|  | CO2 exchange (g vine−1 day−1) | Water use (L vine− 1 day− 1) | WUE (g C02 L− 1 H2O) | ||||
---|---|---|---|---|---|---|---|---|
 | Average [CO2] | Day | Night | Net | Day | Night | Total |  |
10 day treatment period | ||||||||
 Ambient | 412 ppm | 69.0 | −3.8 | 65.2 | 9.0 | 0.53 | 9.5 | 7.1 |
 Sub-ambient | 235 ppm | 33.2 | −3.1 | 30.0 | 10.1 | 0.48 | 10.5 | 3.0 |
 Change |  | −52% | − 20% | −54% | + 12% | − 11% | + 11% | −58% |
4 day treatment period | ||||||||
 Ambient | 408 ppm | 77.4 | −3.0 | 74.4 | 9.0 | 0.50 | 9.5 | 7.9 |
 Sub-ambient | 408 ppm | 76.6 | −2.6 | 74.0 | 8.9 | 0.55 | 9.5 | 7.9 |
 10 days | Treatment | 0.003 | 0.100 | 0.005 | ns | 0.086 | ns | 0.002 |
 | Day | < 0.001 | 0.012 | < 0.001 | < 0.001 | < 0.001 | < 0.001 | < 0.001 |
 | Treatment x Day | 0.008 | ns | 0.007 | ns | 0.023 | ns | < 0.001 |
 4 days | Treatment | Ns | ns | ns | ns | ns | ns | ns |