目的 研究晚籼杂交稻单株穗数、叶面积指数(Leaf area index，LAI)、叶片SPAD和透光率(Light transmittance rate，LTR)等指标的动态变化，进一步明确它们之间的相互关系及其对杂交稻产量和产量性状的影响，为杂交水稻育种和生产实践提供理论指导。方法 以华南地区广泛应用的5个三系不育系和6个恢复系配置杂交组合，于2021年晚季在广州进行27个杂交组合的随机区组试验，分析杂种光合参数的动态变化规律以及不同发育阶段各光合参数对产量及产量性状的影响及相关性。结果 杂种茎蘖数自移栽后直线上升，于移栽后25 d达分蘖高峰，始穗期(移栽后60 d)进入平稳期；杂种LAI自移栽后快速上升，于幼穗分化后期(移栽后50 d)后达最高值，之后进入回落期；叶片SPAD自移栽后逐步走低，生长发育前期组合间叶片SPAD差异不明显，进入灌浆结实期后存在显著(P < 0.05)或极显著(P < 0.01)差异；杂种群体LTR随发育进程呈逐步下降趋势。相关分析表明：分蘖盛期前(移栽后10~20 d)以及始穗期至灌浆期(移栽后60~76 d)的单株茎蘖数与杂种产量呈极显著正相关，增产作用主要通过增加单株实粒数实现；分蘖盛期至幼穗分化后期(移栽后25~50 d)的茎蘖数过多，增加了杂种群体的无效分蘖，造成杂种结实率下降和产量显著降低；分蘖前期(移栽后20 d)和始穗期(移栽后60 d)杂种LAI与产量呈极显著和显著正相关，相关系数分别为0.296和0.255，增产作用主要通过提高单株实粒数和千粒质量实现；灌浆期(移栽后76 d)的LAI与产量呈极显著负相关，相关系数为-0.312；生育前期(移栽后15~50 d)杂种SPAD对产量具有显著或极显著增产效应，而灌浆结实期(移栽后76~90 d)的SPAD则造成极显著减产；杂种群体LTR与产量呈极显著负相关，分蘖前期(移栽后20 d)和幼穗分化前期(移栽后38 d)的LTR与产量的相关系数分别为-0.282和-0.384。结论 ‘天丰A’‘五丰A’‘广恢998’和‘广恢308’组合的前期分蘖力强，茎蘖数多，叶面积系数大，早生快发性好；‘扬泰A’‘广恢998’等组合前期LTR较低、后期较高，有利于植株光合作用和产量提高。在不同生长发育阶段，光合参数通过影响杂种的不同产量性状，实现对杂种产量的影响。通过光合参数与杂种产量回归方程的拟合，能较好地对杂交水稻早期产量进行预测。
Objective The study aims to analyze the dynamic changes of panicles per plant, leaf area index (LAI), leaf SPAD, and light transmittance rate (LTR) in late-season indica hybrid rice, further clarify their interrelationships and their effects on yield and yield-related traits, and provide a theoretical guidance for hybrid rice breeding and production practice.Method Five three-line sterile lines and six restorer lines, which are widely used in South China, were used as hybrid combination parents, and a random block experiment of 27 hybrid combinations was conducted in Guangzhou in the late season of 2021. The dynamic changes of photosynthetic parameters, the effects of photosynthetic parameters at different growth and development stages on yield and yield-related traits, and their dynamic correlation were studied. Result The number of hybrid tillers increased linearly after transplantation, peaked on 25 d after transplantation, and entered a stable period at the initial heading stage (60 d after transplanting). The hybrid LAI rapidly increased after transplanting, reaching its highest value at the late stage of spike differentiation (50 d after transplanting), and then entered a decline period. The leaf SPAD of hybrids gradually decreased after transplantation, and there was no significant difference at the early growth and development stage, while there was significant (P < 0.05) or extremely significant (P < 0.01) differences between the SPAD at the grain-filling stage. The LTR of hybrid populations decreased gradually with the development process. The correlation analysis showed that there was a highly significant positive correlation between the number of tillers per plant and hybrid yield at peak tillering stage (10−20 d after transplanting), initial heading stage (60 d after transplanting), and grain-filling stage (76 d after transplanting). The yield increase effect was mainly achieved by increasing the number of filled grains per plant. The excessive number of tillers during peak tillering stage to the late stage of spike differentiation (25−50 d after transplanting) increased the ineffective tillers, resulted in a decrease in hybrid seed setting rate and a significant decrease in yield. The hybrid LAI value at tilering stage (20 d after transplanting) and initial heading stage (60 d after transplanting) showed a significant or extremely significant positive correlation with yield, with the correlation coefficients of 0.296 and 0.255, respectively. The yield increase effect were mainly achieved by increasing the number of filled grains per plant and the weight of 1000-grain. The LAI value at grain-filling stage (76 d after transplanting) showed a highly significant negative correlation with yield with the correlation coefficient of -0.312. The SPAD of hybrids at the early stage of growth (15−50 d after transplanting) had a significant or extremely significant increase in yield, while the SPAD value in the later stage (76−90 d after transplanting) caused a very significant decrease in yield. The LTR of hybrid populations showed extremely significant negative correlation with their yield, the correlation coefficients between LTR and yield at tillering stage (20 d after transplanting), and early stage of spike differentiation (38 d after transplanting) were -0.282 and -0.384, respectively.Conclusion The combinations derived from ‘Tianfeng-A’, ‘Wufeng-A’, ‘R998’ and ‘R308’ have strong early tillering ability, a large number of stem tillers, a large LAI, and good early growth and rapid development. The combinations of ‘Yangtai-A’ and ‘R998’ show a lower LTR in the early growing stage and a higher LTR in the later stage, which is much beneficial for plant photosynthesis and yield improvement. The yield of hybrids is affected by photosynthetic parameters at different stages of growth and development, through influencing the different yield traits. By fitting the regression equation between photosynthetic parameters and hybrid yield, the yield of hybrids can be well predicted at early growing stage.