Table 2.
Physiological parameters [net CO2 assimilation rate (ACO2); stomatal resistance (rs); transpiration rate (E); intrinsic Water Use Efficiency (WUEi)] of lettuce grown hydroponically in a Fitotron open-gas-exchange growth chamber in relation to light conditions and cultivar.
| Source of variance | ACO2
(μmol CO2 m−2 s−1) |
rs
(m2 s1 mol−1) |
E (mol H2O m−2 s−1) |
WUEi (μmol CO2 mol−1 H2O) |
|---|---|---|---|---|
| Cultivar (C) | ||||
| Baby Romaine | 10.49 ± 0.45 a | 5.00 ± 0.41 cd | 2.60 ± 0.13 ab | 4.08 ± 0.11 b |
| Green Salanova | 7.85 ± 0.49 c | 5.15 ± 0.51 cd | 2.67 ± 0.13 ab | 2.93 ± 0.12 d |
| Lollo rossa | 5.99 ± 0.56 d | 5.92 ± 0.62 b | 2.51 ± 0.15 b | 2.36 ± 0.16 e |
| Lollo verde | 4.06 ± 0.43 e | 5.72 ± 0.93 bc | 2.26 ± 0.16 c | 1.75 ± 0.13 f |
| Red oak leaf | 9.55 ± 0.59 b | 8.03 ± 0.57 a | 2.21 ± 0.16 c | 4.40 ± 0.15 a |
| Red Salanova | 10.07 ± 0.80 a | 4.94 ± 0.65 d | 2.76 ± 0.16 a | 3.58 ± 0.11 c |
| Light intensity (μmol m−2 s−1) (L) | ||||
| 420 (Optimal) | 9.99 ± 0.37 a | 3.70 ± 0.21 b | 2.98 ± 0.06 a | 3.39 ± 0.13 a |
| 210 (Low) | 5.76 ± 0.32 b | 8.15 ± 0.26 a | 1.97 ± 0.05 b | 2.96 ± 0.17 b |
| C × L | ||||
| Baby Romaine × Optimal | 12.06 ± 0.30 b | 3.64 ± 0.23 de | 3.03 ± 0.12 | 4.03 ± 0.17 ab |
| Green Salanova × Optimal | 9.57 ± 0.32 c | 3.36 ± 0.29 def | 3.05 ± 0.15 | 3.19 ± 0.17 c |
| Lollo rossa × Optimal | 8.01 ± 0.24 e | 4.08 ± 0.30 d | 2.93 ± 0.14 | 2.79 ± 0.16 cd |
| Lollo verde × Optimal | 5.59 ± 0.15 g | 2.33 ± 0.15 f | 2.79 ± 0.13 | 2.03 ± 0.11 e |
| Red oak leaf × Optimal | 11.68 ± 0.27 b | 6.24 ± 0.44 c | 2.73 ± 0.15 | 4.38 ± 0.24 ab |
| Red Salanova x Optimal | 13.01 ± 0.31 a | 2.53 ± 0.14 ef | 3.35 ± 0.05 | 3.90 ± 0.12 b |
| Baby Romaine × Low | 8.72 ± 0.08 d | 6.53 ± 0.35 c | 2.12 ± 0.08 | 4.14 ± 0.14 ab |
| Green Salanova × Low | 5.91 ± 0.12 g | 7.16 ± 0.25 bc | 2.25 ± 0.05 | 2.64 ± 0.10 d |
| Lollo rossa × Low | 3.71 ± 0.23 h | 7.99 ± 0.76 b | 2.05 ± 0.14 | 1.89 ± 0.19 ef |
| Lollo verde × Low | 2.33 ± 0.27 i | 9.53 ± 0.51 a | 1.66 ± 0.07 | 1.43 ± 0.19 f |
| Red oak leaf × Low | 7.16 ± 0.21 f | 10.05 ± 0.50 a | 1.63 ± 0.07 | 4.42 ± 0.18 a |
| Red Salanova × Low | 6.76 ± 0.21 f | 7.65 ± 0.22 b | 2.09 ± 0.01 | 3.23 ± 0.11 c |
| Significance | ||||
| C | *** | *** | *** | *** |
| L | *** | *** | *** | *** |
| C × L | *** | *** | ns | ** |
NS, **, *** Non-significant or significant at P ≤ 0.05, 0.01, and 0.001, respectively. Different letters within each column indicate significant differences at P ≤ 0.05. All data are expressed as mean ± SE, n = 3.