Effects of foliar application of melatonin on selenium accumulation in medicinal plant Perilla frutescens

Application of melatonin (MT) can promote selenium (Se) uptake in crops. To enhance Se accumulation in the medicinal plant Perilla frutescens, a pot experiment was carried out to investigate the impact of foliar spraying MT on Se uptake in P. frutescens. The root and shoot biomass of P. frutescens were increased by MT to some extent. MT at 150 μmol/L displayed the maximum biomass, which increased the root and shoot biomass by 53.37% and 39.09%, respectively, compared to the control. MT also increased the photosynthetic pigment contents in P. frutescens to a certain extent, while it had no significant effect on the chlorophyll a/b ratio. MT increased the antioxidant enzyme activities and soluble protein content of P. frutescens. In addition, MT at 150 and 200 μmol/L increased the root Se content, shoot Se content, bioconcentration, and translocation factor of P. frutescens, while at 25, 50, and 100 μmol/L had no significant effects on these parameters. Compared to the control, MT at 150 and 200 μmol/L increased the root Se content by 8.95% and 9.36%, respectively, and increased the shoot Se content by 19.35% and 13.85%, respectively. Moreover, root Se content, shoot biomass, chlorophyll a content, and root biomass were closely associated with shoot Se content. Therefore, foliar application of 150 and 200 μmol/L MT can promote the growth and Se uptake of P. frutescens.