Impacts of elevated CO2 and light on growth and stoichiometry in Arabidopsis

Abstract

The effect of elevated CO₂ on plant stoichiometry has been given a lot of attention in the last years; however, extended studies on the effects of elevated light added to the increased CO₂ are still insufficient. Plant growth chambers were set up to grow Arabidopsis thaliana under ambient (~400 ppm) and elevated (~700 ppm) CO₂. The chambers made it possible to monitor and adjust CO₂ levels precisely while also tracking the light, temperature and relative humidity. Two separate experiments were run; experiment 1 with ambient (~170 µE) light and experiment 2 with increased (~350 µE) light to test the effects of elevated CO₂ and light on plants. We weighed the plants and analysed the tissues for chlorophyll, C, N and P levels to test if there was a correlation between CO₂, light and element composition. With elevated CO₂, the average dry shoot biomass was reduced in both experiments. The clearest changes were between experiments; biomass and C increased, and N, P and chlorophyll decreased with elevated light. When adding elevated CO₂, the trends were even more profound. This resulted in a substantial increase in the C:P and C:N ratios. The results largely suggest that elevated CO₂ together with the corresponding changes in climate have a clear effect on the element composition of plants. The effect of elevated CO₂ and light on plant quality (nutrient and protein content) could have negative impacts on small and large herbivores, and even humans.