اثر ژيبرلين و اسكوربيك اسيد بر كاهش سميت نيكل در گياه سويا

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 (Glyeine mar L. cv. Union x Elf) were examined. Seven-day old hydroponically-grown seedlings were exposed to NiCI2, 6H20 (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 1.1 1.1.6) and guaiacol peroxidase (GPX, EC I.11.1.7), in both roots and leaves indicated that Ni caused oxidative stress in soybean plants. The Ni-stressed seedlings that exposed to AsA or GA3, especially both GA3 plus AsA, exhibited much better growth, when compared to those of other Ni-treated plants. Interaction of AsA plus GA, prevented the decrease in chlorophyll content and lipid peroxidation as well as increased the activities of CAT and GPX enzymes. These results suggest that GA; plus AsA treatment causes a decrease in the negative effects of heavy metal damage in soybean seedlings.