Knowledge of evolution of genome size in species with holocentric chromosomes is limited. Lipnerová et al. study genome size and base composition in the holocentric genus Carex (Cyperaceae) in relation to chromosome number. They find that genomes are relatively small and very GC-poor compared with other angiosperms, with genome size positively correlated with GC content and negatively correlated with chromosome number. They identify seven polyploid and two potentially polyploid species in Carex subgenus Carex, and determine that this subgenus exhibits larger genome sizes and a higher rate of genome size evolution compared to subgenus Vignea. They conclude that evolution of genomes and karyotypes in the Carex genus is promoted by frequent chromosomal fissions/fusions, rare polyploidy, and common repetitive DNA proliferation/removal.
Genome size is known to affect various plant traits such as stomatal size and seed mass but these associations are not well understood for species with very large genomes, which are largely represented by geophytic plants. Veselý et al. survey genome size across 219 geophytes and find that it is associated with species’ ecology and phenology, and analysis also shows an association with changes in DNA base composition. They suggest that although production of larger cells appears to be an advantageous strategy for fast development in seasonal habitats, the drought sensitivity of large stomata may restrict the occurrence of geophytes with very large genomes to regions not subject to water stress.