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Structure and function of the flower

By Roger Gonzalez,2014-11-26 12:34
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Structure and function of the flower

JSSS Teacher material

    Plant reproduction OB52-58

    Introduction

    This section of the syllabus is ideal for active learning. It lends itself to a wide scope and variety of investigation and experiment. Students encounter plant reproduction in their everyday life

    flowers, fruits and seeds are everywhere. Prior knowledge is usually well founded it is part of

    the Primary syllabus from Infants upwards - although misconceptions can be present. There are plenty of links to other parts of the syllabus.

    Prior knowledge

    A lot of students have more knowledge of plant reproduction that they realise who, for instance,

    has not used a dandelion as a ‘clock’ in their youth? Most students will have grown plants from

    seed in Primary school, and many will have observed reproduction of plants in the garden. Topics from the syllabus that students would need to have already studied are 1C1 Living things and 1C3 Plant structure, as well as OB51, distinuishing between asexual and sexual reproduction in plants.

    Misconceptions

    The term ‘flower’ is much misused and will need to be redefined here, as will the term ‘weed’.

    Many students would not consider grass to be a flowering plant. The difference between flowering and non-flowering plants will have to be explained. The connection between some everyday fruit, ‘vegetables’, and seeds may have to be pointed out.

    Teaching strategies

    It may be useful to plan ahead for teaching this topic, to ensure a variety of

    plants are in flower. Plants with large, visible, easily dissected flowers that

    bloom in spring and are usually fairly easily availably are tulips (but no sepals!) and daffodils. Comparison by observation, description and dissection of various flowers will serve the learning process, particularly for the visual and kinaesthetic learners. Investigating the life cycle by growing plants from seed is ideal. Larger seeds, e.g. butter beans and peas, are ideal for dissection to see the embryo, but can be slow to germinate. Smaller seeds,

    e.g. mustard, cress, alfalfa and

    quinoa grow rapidly once damp but

    can be difficult to see. A happy

    medium is the mung bean (the bean sprouts used in oriental cuisine!). It germinates without a medium, provided it is rinsed daily, and grows very quickly.

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JSSS Teacher material

    Common growing media are damp cotton wool, newspaper, or compost. Gelatine, a cheap alternative to agar, can be ideal as it is transparent, supplies water and can have nutrients added. Investigation

    This topic lends itself to a wide variety of investigation, with the simplest of material. A webcam or digital camera could be used to good effect recording the growth of germinating seeds over

    time. Some seeds grow very quickly even within a day, students cannot be there to watch but

    the camera can!

    One problem encountered at this level in studying germination is the exclusion of oxygen from germinating seeds under investigation. There are two techniques that work well covering the

    seeds with oil, or leaving no room at the top of a closed jar of gelatine.

    Seeds under oil Seeds on top of

    on left have no gelatine have almost

     access to O2no access to O2

Syllabus links

    There are many areas of the syllabus with which to link this topic.

    ; 1C1 Living things, particuarly OB40

    ; 1C3 Plant structure, particularly OB45

    ; 1C5 Photosynthesis, particulary OB50. The seeedlings grown in germination

    investigations can be used as the starting point for photo- and geotropism investigation.

    ; 1C7 Ecology, particularly OB60, living things respoding to changes in the

    environment, and OB62, adaptation

    ; 1B4 Human reproduction, particulary OB33 fertilisation

    ; 1A4 Aerobic respiration, particularly OB10 germinating seeds make excellent

    subjects for respiration investigation

    Did you know?

    ; Pure saffron, the red or yellow spice used in cooking, is made from the dried stamen of

    the crocus flower. It was once worth it weight in gold, and is still the most expensive

    spice in the world. See http://www.thefoodclub.org.uk/saffron.htm

    ; The world’s smallest flower is called Wolffia, a tiny duckweed less than 1mm in

    diameter. See http://waynesword.palomar.edu/plmar96.htm

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JSSS Teacher material

    th Century saw tha price of one tupil rise to over thirty ; Tulip mania in Europe in the 17

    times the annual wage of a skilled craftsman! See

    http://itsa.ucsf.edu/~snlrc/encyclopaedia_romana/aconite/tulipomania.html

    ; The worlds largest flower is Rafflesia, the three foot wide relative of the violet, growing

    in the rainforest of SE Asia. See

    http://dsc.discovery.com/news/briefs/20040112/flower.html

    ; The Dead-Horse Arum, a plant that grows in uninhabited areas of Sardinia and Corsica,

    smells and looks like a dead carcass. It attracts blowflies, and traps them inside for up to

    three days to ensure pollination. See

    http://www.pubs.royalsoc.ac.uk/bio_let_content/abstracts/hansson.html

    ; It has been reported that seeda of the arctic lupin that were found in a frozen lemming

    burrow along with animal remains in the Yukon were at least 10,000 years old.

    Amazingly, these seeds germinated within 48 hours. See

    http://www.devonian.ualberta.ca.getgro2.html

    Resources

    The following can be downloaded from www.juniorscience.ie or from the Round 5 CD.

    ; PowerPoint slides outlining flower structure and flowering cycle

    ; PowerPoint slides of Irish flowers from various habitats

    ; Web page with rollover images of flower structure

    ; Short movie on germinating peas

    ; Short movie on germinating beans on gelatine

    ; Students exercise on flower structure and function

    ; Students exercise on every day fruit

    ; Advice sheet on sprouting seeds

    ; Advice sheet on using gelatin as a growing medium

    ; List of plant reproduction topics covered in the primary syllabus

    ; A map showing links to other areas of the syllabus

    Links to useful websites are to be found on www.juniorscience.ie

    Local florists or supermarket will often have flowers past their sell by date, but still in good enough condition for class dissection

    The most cost effective source of seeds is the supermarket or local health food store.

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