Effects of Zn on Some Physiological Characteristics of Wheat Seedlings Under Hg Stress

A sand culture experiment was conducted to investigate the effects of zinc(Zn) with different concentration(10~100 mg L-1) on the chlorophyll relative content(SPAD),the accumulation of malondialdehyde(MDA) and proline,and the antioxidant enzyme activities of wheat seedlings under mercury(Hg) stress(10 mg L-1).The results showed that,under the Hg(10 mg L-1) stress treatment alone,the SPAD of wheat seedlings decreased,and both superoxide dismutas(SOD) and catalase(CAT) activities were inhibited,whereas MDA and proline content were increased.When treated together with 10 mg L-1Zn,SPAD increased by 5.6%,MDA levels decreased by 32.4%,indicating that the concentration of Zn to some extent alleviated the toxicity of Hg in wheat seedlings.However,when Zn concentration was higher than 10 mg L-1 SPAD gradually decreased and MDA content significantly increased,suggesting that with the increasing of Zn concentration,Zn alleviation of the toxicity of Hg decreased.Lower concentration of Zn(10~20 mg L-1) promoted the activity of SOD and CAT,which gradually increased with the increasing of Zn concentration.At 20 mg L-1 of Zn,the activities of the two enzymes were increased by 103.3% and 71.0% respectively compared with the Hg treatment alone.Under the higher concentration of Zn(50~100 mg L-1) treatment,the activities of the two enzymes showed downward trends.Within the test concentration,the proline content was lower than that of Hg treatment alone,and less than that of the control,indicating that additional Zn inhibited the formation of proline.In summary,10~20 mg L-1 of Zn eased the wheat seedling poisoning which was caused by Hg at 10 mg L-1 to a certain extent.