A triplet frequency dictionary is stipulated to be a structure of non-coding DNA fragments of chloroplast genomes. We retrieved the ensembles of the non-coding regions from 391 terrestrial plants and studied the distribution of the fragments in the Euclidean metric space. An interplay between the cluster composition of the set of the dictionaries and the taxonomy of the genome bearers was analyzed.

We studied the statistical properties of non-coding regions of chloroplast genomes of 391 plants. To do that, each non-coding region has been tiled with a set of overlapping fragments of the same length, and those fragments were transformed into triplet frequency dictionaries. The dictionaries were clustered in 64-dimensional Euclidean space. Five types of the distributions were identified: ball, ball with tail, ball with two tails, lens with tail, and lens with two tails. Besides, the multigenome distribution has been studied: there are ten species performing an isolated and distant cluster; surprisingly, there is no immediate and simple relation in taxonomy composition of these clusters.