Plasticity of rice tiller production is related to genotypic variation in the biomass response to elevated atmospheric CO2 concentration and low temperatures during vegetative growth

Appropriate resource partitioning to either production of new tillers or growth of individual tillers is a critical factor for increasing rice biomass production and facilitating adaptation to climate change. We examined the contributions of genotypic variation to the tiller number and individual tiller growth of 24 rice cultivars in response to an elevated atmospheric CO2 concentration [CO2] (control + 191 μmol mol−1) and a low air temperature (control minus 4.7 °C) during 56 days of vegetative growth after transplanting. For all genotypes combined, biomass increased by 27% under elevated [CO2] and decreased by 34% at low temperature, with a significant genotype × temperature interaction. The increase caused by elevated [CO2] resulted from increased tiller number, and the decrease caused by low temperature resulted from decreased growth of individual tillers. Despite the different overall responses to elevated [CO2] and low temperature, most of the genotypic variation in biomass at elevated [CO2] and low temperature was explained by the responses of tiller number rather than by individual tiller growth. The genotypes with the highest biomass response to elevated [CO2] had a smaller reduction of biomass under low temperature. These results highlight the greater importance of genotypic variation in tiller number than in individual tiller growth in the response of biomass to environmental change.

► Rice cultivars responded differently to elevated [CO2] and low air temperature.
► Genotypic variation in biomass was explained mainly by changes in tiller number.
► Variation was explained less by the growth of individual tillers.