125
Plant-Microbe Associations
field experiments have been rare (Glick, 2010; Guo & Chi, 2014; Kidd et al.,
2017; Muratova et al., 2003a; Ren et al., 2019).
Rhizobacteria colonize the roots’ surface while endophytic bacteria colonize the inner surface of stem without harming the plant, and both of the
microorganisms are susceptible to biotic and abiotic factors. Another advantage of endophytes is that microorganisms are able to degrade the organic
pollutants commonly widespread in endophytic populations. Endophytes
can reduce the pollutants’ phytotoxicity and the evaporation of volatile
organic compounds (Shehzadi et al., 2014). Since endophytes are present
inside the plant, they can interact more closely with the host plant in comparison with rhizobacteria. Before entering to plant, endophytes have to settle
in rhizosphere and to attach to root surface. Organic compounds, i.e., root
exudates, act as signals for the chemotactic movement of bacteria. During
the transition from the plant rhizosphere to the endosphere, colonizing bacteria have to be able to quickly adapt to very different environment, i.e., pH,
osmotic pressure, carbon source, and oxygen availability. They also have to
overcome the plant’s protective response to invasion, that is, the reactive oxygen species production, which causes stress for invasive bacteria. The important advantage of applying the endophytic degraders in phytoremediation
technology is that any toxic xenobiotic absorbed by the plant can decompose
inside the plant, thereby reducing the phytotoxic effect and eliminating any
toxic effects on the herbivorous fauna living in or near contaminated sites
(Ryan et al., 2008).
7.1.1 Endophytic Bacteria
Endophytic bacteria were first used to clean soil contaminated with organochloride herbicide 2,4-dichlorophenoxyacetic acid (Germaine et al., 2006).
They reduced the accumulation of organic compounds in plant tissues and
transpiration value. The improved degradation of pollutants was correlated
with increasing the quantity of bacteria which were able to decompose pollutants in the plants. Woody plants: poplar and willow have been used to clean
soil contaminated with various organic chemicals (Newman & Reynolds,
2005); inoculation of these plants with endophytic bacteria enhanced plant
growth and degradation of various organic compounds. The partnership of
different plant species and endophytes has been studied (Afzal et al., 2012;
Germaine et al., 2006; Kang et al., 2012; Wang et al., 2010; Weyens et al., 2009;
Yousaf et al., 2011), i.e., willow and Burkholderia sp. HU001, Pseudomonas sp.
HU002 for Cd accumulation; poplar and Enterobacter sp. PDN3; multiflorum
chaff (L. multiflorum var. Taurus) and Pseudomonas sp. ITRI53, Pseudomonas
sp. MixRI75 with hydrocarbon degradation; multiflorum chaff (L. multiflorum var. Taurus), horned chaff (L. corniculatus var. Leo), alfalfa (M. sativa var.
Harpe) and Enterobacter ludwigii with hydrocarbon degradation; poplar and
Pseudomonas putida W619-TCE; lupine yellow and Bacillus cepacia VM1468;
corn and wheat and Burkholderia cepacia FX2; peas (Pisum sativum) and
Pseudomonas putida; wheat (Triticum sp.) and corn (Z. mays) and Enterobacter sp.
Plant-Microbe Associations
field experiments have been rare (Glick, 2010; Guo & Chi, 2014; Kidd et al.,
2017; Muratova et al., 2003a; Ren et al., 2019).
Rhizobacteria colonize the roots’ surface while endophytic bacteria colonize the inner surface of stem without harming the plant, and both of the
microorganisms are susceptible to biotic and abiotic factors. Another advantage of endophytes is that microorganisms are able to degrade the organic
pollutants commonly widespread in endophytic populations. Endophytes
can reduce the pollutants’ phytotoxicity and the evaporation of volatile
organic compounds (Shehzadi et al., 2014). Since endophytes are present
inside the plant, they can interact more closely with the host plant in comparison with rhizobacteria. Before entering to plant, endophytes have to settle
in rhizosphere and to attach to root surface. Organic compounds, i.e., root
exudates, act as signals for the chemotactic movement of bacteria. During
the transition from the plant rhizosphere to the endosphere, colonizing bacteria have to be able to quickly adapt to very different environment, i.e., pH,
osmotic pressure, carbon source, and oxygen availability. They also have to
overcome the plant’s protective response to invasion, that is, the reactive oxygen species production, which causes stress for invasive bacteria. The important advantage of applying the endophytic degraders in phytoremediation
technology is that any toxic xenobiotic absorbed by the plant can decompose
inside the plant, thereby reducing the phytotoxic effect and eliminating any
toxic effects on the herbivorous fauna living in or near contaminated sites
(Ryan et al., 2008).
7.1.1 Endophytic Bacteria
Endophytic bacteria were first used to clean soil contaminated with organochloride herbicide 2,4-dichlorophenoxyacetic acid (Germaine et al., 2006).
They reduced the accumulation of organic compounds in plant tissues and
transpiration value. The improved degradation of pollutants was correlated
with increasing the quantity of bacteria which were able to decompose pollutants in the plants. Woody plants: poplar and willow have been used to clean
soil contaminated with various organic chemicals (Newman & Reynolds,
2005); inoculation of these plants with endophytic bacteria enhanced plant
growth and degradation of various organic compounds. The partnership of
different plant species and endophytes has been studied (Afzal et al., 2012;
Germaine et al., 2006; Kang et al., 2012; Wang et al., 2010; Weyens et al., 2009;
Yousaf et al., 2011), i.e., willow and Burkholderia sp. HU001, Pseudomonas sp.
HU002 for Cd accumulation; poplar and Enterobacter sp. PDN3; multiflorum
chaff (L. multiflorum var. Taurus) and Pseudomonas sp. ITRI53, Pseudomonas
sp. MixRI75 with hydrocarbon degradation; multiflorum chaff (L. multiflorum var. Taurus), horned chaff (L. corniculatus var. Leo), alfalfa (M. sativa var.
Harpe) and Enterobacter ludwigii with hydrocarbon degradation; poplar and
Pseudomonas putida W619-TCE; lupine yellow and Bacillus cepacia VM1468;
corn and wheat and Burkholderia cepacia FX2; peas (Pisum sativum) and
Pseudomonas putida; wheat (Triticum sp.) and corn (Z. mays) and Enterobacter sp.