9 Phosphate Solubilization by Endophytes from the Tropical Plants
217
evaluation, the dry weight of the aerial part (PSPA) and the dry weight of the root
system (PSSR), in the control treatment were higher than those in the other treatments. Among the treatments inoculated with endophytic strains, the T1 treatment
(EPM2- Serratia marcescens) exhibited significantly higher values for all growth
parameters in comparison to other treatments (Unpublished data).
Recently, Mohanty et al. (2017 characterized the endophytic bacteria of J. curcas
and evaluated their plant growth-promoting effect on maize (Zea mays L.). Fifteen
isolates were sequenced by their 16S rRNA genes and characterized based on
their carbon source utilization and plant growth-promoting activities. The main
genera found were Brevibacillus, Paenibacillus, Rhizobium, and Sphingomonas.
These strains preferred to grow on methanol, ethanol, glucose, fructose, sucrose,
and gelatin and these strains exhibited catalase, nitrate reductase, ACC deaminase,
and phosphatase activities. All isolates were positive for phosphate and IAA production. Inoculation of the endophytic strains on maize seeds significantly increased the
shoot and root length of seedlings compared with those of noninoculated seedlings.
Potassium solubilization is important for K-assimilation. The phosphatase activity
of endophytic bacteria and its relationship to plant growth promotion is interesting.
The authors presumed P-mineralization in the rhizosphere by the enzymatic reaction
carried by root-tissue exudates containing phosphatases, was also postulated.
9.4.3 Plant Growth-Promoting Potential of Phosphate
Solubilization by Endophytic Bacteria Isolated
from Tropical Mangrove Forests
Mangroves are typical tropical ecosystems situated between the land and the sea.
These biological communities are frequently found in tropical and subtropical areas
and occupy approximately 18.1 million hectares of the planet. These ecosystems
demand high nutrient availability at the start of the trophic chain, which confers high
importance on the activities of microorganisms, such as bacteria, that are responsible
for the processes of degradation and formation of essential compounds and most of
the carbon flow in the sediments of mangrove forests (Holguin et al. 2001). The
adaptation of bacterial species to mangrove conditions indicates a potential source
of biotechnological resources to be explored, including the discovery of new bacterial species that produce organic acids and enzymes that can be used for agriculture
and industry (Dias et al. 2009b). In this scenario, endophytic bacteria are of agronomic interest because these organisms can enhance plant growth and improve plant
nutrition through diverse mechanisms such as phosphorus solubilization (Quecine
et al. 2014; Rukshana-Begum and Tamilselvi 2016).
Gayathri et al. (2010) isolated endophytic bacteria from the healthy leaves of
mangrove species from the Pichavaram mangrove forest in Tamil Nadu, India. In
total, 104 endophytic bacteria only six endophytic isolates showed phosphate solubilization activity. This study demonstrated that mangroves are sources of endophytic
217
evaluation, the dry weight of the aerial part (PSPA) and the dry weight of the root
system (PSSR), in the control treatment were higher than those in the other treatments. Among the treatments inoculated with endophytic strains, the T1 treatment
(EPM2- Serratia marcescens) exhibited significantly higher values for all growth
parameters in comparison to other treatments (Unpublished data).
Recently, Mohanty et al. (2017 characterized the endophytic bacteria of J. curcas
and evaluated their plant growth-promoting effect on maize (Zea mays L.). Fifteen
isolates were sequenced by their 16S rRNA genes and characterized based on
their carbon source utilization and plant growth-promoting activities. The main
genera found were Brevibacillus, Paenibacillus, Rhizobium, and Sphingomonas.
These strains preferred to grow on methanol, ethanol, glucose, fructose, sucrose,
and gelatin and these strains exhibited catalase, nitrate reductase, ACC deaminase,
and phosphatase activities. All isolates were positive for phosphate and IAA production. Inoculation of the endophytic strains on maize seeds significantly increased the
shoot and root length of seedlings compared with those of noninoculated seedlings.
Potassium solubilization is important for K-assimilation. The phosphatase activity
of endophytic bacteria and its relationship to plant growth promotion is interesting.
The authors presumed P-mineralization in the rhizosphere by the enzymatic reaction
carried by root-tissue exudates containing phosphatases, was also postulated.
9.4.3 Plant Growth-Promoting Potential of Phosphate
Solubilization by Endophytic Bacteria Isolated
from Tropical Mangrove Forests
Mangroves are typical tropical ecosystems situated between the land and the sea.
These biological communities are frequently found in tropical and subtropical areas
and occupy approximately 18.1 million hectares of the planet. These ecosystems
demand high nutrient availability at the start of the trophic chain, which confers high
importance on the activities of microorganisms, such as bacteria, that are responsible
for the processes of degradation and formation of essential compounds and most of
the carbon flow in the sediments of mangrove forests (Holguin et al. 2001). The
adaptation of bacterial species to mangrove conditions indicates a potential source
of biotechnological resources to be explored, including the discovery of new bacterial species that produce organic acids and enzymes that can be used for agriculture
and industry (Dias et al. 2009b). In this scenario, endophytic bacteria are of agronomic interest because these organisms can enhance plant growth and improve plant
nutrition through diverse mechanisms such as phosphorus solubilization (Quecine
et al. 2014; Rukshana-Begum and Tamilselvi 2016).
Gayathri et al. (2010) isolated endophytic bacteria from the healthy leaves of
mangrove species from the Pichavaram mangrove forest in Tamil Nadu, India. In
total, 104 endophytic bacteria only six endophytic isolates showed phosphate solubilization activity. This study demonstrated that mangroves are sources of endophytic