Exogenous hydrogen peroxide increases dry matter production, mineral content and level of osmotic solutes in young maize leaves and alleviates deleterious effects of copper stress.

Background: The effects of exogenously applied HO on growth, water status, the mineral ion content (Na, K, Ca, Mg and Cu), proline, total sugars and soluble proteins were assessed in leaves of maize (Zea mays L.) cultivars, Akpinar and Pegaso exposed to excess copper (0.5 mM). Seedlings were grown in equal-sizes plastic pots and irrigated with Hoagland nutrient solution containing HO or/and copper. Different treatments taken for pot experiments were named as the control (C), HO treatment only (HO), excess Cu (Cu) and, Cu stress combined with HO pretreatment (Cu + HO).

Results: Treatment of HO caused the increases in growth, water content, mineral concentration, proline, total sugar and soluble protein contents compared to the control groups in the leaves of both cultivars. Yet excess copper caused reductions in the growth, leaf water potential, Na, K, Ca, Mg concentrations and soluble protein levels but increases in proline, total soluble sugars and Cu contents compared to the control group. Dry matter, leaf water potential and mineral content of Cu + HO group revealed a lower decrease than Cu group ones. A higher increase was also observed in proline and total sugar contents of Cu + HO group than Cu group ones in both cultivars.

Conclusions: These data revealed that exogenous HO might increase the dry matter production and the mineral ion distribution in maize seedlings. Moreover, osmotic regulation might be involved in alleviation of copper toxicity of maize leaves by pretreatment of HO.