ABSTRACT
Technically, most higher plants (ferns, soft wood trees, and flowering plants) do not have roots but mycorrhizae (literally “fungus-root”), a combined structure formed when a mycorrhizal fungus infects the roots of a higher plant (Harley and Smith, 1983). Although plants in a few families, such as the brassicas (Brassicaceae), nettles (Urticaceae), rushes (Juncaceae), and sedges (Cyperaceae), do not form any type of mycorrhizae, they are very much in the minority. Mycorrhizal relationships have been around for a very long time and are evident in 460-million-year-old Devonian fossils (Redecker et al., 2000). Over time the fungi have become very specialized so that most cannot survive unless they are in contact with a host plant. Many plants have also become equally dependent on mycorrhizal fungi. This association is generally a beneficial one, with the host plant providing the obligate mycorrhizal fungus with a place to live and organic nutrients. In return, the fungus provides benefits to the plant, for example, by stimulating the uptake of soil nutrients, especially phosphorus (P), and water (Harley and Smith, 1983). The mycorrhizal fungi are, therefore, the most natural of the biofertilisers although not all of them are mutually beneficial (Smith and Read, 1997).
