ORCID
- Laura Scoble: 0009-0008-4380-5841
- Simon J. Ussher: 0000-0001-6724-9212
- Mark F. Fitzsimons: 0000-0002-6443-6087
- Lauren Ansell: 0000-0003-4800-1718
- Ralph M. Fyfe: 0000-0002-5676-008X
Abstract
Single-grain pollen analysis is essential for advancing chemical palynology, which classifies morphologically similar taxa based on taxon-specific pollen and sporopollenin chemistry. Fourier-Transform Infrared (FT-IR) spectroscopy and microspectroscopy (μFT-IR) are widely used to differentiate morphologically similar grains but face limitations from Mie scattering and coarse spatial resolution. Here, we present the first application of Optical-PhotoThermal Infrared (O-PTIR) spectroscopy to chemically treated single pollen grains, using Molinia caerulea as a model taxon to fully test and evaluate the technical capabilities and limitations of this technique. O-PTIR achieves sub-micron “super-resolution” infrared spectroscopy through non-contact, non-destructive measurements by exploiting the photothermal effect. O-PTIR spectra exhibited close similarity to FT-IR datasets, with all major sporopollenin bands present and only minor peak shifts (4 cm−1). Reliable application of sub-micron spectra for classification purposes requires a robust understanding of intra- and inter-grain variability. This can now be assessed using O-PTIR to distinguish whether intra-grain surface heterogeneity or true inter-grain biochemical differences drives grain separation. Multivariate analysis of intra- and inter-grain variability indicated that greater intra-grain variability does not drive greater inter-grain variability, confirming that observed pollen grain separation reflects true biochemical differences rather than technical or surface related effects. Similarly, intra- and inter-grain variability did not differ significantly between plants, While a single O-PTIR measurement can produce a spectrum highly similar to the species centroid, averaging four measurements per grain yields reliable and representative results. This work establishes the methodological foundations necessary for future multi-taxon chemotaxonomic studies using O-PTIR.
DOI Link
Publication Date
2026-01-01
Publication Title
Review of Palaeobotany and Palynology
Volume
353
ISSN
0034-6667
Deposit Date
2026-08-24
Funding
We would like to thank Dartmoor National Park for collecting and sending samples to the University of Plymouth, and Matthew Craven and Julian Stander from the University of Plymouth for support regarding statistical analysis. Laura Scoble was supported by Funds for Women Graduates (FfWG) Foundation Grant. FfWG provide grants, bursaries and fellowships to women graduates to help with living expenses. It should be noted that this research was not funded by FfWG.
Additional Links
Keywords
Acetolysis, Chemical palynology, FT-IR, O-PTIR, Poaceae pollen, Single pollen grains, Sporopollenin
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Scoble, L., Meng, H., Ussher, S., Fitzsimons, M., Ansell, L., Kansiz, M., Simmonds, B., Stone, N., & Fyfe, R. (2026) 'Assessing the application of Optical-PhotoThermal Infrared spectroscopy for single-grain chemical palynology', Review of Palaeobotany and Palynology, 353. Available at: 10.1016/j.revpalbo.2026.105664
