Photosynthesis Rate Calculator
Calculate gross and net photosynthesis rate from O2 evolution or CO2 fixation data. Find compensation point, light saturation, and quantum yield for plant or algae photosynthesis.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Photosynthesis Rate Calculator | — | Net PS = Gross PS - Respiration | μmol O2/m²/s |
Step-by-Step Examples
Gross PS = 15 μmol O2/m²/s, Respiration = 3 μmol O2/m²/s.
- Net PS = 15 - 3 = 12 μmol O2/m²/s
- Plant is gaining carbon (net carbon fixation)
- Compensation point: gross PS = respiration (3 μmol O2/m²/s)
What light level needed for net PS = 0?
- At compensation point: Gross PS = R
- If R = 3 μmol O2/m²/s then plant needs exactly 3 μmol O2 gross
- Below this light: plant loses carbon (negative net PS)
At 500 μmol photons/m²/s light: Gross PS = 15.
- Quantum yield = O2 evolved / photons absorbed
- = 15/500 = 0.030 mol O2 per mol photons
- Maximum theoretical: 0.125 (8 photons per O2)
- Practical: 0.04-0.08 for most plants
Real-World Applications
Common Mistakes to Avoid
Gross = total O2 produced. Net = O2 actually observable (gross - respiration). At night: only respiration (all dark, net = -respiration).
Beyond light saturation: more light gives no more photosynthesis. Excess light can cause photoinhibition. Most plants saturate at 500-1000 μmol/m²/s.
C4 plants (corn, sugarcane) concentrate CO2 around RuBisCO, reducing photorespiration. More efficient at high temperatures and light. C3 plants (wheat, rice, trees) are most common.