Fig. 2.

The CO₂ gas exchange of 3-week-old hybrids compared with parents. The plants were sown on MS solid medium before being transferred into soil at 10 d old. Plants were grown under a light cycle of 16 h/8 h, in a light intensity of 120 µmol photons m⁻²s⁻¹, at 21 °C. (A) The net CO₂ assimilation rate of the hybrids and parents was measured under an increasing partial pressure of atmospheric CO₂ under a saturating irradiance at 1000 µmol m⁻² s⁻¹ using a gas exchange analyser (LI-6400XT, LICOR). The x-axis shows the intercellular CO₂ partial pressure. The analyses were carried out on the largest leaf on the rosette of each plant measured. Each data point represents the average and SE of n≥3. (B) Comparison of the maximum rate of Rubisco carboxylation (V_cmax) between hybrids and the parents. The curve fitting result using the dataset from (A). The curve fitting was carried out by fitting the dataset from (A) to the C₃ photosynthesis model (Farquhar et al., 1980). Each data point represents the average and SE of n=3. Different letters above the columns represent a significant difference between the parents (ANOVA, P<0.05). Asterisks represent significant differences between the hybrid and the better parent (ANOVA, P<0.05). No significant differences were found between hybrids and the lower parents, and between the hybrids and the growth under the average value of the parents (indicated by red dashed lines; ANOVA, P>0.05).