Zinc treatments caused significant increases in the
POD activity in all the parts of the radish seedlings,
especially in the roots (Figure 2). Chaoui et al. (1997)
reported an increase in POD activity in bean plants under
zinc toxicity. Significant increase in the activity of POD
was observed in the shoots of 10-day-old B. juncea
seedlings under zinc toxicity (Prasad et al., 1999).
Sharma et al. (2007) also reported that, different
concentrations of Zn-metal treatment decreased the POD
activity in the 7-d-old seedlings of B. juncea L. In plants,
the detoxification of H2O2 has been known to be an
important function of the peroxidases (Asada, 1994). An
increase in POD activity in radish seedlings exposed to
ZnCl2 suggested its role in the detoxification of H2O2.
However, under the conditions which promote the
production of active oxygen species, a concurrent
enhancement in the expression of the genes for the
synthesis of various antioxidant enzymes was obse