Genome size and guard cell length are associated in four species of Miconia (Miconieae, Melastomataceae)

Miconia Ruiz Pav. (Melastomataceae) is the seventh largest genus of flowering plants, but despite the great diversity of species (ca. 1900), no genome size (GS) studies have been published on the group. Studies have shown that GS can strongly predict phenotypic characteristics such as guard cell length, stomatal density, and epidermal cell area. As more genome sizes become available, a more comprehensive understanding of the role that GS variation plays in cellular characteristics emerges. Here, for the first time, we estimate GS by flow cytometry in four Miconia species, Miconia australis (Cham.) R. Goldenb., Miconia hyemalis St. Hil. Naud. ex Naud., Miconia sellowiana (DC.) Naudin, and Miconia nianga (DC.) R.Goldenb.). Subsequently, we carried out a comparative analysis of the relationship between GS and three phenotypic characteristics: guard cell length, stomatal density, and epidermal cell area. The estimated GS ranged from 0.56 to 1.2 pg, and this variation may be attributed to the distinct reproductive modes among the species analyzed. We found a strong positive correlation between GS and guard cell length (r2 = 0.92) and a low correlation in stomatal density and epidermal cell area (r2 = 0.07 and 0.06, respectively). In this pioneering study, we provide some conclusions or speculations, and point to new questions yet to be explored in Miconia.