Expression in the organ and tissue dataset. Microarray data were retrieved from the Genevestigator database. Background was defined for each probe set as the mean intensity of all samples the probe set was called 'absent' (not significantly higher (p < 0.06) than the signal observed with the corresponding mismatch probe set). a) Histogram describing the frequency distribution of P450 genes expressed in the organ and tissue data set. Given in each bin is the number of probe sets representing P450 genes expressed more than twofold above background in 0% to 5%, 5% to 10%, etc., up to 95% to 100% of the 277 organ and tissue hybridization experiments. The number of genes in each bin is given on top of each bin. b) Genes that are expressed in more than 80% of root, whole flower, or leaf samples (>twofold above background), but not in more than 20% of all other samples (from a total of 277 samples) were selected. Shown are expression data of these genes in leaf, root, and flower samples as indicated on top. Expression intensities are compared to background (defined as the mean intensity of all samples called 'absent'