Effects of eCO2 on plant growth and pollen chemistry in 14 angiosperms

Elevated atmospheric carbon dioxide (eCO2) can affect plant growth and
physiology, which can, in turn, impact herbivorous insects, including by
altering pollen or plant tissue nutrition. Previous research suggests that
eCO2can reduce pollen nutrition in some species, but it is unknown whether
this effect is consistent across flowering plant species. We
experimentally quantified the effects of eCO2 across multiple flowering
plant species on plant growth in 9 species and pollen chemistry (%N an
estimate for protein content and nutrition in 12 species; secondary
chemistry in 5 species) in greenhouses. For pollen nutrition, only
buckwheat significantly responded to eCO2, with %N increasing in eCO2; CO2
treatment did not affect pollen amino acid composition but altered
secondary metabolites in buckwheat and sunflower. Plant growth under eCO2
exhibited two trends across species: plant height was taller in 44% of
species and flower number was affected for 63% of species (3 species with
fewer and 2 species with more flowers). The remaining growth metrics (leaf
number, above-ground biomass, flower size, and flowering initiation)
showed divergent, species-specific responses, if any. Our results indicate
that future eCO2 is unlikely to uniformly change pollen chemistry or plant
growth across flowering species but may have the potential to alter
ecological interactions, or have particularly important effects on
specialized pollinators.