Effects of Plastic Film Mulching Cultivation on Young Roots Growth Development, Tuber Formation and Tuber Yield of Sweet Potato

Abstract

A two-year trial and a one-year pot experiment were performed to investigate growth and development and absorbing ability of young roots, endogenous hormones content of differentiated roots at early growing stage using variety Jixu 23 with two types of plastic film mulching cultivation, and no plastic as control(CK). The tuberous root fresh weight per plant at 50 days after planting was determined, and its relationship with tuberous root yield at harvest time was analyzed. The results showed that, at 10 and 20 days after planting, the number, total length, fresh weight, and volume of young roots significantly increased compared with control, and the differences in activity, total absorption area and active absorption area of young roots between two plastic film mulching treatments were significant(P0.05), showing the black plastic film mulching(BF) superior to the transparent film mulching(TF). Besides, zeatin riboside(ZR) content of differentiated roots(at 10 and 20 days after planting) was significant improved, which was in favor of procambium activity and tuberous roots formation. On the other hand, at early expansion period of tuberous roots, plastic film mulching cultivation increased abscisic acid(ABA) content and decreased gibberellin(GA) content in differentiated roots, as well as improved the secondary cambium activity, starch accumulation and differentiated root expansion. Meanwhile, abscisic acid(ABA) content and gibberellin(GA) content under the black film mulching significantly changed. Film mulching cultivation increased the number and fresh weight of tuberous roots per plant at 50 days after planting, which contrib-uted to higher fresh yield of tuberous root at harvest time. In the two year experiment, two treatments significantly enhanced the valid tuber number and fresh tuber yield compared with CK. The average increments were 10.71% and 5.76% in 2011, and 12.99% and 7.45% in 2012, respectively.