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Biology
Photosynthesis
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Explore photosynthesis through controlled experiments, pathways inside a leaf, C₃/C₄/CAM strategies and a starch test.
A/B experiment
Press Run, then turn lamp B off. Watch what continues in the dark.
Simulation time: 0.0 s
Lock B's conditions into A and start a new measurement.
relative units/simulation minute
| P − R = N | A | B |
|---|---|---|
| P · Photosynthesis | 66.7 | 66.7 |
| R · Respiration | 4.0 | 4.0 |
| N · Net exchange | 62.7 | 62.7 |
Photosynthesis exceeds respiration: net CO₂ uptake, O₂ release and organic matter gain.
Organic matter change ΔS
A 0.0 · B 0.0
Relative to the start; a negative value means loss, not negative sugar.
A and B have identical conditions. Change one factor in B.
Difference in N (B − A): 0.0
Stomata and limits
- Stomatal opening index B
- 1.0
- Transpiration index B
- 100.0
- Light capacity
- 71.4
- CO₂ capacity
- 66.7
P uses the smaller capacity, then applies the temperature factor. Controlled comparisons test limiting factors.
Accumulated organic matter supports growth and food webs. Yield also depends on respiration, species, time and allocation; these indices cannot be converted into crop production.
Change one condition, then record an A/B pair to compare outcomes.
Net exchange over time
100A ━ · B ┄
0
Press Run to collect data. A: solid · B: dashed.
Data table
| s | N(A) | N(B) |
|---|
* Condition changed
Model notes
- A/B represents two hypothetical C₃ leaf samples with equal area and open gas exchange. Supplied CO₂, temperature and water status are controlled independently. It is not a sealed chamber or a whole plant.
- P, R, N = P − R and ΔS are relative indices, not calibrated for a real species. Photorespiration is omitted; respiration depends on temperature and continues in light. The model's peak P at 25 °C is not a universal optimum.
- The model takes the smaller of light and CO₂ capacities and applies a temperature factor. Water affects stomatal opening. Transpiration is an index, not a percentage or volume; it can exceed 100 and does not deplete water.
- Gas exchange assumes an ideal carbohydrate balance, not a universal measured gas ratio. Carbon in organic matter comes from CO₂; photosynthetic O₂ comes from water. Light rays represent energy.
- Rates respond instantaneously. One real second equals one simulated second, up to 120 seconds. Acclimation, growth and crop yield are not modelled. ΔS is change from the beginning, not an absolute sugar store.
- Inside a leaf and C₃/C₄/CAM are qualitative diagrams independent of A/B rates. Light reactions supply ATP/NADPH; Calvin is not restricted to darkness. Typical C₄ separates initial fixation and Calvin in space, CAM in time.
- The iodine test is virtual, using a destarched sample with abbreviated time and preparation. Blue-black indicates starch under the model's conditions; this is not a procedure for heating alcohol or handling chemicals.