Nuclear DNA content of Ae. squarrosa, natural Emmer and natural and synthesized Dinkel wheats, in addition to Tetra Canthatch (AABB) which was extracted from common wheat, was measured Feulgen-microspectrophotometrically using PMC's at first prophase or pollen tetrads.
A significant amount of variation in DNA content per nucleus was observed among seven strains of Ae. squarrosa, indicating intraspecific differentiation accompanied by gain or loss of genetic material in this diploid species.
DNA content per nucleus of the extracted tetraploid (Tetra Canthatch) was the same as those of present-day natural Emmer wheat; no appreciable quantitative change in nuclear DNA of the A and B genomes of common wheat seems to have taken place during at least the past seven thousand years, in spite of considerable genetic changes that have occurred.
Two natural and six synthesized hexaploids had similar DNA content that was approximately equal to the sum of those of their parents.
Evidence concerning variation in nuclear DNA content of higher plants was reviewed and quantitative relationships between diploid and polyploid species in DNA content was discussed in relation to its evolutionary significance.