Objectives Satisfactory soil aeration is inductive to increase ATP content in the storage root, thus improve the transformation of dry matter from vegetative organ to storage roots. We studied the regulation mechanism of soil textures on the storage root respiration and energy supply paths, to provide theoretical base for the high yield cultivation of sweet potato.

Methods Starch sweet potato varieties Shangshu 19 and Jishu 25 were selected as experimental materials in field experiment conducted in 2020 and 2021 in Shandong Province. Three soil texture treatments, namely sandy loam (SL), loam (LS), and clay loam (CL), were set up. Since 45 days after the planting of seedlings, plant samples were collected every 20 days for determination of storage root weight, bulking rate, energy compound ATP, ADP, and AMP content, and respiratory rate. The storage root yield was investigated at harvest.

Results SL treatment was recorded higher storage root yield and single storage root weight than LS, with yield increase of 13.94%−32.91%, while CL treatment was recorded lower storage root yield and single storage root weight, with the yield decreased by 6.71%−22.1%, however, the storage root number per plant was not significantly different among the three soil texture treatments. Compare with LS, the storage root bulking rate was higher in SL but lower in CL treatment (P<0.05). During the rapid storage root bulking period (65 days to 125 days after planting), the storage root sucrose content was lower and starch content was higher in SL treatment than in LS, while the sucrose content was higher and the starch content was lower in CL treatment than in LS significantly. Compared with loam soil treatment, the respiration rate of total, glycolytic pathway (EMP) and tricarboxylic acid cycle (TCA) in SL treatment were 12.48%−34.36%, 7.14%−43.23% and 7.14%−39.62% higher than those in LS treatment, respectively. The gap in the total and TCA respiration rate between the SL and LS treatment reached largest at the peak of storage root enlargement. The storage root in CL treatment was tested the lowest total respiration rate and highest pentose phosphate pathway (PPP) respiration rate, among the three soils texture treatments. The ATP, ADP and AMP contents in storage root of SL treatment were significantly higher than those in LS, while those in CL treatment were significantly lower. The correlation analysis showed that the storage root yield and single storage root weight were positively correlated with ATP content, and the storage root bulking rate was positively correlated with ATP and ADP content. The results of path analysis showed that ATP content showed the highest direct effect on single storage root weight, and TCA respiration rate showed the highest total effect on single storage root weight, and its total effect was mainly realized through the indirect effect of ATP content.

Conclusions Storage root respiration rate, ATP and ADP contents of storage root were closely related to storage root bulking, single storage root weight and yield, and ATP content directly and indirectly affected single storage root weight. The treatment of sandy loam soil enhances aerobic respiration of storage roots, improves ATP production efficiency, provides sufficient energy supply, promotes starch synthesis and accumulation, and leads to rapid storage root bulking and high storage root yield. The anaerobic respiration in the treatment of clay loam storage roots is enhanced, resulting in less ATP production, which is not conducive to starch synthesis, slow storage root bulking, and low storage root yield.