The development of the fungal sheath on Cistus incanus short roots

Sheath development of mycorrhizae of Cistus incanus L. ssp. incanus + Tuber melanosporum Vitt. synthesized under gnotobiotic conditions was studied by anatomical and ultrastructural techniques. Root systems examined at different times after inoculation exhibited short lateral roots which could be categorized as follows: (i) uninfected; (ii) with hyphae in the dead outer root cap cells; (iii) with developed sheaths. In the last case the inner hyphae of the sheath penetrated through remains of dead root cap cells which were trapped in the inner sheath. Remains of root cells were also found in the outer sheath. Growth of hyphae into the dead layers of the root cap leads to formation and development of the sheath.