Foliar application of melatonin-capped copper nanoparticles improves stem strength and postharvest quality by regulating the lignin biosynthesis genes and physio-chemical profile in Gerbera jamesonii L.

Gerbera (Gerbera jamesonii L.) is one of the most economically significant ornamental crops, ranking among the top five cut flowers globally. However, its low stem strength often limits its commercial quality and post-harvest vase life. The application of nanotechnology in floriculture is increasingly recognized for its potential to extend post-harvest life and enhance the quality of ornamental flowers. Melatonin (N-acetyl-5-methoxytryptamine) (MT), a well-known bio-stimulant, has been demonstrated to regulate various key physiological processes such as growth and stress resistance in plants. Despite the documented benefits of MT in plant physiology, its combination with nanoparticles to improve structural integrity and post-harvest performance has not been fully explored. In this study, we investigated the effects of melatonin-capped copper nanoparticles (MT-CuNPs) and MT on stem strength and post-harvest quality of gerbera-cut flowers. Our results demonstrated that MT-CuNPs treatment significantly improved photosynthetic parameters, enhanced antioxidant activity, increased stem diameter, lignin content, and xylem cell wall thickness, thereby strengthening the mechanical properties of the plant. Additionally, MT-CuNPs treated plants exhibited improved biochemical traits, such as higher soluble sugar and phenolic content, associated with enhanced post-harvest longevity. Vase life studies revealed a 6-day extension in the longevity of MT-CuNPs treated gerbera flowers, which showed reduced senescence and delayed wilting compared to control. These changes were supported by the upregulation of key lignin biosynthetic genes as confirmed by quantitative real-time-PCR (qRT-PCR) analysis. This underscores the significant potential of nanotechnology for innovative applications in the floriculture industry.