Stimulation of Norway spruce sedling growth and branching induced by pre-sowing seed treatment with cold plasma and electromagnetic field

Abstract

Norway spruce (Picea abies (L.) Karst.) is one of the most important forest trees in Europe both due to economic and ecological aspects. In Lithuania it covers 23.4% of total forest lands and is considered as one of the most productive trees. Norway spruce is subject to increasing concerns about forest decline and that underlies the need to develop novel technologies that could lead to improved seedling performance and resistance. Plant seed treatment by electromagnetic fields (EMF) or cold plasma (CP) is recognized as an innovative tool for seed germination enhancement and early seedling growth. The aim of our study was to estimate the effects of pre-sowing treatment of seeds by radio-frequency CP and EMF treatments on Norway spruce germination and seedling growth, and to elucidate possible involvement of reactive oxygen species (ROS) in the molecular mechanism of the induced stress response and signal transduction. The obtained results indicate that pre-sowing treatment of Norway spruce seeds with CP, vacuum, and EMF can effectively improve seed germination and seedling growth. Treatment with CP (7 min) and EMF (5 min) significantly increased (by 8-10%) the germination yield, whereas the effect of CP (5 min) was negative. The majority of treatments accelerated the germination rate significantly, with CP (2 min) treatment being the most effective. Only the CP (7 min) treatment affected the germination rate negatively. Long-term observations revealed that the treatment-induced pattern of seedling growth changes varied with time. In the end of the second vegetation season (17 months from sowing) seedlings grown from CP5 and CP7 treated seeds, characterized by the negative effects on either germination rate or yield, had 50-60% larger height and 40-50% increased branching in comparison to the control seedlings. In contrast, the EMF treatments that positively affected germination, had no effect on seedling growth on a longer time scale.[...]