中文摘要：

种植4个超级稻品种[两优培九和Ⅱ优084（杂交籼稻）、淮稻9号和武粳15（粳稻）]和2个高产对照品种[汕优63（杂交籼稻）和扬辐粳8号（粳稻）]，观察其结实期强、弱势粒中蔗糖合酶（SuSase）、腺苷二磷酸葡萄糖焦磷酸化酶（AGpase）、淀粉合酶（StSase）和淀粉分支酶（SBE）活性及玉米素＋玉米素核苷（Z＋ZR）、3-吲哚乙酸（IAA）和脱落酸（ABA）含量的变化，并测定了强、弱势粒灌浆速率。结果表明，超级稻品种强势粒的最大灌浆速率、到达最大灌浆速率的时间、平均灌浆速率和糙米重与对照品种差异较小，超级稻品种弱势粒的灌浆速率和糙米重显著低于对照。灌浆期强、弱势粒的SuSase、AGPase、StSase和SBE活性变化及Z＋ZR、IAA和ABA含量变化均呈单峰曲线。弱势粒的SuSase、AGPase、StSase和SBE的峰值活性和平均活性及其Z＋ZR和IAA的峰值含量和平均含量均低于强势粒。弱势粒的ABA峰值含量和平均含量显著高于强势粒，超级稻品种高于对照品种。籽粒灌浆速率与SuSase、AGPase和StSase活性及Z＋ZR和IAA含量均呈显著或极显著正相关，与SBE活性及ABA含量的相关不显著。说明超级稻品种弱势粒中较低的SuSase、AGPase和StSase活性及较低的Z＋ZR和IAA含量是其灌浆速率小、粒重轻的一个重要原因。

英文摘要：

The changes in activities of key enzymes involved in sucrose-to-starch conversion and contents of hormones in superior and inferior spikelets were investigated and their relation with grain filling of super rice was analyzed with four super rice cultivars, Liangyoupeijiu and ]1 you 084 （indica hybrids）, Huaidao 9 and Wujing 15 （japonica）, and two high-yielding and elite check cultivars, Shanyou 63 （indica hybrid） and Yangfujing 8 （japonica）as material in paddy field. Activities of sucrose synthase （SuSase）, adenosine diphosphoglucose pyrophosphorylase （AGPase）, starch synthase （StSase）, and starch branching enzyme （SBE） and contents of zeatin -- zeatin riboside （Z＋ZR）, indole-3- acetic acid （IAA）, abscisic acid （ABA） in superior and inferior spikelets were determined during the grain filling period and their relationships with grain filling rate were analyzed. Maximum grain filling rate, the time reaching a maximum grain-filling rate, mean grain filling rate and brown rice weight for superior spikelets slightly differed between super rice and elite check rice, but those for inferior spikelets were significantly different between super rice and check rice cuhivars. Changes in enzyme activity and contents of hormones in grains followed single peak curves during the grain filling period. The peak and mean activity of SuSase, AGPase, StSase and SBE were lower in inferior spikelets than in superior ones,as well as the peak and mean contents of Z＋ZR, IAA and ABA. The peak and mean contents of ABA were significantly greater in inferior spikelets than in superior ones and greater in the super rice than in the check rice. The grain filling rate was positively significantly correlated with the activities of SuSase, AGPase and StSase and con- tents of Z＋ZR and IAA, but not significantly correlated with activity of SBE and ABA contents. The results suggested that the low activities of SuSase, AGPase and StSase and low contents of Z＋ZR and IAA may be an important reason for