Most of the studies have examined how the single addition of either
Cu or Zn affects a variety of plant physiological processes (Jain et al.,
2010; Cambrollé et al., 2012; Mateos-Naranjo et al., 2013). Recently it
has been highlighted that the interaction between the two elements
further affects plant physiology as the antioxidant defense system of
plants (Upadhyay and Panda, 2010).