Morphological comparison of short saddle phytoliths of Eragrostoideae and Phragmites australis

Phytoliths are an emerging vegetation, environment, and climate proxy used in paleoecology and archaeology. The accuracy of phytoliths as paleo-vegetation and paleo-climate indicators relies heavily on the detailed research on phytoliths extracted from modern plants. For example, Eragrostoideae and Phragmites australis can produce short saddle phytoliths that are similar in shape and size, however, few detailed morphological comparative studies have been conducted on phytoliths. In this study, we described the morphology of short saddle phytoliths produced by stems, leaves, and flower spikes of five species of Eragrostoideae and P. australis. We then measured the lengths and widths of these shorth saddle phytoliths from different parts of the plant. The results showed that most of the short saddle phytoliths were similar in morphology, except for those from the flower spikes of Eragrostis minor, without concave edges. Further detailed differentiation of morphological parameters showed that the average length of the bottom (A) of short saddle phytoliths in the stems and leaves of Eragrostoideae was (11.9 ± 2.3) μm, the average length of saddle (B) was (8.1 ± 1.9) μm, and body width (C) was (12.2 ± 2.7) μm. The average length of the bottom (A) of short saddle phytoliths in the stems and leaves of P. australis was (11.9 ± 2.2) μm, the average length of saddle (B) was (7.9 ± 1.1) μm, and body width (C) was (11.2 ± 1.6) μm. Morphometric data of short saddle phytoliths of the stems and leaves of Eragrostoideae and P. australis overlapped, and no statistically significant difference existed between them. However, the average length of the bottom (A) of short saddle phytoliths in the flower spikes of E. minor was (8.3 ± 1.0) μm, the average length of saddle (B) was (5.3 ± 1.0) μm, and the average body width (C) was (6.3 ± 1.0) μm, which was much smaller than that of P. australis. Species with these types of short saddle phytoliths were classified into Eragrostoideae. The aim of this study was to explore the differences in short saddle phytoliths from the two subfamilies and to improve their identification in strata or sediments. In addition, this study provides specific references for reconstructing the paleo-vegetation and paleoenvironment of phytoliths.