Symbiotic Fungi: Principles and Practice (Soil Biology)

20 A. Das and A. Varma
Fig. 1.6 Diagramatic representation of molecular taxonomic position of symbiotic fungi (cf. Das
et al. 2007)
Infection of each cortical cell takes place from the outer cortical wall; lateral spread
from cell to cell does not occur. Infected cells appear to be fully packed with fungal
hyphae. In the ericoid mycorrhizae, the host cell dies as the association disintegrates,
thereby restricting the functional life (i.e., nutrient absorption) of these
epidermal cells to the period prior to breakdown of the infected cell.
Arbutoid Mycorrhiza
The arbutoid mycorrhizae have characteristics which are found in both ECM and
other endomycorrhizae. Intracellular penetration of cortical cells and formation of a
sheath can occur, and a ‘‘Hartig’s net’’ is present. A feature distinguishing them
from ericoid mycorrhizae is the presence of dolipore septum in internal hyphae.
Fungal associates in arbutoid mycorrhizae belong to basidiomycetes.
Monotropoid Mycorrhiza
This group of mycorrhiza is associated with the achlorophyllous plants in the family
Monotropaceae. These mycorrhizae are very similar to the ECM, and form a
distinct sheath and ‘‘Hartig’s net’’. However, they exhibit a distinctive type of
intracellular penetration in cortical cells that is unlike other endomycorrhizal
types. The fungus forms a peg, into the cell wall.
Ect-endomycorrhiza
These are formed with the members of the Pinaceae. These mycorrhizae form a
‘‘Hartig’s net’’ in the cortex of the root, but develop little or no sheath. Intracellular