Advantages and Their Formation Characteristics of the Highest Population Productivity of Nitrogen Fertilization in Japonica/Indica Hybrid Rice of Yongyou Series Root System Morphological and Physiological Characteristics of Indica-japonica Hybrid Rice of Yongyou Series A Dynamic Model and Its Characteristics Analysis for Nitrogen Accumulation after Heading in Yongyou 538 Characteristics of Super-high Yield Population in Yongyou Series of Hybrid Rice Canopy Structure and Photosynthetic Characteristics of Yongyou Series of Indica-Japonica Hybrid Rice under High-yielding Cultivation Condition Dynamic Model and Its Characteristics Analysis for Dry Matter Production after Heading of Indica/JaponicaHybrid Rice of Yongyou Series