Selenium nanoparticles stimulate growth, physiology, and gene expression to alleviate salt stress in Melissa officinalis

Abstract

Nanoparticles are receiving many interests due to their broad efficiency in mitigating environmental stresses. The purpose of this research was to study the potential of selenium-nanoparticles (Se-NPs) to mitigate the adverse effects of salt stress on growth, physiology, and gene expression of Melissa officinalis. The pot experiment was conducted in a factorial based on completely randomized design (CRD) with three Se-NPs concentrations (0, 50, and 100\xa0mg\xa0L−1) and four salinity levels (0, 50, 100, and 150\xa0mM NaCl). The foliar spray of Se-NPs improved the growth of M. officinalis plants at different salinity concentrations, from which the most effective was 50\xa0mg\xa0L−1. Plant growth decreased by progressing salinity concentration so that the minimum growth was observed at 150\xa0mM NaCl. The Se-NPs improved salt tolerance in M. officinalis by decreasing lipid peroxidation through increased activity of antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX). Furthermore, exposure to Se-NPs enhanced the transcript levels of phenylalanine ammonia-lyase and rosmarinic acid (RA) synthase genes in lemon balm plants under salt conditions. Plants treated with 100\xa0mg\xa0L−1 Se-NPs at non-saline conditions revealed the highest RA accumulation. According to the findings, we suggest both 100\xa0mg\xa0L−1 Se-NPs to alleviate the adverse effects of salinity on in the M. officinalis, as well as the biosynthesis pathway of RA as a valuable secondary metabolite.