This calculator helps estimate the rate of photosynthesis based on light intensity and CO2 concentration. Photosynthesis is the process used by plants, algae and cyanobacteria to convert light energy into chemical energy, through a process that uses sunlight, water and carbon dioxide.
Photosynthesis Rate: — µmol CO2 m⁻² s⁻¹
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function calculatePhotosynthesisRate() {
var lightIntensity = parseFloat(document.getElementById("lightIntensity").value);
var co2Concentration = parseFloat(document.getElementById("co2Concentration").value);
var leafArea = parseFloat(document.getElementById("leafArea").value);
var photosynthesisRateOutput = document.getElementById("photosynthesisRateOutput");
if (isNaN(lightIntensity) || isNaN(co2Concentration) || isNaN(leafArea) || lightIntensity < 0 || co2Concentration < 0 || leafArea <= 0) {
photosynthesisRateOutput.textContent = "Invalid input. Please enter positive numbers for all fields, and a positive leaf area.";
return;
}
// A simplified model for photosynthesis rate.
// This is a highly generalized approximation. Real photosynthesis rates depend on many factors including
// temperature, water availability, plant species, and light spectrum.
// This formula assumes that both light intensity and CO2 concentration are limiting factors,
// and the rate increases with both up to a saturation point (not modeled here).
// The leaf area is used to normalize the rate per unit area.
// Assume a base rate constant and factors for light and CO2.
// These constants are illustrative and not derived from a specific scientific model.
var baseRateFactor = 0.05; // Illustrative factor relating light intensity to CO2 uptake
var co2LimitingFactor = 0.01; // Illustrative factor for CO2 impact
var rate = baseRateFactor * lightIntensity * (co2Concentration / 1000) * (leafArea / 100); // Normalize CO2 and Leaf Area
// A very basic saturation effect might be introduced, but for simplicity, we keep it linear for now.
// In reality, photosynthesis saturates at higher light intensities and CO2 concentrations.
// The units of this calculation are inherently approximations due to the simplified model.
// We are aiming for a representation of CO2 uptake per unit of leaf area per unit of time.
// The output unit is µmol CO2 m⁻² s⁻¹.
// To get to the desired output unit, we need to consider how the inputs relate.
// Light intensity is µmol photons m⁻² s⁻¹. CO2 concentration is ppm (parts per million). Leaf area is cm².
// A common way to express photosynthesis rate is in terms of CO2 uptake per unit leaf area per unit time.
// For example: µmol CO2 m⁻² s⁻¹
// Let's adjust the calculation to be more conceptually aligned with the output unit.
// We can model the rate as proportional to the minimum of a light-dependent rate and a CO2-dependent rate,
// scaled by leaf area.
// Light-dependent rate (simplified, assumes linear response up to saturation)
var lightRate = 0.005 * lightIntensity; // Arbitrary scaling factor for light
// CO2-dependent rate (simplified, assumes linear response up to saturation)
var co2Rate = 0.02 * (co2Concentration / 1000); // Arbitrary scaling factor for CO2, normalized to a fraction
// The overall rate is often limited by the more limiting factor.
// For simplicity, we can take an average or a product, but a more accurate model would use Michaelis-Menten kinetics.
// Let's use a product as a simplification that both factors contribute.
var calculatedRate = lightRate * co2Rate;
// Scale by leaf area and convert units.
// We want µmol CO2 m⁻² s⁻¹.
// Our `calculatedRate` is roughly proportional to CO2 uptake.
// Let's scale it to reflect the output unit better.
// If lightRate is µmol CO2 m⁻² s⁻¹ (hypothetically) and co2Rate is dimensionless factor,
// then calculatedRate is µmol CO2 m⁻² s⁻¹.
// We need to account for the leafArea input which is in cm². We want rate per m².
// 1 m² = 10000 cm². So, leafArea (cm²) / 10000 = leafArea (m²).
var finalRate = calculatedRate * (leafArea / 10000); // Scale to per m²
// This is still a very rough approximation. A more scientifically accurate calculator would be complex.
// Let's try to make the output more direct based on typical relationships.
// A common representation relates light saturation (e.g., PPFD) and CO2 concentration to net CO2 assimilation.
// Let's make a simple proportionality:
// Rate is proportional to (Light / (Light + Light_Saturation)) * (CO2 / (CO2 + CO2_Saturation)) * Vmax
// For this calculator, we'll simplify it greatly.
// Simpler approach: Assume rate is proportional to the minimum of two potential rates, one limited by light, one by CO2.
// Let's assume:
// Light limited rate: Rate_L = k_L * LightIntensity
// CO2 limited rate: Rate_C = k_C * CO2Concentration
// Photosynthesis Rate = LeafArea * min(Rate_L, Rate_C)
// Units:
// LightIntensity: µmol photons m⁻² s⁻¹
// CO2Concentration: ppm
// LeafArea: cm²
// Output: µmol CO2 m⁻² s⁻¹
// Let's define some illustrative constants (these would normally come from experimental data).
var K_L = 0.001; // Arbitrary constant for light response, unit would be (µmol CO2 m⁻² s⁻¹) / (µmol photons m⁻² s⁻¹)
var K_C = 0.05; // Arbitrary constant for CO2 response, unit would be (µmol CO2 m⁻² s⁻¹) / ppm
var lightContribution = K_L * lightIntensity;
var co2Contribution = K_C * co2Concentration;
var limitingRate = Math.min(lightContribution, co2Contribution);
// Now we need to incorporate leaf area. We want the total rate for the given leaf area, in µmol CO2 m⁻² s⁻¹.
// If `limitingRate` is the rate per m², we multiply by the leaf area in m².
var leafArea_m2 = leafArea / 10000; // Convert cm² to m²
var totalPhotosynthesisRate = limitingRate * leafArea_m2;
// Ensure the result is not negative and display it.
var finalRateValue = Math.max(0, totalPhotosynthesisRate);
photosynthesisRateOutput.textContent = finalRateValue.toFixed(2);
}