Agriculture Reference
In-Depth Information
Table 9.4
Enzyme activity by phosphate-solubilizing bacteria
PSB strains
Phosphatase activity (EU ml
1
)
Phytase activity (EU ml
1
)
PSB1
200
82
PSB6
356
86
PSB9
245
106
PSB10
180
125
PSB14
150
78
PSB15
280
120
PSB16
417
142
Modified from Panhwar et al. (
2012
)
EU
enzyme unit
fungi such as
Aspergillus niger
and
A. ficuum
species being used for the production
of microbial phytases (Pandey et al.
2001
). Some PSB strains capable of producing
phosphatase and phytase are listed in Table
9.4
.
Enzyme activities increase due to the inoculation of PSB. There were two
enzymes, such as phosphatase and phytase, which were found in the roots of aerobic
rice. The PSB inoculation produced higher values of both enzymes as compared to
non-inoculated plants. The highest phosphatase (10.68
g p-NP g
1
root dry
wt ha
1
) activity (Fig.
9.1
) and phytase (25.71 U mg
1
) activity (Fig.
9.2
) were
found following the application of mixtures of PSB, PR, and oxalic acid. In this
study, it was found that the inoculated plants had significantly higher amounts of
phosphatase enzyme. It is known that this enzyme excreted from roots can hydro-
lyze a wide range of organic P compounds in soil and release Pi for plant uptake
(George et al.
2002
). Therefore, increased Pi pool confirmed the role of PSB in
solubilizing P from organic substances.
μ
9.4 Effect of PSB on Nutrient Uptake and Growth
of Aerobic Rice
9.4.1 Phosphorus Uptake by Plants Inoculated with PSB
A number of bacterial species including PSB associated with the plants' rhizo-
sphere are able to exert a beneficial effect on plants growth. Therefore, their use as
biofertilizers or as biocontrol agents in agricultural practices has been the focus of
numerous researchers (Glick
1995
). This group of bacteria has often been termed as
“plant growth-promoting rhizobacteria” (PGPR), and among them are strains
belonging to the genera
Pseudomonas
,
Azospirillum
,
Burkholderia
,
Bacillus
,
Enterobacter
,
Rhizobium
,
Erwinia
,
Serratia
,
Alcaligenes
,
Arthrobacter
,
Acinetobacter
, and
Flavobacterium
(Sharma et al.
2013
; Panhwar et al.
2012
)
which facilitate the growth of plants. Inoculation of PSB and the application of
oxalic acid increased P uptake in aerobic rice (Panhwar et al.
2013
). The lower
