Factors determining the thickening and the shape of the tuberous root in sweet potato (Ipomoea batatas (L.) Lam.). Effect of irrigation at the early growth period.

摘要

Effects of irrigation during the early growth period were investigated on the thickening and shape of sweet potato tuberous roots. The number and length of tuberous roots were determined 70 days after planting (DAP). There was a high positive correlation between the length and width of the tuberous roots, indicating that the rate of lateral growth was higher in the long tuberous roots than in the short tuberous roots. The width/length ratio of the tuberous roots tended to converge as growth progressed, although during the final growth period, the width/length ratio was larger in the irrigated plot than in the non-irrigated plot. Spindle-type and long spindle-type tuberous roots constituted 35 and 65%, respectively, of the total number at 70 DAP. However, during the final growth period, most of the tuberous roots in the irrigated plot were of the spindle-type, while in the non-irrigated plot, many were of the long spindle-type. Results indicate that irrigation during the early growth period greatly affects the shape of sweet potato tuberous roots.