Student Instructions            Notes for teachers

Read these instructions carefully before you start.

Begin by studying a Wild Oat seed with a hand lens. Record what you see. The long hair is called an awn. Then carry out steps 1-6 below.

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Notes for teachers

The Wild Oats awn (hair) is hygroscopic and moves rapidly (within a minute) in response to small changes in humidity. The Student Sheet shows one way of anchoring the seed and exposing it to different conditions so that movements of the awn can be observed and measured.

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Investigations

There are good opportunities here for investigations. Careful control of independent variables such as temperature as well as humidity will be needed, and there is great scope for identifying and measuring the dependent variable e.g. with a protractor and a stop watch. Once they have carried out steps 1 to 6, students could be encouraged to study the behaviour of the seeds when they are not anchored in blutack and to,try and relate this to the question of why the awn behaves as it does. Careful study of the seeds will reveal that the twisting and untwisting of the awn, combined with the spirally arranged, barb-like hairs at the other end of the seed provide a mechanism which will disperse the seeds and/or bury them in crevices.

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Organise a Wild Oat Derby!

See the article by Hou and Simpson for an ingenious way of extending the activity to include a Wild Oat seed race - a great idea for an Open Day at your School or College.

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How to get hold of the seeds of Wild Oats

The seeds of Wild Oats should be collected when they are ripe, which usually occurs just before the crops are harvested - in July or August in the UK. You are likely to find either the common Wild Oat, Avena fatua, or the Winter Wild Oat, Avena sterilis = A. ludoviciana. Use a specialist text, (Hubbard or Stace), if you want to find out which one you have.

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Important warning

Wild Oats are a serious pest on agricultural land. Please be careful not to discard the seeds when you have finished with them in case they find their way onto farm land e.g. via the waste disposal system. Store them in a suitably labelled jar or burn them.

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References

• Hubbard, C.E. (1984) Grasses (Penguin Books).
• Price, R. (1983) Beginning Biology: An introduction to biological science. Cambridge University Press.
• Hou, J.Q. and Simpson, G.M. (1992) The adaptive significance of awns and hairs in grasses. Journal of Biological Education, 26 (1) 10 - 11.
• Stace, C. (1991) New Flora of the British Isles. Cambridge University Press.

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Acknowledgements

Mike Kirby, formerly of the Plant Breeding Institute Cambridge, and Mike Ambrose of the John lnnes Centre, Norwich.