157
phytoremediation, leaves of which can accumulate higher amounts of U when they
were grown on uranium mine tailings. Amending soil with bioagents like AMF
(arbuscular mycorrhizal fungi) and chemicals like phosphate, calcium carbonate,
citric acid, etc. can augment phytoremediation by increasing the bioavailability of U
(Malaviya and Singh 2012). Mycorrhizae are abundant in nature forming root-fungus associations. Three types of mycorrhizae are common, namely, arbuscular
mycorrhizae (AM, formed mainly by herbaceous plants), ectomycorrhizae (ECM,
formed mainly by forest trees) and ericoid mycorrhizas (of plants like the Ericaceae).
Association with arbuscular mycorrhizae provides several benefits to the plant,
including growth, disease resistance, better crop quality, survival and tolerance to
troubled sites. Mycorrhizal association with plant roots modulates functioning of
the plants to grow in distressed sites contaminated with heavy metals like U (ShakerKoohi 2014). Rufyikiri et al. (2002), working on AMF Glomus intraradices with
bacteria Agrobacterium rhizogenes, transformed carrot (Daucus carota) for U
uptake and translocation and found that U hyphae number influenced the U translocation in plant root. In another study with essential
33
P and non-essential
233
U with
carrot introduced with AMF (G. intraradices), Rufyikiri et al. (2004) demonstrated
that translocation of
33
P is much higher than
233
U, suggesting AMF’s efficient segregation mechanisms for non-essential elements such as uranium. Charro and Moyano
(2017), working with
238
U,
232
Th,
226
Ra,
224
Ra and
210
Pb uptake in trees like Quercus
pyrenaica and Quercus ilex rotundifolia of dehesa ecosystem, found that there was
no influence over the transfer factors and radionuclide contents, but concentration
of the metal may affect.
9 Conclusive Remarks
Phytoremediation is a promising technology for restoration of sites contaminated by
radionuclides (in particular uranium) or other toxic metals. Chemistry- and
engineering- based remediation processes have a number of apprehensions for their
higher energy and economic implications. Yet, effective application of plants
depends upon factors like the plant’s ability to uptake the element in relatively high
concentrations without affecting their growth and biomass production. Other
edaphic factors like soil and clay properties, presence of other minerals and organic
matters and availability of the desired elements to the plants are important.
Amendments of soil with organic acids like citric acids have shown considerable
difference in remediation practices by transiently reducing the pH of soil that
improves desorption of soil U. Several plants like C. stagnalis, F. antipyretica, A.
nodiflorum and B. juncea are having the potential for U remediation. Along with
cultivar selection, genetic manipulation of metal transporters, elucidating factors
related to growth and antistress are important areas of research which will help to
apply phytoremediation more decisively. Therefore, comprehensive multidisciplinary research on contamination factors, AMF and associated rhizosphere related
Uranium and Plants: Elemental Translocation and Phytoremediation Approaches
phytoremediation, leaves of which can accumulate higher amounts of U when they
were grown on uranium mine tailings. Amending soil with bioagents like AMF
(arbuscular mycorrhizal fungi) and chemicals like phosphate, calcium carbonate,
citric acid, etc. can augment phytoremediation by increasing the bioavailability of U
(Malaviya and Singh 2012). Mycorrhizae are abundant in nature forming root-fungus associations. Three types of mycorrhizae are common, namely, arbuscular
mycorrhizae (AM, formed mainly by herbaceous plants), ectomycorrhizae (ECM,
formed mainly by forest trees) and ericoid mycorrhizas (of plants like the Ericaceae).
Association with arbuscular mycorrhizae provides several benefits to the plant,
including growth, disease resistance, better crop quality, survival and tolerance to
troubled sites. Mycorrhizal association with plant roots modulates functioning of
the plants to grow in distressed sites contaminated with heavy metals like U (ShakerKoohi 2014). Rufyikiri et al. (2002), working on AMF Glomus intraradices with
bacteria Agrobacterium rhizogenes, transformed carrot (Daucus carota) for U
uptake and translocation and found that U hyphae number influenced the U translocation in plant root. In another study with essential
33
P and non-essential
233
U with
carrot introduced with AMF (G. intraradices), Rufyikiri et al. (2004) demonstrated
that translocation of
33
P is much higher than
233
U, suggesting AMF’s efficient segregation mechanisms for non-essential elements such as uranium. Charro and Moyano
(2017), working with
238
U,
232
Th,
226
Ra,
224
Ra and
210
Pb uptake in trees like Quercus
pyrenaica and Quercus ilex rotundifolia of dehesa ecosystem, found that there was
no influence over the transfer factors and radionuclide contents, but concentration
of the metal may affect.
9 Conclusive Remarks
Phytoremediation is a promising technology for restoration of sites contaminated by
radionuclides (in particular uranium) or other toxic metals. Chemistry- and
engineering- based remediation processes have a number of apprehensions for their
higher energy and economic implications. Yet, effective application of plants
depends upon factors like the plant’s ability to uptake the element in relatively high
concentrations without affecting their growth and biomass production. Other
edaphic factors like soil and clay properties, presence of other minerals and organic
matters and availability of the desired elements to the plants are important.
Amendments of soil with organic acids like citric acids have shown considerable
difference in remediation practices by transiently reducing the pH of soil that
improves desorption of soil U. Several plants like C. stagnalis, F. antipyretica, A.
nodiflorum and B. juncea are having the potential for U remediation. Along with
cultivar selection, genetic manipulation of metal transporters, elucidating factors
related to growth and antistress are important areas of research which will help to
apply phytoremediation more decisively. Therefore, comprehensive multidisciplinary research on contamination factors, AMF and associated rhizosphere related
Uranium and Plants: Elemental Translocation and Phytoremediation Approaches