Application of selenium nanoparticles is more effective in improving the growth, yield, antioxidant enzymes, and essential oil production of Dracocephalum kotschyi Boiss compared to sodium selenite

Abstract

Background: Dracocephalum kotschyi Boiss., a perennial medicinal and aromatic plant endemic to Iran, is renowned for its diverse biological and medicinal properties. This study aimed to evaluate the influence of foliar application of selenium nanoparticles (Se NPs) and sodium selenite (Na2SeO3) on the growth, yield, physiological and biochemical characteristics, and essential oil (EO) of D. kotschyi. The experiment included seven treatments: a control (distilled water) and foliar spray of 50, 100, and 200 mg L-1 of both Se NPs and Na2SeO3 separately. Results: Se NPs were found to be more effective than Na2SeO3 in improving plant growth and yield. Specifically, a 200 mg L-1 Se NPs treatment led to the highest plant height, fresh weight of plant, dry weight of leaf, and relative water content. Elevated Se concentrations were associated with a decrease in chlorophyll level. Both Se NPs and Na2SeO3 treatments increased hydrogen peroxide levels, and the activity of catalase and ascorbate peroxidase. The phenylalanine ammonia-lyase activity increased with Se NPs up to 50 mg L-1 and Na2SeO3 up to 100 mg L-1. Application of 200 mg L-1 Na2SeO3 resulted in the highest total phenol content and antioxidant activity. Although spraying 100 mg L-1 Se NPs led to the highest EO content, the EO yield peaked with 200 mg L-1 Se NPs. Notably, the application of 200 mg L-1 Se NPs reduced the level of neral, while 200 mg L-1 Na2SeO3 decreased both geranial and neral levels. Conversely, levels of α-pinene and geranyl acetate increased with Se application. Conclusions: The results revealed that Se NPs was more effective than the Na2SeO3 for improving plant growth and yield. Overall, the 200 mg L-1 Se NPs treatment was the most effective in improving growth, yield attributes, and EO yield of D. kotschyi.