Effects of potassium on yield, photosynthate distribution, enzymes' activity and ABA content in storage roots of sweet potato (Ipomoea batatas Lam.)

Abstract

Effects of supplying K2O at 0, 12, 24 and 36 g m-2 soils on distribution of photosynthates (carbohydrates produced by photosynthesis) were studied in plants of Ipomoea batatas Lam (Beijing 553). Storage roots yield, photosynthate distribution, sucrose synthase and insoluble acid invertase activities, as well as abscisic acid content in storage roots were determined. The storage root yield first increased and then decreased as the increase in potassium fertilizer supply, with the highest increase of 36.42% under treatment of 24 g K2Om-2 (K24) which was determined to be the optimal amount of fertilization. Under the K24 treatment, the chlorophyll content and PN of functional leaves were improved in the early growth stage, as was the leaf area index. This treatment also increased the sucrose synthase activity and abscisic acid content of storage roots by 16.47% and 18.27%, respectively, for the whole growth stages, and improved insoluble acid invertase activity by 5.75% in the late growth stage. Larger increases of abscisic acid content appeared in late growth stage. More photosynthates were unloaded to storage roots as a result of the improved sucrose synthase, insoluble acid invertase activities and abscisic acid content which contributed to sink strength. The dry matter distribution rate of storage rootswas significantly higher (69.45%) in plants with K24 treatment. In summary, sweet potatos under K24 treatment not only supplied more photosynthates during the early and middle growth stages but also had higher sink strength of storage roots which lead to higher photosynthate distribution in storage roots mainly in the late growth stage. The optimal amount was K2O 24 g m-2.