Paired Arabidopsis samples surveyed with microarrays in this study. A total of 19 samples were grouped into 20 hybridization pairs representing abiotic and biotic stressors and tissue-specific sets; subsets of experiments are color-coded as in Figures 6 and 8. mRNA from each plant sample was labeled with Cy3 or Cy5 fluorescent dye as indicated and the collection of hybridizations was replicated with dye labels reversed.