SAPS Student Project - plant investigations

Science and Plants for Schools – Student Project Starters
Some ideas for extended projects with plants
Stuck for ideas for your extended project or investigation? Interested in
plants? Here are some ideas. But a good starting point is to have a close look
at some plants, e.g. the 'weeds', which grow around your house or in the
school grounds. Many of these have amazing survival strategies - which is
why they are such successful weeds. Alternatively, sow some seeds and
watch them grow. Make a note of any interesting observations. Then get into
the habit of asking yourself some simple questions about your observations. It
is quite likely that, sooner or later, one of your questions will turn into a good
The leaves of dandelions (Taraxacum officinale) sometimes lie flat and
sometimes stand up.
What stimulus are the leaves responding to?
Where is it detected?
The vase life of some cut flowers seems to be affected by the presence
of other flowers in the same vase, e.g. Forget-me-nots (Myosotis sp) wilt
rapidly when they are put in the same vase as Narcissi (Narcissus sp).
Try to devise your own questions relating to this observation.
Seedlings respond to unidirectional light by bending towards the light
source (positive phototropism).
What wavelength or wavelengths are they responding to?
Does the part of the seedling which responds also detect the unidirectional
Record the number and type of insects visiting different coloured
flowers on sunny days.
When the petals are separated from the nectaries are the same insects still
attracted to the petals?
Is it the colour of the flowers which is significant in attracting insects. What
else could it be? Devise simple investigations to find out more.
The flowers of daisies (Bellis perennis) are sometimes open and
sometimes closed.
What is it that stimulates the flowers to open and close?
Where is the stimulus detected, e.g. in the flowers themselves or elsewhere?
An investigation from Science and Plants for Schools,
Do the flowers of other plants behave in the same way? Are they responding
to the same stimulus?
Can the open flowers of laboratory grown plants, e.g. rapid-cycling brassicas,
be made to close? (or inhibited from opening?)
Many small crucifer weeds are widespread and easy to culture in the lab.
e.g. Shepherd's Purse (Capsella bursa-pastoris), Hairy Bittercress
(Cardamine hirsuta) and Thale Cress (Arabidopsis thaliana). Drill a single hole
about 5 mm in diameter in the bottom of a black film can. Insert a short wick of
any suitable absorbent material. Transplant crucifer seedlings, one to a film
can. Grow them in soil or compost. Place the film cans on capillary matting on
a water reservoir made out of a margarine or ice cream carton. Follow the
development of the plants through flowering to seed set. Growth may be more
rapid under a light bank. A number of questions will arise, e.g:
What factors influence flowering, pollination mechanisms, tropic response of
the flowering shoot, seed maturation, seed dispersal (especially in C.
Grow some seedlings in bright light, shade and darkness. You will see some
distinct differences which will raise questions which you can pursue. Suitable
seedlings: Garden Pea (Pisum sativum), White Mustard (Sinapis alba), Salad
Cress (Lepidium sativum), French Bean (Phaseolus vulgaris), etc.
Plants in the genus Euphorbia (the spurges) contain a white latex which
is toxic and said to offer them protection from predation e.g. by
herbivorous insects. Petty Spurge (Euphorbia peplus) is a common weed on
cultivated ground.
safety SAFETY NOTE: Euphorbia latex is toxic can cause skin burns and
irritation. Take care to keep it off your skin and particular care to avoid getting
it in your eyes.
Find a Euphorbia and look for evidence of predation. If you find it, try to find
out what animal is causing the damage.
Smear Euphorbia latex onto other plants. Does it protect them from
Learn a suitable technique for examining the stomata on leaf surfaces
(e.g. nail varnish impressions). Grow seedlings (e.g. in film cans) under
controlled conditions.
Is the size and/or distribution of stomata influenced by the conditions under
which the seedlings are grown?
What factors influence the behaviour of stomata?
An investigation from Science and Plants for Schools,
Weeds compete with each other and with our crops and garden plants.
What sort of things do plants compete for when growing close together?
Make sure that you understand what the words bioassay and allelopathy
mean. Use small seed such as Garden Cress (Lepidium sativum) as a
bioassay to investigate the production of allelopathic compounds by other
Why don't seeds germinate inside ripe fruits such as tomatoes, apples,
oranges, etc?
Use small inexpensive seed, e.g. Garden Cress (Lepidium sativum), as a
bioassay to examine extracts from the tissues which surround the seeds in
various ripe fruits. (Reference: Gill, J. (1982) 'A study of germination inhibition
in fruits', Journal of Biological Education, 16 (3) pp 162 -163).
Study the way in which plants and animals are dependent on each other.
For example, adult hoverflies feed on nectar and pollen. Their larvae feed on
Do adult hoverflies lay their eggs on the same plants from which they
get pollen and nectar?
What is it that attracts the adult hoverflies to a flower?
Can a fly trap count? Does it have a memory?
Strange questions to ask about a plant? Examine 10 open fly traps. Do not
touch them! Look for the trigger hairs. How many are there on each side of
the trap? Is there the same number of trigger hairs in all 10 traps?
One of the most interesting questions about the fly trap is this. How does the
trap know when to close and when not to close? For example, it will not close
when a raindrop or a piece of debris falls on a trigger hair but it will when an
insect does. It seems as if the trigger hairs must be touched more than once.
Use a very fine pin or needle and a stop watch to investigate this interesting
problem. Here are some suggestions:
# Touch 1 hair once and note the response.
# Touch 1 hair twice in quick succession (e.g. 1 second)
# Touch 1 hair twice with a longer interval (e.g. 1 minute)
# Touch 1 hair once and then another hair on the same side once. And so on.
Fly trap digestion
Sometimes a fly trap will close on something which is not suitable 'food' e.g. a
soil particle. If this happens it will open again without trying to digest it. How
does it know what to digest?
An investigation from Science and Plants for Schools,
You can investigate this by placing small quantities of different substances in
closed traps and seeing if they open.
What sort of substances are likely to be effective? Remember that fly traps
grow in soils deficient in one particular mineral.
An investigation from Science and Plants for Schools,