Figure 3.

Expression of genes involved in cytokinin biosynthesis in shoots and roots upon exposure to high CO₂. Transcript levels of AtIPT1, AtIPT3, AtIPT4, AtIPT5, AtIPT6, AtIPT7, AtIPT8, CYP735A1, and CYP735A2 were analysed in shoots (a) and roots (b) of Col-0 seedlings by quantitative RT-PCR. Expression levels of AtIPT4, AtIPT6, and AtIPT8 were below the detection limit in shoots and roots. Expression levels were normalized using At4g34270 as an internal control. Twelve-day-old seedlings grown on 1/2 MS agar plates at 280 ppmv were exposed to 280 ppmv (280) or 780 ppmv (780) CO₂ for the indicated periods. Error bars represent standard deviations of three biological replicates. Asterisks indicate statistically significant differences between 280 ppmv CO₂- and 780 ppmv CO₂-treated samples at the same exposure time (**p < 0.01; *p < 0.05; Student’s t-test).