The source-sink relationship is key to overall crop performance. Detailed understanding of the factors that determine source-sink dynamics is imperative for the balance of biomass and grain yield in crop plants. We investigated the differences in the source-sink relationship between a cultivated rice Oryza sativa cv. Nipponbare and a wild rice Oryza australiensis that show striking differences in biomass and grain yield. Oryza australiensis, accumulating higher biomass, not only showed higher photosynthesis per unit leaf area but also exported more sucrose from leaves than Nipponbare. However, grain features and sugar levels suggested limited sucrose mobilization to the grains in the wild rice due to vasculature and sucrose transporter functions. Low cell wall invertase activity and high sucrose synthase cleavage activity followed by higher expression of cellulose synthase genes in Oryza australiensis stem utilized photosynthates preferentially for the synthesis of structural carbohydrates, resulting in high biomass. In contrast, the source-sink relationship favored high grain yield in Nipponbare via accumulation of transitory starch in the stem, due to higher expression of starch biosynthetic genes, which is mobilized to panicles at the grain filling stage. Thus, vascular features, sucrose transport, and functions of sugar metabolic enzymes explained the differences in the source-sink relationship between Nipponbare and Oryza australiensis.

中文翻译：

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蔗糖转运和代谢控制水稻茎秆和谷物之间的碳分配

源库关系是整体作物生长的关键。对决定源库动态的因素的详细了解对于作物中生物量和谷物产量的平衡至关重要。我们调查了栽培稻Oryza sativa cv之间源库关系的差异。在生物量和谷粒产量上表现出明显差异的日本are和野生稻Australiensis。澳洲稻积累更高的生物量，不仅显示出每单位叶面积更高的光合作用，而且从叶片中输出的蔗糖比日本晴更多。然而，由于脉管系统和蔗糖转运蛋白的功能，谷物的特征和糖水平表明蔗糖只能运用于野生稻中的谷物。低细胞壁转化酶活性和高蔗糖合酶裂解活性，随后纤维素合成酶基因在稻米中表达更高茎优先利用光合产物来合成结构性碳水化合物，从而产生高生物量。相反，由于淀粉生物合成基因的高表达，在谷粒灌浆期动员到穗上，源库关系通过暂态淀粉在茎中的积累，有利于日本晴中的高谷产量。因此，血管特征，蔗糖转运和糖代谢酶的功能解释了日本晴与澳大利亚稻之间源库关系的差异。