plant surface microbiology.pdf

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Galdino Andrade
Fig. 9. Bacteria colonising mycelia of Glomus clarum in the hyphosphere of maize plants
grown under axenic conditions in 1 % water-agar. Bacteria did not colonise maize roots,
colonies were observed only around mycelia (x40). BC Bacteria colonies, H hyphae, R
root
the A. globiformis population present in bulk soil, in the rhizosphere and
hyphosphere were similar, but that present in the mycorrhizosphere was
larger. A. eutrphus was dependent on the presence of G. mosseae in the soil,
indicating that even in soil some bacteria may depend on MA-excreted
metabolic products.
These results show that the MA-plant system is very complex and the influence
of these microorganisms is fundamental for the regulation of the biogeochemical
cycles in the rhizosphere system. On the other hand, the
microorganisms of other cycles also influenced the mycorrhizal activity and
root infection with direct consequences on the plant growth and soil fertility.
In degraded areas of tropical regions, the soil is compacted displaying minimum
aeration and draining capacity, aluminium and manganese toxicity
and low fertility indices especially for nitrogen, phosphorus and organic matter.
In these areas, the re-vegetation process is directly related to the interaction
between the plant roots and the functional microorganism groups. The
pioneer plants are the first to colonise these low fertility areas, and they are
very dependent on AM for phosphorus. The pioneer plants in this process are
r strategists which improve the physicochemical characteristics of the soil
and fertility levels with time, allowing other groups of more demanding