Percentage frequency of rDNA sites along chromosomes of angiosperms (a) and gymnosperms (b). Total number of sites: 3.287 in a and 679 in b. In b, the only eleven karyotypes with single sites, were represented together with multiples sites. To stress that some distributions are particular for some gymnosperm families, they were shown distinctly (cen, centromeric region; p, proximal; ip, interstitial-proximal; it, interstitial-terminal; t, terminal; wa, whole arm sites).
Roa and Guerra BMC Evolutionary Biology 2012 12:225 doi:10.1186/1471-2148-12-225