以杂交粳稻‘花优14’为试验材料,在机械直播下研究了播种密度对水稻群体冠层光合有效辐射(PAR)分布和产量构成的影响.结果表明:在水稻生长中后期,群体冠层叶面积指数(LAI)、光合有效辐射截获量(IPAR)及PAR截获率与密度呈正向趋势,各层级冠层自下而上逐渐递减,并随生育进程延续而逐渐降低.群体冠层底部光合有效辐射(TPAR)与密度呈负向趋势,同密度群体冠层TPAR自下而上呈递增趋势.在相同播种密度条件下,各层级水稻群体冠层TPAR与LAI呈现对数关系,Y=-1.49 ln(x)+10.27(腊熟期),R2=0.9965**.在本试验密度处理范围内,密度与单位面积内有效穗数呈正向趋势,而与千粒重存在负向趋势,与穗粒数和产量呈现二次曲线关系.水稻精量穴直播的密度以行穴距20 cm×16 cm,孕穗期群体基部冠层PAR截获率控制在95.0％左右,有效穗数为283.7万/hm2,则获得较高穗粒数,稻谷产量可突破10 500 kg/hm2水平.%Field experiments with keng rice variety'Huayou 14'were carried out under mechanical spot seeding to study the population canopy's photosynthetically active radiation (PAR)distribution and grain yield as influenced by seeding densities.The results showed that in the mid/late period of rice growth,the population canopy's leaf area index (LAI),interception of photosynthetically active radiation (IPAR) and PAR interception rate were positively correlated with the seeding density,gradually decreased from bottom to top in all layers of population canopy and also declined with the growth process.The photosynthetically active radiation at bottom of population canopy (TPAR)was negatively correlated with the seeding density and gradually increased from bottom to top in the whole population canopy in the same density.Under the same seeding density the TPAR and LAI presented a logarithmic function relation:Y =-1.49 ln (x) + 10.27 (wax-ripe stage),R2 =0.9965 **.In the experiments,the seeding density was correlated positively with the effective panicle number per unit area and negatively with the 1 000-grain weight,and presented a quadratic function relation with the grain number per spike and yield.A greater grain number per spike could reach and the grain yield could be over 10 500 kg/hm2 when the seeding density was 20 cm × 16 cm,the population basal canopy's PAR interception rate was about 95％ at the booting stage and the effective panicle number was 2 837 000/hm2.
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