Preharvest silicon and triacontanol improve postharvest quality in orange and purple carrots

The application of biostimulants during crop production may influence postharvest behavior and nutritional quality of horticultural products. This study evaluated preharvest silicon- and triacontanol-based biostimulants on root yield, texture, and metabolite stability during cold storage in two carrot cultivars (Daucus carota L.), ‘Dordogne’ (orange root) and ‘Purple Sun’ (purple root). Treatments included potassium silicate, a protein hydrolysate enriched with triacontanol, and a combination of both. Root samples were evaluated at harvest and after 20 days of storage in polyethylene bags at 4 °C and 90 % RH. All treatments enhanced root weight at harvest (by up to 18 %), while potassium silicate preserved cutting force during storage. Untargeted metabolite profiling by 1H NMR revealed cultivar-specific responses in the accumulation of primary and secondary metabolites, including organic acids, soluble carbohydrates, phenolic compounds, and polyacetylenes. Notably, potassium silicate increased phenolic content in both cultivars (+10–20 %) and, together with T4, reduced polyacetylene levels in ‘Purple Sun’ (−30 %), potentially enhancing functional quality and sensory acceptance. During storage, both silicon-based treatments stabilized sugars and phenolics, limiting respiratory and fermentative losses. These effects indicate improved stress tolerance and metabolic stability, particularly in ‘Purple Sun’. Overall, potassium silicate alone proved most promising for maintaining postharvest quality and extending shelf life. These findings demonstrate the potential of silicon-based PBs as sustainable tools to enhance carrot yield, nutritional quality, and storage performance, providing practical value for producers and the fresh-cut industry.