High Yield Formation and Its Eco-Physiological Characteristics of Cast-Trans¬planting Rice

Abstract

Cast-Transplanting rice has a low cost, easy operation, high and stable yield potential advantage, Depth study of the seedings throwing is very important to develop the light and simple cultivation of rice. The purpose of this study is to explore the high yield formation and its eco-physiological characteristics of cast-transplanting rice. Under the rice-wheat cropping systems, conventional japonica cultivar Nanjing 44 and japonica hybrid rice cultivar Yongyou 8 were used to investigate the characteristics of high yield formation including tillering dynamic, LAI, photosynthetic potential, dry matter production and the eco-physiological basis, such as post-root activity, photosynthetic characteristics, material accumulation and translocation, with three cast-transplanting methods of transplanted seedlings (TS), pointed seedlings (PS), and broadcasted seedlings (BS) in contrast with the manually transplanting of seedlings with roots washed beforehand (MTS), which could provide the theoretical and practical basis for the high and stable yield of the cast-transplanting rice. The results showed that the yields of three methods were 21.9%, 18.3%, and 13.2% higher than MTS for Yongyou 8, and 18.3%, 14.1%, and 9.87% higher than MTS for Nanjing 44, respectively. The yields of two cultivars both showed the trend of TS PS BS MTS. Although the filled-grain percentage and 1000-grain weight of cast-transplanting rice were significantly or very significantly lower than those of MTS, the total number of spikelets of cast-transplanting rice was conformably higher than that of MTS at a significant or very significant degree. The increased yield was mainly due to the higher total spikelet number. Compared to MTS, the cast-transplanting rice had more peak seedling tillers, higher or equivalent ratios of productive tillers to total tillers, an enough number of ultimate effective panicles, higher LAI and LAD, and thus a more robust population quality. According to these results, we could give the conclusion of the eco-physiological basis of high and stable yield of cast-transplanting rice. After transplantation, there were earlier tillering, more leaf tillering positions, stronger tillering capability, and higher quality and enough quantity of tillering. At the heading stage, they had suitable plant height, stouter stems and sheaths, efficient leaf configurations, preferable air ventilation and light transmission conditions, higher biomass accumulation, a more coordinated sink-source relationship, and hence a higher yield potential. In the late growth period, the cast-transplanting rice had stronger roots, slower senescence of leaves, more powerful photosynthesis, more coordinated dry matter accumulation and translocation of stem and sheath, higher filling ratios, being more conducive to the higher yield. TS and PS have evident advantages than MTS, and are more favorable in achieving higher yield.