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A. Dahiya et al.
readily taken up through the stems of cut flowers, subsequently delaying flower
senescence by several days (Ali et al. 2012). The endophytic bacterium B. megaterium NMp082 isolated from root nodules of Medicago polymorpha reported to
exhibit ACC deaminase activity in vitro and its inoculation promoted growth in
M. polymorpha, Medicago lupulina, Medicago truncatula, and Medicago sativa. B.
megaterium NMp082 also induced tolerance to salt stress in alfalfa and Arabidopsis
plants (Chinnaswamy et al. 2018).
3.6.5 Metals Solubilization by Endophytes
Soil contamination with heavy metals due to anthropogenic activities such as mining,
combustion of fossil fuel, agrochemicals, and sewage sludge has become one of
the most severe environmental hazards throughout the world. Interactions between
plants and beneficial microorganisms have received much attention worldwide for the
bioremediation and phytoremediation of polluted sites as a cleaning technology for
removing metals from soils. Pereira and Castro (2014) isolated distinctive microbial
communities from woody tree species to herbaceous crop plants, which showed
predominant existence in all higher plants (Luo et al. 2011) and able to colonize
different plant compartments such as roots, stem, leaves, flowers as well as fruits
and seeds (Compant et al. 2011; Sun et al. 2010). These endophytes may act as
bioinoculants in the recovery of metal contaminated soils, constituting a biological
alternative to improve phytoremediation efficiency.
Several bacterial endophytes were isolated from the Zn/Cd hyperaccumulator
plant Sedum plumbizincicola (Ma et al. 2015; Ullah et al. 2015). On the other hand, the
effect of the rhizobial endosymbiont Sinorhizobium meliloti strain CCNWSX0020
under copper stress was recently evaluated (Kong et al. 2015). This strain increased
both plant growth and nitrogen content. Besides, the rhizobial symbiosis promoted
Cu accumulation in plant shoots and roots. Also, several plant genes involved in
antioxidant responses were upregulated in plants treated with the bacterium in the
presence of high levels of Cu. Thus, the symbiosis with S. meliloti not only enhanced
plant growth and metal uptake but also induced the plant’s antioxidative defense
responses under Cu stress.
Verma et al. (2014) isolated endophytic bacteria Delftia and Micrococcus from
wheat and six percent isolates showed the highest potassium (K) solubilization, i.e.,
some other bacterial genera such as Stenotrophomonas maltophilia and IARI-IIWP27 Pseudomonas monteilii also showed significant K-solubilization. Wagh et al.
(2016) found that two endophytic microorganisms Hs (pJNK5) and Hs (pJNK6) of
species H. seropedicae that showed K-solubilization on Aleksandrov agar plates.
A. Dahiya et al.
readily taken up through the stems of cut flowers, subsequently delaying flower
senescence by several days (Ali et al. 2012). The endophytic bacterium B. megaterium NMp082 isolated from root nodules of Medicago polymorpha reported to
exhibit ACC deaminase activity in vitro and its inoculation promoted growth in
M. polymorpha, Medicago lupulina, Medicago truncatula, and Medicago sativa. B.
megaterium NMp082 also induced tolerance to salt stress in alfalfa and Arabidopsis
plants (Chinnaswamy et al. 2018).
3.6.5 Metals Solubilization by Endophytes
Soil contamination with heavy metals due to anthropogenic activities such as mining,
combustion of fossil fuel, agrochemicals, and sewage sludge has become one of
the most severe environmental hazards throughout the world. Interactions between
plants and beneficial microorganisms have received much attention worldwide for the
bioremediation and phytoremediation of polluted sites as a cleaning technology for
removing metals from soils. Pereira and Castro (2014) isolated distinctive microbial
communities from woody tree species to herbaceous crop plants, which showed
predominant existence in all higher plants (Luo et al. 2011) and able to colonize
different plant compartments such as roots, stem, leaves, flowers as well as fruits
and seeds (Compant et al. 2011; Sun et al. 2010). These endophytes may act as
bioinoculants in the recovery of metal contaminated soils, constituting a biological
alternative to improve phytoremediation efficiency.
Several bacterial endophytes were isolated from the Zn/Cd hyperaccumulator
plant Sedum plumbizincicola (Ma et al. 2015; Ullah et al. 2015). On the other hand, the
effect of the rhizobial endosymbiont Sinorhizobium meliloti strain CCNWSX0020
under copper stress was recently evaluated (Kong et al. 2015). This strain increased
both plant growth and nitrogen content. Besides, the rhizobial symbiosis promoted
Cu accumulation in plant shoots and roots. Also, several plant genes involved in
antioxidant responses were upregulated in plants treated with the bacterium in the
presence of high levels of Cu. Thus, the symbiosis with S. meliloti not only enhanced
plant growth and metal uptake but also induced the plant’s antioxidative defense
responses under Cu stress.
Verma et al. (2014) isolated endophytic bacteria Delftia and Micrococcus from
wheat and six percent isolates showed the highest potassium (K) solubilization, i.e.,
some other bacterial genera such as Stenotrophomonas maltophilia and IARI-IIWP27 Pseudomonas monteilii also showed significant K-solubilization. Wagh et al.
(2016) found that two endophytic microorganisms Hs (pJNK5) and Hs (pJNK6) of
species H. seropedicae that showed K-solubilization on Aleksandrov agar plates.