Interactive effects of gibberellin A(3) and ascorbic acid on lipid peroxidation and antioxidant enzyme activities in Glycine max seedlings under nickel stress

The effects of nickel in combination with ascorbic acid (AsA) and gibberellin on 7-day-old soybean seedlings were examined. Exposure to 0.25 mM NiCl2 x 6H(2)O for 5 days resulted in toxicity symptoms, such as formation of reddish-brown mottled spots on the leaf blade. Addition of 0.05 mM GA(3) or 1 mM AsA reduced toxic effects of nickel. After their simultaneous application, these symptoms did not appear. Ni decreased dry weights of roots and shoots and reduced chlorophyll content in leaves. An enhanced level of lipoxygenase activity and malondialdehyde, and changes in the activities of the antioxidant enzymes, catalase, guaiacol peroxidase and ascorbate peroxidase, in both roots and leaves indicated that Ni caused an oxidative stress in soybean plants. The Ni-stressed seedlings exposed to AsA or GA(3), especially to GA(3) plus AsA, exhibited an improved growth as compared to Ni-treated plants. GA(3) decreased Ni uptake by roots, while ascorbic acid considerably reduced root-to-shoot translocation of Ni. Interaction of AsA plus GA(3) prevented the decrease in chlorophyll content and lipid peroxidation as well as increased the activities of the antioxidant enzymes. These results suggest that GA(3) plus AsA treatment counteracts the negative effects of Ni on soybean seedlings.