Photosynthesis and Respiration
Dial up light, CO₂, temperature, hours of daylight and chamber size, and watch a leaf in a sealed chamber photosynthesise in the light and respire all the time. Chamber CO₂ falls by day and rises by night, while a light-response graph shows where photosynthesis matches respiration and then levels off.
Preview — sign up free to change the numbers yourself
What you can adjust
- Light intensity
- 0 – 1500 µmol/m²/s
- CO₂ at the start
- 200 – 1000 ppm
- Temperature
- 5 – 40 °C
- Hours of light per day
- 0 – 24 h
- Chamber volume
- 10 – 500 L
How much light reaches the leaf while the lamp is on, in micromoles of photons per square metre per second. Photosynthesis climbs steeply at low light, then levels off once something else limits it.
The carbon dioxide in the sealed chamber when the run begins. Outdoor air today is about 420 ppm. The leaf can only use what is in the chamber, so this changes how much it can photosynthesise.
Photosynthesis is fastest around 25 to 30 °C and collapses above about 38 °C as its enzymes begin to fail. Respiration keeps climbing with temperature, roughly doubling for every 10 °C.
How many hours of each 24 hour cycle the lamp is on. The rest is darkness, when the leaf only respires and the chamber's CO₂ rises.
The volume of sealed air around the single 20 cm² leaf. A small chamber holds little CO₂ for the leaf to use, so its CO₂ swings further and photosynthesis slows sooner.