LAUSR

ABSTRACT A two-year field experiment was conducted to investigate the effects of potassium on sucrose metabolism in the root system and its relationship with storage root formation in sweetpotato. Edible varieties Yanshu 25 and Beijing 553 were treated with K2O at 0, 12, 24, or 36 g m−2, and the number and length of adventitious roots in early growth stage, sucrose and hexose contents, and related enzyme activity in potential storage roots, as well as the number of storage roots and yield at harvest, were analyzed. The results showed K significantly increased the average number of storage roots per plant and yield at harvest, compared to the control. The increases were highest in 24 g m−2 K2O treatment, they changed slightly and even decreased with more K2O. Further study revealed appropriate potassium rate significantly increased the number and length of adventitious roots in early storage root formation stage. It also increased the activities of vacuolar, cell-wall and cytosolic invertase, coinciding with decreased sucrose versus increased fructose and glucose contents in potential roots. As per statistical path analysis, fructose accumulation contributed the most to storage root formation, while, in turn, cytosolic invertase contributed the most to promoting sucrose degradation and fructose accumulation.