Hierarchical clustering showing the expression pattern of transcripts expressed more than once in any of the 16 different growth conditions. The blowup shows some of the genes differentially expressed in the high CO2 libraries (C1 and C4). Expression levels are shown in an increasing scale from grey to dark blue, and are based on frequencies of ESTs in each library (see Materials and methods). NA, no annotation information available. For two-letter library codes, see Table 1.