Agriculture Reference
In-Depth Information
successful plant microbe interactions, the capability to colonize plant habitats is
important. Single bacterial cells can affix to surfaces and, after repeated cell di-
visions and proliferation, dense aggregates are formed which are commonly re-
ferred to as macro colonies or biofilms (Mohammadi and Sohrabi
2012
). Steps of
colonization include attraction, recognition, adherence, invasion (only endophytes
and pathogens), colonization and growth, and several strategies to establish inter-
actions (Nihorimbere et al.
2011
). There is crosstalk between plant roots and soil
microbes. Plants roots initiate crosstalk by producing signals that are recognized by
the microbes, which in turn produce signals that initiate colonization (Berg
2009
).
PGPR reach root surfaces by active motility facilitated by flagella and are guided
by chemotactic responses. This implies that PGPR capability highly depends either
on their abilities to take advantage of a specific environment or on their abilities
to adapt to changing conditions or plant species (Nihorimbere et al.
2011
). Habibi
et al. (
2011
) strongly recommended that use of bio-fertilizers (combined strains) in
addition with organic and chemical fertilizers have resulted in the maximum grain
yield and oil yield in medicinal pumpkin. They revealed that 50 % of required ni-
trogen and phosphorus fertilizers might be replaced by bio and organic fertilizers,
since bio and organic fertilizers improve the efficiency of recommended nitrogen
and phosphorus fertilizers and reduced the cost of chemical fertilizers and also pre-
vent the environment pollution from extensive application of chemical fertilizers.
de Freitas et al. (
1993
) demonstrated that inoculation of beans with
Rhizobium.
leguminosarum
and
Pseudomonas putida
increased the number of nodules and
acetylene reduction activity (ARA) significantly. A significant positive effect on
grain yield and ARA in roots of barley was obtained due to combined inoculation of
nitrogen fixer's
A. lipoferum
,
Arthrobacter mysorens
and the phosphate solubilizing
strain
Agrobacterium radiobacter
by Belimov et al. (
1995
). Radhakrishnan (
1996
)
revealed that inoculation of
Azospirillum
and phosphor-bacteria resulted in higher
root biomass and more bolls in cotton. Findings of Mohammadi (
2010
) showed
that inoculation of bio-fertilizers (PSB +
Trichoderma
fungi) + application of FYM
had a great influence on canola growth, height and grain yield when compared to
control treatment. Findings of Mohammadi et al. (
2011
) showed that application of
bio-fertilizers had a significant effects on nutrient uptake of chickpea combined ap-
plication of Phosphate solubilizing bacteria and
Trichoderma harzianum
produced
the highest leaf P content and grain P content. Capacity of
Bacillus
sp. to produce
organic acid such as gluconic, citric and fumaric acids under P-limiting conditions
may increase the solubility of poorly soluble phosphorus (Mohammadi and Sohrabi
2012
).
Phosphorus Solubilizing/Mobilizing Microorganisms (PSM)
Phosphorous makes about 0.2 % of the plant on dry weight basis. It has distinct role
in plant metabolism which includes cell division, cell development, photosynthesis,
breakdown of sugars, nuclear transport within plants, and transfer of genetic char-
acteristics from one generation to another generation and regulation of metabolic
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