Seed searching (1hr)
Take a collection of fruits (apples, grapes, kiwi fruit, tomatoes, peaches, melon) and ask the children to dissect them in search for the seed(s). Collect and count them (estimate in the case of the kiwi!). Try planting some of the seeds in mini-pots of soil and keep the pots in grip-seal plastic bags to create a particularly warm and humid environment to encourage germination.
Edible roots (20 min)
Begin with a carrot top (inc. leaves) buried in a box of soil or sand so that only the top is showing. Do a quick survey of the class and we would suggest that <50% will guess that it is a carrot. When you reveal its identity, ask them what part of a plant is a carrot – have they ever eaten roots since carrots are swollen roots. Discuss other ‘root vegetables’
Germination (45 min – 1 hr)
What is germination? You need a definition before you start this experiment. We consider it the production of both roots and shoots from a seed. Germination is a great subject for designing ‘a fair test’ and looking at the factors that affect germination. There are many you can test and we are always led by the children in terms of which factors they wish to investigate eg. water, food, sunlight, warm temp, - worth remembering here that seeds will germinate in a fridge (they just take longer), give them too much water and they may become waterlogged. All the energy a seed needs for germination is packed within it, so additional food is not necessary – as you will see below, we germinate on wet filter papers. If they want to place their seeds in the freezer, try it, they will not germinate but it may not kill them: the petri-plate can then be left in optimal conditions for an extra week to show this. Again, this links nicely to the survival of seed under snow (in fact, farmers used to store grain in this way).
Traditionally we use wheat seed for this experiment but beans or maize (sweetcorn) seeds are probably more easily obtained and work just as well. Place 10 seeds on a petri-plate lined with a piece of wet filter paper. Do not have water splashing around. Try to give each child a plate. Place in different environments (eg. light/dark – cover with foil) and leave for no more than a week. Determine the % germinated under each condition that you test and determine the optimum conditions for germination. With bean seeds, completely cover with water and soak for 24 hrs to ensure they germinate – imbibing water from a filter paper will take too long!
The colour of germination (15 min)
As an extension activity to the germination test, children should be challenged to observe the colour of the shoot as it appears from the seed and to compare this between plates germinated in the light and in the dark. Remember it’s dark below the soil surface and so chlorophyll production as a result of photosynthesis will not have occurred and shoots will be white/colourless. What colour are roots?
Investigating Root Power (45 min)
Advance preparation required here – begin with some already germinated seeds (again use beans or sweetcorn as they are large and germinate fairly quickly). Also enough egg shells for the whole class – half of one each.
Working with hand-lenses the children should draw a germinated seed in detail, looking for root hairs, seed coats & shoots and recording colours, and finally label all the parts (note colours – see above). Place a teaspoonful of soil in the base of the egg-shell and plant the germinated seed in the soil. Children may like to paint the egg shells in advance or write on them the words ‘root power’. Place the eggs on some paper/card in a warm place. Keep the soil moist and in less than a week the roots should have grown through the egg shell. Think about what they have to negotiate in the field!