Agriculture Reference
In-Depth Information
Fig. 7.2
A model of phosphate starvation-inducible mps genes (Bagyaraj et al.
2000
)
through ligand exchange reactions (Jones
1998
). Dissociation of calcium phosphate
(Ca-P) results from the combined effects of carboxylic acids synthesis and subse-
quent pH decrease involving common mechanism, but proton release is the out-
come of several mechanisms (Deubel et al.
2000
).
7.4 PSB and Plant Growth Promotion
PSB helps in making the soluble P accessible for uptake by plants and concurrently
promotes the growth of plants promotion of plants by PSMs (Khan et al.
2007
).
Growth promotion can be achieved by production of plant beneficial metabolites,
such as phytohormones, antibiotics, or siderophores; however, there are about or
more than 20 possible mechanisms by which the plant growth promotion can be
mediated (Sharma et al.
2013
). Many reports show that bacteria belonging to genera
Bacillus
,
Pseudomonas
,
Serratia
,
Enterobacter
, etc., solubilize inorganic P and aid
in plant growth promotion (Rodriguez and Fraga
1999
). Use of PSB is reported to
increase crop yields up to 70 % (Verma
1993
).
Pseudomonas
sp. CDB35, for
instance, solubilized P in buffered RP medium (Hameeda et al.
2008
) and, when
tested, promoted overall growth including the biomass index of the maize. It has,
however, been observed that a single PSB strain may not employ several mecha-
nisms at one time; instead simultaneous mechanisms can function in unison and
very efficiently enhance the plant growth. The role of a very few select groups of
PSB in growth promotion of various crops is listed in Table
7.1
(Patil et al.
2002
;
Mehrvarz et al.
2008
).
Single and dual inoculation along with P fertilizer was 30-40 % better than P
fertilizer applied alone in terms of grain yield of wheat. Also, dual inoculation
without P fertilizer improved grain yield up to 20 % against sole P fertilization
