Transgenerational stress memory in E. purpurea: seed treatment with cold plasma and electromagnetic field induces changes in germination, seedling growth and phytohormone pattern in the seeds of second generation

Abstract

Purple coneflower, Echinacea purpurea (L.) Moench, is widely used as medicinal plant and dietary supplement. We investigated the effects of pre-sowing seed treatment with physical stressors – cold plasma (CP, 2-7 min) and electromagnetic field (EMF, 5-15 min) on seed germination and seedling performance. We reported earlier [1] that all applied seed treatments with CP and EMF not only stimulated germination and plant growth in the first year of vegetation but also induced increase in the amounts of biologically active constituents (cichoric acid, vitamin C) and antioxidant activity in leaves of plants (up to 3-fold). In this study, we report also results obtained on the persistency of treatment effects in the second year of plant vegetation, estimated by changes in the morphometric traits of plants and also some inherited traits in the second generation. We observed that in the second year of vegetation the most sustainable positive effects were in short CP treatment (2 min) and EMF treatments (5, 10 and 15 min) groups. Plants grown from CP (2 min) treated seeds had larger number of branches, flowers, and leaves (by 45, 32 and 26%, respectively); larger fresh weight of stems, flowers, and leaves (by 31, 30 and 29%, respectively) in comparison to control. The only effect in plants from all EMF treated groups was larger stem height (from 14 to 26%) and stem weight (from 38 to 49%). The seeds from plants grown from CP- and EMF-treated seeds were collected (second generation seeds, non-treated) and tested in vitro for the germination parameters, early seedling growth and amount of phytohormones in seedlings grown from these seeds. The germination tests in vitro revealed that short time CP and EMF (2 and 5 min, respectively) treatments induced increase in germination rate in the seeds of second generation as compared to control. However, the decrease in germination rate (from 10 to 20%) of longer treatment groups was observed.[...]