Rising atmospheric CO₂ concentrations stimulate photosynthesis and productivity of C3 plants such as rice (Oryza sativa L.), a phenomenon known as the CO₂ fertilization effect (CFE). Previous studies have shown that a greater sink capacity (e.g. grain number, or grain size) enhances the CFE on rice yield and that cytokinin is involved in the sink capacity; however, the direct involvement of this phytohormone in the CFE remains unclear. In this study, we tested whether exogenous application of kinetin improved the CFE of cultivars with different sink sizes (Koshihikari, japonica, with small sink; Takanari, indica with large sink) using a free-air CO₂ enrichment experiment on a rice paddy. We hypothesized that kinetin increases the sink size and thereby enhances the CFE, particularly for the cultivar with a smaller sink. Elevated CO₂ (200 Âµmol/mol above ambient concentration) increased grain yield by 11.4%, averaged across two cultivars. Kinetin significantly improved the CFE in Takanari from 11.2% to 19.2%, but not in Koshihikari. The enhancement of the CFE by kinetin in Takanari appeared through the increased sink size resulting from a greater panicle density. In contrast, kinetin did not increase panicle density or sink size in Koshihikari and failed to enhance the CFE. We therefore conclude that sink size improves CFE on rice yield, and that kinetin could increase sink size, but the effect is cultivar dependent.

中文翻译：

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叶面喷动素对CO 2浓度升高对水稻产量的影响

上升大气CO ₂浓度的刺激C3植物例如稻（光合作用和生产率稻L.），被称为CO的现象₂施肥效果（CFE）。先前的研究表明，更大的库容（例如，粒数或粒度）可以提高水稻产量的CFE，而细胞分裂素则参与了细胞分裂素的调控。然而，尚不清楚这种植物激素是否直接参与CFE。在这项研究中，我们测试了通过自由空气CO _2的外源施用激动素是否改善了不同水槽大小（越光，粳稻，小水槽；高田奈（d），大水槽）的栽培品种的CFE。水稻的富集实验。我们假设激动素增加了接收器的大小，从而提高了CFE，特别是对于接收器较小的品种。升高的CO ₂（比环境浓度高200 µmol / mol）将谷物产量平均提高了11.4％，这是两个品种的平均水平。Kinetin将Takanari的CFE从11.2％显着提高到19.2％，但在Koshihikari中则没有。通过增加穗密度导致的接收器尺寸增加，出现了运动因子在Takanari中对CFE的增强作用。相反，激动素在越光中并未增加穗密度或穗大小，也未能增强CFE。因此，我们得出的结论是，水槽大小可提高CFE对水稻产量的影响，而激动素可增加水槽大小，但其影响取决于品种。