Bioscience Methods 2026, Vol.17, No.1, 43-56 http://bioscipublisher.com/index.php/bm 44 tolerance (Shu et al., 2024). As a "lubricant" for carbohydrate transportation, potassium can regulate the source-sink relationship between the aboveground and underground parts of sweet potatoes, promoting the transport and distribution of photosynthetic products to the tubers (Gao et al., 2021). Adequate supply of potassium fertilizer can optimize the root-shoot ratio of sweet potatoes, enhance tuber enlargement and dry matter accumulation. Thus, potassium nutrition plays a crucial role in the formation of sweet potato tubers and the distribution of assimilates, and is a necessary condition for simultaneously improving the yield and quality of sweet potatoes. This study aims to clarify the influence patterns and physiological mechanisms of different potassium fertilizer application rates on the yield and quality of sweet potatoes, and to meet the practical needs for the simultaneous improvement of yield and quality. The core scientific questions include how does the potassium fertilizer application rate affect the yield and its constituent elements of sweet potatoes, as well as the trend of changes in the commodity rate of the tubers; The mechanism of the effect of potassium supply level on the dry matter rate of sweet potato tubers and starch accumulation; What are the effects of potassium fertilizer application rates on the sugar content and composition of sweet potato tubers, and the biochemical regulatory pathways; How to determine the optimal potassium application range for sweet potatoes based on the comprehensive evaluation of yield and quality indicators. Regarding these issues, the innovation points of this study lie in: through setting up a systematic potassium fertilizer gradient experiment, combined with multi-index observation and multi-objective evaluation methods, to comprehensively assess the impact of potassium application on the "high yield and high quality" goal of sweet potatoes, and to propose an optimized fertilization mode of "periodic potassium application and demand-based potassium supply", in order to provide new ideas and theoretical basis for scientific fertilization of sweet potatoes. 2 Theoretical Framework and Research Progress 2.1 The physiological basis of potassium regulation of the "source-sink" relationship and root formation Potassium regulates the "source-sink" relationship in sweet potatoes through various physiological pathways, thereby influencing the formation and expansion of the roots (Jiang et al., 2024). As the source (leaf) end, potassium helps maintain a high photosynthetic efficiency and assimilate synthesis rate. When potassium is sufficient, the regulation of stomatal opening and enzymatic reactions in the leaves becomes more efficient, avoiding feedback inhibition caused by excessive accumulation of photosynthetic products within the leaves, which is conducive to the continuous supply of transportable forms of carbohydrates (Shu et al., 2024). During the transportation process, potassium enhances the loading and unloading capacity of the phloem: on the one hand, potassium promotes the development of conducting tissues in the stem (such as increasing the cross-sectional area of the stem) and the formation of osmotic potential gradients, enhancing the driving force for the transport of photosynthetic products from the source to the sink; on the other hand, potassium ions themselves are important participants in assimilate transport, and their concentration gradients help maintain the efficient transport of sugars and other assimilates (Duan et al., 2018). For the sink (root) end, potassium nutrition can enhance the competitiveness and strength of the root, promoting earlier tuber differentiation and faster expansion. After potassium application, the sweet potato roots can promptly unload and store the photosynthetic products from the source end, reducing waste caused by accumulation at the source end (Gao et al., 2021). In summary, potassium enhances photosynthesis, expands assimilate transport channels, and increases the strength of the root storage, achieving the optimized regulation of the sweet potato's source-sink relationship and laying the physiological foundation for high-yield root formation. 2.2 Research conclusions, differences, and causes regarding potassium fertilizer application and yield/dry matter ratio A large number of studies have shown that applying potassium fertilizer has a significant effect on increasing the yield of sweet potatoes (Singh et al., 2017; Geng et al., 2024). However, there are certain differences in the conclusions regarding the extent of yield increase and the dry matter content of the tubers. The consistent finding is that compared to not applying potassium, applying potassium in a reasonable amount can significantly increase
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