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To explore the effect of the photoperiod on the accumulation and distribution of dry matter in potato, a pot experiment was carried out in 2021 and 2022 with two varieties (Atlantic and Hezuo 88). The varieties were used as the main plot, and light treatments (short-day and long-day) were used as the subplot. The results showed that extended hours of light delayed tuber formation in Hezuo 88, however, the effect was not obvious for the Atlantic. Comprehensive analyses were carried out using the potato developmental process, dynamic equation fitting of the tuber and whole-plant dry matter accumulation, and the dry matter accumulation and distribution rate of each organ of the two varieties under two photoperiods. The two photoperiods had different effects on the parameters of rapid tuber and whole-plant dry matter accumulation: the starting point of the period of the rapid dry matter accumulation (t1), the duration period of the rapid dry matter accumulation (Δt), and the average growth rate of the period of the rapid dry matter accumulation (Vmean). According to comprehensive analysis, tuber dry matter accumulation in Atlantic was the highest under the short-day condition, while Hezuo 88 showed the lowest tuber dry matter accumulation under the long-day condition and was the latest to enter the rapid tuber dry matter accumulation period. The whole-plant dry matter accumulation in Atlantic was the highest under the long-day condition and lowest in Hezuo 88; meanwhile, Hezuo 88 was the latest to enter the rapid whole-plant dry matter accumulation period. In terms of the dry matter accumulation and dry matter partitioning ratio of various organs, Hezuo 88 had the lowest mean tuber dry matter accumulation and partitioning ratio under the long-day condition but the highest mean stem, leaf, root, underground stem, and stolon dry matter partitioning ratio. On the contrary, Atlantic had the highest mean tuber dry matter accumulation and portioning ratio under the short-day condition but the lowest mean stem, leaf, root, underground stem, and stolon dry matter partitioning ratio. It was concluded that different varieties of potato respond differently to the photoperiod. In the case of Hezuo 88, prolonging the photoperiod affected the dynamics and distribution of dry matter accumulation; increased the stem, leaf, root, and underground stem dry matter partitioning ratio; and decreased the tuber dry matter partitioning ratio, which resulted in a decrease in tuber dry matter accumulation and consequently delayed the emergence of the equilibrium period between the aboveground and underground dry matter.

Nitrogen is an essential nutrient for plant growth. However, the excessive use of nitrogen fertilizers not only increases production cost, but also has negative a impact on the environment. The purpose of this study was to quantify the source-sink characteristics and length of each growth stage in two potato varieties under different nitrogen application rates. This clarifies the source-sink coordination characteristics of the nitrogen-efficient variety and the source-sink coordination mechanisms of high nitrogen use efficiency (NUE). Field experiments were conducted in 2019, 2020, and 2021 using a split-plot design, with a nitrogen application rate of (0; 150 kg·ha−1; 300 kg·ha−1) as the main plot and variety (J, nitrogen-efficient variety Jizhang 12; Y, nitrogen-inefficient variety Youjia 70) as the subplot. The results showed that the yield and NUE of Jizhang 12 at 300 kg·ha−1 were, on average, 90.73% and 75.15% higher than those of Youjia 70, respectively. The NUE and nitrogen utilization efficiency of Jizhang 12 increased on average, with decreasing N application at 68.66% and 24.53%, which were higher than those of Youjia 70 at 62.89% and 10.86%. Quantitative analysis of the source and sink showed that the Jizhang 12 had a higher source and sink capacity of 23.45 g and 51.85 g, respectively, and the maximum source and sink activity was on average 0.28 g·plant−1·d−1 and 1.47 g·plant−1·d−1 higher, and the growth period of the source and sink was on average 24 days and 7 days longer, respectively. On the basis of these results, the nitrogen-efficient varieties had a higher yield base and a smaller reduction in NUE with reduced N application. In terms of source-sink growth, N-efficient varieties lasted longer at the seedling and tuber initiation stages, when potatoes grew above ground and source organs grew for longer periods, providing a solid foundation for later sink growth, as evidenced by their higher source-sink activity, capacity, and growth time than N-inefficient varieties.