Direct uptake of organically derived carbon by grass roots and allocation in leaves and phytoliths: 13C labeling evidence
Direct uptake of organically derived carbon by grass roots and allocation in leaves and phytoliths: 13C labeling evidence
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DOI：
10.5194/bg-13-1693-2016
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发表时间：
2016-03-18
期刊：
影响因子：
4.9
通讯作者：
Santos, Guaciara M.
中科院分区：
文献类型：
--
作者：
Alexandre, Anne;Balesdent, Jerome;Santos, Guaciara M.
在根际环境中，植物根系对低分子量碳（C）和氮（N）的吸收已被充分记录。虽然有机氮吸收相对于总吸收很重要，但有机碳吸收相对于植物的碳预算应该较低。最近，放射性碳分析表明，土壤中的一小部分C被无定形二氧化硅微粒（沉淀在植物细胞中的植硅体）所吸收。在这里，我们调查是否以及在何种程度上有机来源的C吸收的基层可以养活的C闭塞植硅体。为此，我们添加C-13-和N-15-标记的氨基酸（AAs）的富硅溶液高羊茅。该实验旨在防止C从标记的营养液泄漏到腔室大气中。生长14天后，相对于未添加标记的AA的对照实验，测量根、茎和叶以及植硅体中的C-13和N-15富集（C-13过量和N-15过量）。此外，C-13过量的测量在分子水平上，从根和茎和叶中提取的AA。标记的AA衍生的C-13的净摄取达到总AA C-13供应的4.5%。固定在植物中的AA-衍生的C-13的量很少，但不是零（分别为根和茎/叶中总C的0.28%和0.10%）。苯丙氨酸和甲硫氨酸，提供了大量的营养液更C-13富集比其他氨基酸在植物中。这有力地表明，部分AA衍生的C-13被吸收并以其原始AA形式转运到植物中。在植硅体中，检测到AA衍生的C-13。其浓度与茎和叶中的浓度处于同一数量级（植硅体C的0.15%）。这一发现进一步证实了植硅体中的部分有机化合物可以被通过根部进入植物的碳所吸收。虽然这个实验是在营养液中进行的，因此它与土壤C吸收评估的相关性有限，但我们讨论了AA衍生的C-13在植物中吸收和转移并最终固定在植硅体中的可能形式，以及我们的结果对我们理解土壤-植物-大气界面C循环的影响
In the rhizosphere, the uptake of low-molecular-weight carbon (C) and nitrogen (N) by plant roots has been well documented. While organic N uptake relative to total uptake is important, organic C uptake is supposed to be low relative to the plant's C budget. Recently, radiocarbon analyses demonstrated that a fraction of C from the soil was occluded in amorphous silica micrometric particles that precipitate in plant cells (phytoliths). Here, we investigated whether and to what extent organically derived C absorbed by grass roots can feed the C occluded in phytoliths. For this purpose we added C-13- and N-15-labeled amino acids (AAs) to the silicon-rich hydroponic solution of the grass Festuca arundinacea. The experiment was designed to prevent C leakage from the labeled nutritive solution to the chamber atmosphere. After 14 days of growth, the C-13 and N-15 enrichments (C-13 excess and N-15 excess) in the roots, stems and leaves as well as phytoliths were measured relative to a control experiment in which no labeled AAs were added. Additionally, the C-13 excess was measured at the molecular level, in AAs extracted from roots and stems and leaves. The net uptake of labeled AA-derived C-13 reached 4.5 % of the total AA C-13 supply. The amount of AA-derived C-13 fixed in the plant was minor but not nil (0.28 and 0.10 % of total C in roots and stems/leaves, respectively). Phenylalanine and methionine that were supplied in high amounts to the nutritive solution were more C-13-enriched than other AAs in the plant. This strongly suggested that part of AA-derived C-13 was absorbed and translocated into the plant in its original AA form. In phytoliths, AA-derived C-13 was detected. Its concentration was on the same order of magnitude as in bulk stems and leaves (0.15 % of the phytolith C). This finding strengthens the body of evidences showing that part of organic compounds occluded in phytoliths can be fed by C entering the plant through the roots. Although this experiment was done in nutrient solution and its relevance for soil C uptake assessment is therefore limited, we discuss plausible forms of AA-derived C-13 absorbed and translocated in the plant and eventually fixed in phytoliths, and implications of our results for our understanding of the C cycle at the soil-plant-atmosphere interface