Temperature affects the rate of photosynthesis. In this interactive, the temperature of a solution surrounding a water plant can be manipulated. The resulting pH changes can be monitored with the help of the pH indicator Bromothymol blue (BTB). Generally, enzyme-driven biological reactions increase in speed with increasing temperatures. But this occurs only up to a certain temperature. This also applies to photosynthesis and the enzymes involved. Instructions: Drag the slider to see how temperature affects the photosynthesis rate of the water plant Elodea in a BTB solution. The graph will show the outcome of an experiment after 12 hours of shining light on the plant. Photosynthesis is measured as changes in pH with BTB. Select “Show oxygen” to see how much oxygen gas is produced by the plant and released as bubbles.