0.0833
µmol/cm²/s
833.33
µmol/m²/s
835.33
µmol/m²/s
0.0833
µmol/cm²/s
833.33
µmol/m²/s
835.33
µmol/m²/s
The Photosynthesis Rate Calculator computes the net and gross photosynthesis rates of a leaf or plant based on CO₂ absorption measurements. Photosynthesis is the fundamental biological process by which plants convert light energy into chemical energy, fixing atmospheric CO₂ into organic compounds. Measuring photosynthesis rate is essential for plant physiology research, crop science, ecology, and climate studies.
Enter the total CO₂ absorbed during your measurement period, the leaf area, measurement duration, and the dark respiration rate to obtain both net and gross photosynthesis rates expressed in standard units.
The calculator computes photosynthesis rates as follows:
Net photosynthesis represents the total CO₂ fixed minus the CO₂ released by respiration. Gross photosynthesis represents the total amount of carbon fixation by the Calvin cycle before accounting for respiratory losses. Dark respiration rate is measured separately by enclosing the leaf in darkness and measuring CO₂ release. Results are converted to µmol/m²/s, the standard unit used in plant science.
Inputs
Results
A sunflower leaf absorbing 50 µmol CO₂ over 10 cm² in 60 seconds has a very high net rate of about 833 µmol/m²/s.
Inputs
Results
A shade fern absorbing 5 µmol over 20 cm² in 2 minutes shows a modest net rate of about 21 µmol/m²/s.
Net photosynthesis is the amount of CO₂ actually removed from the atmosphere, measured as the difference between CO₂ fixed by the Calvin cycle and CO₂ released by the plant's own respiration. Gross photosynthesis is the total CO₂ fixed before subtracting respiratory losses. Gross = Net + Respiration. In most plants, respiration consumes about 30-50% of gross photosynthesis.
Typical net photosynthesis rates for C3 crops (wheat, rice, soybean) range from 15-25 µmol CO₂/m²/s, while C4 crops (maize, sugarcane, sorghum) can reach 30-40 µmol/m²/s or higher. CAM plants (cacti, pineapple) have lower instantaneous rates. Maximum rates occur under saturating light, optimal temperature, and adequate water and CO₂ supply.
Dark respiration occurs continuously in plant cells, even during photosynthesis. When you measure CO₂ uptake by an illuminated leaf, you are measuring net photosynthesis (gross fixation minus simultaneous respiration). To estimate gross photosynthesis, you must add back the respiratory CO₂ release, which is measured by darkening the leaf and recording CO₂ output.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
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