AMELIORATION OF NICKEL TOXICITY IN SOYBEAN PLANTS BY GIBBERELLIN AND ASCORBIC ACID

The interactive effects of nickel (Ni) and ascorbic acid (AsA) and gibberellin (GA3) on soybean seedlings (Glycine max L. cv. Union × Elf) were examined. Seven-day old hydroponically-grown seedlings were exposed to NiCl2, 6H2O (0.5 mM), either with or without AsA (1 mM) or GA3 (0.05 mM) or AsA (1 mM) plus GA3 (0.05 mM), for five days. Nickel toxicity symptoms, such as formation of reddish-brown mottled spots on the leaf blade, observed in Ni-treated plants. Addition of GA3 or AsA to the culture medium reduced toxic effects of nickel. Interestingly, with application of GA3 plus AsA, these symptoms did not appear in Ni-stressed plants. Ni decreased dry weights of both roots and shoots and reduced chlorophyll content in leaves. An enhanced level of malondialdehyde and changes in the activities of the antioxidant enzymes, catalase (CAT, EC 1.11.1.6) and guaiacol peroxidase (GPX, EC 1.11.1.7), in both roots and leaves indicated that Ni caused oxidative stress in soybean plants.