Photosynthesis
This list suggests resources which can be used to investigate photosynthesis.
In primary school (Year 3), students will have explored the requirements of plants for life and growth (air, light, water, nutrients from soil, and room to grow) and how they vary from plant to plant, as well as investigating the way in which water is transported within plants. At this age the science will have been covered at a fairly basic level, but it is worth spending some time at the beginning of the unit to assess prior learning.
At Key Stage Three, photosynthesis is looked at in more detail, including:
• plants making carbohydrates in their leaves by photosynthesis and gaining mineral nutrients and water from the soil via their roots
• the role of leaf stomata in gas exchange in plants
• the reactants in, and products of, photosynthesis, and a word summary for photosynthesis
• the adaptations of leaves for photosynthesis.
Visit the secondary science webpage to access all lists: https://www.stem.org.uk/secondary-science
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.
Chlorophyll fluorescence
This activity allows students to see how chlorophyll can be energised and how this causes it to fluoresce. Chlorophyll in plant leaves absorbs red light and passes the energy on to other parts of the plant, hence leaves look green. But if there is nowhere for the energy to go, it is released as light again.
Measuring Photosynthesis with Cabomba
Cabomba is a highly reliable plant, especially compared to Elodea, for demonstrating photosynthesis.
Students observe bubbles of oxygen which are released as the plant carries out photosynthesis. These bubbles can be counted and the rate of bubbling can give an indication of the rate of photosynthesis. If you alter the light intensity, does the rate of bubbling vary?
Investigating Photosynthesis: Can Leaf Discs Make Starch in the Dark?
Once students have understood that carbon dioxide is the source of carbon in the starch formed by photosynthesis, and that starch is a carbohydrate made from the polymerisation of glucose, they can carry out this investigation to see whether starch is produced in leaves with and without light.
Observing stomata
Stomata control the movement of gases in and out of a leaf, making carbon dioxide available for photosynthesis and controlling the loss of water from the leaf through transpiration. This resource suggests several methods of observing stomata and which plants provide good results.
Because of the size of stomata, you will need a reasonably good microscope for this. Your choice of magnification will depend on the leaf material that you are using, and the size of the stomata. A few investigations are suggested.
To demonstrate how the guard cells control the opening and closing of stomata, you can use a balloon as shown in this video.
Seagrass and photosynthesis
This resource takes a slightly different slant on how plants can help reduce the build up of carbon dioxide in the atmosphere and thereby help prevent climate change. In the video Ben Ainslie, the Olympic gold medal winning sailor, explains how seagrass can be used to reduce carbon dioxide in the atmosphere.
