<p>(A) Seedlings inoculated with <i>P. indica</i> for 8 weeks showed significantly enhanced growth and root development. (B–D) Anatomic structures of roots colonized by <i>P. indica</i> for 24 hours. Hyphae (green spots in B, arrow head) and penetration site (red spots in C, arrow head) were overlayed in bright field (D, arrow head). Bar = 50 µm. (E) Microscopic structure of roots colonized by <i>P. indica</i> for 5 days. A large number of hyphae were widespread over the root surface and tip, elongation zone and mature zone. Bar = 200 µm. (F, G) Microscopic structures of transverse sections and longitudinal sections of roots colonized by <i>P.indica</i> for 5 days. Hyphae fully colonized the velamen. Chloroplast autofluorescence (red) was also detected in cortex. Bar = 200 µm. (H) Microscopic structures of transverse section of roots colonized by <i>P. indica</i> for 5 days. <i>P. indica</i> was restricted in the velamen and not detectable in the exodermis of <i>Oncidium</i> roots. Chloroplast autofluorescence (red) was detected in cortex. Bar = 50 µm. (I) Micrograph of root cross sections from seedlings colonized with <i>P. indica</i> for 5 days. Without chlorophyll fluorescence in velamen, the penetration sites (red spot) were clearly detected. Bar = 20 µm. (J) Growth quantification of seedling colonized with <i>P. indica</i> for 8 weeks. Fresh weight, plant height, leaf number, leaf wide, stem diameter, root number and diameter were analyzed. Error bars represent SD for three independent experiments. *, <i>P</i> value<0.05; **, <i>P</i><0.001. Hyphae were stained with chitin-specific WGA-AF488 (green). Penetrated sites (Ps) were stained with lectin-specific conA-AF633 (red) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084920#pone.0084920-Zuccaro1" target="_blank">[88]</a>. Samples were analyzed and photographed with an Olympus IX71 inverted microscope system (Japan). Ve, velamen; EX, exodermis; Cort: cortex; Ch: Chloroplast. Hy, hyphae; Ps, penetration site.</p
