Morphometric distinction between ACUTE BULBOSUS (silicified epidermal hair cells) from Panicum miliaceum and Setaria italica leaves

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• June 7, 2024
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The taxomonic differentiation of broomcorn millet (Panicum miliaceum) and foxtail millet (Setaria italica) is of high relevance for archaeology and archaeobotany. The analysis of phytoliths from P. miliaceum and S. italica heavily relies on the morphology of those produced by inflorescence bracts, while other plant parts remain less explored. This study offers a meticulous examination of a distinctive variety of millet leaf phytoliths, termed as “ACUTE BULBOSUS”. It carries out a comparative analysis between ACUTE BULBOSUS sourced from contemporary S. italica and P. miliaceum leaves. To support the robustness of our findings, a case study was conducted using burnt clay daubs retrieved from the Shuanghuaishu site (5290–4527 cal BP, Central China), which display evident millet impressions.

Fig. 1 Morphometric measurement method employed for the analysis of ACUTE BULBOSUS which are categorized into two types: Type a, characterized by a single protrusion, and Type b, featuring double protrusions.

This project encompassed a quantitative analysis of the morphology of ACUTE BULBOSUS sourced from contemporary P. miliaceum and S. italica leaves. Several discriminant criteria, including density, number of protrusion, width, length and protrusion length, were proposed to differentiate between the two species. This study substantiates the potential for morphometric differentiation of ACUTE BULBOSUS from P. miliaceum and S. italica leaves. The examination of archaeological burnt clay daubs in the case study yields results that are consistent with parallel investigations focusing on diagnostic phytoliths from millet husks and ethnographic observations. Our findings confirm the feasibility of distinguishing ACUTE BULBOSUS originating from P. miliaceum and S. italica leaves, relying on distinctive size and shape criteria as well as variance in density. This pioneering classification approach introduces the possibility for detecting and identifying these taxa within archaeological contexts.

Fig. 2 Protuberance ratio of ACUTE BULBOSUS from S. italica and P. miliaceum leaves under study

Fig. 3 a, Scatter plot of length and width of the ACUTE BULBOSUS from archaeological samples and contemporary S. italica and P. miliaceum leaves; b, Scatter plot of the protrusion length and length of the ACUTE BULBOSUS from archaeological samples and contemporary S. italica and P. miliaceum leaves

Fig. 4 The two burnt clay daubs with millet impressions investigated in the current study (left). a, Fragment of burnt clay daub labelled as 2020HGSIT3448H1045, sourced from an ashpit and typologically dated to the transitional period from late Yangshao to Longshan period; b, Fragment of burnt clay daub labelled as 2020HGSIT1453, originating from Level 4 and typologically dated to the transitional period from the late Yangshao to Longshan period; c-g, Microscopic photographs depicting millet impressions from fragment of burnt clay daub labelled as 2020HGSIT3448H1045; h, SEM image showing a silicone cast made from a P. miliaceum grain impression from fragment of burnt clay daub labelled as 2020HGSIT1453; i, MicroCT visualisation of a S. italica grain from fragment of burnt clay daub labelled as 2020HGSIT1453. Protuberance ratio of ACUTE BULBOSUS from Shuanghuaishu samples (right)

Ting An
School of Art and Archaeology Zhejiang University
Hangzhou 310000 China

How to cite: An, T., Chen, J., Zheng, Y. et al. Morphometric distinction between ACUTE BULBOSUS phytoliths (silicified epidermal hair cells) from Panicum miliaceum and Setaria italica leaves. Veget Hist Archaeobot (2024). https://doi.org/10.1007/s00334-024-00999-5