Science and Plants for Schools – Student Project Starter
Inhibitory growth effects of conifers
This is a project starter, suitable for Advanced Higher biology investigations or A-level extended
projects. Don’t forget to credit this resource in your bibliography by including the title, the website,
the web address and the date you accessed it.
Background information
It is well known that conifer trees, such as pine trees, contain compounds which
inhibit the growth of other plants. Conifer trees tend to have few other species of
plants growing under them and experiments can be done which show that pine
needles have an inhibitory effect on the germination of seeds such as cress. It has
also been reported recently that extracts from the immature cones of a species of
conifer tree (Lawson’s Cypress) contain anti-bacterial agents which may be
effective against MRSA. An extract from the bark of another conifer (a Yew tree) is
used in the treatment of cancer as it has an inhibitory effect on cancer cell growth.
In investigations on this topic the inhibitory effects of conifer extracts on plant and
microbial growth can be investigated.
Starter experiment
Instructions
Preparing the conifer extract – e.g. pine/cypress/spruce/yew
Take 2.5g of needles or cones and grind in a mortal and pestle with 30cm3
 of sterile distilled water
 Filter the extract through muslin and pour into a clean labelled bottle
Seedling growth
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Pre-label petri-dishes with each conifer extract to be used (do replicates of
each extract)
Place filter paper into petri-dish base and moisten with 1ml of sterile water
Weigh out 0.3g of cress seeds and scatter evenly onto pre-labelled petridishes
Water each dish with 2cm3 of conifer extract or sterile water (control)
Place under light bank
Water daily with 1cm3 of extract or sterile water
Each day record % germination of seeds and from day 2 onwards measure
average root and shoot length
Plot results showing % inhibition of germination, root and shoot growth
Possible investigations
Plant growth inhibition
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Compare the inhibitory effects on plant growth of extracts from cones or
needles
 Collect conifer needles from the woodland floor and compare the inhibitory
effects on plant growth of old needle extract against new needle extract
 Compare the inhibitory effects on plant growth of extracts from old and
immature cones
 Compare growth inhibition using different plant seeds e.g. plants commonly
found on woodland floors
Microbial inhibition
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Investigate the inhibitory effects of the conifer extracts on microbial growth
e.g. compare extracts from different conifer species or from new and old
cones/needles (prepare agar plates suitable for growing lawns of bacteria,
yeast or algae- place, different plant extracts in wells on the plates and
measure any zone of inhibition)
The methods for this activity can be found in the project starter – ‘Antimicrobials’
( http://www.saps.org.uk/students/projects/148-investigating-antimicrobials ) and
further information about the algae and culture medium can be found on the SAPS
web-site in our algal balls resource (http://www.saps.org.uk/secondary/teachingresources/235)
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Investigate the effect of an extract on different microbes