CARVALHO, L.M., CAÇADOR, I. & MARTINS-LOUÇÃO, M.A.
Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa. Campo Grande Bloco C2, Piso 4, 1700 Lisboa, PORTUGAL.
This work is part of a larger project intending to understand
wheter AM associations represent important keys on the adaptative strategies
of plants colonizing salt marshes in a highly polluted estuary. Salt marshes
are complex ecosystems where plants are subjected to a multiple array of stresses
that include flooding, high soil salinity and anoxia. Independently of this
stressful environment, the occurrence of arbuscular mycorrhizas has been reported
in salt marsh plants in several countries but not in Portugal.
In these work two different hypothesis were tested: i) if AM are present in
this ecosystem they are related to particular phenological stages of plant species;
ii) AM fungi constitute isolates particularly adapted to those stressful conditions.
Roots and rhizosphere soil of plant species were collected every 2 months in
the upper and lower marsh zones of a Tagus salt marsh. Soil root zone infectivity
was determined by a soil dilution method and spores were tested for their tolerance
to some factors, namely heavy metals (Cd and Cu) and salinity. It was observed
that only 3 different species were mycorrhizal, Aster tripolium, Inula
crithmoides and at lower level, Puccinellia maritima. Seasonal variation
of the infection degree occurred but they were more connected to the geographical
situation of the plant than to the phenological stage. Low diversity of AM fungi
were found and all of them belong to Glomus genus. It was observed that
AM fungi present a high rate of viability but they also showed a potential adaptation
to salt marsh conditions. This means that they may loose their viability when
grown under non-marsh conditions.