Biomedical Engineering Reference
In-Depth Information
most crop plants form AM symbiosis, there are some plant families
(their roots exudates are unfavorable to AM) which are not symbiotic to
AM, including
Brassicaceae
,
Caryophyllaceae
,
Cyperaceae
,
Juncaceae
,
Chenopodiaceae
or
Urticaceae
and
Amaranthaceae
. The root exudates of
non-host plants may include antifungal products such as isothiocyanates.
It may also be due to the fact that non-host plants are not able to produce
the hyphal branching signal molecules, the strigolactones (Schreiner and
Koide 1993, Yoneyama et al. 2008). However, there are limited species in
each family that may form AM symbiosis (Hause and Fester 2005, Cardoso
and Kuyper 2006).
AM fungi are essential components of sustainable agriculture due
to their multi-functional nature indicated in the following: (1) an active
and diverse part of soil microbial community, affecting plant water and
nutrient uptake (chemical properties), especially under nutrient defi cient
conditions, (2) improve soil aggregation and structure through their hypha
(physical properties) and (3) affect soil food network (biological properties)
(Miransari 2011a, b).
AM fungi affect the dynamic of organic and inorganic nutrients
including C cycling. The ability of AM fungi to enhance plant water and
nutrient uptake is among their most important characteristic (Cardoso
and Kuyper 2006, Miransari et al. 2009a, b, 2011b). It is often stated that
the AM-plant symbiosis is non-specifi c. However, different researchers
have indicated that there are different parameters affecting the symbiosis
specifi city including: (1) the interaction between AM fungi and the host
plant, (2) the physiological and morphological differences among the
different species of AM fungi and (3) AM origin (Smith and Smith 1997,
Miransari et al. 2007, 2008).
All the above mentioned activities are controlled by molecular and
signaling communications between AM fungi and the host plants (Seddas
et al. 2009, Dermatsev et al. 2010, Kuznetsova et al. 2010). Some of the signal
molecules, related to the AM-plant symbiosis have been recently recognized
(Akiyama et al. 2005, 2006). For example, strigolactones are among the signal
molecules necessary for the onset of symbiosis between AM fungi and the
host plant. They also act as stimulants for the seed germination of parasitic
weeds and help the weeds fi nd their host plant. In other words, under P
defi cient conditions the host plant exudates strigolcatones attracting AM
fungi and weeds (Akiyama and Hayashi 2006). Plant hormones including
cytokinins, ethylene, abscisic acid (ABA), auxin (indole acetic acid, IAA),
jasmonic acid and salicylic acid can also act as signal molecules during the
process of AM symbiosis.
Evaluation of such signaling and communications between AM fungi
and the host plant can be useful for a more precise understanding of the
