Matter Accumulation And Transportation Characters In Stem-sheath Of Modern High-yield Varieties

Using different types of modern high-yielding rice varieties as materials, the relationship between the matter accumulation and transportation in stem-sheath and matter production and yield was studied. The objective of this study was to investigate the matter production characteristics under high-yield level and the effects of the matter accumulation and transportation in stem-sheath on yield. The main results were as follows:1. Modern rice varieties had significant heterosis of large panicle, but seed setting percentage was low in two years, and the yield was significantly correlated with seed setting percentage and total spikelets per unit area. Increasing total spikelets per unit area was the main approach to increasing the yield of modern varieties. Comparatively inadequate assimilate supply was the major constraint in the increase in grain yield of modern varieties.2. The matter accumulations of modern varieties before heading were nearly same, which were all higher than those of Shanyou63. Significant differences of matter accumulation among varieties were found after heading. The total dry matter accumulation at maturity increased, then decreased with the increase in dry matter production before heading stage, quadratic relationship was found between them. There was a positive correlation between total dry matter accumulation at maturity and matter accumulation after heading, indicating that increasing matter production during grain-filling period could improve total dry matter accumulation on the basis of moderate or higher matter production before heading stage. 3. Comparing the matter product in early and later grain filling period, the results showed that matter accumulations of Shanyou 63 and Liangyoupeijiu were higher in early grain filling period than those in later grain filling period, while the matter accumulation status of Yangliangyou6, Yangdao6 and Wuxiangjing14 was reversed, which indicated that the fine ability of matter accumulation might be related with their strong product activity in the later growing period. Improving growing status through sparse transplanting could increase the matter accumulation in later grain filling period and the trend was more obvious in modern high yielding varieties.4. There were great differences among varieties in the reserve in the stem and sheath in grain filling period, which could be divided into three groups, i.e. high output, low output and slight accumulation. The former were Shanyou63 and Liangyoupeijiu, the latter was Wuxiangjing14. Yangliangyou6 has low transfer level in the hybrid combinations. Comparing the material transfer in the later grain filling period among the tested varieties, most varieties showed strong matter output in the early grain filling period, whereas descended greatly in the later period, and more varieties showed minus transfer, that was, matter was re-filled in the stem and sheath. Analyzing the relationship between the transfer ratio of stem and sheath and the yield, it suggested that the yield had no obvious correlation with the transfer ratio, and the increase in panicle weight also had no obvious correlation with the transfer ratio.5. The yield was significantly correlated with the matter accumulation during whole growth stage. It indicated that the more matter production, the higher the yield was and more dry matter accumulation was the basis of high and super-high yield. There was parabolic relationship between the matter production before heading and the yield, and the late dry matter accumulation was significantly correlated with yield. It showed that the ability of matter production during the grain-filling period was more important to yield than high matter accumulation before heading.6. The effects of environmental conditions on the yield components were studied and the results showed that the 1000-grain weight was relatively stable, but the seed setting percentage and the grain plumpness were more complicated. The effects of environmental conditions on the individual growth of rice and matter transportation of stem and sheath changed with varieties. The transportation rate of stem-sheath reserve was negatively correlated with matter production both at earlier and later grain filling stage, which indicated too much stem-sheath reserve transportation was not beneficial to increase the ability of matter production during whole grain-filling stage.7. ABA contents in flag leaf of Shanyou63 during heading stage and in stem-sheath on 20^th day after heading were high. SOD activity in stem-sheath and chlorophyll content in the top three leaves decreased rapidly at later grain-filling period. Rapid senescence of Shanyou63 might be an important reason for its rapid decline of photosynthetic rate and low ability of matter production, while the results of Wuxiangjing14 were reversed, indicating the high physiological activities and photosynthesis of Wuxiangjing14 were beneficial to matter accumulation during later grain-filling period. The slow senescence might closely relate with transportation status of stem-sheath reserve.