Mycorrhizal morphology of Monotropastrum humile collected from six different forests in central Japan

A survey of the nonphotosynthetic plant Monotropastrum humile was conducted to determine its mycorrhizal status and characterize the fungal structures observed. Thirteen populations and 40 individuals were collected from six forest types, including coniferous and broadleaf trees, in central Japan. The nearly spherical root system of M. humile intertwines with the root systems of neighboring trees, and individual roots were branched up to third-order structure, forming monopodial-pinnate or monopodial-pyramidal morphologies. In addition to the formation of a fungal mantle and Hartig net in association with the epidermis, fungal penetration pegs consistently were observed around and within the epidermal cells. These structures indicate that the mycorrhizal status of M. humile is of the monotropoid type.