Symbiotic Fungi: Principles and Practice (Soil Biology)

22 A. Das and A. Varma
a
b
Root hair Smallest hyphae
Not inoculated with mycorrhizae Inoculated with mycorrhizae
Fig. 1.7 (a) Comparison of size of diameter of a fungal hypae with a root hair. (b) Difference
between nonmycorrhizal and mycorrhizal root. Formation of arbuscules in roots inoculated with
arbuscular mycorrhiza which facilitates the absorbtion of soil nutrients
1.10.1.3 Interactions with Other Soil Organisms
Mycorrhizal fungi interact with a wide assortment of organisms in the rhizosphere.
The result can be positive, neutral, or negative on the mycorrhizal association or a
particular component of the rhizosphere. For example, specific bacteria stimulate
EM formation in conifer nurseries, and are called mycorrhization helper bacteria. In
certain cases, these bacteria eliminate the need for soil fumigation (Garbaye 1994).
The interaction between rhizobia and arbuscular mycorrhiza (AM) fungi has
received considerable attention because of the relatively high phosphorus demand
of nitrogen fixation. The two symbioses typically act synergistically, resulting
in greater nitrogen and phosphorus content in combination than when each is
inoculated onto the legume alone. Legumes are typically coarse-rooted and therefore
inefficient in extracting phosphorus from the soil. The AM fungi associated