Biomedical Engineering Reference
In-Depth Information
absorb water and nutrients from the soil through their extensive network
of hypha (Hause and Fester 2005).
AM fungi produce different organs including spores and hypha by
which AM fungi can grow and develop. Polymorphism of ribosomal RNA
indicates that AM spores are very variant, suggesting that AM fungi are
heterokaryotic (Hause and Fester 2005). The ecological signifi cance of AM
species, which are also indicated by their spore variation, can be determined
by the structure of plant communities. The responsiveness of AM species
to their host plant differs highly and hence the degree by which they can
enhance plant growth differs among different AM species (van der Heijden
et al. 1998, 2003, Koch et al. 2004, Grunwald et al. 2009).
The other important point about AM fungi is their functional diversity,
which is a rule and not exception. Parameters affecting the functional
diversity of AM species include the phenotypic and genotypic characters
of the fungi and the host plant, as well as the environment they inhabit. In a
symbiotic association, functional diversity of AM species affects host plant
morphology, nutrient balance, the effi ciency of symbiosis as well as the way
the genes are expressed in both symbionts (Feddermann et al. 2010). Such
a property or the existence of functional diversity among AM species can
hence infl uence the ecological signifi cance of AM species. It is because the
above mentioned properties are the most important ones determining the
production effi ciency of ecosystem.
Different approaches have been suggested to determine the ecological
signifi cance of AM symbiosis as the most widespread symbiotic association
including the molecular methods investigating the genetic sequence of AM
fungi and the host plant. However, for the ecological evaluation of AM
symbiosis, just very recently Gamber et al. (2010) suggested evaluating
the genes (Guether et al. 2009) that are activated and expressed during the
protein production in both symbionts.
The amount of AM hypha may range from 54 to 900 kg/ha (Zhu and
Miller 2003), weighing up to 3% of root weight (Jakobsen and Rosendahl
1990). Each cm root may approximately contain 10-100 cm mycorrhizal
hypha (McGonigle and Miller 1999). AM fungi may also produce other
C products accounting for another 3000 kg/ha. For example, AM fungal
production of organic C including glomalin (a heat stable glycoprotein
produced by AM hypha, Sophn and Giani 2010) may be 10-20 times higher
than the microbial biomass (Rillig et al. 2001).
In addition to the growth of fungal hypha into the root cells and onto the
root surface, AM fungi also form hypha with multiplied branched haustoria
structures formed within the cortex cells, called arbuscules, which is the
place of nutrient exchange and also storage organs, called vesicles (hyphal
swellings within the cortex cells with lipids and cytoplasm). Although
