Table 2.
Effects of exogenous spermidine and D-arg on the photosynthetic parameters of lettuce under high-temperature stress.
| Treatment | Net Photosynthetic Rate (μmol m−2s−1) |
Stomatal Conductance (mmol m−2s−1) |
Transpiration Rate (mmol m−2s−1) | Intercellular CO2 Concentration (μmol m−2s−1) |
Limiting Value of Stomata |
Water Use Efficiency |
|---|---|---|---|---|---|---|
| CK | 7.87 ± 0.20 a | 117.00 ± 9.61 ab | 3.14 ± 0.12 a | 313.67 ± 23.62 a | 0.30 ± 0.04 a | 2.21 ± 0.09 b |
| H | 5.60 ± 0.17 b | 105.00 ± 26.51 b | 3.07 ± 0.06 a | 343.33 ± 10.65 a | 0.18 ± 0.02 b | 2.53 ± 0.54 a |
| HD | 3.70 ± 0.26 c | 90.33 ± 19.92 b | 2.22 ± 0.08 a | 350.00 ± 10.02 a | 0.17 ± 0.03 b | 2.57 ± 0.60 a |
| HDS | 4.83 ± 0.19 bc | 119.67 ± 27.72 a | 3.20 ± 0.07 a | 303.33 ± 12.81 a | 0.30 ± 0.01 a | 2.75 ± 0.57 a |
Data are shown as the mean, n = 3. Values in each column followed by the different letters show significant differences (p < 0.05). CK, 22 °C/17 °C, deionized water; H, 35 °C/30 °C, deionized water; HD, 35 °C/30 °C, 1 mM D-arg; HDS, 1 mM D-arg+ 1 mM Spd.