Hierarchical cluster analysis (HCA) of P. vulgaris miRNA families. Frequencies of conserved miRNA families were used to analyze relative miRNA family expression in leaf, seedling, root and flower. Hierarchical cluster analysis was performed on thirty-three conserved miRNA families (right). The color scale denotes abundant (green) and non-abundant (red) miRNA families according to transformed count data. Density plots are included in blue lines.