Ascorbate is an antioxidant in plants. Its content is an important index to evaluate the nutritional quality of celery. In higher plant, ascorbate accumulation is effected by CO2 concentration. To study the effects of elevated CO2 (1000 µmol mol−1) on ascorbate accumulation in celery, ascorbate contents and the transcript levels of genes related to ascorbate metabolism in the leaves (leaf blade and petiole) were detected. The results of current study showed that the ascorbate and total ascorbate levels increased during all the treated stages in celery petioles, and they were 1.09–3.91 fold of the control. In leaf blades, the ascorbate contents exhibited a lower level (96.12% and 90.46% of the control) in treatments at 2 and 4 days, and then increased to 1.04 and 1.27 fold of the control in treatments at 6 and 8 days, respectively. Elevated CO2 altered the expression profiles of ascorbate-related genes and the activities of corresponding enzymes. Expression levels of the genes, AgPGI2, AgGMP, AgPMI, AgGalDH, AgGalLDH, GalUR, AgDHAR1, AgAPX1, and AgAO, in the leaf blades corresponded well to the change in ascorbate contents. At 6 days of treatment, the relative expression levels of AgPGI2, AgPMI, AgGGP1, AgGGP2, AgGalUR, AgMDHAR, AgDHAR1, and AgAPX1 in leaf blades increased, and were 4.41, 2.39, 4.65, 3.64, 3.11, 4.53, 4.59, and 3.86 times higher than that of the control. Increased ascorbate accumulation in celery leaves under elevated CO2 treatments might be also related to the change in SOD, POD, and CAT activities, as well as GSH content. These results will enhance our understanding on the effects of elevated CO2 on ascorbate accumulation and potential molecular mechanism regulating ascorbate metabolism in celery.

中文翻译：

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二氧化碳浓度升高对芹菜抗坏血酸积累和抗坏血酸代谢相关基因表达水平的影响

抗坏血酸是植物中的抗氧化剂。其含量是评价芹菜营养品质的重要指标。在高等植物中，抗坏血酸的积累受 CO2 浓度的影响。为了研究升高的 CO2（1000 µmol mol-1）对芹菜中抗坏血酸积累的影​​响，检测了抗坏血酸含量和叶片（叶片和叶柄）中与抗坏血酸代谢相关基因的转录水平。目前的研究结果表明，在所有处理阶段，芹菜叶柄的抗坏血酸和总抗坏血酸水平均增加，是对照的 1.09-3.91 倍。在叶片中，抗坏血酸含量在第 2 天和第 4 天的处理中表现出较低的水平（对照的 96.12% 和 90.46%），然后在第 6 天和第 8 天的处理中分别增加到对照的 1.04 和 1.27 倍。升高的二氧化碳改变了抗坏血酸相关基因的表达谱和相应酶的活性。叶片中基因 AgPGI2、AgGMP、AgPMI、AgGalDH、AgGalLDH、GalUR、AgDHAR1、AgAPX1 和 AgAO 的表达水平与抗坏血酸含量的变化很好地对应。处理6天时，叶片中AgPGI2、AgPMI、AgGGP1、AgGGP2、AgGalUR、AgMDHAR、AgDHAR1和AgAPX1的相对表达水平升高，分别为4.41、2.39、4.65、3.64、3.11、4.593、4.586和4.58。比对照高出数倍。在升高的 CO2 处理下芹菜叶片中抗坏血酸积累的增加也可能与 SOD、POD 和 CAT 活性以及 GSH 含量的变化有关。