Agriculture Reference
In-Depth Information
Growth
promotion
Sequester
metal ions
Reduces
ROS
Osmoprotection
Ethylene
Ion
translocation
ABA
Protective
compound
Siderophores
IAA
Volatiles
ACC
deaminase
Antioxidants
Cytokinin
SOIL
Toxic compounds
PGPR
Non toxic
Improved texture,
water retention and nutrients
Exopolysaccharide
Fig. 11.2
Stress alleviation modes of PGPR (modified from Yang et al.
2009
).
ABA
abscisic acid,
IAA
indole acetic acid,
ROS
reactive oxygen species
ameliorating metal stress. The siderophores also bind to other metals like Mg, Mn,
and Cr and chelate the solubilized/leached metals (Akhtar et al.
2013
). Siderophore-
producing PGPR can therefore be used to remove toxicants (metals) from metal
polluted soil (Mani et al.
2010
). Along with metal stress, siderophore-producing
rhizobacteria also inhibit the phytopathogen (Kloepper et al.
1980
; Glick
2012
)as
discussed in Sect.
11.3.2.2
.
11.5.1.3 Biotransformation: Conversion of Toxic Forms to Less Toxic
Forms
Microorganisms especially PGPR can help in relieving metal toxicity by
transforming highly toxic metals to less toxic forms or in forms more readily
accessible to plant roots (Khan et al.
2009
). The conversion of metals involves
mainly a change in the valence state of metals, for example, change of organic
selenium to selenate or organo-selenium (Zayed et al.
1998
) which can easily be
taken up by plants. This
feature of PGPR has been well exploited in
