Time course of colonization of poplar roots by L. bicolor in an in vitro sandwich culture system. A and B, L. bicolor and poplar precultures, respectively. C to E, Root development of poplar at 3 DODI (C), 10 DODI (D), and 30 DODI (E). Note the increasing LR number starting at 10 DODI. Root swelling at the LR basis started at 10 DODI, and LR arrest was observed at 30 DODI. F, L. bicolor hyphae from precultures after UVitex staining. G, Transverse root section after propidium iodide UVitex dual staining (green, UVitex; magenta, propidium iodide). H to J, Dual fluorescence-stained transverse root sections at 3 DODI (H), 10 DODI (I), and 30 DODI (J). Co, Cortex; Ep, epidermis; HN, Hartig net; M, mantle; RC, root cap cells; RH, root hair. Note hyphae attachment at 3 DODI and mantle and Hartig net development from 10 to 30 DODI. In H, single, magenta-colored cells surrounding the epidermis are detached root cap cells. Images shown are representative from a series of three experiments. Bars = 10 μm.