Computed tomography has revolutionized scientific visualization by enabling the study of biological structures without the need to physically section them. In the case of pollen grains, this technique reveals details of their external and internal morphology with micrometric resolution. Unlike scanning electron microscopy, which only captures the surface, tomography generates three-dimensional volumetric models that can be rotated and analyzed from any angle.
Volumetric reconstruction and data processing 🔬
The process begins with the acquisition of hundreds of radiographic projections of the pollen grain as it rotates on its axis. A filtered back-projection algorithm reconstructs a 3D volume from these images. Each voxel contains density information, allowing differentiation of the exine (resistant outer layer) from the intine (cellulosic inner layer) and the cytoplasm. Tools such as ImageJ or Avizo allow these layers to be segmented and polygon meshes to be generated for export to rendering software. Precision reaches 0.5 micrometers, sufficient to observe pores, colpi, and species-specific ornamentations.
Implications for science and visual art 🌿
Beyond pure botany, these models have direct applications in paleoclimatology, where fossilized pollen in sediments helps reconstruct ancient ecosystems. In allergology, precise identification of allergenic species improves diagnoses. Visually, the fractal geometry and textures of pollen grains offer a fascinating field for scientific illustration and outreach. Compared to traditional optical microscopy, tomography eliminates optical distortions and allows measurement of real volumes, not just projected areas.
What was the main technical challenge in reconstructing the three-dimensional images of pollen grains from the computed tomography data?
(PS: modeling manta rays is easy; the hard part is making sure they don't look like floating plastic bags)