In the Jasper Ridge Global Change Experiment, microarrays were used to investigate the changes in gene expression of the dominant dicot Geranium dissectum, in response to four simulated global change factors: N deposition, elevated CO₂, added rainfall and warming. The approach was based on cross-species hybridization to an Arabidopsis cDNA microarray, using Arabidopsis genomic DNA as a common reference. Of the 15,000 features on the array, 8,000 gave good signals with Geranium. The ability to monitor coordinated patterns of gene expression gives us insight as to how the plants are responding to changes in their environment.

In response to simulated N deposition, the transcripts levels for several photosynthesis genes were elevated but transcript levels for genes involved in nitrate uptake and assimilation remained the same. A suite of genes previously reported to be induced in response to phosphate deficiency, including genes for the glycolytic bypass pathway, a phosphate transporter, ADP-glucose pyrophosphorylase and inorganic pyrophosphatases, was co-ordinately up-regulated in response to the addition of nitrogen. The existence of a phosphorus limitation was confirmed by measurement of phosphorus in G. dissectum leaves. This showed that phosphorus levels on a dry weight basis were sub-optimal for growth in plants from elevated nitrogen plots. Thus, although plants commonly produce more biomass when grown in elevated nitrogen conditions in undisturbed grasslands, this growth response may be constrained by sub-optimal levels of available phosphorus.