In situ localization of Pinus radiata SHORT-ROOT ( PrSHR ) mRNA. A, B) Transverse sections of hypocotyls from 90-day-old seedlings at time 0 (A), and after 24 h of culture in the presence of 10 μM indole-3-butyric acid (IBA) (B). C, D) Transverse sections of epicotyls from 90-day-old seedlings at time 0 (C), and after 24 h of culture in the presence of 10 μM IBA (D). The sections were hybridized with an RNA probe obtained by in vitro transcription of PrSHR in either the antisense (A, B, C, D) or sense (E, F) orientation. Note the absence of hybridization in the controls. Similar results were obtained using an RNA probe obtained by in vitro transcription of PrSCL1 in either the antisense or sense orientation. ab, axillary bud; c, cambial region; co, cortex; r, resin canal; x, xylem. In situ localization of PrSCL1 and PrSHR had already been described in competent hypocotyls from 21-day-old seedlings during adventitious rooting . SCL, SCARECROW-LIKE.