依据着粒密度，对江淮稻区大面积生产应用的和新近育成的36个粳稻品种(系)进行聚类分析。结果表明，供试品种可分成半密穗型(Ⅰ)、偏密穗型(Ⅱ)和密穗型（Ⅲ）三类。随着水稻品种由散穗型向半密穗型、偏密穗型和密穗型的演变，产量性状、品质性状、形态性状和部分生理、生化性状发生了明显的变化，产量、每穗总粒数和实粒数显著增加，而穗数/m2、千粒重和结实率呈下降趋势；株高增加，上部三张叶片变长、变宽，生物日产量增高；穗部一、二次枝梗数增多，着粒密度变大；抽穗期和成熟期叶片、茎秆的含氮量和叶片叶绿素含量增高；糙米率和整精米率下降、垩白粒率降低、胶稠度变硬、蛋白质含量呈上升的趋势。
Thirty six japonica cultivars bred in Jiang-Huai area were categorized into three groups with semi-dense panicle, near-dense panicle and dense panicle by clustering analysis, based on panicle grain density. With the panicle type changing from thin panicle to semi-dense panicle and dense panicle the rice cultivars were changed as follows: total grain numbers and filled grain numbers per panicle, the diurnal yield were improved significantly while panicle numbers/m2, 1000-grain-weight and the percentage of filled grains declined; plant height was increased, top three leaves became longer and wider, biological production per day was increased; the first and second branches of the panicle and grain density were increased; some values of physiological character were increased, such as nitrogen content and chlorophyll content of leaf, and nitrogen content of stem during heading and maturity stages; As to some grain quality characters, the rate of brown rice and head milled rice, chalkiness rate were decreased, gel consistency became rigid and protein content was increased.
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