Abstract: In order to clarify the regulatory effect of melatonin on the tolerance of wheat (Triticum aestivum L.) under copper (Cu) stress at germination stage, Shangmai 1619 and Xiaoyan 15 were used as experimental materials to determine the changes of seed germination indexes and seedling physiological indexes under different Cu stress intensities (100 and 150 μmol/L) after different concentrations (0, 50, 100 and 1 000 μmol/L) of melatonin priming. The results showed that with the increase of exogenous melatonin, the germination potential, germination rate, bud length, root length, and the activities of superoxide dismutase (SOD) and peroxidase (POD) in the seedings of the two wheat varieties increased first and then decreased, and the malonaldehyde (MDA) content of the seedlings decreased first and then increased. The membership function analysis showed that, under 100 μmol/L Cu²⁺ stress, the comprehensive evaluation value of 100 μmol/L melatonin treatment was the highest, followed by 50 μmol/L melatonin; under 150 μmol/L Cu²⁺ stress, the comprehensive evaluation value of 50 μmol/L melatonin treatment was the highest, followed by 100 μmol/L melatonin. In summary, 50 and 100 μmol/L melatonin had better mitigation effects on relieving Cu stress under 100 and 150 μmol/L in wheat.

Key words: wheat (Triticum aestivum L.), melatonin, Cu stress, germination characteristics, physiological index