Abstract: 【Objective】Sweetpotato (Ipomoea batatas (L.) Lam) is a typical K-preferred starchy root crop. Potassium (K) deficiency (namely low potassium), an important abiotic stress in plants，has become a major limiting element for obtaining crop high yield and good quality. However, in China, K deficiency in soils exists commonly in sweetpotato-growing areas. Sweetpotato starch utilization is closely related with its physico-chemical properties. The influence of low potassium on starch physic-chemical properties was investigated in an experiment conducted by using three sweetpotato cultivars with different potassium utilization efficiencies (KUE) in response to low potassium(K) field condition, aiming at providing reference for improving sweetpotato root properties and potassium utilization efficiency. 【Method】Three sweetpotato cultivars with different potassium utilization efficiencies (KUE) were chosen and cultivated under different potassium field condition, including two treatments (low potassium treatment, LK, and normal potassium treatment, CK).【Result】The results showed that under low K condition, the main components (amylose, amylopectin, nitrogen, total phosphorus and total lipid) in sweetpotato storage root starch changed to a certain extent. There were some differences among the three cultivars in the main components. Three distribution peaks in ≤2.50 μm, 2.50-5.00 μm and 5.00-30.00 μm were observed in starch granule size obviously. The slight decrease was observed in the whole average granule size under low K, which of Xushu32 had the least decrease in volume distribution. However, there was a significant difference in decrease of average granule size of Ningzishu1. The percentage, average granule size and peak value of different granule sizes in three distributions had some differences among three cultivars. Starch T₀ (gelatinization temperature), Tp (peak temperature) and ΔH (heat enthalpy) were basicially lower than that in CK treatment, and Ningzishu1 had significant differences in the three characteristic values. Peak viscosity and breakdown viscosity in three genotypes had an obvious decrease. Hot paste viscosity, cool paste viscosity in Xushu18 and Ningzishu1 significantly increased, but Xushu32 was on the contrary. Moisture absorption degree of starches in three genotypes was reduced differently. There was a significant difference in the decline of moisture absorption in Xushu18 and Ningzishu1. In addition, swelling power of starch increased differently in three storage root starchs. There was a significant difference in a rise of swelling power of starch in Ningzishu1. Xushu32 had high starch swelling power, but low K had a little effect on it. Correlation analysis showed that the main physico-chemical indicators of sweetpotato starch are closely related. The low K changes starch compositions and particle sizes in sweetpotato root, which led to different degrees of influence on starch gelatinization properties and thermal properties.【Conclusion】The results of the study findings indicated that potassium is a key plant element influencing sweetpotato starch physico-chemical properties. Some obvious effects on physico-chemical properties and main components exist in storage root starch under low K stress. The responses of sweetpotato genotypes differing in potassium utilization efficiency to low K stress are different.

Key words: sweetpotato (Ipomoea batatas(L.) Lam), low potassium stress, storage root, starch; physico-chemical properties