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| Select item below | Osmosis 9 |
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ContentsAn
Introduction from the Director Dear Colleague, Modern science courses increasingly require students to plan and carry out their own investigations. We know only too well how demanding this is for teachers, so in this issue we offer a range of suggestions. On pages 2 and 3 we list some ideas for investigations with a number of different plants. On pages 4 and 5 we describe a method for studying the remarkable hygroscopic awn of wild oat seeds. Finally on page 8 we print a much shorter version of an excellent article on seed dispersel by animals which appeared in a recent issue of the Journal of Biological Education (JBE). If you are not already a member of the Institute of Biology we urge you to apply. Members get the JBE at a reduced rate and it really is an excellent source of ideas especially for secondary (pre and post-16) teachers - details from:
20 Queensberry Place, London, SW7 2DZ England Richard Price
Help us to help you We are always pleased to hear that students are choosing plant topics for their projects e.g. at A-level, GNVQ, CSYS, etc. However, we do find it hard to respond to letters from individual students. Firstly, students very rarely tell us what syllabus they are following so we do not know what constraints there may be e.g. time, etc. Secondly, we have no idea what facilities their school or college may have. Thirdly, we just do not have enough staff to respond helpfully to each and every student. Lastly and most importantly, we feel that it is a better use of everyone's time if we deal directly with those who teach the students rather than with the students themselves. Return to ContentsNEWSFLASH Special Grants for Special Needs. We are pleased to announce that one of the Sainsbury Family Trusts has generously agreed to continue to provide support for plant science work with Special Needs children. Grants are available (UK only) from SAPS. Please contact our Cambridge office for further details and an application form. Return to Contents "MERRY'S EARS" - a study of fruit and seed dispersal. By John Bebbington and Anne Bebbington. A short walk with Merry, a lively Springer Spaniel, provides an ideal opportunity to study the fruits dispersed by animals. If no dog is available an old blanket or sweater can be dragged through the undergrowth instead. Introductory work before the walk establishes that plants need to disperse their seeds and have several ways of doing this. (It may be that the whole fruit is dispersed or just the seeds themselves. Here the word fruit will be used throughout for simplicity.) The students are then asked to set up hypotheses about the characteristics of the fruits likely to be found on Merry, a furry mammal, and where they will be found, e.g:
Are your
plants close enough to the lights?
Return
to Contents Some ideas for projects with plants Stuck for ideas for your project? 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 project. The leaves of dandelions (Taraxacum officinale) sometimes lie flat and sometimes stand up. What
stimulus are the leaves responding to? 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? 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? 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? 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. hirsuta)? 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. 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 predation? 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? 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 plants. 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 aphids. 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? (This idea comes from Dr Matthew Sullivan of the Dept. of Biological Sciences at Manchester Metropolitan University.) Return to
Osmosis Index
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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.