| In this experiment, three water irrigation gradients were set at the seedling stage, namely full irrigation (M65), mild deficit (M50) and severe deficit (M35), the leaf area index and biomass were measured at the whole growth stage, and the yield and its components were measured at the maturity stage, and the sucrose synthase (SS-synthesis direction), sucrose phosphate synthase (SPS), adenylyl glucose pyrophosphorylase (AG-Pase), starch synthase ( SSS) activity, and changes in the content of carbon metabolites sucrose and starch. The results showed that the leaf area index and biomass of potato were significantly higher than those of the control after rewatering under mild water stress at seedling stage, which were 29.11% and 13.21% higher at the starch accumulation stage, respectively, and the yield was also significantly higher than that of the control. Under water stress, the SS-synthesis direction and AG-Paste activity in leaves were significantly enhanced, and the mild deficit increased by 264.91% and 762.39%, respectively, and the severe deficit increased by 144.94% and 251.28%, respectively. The activity of SPS in leaves was significantly reduced, with mild deficiency decreasing by 47.16% and severe deficiency decreasing by 83.01% compared with the control treatment. There was no significant difference in SSS activity between mild deficiency and control, and severe deficiency was significantly lower than that of control. The contents of sucrose and starch in mildly deficient leaves increased significantly by 1.81% and 19.70%, respectively, compared with the control. After rewatering, the activities of SPS, SS-synthesis direction and AG-Paste in mildly deficient leaves were restored to the control level, and the starch content decreased significantly by 38.14%~69.69%, restoring the supply capacity of the source. Compared with the control, the SSS activity in the mildly deficient tubers increased by 29.72%, and the other enzyme activities returned to the control level, and the contents of sucrose and starch increased, which enhanced the activity of the reservoir. There was a significant positive correlation between sucrose and starch content in potato leaves, and a significant positive correlation between starch content and AG-Pase and SSS activities in tubers. The results showed that moderate water deficit and rewatering at potato seedling stage reconstructed the source-sink relationship and realized the compensatory growth of plants, which was conducive to high potato yield and water efficiency. |