Melatonin and 24-epibrassinolide promote the growth and selenium uptake of wild peach seedlings under selenium stress

To enhance selenium (Se) uptake in peach plants, a pot experiment was conducted to study the effects of melatonin (150 μmol/L) and 24-epibrassinolide (1.5 mg/L) on the growth and Se accumulation of wild peach (as the rootstock of peach) seedlings under Se stress (0.1 mg/L). The results showed that the application of melatonin, 24-epibrassinolide, and the combination of both increased the biomass and levels of photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids) in wild peach seedlings under Se stress. Furthermore, these treatments increased the activities of peroxidase and catalase while decreasing the activity of superoxide dismutase. Among the treatments, only the combination of melatonin and 24-epibrassinolide resulted in an increase in root Se content and root bioconcentration factor (BCF) in wild peach seedlings. Compared to the Se treatment alone, the treatments with melatonin, 24-epibrassinolide, and the combination increased the shoot Se content by 40.87%, 53.91%, and 53.04%, respectively, as well as the translocation factor, shoot BCF, and whole plant BCF of wild peach seedlings. Correlation and gray relational analyses revealed that the carotenoid content, chlorophyll a content, root biomass, and chlorophyll b content showed the closest relationships with the shoot Se content under Se stress. Thus, the application of melatonin, 24-epibrassinolide, and the combination of both can effectively promote the growth and Se uptake in wild peach seedlings under Se stress, with the best results observed with the combination of melatonin and 24-epibrassinolide.