Anatomy and micromorphology of Imperata (Poaceae, Andropogoneae) from Brazil and their taxonomic significance.

Species delimitation in Imperata (Poaceae, Andropogoneae) is complicated by overlapping morphological variation. Here, we reassess the taxonomy of Brazilian Imperata and investigate leaf and culm anatomy together with leaf epidermal micromorphology to evaluate their taxonomic relevance. Field collections and herbarium specimens were examined using standard taxonomic procedures, light microscopy, and scanning electron microscopy. Three species were confirmed for Brazil (I. brasiliensis, I. contracta, and I. tenuis), whereas the occurrence of I. minutiflora in the country was not supported. We provide an identification key, updated descriptions, distribution maps, and illustrations of the confirmed species, as well as lectotype designations for I. contracta and I. tenuis. The most informative anatomical and micromorphological characters were found in the leaf blade, including the presence of dumbbell-shaped guard cells in I. brasiliensis, distinctive long and short epidermal cells in I. contracta, and the absence of cushion-hairs in I. tenuis. In contrast, leaf sheath and culm anatomy were comparatively more uniform. Our results support the use of comparative anatomy and micromorphology as complementary sources of evidence for the delimitation of Brazilian species of Imperata.