Expression of <i>PCN</i> (Fig. 2a) and <i>PCN</i> paralog Pt-ATHB.11 (Fig. 2b) in organs, as assayed by Quantitative Real Time PCR.

<p>Relative expression of <i>PCN</i> and paralog Pt-ATHB.11 in apices, leaves, roots, and stem was determined using Quantitative Real Time PCR (QRT-PCR) of two month old tissue culture grown <i>Populus tremula x alba</i>. <i>PCN</i> and paralog Pt-ATHB.11 are expressed in all tissues assayed, and are highly expressed in shoot apexes and stem tissue with active cambium. Stem tissue samples were confirmed to have a vascular cambium by phloroglucinol staining of secondary xylem. Relative expression (Mean ± SE) was calculated from triplicate QRT-PCR reactions of independent RNA samples prepared from different trees.</p>