Bigger genomes provide environment-dependent growth benefits in grasses

Increasing genome size (GS) is associated with slower rates of DNA
replication and greater cellular nitrogen and phosphorus demands.
Nevertheless, plant species vary enormously in GS. Using data on grass
species’ climatic niches and growth rates under different environmental
conditions, we tested for growth costs or benefits associated with GS. We
found that evolutionary history, photosynthetic pathway and life-history
all influence the distribution of grass species’ GS. GS was constrained in
annual and C4 species, the latter allowing for small cells necessary for
C4 leaf anatomy. We found that larger GS were advantageous under high
nitrogen availability and, for perennial species, low growth-season
temperature. Increased GS benefits are likely due to associated larger
cell sizes, allowing rapid biomass production where soil fertility meets
nitrogen demands or when growth occurs via temperature-independent cell
expansion. Our findings reveal that GS is a globally important predictor
of grass performance dependent on environmental conditions.