4.2 Role of Endophytes
According to Schulz and Boyle (2006) and Lodewyckx et al. (2002), bacteria that
colonize the intimate niche of plant (internal tissues) without any negative effects or
infection to host are called endophytic bacteria. Except seed endophytes, the primary
site to gain entry (or route of colonization) by endophytes into plants is via the roots
which is now confirmed by several microscopic studies (Pan et al. 1997; Germaine
et al. 2004). After getting entrance into the plant, endophyte resides in xylem or root
cortex or transports through the vascular system to colonize the plant systematically
(Mahaffee et al. 1997; Quadt-Hallmann et al. 1997). With interaction to plants,
endophytes get carbohydrates, and in return, they provide resistance to plant from
various abiotic and biotic stresses (Hamilton and Bauerle 2012; Hamilton et al.
2012). Endophytes can alter the structural community of plant (Clay and Holah
1999; Yuan et al. 2011), as well as they regulate the interaction between competitors
and their host plant (Omacini et al. 2001; Clay and Holah 1999; Hyde and Soytong
2008; Guo et al. 2008)
A study of Chen et al. (2010), Shin et al. (2011), and Luo et al. (2011) describes
that many endophytes are being used in phytoremediation because of metal resistance or organic pollutant degradation and plant growth promotion ability.
4.3 Role of Mycorrhiza
For plant growth development, mycorrhizae fulfil its role by providing mineral
nutrients exclusively the uptake of phosphate to the plants (Moose 1972). According
to Bagyaraj (1984), Entry et al. (2002), and Fomina et al. (2005), this effect is
because of several key features of mycorrhiza such as (i) extra radical mycelium
increases the absorbing surface and exploits large soil volume; (ii) hyphal diameter is
small which leads to increase in P-absorbing surface area; (iii) P concentration is low
in mycorrhiza by the formation of polyphosphates (poly P); and (iv) release of P is
catalyzed by the production of phosphatases and organic acids. Hence mycorrhiza
can help in sustainable development of agroecosystem by increasing plant survival
rate and plant nutrients acquisition, and also it helps in increasing carbon and
nitrogen deposition into the soil and reduces plant stress (Almas et al. 2004).
The infection by mycorrhiza helps in the increase of uptake of Pb and Mn by plant
from soil solutions even in low concentrations (Heggo et al. 1990; Malcova and
Gryndler 2003), and thus, they may play crucial role in the phytoremediation of
contaminated site (Liao et al. 2003; Gohre and Paszkowski 2006; Orlowska et al.
2011; Zarei et al. 2010; Chanda et al. 2014). The association formed by
ectomycorrhiza can perform a significant resistance against metallic toxicity in
contaminated soil (Leyval et al. 1997) and petroleum-like compounds (Sarand
et al. 1999) or polycyclic aromatic hydrocarbons (Leyval and Binet 1998).
17 Plant-Microbe Interactions for Bioremediation and Phytoremediation of. . .
429
According to Schulz and Boyle (2006) and Lodewyckx et al. (2002), bacteria that
colonize the intimate niche of plant (internal tissues) without any negative effects or
infection to host are called endophytic bacteria. Except seed endophytes, the primary
site to gain entry (or route of colonization) by endophytes into plants is via the roots
which is now confirmed by several microscopic studies (Pan et al. 1997; Germaine
et al. 2004). After getting entrance into the plant, endophyte resides in xylem or root
cortex or transports through the vascular system to colonize the plant systematically
(Mahaffee et al. 1997; Quadt-Hallmann et al. 1997). With interaction to plants,
endophytes get carbohydrates, and in return, they provide resistance to plant from
various abiotic and biotic stresses (Hamilton and Bauerle 2012; Hamilton et al.
2012). Endophytes can alter the structural community of plant (Clay and Holah
1999; Yuan et al. 2011), as well as they regulate the interaction between competitors
and their host plant (Omacini et al. 2001; Clay and Holah 1999; Hyde and Soytong
2008; Guo et al. 2008)
A study of Chen et al. (2010), Shin et al. (2011), and Luo et al. (2011) describes
that many endophytes are being used in phytoremediation because of metal resistance or organic pollutant degradation and plant growth promotion ability.
4.3 Role of Mycorrhiza
For plant growth development, mycorrhizae fulfil its role by providing mineral
nutrients exclusively the uptake of phosphate to the plants (Moose 1972). According
to Bagyaraj (1984), Entry et al. (2002), and Fomina et al. (2005), this effect is
because of several key features of mycorrhiza such as (i) extra radical mycelium
increases the absorbing surface and exploits large soil volume; (ii) hyphal diameter is
small which leads to increase in P-absorbing surface area; (iii) P concentration is low
in mycorrhiza by the formation of polyphosphates (poly P); and (iv) release of P is
catalyzed by the production of phosphatases and organic acids. Hence mycorrhiza
can help in sustainable development of agroecosystem by increasing plant survival
rate and plant nutrients acquisition, and also it helps in increasing carbon and
nitrogen deposition into the soil and reduces plant stress (Almas et al. 2004).
The infection by mycorrhiza helps in the increase of uptake of Pb and Mn by plant
from soil solutions even in low concentrations (Heggo et al. 1990; Malcova and
Gryndler 2003), and thus, they may play crucial role in the phytoremediation of
contaminated site (Liao et al. 2003; Gohre and Paszkowski 2006; Orlowska et al.
2011; Zarei et al. 2010; Chanda et al. 2014). The association formed by
ectomycorrhiza can perform a significant resistance against metallic toxicity in
contaminated soil (Leyval et al. 1997) and petroleum-like compounds (Sarand
et al. 1999) or polycyclic aromatic hydrocarbons (Leyval and Binet 1998).
17 Plant-Microbe Interactions for Bioremediation and Phytoremediation of. . .
429