Root anatomy of five South American taxa of Saccharum L. (Poaceae): Taxonomic and ecological implications

Most anatomical studies on Saccharum have focused on the above-ground part of the species S. officinarum L. Thus, relatively little is known about the anatomy of South American Saccharum species. The purpose of this study was to describe the root anatomy of the native species S. angustifolium (Nees) Trin., S. asperum (Nees) Steud and S. villosum Steud, in addition to Saccharum aff. villosum 1 and Saccharum aff. villosum 2, and discuss the taxonomic and ecological relevance of our findings. Cross-sections of the roots were evaluated qualitatively with cluster analysis and quantitatively with ANOVA and the Tukey test at the 5% level of significance. The distinctive traits observed (25 qualitative characters and 10 quantitative characters) allowed to identify the species taxonomically and segregate them into three functional groups according to soil type: dry (S. angustifolium), moist (Saccharum aff. villosum 1) and waterlogged (remaining 3 species), shedding new light on aspects of ecological relevance. The anatomical traits observed in the study were found to have significant taxonomic value, especially branched root hairs, endodermal cells with a central projection and multi-layered pericycle, all of which are novel characteristics in the genus. Also ecologically relevant was the finding that different species growing under similar soil conditions displayed similar adaptive strategies. Thus, in this study we report the occurrence of two cryptic species of the Saccharum villosum complex (Saccharum sp. nov. 1 and Saccharum sp. nov. 2).