Orchidoid mycorrhizae (OM), as the name suggests, are characteristics of roughly the 20,000 species in the orchid family, and are not known in any other group. Orchids are unusual in that they pass through an obligate mycoparasitic stage in the course of normal development. Like other mycoparsitic plants, they have a number of structural specializations to this way of life, including their own distinctive form of mycorrhiza.

Orchid Seeds

Orchid seeds are dust-like, consisting of a tiny spherical embryo with no endosperm and a thin seed coat (Arditti & Ghani, 2000). As such, these minute seeds contain very small amounts of high-energy protein and lipid, and very little sugar (Arditti, 1979; Richardson et al., 1992). If the seeds are spread on a moist substratum, the undifferentiated embryos absorb water, swell slightly and may burst the testa, and sometimes produce epidermal hairs. Thus these seeds do not develop further unless it receives an...