稻穗颖花开花时间对胚乳发育的影响及其生理机制

武育粳3号（粳稻）、扬稻4号（籼稻）、汕优63（籼型杂交稻）和PC311/早献党18（籼粳杂交稻）一个穗上颖花开花经历的时间分别为5d、7d、7d和8d。胚乳细胞数（ECs）以第2天开花的籽粒最多,其次为第1天开花的籽粒,以后随开花时间的推迟,ECs减少。同一品种（组合）不同开花时间籽粒的单个胚乳细胞重差异不大。胚乳重和谷粒充实率与ECs呈极显著正相关，与单个胚乳细胞的重量相关不显著。开花越早的籽粒（第1天开花的籽粒除外），胚乳细胞的起始增殖势（R#+0）、最大增殖速率[V#-（max）]和平均增殖速率（V*+-）越大，到达最大增殖速率的时间越短。R#+0、V#-（max）、V*+-和ECs与灌浆初期的籽粒生理活性（ATP酶活性、亚精胺和精胺含量）密切相关。孕穗期去1/2植株或始穗期喷施6-BA[6-（苄基）腺嘌呤]，灌浆初期的籽粒生理活性、R#+0、V#-（max）、V*+-、ECs、胚乳重和谷粒充实率明显增加，孕穗期去1/2叶后，结果则相反。表明由于ECs的不同，造成了穗上籽粒间粒重的差异，而迟开花籽粒的生理活性低是其胚乳发育不良的重要原因。

Effects of Flowering Time of Spikelets on Endosperm Development in Rice and Its Physiological Mechanism

The flowering duration of spikelets in the rice cultivars Wuyujing 3 ( Japonica ), Yangdao 4( Indica ),Shanyou 63 ( Indica hybid rice ) and PC311/Zaoxiandang 18 ( Japonica/Indica hybrid rice ) was 5d,7d,7d and 8d, respectively. The spikelets flowered on the 2nd day produced the highest endosperm weight (EW) and highest number of endosperm cells (ECs). The spikelets flowered on the 1st day had the second highest EW and number of ECs. The ECs decreased with the delay of flowering on the spikelets flowered on the 3rd day. Within a variety or a hybrid combination,the difference of the weight of an endosperm cell was not significant among the grains flowered on different dates.EW and grainfilled percentage (GFP) were very significantly correlated with ECs, and had no significant correlation with the weight of an endosperm cell. The earlier the spikelets flowered (except those flowered on the 1st day),the greater the initial proliferation power (R0),the maximum proliferation rate (Vmax) and a mean proliferation rate( ) of ECs were,and the shorter the time reaching Vmax was, and vice versa. R0, Vmax, and ECs were significantly correlated with the physiological activities(ATPase activity and the content of spermidine and spermine) of the grains in early grain filling period. The physiological activities of the grains, R0,Vmax, , ECs and EW increased significantly after removing 1/2 plants at booting stage and spraying 6BAN6(benzyl) adenine at early heading,and the results were reversed after cutting 1/2 leaves at booting stage. These results suggested that the difference of ECs caused the difference of the grain weight, and the low physiological activities of lateflowered grains was the important reasons for their poor endosperm development.