Responses of lotus rhizome nutrient composition, polyphenol, and starch to growth period and cultivar

• Vc increased, followed by a decrease and a subsequent rise with growth periods. • Wuzhi No. 2 had high water, while Baiyuzhan had high TSS, soluble sugar and Vc. • Antioxidant capacity, phenolic, flavonoid, PAL activity increased with growth. • PAL1, POD were correlated with total phenolic and flavonoid in both cultivars. • Starch accumulated with growth periods and was correlated with SSI, GBE1-2, ISA2/3. The appearance, nutrition and functional components of lotus rhizome determine its commercial value. This study presents a comprehensive comparison of the dynamic changes in appearance, nutritional quality, polyphenol content, and starch accumulation across growth stages of two lotus rhizome cultivars Wuzhi No. 2 and Baiyuzhan and unravels the underlying molecular mechanisms. The color of both cultivars shifted from pale white to light yellow, with browning degree and texture (firmness, chewiness, cohesiveness) increasing during growth. During growth, TSS and soluble sugars accumulated whereas water content decreased. Soluble protein first decreased, then increased, and finally declined; vitamin C showed the opposite trend. Wuzhi No. 2 had higher water content, while Baiyuzhan had higher TSS, soluble sugars and vitamin C. Antioxidant assays indicated DPPH and ABTS free radical scavenging activities, total phenolic content, total flavonoid content and PAL activity all increased during growth. Additionally, gallic acid, hyperin, catechin, resveratrol (Baiyuzhan) and catechin (Wuzhi No. 2) accumulated with growth. NnPAL1/3/4, NnPOD, NnCOMT-like, NnCHS1, NnF3H, and NnANR were correlated with both total phenolic content and total flavonoid content. Starch accumulated with growth periods and was correlated with NnSSI, NnGBE1-2 and NnISA2/3. This study provided a theoretical basis for the utilization and product development of high-quality of lotus rhizome.