Figure 4:

An example model showing hybrid ODE/SSA simulation. This model of photosynthesis, adapted from Whitmarsh and Covindjee (1999), couples an external time-varying input (sunlight, green) with a reaction network. Diffusion in and out of the volume of interest is simulated deterministically, while the reaction that creates sugars (carbohydrates, red) is stochastic when the population of carbohydrates is low (time < 17) and switches to deterministic after time ≈ 17 because the calculated noise crosses below the tolerance threshold.