Allelopathy is the influence or effects of a living plant on nearby plants or microorganisms. These effects are generally caused by secondary metabolites.
In this experiment a bioassay was carried out to examine the effect of plant extracts on seedling growth. A bioassay is the determination of the biological activity of a substance using a living organism. Lettuce seeds were used in this experiment.
Equipment needed- Plant materials Lemon,Chilli and Daffodil (in my case).
- 4 Petri dishes.
- Parafilm.
- Mortar and pestle.
- 15ml screw capped tubes
- Lettuce seeds (Lactuca sativa).
Lettuce seeds
<---- Now that the main introduction is out of the way I can go on to tell you the method that I used and results obtained from doing this experiment. A selection of plant tissue was laid out on the front bench in our Botany lab and I picked 3 different types. I picked lemon, daffodil and chilli, then proceeded to weigh out 2g of each tissue and grinded them up in a mortar and pestle. The daffodil was no problem to grind up but the chilli and lemon took a bit more elbow grease. When I felt I had ground each tissue up enough I placed them into a labelled 15ml tube and added about 10ml of warm water (roughly 37°). I then mixed the tubes very well and left to stand for ten minutes they were then handed over to our lecturer and centrifuged. I then went and got my petri dishes which I had individually labelled with the plant names and also one just as a control. Then I placed a piece of filter paper in the base of the petri dish, I then wet the control filter paper disc with distilled water and the other three dishes with the plant extracts matching each dish. The next part was quite tedious where 40 lettuce seeds had to be carefully counted out and placed on to each dish. Each petri dish was then wrapped with parafilm to prevent them drying out and getting infected they were then placed in an incubator.
Hey Presto
Picture 1: This picture shows the control, as you can see the lettuce seeds are premoting good growth because distilled water has been used on them and they have been incubated at the right temperature practically 90% of the seeds have germinated.
Picture 2: This picture shows the growth of the lettuce seeds using the plant extract chilli, very little growth has been observed here, a red stain can be seen on the filter paper. Hypocotyls appear to have grown on average.1cm a tiny bit of mould was observed in one patch and overall a 5% germination rate.
Picture 3: This picture goes on to show the growth of the lettuce seeds using daffodil plant extract, all of the roots look like they have been burnt off because a minature black dot has appeared on the ends of the hypocotyls, my conclusion is that a chemical is contained in the daffodil that prevents root growth. Also another conclusion I made was that whatever part of the daffodil used may effect the end result because other people that used the daffodil had better growth rates.10% germination rate.
Picture 4: This final picture now shows the lemon extract used on the lettuce seeds, as you can see the dish is over grown in a mould, this lemon seems to have a penicillin inhibitor on the exterior of the lemons skin. Skin and flesh was used in this so the sugars contained in the lemon acted as a activator for growth but the penicillen would have acted as a inhibitor. 90% germination seems to be present the shoots seem narrow and more spindally compared to the control.
