关键词: 镉胁迫, 磁化作用, 抗氧化物质, 抗氧化酶, 内源激素

Abstract: [Objective] Cadmium (Cd) contamination in soil has become a serious worldwide environmental and health problem. Cd is easily taken up by a plant and transported to the above-ground tissues. A potted experiment was carried out to explore the physiological mechanism of cadmium toxicity after magnetization and the way of mitigating cadmium toxicity by magnetization by measuring ascorbate-glutathione cycle and endogenous hormone level in one-year-old seedlings of Populus×euramericana ‘Neva’.[Method] In this study, poplar I-107 (P.×euramericana ‘Neva’) was subjected to different concentrations of Cd(NO₃)₂ stress. The cadmium treatment was implemented by irrigating with half-Hoagland solution containing 0 or 100 mmol·L^-1 Cd(NO₃)₂, with magnetized (MT) or without magnetized treatments (NMT) for 30 days. The effects of magnetization on AsA-GSH cycle and endogenous hormone levels of poplar under exogenous cadmium stress were analyzed by measuring the activities of non-enzymatic antioxidants (AsA, DHA, GSH and GSSG) and key enzymes (APX, GR, MDHAR and DHAR), hydrogen peroxide (H₂O₂), malondialdehyde (MDA) and endogenous hormones in AsA-GSH cycle.[Results] 1) Under Cd stress, the magnetization treatment induced a slightly higher level of AsA in roots than in leaves, resulted in DHA level increased in leaves but decreased in roots, and increased the contents of GSH and GSSG in both roots and leaves. 2) Under Cd stress, magnetization inhibited APX activity in leaves and roots, and GR and MDHAR activity in leaves, but promoted DHAR activity in leaves and GR activity in roots. In addition, the activity of GR, MDHAR and DHAR was increased by 19.37%~284.40% in the poplar by the magnetization in comparison with the NMT control. 3) Under Cd stress, magnetization enhanced Cd enrichment and bio-transport efficiency in leaves and roots, and at the same time insulted in accumulation of hydrogen peroxide and MDA. 4) Under Cd stress, magnetization reduced the levels of IAA, ABA, GA₃ and ZR in leaves by 19.69%~94.88%, and increased the levels of these endogenous hormone in roots. Thus, under Cd stress, AsA was consumed in poplar after magnetization treatment.[Conclusion]GSH and GSSG played an important role in the antioxidant cycle system of AsA-GSH. Roots played a dominant role in the process of scavenging H₂O₂ and MDA by regulating the activities of different antioxidant enzymes and the contents of endogenous hormones, as well as their ratios.

Key words: cadmium stress, magnetization, antioxidant substance, antioxidant enzymes, endogenous hormone