Scatterplots of the Affymetrix ATH1 Arabidopsis Array for magnetic field data. The 9 day-old plants were exposed to a field of 21 Tesla for 6.5 hours and compared to control plants that had been maintained in the bore of the magnet for the same amount of time without an applied field. In (a), each data point represents the level of differential expression for each of the 8000 genes represented on the microarray, and the axes are logarithmic. Genes of interest that were chosen for further quantification are indicated with boxes, see text. The large yellow spots represent "housekeeping" genes that are typically unaffected by abiotic stress. The two parallel lines represent the 2-fold increase or decrease limits. The data in (a) replotted in (b) using a topographical routine , where the color gradient designates the number of genes appearing in a given localized region of the graph.