How do we in school take care of the enthusiasm children show for biology? Small children often show a spontaneous keen interest in animals, flowers and nature. Their curiosity leads to many questions. One way to take care of this interest could be to do very simple practical work in the classroom or in the neighbourhood.
I want to give my impressions about a very easy laboratory experiment with plants I have tested on 10-11 year old pupils in a nine-year compulsory school. The experiment is the same as given at university, but simplified. However, theory and conclusions are the same. The experiment has many advantages: it is easy to prepare and carry out, it gives very clear results, it requires very little equipment and it is cheap. Besides these characteristics theory is simple.
The experiment shows the great importance light have on development of seedlings. Different peas (Pisum sativum sp) were imbibed overnight, carefully washed in lukewarm water and then sown in a mixture of soil, peat and sand in pots. Each group put two pots on a bench for daylight conditions and two pots in a dark-box. The dark-boxes were made by a carpenter but cardboards with appropriate lids could be used instead. It was very important that the dark-grown seedlings didn’t receive any light. Watering of seedlings etc was made in a locked dark toilet! As green light isn’t absorbed by plants torches provided with green-Plexiglass were used when checking the dark-grown seedlings.
The experiment was completed after two school-weeks, when seedlings with and without light were compared. The result was striking. Seedlings without light were very tall, pale and flabby. They had hardly any leaves and some had a ‘hook’, a curve near the top. Form, shape and colour of the dark-grown seedlings could easily be explained when we consider that dark-grown seedlings will develop in the dark-box as in the soil. They are tall as they grow fast and struggle for light, they are pale as chlorophyll synthesis requires light and they do not develop any leaves as leaves would be destroyed in the soil. The hook is an adaptation to protect the sensitive shoot tip of the seedling. Explanations of the differences between light- and dark-grown plants could be given without deep knowledge of the different developmental systems in plants.
Moreover, laboratory experiments on plants are excellent as an entrance gate to maintain and increase interest in biology and natural science. I will now give some criteria for this statement.
1) Plants are well-known to all children.
2) Plants are easy to cultivate.
3) Experiments with plants are easy to prepare. Seeds, soil and pots are easily bought at a garden centre.
4) Experiments with plants are cheap. Seeds, soil and pots do not cost much per laboratory work group. This in turn means that pupils could work in small groups, which of course is best from an educational point of view. Most experiments do not require any complicated equipment.
5) Experiments with plants are not dangerous if you avoid plants with toxic and/or allergenic substances. Compared to experiments with animals, where you have to take ethical and sometimes medical aspects into consideration, work with plants is easier.
6) Some experiments give inspiration to attendant tasks or stimulate to design new experiments. Creativity is promoted.
7) It is very important in this computer-oriented world to provide pupils with hands-on, practical activity.