| Hg is a toxic heavy metal element, it causes serious damage to human health, plant growth and development. Subjected to Hg pollution of soil, most Hg residues in the soil, and composes serious hazards to crops. To explore the trait of Hg damage on crops and provide a rationale for plants protection under Hg stress, this essay researched the effect of Zn and Se with different concentration on some physiological target of wheat seed germination and seedling growth under Hg stress by a sand culture and hydroponic experiment.The main results are listed as following:1. Compared with Hg alone, low concentration of Zn (1020 mg·L-1) treatments promoted the bud and root length of wheat seeds, which peaked at 20 mg·L-1 Zn. In high concentration of Zn (50100 mg·L-1) treatments the promotion disappeared and even showed inhibition. Seed germination rate did not show significant changes under the infusing of Zn.2. The addition of Zn significantly promotedα-amylase activity of wheat seed under Hg stress. And with the Zn concentration increasing, the promoting effect decreased gradually. Protein and CAT activity were restrained after Zn added and with the Zn concentration increasing, the activity decreasing.3. Compared with Hg alone, Se promoted bud and root length of wheat seeds. And with the Se concentration increasing, bud and root length firstly increased and then decreased, peaking at the 15 mg·L-1 Se treatment. Low concentration of Se (510 mg·L-1) can promoted seed germination of wheat under Hg stress while the effect of promoting disappeared under the high concentration of Se (1520 mg·L-1). The addition of Se in general mitigated the toxic of Hg stress on wheat seed.4. In low concentrations of Se (510 mg·L-1) treatment, theα-amylase activity did not show significant changes compared with the treatment of Hg alone. 15 mg·L-1 Se promotedα-amylase activity and made it reach the level of the CK treatment. In 20 mg·L-1 Se treatments, the promoting effect ofα-amylase disappeared. Se restrained the protease activity and with the concentration of Se increaseing protease activity decreasing. CAT activity generally rised compared with the treatment under Hg alone. The activity increased at first and decreased then. The peak appeared at the treatment of 10 mg·L-1 Se.5. The treatments of 1050 mg·L-1 Zn to a certain extent eased the toxicity of Hg on the content of chlorophyll of wheat seedlings. The chlorophyll content increased to the level of the CK treatment. The most obvious alleviating effect occurred on the level with 10 mg·L-1 Zn. With the Zn concentration increasing gradually, the easing effect showed downward trend. When the Zn concentration reached 100 mg·L-1, the chlorophyll content was restrained.6. The Zn added improved the activity of SOD and CAT of wheat seedlings in some extend and this promoting effect increased firstly and decreased then. The most obvious alleviating effect occurred on the level with 20 mg·L-1 Zn. Meanwhile, the Zn added also inhibited the production of MDA and free praline, relieving lipid peroxidation caused by Hg. The most obviously inhibition effect of MDA was at 10 mg·L-1 Zn and the minimum value of free proline content was observed in the treatment of 20 mg·L-1 Zn, which means 1020 mg·L-1 Zn can effectively relieve lipid peroxidation in wheat seedlings caused by Hg stress.7. 515 mg·L-1 Se added eased the inhibition of Hg on the chlorophyll content of wheat seedling and made it reach even exceed the level of CK and in the 5 mg·L-1 Se treatment the alleviative effect was most obviously. With the concentration of Se increasing, the effect of alleviating showed downward trend and while the concentration of Se reached 20 mg·L-1 the chlorophyll content was decreased.8. The addition of Se decreased the MDA and free proline content of wheat seedlings, and alleviated the lipid peroxidation caused by Hg. In the treatment of 5 mg·L-1 Se, the alleviative effect on the MDA was the most obviously and free proline decreased to the lowest point in the treatment of 10 mg·L-1 Se. Low concentration of Se (510 mg·L-1) eased Hg stress on SOD and CAT activity in wheat seedlings while with high concentrations of Se (1520 mg·L-1) the easing effect showed downward trend and even inhibition appeared.
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