found across a variety of plant families (e.g. mint, cabbage and carrot families) as well as the diversity within a single family.

To make sure participants can smell as many stinky plants as possible we will play the “smelly plant game” in which 30 squished, mushed, or otherwise broken and crushed plants will be placed in little smell pots. Participants sniff the contents without any clues as to what the original plant might be. The aim of the game is to identify the smell, think about why it might smell like that, and also what it might smell similar to.

The lucky winners are awarded their prizes and the session ends with some explanation about how the chemicals which make the plants smell are useful for both the plant, and to us for food, medicines, therapy and so on.

ACTIVITY #2: We’re all going on a smelly plant walk! 

Dr M is running this activity and he says:

This activity introduces you to smelly plants outside and starts with a walk from the laboratory to the University of Reading’s beautiful Harris Garden and on the way we will take a look and a sniff at some of the plants we see there.

We will find that some flowers are heavily and sweetly scented but others are more grossly stinky and we will ask why is this?!

We will also look at some other plants, e.g. conifers like Christmas trees, and participants will be encouraged to use hand lenses provided to examine the detail of these lovely plants.  We will then get busy snapping the stems and crushing the leaves to release the terpene-rich sticky resin which is a feature of conifers such as Christmas trees.  We will try to identify and characterise the smells – pine, resin, parsley, citrus.  We may not be able to agree on the particular smell of any one plant, and this reflects the individualistic feature of the human nose!  What smells sweet to one person may smell sour to another!

The session concludes by asking what the function of different plant smells might be. We will talk about “come and get me” smells which try to attract insects for pollination.  Equally we will discuss “naff off!” smells which might try to repel herbivorous insects which want to eat the plant. There are also other chemicals which might protect the plant from bacterial and fungal infections.

ACTIVITY 3: Can smelly plants kill germs?!  

Mr Oli is running this activity back in the biology laboratory and he says:

For this activity we want to introduce you to the idea that plants can kill germs, the scientific term for this process is “antimicrobial” which means “germ-killing” and there are special chemicals in some plants which can do this.

Microbes are tiny, microscopic living things like bacteria and fungi which are all around us. In fact, most of the cells in our body are bacteria!  Most of these bacteria don’t cause us any problems and many are incredibly helpful, but there are microbes that can cause make us sick.

Although you probably never realised this, it is exactly the same for plants! Just like our bodies plants try and fight off germs, to do this they produce anti-microbial (germ-killing) chemicals to protect themselves. In this activity, we’re going to investigate these chemicals, test them, and understand how they link to plants’ smells.

For this exercise we will be doing some experiments using agar plates and you will be crushing up some plants to make extracts using a mortar and pestle.  For your safety you will need to wear white lab coats, gloves and goggles just like a real scientist!  But don’t worry, all of this will be provided by the University of Reading for you to use on the day, you only need to bring yourselves and your brains switched on and ready to work!

Finally, Dr M who is coordinating this event says: If you are one of the schools booked and coming to Reading for this Fascination of Plants day you can prepare by discussing and trying to understand all the words in the descriptions above, the rest will happen in the activities next week, we look forward to meeting you!

*NB This event is now fully booked, any other schools wishing to attend botanical outreach events at University of Reading please email j.mitchley@reading.ac.uk

We are grateful to the British Ecological Society for helping fund this outreach project.