State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
J Environ Sci (China). 2020 Dec;98:22-30. doi: 10.1016/j.jes.2020.05.011. Epub 2020 Jun 11.
The release of root exudates (REs) provides an important source of soil organic carbon. This work revealed the molecular composition of REs of different plant species including alfalfa (Medicago sativa L.), bean (Phaseolus vulgaris L.), barley (Hordeum vulgare L.), maize (Zea mays), wheat (Triticum aestivum L.), ryegrass (Lolium perenne L.) and pumpkin (Cucurbita maxima) using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The combination of positive ion mode (+ESI) and negative ion mode (-ESI) increased the number of the molecules detected by ESI FT-ICR MS, and a total of 8758 molecules were identified across all the samples. In detail, lipids and proteins and unsaturated hydrocarbons were more easily detected in +ESI mode, while aromatic compounds with high O/C were readily ionized in -ESI mode, and only 38% of the total assigned formulas were shared by -ESI and +ESI modes. Multivariate statistical analysis of the formulas indicated that the close related plants species secreted REs with similar molecular components. Moreover, the unsaturation degree and nitrogen content were the two key parameters able to distinguish the similarities and differences of molecular components of REs between plant species. The results provided a feasible analysis method for characterization of the molecular components of REs and for the first time characterized the molecular components of REs of a variety of plant species using ESI FT-ICR MS.
根系分泌物（REs）的释放为土壤有机碳提供了重要来源。本研究采用电喷雾电离与傅里叶变换离子回旋共振质谱（ESI FT-ICR MS）联用技术，揭示了包括紫花苜蓿（Medicago sativa L.）、菜豆（Phaseolus vulgaris L.）、大麦（Hordeum vulgare L.）、玉米（Zea mays）、小麦（Triticum aestivum L.）、黑麦草（Lolium perenne L.）和南瓜（Cucurbita maxima）在内的不同植物根系分泌物的分子组成。正离子模式（+ESI）和负离子模式（-ESI）的结合增加了 ESI FT-ICR MS 检测到的分子数量，总共鉴定出 8758 种分子。详细地说，在+ESI 模式下更容易检测到脂质、蛋白质和不饱和烃，而具有高 O/C 的芳香族化合物在-ESI 模式下更容易被离子化，而-ESI 和+ESI 模式共有的总分配公式仅占 38%。公式的多元统计分析表明，亲缘关系密切的植物物种分泌的根系分泌物具有相似的分子组成。此外，不饱和程度和氮含量是区分植物物种之间根系分泌物分子组成相似性和差异性的两个关键参数。该结果为根系分泌物分子组成的特征分析提供了一种可行的方法，并首次采用 ESI FT-ICR MS 对多种植物物种的根系分泌物分子组成进行了表征。
