Carbon starvation is induced by both low CO₂ concentration and low light intensity.

(A) Net CO2 assimilation of A. thaliana plants at 100 ppm CO2 and 20 μE light intensity, respectively. (B) Correlation in log2 changes in metabolite concentrations between plants shifted to either low light or to low CO2 concentrations. (C) Reduction of the glucose concentration in response to both low light- and low CO2-shift. (D) Log2 changes of selected amino acids 24 h after the shifts. Data are the mean of three (light-shift) or five (CO2-shift) biological replicates ± SD. The whole data set is given in S1 File.