Abstract: A geomagnetic field is a significant factor during the growth and development of trees. Changes in the magnetic field (MF) will result in reactions at the biochemical, molecular, cellular and gene levels. However, it is not clear how a magnetic field affects metabolism and homeostasis under stressful conditions such as salinity. In this study, a novel method was developed of a static magnetic field (SMF) to investigate magnetobiological changes in trees. The results show that pre-treatment of poplar (Populus × euramericana ‘Neva’) cuttings with a static magnetic field significantly mitigated the negative effects of salinity stress on their growth and physiological activities. Biochemical assays revealed that several chemical messengers, including hydrogen peroxide (H₂O₂) and O₂^•−, were significantly improved in roots treated with salt, implying an increase reactive oxygen species. A static magnetic field also significantly increased proline concentrations, soluble protein contents, and CAT and SOD activities. Electrophysiological experiments further revealed that pre-treatment with a static magnetic field remarkably decreased salt-induced Na⁺ influx and H⁺ efflux which control plant salt tolerance. In pharmacological experiments, because the Na⁺/H⁺ correlation was closely related to the SMF-activated plasma membrane and Na⁺ antiporter activity alleviated the massive accumulation of salt-induced reactive oxygen species (ROS) within the roots. In addition, a static magnetic field dramatically increased the transcriptional activity of stress-responsive genes, including PtrRBOHD and PtrHA5. Together, these results indicate that SMF reduced Na⁺ influx by activating Na⁺/H⁺ antiporters and plasma membrane H⁺-ATPase to effectively maintain homeostasis by regulating the reactive oxygen species system and cytoplasmic osmotic potential. Ultimately, these static magnetic field methods improved salt tolerance in poplar cuttings, and, for future research, similar methods could be applied to other plants.

Key words: Poplar, Salt tolerance, Static magnetic field, Plasma membrane Na⁺ transporters, Reactive oxygen species (ROS) homeostasis