DNA content of the individual chromosomes of rye

The relative DNA content of individual chromosomes of Secale cereale L. was determined in 25 cells by microdensitometry of Feulgen stained preparations. The correlation value between relative DNA content and relative chromosome length was r=0.61 for all 328 chromosomes measured. However, the correlation coefficients calculated for individual cells as well as for mean values always approached 1. Taking into account the structure of rye chromosomes, this indicates that microdensitometric results may not be accurate when large quantities of heterochromatic DNA sequences are present in analyzed material.