Using aquatic photosynthetic organisms
Environmental effects on photosynthesis can be investigated using an aquatic photosynthetic organism such as pondweed, algae or immobilised algal beads.
One approach is to collect the oxygen released during photosynthesis. The volume of oxygen produced in a fixed time can then be used as a measure of photosynthetic rate.
| Measurement | What it indicates |
|---|---|
| Volume of oxygen collected | Amount of oxygen released by photosynthesis |
| Fixed measurement time | Allows oxygen production to be expressed as a rate |
| Different lamp distances | Allows the effect of changing light intensity to be investigated |
Before measurements begin, air can be bubbled through the water. This encourages oxygen subsequently released by the plant to form bubbles instead of remaining dissolved.
The plant should also be well illuminated beforehand so that photosynthesis is already taking place when measurements begin.
Other factors
- Carbon dioxide concentration: sodium hydrogencarbonate can be used to provide different concentrations of dissolved carbon dioxide.
- Temperature: submerged photosynthetic material can be placed in water baths at different temperatures.