Nogués Salvador, Aranjuelo Iker, Pardo Antoni, Azcón-Bieto Joaquim
Unitat de Fisiologia Vegetal, Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal, 645, Barcelona, Spain.
Rapid Commun Mass Spectrom. 2008 Apr;22(7):1017-22. doi: 10.1002/rcm.3460.
Most of the literature focused on internal CO(2) (Ci) determinations in plants has used indirect methods based on gas-exchange estimations. We have developed a new method based on the capture of internal air gas samples and their analysis by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). This method provided a direct measure of intercellular CO(2) concentrations combined with stable carbon isotopic composition in O. ficus-indica plants. Plants were grown at both ambient and elevated CO(2) concentration. During the day period, when the stomata are closed, the Ci was high and was very (13)C-enriched in both ambient and elevated CO(2)-grown plants, reflecting Rubisco's fractionation (this plant enzyme has been shown to discriminate by 29 per thousand, in vitro, against (13)CO(2)). Other enzyme fractionations involved in C metabolism in plants, such as carbonic anhydrase, could also be playing an important role in the diurnal delta(13)C enrichment of the Ci. During the night, when stomata are open, Ci concentrations were higher in elevated (and the corresponding delta(13)C values were more (13)C-depleted) than in ambient CO(2)-grown plants.
大多数关注植物内部二氧化碳（Ci）测定的文献都采用了基于气体交换估算的间接方法。我们开发了一种基于采集内部空气气体样本并通过气相色谱 - 燃烧 - 同位素比率质谱法（GC - C - IRMS）进行分析的新方法。该方法直接测量了霸王鞭植物细胞间二氧化碳浓度及其稳定碳同位素组成。植物分别在环境二氧化碳浓度和高二氧化碳浓度条件下生长。在白天气孔关闭期间，Ci值较高，且在环境二氧化碳浓度和高二氧化碳浓度条件下生长的植物中，Ci都高度富集了碳 - 13，这反映了核酮糖 - 1,5 - 二磷酸羧化酶（Rubisco）的分馏作用（这种植物酶在体外已被证明对碳 - 13二氧化碳的歧视率为29‰）。植物碳代谢中涉及的其他酶的分馏作用，如碳酸酐酶，也可能在Ci的日变化δ¹³C富集过程中发挥重要作用。在夜间气孔开放时，高二氧化碳浓度条件下生长的植物的Ci浓度更高（相应的δ¹³C值更贫碳 - 13），高于环境二氧化碳浓度条件下生长的植物。
