The effects of magnetic treatment of irrigation water on seedling growth, photosynthetic capacity and nutrient contents of Populus × euramericana ‘Neva’ under NaCl stress

Abstract

The use of saline water in irrigation is cause for concern due to the reduced availability of fresh water resources for agroforestry in some regions; however, salinity can negatively affect plant populations, such as Populus. Here, magnetic techniques were employed to investigate their effects on improving salinity tolerance in Populus. Irrigation experiments were performed with Populus applying magnetized water (MW) and non-magnetized water (NMW), and seedling growth and development in 1-year-old potted seedlings of Populus × euramericana ‘Neva’ were evaluated under saline conditions. A magnetic treatment device with a low-intensity magnetic field was used for the management of irrigation water. Two average salinity levels, 0 and 4.0 g L−1 of NaCl, were used with MW and NMW, yielding four treatments of irrigation water. The experiments were performed according to a single-factor randomized block design. Seedling growth; the biomass of leaves, roots and stems; photosynthetic parameters and nutrient contents were measured. The results showed that, compared with the non-magnetic treatment (NMT), magnetic treatment (MT) led to improvements in seedling height, basal diameter, leaf area and biomass of leaves and roots (but not stem biomass). Net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and water use efficiency were increased in MT, whereas both transpiration rate and stomatal limiting value were decreased in MT compared with those in NMT. In addition, MT promoted root development, as evidenced by improvements in the length, surface area, mean diameter, volume and tips of the roots. The microelement contents analyses indicated that MT led to higher contents of Fe, Zn and Cu in leaves and roots and a lower content of Mn. MT led to increased contents of C and P and an increased C/N ratio in leaves but a decreased N content; in the roots, the C content and the ratios of C/N and C/P were increased. These results indicated that irrigation with MW appeared to promote seedling growth, root development, photosynthesis and mineral nutrient contents. The properties of saline water were improved by MT, indicating that MT-treated saline water can be used for irrigation.