A correlation analysis of Light Microscopy and X-ray MicroCT imaging methods applied to archaeological plant remains’ morphological attributes visualization

Abstract

In this work, several attributes of the internal morphology of drupaceous fruits found in the archaeological site Monte Castelo (Rondonia, Brazil) are analyzed by means of two different imaging methods. The aim is to explore similarities and differences in the visualization and analytical properties of the images obtained via High Resolution Light Microscopy and X-ray micro-computed tomography (X-ray MicroCT) methods. Both provide data about the three-layered pericarp (exo-, meso- and endocarp) of the studied exemplars, defined by cell differentiation, vascularisation, cellular contents, presence of sclerenchyma cells and secretory cavities. However, it is possible to identify a series of differences between the information that can be obtained through each of the methods. These variations are related to the definition of contours and fine details of some characteristics, their spatial distribution, size attributes, optical properties and material preservation. The results obtained from both imaging methods are complementary, contributing to a more exhaustive morphological study of the plant remains. X-ray MicroCT in phase-contrast mode represents a suitable non-destructive analytic technique when sample preservation is required.

Some Notes on Dense Structures Present in Archaeological Plant Remains: X-ray Fluorescence Computed Tomography Applications

“…Their presence extends inside the sample in some sectors of the mesocarp and endocarp contours. In the case of Ca, it is represented in the XFCT images towards both ends of the endocarp tissue, probably related to the presence of constitutive calcium oxalate biomineralization, already observed by microscopy and X-ray absorption microtomography in several uncharred specimens from Monte Castelo [4,5]. On the other hand, all these elements are notably abundant in sediments, especially Ca, suggesting that at least some of its presence in the fruit could penetrate it through the most exposed tissues, the lax cellular arrangement of the mesocarp and some broken areas.…”

“…The sample SMC_01 found in association with the sub-adult burial context was imaged twice, using the XFCT technique at the XRF Beamline of the Brazilian Synchrotron Light Laboratory (LNLS-CNPEM) (UVX source), aiming to obtain compositional and distributional information about the solid bodies and anatomical structures of the fruit. Both experiments were set to provide XFCT images of the internal structure of the sample that can be cross-checked against the X-ray MicroCT images on which the dense aggregates were initially detected [4,5].…”

“…Microtomographic images obtained from a dozen of these specimens revealed the occurrence of dense aggregates stuck into the internal tissues and cavities of the drupes. Some of them are regular small crystal bodies associated with the endocarp idioblast cells, while others were described as irregular, bigger, and apparently amorphous structures, placed between the mesocarp cells and inside some cavities in the fruit structure [4,5]. A considerable large and morphologically homogeneous assemblage of uncharred plant remains was recovered from the ceramic layers from the Bacabal Phase and the more ancient Sinimbu Phase (Figure 1C).…”

“…This article builds on some assumptions derived from previous X-ray microtomography analysis of a set of uncharred plant remains from the archaeological site Monte Castelo (Rondonia, Brazil), a fluvial shellmound in Southwestern Amazonia [1][2][3]. Tridimensional images of the internal structure of these specimens had shown the presence of solid aggregates, or concretions, whose relative density, distribution, and shape does not refer to anatomical features [4,5]. A mineral composition derived from some mechanical, biological, and/or physicochemical interaction processes involving the sedimentary materials from the site matrix was then proposed as the origin of these dense bodies.…”

“…The abundance of Ca-as well as P, Mg, K, and Mn-compounds in Monte Castelo, mostly due to the decay of high amounts of shell material, and the fluctuating water levels along the seasonal regime of the local wetlands landscape, give the general conditions for the occurrence of some mineralization processes [1,3,5]. However, these have been minimally studied so far, especially in the case of preserved uncharred plant remains.…”