Ameliorative effect of exogenously applied oxalic acid on nickel heavy metal induced stress in zea mays

Oxalic acid (ethanedioic acid: OA) is the simplest organic acid occurring naturally in plants. It functions as a chelator of metals. The effects of the exogenous application of OA (1000 μM) on maize plants’ (Zea mays) growth parameters and superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), reduced glutathione (GSH) and lipid peroxide contents were evaluated in the presence or absence of nickel (Ni) induced stress. The plants were treated with 200 μM and 400 μM of nickel sulphate (NiSO4) solution. At the end of the 29-day treatment period, OA enhanced SOD, GSH and catalase activity. The level of lipid peroxidation as determined by TBARS (thiobarbiturate reactive species) was decreased significantly. OA improved the growth parameters of maize plants under nickel induced stress (that is: the root length, root fresh weight and root dry weight all were increased compared to the control). This is a clear indication that OA ameliorates heavy metal stress in maize via biochemical pathways in which it acts as an important chelator and detoxifier of nickel. It thereby depletes the pool of Ni available for the production of free radicals.