Table II. The slow growth of βca2βca4 is not attributable to lower photosynthetic rates.
The CO2 compensation points were generated by finding the slope of the initial linear portion of the assimilation/inorganic carbon curve and solving for the x intercept. CO2 assimilation (A), stomatal conductance (gs), and water use efficiency (WUE) values are listed for low (200 μL L−1), ambient (400 μL L−1), and high (1,000 μL L−1) CO2. Measurements were made with a LI-COR 6400XT gas analyzer using the LI-COR 6400-40 leaf fluorescence cuvette. Values are taken from assimilation/inorganic carbon curves performed on the 16th youngest leaf of four independent 10-week-old plants from each plant line grown in 200 μL L−1 CO2.
| Parameter | Wild Type (COL) | βca2 | βca4 | βca2βca4 |
|---|---|---|---|---|
| CO2 compensation point | 55.9 ± 2.0 | 53.1 ± 1.4 | 59.9 ± 4.1 | 56.4 ± 4.1 |
| 200 μL L−1 CO2 | ||||
| A | 4.9 ± 0.32 | 5.3 ± 0.71 | 6.3 ± 0.38 | 5.3 ± 0.90 |
| gs | 0.28 ± 0.04 | 0.25 ± 0.04 | 0.37 ± 0.03 | 0.35 ± 0.04 |
| WUE | 0.16 ± 0.02 | 0.18 ± 0.01 | 0.15 ± 0.01 | 0.14 ± 0.01 |
| 400 μL L−1 CO2 | ||||
| A | 11.2 ± 1.1 | 12.1 ± 0.85 | 13.6 ± 0.6 | 11.4 ± 1.7 |
| gs | 0.32 ± 0.03 | 0.29 ± 0.04 | 0.38 ± 0.03 | 0.35 ± 0.04 |
| WUE | 0.33 ± 0.04 | 0.35 ± 0.02 | 0.33 ± 0.01 | 0.30 ± 0.02 |
| 1,000 μL L−1 CO2 | ||||
| A | 18.0 ± 2.1 | 19.7 ± 1.4 | 20.8 ± 1.1 | 18.7 ± 2.2 |
| gs | 0.29 ± 0.04 | 0.21 ± 0.04 | 0.38 ± 0.03 | 0.35 ± 0.04 |
| WUE | 0.57 ± 0.12 | 0.77 ± 0.09 | 0.51 ± 0.03 | 0.49 ± 0.02 |