Aquatic plants have an inherent capacity to counter
ROS via key antioxidant enzymes (Monferrán et al.2009). The superoxide radical (O2
·), is scavenged in
plants by SOD, which converts it to hydrogen peroxide
(H2O2). H2O2 is scavenged directly by CAT, converting
it to water and O2. APX and GPX also scavenge H2O2
indirectly by combining it with antioxidant compounds
such as ascorbate and guaiacol (Rascio and Navari-Izzo
2011). Our study found augmentation of the major enzyme
repertoire in response to Cu. Such augmentation
may be inferred as a beneficial tool to counter ROS and
confer better phytoremedial efficiency. Contradictory results
of induction Ceratophyllum demersum, (Devi and
Prasad 1998) as well as inhibition Pistia stratiotes,
(Upadhyay and Panda 2009) of SOD, CAT, GPx in
Cu excess have been reported in aquatic plants.
Further, induction of enzymes followed by inhibition
was also observed in some Potamogeton pusillus
(Monferrán et al. 2009).