Stomatal complexes in Mimosa L. (Caesalpiniodeae, Leguminosae), a literature review

The study of stomatal complexes has provided characters that allow for species recognition, so this area of research is critical, mainly in families with a high concentration of genera that are problematic about the recognition and classification of their taxa. Mimosa L. belongs to one of the largest and most diverse families of angiosperms, the legumes, yet the morphological characters used are not sufficient for the delimitation and recognition of its sections, series, and species, and it is for this reason that its infrageneric classification is considered problematic. Thus, the aim of our study was to perform, based on a literature review, an analysis of the taxonomic relevance of stomatal complexes in the infrageneric classification of Mimosa. Studies on stomatal complexes in Mimosa are scarce, but the evidence suggests: (i) that the presence of paracytic complexes does not allow for the separation of sections, (ii) that, thus far, series Acanthocarpae, section Batocaulon is the only series to exhibit exclusively paracytic stomatal complexes, and (iii) that the anomocytic complex observed in M. benthamii is useful for the recognition of that taxon. Finally, the study of stomatal complexes in Mimosa opens new and different challenges to explore, not only in terms of taxonomic issues, but also with respect to physiological and ecological aspects, as this knowledge leads to the determination of the plants’ water-use efficiency and will most likely indicate their use in ecological restoration.