Bicarbonate as tracer for assimilated C and homogeneity of ¹⁴C and ¹⁵N distribution in plants by alternative labeling approaches

• Published in: Plant and soil 2013-10, Vol.371 (1/2), p.191-198
• Main Authors: Rasmussen, Jim, Kusliene, Gedrime, Jacobsen, Ole Stig, Kuzyakov, Yakov, Eriksen, Jörgen
• Format: Article
• Language: English
• Subjects: Agricultural soils; Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Atoms; Bicarbonates; Biological and medical sciences; Biomedical and Life Sciences; Clover; Ecology; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Imaging; Leaves; Life Sciences; Plant anatomy; Plant Physiology; Plant roots; Plant Sciences; Plants; Radiocarbon; Regular Article; Soil Science & Conservation; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-013-1660-x

Aims Application of carbon (C) and nitrogen (N) isotopes is an essential tool to study C and Í flows in plant-soil-microorganisms systems. When targeting single plants in a community the tracers need to be added via e.g., leaf-labeling or stem-feeding approaches. In this study we: (i) investigated if bicarbonate can be used to introduce ¹⁴C (or ¹³C) into white clover and ryegrass, and (ii) compared the patterns of ¹⁴C and ¹⁵N allocation in white clover and ryegrass to evaluate the homogeneity of tracer distribution after two alternative labeling approaches. Methods Perennial ryegrass and white clover were pulse labeled with ¹⁵N urea via leaf-labeling and ¹⁴C either via a ¹⁴CO₂ atm or with ¹⁴C bicarbonate through leaflabeling. Plants were sampled 4 days after labeling and prepared for bulk isotope analysis and for ¹⁴C imaging to identify plant parts with high and low ¹⁴C activity. Subsequently, plant parts with high and low ¹⁴C activity were separated and analyzed for ¹⁵N enrichment. Results Bicarbonate applied by leaf-labeling efficiently introduced ¹⁴C into both white clover and ryegrass, although the ¹⁴C activity in particular for white clover was found predominantly in the labeled leaf. Using ¹⁴C imaging for identification of areas with high (hotspots) and low ¹⁴C activity showed that ¹⁴C was incorporated very heterogeneously both when using bicarbonate and CO₂ as expected when using pulse labeling. Subsequent analysis of ¹⁵N enrichment in plant parts with high and low ¹⁴C activity showed that ¹⁵N also had a heterogeneous distribution (up to two orders of magnitude). Conclusion Bicarbonate can efficiently be used to introduce ¹⁴C or ¹³C into plant via the leaf-labeling method. Both ¹⁴C and ¹⁵N showed heterogeneous distribution in the plant, although the distribution of ¹⁵N was more even than that of ¹⁴C.