The effects of crwn mutations on nuclear size and nuclear DNA density in leaf cells. (A) Developmentally matched rosette leaves from approximately one month-old plants were fixed, cells isolated and stained with DAPI, and nuclei imaged using epifluorescence microscopy. The average areas of randomly-selected individual nuclei (n = 32–108) were determined for each genotype. Error bars indicated standard error of the mean. (B) Nuclear area measurements from panel A (see also, Additional file 4) were converted to relative values and were plotted against average endopolyploidy level for each genotype expressed as a fraction of the wild-type value. The average endopolyploidy levels (Additional file 4) were measured by flow cytometry using corresponding leaf samples. The diagonal dashed line indicates the expected linear relationship between nuclear area and endopolyploid level observed in wild-type plants. Note that panel A measures nuclear area but the isolated nuclei are flattened under a coverslip to a uniform thickness (see Additional file 6) and therefore nuclear area is proportional to and therefore a proxy for nuclear volume. The numbers next to the symbols indicate the corresponding crwn genotype. Data points above the dashed line indicate an elevated nuclear DNA density relative to wild type. The solid line corresponds to a nuclear DNA density four-times that of wild type.