In many parts of the world, solar radiation has decreased during the past 50 years due to industrialisation‐induced elevations in air aerosols which has negatively impacted crop productivity. Climate change threatens rapeseed (Brassica napus L.) production due to shade stress caused by reduced light radiation. However, studies on how shade affects photosynthetic mechanisms in rapeseed (leaves and pod wall) are not well documented. Understanding the mechanisms of shade on yield formation in rapeseed is important for breeding shade‐tolerant rapeseed varieties and optimising agricultural management practices in low‐light areas. Therefore, this study assesses the impacts of ‘global dimming’ simulated by shading at a specific period on rapeseed's photosynthetic behaviour, yield and seed quality. A two‐factor split‐plot design was arranged with three shading treatments (CK, FS and PS) and two hybrid genotypes (Chuannong and Zhongyouza) of rapeseed. We observed that shading at the flowering stage (FS) significantly inhibited the leaf area index, chlorophyll content, photosynthetic efficiency and enzymatic activities of both genotypes. Besides that, shading at pod development stage (PS) substantially declined the pod photosynthetic characteristics and transportation of carbohydrates towards economic organ (seeds) which directly decreased the yield of rapeseed. We found that PS treatment remarkably declined the oil content of both genotypes. According to the results, the photosynthetic capacity of rapeseed pod wall had a greater impact on yield and seed quality than leaves. Therefore, improving the photosynthetic capacity and material transport efficiency of the pod wall is a potential measure to increase the yield of rapeseed under shade stress. This study provides a new insight into the effects of shade on rapeseed production and provides a valuable reference for rapeseed breeding techniques to develop high‐yielding genotypes by enhancing the photosynthetic efficiency of rapeseed pod wall in low‐light conditions.

中文翻译：

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特定生长阶段的弱光影响甘蓝型油菜的光同化物运输、种子质量和产量。


在世界许多地方，由于工业化导致空气中气溶胶含量升高，过去 50 年来太阳辐射有所减少，这对作物生产力产生了负面影响。由于光辐射减少造成遮荫胁迫，气候变化威胁着油菜籽 (Brassica napus L.) 的生产。然而，关于遮荫如何影响油菜籽（叶子和豆荚壁）光合作用机制的研究还没有很好的记录。了解遮荫对油菜产量形成的机制对于培育耐荫油菜品种和优化弱光地区的农业管理实践具有重要意义。因此，本研究评估了特定时期遮荫模拟的“全球变暗”对油菜籽光合行为、产量和种子质量的影响。采用双因素裂区设计，对油菜进行三种遮荫处理（CK、FS 和 PS）和两种杂交基因型（川农和中油杂）。我们观察到开花期（FS）的遮荫显着抑制了两种基因型的叶面积指数、叶绿素含量、光合效率和酶活性。此外，荚果发育阶段（PS）的遮荫大大降低了荚果的光合特性和碳水化合物向经济器官（种子）的运输，直接降低了油菜的产量。我们发现 PS 处理显着降低了两种基因型的含油量。结果表明，油菜荚壁的光合能力对产量和种子品质的影响大于叶片。因此，提高豆荚壁的光合能力和物质运输效率是遮荫胁迫下油菜增产的潜在措施。 该研究为揭示遮荫对油菜产量的影响提供了新的见解，并为油菜育种技术通过提高弱光条件下油菜荚壁的光合效率来开发高产基因型提供了有价值的参考。