| Subspecies hybrid rice which are widely adopted in China show a strong superiorities in larger spike, more grain number and stronger growth potential, but a low seed setting rate of most combinations become a major obstacle in their application and extension. By setting up an IAA HPLC detection method, and application of isotopes and ELISA technique, the correlation of endogenous 1AA with the grain filling were studied in this thesis. Subspecies hybrid rice Xieyou9308 with its restorer Zhonghui9308 was tested as main material; Xieyou9312 and Hyou162 with their restorers were also planted and sampled in this experiment. The results are briefly described as follows.1. Purification and detection method of endogenous IAA in subspecies hybrid rice grains was improved and established. It is simplified and operable method when compared to the traditional one, and the released data is coincides with quantitative requirements.2. Further confirmation of the "Apical-grain superiority" in grain filling: It is a common phenomenon of apical-grain superiority in grain filling, but the differences were existed within combinations and restorers. There were some correlation between restorer and its hybrid rice, the apical-grain superiority in combination was amplified when comparing to its restorer.3. Carbohydrate accumulation in spikelets: Superior spikelets showed a privilege in easy access to accumulate the carbohydrate. The carbohydrate content in superior spikelets increased rapidly soon after pollination and reach the peak. Only then, the carbohydrate content in inferior spikelets began to accumulate. The combination and its restorer show a similar fluctuation pattern in carbohydrate accumulation. During grain filling period, the accumulating ratio of three kinds of sugar (Glucose/Sucrose/Fructose) in spikelets of restorer showed a correlation with its combination.4. Endogenous IAA content in superior spikelets of the combinations increased rapidly soon after pollination. While as the IAA content in inferior spikelets was stay still for a period of 7 days from pollination. IAA content in inferior spikelets was much less than the superior spikelets. These phenomena were also observed in their restorers, but as compareto their combinations, the scope of IAA fluctuation was reduced. There was a positivecorrelation of the phenomena between restorer and its combination.5 > Endogenous IAA could be a signaling substance for triggering the grain filling.First, Resulting from isotopes experiments, 3H-IAA accumulation in spikelets was always 3-6 hours prior to H-Glucose accumulation.Second, IAA transport inhibitor-TIBA inhibited the accumulation of 3H-IAA in spikelets; IAA bio-synthesis inhibitor-PCIB inhibited the accumulation of 3H-IAA in spikelets through the inhibiting of 3H-Try transportation; The two inhibitors could also reduce the 3H-Glucose accumulation in spikelets by decreasing endogenous IAA level.Third, Exogenous IAA application on young panicle could be a assisting effects of carbohydrate accumulation in spikelets. The application of high concentration IAA to the young panicle (before anthesis) could improve the seed setting rate of inferior spikelets, and more or less decrease the seed setting rate of the superior spikelets. The main reason of the above phenomena could be a reduced difference of endogenous IAA level in spikelets by exogenous IAA application, and then the apical-grain superiority between superior spikelets and the inferior spikelets was weakened.Therefore, it is considered in this dissertation that endogenous IAA is a signaling substance in triggering the grain filling. There is a positive correlation between IAA emerging time & intensity and the starting & intensity of the grain filling in spikelets. The application of exogenous IAA could improve seed setting rate by weakening the apical-grain superiority. It will be a new stream to the photo-hormone physiology, and will have some practical meaning in improvement of the seed-setting rate by m...
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