Pre-sowing seed treatment by cold plasma and electromagnetic field stimulates on trichome formation on Picea abies needles

Abstract

Norway spruce is subject to increasing concerns about forest decline. That underlies the need to develop novel technologies that could lead to improved seedling performance and resistance. Seed treatment by electromagnetic field (EMF) or cold plasma (CP) is recognized as an innovative tool for enhancement of seed germination and early seedling growth. Long time observations have revealed that Norway spruce (Picea abies (L.) Karst.) seed treatments with CP and EMF induce changes in seed germination, stimulate seedling growth and branching, and increase the length of needles. The aim of this study was to estimate the effects of presowing seed treatment with CP and EMF on trichome formation on Norway spruce needles. The obtained results indicate a significant increase of average number of trichomes on a young (current year) needles (by 2.5 times) and older previous year needles (by 1.93 times) developed on seedlings grown from seeds treated by CP for 2 minutes (CP2). Seed treatment by EMF (5 and 10 min) induced later positive effect - the trichome number on young needles was increased by 1,97 and 3,35 times, respectively. However, no significant effects on older needle trichome formation were detected by the used treatments, except CP2. Moreover, CP (5 min) and vacuum had negative effect on trichome formation on young needles - the average number of trichomes decreased by 2.8 and 5 times, respectively. Electron scanning microscopy did not detect any differences in trichome surface structure of treated and control seedling needles. Our data show that seed treatment by CP and EMF may be a promising tool of increasing trichome formation on Picea abies needles. Trichomes are protective structures involved in synthesis and storage of volatile oils and other secondary metabolites. The reported effect may improve plant communication, strengthen stress response and resistance to pests and pathogens.