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Fig. 13.3   Possible mechanism of arsenic induced oxidative stress and antioxidant defense system.
(Adopted from Sharma 2012 )
finally sequestration of arsenic in vacuoles (Sharma et al. 2007 ). Increasing activ-
ity of Guaiacol peroxidase, Catalase, Ascorbate peroxidase contributes to high ac-
cumulation of the arsenic species by the plants (Srivastava et al. 2011 ). Similarly,
another non enzymatic antioxidant of glutathione-ascorbate cycle like ascorbate
(AsA) and dehydroascorbate (DAsA), were also analyzed in some plants during
As(V) exposure. As(V) treatment caused an increase in the ratio of AsA/DAsA in
P. vitatta, P. ensiformis, H. verticillata, and O. sativa (Singh et al. 2006 ; Srivastava
et al. 2011 ; Tripathi et al. 2012b ) indicating the significant role of ascorbate in As
induced stress tolerance. Also Requejo and Tena ( 2005 ) confirmed that the level
of these enzyme increased because these are involved in cellular homeostasis for
redox perturbation by the study of proteome analysis in maize roots (Fig. 13.3 ).
Reduction of arsenate to arsenite is catalyzed by enzyme arsenate reductase,
it is also considered as a mechanism involved in detoxification because arsenite
can bind with phytochelatins. Arsenate reduction is coupled to NADP (NADPH)
oxidation via the reduction of oxidized glutathione by glutathione reductase (GR)
and with the resulting glutathione (GSH) serving as the electron donor for arsenate
reductase (Ellis et al. 2006 ).
The activity of arsenate reductase (AR) is well studied in yeast (Rosen 2002 ).
Root extracts from the arsenic hyperaccumulator fern Pteris vittata also show the
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