Effects of selenium application on physiological parameters of Melissa officinalis L. plants

In this study, the influence of hydroponically applied (0.1, 1 and 10mg l-1) and foliar-applied (10mg l-1) Na2SeO3 on the some physiological characteristics of Melissa officinalis L. was investigated. The results indicated that the root application of 10mg l-1 Se could decrease shoot fresh and dry mass, and caused an improved lipid peroxidation in hydroponically grown lemon balm. Se supply at 10mg l-1 in lemon balm exhibited a significantly positive effect on accumulation of total chlorophyll, and raised the activity of catalase, but these mechanisms could not ameliorate the negative effect of Se toxicity on productivity, as was indicated by a higher malondialdehyde concentration. Our results indicated that for biofortification program with lemon balm, the application of Se as selenate at low concentrations (0.1 and 1mg l-1) would be more beneficial because it favored shoot biomass growth. In contrast, the results from field experiment indicated that foliar-applied Se (10mg l-1) was favorable for biomass accumulation in lemon balm. In this work, the foliar application of selenium induced higher activity of phenylalanine ammonia-lyase as well as the higher total phenol content, which appear to act as protective compounds. It was concluded that foliar applications to lemon balm at 10mg Se l-1 can effectively cause a significantly higher growth rate, improve Se content and phenolic compounds.