Ecologie Systématique Evolution, Bâtiment 362, Université Paris-Sud 11, 91405 Orsay cedex, Paris, France.
Plant Cell Environ. 2010 Jun;33(6):900-13. doi: 10.1111/j.1365-3040.2010.02115.x. Epub 2010 Jan 15.
While there is currently intense effort to examine the (13)C signal of CO(2) evolved in the dark, less is known on the isotope composition of day-respired CO(2). This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure c(i)/c(a) effect) from respiratory effect (production of CO(2) with a different delta(13)C value from that of net-fixed CO(2)) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO(2)]. We show that whole mesocosm-respired CO(2) is slightly (13)C depleted in the light at the mesocosm level (by 0.2-0.8 per thousand), while it is slightly (13)C enriched in darkness (by 1.5-3.2 per thousand). The turnover of the respiratory carbon pool after labelling appears similar in the light and in the dark, and accordingly, a hierarchical clustering analysis shows a close correlation between the (13)C abundance in day- and night-evolved CO(2). We conclude that the carbon source for respiration is similar in the dark and in the light, but the metabolic pathways associated with CO(2) production may change, thereby explaining the different (12)C/(13)C respiratory fractionations in the light and in the dark.
虽然目前人们正在努力研究黑暗中 CO2 释放的 (13)C 信号，但对日间呼吸 CO2 的同位素组成却知之甚少。这种知识的缺乏源于测量纯呼吸同位素信号的技术困难：日间呼吸与光呼吸混合在一起，而且在生态系统水平上，没有明显的方法可以将光合作用分馏（纯 c(i)/c(a 效应）与呼吸作用（产生与净固定 CO2 不同的 δ(13)C 值的 CO2）区分开来。在这里，我们利用新的简单方程，并将其应用于在低和高 [CO2] 下生长的向日葵冠层。我们表明，整个中观呼吸 CO2 在中观水平上（约 0.2-0.8‰）在光下略微（13)C 贫化，而在黑暗中略微（13)C 富集（约 1.5-3.2‰）。标记后呼吸碳库的周转似乎在光下和黑暗中相似，因此，层次聚类分析显示日间和夜间释放的 CO2 中（13)C 丰度密切相关。我们得出结论，黑暗中和光下呼吸的碳源相似，但与 CO2 产生相关的代谢途径可能会发生变化，从而解释了光下和黑暗中不同的（12)C/(13)C 呼吸分馏。
