In the context of climate change and severe water shortages in agriculture, we explored water stress responses in the sweet potato (Ipomoea batatas) in terms of endogenous hormone levels and other physiological characteristics, providing a theoretical basis for drought-resistant cultivation of sweet potato. This study was conducted from 2021–2022 in a solar greenhouse under artificially controlled water conditions. We determined biomass, agronomic indexes, photosynthetic parameters, and endogenous hormone levels in three treatments: normal water supply (CK), mild drought (LD), and severe drought (HD). The results revealed that drought stress inhibited aboveground and belowground sweet potato growth compared with CK; sweet potato yield decreased with increasing drought. The net photosynthetic rate, stomatal conductance, and transpiration rate of sweet potato leaves decreased significantly under drought stress. The leaves’ intercellular CO₂ concentration (Ci) decreased with increasing drought up to 50 days after transplanting but increased with increasing drought up to 75 days after transplanting. The zeatin riboside (ZR) and indole-3-acetic acid (IAA) contents were significantly lower in sweet potato leaves and tubers in the LD and HD treatments compared with CK, whereas the abscisic acid (ABA) content was significantly higher. Within the same period, the (ZR + IAA)/ABA ratio decreased with increasing drought severity. Correlation analysis revealed that the ABA and leaf Ci were significantly positively correlated, and both indices were significantly negatively correlated with all other indices. Aboveground dry weight was significantly correlated with the ZR and IAA contents. These findings demonstrate the regulatory effects of elevated leaf ABA concentrations on stomatal conductance during drought and indicate that stomatal closure was mainly responsible for the decreased photosynthetic rate observed in the early stage of drought. The rapid decrease in the photosynthetic rate in the late stage of drought may have been caused by non-stomatal factors. These findings provide a theoretical foundation for future drought-resistant sweet potato cultivation.

Sufficient soil moisture is required to ensure the successful transplantation of sweet potato seedlings. Thus, reasonable water management is essential for achieving high quality and yield in sweet potato production. We conducted field experiments in northern China, planted on 18 May and harvested on 18 October 2021, at the Nancun Experimental Base of Qingdao Agricultural University. Three water management treatments were tested for sweet potato seedlings after transplanting: hole irrigation (W₁), optimized drip irrigation (W₂), and traditional drip irrigation (W₃). The variation characteristics of soil volumetric water content, soil temperature, and soil CO₂ concentration in the root zone were monitored in situ for 0–50 days. The agronomy, root morphology, photosynthetic parameters, ¹³C accumulation, yield, and yield components of sweet potato were determined. The results showed that soil VWC was maintained at 22–25% and 27–32% in the hole irrigation and combined drip irrigation treatments, respectively, from 0 to 30 days after transplanting. However, there was no significant difference between the traditional (W₃) and optimized (W₂) drip irrigation systems. From 30 to 50 days after transplanting, the VWC decreased significantly in all treatments, with significant differences among all treatments. Soil CO₂ concentrations were positively correlated with VWC from 0 to 30 days after transplanting but gradually increased from 30 to 50 days, with significant differences among treatments. Soil temperature varied with fluctuations in air temperature, with no significant differences among treatments. Sweet potato survival rates were significantly lower in the hole irrigation treatments than in the drip irrigation treatments, with no significant difference between W₂ and W₃. The aboveground biomass, photosynthetic parameters, and leaf area index were significantly higher under drip irrigation than under hole irrigation, and values were higher in W₃ than in W₂. However, the total root length, root volume, and ¹³C partitioning rate were higher in W₂ than in W₃. These findings suggest that excessive drip irrigation can lead to an imbalance in sweet potato reservoir sources. Compared with W₁, the W₂ and W₃ treatments exhibited significant yield increases of 42.98% and 36.49%, respectively. The W₂ treatment had the lowest sweet potato deformity rate.