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

Abstract

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.

• ecology
• microscopic survey
• Monotropoideae
• monotropoid mycorrhizae
• root architecture

We are grateful to M. I. Bidartondo (University of California at Berkeley) for his invaluable comments on the manuscript. We also thank Dr. S. Ito and the members of the Laboratory of Forest Pathology and Mycology, Mie University, for their support. The Dr. Kazuhiko Kasai, recently deceased, kindly provided us (A. Y.) with information of plant distribution at Mount Yatsugatake. This study was supported in part by Grant-in-Aid for Scientific Research from the Japan Ministry of Education, Science, Sports and Culture (No. 11460070).