3.4. Observation of mycorrhizal fungi colonization
Base on the positive effects of Tulasnella isolates on the growth of D. officinale seedlings, transverse sections of roots infected by JC-02 and JC-05, respectively, were observed under a light microscopy after cultivation for 7 weeks. The fungal hyphae were observed in the velamen, exodermal passage cells, exodermis and cortex, but not in the endodermis and vascular bundle sheath. Some hyphae had formed pelotons and coils mycelium in the cortex of roots of JC-02+ plant and JC-05+ plant ( Fig. 7A–C). Transverse sections of roots (control) confirmed the lack of mycelium in the velamen, exodermal passage cells, exodermis and cortex as well as the endodermis and vascular bundle sheath (Fig. 7D).