Response curves

The archetypal dose-response curve is the one described by Mitscherlich (1909), with at the left a part (marked by an A) where a given environmental factor (e.g. Nutrient supply) is limiting the plant trait of interest (e.g. Yield), then a region (B) where the environmental factor is optimal, and subsequently a range (C) where the environmental factor is supra-optimal for that trait:

SLA-1st part
The above graph also illustrates an interesting problem. Suppose that 2 experiments are carried out, one with species X and investigator M, and one with species Y by investigator N. The results for the first experiment are the red points in the graph, the results for the second are the blue points. When we try to generalise across these experiments, we would conclude from the first experiment that the environmental factor has a positive effect on the trait of interest, whereas the 2nd experiment suggests that there was no effect at all. In reality, it might be that the species X and Y follow exactly the same dose-response curve, but that the two experiments comprised rather different parts of this curve.

Of course, it could also be that the 2 species behave differently because they were grown at very different other conditions (e.g. growth chamber versus glasshouse) or behave differently because they occupy different ecological niche, or simply because the two species have evolved from different ancestors. Also these alternatives can be analysed with the MetaPhenomics approach.