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| Select item below | Osmosis 15 |
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There is a 30cm ruler on the pot |
About this time of the year (Christmas-time), you can buy Amaryllis bulbs in the shops. All you have to do is water them each week and keep them warm (minimum 20oC). When the flower bud appears then you must water the soil about twice a week, and they will produce the most beautiful flowers.
When the flower stem starts to grow, measure its length every day and keep a record of the growth. Measure from the same place (for example put a ruler across the top of the pot) up to the tip. Once the flower has opened, move it to a cooler place because it will last longer there. |
You can draw a line graph of the length of the flower stem each day. What shape of graph did you find?
How many flowers did you get on your flower head?
How many petals were there in each flower?
How many stamens in each flower?
Look at the stigma on top of the ovary. How many lobes has it? How many lobes does the ovary have?
Take one flower and cut the ovary in half (across its short axis - sideways, not longways). How many chambers in the ovary?
Are there any seeds in the ovary? Scrape out the ovary carefully. How many seeds did you find?
Do the flowers show symmetry? If so, what sort of symmetry?
You only need use one flower to answer all these questions - you can leave the others to develop fully and enjoy them.
You could try removing the stamens from some flowers and not from others. Do the flowers without stamens last longer than those left intact?
Did you find that things go in 3s or 4s or 5s with this flower? Try looking at snowdrops and narcissus - they are in the same family of flowers. Now look for other characters that members of the family share - what about the shape of the leaves?
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After the flowers have died, cut the stalk to about 5cm above the bulb. The leaves may continue to grow and a second flower may appear. When the chance of frost has passed, bury the whole pot about 2.5 cm under the soil in your garden. Feed the plant regularly with liquid fertiliser and water it in dry periods. In early autumn, stop watering, dig up the pot and lie it on its side to dry off. The leaves will die off and the nutrients will pass back into the leaf bases to make a plump new bulb. Dry the bulb for 2 weeks at 18-24oC and then store for 10 weeks in a cool (about 14oC), dark and dry place in its pot. It is now ready for repotting and watering to wake it again. |
Dr Mary MacDonald, Dr John Hewitson and staff at Laxton Junior School, Oundle
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Osmosis No 14 gave a list of ideas for investigations with mosses.
1) Many gardeners find it hard to kill moss in their lawns. Why is this? Perhaps mosses are not as sensitive to some weedkillers as are other 'weeds'. How could you investigate this in the laboratory?
Safety check - Always:
• take care when handling weedkillers (herbicides) and be sure to follow the manufacturers instructions and heed their warnings
• dispose of the solutions carefully after use. They can be put down the sink, but with plenty of water.
(In the next section, you need to make sure you understand the technical terms which are in bold.)
2) The capsules of mosses make beautiful objects to study. Carefully cut the stalk (seta) of some moss capsules at different stages of development and bring the capsules into the laboratory. Put some plasticine onto a microscope slide and poke the base of a capsule into the plasticine. Put the specimen under the microscope and observe it under low power with a reading lamp shining onto the specimen. This is viewing by 'reflected light' instead of the usual 'transmitted light'. The heat from the lamp also helps the next bit. With two mounted needles, you may be able to remove the cap (calyptra) from the capsule. You can sometimes do this by popping the calyptra off by poking it from opposite sides at the same time. Some calyptra can be lifted off by tugging at them with forceps. The peristome teeth should now be visible. These are responsible for allowing the spores out in the best weather for dispersal. They are most beautiful. If you breathe gently on the capsule, whilst looking down the microscope you should see the teeth move. Does your damp breath cause the teeth to close, or to open. Can you explain how this mechanism assists the dispersal of the spores from the capsule? There are often two rows of teeth - do you think each has a different job to do?
Did you know:
1. That mosses have a life-cycle which is very different from that of other land plants? The green leafy part of mosses (and liverworts) is haploid. The sperm and egg cells are produced in special organs (called antheridia and archegonia) by haploid mitosis.
2. That mosses produce sperm cells? Each sperm has two tails (flagella). Moss sperm find moss eggs by swimming through the film of water which covers mosses e.g. after heavy rain. They navigate by following a chemical given out by the female parts (archegonia) of the moss plant.
3. That a diploid zygote forms when a moss sperm cell fertilises a moss egg? This zygote develops into the stalked capsule which we looked at above.
4. That meiosis takes place in this capsule? The products of this meiosis are numerous tiny haploid spores which are dispersed by air currents when the capsule opens.
5. That each tiny haploid spore can develop into a new haploid moss (or liverwort) plant?
Richard Price and John Hewitson
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