One of the major challenges facing rice breeding is to produce ideotype or ideal plant architecture (IPA) to improve canopy radiation use efficiency and hence grain yield. The hybrid japonica rice Jiayou Zhongke 6 (JYZK-6) is one of the benchmark cultivars with IPA characteristics, but the physio-ecological foundation of its high yield potential is still imperfectly understood. In this study, two-year field experiments were conducted using four japonica rice cultivars including JYZK-6 with contrasting canopy structures. A dynamic canopy light interception simulating device was constructed to capture canopy images representing the diurnal dynamics of solar angles throughout the grain-filling stage. Subsequently, leaf to panicle ratio (LPR), a newly developed physiological trait indicative of source-sink relations, was exploited to quantify the light distribution pattern within the rice canopy. The LPRs with high spatio-temporal resolution clearly showed the diurnal changes of light interception within the rice canopy. Genotypic differences in diurnal pattern of LPR were detected among the tested cultivars in both growing seasons, with the amplitude varying with grain-filling stages. Notably, LPR of the IPA cultivar JYZK-6 and its analogue WYJ-29, had a pattern of a V-shaped graph, peaking at sunrise and sunset while dropping to the lowest at noon during middle and late stages. Morphological measurement showed that the V-shaped pattern was associated with the height difference between flag leaf and panicle, panicle curvature, ratio of leaf area to panicle area, as well as the changing solar angles along with the progression of growth stage. This distinguishing feature of light pattern indicates that within the canopy of IPA cultivars, the leaf receives more light in the morning and afternoon whereas the panicle harvests more light at noon. It is inferred that such novel characteristics may provide the IPA cultivar with advantages of reducing midday suppression over the conventional cultivars, while more work is needed to verify this hypothesis. In summary, findings of this study offer a deeper insight into the physio-ecological processes underpinning radiation use efficiency at canopy level, and hence are valuable for breeding programs for ideotype cultivars.

水稻育种面临的主要挑战之一是产生理想型或理想植物结构 (IPA) 以提高冠层辐射利用效率，从而提高粮食产量。杂交粳稻嘉油中科6号（JYZK-6）是具有IPA特性的标杆品种之一，但其高产潜力的生理生态基础尚不完全清楚。在这项研究中，使用四株粳稻进行了为期两年的田间试验。包括 JYZK-6 在内的水稻品种具有对比鲜明的冠层结构。构建了一个动态树冠遮光模拟装置来捕捉树冠图像，该图像代表整个谷物灌浆阶段的太阳角的昼夜动态。随后，叶穗比 (LPR) 是一种新开发的指示源库关系的生理特征，被用来量化水稻冠层内的光分布模式。具有高时空分辨率的 LPR 清楚地显示了水稻冠层内光拦截的日变化。在两个生长季节的测试品种之间检测到LPR昼夜模式的基因型差异，其幅度随灌浆阶段而变化。值得注意的是，IPA 品种 JYZK-6 及其类似物 WYJ-29 的 LPR 具有 V 形图的模式，在日出和日落时达到峰值，在中后期下降到中午最低。形态学测量表明，V形图案与旗叶与穗高差、穗曲率、叶面积与穗面积之比、太阳角随生长阶段的变化有关。这种光模式的显着特征表明，在 IPA 品种的树冠内，叶子在上午和下午接收更多的光，而穗在中午收获更多的光。据推测，这些新特性可能为 IPA 品种提供了比传统品种减少午间抑制的优势，但需要更多的工作来验证这一假设。总之，