The hypaphorine concentration in Pisolithus tinctorius
Coker & Couch hyphae colonizing Eucalyptus roots was 3
to 5 times higher than in adjacent parts of the fungal colony. This phenomenon,
observed 24 h after inoculation,
was also recorded in several-month-old, well-established ectomycorrhizas.
Accumulation was controlled by
specific root-derived diffusible molecules: it can be induced through a
membrane, but not by non-host plants. In
pure culture, high hypaphorine concentration was found only in the youngest
mycelium, i.e. the outer 2 mm of
the colony. Fungal hypaphorine had no IAA-like activity on Eucalyptus
root development and therefore could not
be considered as an auxin analogue; instead, a strong reduction of root hair
elongation was recorded.