This study aimed to understand the response of photosynthesis and growth to e-CO2 conditions (800 vs. 400 μmol mol-1 ) of rice genotypes differing in source-sink relationships. A proxy trait called local C source-sink ratio was defined as the ratio of flag leaf area to the number of spikelets on the corresponding panicle, and five genotypes differing in this ratio were grown in a controlled greenhouse. Differential CO2 resources were applied either during the 2 weeks following heading (EXP1) or during the whole growth cycle (EXP2). Under e-CO2 , low source-sink ratio cultivars (LSS) had greater gains in photosynthesis, and they accumulated less nonstructural carbohydrate in the flag leaf than high source-sink ratio cultivars (HSS). In EXP2, grain yield and biomass gain was also greater in LSS probably caused by their strong sink. Photosynthetic capacity response to e-CO2 was negatively correlated across genotypes with local C source-sink ratio, a trait highly conserved across environments. HSS were sink-limited under e-CO2 , probably associated with low triose phosphate utilization (TPU) capacity. We suggest that the local C source-sink ratio is a potential target for selecting more CO2 -responsive cultivars, pending validation for a broader genotypic spectrum and for field conditions.

中文翻译：

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源和汇性状的基因型变化影响光合作用和生长对大气CO2升高的响应。

这项研究旨在了解光合和生长对不同源-库关系的水稻基因型的e-CO2条件（800 vs. 400μmolmol-1）的响应。将称为局部碳源-吸收比的代用性状定义为旗叶面积与相应穗上小穗数的比值，并在受控温室中种植该比例不同的五种基因型。在抽穗后的两周内（EXP1）或整个生长周期（EXP2）均施用了不同的CO2资源。在e-CO2下，低源/库比品种（LSS）的光合作用增加，并且与高源/库比品种（HSS）相比，它们在旗叶中积累的非结构碳水化合物较少。在EXP2中，LSS的谷物产量和生物量增加也较大，这可能是由于它们强烈的下沉。不同基因型对e-CO2的光合能力响应与局部碳源-吸收比呈负相关，局部碳源-吸收比在整个环境中高度保守。HSS在e-CO2下受汇的限制，这可能与磷酸三甘油酯利用率（TPU）容量低有关。我们建议，本地C源库比是选择更多CO2响应品种的潜在目标，尚待验证更广泛的基因型谱和田间条件。