Anatomy of leaf blade, leaf sheath and pseudopetiole in Neotropical Bambusoideae (Poaceae): Insights into structure and taxonomic contributions

Anatomical investigations aiming to seek alternative characters for the taxonomy of bamboos are almost exclusively restricted to the leaf blade. Little is known about the anatomical structure of other parts of the leaf, such as the leaf sheath and pseudopetiole. The present paper analyzed the complete structure of foliage leaves, including the foliage leaf blade, foliage leaf sheath, and pseudopetiole of species belonging to the tribes Bambuseae (subtribes Guaduinae, Chusqueinae and Arthrostylidiinae) and Olyreae (subtribe Parianinae) to identify useful characters in the taxonomy of bamboos. We used scanning electron microscopy and light microscopy to describe micromorphological and anatomical features. All species sampled share the following features: foliage leaf blades with uniseriate epidermis; adaxial bulliform cells; mesophyll with arm cells, cavities, and collateral vascular bundles. Intercostal sclerenchyma associated to bulliform cells was observed only in Arthrostylidiinae. Micromorphologically, the shape and distribution of silica bodies, presence, type, and distribution of papillae on the long cells and subsidiary cells, and the presence and distribution of trichomes may be taxonomically informative in different taxonomic levels. We highlight the absence of papillae on the surfaces of foliage leaf blade of Guaduinae since the presence of papillae is considered a putative diagnosis feature supporting the sister relationship of this subtribe with Arthrostylidiinae. We describe the anatomical structure of foliage leaf sheath for the first time for Guaduinae, Chusqueinae and Parianinae. In Guaduinae, we found a unique distribution pattern of silica cells on the abaxial surface of the leaf sheath. Anatomical data about the pseudopetiole structure also were described for the first time in bamboos species; the arrangement of vascular bundles may be taxonomically informative, especially in Guaduinae.