The genome size of an organism is determined by its capacity to tolerate genome expansion. Veselý et al. study 47 pairs of geophytic taxa and their closest non-geophytic relatives across the whole angiosperms. They find increased genome sizes in geophytes compared to their non-geophytic relatives, regardless of the storage organ type and regardless of whether or not vernal geophytes, polyploids or annuals are included in the analyses. The tendency of geophytes to possess higher genome size suggests the presence of a universal mechanism allowing for genome expansion. It is assumed that this is primarily due to the nutrient and energetic independence of geophytes perhaps allowing continuous synthesis of DNA, which is known to proceed in extreme cases of vernal geophytes even in dormant stages.
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.