Fig. 4: Leaves of the ethylene overproducer, eto1-1, show intact CO₂-induced stomatal conductance responses.

A. thaliana wild-type (WT, Col-0) and the eto1-1 mutant plants were grown under ambient CO₂ (400 ppm) for five-weeks and then measured for their (a) Ethylene levels using gas chromatography and (b) stomatal conductance responses to [CO₂]-shifts. (a) Potted plants were split into two groups and incubated at either low CO₂ (150 ppm) or high CO₂ (900 ppm) for 100 min. Ethylene production was then quantified using gas chromatography. Data present the mean of three independent experiments (n=8 plants in each experiment, for each line and condition). Letters indicate statistical differences between lines and treatment (P < 0.05, Two-way ANOVA). (b, c, d) Stomatal conductance of wild-type (WT, Col-0) and eto1-1 A. thaliana mutant leaves from intact plants in response to shifts in imposed [CO₂] as indicated at the bottom (ppm). (b) Shown are mean (±SEM) of n=4 leaves from individual plants per genotype. (c) Stomatal conductance (in panel b) was normalized to the stomatal conductance at 360 ppm [CO₂] before shifting to 800 ppm [CO₂]. (d) Changes in absolute stomatal conductance (mean ± SEM) were calculated at the indicated time points based on the data presented in panel b (t1=stomatal conductance at 360 ppm [CO₂], t2=10 min following exposure to 800 ppm [CO₂], t3=20 min following exposure to 800 ppm [CO₂], t4=25 min following exposure to 100 ppm [CO₂], t5=50 min following exposure to 100 ppm [CO₂]). Statistical analyses were done using unpaired Student’s t tests between the wild-type and the mutant line, P-value is presented above/under columns. Comparable findings were made in additional independent experiments, using a different [CO₂]-shift protocol, where the gas exchanged leaf was exposed to ambient, low and then high CO₂ (Fig. S3).