Changes of Chlorophyll Content & Grain Filling Characteristics of the Super High-yielding Rice Cultivars with Different Plant and Panicle Types

To raise the population photosynthetic efficiency, Chen Wen-Fu (1987) thought,the quantity and the quality of photosynthetic organ should be increased. The photosynthetic capacity of panicle in rice is so weak that it's contributive rate is less than 5% to grain weight (Tsunoda S, 1965), therefore, leaf is the main photosynthetic organ in rice. The chlorophyll content is an important index of leaf quality, and effect the economic yield and biological yield indirectly or directly. Many researchers focused on the relation between chlorophyll content and yield,but little research was on the law of variation of chlorophyll content. In rice super high yielding breeding, the law of variation of chlorophyll and resources with different chlorophyll contents have important theoretical and practical significance. The yield of rice is finally decided by the grain filling, which process was described by Kato(1993), Zhu Qing-Sen(1988), Gu Shi-Liang (2001), et al. through linearity-plain model, but it is very simple and rough. Richards equation which was used in this paper can exactly describe the law of grain filling process.In 2001, 41 super high yielding rice cultivars with different plant and panicle types were arranged in a randomized block experimental design with three replications. Each experimental unit was composed of 5 rows 5 m long, 3 seedlings/ hole. Transplant density was 30 cm × 20 cm. Nitrogenous level was 150 kg/ha.In 2002, cultivar Ji-99F90, Ji-01-124, J-E262, Jite-623 and Chaochan-1(CK) (Table 1) were used in the experiment, the design and cultivitive practices were the same as that in 2001.The results indicated that the chlorophyll contents of the 2nd and 3rd leaves from the top of cultivars with semi-erect panicle was higher than that of flag leaf during 20 days after heading stage(Fig.3,4), and only higher than that of flag leaf during 10 days after heading stage for other cultivars with different panicle types(Fig.7). Cultivars with semi-erect panicle would be ideal for its chlorophyll content in flag leaves increased rapidly in early stage of development, and declining in later stage. The filled grain weight of the upper, the middle and the lower panicle was similar in that of semi-erect panicle type, which had higher grain-filling rate and a sufficient matter to fill the inferior grains (Table 3 and Fig.9,10). The inferior grain weight of erect panicle type was largely lower than that of the superior one, the seed-filling stage was delayed (Table 3 and Fig.9,10). The large curved panicle type was so-called typical asynchronous type, the inferior grain weight was half of upper grains, and its grain filling characteristics was undesirable (Table 2 and Fig.9, 10).