Fig. 3. Responsiveness of the basal meristem to auxin and specificity of DR5 auxin reporter maximum. (A) Transfer from MS medium to 10 µM NAA: induction of lateral roots all over the root (^*, visualized using CYCB1;1::GUS) and emergence of a big cluster in the basal meristem (arrowhead). (B) Quiescent center marker line (QC184) demonstrating differentiation in fused lateral root primordia (arrowheads). (C-E) DR5::GUS expression in apical part of root grown on MS medium for 40 HAG (C); transferred from MS medium to 10 µM NAA for 6 hours (D); and grown for 72 HAG on NPA (E). Scale bar: 100 µm. The boxed area in C indicates DR5::GUS expression in the basal meristem. Arrowheads mark the end of the root cap and start of the basal meristem. (F-H) Transverse sections through the basal meristem of seedling roots expressing DR5::GUS (F) and IAA2::GUS (G,H) grown on MS for 40 HAG (F,G) and on NPA for 72 HAG (H). ^*, protoxylem cells; p, pericycle layer.