frequency of the micronuclei in the peripheral root tip cells, because As is one of the
well-known inducers of chromosomal and chromatid aberrations (Colognato et al.
2007; Duquesnoy et al. 2010). As-induced genotoxic effects in affected plant tissues
were caused by reductions in telomere length and inhibition in DNA repair processes
and nucleotide excision repair and base excision repair (Faita et al. 2013). Numerous
researches on the denature of normal RAPD results might be linked to the events of
DNA damage, e.g., point mutation or chromosomal reorganization induced by
genotoxic elements (Atienzar et al. 1999, 2000). Similarly, Ahmad et al. (Schulz
et al. 2008) has shown that the frequency of RAPD band loss increased with rising
concentrations and durations of As exposure in Oryza sativa seedlings. The changes
found in the RAPD banding patterns of As-affected plant tissues could be observed
as changes in genomic template stability, possibly related to modifications in both
physiological and biochemical characteristics (Cenkci et al. 2010; Adhikari and Pal
2015; Körpe and Aras 2011).
6.1 Mitigation of Arsenic Accumulation in Rice
Human exposure to As through rice intake is a global health concern. There is a
crucial need to remediate As-contaminated paddy soils and to screen for low As
accumulating rice varieties, so that As contamination can be limited. The above
review explains about the number of agronomic, physicochemical, and different
biological methods, which can lower the As contamination in paddy growing area.
Different studies explained about other alternate water irrigation practice that will
bring down the As contamination in rice grains. Silicon (Si) application in
As-affected paddy growing soil will limit the uptake of AS III. Redox-sensitive
element (i.e., Fe and Mn) supplementation and the biochar (BC) assimilation can
immobilize As in the rice growing area (Fig. 12.1). Introduction of different
microbes is another in-situ method to reduce As content in rice grains. Alteration
of gene expression in rice plants will also reduce the accumulation of As in paddy
grains. Biogeochemical cycle of the rice agroecosystem, availability of sources,
water management policies, and cost involved in the practice will play a major
role in As mitigation process (Kumarathilaka et al. 2019).
A multifaceted and interdisciplinary understanding of As biogeochemistry in
paddy agroecosystems and the mechanisms in As metabolism in rice plants is
important to ensure low As levels in the rice soil solution and rice tissues. Water
management, physicochemical and biological methods, or combinations of these
methods can be successfully adapted to decrease inorganic and methylated As
species content in rice agroecosystems (Fig. 12.2). Even though each technique
has its limitations, the advantages far outweigh the disadvantages (Kumarathilaka
et al. 2019).
In terms of biological approaches, the rate of microbial-driven As III oxidation
and As volatilization in As-contaminated paddy environments needs to be increased
to utilize the eco-friendly approach in a sustainable manner. It is essential to identify
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P. Narayanasamy and R. K. Subramanian
well-known inducers of chromosomal and chromatid aberrations (Colognato et al.
2007; Duquesnoy et al. 2010). As-induced genotoxic effects in affected plant tissues
were caused by reductions in telomere length and inhibition in DNA repair processes
and nucleotide excision repair and base excision repair (Faita et al. 2013). Numerous
researches on the denature of normal RAPD results might be linked to the events of
DNA damage, e.g., point mutation or chromosomal reorganization induced by
genotoxic elements (Atienzar et al. 1999, 2000). Similarly, Ahmad et al. (Schulz
et al. 2008) has shown that the frequency of RAPD band loss increased with rising
concentrations and durations of As exposure in Oryza sativa seedlings. The changes
found in the RAPD banding patterns of As-affected plant tissues could be observed
as changes in genomic template stability, possibly related to modifications in both
physiological and biochemical characteristics (Cenkci et al. 2010; Adhikari and Pal
2015; Körpe and Aras 2011).
6.1 Mitigation of Arsenic Accumulation in Rice
Human exposure to As through rice intake is a global health concern. There is a
crucial need to remediate As-contaminated paddy soils and to screen for low As
accumulating rice varieties, so that As contamination can be limited. The above
review explains about the number of agronomic, physicochemical, and different
biological methods, which can lower the As contamination in paddy growing area.
Different studies explained about other alternate water irrigation practice that will
bring down the As contamination in rice grains. Silicon (Si) application in
As-affected paddy growing soil will limit the uptake of AS III. Redox-sensitive
element (i.e., Fe and Mn) supplementation and the biochar (BC) assimilation can
immobilize As in the rice growing area (Fig. 12.1). Introduction of different
microbes is another in-situ method to reduce As content in rice grains. Alteration
of gene expression in rice plants will also reduce the accumulation of As in paddy
grains. Biogeochemical cycle of the rice agroecosystem, availability of sources,
water management policies, and cost involved in the practice will play a major
role in As mitigation process (Kumarathilaka et al. 2019).
A multifaceted and interdisciplinary understanding of As biogeochemistry in
paddy agroecosystems and the mechanisms in As metabolism in rice plants is
important to ensure low As levels in the rice soil solution and rice tissues. Water
management, physicochemical and biological methods, or combinations of these
methods can be successfully adapted to decrease inorganic and methylated As
species content in rice agroecosystems (Fig. 12.2). Even though each technique
has its limitations, the advantages far outweigh the disadvantages (Kumarathilaka
et al. 2019).
In terms of biological approaches, the rate of microbial-driven As III oxidation
and As volatilization in As-contaminated paddy environments needs to be increased
to utilize the eco-friendly approach in a sustainable manner. It is essential to identify
246
P. Narayanasamy and R. K. Subramanian