Spatiotemporal Regulation of Starch–Sugar Metabolism by Potassium Enhances Carbon Partitioning and Processing Quality in Potatoes

To investigate the role of potassium in the regulation of potato growth, dynamic changes in starch–sugar metabolism, and processing quality. In this study, “Gannong Potato No. 9” was used as the test material, and five potassium concentration treatments of 0, 9.4, 23.5, 28.5, and 37.6 mmol/L were set. The results showed that moderate application of potassium (23.5 mmol/L) significantly enhanced plant height, stem thickness, and tuber yield. It also promotes starch accumulation in all tissues and reduces sucrose, fructose, and glucose content, thus optimizing processing quality. Dynamic analyses showed that potassium affects carbohydrate transport and partitioning among tissues by regulating the direction of carbon partitioning and the rate of conversion. Correlation analysis confirmed the synergistic effect of starch–sugar metabolism among tissues, forming a spatio-temporally linked carbon allocation network. This study reveals the pivotal role of potash in potato starch–sugar metabolism and provides a theoretical basis for precision potassium application and quality improvement.