Relative QPCR transcript levels for maize ZmCEL genes in internode 12. Transcript correlations of r2 of 0.9 or greater are shown. A: ZmCEL2, ZmCEL7, ZmCEL10, ZmCEL19 and ZmCEL20 all had high transcript levels in the mature zone of elongating vascular bundles, and B: similarly, ZmCEL1 and ZmCEL3 also showed highest levels of transcript in the mature zone of elongating vascular bundles, however, transcript was present in some elongating tissues. The stages of development examined included EARLY (V11), V14 and V16. P, R and VB refer to pith, rind and vascular bundle, respectively. E, M and T refer to elongation, maturation and transition zones, respectively.