THE EFFECT OF ELECTROMAGNETIC PRETREATMENT ON LEMON BALM (MELISSA OFFICINALIS L.) SEEDS SUBJECTED TO STATIC MAGNETIC FIELDS

The effects of magnetic waves as natural environmental factors on the growth and development of plants is not well known. The present study evaluated the effects of a static magnetic field (SMF) (4 and 6mT for 30 and 120 min) on the growth, contents of proline and total soluble sugar, phenolic compounds, accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA) of pretreated seeds. The activity of antioxidant enzymes and the essential oil composition of lemon balm seedlings subjected to SMF treatment (4 and 6mT for 30 and 120 min for 7 days) were also examined. The SMF treatments decreased plant growth by reducing the contents of photosynthetic pigments and inducing oxidative stress; however, pretreated plants had greater contents of pigments, proline, soluble sugars, total phenol and flavonoids than non-pretreated plants. The contents of MDA and H2O2 were decreased in pretreated plants compared to non-pretreated plants; this result was associated with the reduction in antioxidant enzyme activity. The exposure of seeds to SMF also increased the yield and altered the chemical composition of essential oils compared to both non-pretreated and control plants.These results indicate that pretreatment of lemon balm seeds with SMF can be effectively used as a pre-sowing treatment to increase essential oil yield for medical purposes.