The present study indicates that the microbial community
inhabiting rye roots consists of microorganisms originating from the
interior of the grain only (PSSG) or those coming from the interior as
well as from the surface of the grains (PNSG). Differences in the
number of microbes between PSSG and PNSG may be explained by
various antagonistic interactions between the microorganisms
originating from the interior and from the surface of the grains. In
the PSSG medium, endophytes were the only microorganisms
observed, and their proliferation and migration from the grain
interior to the medium and roots were not limited by interactions
with microbes originating from the grain surface. However, the
higher number of microbes on the root surface found in the PNSG
medium could be a result of a faster and more efficient use of the
nutrients released by plant roots. The PNSG community of microorganisms
was more strongly bound to the root surface than PSSG.
These two populations differed significantly in the ways they
affected plant growth, export of plant and microbial metabolites to
growth medium, total amount of Cd immobilized by plant roots, and
distribution between its operational fractions obtained by sequential
extraction. Elimination of the microbial community from the
grain surface significantly decreased the stability of Cd immobilized
by PSSG plants and decreased the fresh and dry weight of the plants.
The low translocation index and the large root system of PNSG as
well as its specific pattern of Cd distribution between operational
fractions extracted from roots clearly indicate that rye,with roots
colonized by a dense fungal and bacterial rhizosphere community,
can be taken into consideration as a plant for phytostabilization of
Cd-contaminated soils.