Stem labeling results in different patterns of 14C rhizorespiration and 15N distribution in plants compared to natural assimilation pathways |
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| Authors: | Florian Wichern Darima Andreeva Rainer Georg Joergensen Yakov Kuzyakov |
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| Institution: | 1. Department of Life Sciences, Rhine‐Waal University of Applied Sciences, 47533 Kleve, Germany;2. Department of Agroecosystem Research, University of Bayreuth, 95440 Bayreuth, Germany;3. Institute of General and Experimental Biology of the Siberian Branch of the Russian Academy of Sciences, 670047, Ulan‐Ude, Russia;4. Department of Soil Biology and Plant Nutrition, University of Kassel, Nordbahnhofstra?e 1a, 37213 Witzenhausen, Germany |
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| Abstract: | To investigate C and N rhizodeposition, plants can be 13C‐15N double‐labeled with glucose and urea using a stem‐feeding method (wick method). However, it is unclear how the 13C applied as glucose is released into the soil as rhizorespiration in comparison with the 13C applied as CO2 using a natural uptake pathway. In the present study, we therefore compared the short‐term fate of 14C and 15N in white lupine and pea plants applied either by the wick method or the natural pathways of C and N assimilation. Plants were pulse‐labeled in 14CO2‐enriched atmosphere and 15N urea was applied to the roots (atmosphere–soil) following the natural assimilation pathways, or plants were simultaneously labeled with 14C and 15N by applying a 14C glucose–15N urea solution into the stem using the wick method. Plant development, soil microbial biomass, total rhizorespiration, and distribution of N in plants were not affected by the labeling method used but by plant species. However, the 15N : N ratio in plant parts was significantly (p < 0.05) affected by the labeling method, indicating more homogeneous 15N enrichment of plants labeled via root uptake. After 14CO2 atmosphere labeling of plants, the cumulated 14CO2 release from roots and soil showed the common saturation dynamics. In contrast, after 14C‐glucose labeling by the wick method, the cumulated 14CO2 release increased linearly. These results show that 14C applied as glucose using the wick method is not rapidly transferred to the roots as compared to a short‐term 14CO2 pulse. This is partly due to a slower 14C uptake and partly due to slow distribution within the plant. Consequently, 14C‐glucose application by the wick method is no pulse‐labeling approach. However, the advantages of the wick method for 13C‐15N double labeling for estimating rhizodeposition especially under field conditions requires further methodological research. |
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| Keywords: | 14C belowground carbon belowground nitrogen double‐labeling technique 15N pulse labeling stem‐feeding method |
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