Physiological Basis Of Plastic Mulching On Tuberous Roots Formation And Thickening In Sweet Potato

This experiment was carried out at the experimental station of Shandong Agricultural University from May2010to October2011.Combing the pot and field experiment method, the study was conducted to investigate systematicly the physiological basis of effects of seedling quality and plastic mulching on the tuberous roots formation and thickening in sweet potato. The main results were as follows:1Effect of plastic mulching on the ecological environment of the soilPlastic mulching improved the soil ecological environment, improved the soil temperature, moisture and porosity, reduced the soil bulk density and available nutrient content, so as to promote the absorption of available nutrients of the plant and lay the foundation of root explandation. Transparent film had better effect than black film on increasing temperature, black film water retaining property was better than transparent film, while it played the role of decreasing the temperature at the highest temperature period.2Effect of seedling quality and plastic mulching on the tuberous roots formation and thickening of the sweet potatoBoth of strong seedling and plastic mulching were beneficial to make tuberous roots formation earlier, improved the weight per plant of tuberous root of sweet potato significantly, so as to provide greater sink capacity for nutrient transportation from the shoot to underground part. Comparing with strong seedling, the role of the plastic mulching was more obvious. Meanwhile, plastic mulching promoted the shoot growth and played a part in accelerating sweet potato growth in some degree. Both of strong seedling and plastic mulching improved chlorophyll content, photosynthetic rate in the early period of sweet potato growth, so as to provied a foundation for root growth and development.Both of strong seedling and plastic mulching were beneficial to root growth and development, increased seedling root quantity and improved the root activity. The black film was better than transparent film. Both of strong seedling and plastic mulching promoted the cambial activity of tuberous root, made the root structures appear early. At tuberous roots formation stage, strong seedling and plastic mulching improved the root endogenous hormones ABA and ZR content, while improved ABA content, decreased ZR content at early stage of tuberous root thickening, it was beneficial for increasing the turberous root weight of per plant.3Effect of seedling quality and plastic mulching on the tuberous root dynamic explandation of the sweet potatoBoth of strong seedling and plastic mulching promoted the growth and development of sweet potao, improved biological yield of sweet potato, meanwhile promoted the shoot dry matter transportation, improved the harvest-time dry matter distribution ratio to underground part. Both of strong seedling and plastic mulching decreased the N/K ratio, especially decreased the N/K ratio dramatically in early period that were beneficial for photo synthetic product transfer into tuberous root and coordinated the nitrogen metabolism and carbon metabolism, ensured root dry matter accumulation at the later period, so as to promote the tuberous root explandation.4Effect of seedling quality and plastic mulching on yield and yield components of sweet potatoBoth of strong seedling and plastic mulching improved the fresh yield of sweet potato in different extent. The plastic mulching effect was more evident. Both of them had different ways to increase yield, the strong seedling increased yield was due to increase the number of tuberous root. But plastic mulching increased yiled not only due to increase number of tuberous root, but also increased tuberous root weight per plant that is the main way to increase yield. Strong seedling decreased the number ratio and weight ratio of big tuber, increased the number ratio and weight ratio of mid-tuber and small tuber. Plastic mulching mainly increased the number ratio and weight ratio of big tube, and had little effect on mid-tuber and small tuber. From the analysis results of interaction effects, the interaction effect was not signicance, choosing strong seedling and mulching black film to cultivate the sweet potato is better to increase the yield in actual production.