Here µ
denotes the growth rate coefficient at Si,
the limiting nutrient concentration; is
the maximum specific growth rate, and Ki, the
half-saturation value for the i th nutrient.
This applet gets you ready for more interesting models. The method of plotting deserves explanation. The blue and green lines are for each potentially limiting nutrient at the concentration shown on the abscissa. Excess means that the other nutrient is at a concentration that is not limiting. Permutations of mixtures of these nutrients could be plotted across the graph paper, but it would be hard to compare runs. Instead we have used the slider bars to select a percentage of the reference concentration for each nutrient.
Experiments
1. Select a concentration of one of the nutrients of about half of the reference concentration. Note the ranges where the other slider bar has no effect.
2. Set both slider bars to the far right and try to explain what you observe.
We simply evaluate each equation and use the lower value for the best guess for the specific growth rate coefficient. This is not accurate because actual data show that both concentrations can be important.