The effect of light intensity on photosynthesis can be investigated in water plants. Use Cabomba or Elodea, which are sold in aquarium shops.
The plants will release bubbles of oxygen – a product of photosynthesis – which can be counted.
A lamp with an LED bulb is set up at different distances from the plant in a beaker of water:
The bubbles produced over one minute periods are recorded.
To investigate the effect of light intensity on the rate of photosynthesis.
Care must be taken when using water near electrical equipment. Ensure that your hands are dry when handling the lamp.
The volume of oxygen produced could be measured by collecting the gas produced in a gas syringe.
The changes in the oxygen concentration in the water could be measured using data logging equipment.
You could investigate the effect of different wavelengths of light on photosynthesis.
Use coloured acetate filters to investigate the effects of the blue, green and red parts of the spectrum on photosynthesis.
The effect of the presence or absence of chlorophyll on photosynthesis can be investigated using a variegated plant. Variegated plants have regions of their leaves with, and without, chlorophyll.
Only those areas of the leaf with chlorophyll photosynthesise. They will test positive for starch, which is built up from the glucose produced.
Care must be taken when using boiling ethanol. Make sure that no Bunsen burners are turned on as the ethanol is highly flammable.