Relatively few studies have been focused so far on magnesium–isotope fractionation during plant growth, element uptake from soil, root-to-leaves transport and during chlorophylls biosynthesis. In this work, maize and garden cress were hydroponically grown in identical conditions in order to examine if the carbon fixation pathway (C4, C3, respectively) might have impact on Mg-isotope fractionation in chlorophyll-a. The pigment was purified from plants extracts by preparative reversed phase chromatography, and its identity was confirmed by high-resolution mass spectrometry. The green parts of plants and chlorophyll-a fractions were acid-digested and submitted to ion chromatography coupled through desolvation system to multiple collector inductively coupled plasma-mass spectrometry. Clear preference for heavy Mg-isotopes was found in maize green parts (∆26Mgplant-nutrient 0.65, 0.74 for two biological replicates, respectively) and in chlorophyll-a (∆26Mgchlorophyll-plant 1.51, 2.19). In garden cress, heavy isotopes were depleted in green parts (∆26Mgplant-nutrient (−0.87)–(−0.92)) and the preference for heavy isotopes in chlorophyll-a was less marked relative to maize (∆26Mgchlorophyll-plant 0.55–0.52). The observed effect might be ascribed to overall higher production of energy in form of adenosine triphosphate (ATP), required for carbon fixation in C4 compared to C3, which could reduce kinetic barrier and make equilibrium fractionation prevailing during magnesium incorporation to protoporphyrin ring.

中文翻译：

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从具有不同固碳途径的两种植物中提取的叶绿素-a 中的镁-同位素分馏（C3、C4）

迄今为止，相对较少的研究集中在植物生长过程中镁同位素分馏、土壤元素吸收、根到叶运输以及叶绿素生物合成过程中。在这项工作中，玉米和水芹在相同的条件下水培生长，以检查碳固定途径（分别为 C4、C3）是否可能对叶绿素 a 中的镁同位素分馏产生影响。通过制备型反相色谱法从植物提取物中纯化色素，并通过高分辨率质谱法确认其身份。植物的绿色部分和叶绿素-a 部分被酸消化，并通过去溶剂系统进行离子色谱耦合到多收集器电感耦合等离子体质谱。在玉米绿色部分（两个生物重复的Δ26Mgplant-营养物分别为0.65、0.74）和叶绿素-a（Δ26Mg叶绿素植物1.51、2.19）中发现了对重Mg同位素的明显偏好。在花园水芹中，绿色部分的重同位素耗尽（Δ26Mgplant-营养物（-0.87）-（-0.92））并且相对于玉米（Δ26Mg叶绿素-植物0.55-0.52），叶绿素-a中重同位素的偏好不太明显）。观察到的效果可能归因于以三磷酸腺苷 (ATP) 形式产生的总体更高的能量，与 C3 相比，C4 中的碳固定所需的能量更高，这可以降低动力学障碍并使平衡分馏在镁掺入原卟啉环期间占主导地位。51, 2.19)。在花园水芹中，绿色部分的重同位素耗尽 (Δ26Mgplant-营养 (-0.87)–(-0.92)) 并且相对于玉米 (Δ26Mg 叶绿素-植物 0.55-0.52)，叶绿素-a 中重同位素的偏好不那么明显）。观察到的效果可能归因于以三磷酸腺苷 (ATP) 形式产生的整体更高的能量，与 C3 相比，C4 中的碳固定是必需的，这可以降低动力学障碍并使平衡分馏在镁掺入原卟啉环期间占主导地位。51, 2.19)。在花园水芹中，绿色部分的重同位素耗尽 (Δ26Mgplant-营养 (-0.87)–(-0.92)) 并且相对于玉米 (Δ26Mg 叶绿素-植物 0.55-0.52)，叶绿素-a 中重同位素的偏好不那么明显）。观察到的效果可能归因于以三磷酸腺苷 (ATP) 形式产生的整体更高的能量，与 C3 相比，C4 中的碳固定是必需的，这可以降低动力学障碍并使平衡分馏在镁掺入原卟啉环期间占主导地位。