Phytolith Characteristics in Leaves and Culm Sheaths of Three Sympodial Bamboo Genera (Bambusoideae) in the Xishuangbanna Tropical Botanical Garden, China

This study focused on the phytolith characteristics of leaves and culm sheaths from nine bamboo species across three genera (Bambusa Schreb., Gigantochloa Nees, and Dendrocalamus Kurz ex Munro) in the Xishuangbanna Tropical Botanical Garden. By analyzing phytolith content, concentration, particle size distribution, morphometric parameters of elongated saddle-type phytoliths, and phytolith–assemblage composition, we aimed to elucidate the distribution patterns and morphological features of phytoliths in clumping bamboos, thereby providing morphological evidence for genus-level classification within the Bambusoideae. The results demonstrated the following. (1) Leaves exhibited significantly higher phytolith content and concentration than did culm sheaths across all genera, with Dendrocalamus being the sole exception, showing no significant intrageneric differences. (2) Distinct particle size distribution patterns were observed—leaves consistently peaked at 10–20 μm, whereas culm sheaths displayed triple peaks at 10–20 μm, 20–30 μm, and 900–1000 μm. (3) Morphometric analysis revealed that culm sheaths contained larger elongated saddle-type phytoliths (length, width, and area) compared to leaves across all genera. (4) Among the 37 identified phytolith morphotypes, culm sheaths exhibited greater diversity, with 35 types (dominated by rondel and elongate), while leaves contained 31 types primarily characterized by saddle and stomatal phytoliths, with elongated saddles being the most abundant. Collectively, our findings demonstrate significant morphological disparities between foliar and culm sheath phytoliths in sympodial bamboos (Bambusa), with culm sheath phytoliths exhibiting greater taxonomic potential for generic-level classification within the subfamily Bambusoideae.